Abstract:
A process cartridge and an electrophotographic image forming apparatus incorporating the same. The process cartridge includes an electrophotographic photosensitive member, a container supplying a developer to the electrophotographic photosensitive member, a cleaning member including a blade and a support portion supporting the blade, the blade selectively contacting the electrophotographic photosensitive member to remove the developer from the electrophotographic photosensitive member, and a cartridge frame supporting the electrophotographic photosensitive member and the support portion, the cartridge frame including a contact portion contacting the support portion under external forces on the cartridge frame to prevent deformation of the cartridge frame.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an electrophotographic image forming apparatus and a process cartridge for use with the electrophotographic image forming apparatus. 
   2. Description of the Related Art 
   An electrophotographic image forming apparatus is an apparatus for forming an image onto a recording medium by an electrophotographic image forming system. Examples of such apparatuses include electrophotographic copying machines, electrophotographic printers (e.g., laser-beam printers, LED printers), facsimile machines, and word processors. 
   A process cartridge can include at least cleaning means and an electrophotographic photosensitive drum, and can be detachably mounted to the body of the image forming apparatus. 
   Conventional electrophotographic image forming apparatuses using an electrophotographic image forming process adopt a process cartridge system in which an electrophotographic photosensitive member and process means for the electrophotographic photosensitive member are integrated in a cartridge, which can be detachably mounted to an image forming apparatus body. With such process cartridge system, users can themselves maintain the apparatus and do not require repair people, thus significantly improving ease of use. Such process cartridge system is widely used in image forming apparatuses. 
   Recently, multicolor-image forming apparatuses utilize a plurality of process cartridges of different colors. Providing the plurality of process cartridges detachable to the image forming apparatus body improves ease of use for users. 
   The multicolor-image forming apparatus can be personalized by vertically disposing a plurality of process cartridges to reduce its installation area in view of space saving. 
   The image forming apparatus with the above structure may have a flat process cartridge to reduce the height. 
   For this purpose, for example, a technique for cleaning means is disclosed in Japanese Patent Laid-Open No. 10-301460 in which waste toner, which is a transfer residual developer agent, is carried horizontally and a waste-toner storage chamber is formed in a flat shape. 
   With the above-described structure, the rigidity of the part where the waste-toner storage means is disposed becomes lessened. As such, when the user strongly grasps the process cartridge, the waste-toner storage chamber may be deformed. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a compact process cartridge configured such that, when a user grasps the process cartridge, a frame of the process cartridge is prevented from substantially deforming. 
   The present invention is directed to a compact process cartridge configured such that, when a user grasps the process cartridge, leakage of developer from the process cartridge is prevented. 
   The present invention is also directed to an electrophotographic image forming apparatus to which the process cartridge is detachably mounted. 
   In one aspect of the present invention, the process cartridge includes an electrophotographic photosensitive member, a cleaning member including a blade and a support portion supporting the blade, the blade contacting the electrophotographic photosensitive member to remove the developer from the electrophotographic photosensitive member, and a cartridge frame supporting the electrophotographic photosensitive member and the support portion, the cartridge frame including a contact portion contacting the support portion under an external force on the cartridge frame to prevent deformation of the cartridge frame. 
   In one embodiment, the contact portion includes a rib projecting from the frame to contact the support portion. 
   Further features and advantages of the present invention will become apparent from the following description of the embodiments with reference to the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a cleaning unit according to an embodiment of the present invention. 
       FIG. 2  is a schematic diagram of a color image-forming apparatus in accordance with one embodiment of the present invention. 
       FIG. 3  is a schematic diagram of process cartridges used in the color image-forming apparatus shown in  FIG. 2 . 
       FIG. 4  is a cross-sectional view of the overall structure of a process cartridge. 
       FIG. 5  is a perspective view of the structure of the process cartridge. 
       FIG. 6  is a perspective view of the process cartridge. 
       FIG. 7  is a partial perspective view of a cleaning unit according to the invention. 
       FIG. 8  is a perspective view showing the relationship between a cleaning frame and a sealing member according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A developer unit, a process cartridge, and an image forming apparatus including the same according to an embodiment of the present invention will now be described. 
   [Overall Structure of Color-Image Forming Apparatus] 
   The overall structure of a color-image forming apparatus will be schematically described with reference to  FIGS. 2 and 3 .  FIG. 2  is a schematic diagram of a color image-forming apparatus  200  in accordance with one embodiment of the present invention. The color image-forming apparatus  200  can be a color laser printer, for example.  FIG. 3  is a schematic diagram of process cartridges  7  used in the color image-forming apparatus  200  shown in  FIG. 2 . 
   Referring to  FIG. 2 , the color laser printer  200  includes an image forming section having photosensitive drums  1   a ,  1   b ,  1   c , and  1   d  (collectively referred to as photosensitive drum  1 ) for each of yellow, magenta, cyan, and black colors, respectively. The printer  200  also includes an intermediate transfer member  5  that holds a color image developed by the image forming section and transferred in multiple colors. The intermediate transfer member  5  transfers the color image to a recording medium (transfer material) P fed by feeding means. The photosensitive drums  1   a ,  1   b ,  1   c , and  1   d  are rotated counterclockwise in the drawing by driving means (not shown). Around the photosensitive drum  1  is provided in the rotating direction charging means  2  ( 2   a ,  2   b ,  2   c , and  2   d ) for uniformly charging the surface of the photosensitive drum  1  with electricity, a scanner unit  3  ( 3   a ,  3   b ,  3   c , and  3   d ) for emitting a laser beam according to image information to form an electrostatic latent image on the photosensitive drum  1 , a developer unit  4  ( 4   a ,  4   b ,  4   c , and  4   d ) for applying toner, which is a developer agent, to the electrostatic latent image to develop it as a toner image, and a photoconductor unit  6  ( 6   a ,  6   b ,  6   c , and  6   d ) for transferring the toner image on the photosensitive drum  1  to a primary transfer region T 1  of the intermediate transfer member  5 . The photoconductor unit  6  includes a cleaning unit for removing residual toner left on the surface of the photosensitive drum  1  after transfer. The toner image transferred to the intermediate transfer member  5  is further transferred onto the recording medium P with a transfer roller  13  at a transfer region T 2 . The recording medium P onto which the color image has been transferred is carried to fixing means  8 , in which the color image is fixed to the recording medium P. The recording medium P is then discharged to an output tray  26  by discharge rollers  25 . 
   The photosensitive drum  1 , charging means  2 , the developer unit  4 , and the photoconductor unit  6  are integrated into a process cartridge  7 . 
   Referring to  FIG. 3 , an image-forming apparatus body  100  includes an opening cover  29  integrated with the intermediate transfer member  5 . The process cartridge  7  can be mounted to or dismounted from the image-forming apparatus body  100  when the opening cover  29  is opened and the photosensitive drum  1  set on this side. 
   The components of the image forming apparatus  200  will be specifically described hereinafter. 
   [Photosensitive Drum] 
   The photosensitive drum  1  will now be described in detail. 
   The photosensitive drum  1  includes an organic photoconductor (OPC) layer applied onto an outer surface of an aluminum cylinder with a diameter of, for example, 30 mm. The ends of the photosensitive drum  1  are rotatably supported by a supporting member (not shown). A drive motor (not shown) transmits a drive force to one or both ends of the drum  1  to drive the photosensitive drum  1  in a counterclockwise direction, for example. 
   [Charging Means] 
   The charging means  2  employs a contact-roller electrifying system. The charging means  2  is a conductive roller that is brought into contact with the surface of the photosensitive drum  1  to uniformly charge the surface of the photosensitive drum  1  with electricity by applying charging bias to the charging means  2 . 
   [Exposure Means] 
   The scanner unit  3  serving as exposure means emits an image light corresponding to an image signal to the polygon mirror  9  ( 9   a ,  9   b ,  9   c , and  9   d ), which is rotated at a high speed by a scanner motor. The image light reflected by the polygon mirror  9  selectively exposes the surface of the photosensitive drum  1  rotating at a fixed speed with light through an imaging lens, thereby forming an electrostatic latent image onto the photosensitive drum  1 . 
   [Developer Unit] 
   The developer unit  4  includes a toner container  41  that accommodates yellow, magenta, cyan, and black toners to visualize the electrostatic latent image. The toners in the toner container  41  are fed to a toner supply roller  43  with a toner mixing and feeding mechanism  42 . The toner supply roller  43  rotates clockwise in the Z-direction and is in pressure contact with a developing roller  40 . Electrically charged toner is applied to the outer surface of the developing roller  40 , which is rotating clockwise (in the Y-direction), via a developing blade  44  and the toner supply roller  43 . 
   A developing bias is applied to the developing roller  40  facing the photosensitive drum  1  on which an electrostatic latent image is formed, thereby developing the latent image. 
   [Intermediate Transfer Member] 
   The intermediate transfer member  5  rotates clockwise in synchronization with the outer speed of the photosensitive drum  1 , as shown in  FIG. 2 . A primary transfer roller  12  ( 12   a ,  12   b ,  12   c , and  12   d ) is disposed to face the photosensitive drum  1  with the intermediate transfer member  5  sandwiched therebetween. The toner image formed on the photosensitive drum  1  is transferred onto the intermediate transfer member  5  by application of voltage to the primary transfer roller  12 . The intermediate transfer member  5 , which receives the transferred image, then transfers the toner image onto the recording medium P via the transfer roller  13  having an applied voltage. 
   The intermediate transfer member  5  (intermediate transfer belt) according to the embodiment is stretched over a driving roller  14 , a transfer opposing roller  15 , and a tension roller  16 . 
   The intermediate transfer member  5  is supported to the apparatus body  100  with the driving roller  14  as the fulcrum. The driving force of the drive motor (not shown) is transmitted to the intermediate transfer member  5  at one end of the driving roller  14  to rotate the intermediate transfer member  5  clockwise (in the direction of the arrow) with the image forming operation. 
   [Feeding Means] 
   The feeding means feeds the recording medium P to the image forming section. The feeding means includes a cassette  17 , a feed roller  18 , a separation pad  19 , a guide  20 , and a registration roller pair  21 . During an image forming operation, the feed roller  18  rotates to feed the recording medium P in the cassette  17  one by one. The recording medium P is guided by the guide  20  and passes through the feed roller  18  to reach the registration roller pair  21 . During the image forming operation, the registration roller pair  21  performs a stop operation to stop the recording medium P in standby mode, performs a rotating operation of feeding the recording medium P towards the intermediate transfer member  5  in a predetermined sequence, and also adjusts the transfer position of the image for transferring on the recording medium in the following process. 
   [Transfer Means] 
   A transfer means includes the movable transfer roller  13 . The transfer roller  13  contacts the intermediate transfer member  5  with a specified pressure during transfer of a color image onto the recording medium P. At the same time, the transfer roller  13  is provided with a bias so that the toner image on the intermediate transfer member  5  is transferred onto the recording medium P. The recording medium P is transferred to the left at a specified speed during the transfer operation, towards the fixing means  8 . 
   [Fixing Means] 
   The fixing means  8  fixes the toner image formed on the recording medium P. Specifically, the fixing means  8  includes a film guide unit  23  having a built-in ceramic heater for heating the recording medium P and a pressure roller  24  for bringing the recording medium P into pressure contact with the film guide unit  23 . 
   [Image Forming Operation] 
   The operation of image formation with the apparatus constructed above will be described. 
   The feed roller  18 , shown in  FIG. 2 , is rotated to separate one recording medium P in the cassette  17  and carry it to the registration roller pair  21 . 
   The photosensitive drum  1  and the intermediate transfer member  5  are individually rotated in the direction of the arrow at a predetermined circumferential speed V (hereinafter, referred to as a process speed). 
   The surface of the photosensitive drum  1 , which is uniformly electrified by the charging means  2 , is exposed to laser light to form an image. 
   Latent-image formation, development, and toner transfer to the intermediate transfer member  5  are each performed in the respective primary transfer positions T 1  in the order of yellow, magenta, cyan, and black, forming a full-color image made of four toners (yellow, magenta, cyan, and black colors) on the surface of the intermediate transfer member  5 . The full-color image on the intermediate transfer member  5  is transferred onto the recording medium P with all the four colors at the same time. The recording medium P that has passed through the transfer region T 2  is separated from the intermediate transfer member  5 , carried to the fixing means  8 , and discharged to the output tray  26  through the discharge rollers  25  after toner fixing operation. The image forming operation is thus finished. 
   [Structure of Process Cartridge] 
   A process cartridge embodying the present invention will be specifically described with reference to  FIGS. 4 and 5 .  FIG. 4  is a main cross-sectional view of the process cartridge  7  which accommodates toner.  FIG. 5  is a perspective view of the process cartridge  7 .  FIG. 6  is a perspective view of the process cartridge. The respective process cartridges  7   a ,  7   b ,  7   c , and  7   d  of yellow, magenta, cyan, and black colors have the same structure. 
   As shown in  FIGS. 4 and 5 , the process cartridge  7  is divided into the photoconductor unit  6  and the developer unit  4 . The photoconductor unit  6  includes the photosensitive drum  1 , the charging means  2 , and a cleaning blade  60 . The developer unit  4  includes the developing roller  40  for developing the electrostatic latent image on the photosensitive drum  1 . 
   The photosensitive drum  1  of the photoconductor unit  6  is rotatably mounted to a cleaning frame  61  through a bearing member  31 . Disposed around the outer surface of the photosensitive drum  1  is the charging means  2  for uniformly charging the surface of the photosensitive drum  1  with electricity and the cleaning blade  60  for removing the toner remaining on the photosensitive drum  1 . 
   The blade  60  includes an elastic cleaning portion  60   a  that contacts the photosensitive drum  1 , and a support plate  60   b  fixed to the cleaning frame  61  for supporting the cleaning portion  60   a.    
   The material for the cleaning portion  60   a  can be an elastomer such as urethane and silicone, which is a urethane rubber with a hardness of  710  (Wallace) in this embodiment. The support plate  60   b  can be made of a rigid material, such as a cold rolled steel sheet of t=1.6. 
   If the contact pressure of the blade  60  on the photosensitive drum  1  is not uniform in the longitudinal direction, there may be incomplete cleaning which has significant effects on the image quality. As such, the blade  60  is accurately fixed to the cleaning frame  61 . 
   The residual toner removed from the surface of the photosensitive drum  1  with the blade  60  is sequentially carried to a waste-toner chamber  63  provided at the rear of the cleaning frame  61  with a toner-carrying mechanism  62 . The driving force of the drive motor (not shown) at one end of the rear is transmitted to the photosensitive drum  1  to rotate the photosensitive drum  1  counterclockwise during the image forming operation. 
   The developer unit  4  includes the developing roller  40  that contacts the photosensitive drum  1  and rotates in the direction of arrow Y. The developer unit  4  also includes the toner container  41  for accommodating toner, and a developer container  45 . The developing roller  40  is rotatably supported by the developer container  45  with developer bearings  47  and  48 . On the outer surface of the developing roller  40  is disposed the toner supply roller  43 , which rotates in the direction of arrow Z, and the developing blade  44 . The toner container  41  includes the toner mixing and feeding mechanism  42  therein for mixing the accommodated toners and carrying them to the toner supply roller  43 . 
   As shown in  FIG. 5 , the developer unit  4  is provided with support holes  49  at the developer bearings  47  and  48 . The developer unit  4  has a suspension structure rotatably supported to the photoconductor unit  6  with support pins  49   a  and the support holes  49 . 
   Without the process cartridge  7  mounted to a printer body, the developer unit  4  is constantly biased by a pressure spring  64  so that the developing roller  40  is brought into contact with the photosensitive drum  1  around the support pins  49   a  (refer to  FIG. 4 ). 
   During a developing operation, the accommodated toner is carried to the toner supply roller  43  via the toner mixing and feeding mechanism  42 . The toner supply roller  43 , which rotates in the direction of arrow Z, feeds the toner onto the developing roller  40  by sliding friction with the developing roller  40 , which is rotating in the direction of arrow Y. The toner is thus supplied onto the developing roller  40 . The toner on the developing roller  40  is moved to the developing blade  44  as the developing roller  40  rotates. The developing blade  44  applies an electrical charge to the toner to form them into a specified thin layer of toner. The toner is then carried to a developing section where the photosensitive drum  1  and the developing roller  40  are in contact with each other. The toner adhers to the electrostatic latent image formed on the surface of the photosensitive drum  1  by a direct-current developing bias applied from a power source (not shown) to the developing roller  40 , thereby developing the latent image. Toner that does not contribute to the development and remains on the surface of the developing roller  40  is returned into the developer unit  4 . As the developing roller  40  rotates, the toner is separated and collected from the developing roller  40  at the sliding frictional section with the toner supply roller  43 . The collected toner is mixed with remaining toners by the toner mixing and feeding mechanism  42 . 
   In the contact developing system for developing by the contact of the photosensitive drum  1  and the developing roller  40 , the photosensitive drum  1  can be a rigid member and the developing roller  40  can be an elastic member. The elastic member includes a single solid-rubber layer and a resin coating on the solid rubber layer in view of a toner electrizing characteristic. 
   The toner supply roller  43  is an elastic roller made of a core metal and a sponge, of which the sponge is formed of continuously foamed sponge. 
   EMBODIMENTS OF THE INVENTION 
   The structure of an image forming apparatus according to the present invention and a process cartridge used therein will be specifically described with reference to  FIGS. 1 to 4 . 
   PRINCIPAL STRUCTURE OF THE INVENTION 
     FIG. 1  is a perspective view of a cleaning unit according to an embodiment of the present invention.  FIG. 7  is a partial perspective view of the cleaning unit according to the invention.  FIG. 8  is a perspective view showing the relationship between a cleaning frame and a sealing member according to the invention. The cleaning frame  61  includes an upper plate  61   a , opposite side plates  61   b  and  61   c , a front wall  61   d , and cleaning-blade support portions  61   e  and  61   f . The waste-toner chamber  63  is provided at the rear of the cleaning frame  61 . 
   Opposite ends  60   b   1  and  60   b   2  of the support plate  60   b  of the cleaning blade  60  are fixed to the opposite ends  61   e  and  61   f  of the cleaning frame  61  with fixing members such as screws  66 . Thus, the cleaning blade  60  is in contact with the photosensitive drum  1  supported by the cleaning frame  61 . 
   The upper plate  61   a  has a downward rib  65  at the center, which is a contact portion. The rib  65  has an end  65   a  which is adjacent to the center  60   b   3  of the cleaning-blade support plate  60   b . The distance between the end  65   a  and the center  60   b   3  of the cleaning-blade support plate  60   b  is within the range of 0 to 1 mm, for example, which is set at 0.5 mm in this embodiment. This structure provides a support between the rigid metal plate and the upper plate  61   a  of the cleaning frame  61  even if a user strongly grasps the process cartridge vertically, thus eliminating the possibility of leakage of waste toner. 
   Also, a very small space is provided between the end of the rib  65  provided to the cleaning frame  61  and the cleaning-blade support plate  60   b . This prevents application of a force that will deform the cleaning blade  60  during image forming operation, thus providing a preferable image. 
   As described above, according to the embodiment, even a compact flat process cartridge can have sufficient rigidity without causing leakage of waste toner. 
   In this embodiment, no undesired force is applied to the cleaning member during image formation, thus providing a preferable image. 
   As described above, according to the embodiment, a more compact process cartridge can be provided and the deformation of the cartridge frame can be prevented when it is grasped. 
   While the present invention has been described with reference to what are presently considered to be the embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 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.