Patent Publication Number: US-7912402-B2

Title: Developing device with leakage preventing member, process cartridge with leakage preventing member, and method for attaching developing roller to developer container

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2006-030551, filed on Feb. 8, 2006, the entire subject matter of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     Aspects of the present invention relate to a developing device using developer, such as toner, an image forming device and a process cartridge. 
     BACKGROUND 
     An electrophotography-based image forming device such as a laser printer electrostatically feeds developer, such as toner, on an electrostatic latent image formed on a photosensitive member to develop a toner image. The toner image is transferred to a recording medium (for example, a sheet) to form an image. The developer is contained in a developer container (case) of a developing device and provided for development to a developing roller, such as a developing roller, rotatably supported at a predetermined position along an opening of the developer container. 
     When the developer contained in the developer container is leaked out from the developer container, the developer scatters to stain the interior of the image forming device and the recording medium. In order to prevent the leakage of developer as described above, for example, JP-A-2001-134080 discloses an image forming device including developer leakage preventing members called side seals respectively disposed at portions, where the longitudinal end portions of the developing roller oppose the developer container. The developer leakage preventing members prevent the leakage of the developer. The substrate of the side seal is made of an elastic material, such as urethane sponge. Since the developing roller is attached so as to press the side seal, the longitudinal end portions of the developing roller strongly contact with the side seals, respectively. Therefore, even when the developing roller rotates, the toner is prevented from leaking from the longitudinal end portions of the developing roller. 
     The side seal  109  (refer to  FIG. 13B ) is made of an elastic material such as urethane sponge and has a certain thickness so that when a developing roller  22  is attached to a case  21  of a developing cartridge  4 , the side seal  109  is compressed and exerts a predetermined pressing force to the developing roller  22 . When the developing roller  22  is attached to the case  21  of the developing cartridge  4 , such a method is employed that a shaft of the developing roller is inserted into a supporting hole  21   d  formed on a case side portion  21   a  of the developing cartridge  4  and the developing roller  22  is placed on a side seal  109 . 
     However, since the side seal  109  is, as described above, made of an elastic material having a certain thickness, a direction to which the side seal  109  is pressed and forcibly deformed is varied depending on how the developing roller  22  presses the side seal  109 . Specifically, a shape of the side seal  109  at the time when the developing roller  22  is attached is very difficult to control with collapse of the side seal  109  taken into account. As one example shown in  FIG. 13B , when the developing roller  22  is attached so as to press down the side seal  109  downward (in a direction apart from a blade  26 ), a large clearance  100  is formed in the vicinity of an upper end side  109   e  of the side seal  109 . Then, the developer leaks from the clearance  100  and the developer scatters inside an image forming device. 
     SUMMARY 
     An aspect of the invention provides a developing device including: a developer container that contains developer and is formed with an opening for providing the developer; a developing roller that is rotatably supported by the developer container at a predetermined position to be disposed along the opening and includes, a roller shaft, and an elastic roller that is supported by the roller shaft and is configured to carry the developer provided through the opening; leakage preventing members that are made of elastic material and prevent leakage of the developer at longitudinal end portions of the elastic roller, each of which is respectively disposed at portions where the longitudinal end portions oppose the developer container, to extend in an extending direction along a circumferential surface of the elastic roller at a longitudinal end portion thereof; and a guide that is provided on the developer container and slidably guides the developing roller toward the predetermined position along a sliding direction that is defined along the extending direction to allow the developing roller to be attached to the developer container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a brief side sectional view of a printer; 
         FIG. 2  is an upper face view of a developing cartridge; 
         FIG. 3  is a left side view of the developing cartridge; 
         FIG. 4  is a right side view of the developing cartridge; 
         FIG. 5  is a view of the developing cartridge before a blade and a developing roller are attached when viewed from a direction X of  FIG. 2 ; 
         FIG. 6A  is a view of the blade when viewed from the back thereof; 
         FIG. 6B  is a view of the blade when viewed from the front thereof; 
         FIG. 7  is a right side view of the developing cartridge before the developing roller is attached; 
         FIG. 8  is a right side view of the developing cartridge in a process of attaching the developing roller; 
         FIG. 9  is a right side view of the developing cartridge in a state that the developing roller is completely attached; 
         FIG. 11A  is a brief sectional view taken along the line of A-A of  FIG. 2 ; 
         FIG. 10B  is an enlarged view of major parts in  FIG. 10A ; 
         FIG. 11  is a view showing an exemplified variation of the configuration of a guide notch shown in  FIG. 7 ; 
         FIG. 12A  is a brief sectional view showing an exemplified variation of the developing cartridge; 
         FIG. 12B  is an enlarged view of major parts in  FIG. 12A ; 
         FIG. 13A  is a brief sectional view of a conventional developing cartridge; 
         FIG. 13B  is an enlarged view of major parts in  FIG. 13A ; 
       FIG.  14 Aisanotherbriefsectionalviewofaconventional developing cartridge for comparison with that shown in  FIGS. 13A and 13B ; and 
         FIG. 14B  is an enlarged view of major parts in  FIG. 14A . 
     
    
    
     DETAILED DESCRIPTION 
     First Example 
     Next, description will be made for a first example of a laser beam printer according to the present invention. 
     Configuration of Image Forming Device 
       FIG. 1  is a brief side-sectional view showing a printer as an image forming device. As shown in  FIG. 1 , a process cartridge  2  including a photosensitive cartridge  3  and a developing cartridge  4  is arranged inside a main housing  1  of the printer approximately at the center thereof. The process cartridge  2  is configured to be attachable to and detachable from the main housing  1  in a state where a lid lb on a right end (on a front face) of the main housing  1  in  FIG. 1  is rotated downward and opened. 
     A fixing unit  5  is arranged on a left side in  FIG. 1  adjacent to the process cartridge  2 . A sheet feeding unit  6  is arranged below the process cartridge  2  so that a sheet feeding cassette  8  is attachable from a front face (indicated by the arrow A shown in  FIG. 1 ) below the main housing  1 . Further, a laser scanner unit  7  is mounted on a frame below the lower face of a synthetic resin sheet discharging tray  1   a , which is also used as a cover. The laser scanner unit includes a laser light emitting unit, a polygon mirror  18 , a plurality of lenses  19 , a plurality of reflecting mirrors  20  and others. 
     When a print data is sent from an external device (not shown), for example, a personal computer in response to a print instruction, cut sheets P each being a recording medium stacked on a supporting plate  9  of the sheet feeding cassette  8  are separated into single sheets by a separation pad  11  as a sheet feeding roller  10  in a sheet feeding unit  6  is rotated. Then, the separated sheet is conveyed through a pair of registration rollers  12   a  and  12   b  between a photosensitive drum  13  (a photosensitive member) in the process cartridge  2  and a transfer roller  14  (a transfer unit) pressing the conveyed sheet to the lower face of the photosensitive drum  13 . On the other hand, a laser beam emitted from an emission hole at the lower face of the frame supporting the laser scanner unit  7  is irradiated on an upper face of the photosensitive drum  13  through a window opening  31  at an upper side of the process cartridge  2 . Then, the peripheral face of the photosensitive drum  13  is exposed with the light in accordance with the print data and an electrostatic latent image is formed. 
     Further, as will be described later, toner (developer) provided from a developing roller  22  on the developing cartridge  4  is fed on the electrostatic latent image to be visible. Then, a visible image by the toner on the photosensitive drum  13  is transferred to a sheet P. Thereafter, the sheet P is transferred between a heating roller  15  and a pressing roller  16  in the fixing unit  5  and subjected to be heated and fixed and then discharged from a sheet discharging path  17  to the sheet discharging tray  1   a . The sheet P is conveyed inside the image forming device along a conveying path (conveying mechanism) shown by the two-dot chain line in  FIG. 1 , and an image is formed on a surface of the sheet P by the toner provided on the photosensitive drum  13 . 
     In the first example, the process cartridge  2  includes: a photosensitive cartridge  3  having at least a photosensitive drum  13 ; and a developing cartridge  4  having at least a developing roller  22  attached to a case  21  as a developer container. The developing cartridge  4  is attachable to and detachable from the photosensitive cartridge  3 . The process cartridge  2  including the developing cartridge  4  and photosensitive cartridge  3  is attachable to and detachable from the image forming device. The developing cartridge  4  is attachable to and detachable from the image forming device separately from the photosensitive cartridge  3 . Although the developing device according to the first example is configured to be attachable to and detachable from the image forming device as described above, the present invention may be applicable to a developing device that is fixed inside an image forming device. 
     A photosensitive drum  13  is rotatably supported so as to rotate at one side of a synthetic resin case of the photosensitive cartridge  3 . The photosensitive drum  13  includes an organic photosensitive agent mainly composed of positively charged materials such as positively charged polycarbonate. The photosensitive drum  13  has a hollow cylindrical shape with a hollow. Specifically the photosensitive drum  13  includes an aluminum cylindrical sleeve as a body and a photoconductive layer with a predetermined thickness (for example, 20 μm), which includes a photoconductive resin dispersed with polycarbonate and is formed around the body. The photosensitive drum  13  is rotatably supported while the cylindrical sleeve is kept grounded. The photosensitive drum  13  is rotated and driven by a driving unit (not shown) in a direction shown by an arrow in  FIG. 1 . The transfer roller  14  (a transfer unit) is arranged below the photosensitive drum  13 , and a bottom face of the photosensitive cartridge  3  is therebelow. The transfer roller  14  is axially supported to move vertically to separate from the lower face of the photosensitive drum  13  by its own weight. The transfer roller  14  is urged upwardly by springs (not shown) arranged on the right and left ends inside the main housing  1  to move and press a lower face (transfer area) of the photosensitive drum  13  when set inside the main housing  1  as a component of the process cartridge  2 . 
     The window opening  31  for irradiating the upper face of the photosensitive drum  13  with the laser light from the laser scanner unit  7  is formed longitudinally along an axial direction of the photosensitive drum  13  at an upper wall covering above the photosensitive drum  13  in a case of the photosensitive cartridge  3 . Further, a charger  36  such as a scorotron for charging a photosensitive face of the photosensitive drum  13  is arranged adjacent to the window opening  31 . The laser light scans the surface of the photosensitive drum  13  which is uniformly charged by the charger  36 , whereby an electrostatic latent image is formed and thin layer toner provided by the developing roller  22  to be described later is fed on the electrostatic latent image, which is then visible (manifested) and transferred to sheet P at a pressing transfer area between the transfer roller  14  and the photosensitive drum  13 . 
     Configuration of Developing Cartridge 
     Next, a description will be made for the configuration of the developing cartridge  4  by referring to  FIG. 1  through  FIG. 4 . In the following description, the “left side face” is a side face located on the left when a main housing  1  of a printer is viewed from the front face (arrow A), and the “right side face” is a side face on the opposite side. 
     As shown in  FIG. 1 , an agitator  27  is rotated inside a toner container  24  having a shape of downward convex curvature of a case  21  of the developing cartridge  4 . Accordingly, the toner contained inside the toner container  24  is released to a developing chamber  28 . The toner contained in the toner container  24  is developer of positively charged nonmagnetic single components. The toner contains core particles having a spherical shape with diameters of 5 μm to 10 μm and the volume mean particle diameter of 10 μm. The core particles are formed by a polymerization method such as a suspension polymerization method after known coloring agents such as carbon black and charge control agents such as nigrosine, triphenylmethane and quaternary ammonium salt are added to a mixture monomer of styrene with acryl. A core particle is added with silica as an external additive to the surface of the particles. The thus formed polymerized toner is high in fluidity and able to provide a highly elaborate development. The toner released into the developing chamber  28  is held on an outer peripheral face of the developing roller  22  through a providing roller  25  to form a layer. The layer thickness of the developer is regulated by a blade  26  (a regulating member). 
     As shown in  FIG. 2 , the developing roller  22  is rotatably supported at one end (an opening at the side of the photosensitive drum  13 ) of the case  21  of the developing cartridge  4 . The developing roller  22  includes a developing roller shaft  22   a  (roller shaft) made of metal such as stainless steel and a rubber roller  22   b  (elastic roller) that is supported by the developing roller shaft  22   a  and composed of a substrate given an electrical conductivity by dispersing carbon black to silicon rubber or urethane rubber. A fluorine-containing coat layer is formed on the surface of the rubber roller  22   b . Bearings  23   a  and  23   b  made of a material such as polyacetal resin with small friction coefficient are rotatably capped on the right and left ends of the developing roller shaft  22   a . Knob portions  21   f  for easily carrying or handling the developing cartridge  4  are provided respectively on the upper face and on the lower face of the case  21  of the developing cartridge  4  (only the upper face is shown in  FIG. 2 ). 
     Configuration of Seal Member on Developing Cartridge 
     The case  21  of the developing cartridge  4  further includes a leakage preventing member that prevents leakage of the toner from the case  21 . Next, a description will be made for a seal member which is one example of the leakage preventing member by referring to  FIG. 5 ,  FIGS. 11A and 10B . 
     An opening  340  is formed along an axial direction of the developing roller  22  at one end of the case  21  of the developing cartridge  4  (refer to  FIG. 1 ). The opening  340  is formed in a rectangular shape surrounded by an opening upper end  340   a  defining an upper end side in the longitudinal direction of the opening  340 , an opening lower end  340   b  defining a lower end side in the longitudinal direction of the opening  340  and opening side ends  340   c  and  340   c  defining both end sides in a transverse direction. 
     An upper seal  108  made of urethane sponge is attached to an area adjacent to the upper end  340   a  of the opening  340 , that is, an upper area of the upper end  340   a . The upper seal  108  extends in a longitudinal direction over a length substantially equal to the upper end  340   a  and includes sagged portions  108   e  that hang down so as to hang over upper areas adjacent to the both ends  340   c  and  340   c  of the opening  340 , a lower end  108   f  of the sagged portion  108   e  at the end of the sagged portion  108   e  is in contact with a shoulder  21   e  formed on the case  21  (refer to  FIGS. 10A and 10B ). As will be described later, a blade  26  is attached to the case  21  so that the blade  26  overlaps with the upper seal  108 . This configuration prevents toner leakage from above the opening  340  of the case  21  of the developing cartridge  4  or toner leakage which may occur when the developing cartridge  4  is inverted. 
     Side seals  109  (leakage preventing members) are attached on areas below the descent portions  108   e  of the upper seal  108  and adjacent to the opening both ends  340   c  and  340   c  of the case  21 , that is, on side areas of the opening at both ends  340   c  and  340   c . The side seals  109  prevent the toner leakage from both end portions of the rubber roller  22   b  by slidably contacting with both end portions of the rubber roller  22   b . Each side seal  109  is made of urethane sponge relatively high in stiffness among sponges (e.g. Poron® manufactured by Rogers Inoac Corporation), and has a certain thickness for exerting a predetermined pressing force when the developing roller  22  is attached and the side seals  109  are compressed. Each side seal  109  is attached to the case  21  by a double side adhesive tape or the like in an extending direction along a circumferential surface of the rubber roller  22   b  at a longitudinal end portion thereof. Each side seal  109  is disposed between both end portions of the rubber roller  22   b  and the case  21  which is opposed to the both end portions. 
     A lower film  110 , which has a width substantially equal to the lower end  340   b  of the opening  340 , is attached to an area adjacent to the lower end  340   b  of the opening  340 , that is, a lower area of the lower end  340   b . The lower film  110  is made of, for example, a PET sheet or urethane rubber film. In the first example, a PET sheet is used. The lower film  110  is attached to a part of the lower front edge  21   f  of the case  21  by a double side adhesive tape (refer to  FIGS. 11A and 10B ). The upper end side  110   e  of the lower film  110  is configured to slidably contact with a circumferential face of the developing roller  22 . The lower film  110  is attached as described above, thereby preventing toner leakage from a lower part of the opening  340  of the case  21  of the developing cartridge  4 . 
     After the upper seal  108 , the side seal  109  and the lower film  110  are attached, the blade  26 , shown in  FIGS. 6A and 6B , is attached to the case  21  while the blade  26  overlaps with the upper seal  108 . 
     As shown in  FIGS. 6A and 6B , the blade  26  includes: a supporting member  26   c  made of iron, stainless steel or the like; a thin plate-shaped leaf spring  26   b  made of phosphor bronze, stainless steel or the like mounted on the supporting member  26   c ; a pressing member  26   a  made of silicon rubber mounted on the leaf spring  26   b . Notched portions  26   d  notched concavely are formed in the vicinity of the ends of the leaf spring  26   b . The pressing member  26   a  is made of silicon rubber and has a shape being notched in a width similar to that of the notched portions  26   d.    
     The blade  26  is attached to the case  21  while a boss  115   a  of the case  21 , shown in  FIG. 5 , fits into a boss hole  26   e  formed on the supporting member  26   c  and screwing through a threaded hole  26   f  also formed on the supporting member  26   c . Thereafter, the developing roller  22  is attached to the case  21 , by which the pressing member  26   a  is configured to be in press-contact with the peripheral face of the developing roller  22  by an elastic force of the leaf spring  26   b  and the elastic force of silicon rubber itself. Therefore, the layer thickness of the toner on the developing roller  22  is regulated to a desired amount. 
     As shown in  FIG. 6A , the leaf spring includes a rib sponge  117  (first attached member) formed to have substantially the same width as the length of the leaf spring  26   b  in the longitudinal direction and also has an approximately U-lettered shape so as not to block the notched portion  26   d  is attached to the leaf spring  26   b  by using a double side adhesive tape. The rib sponge  117  is made of urethane sponge thicker than an upper seal  108 . When the blade  26  is attached to the case  21 , the rib sponge  117  press-contacts with the upper seal  108  (refer to  FIGS. 11A and 10B ). It is thereby possible to prevent toner from entering into the back face of the blade  26  and also prevent non-charged toner from feeding on the back face of the blade. 
     Next, description will be made for a configuration of the case  21  of the developing cartridge  4  to which the developing roller  22  is attached and a method for attaching the developing roller  22  by referring to  FIG. 7  through  FIG. 10B . The “thickness” of the side seal  109  described in the following indicates a thickness in a thickness direction perpendicular to a sliding surface that is defined between the side seal  109  and the rubber roller  22   b.    
     In order to attach the developing roller  22  to the case  21  of the developing cartridge  4 , a developing roller shaft  22   a  is inserted from each guide notch  350  formed on case side  21   a  of the case  21  on both sides of the developing roller  22  in a longitudinal direction. A developing roller shaft  22   a  is moved up to a second end portion  350   d  of each guide notch  350 , which is a attaching completion position (predetermined position) while the developing roller shaft  22   a  slides along the guide notch  350 . The guide notch  350  includes a first guide notch  350   a  extending from an opening-side front edge  21   b  at the case side  21   a  in the thickness direction of the side seal  109  and a second guide notch  350   b  extending along the extending direction of the side seal  109  up to the second end portion  350   d . The end portion of the first guide notch  350   a  is constituted as the first end portion  350   c.    
     The developing roller  22  moves up to the first end portion  350   c  while the developing roller shaft  22   a  slides along the first guide notch  350   a . The first end portion  350   c  is configured so that the rubber roller  22   b  compresses the side seal  109  in the thickness direction when the developing roller  22  is at the first end portion  350   c  (refer to  FIG. 8 ). 
     Thereafter, the developing roller shaft  22   a  slides along the second guide notch  350   b  and moves up to the second end portion  350   d , by which the developing roller  22  is placed at the attaching completion position (the predetermined position) as shown in  FIG. 9 . In the second guide notch  350   b , a part from the first end portion  350   c  to the second end portion  350   d  extends along the extending direction of the side seal  109 . The rubber roller  22   b  is configured so that the both ends thereof rotate while slidably contacting with the side seals  109 . The side seal  109  is attached along the extending direction along a circumferential surface of the rubber roller  22   b  at a longitudinal end portion thereof. 
     That is, the rubber roller  22   b  compresses each side seal  109  in the thickness direction at the first end portion  350   c . Then, the developing roller shaft  22   a  moves along the second guide notch  350   b  so that the developing roller  22  slides and moves up to the second end portion  350   d  while compressing the side seal  109  with rubber roller  22   b . Therefore, as shown in  FIG. 10B , the side seal  109  is pressed toward an upper end side  109   e  located on the downstream side of a rotation direction of the developing roller  22  due to friction between the side seal  109  and the surface of the rubber roller  22   b . More specifically, in a state where the developing roller  22  is placed at the attaching completion position, a face which is in a sliding contact with the rubber roller  22   b  on the upper end side  109   e  of the side seal  109  is pressed toward the blade  26 . Further, in response to such action, the side seal  109  is also subjected to be pressed toward a rib sponge  117 . The rib sponge  117  is attached to the back face of the blade  26  while contacting edges of the side seal  109  at the downstream side of a rotation direction of the developing roller. 
     When the developing roller  22  is attached by an operator, the case  21  is often placed on a work table, with the toner container  24  placed below in the vertical direction, and with the developing chamber  28  and the opening  340  placed above in the vertical direction. In this state, when the developing roller  22  is located at the first end portion  350   c , the side seal  109  is compressed in the direction of thickness by the weight of the developing roller  22  itself. Therefore, the operator is not required to have special skill in pressing the side seal  109  in the thickness direction. Further, only by a simple operation in which the operator slides the developing roller  22  along the second guide notch  350   b  from the above state, it is possible to press the side seal  109  toward the attaching completion position of the developing roller  22  using friction between the surface of the rubber roller  22   b  and that of the side seal  109 . 
     Thereafter, in order to keep this state, a bearing member  21   g  as a retaining member is attached to the right end of the developing roller shaft  22   a  (refer to  FIG. 4 ). Thereafter, a bearing body  23   b  is attached. At the left end of the developing roller shaft  22   a  which is an opposite side shown in  FIG. 4  (refer to  FIG. 3 ), a bearing member as a retaining member is fixed in a similar manner. However, since a plurality of gears including a driving gear  22   c  for driving the developing roller  22  are included on this side, the bearing member has a size and configuration so as not to affect the operation of these gears. In the first example, the bearing member is smaller in diameter than the driving gear  22   c . As described so far, after the bearing member (not visible behind the driving gear  22   c  in  FIG. 3 ) is attached also to the left end of the developing roller shaft  22   a , the driving gear  22   c  is fitted and the bearing body  23   a  is then attached further outside. 
     As described above, the bearing member  21   g  is attached for retaining the developing roller  22  at an attaching completion position, by which the developing roller shaft  22   a  is fixed at the second end portion  350   d . The bearing member  21   g  according to the first example includes a supporting hole, a diameter of which is approximately equal to that of a developing roller shaft  22   a , and an engaging portion for positioning. The case side  21   a  includes an engage portion to be engaged with the engaging portion of the bearing member  21   g . In this instance, the engaging portion of the bearing member  21   g  may be given as a projection for positioning and the engage portion on the case side  21   a  may be given as a hole for positioning, or vice versa. Further, the engaging portion and the engage portion may be provided in any given numbers that are able to retain the developing roller  22  at the attaching completion position of the case  21 . Then, since the bearing member  21   g  is attached, the developing roller  22  is retained so as to rotate at the attaching completion position. 
     Further, as described above, the bearing members  21   g  may be attached outside the case side  21   a . Alternatively, the developing roller shaft  22   a  may be inserted into the guide notch  350  in a state where the bearing members  21   g  are in advance kept attached to both end portions of the developing roller shaft  22   a , and individually engaged inside the case side  21   a  when the developing roller shaft  22   a  is placed at the second end portion  350   d.    
     Further, in place of engaging the bearing members, it may be possible to fix the developing roller  22  at the attaching completion position by modifying a configuration of the guide notch  350  by itself. Specifically, as shown in  FIG. 11 , the projection  350   e  as a retaining member projects toward the second guide notch  350   b  on the opening-side front edge  21   b  side of the guide notch  350  (the side opposite the second guide notch  350   b ). Since the projection  350   e  projects toward the second guide notch  350   b , a clearance between the second guide notch  350   b  and the opposite side becomes narrow. Thereby, when the developing roller shaft  22   a  is moved beyond the projection  350   e  and arranged at the second end portion  350   d , the developing roller shaft  22   a  is fixed at the position concerned. This projection  350   e  is formed on the side of opening-side front edge  21   b  of the guide notch  350 , and not formed on the second guide notch  350   b  which is the opposite side thereof. When a projection is formed on the second guide notch  350   b , the developing roller shaft  22   a  sliding along the second guide notch  350   b  becomes loose by the projection. Then, the side seal  109  fails to be pressed effectively toward the attaching completion position. However, since the second guide notch  350   b  according to the first example is formed as a smooth guide up to the second end portion  350   d , the developing roller shaft  22   a  slides up to the second end portion  350   d  while the side seal  109  is kept compressed in the thickness direction, whereby the side seal  109  is effectively pressed toward the attaching completion position. 
     As described above, an operator only slides the developing roller  22  along the guide notch  350 , whereby the side seal  109  is pressed toward the attaching completion position of the developing roller  22 . It may be possible to suppress formation of a clearance in the vicinity of the upper end side  109   e  of the side seal when attaching the developing roller  22 . Since the side seal  109  is pressed toward the downstream side of the rotation direction of the developing roller  22 , the rotation direction of the developing roller  22  coincides with a deforming direction to which the side seal  109  is forcibly deformed. Therefore, even when the developing roller  22  is rotated in the process of forming images, the falling direction of the side seal does not change. Thus, it may be possible to maintain a state in which formation of a clearance is suppressed. Further, since the side seal  109  is pressed toward the blade  26  and the rib sponge  117  on the back face of the blade  26  by the rubber roller  22   b  at the time of attaching the developing roller  22 , a clearance between the side seal  109  and the blade  26  is rarely formed. Thus, it may be possible to reduce the toner leakage from this clearance. Since the side seal  109  is pressed and deformed toward the rib sponge  117  which is made of elastic material, the rib sponge  117  deforms by the action of the side seal  109 . Therefore, the side seal  109  and the rib sponge  117  are firmly stuck together. Thus, it may be possible to effectively prevent toner leakage from this portion. 
     Second Example 
     The present invention shall not be restricted to the first example described above with reference to the drawings, but the following example is also included in the technical scope of the present invention. The second example is different from the first example in that the upper end side  109   e  of the side seal  109  is not in contact with the rib sponge  117  but, instead, in contact with the rib  21   c  projecting from the case  21 . Other constitutions which are the same as those of the first example are given the same numerals and symbols, and a detailed description will be omitted here. 
     When attaching the developing roller  22  to the case  21 , the developing roller shaft  22   a  is inserted along the attaching guide notch  350  in a sliding manner, and moved up to the first end portion  350   c . In this state, the side seal  109  is kept compressed in the thickness direction by the rubber roller  22   b . When the developing roller shaft  22   a  is slid and moved from the first end position  350   c  up to the second end portion  350   d  which is to be an attaching completion position of the developing roller  22 , the side seal  109  is pressed and deformed toward the rib  21   c  (second attached member) by friction between the surface of the rubber roller  22   b  and that of the side seal  109 . 
     As shown in  FIGS. 14A and 14B , when the developing roller  22  is attached according to a conventional method, it is impossible to predict a direction to which side the side seal  109  falls down and there are some cases where a clearance  100  as shown in  FIG.14B  is formed in the vicinity of the upper end side  109   e . This clearance causes toner leakage from this part to result in scatter of toner inside a printer. However, according to the configuration of the second example, since the side seal  109  is pressed and deformed toward the rib  21   c  (projection) provided in the vicinity of a attaching completion position of the developing roller  22  when attaching the developing roller  22 , a frequency of forming a clearance between the side seal  109  and the rib  21   c  is reduced and toner leakage is prevented.