Patent Publication Number: US-7212768-B2

Title: Process cartridge and electrophotographic image forming apparatus

Description:
FIELD OF THE INVENTION AND RELATED ART 
   The present invention relates to a process cartridge and an electrophotographic image forming apparatus. 
   The electrophotographic image forming apparatus forms an image on a recording material through an electrophotographic image formation type process. The electrophotographic image forming apparatus may be an electrophotographic copying machine, an electrophotographic printer (an LED printer, a laser beam printer or the like), an electrophotographic printer type facsimile machine, an electrophotographic printer type word processor or the like. 
   In the field of an electrophotographic image forming apparatus using an electrophotographic image process, a process cartridge type is known in which an electrophotographic photosensitive member, i.e., an electrophotographic photosensitive drum and process means actable on the electrophotographic photosensitive drum are integrally contained in a cartridge which is detachably mountable to a main assembly of an electrophotographic image forming apparatus as a unit. Such a process cartridge type is advantageous in that a maintenance operation of the apparatus can be performed by the user without relying on a serviceman, and therefore, the operability is good. Therefore, the process cartridge type is widely used in the field of image forming apparatus. 
   In an electrophotographic image forming apparatus, the light corresponding to image information is projected from a laser, an LED or a lamp onto an electrophotographic photosensitive drum (photosensitive drum). This forms an electrostatic latent image on the photosensitive drum. The electrostatic latent image thus produced is developed by a developing member which is built into the process cartridge. The developed image formed on the photosensitive drum is transferred onto the recording is material. In this manner, an image is formed on a recording material. 
   In a conventional example, a developing device includes a developing roller swingably supported on a supporting shaft provided in the main assembly of the image forming apparatus, and a follow gear for transmitting the driving to the developing roller (Japanese Laid-open Patent Application Sho 55-15177). The follow gear is rotatably supported on an outside of a side plate supporting the developing roller, and it is brought into meshing engagement with a driving gear provided in the main assembly of the image forming apparatus to transmit the driving force. The developing device is correctly positioned relative to the main assembly of the image forming apparatus by the side plate abutting to a stopper provided in the main assembly of the image forming apparatus. With this arrangement, the position where the driving force is transmitted to the follow gear and the position where the side plate is abutted to the stopper are different in the longitudinal direction of the developing device. Therefore, when the driving is transmitted from the driving gear, the developing device is subjected to a moment about the position where the side plate is abutted to the stopper with respect to the longitudinal direction of the developing device. There is a possibility that the moment adversely affects the positional accuracy of the developing roller and so on. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is a principal object of the present invention to provide a process cartridge and an electrophotographic image forming apparatus, in which the process cartridge is subjected to less bending moment and less deformation thereof when the process cartridge set in place in the main assembly of the electrophotographic image forming apparatus and receives the driving force from the main assembly of the apparatus. 
   It is another object of the present invention to provide a process cartridge and an electrophotographic image forming apparatus in which the deformation of the process cartridge is suppressed, the deformation being otherwise caused by the force received by the driving input gear within the engagement range between the driving input gear and the main assembly driving gear when the process cartridge set in place in the main assembly of the electrophotographic image forming apparatus and receives the driving force from the main assembly of the apparatus. 
   It is a further object of the present invention to provide a developing cartridge, a process cartridge and an electrophotographic image forming apparatus in which even when the rotational driving force is transmitted from the main assembly of the electrophotographic image forming apparatus, the developing roller is kept positioned with high accuracy relative to the main assembly of the apparatus. 
   It is a further object of the present invention to provide a developing cartridge, a process cartridge and an electrophotographic image forming apparatus which are downsized. 
   According to an aspect of the present invention, there is provided a process cartridge detachably mountable to an electrophotographic image forming apparatus, the process cartridge comprising an electrophotographic photosensitive drum extending in a longitudinal direction of the process cartridge; a developing roller for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; a first cartridge positioning portion which is provided at each of one and the other longitudinal end portion of the process cartridge and which is abuttable to a first main assembly positioning portion provided in the main assembly of the apparatus to position the process cartridge with respect to a direction crossing the longitudinal direction, when the process cartridge is mounted to the main assembly of the apparatus; a second cartridge positioning portion which is provided at one longitudinal end portion of the process cartridge and which is abuttable to a second main assembly positioning portion provided in the main assembly of the apparatus to limit rotation of the process cartridge about the first cartridge positioning portion, when the process cartridge receives a rotational driving force for rotating the developing roller from the main assembly of the apparatus; and a first drive input gear, provided at the one longitudinal end portion, for engagement with a main assembly driving gear provided in the main assembly to transmit a rotational driving force to the developing roller the range of engagement, with respect to the longitudinal direction, between the main assembly driving gear and the input gear when the input gear is engaged with the main assembly gear, overlaps with the second cartridge positioning portion as seen in a direction which is perpendicular to the longitudinal direction and which passes through the second cartridge positioning portion. 
   According to another aspect of the present invention, there is provided an electrophotographic image forming apparatus for forming an image on a recording material, to which a process cartridge is detachably mountable, The apparatus comprises (a) a first main assembly positioning portion; (b) a second main assembly positioning portion; (c) a main assembly driving gear; and (d) a mounting means for detachably mounting a process cartridge. The process cartridge includes: an electrophotographic photosensitive drum extending in a longitudinal direction of the process cartridge; a developing roller for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; a first cartridge positioning portion which is provided at each of one and the other longitudinal end portion of the process cartridge and which is abuttable to the first main assembly positioning portion provided in the main assembly of the apparatus to position the process cartridge with respect to a direction crossing the longitudinal direction, when the process cartridge is mounted to the main assembly of the apparatus; a second cartridge positioning portion which is provided at one longitudinal end portion of the process cartridge and which is abuttable to the second main assembly positioning portion provided in the main assembly of the apparatus to limit rotation of the process cartridge about the first cartridge positioning portion, when the process cartridge receives a rotational driving force for rotating the developing roller from the main assembly of the apparatus; and a first drive input gear, provided at the one longitudinal end portion, for engagement with a main assembly driving gear provided in the main assembly to transmit a rotational driving force to the developing roller. The range of engagement, with respect to the longitudinal direction, between the main assembly driving gear and the first drive input gear when the first drive input gear is engaged with the main assembly gear, overlaps with the second cartridge positioning portion as seen in a direction which is perpendicular to the longitudinal direction and which passes through the second cartridge positioning portion. The apparatus further comprises (e) feeding means for feeding the recording material. 
   These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of an example of a multi-color image forming apparatus according to an embodiment of the present invention. 
       FIG. 2  is a main sectional view of a process cartridge according to an embodiment of the present invention. 
       FIGS. 3(   a ) and  3 ( b ) are perspective views of a process cartridge according to an embodiment of the present invention. 
       FIG. 4  is a schematic perspective view of the main assembly of the image forming apparatus in which the process cartridge is mounted thereto according to an embodiment of the present invention. 
       FIG. 5  is a perspective view of a process cartridge according to an embodiment of the present intention. 
       FIG. 6  is a perspective view of a process cartridge according to an embodiment of the present invention. 
       FIG. 7  is a sectional view of a drive transmission path according to an embodiment of the present invention. 
       FIG. 8  is a sectional view of a process cartridge according to an embodiment of the present invention. 
       FIG. 9  is a sectional view of a process cartridge according to an embodiment of the present invention. 
       FIG. 10  is a sectional view of a process cartridge according to an embodiment of the present invention. 
       FIG. 11  is a side view of a process cartridge according to an embodiment of the present invention. 
       FIG. 12  is a sectional view of a process cartridge according to an embodiment of the present invention. 
       FIG. 13  is a sectional view of a process cartridge according to an embodiment of the present invention. 
       FIGS. 14(   a ) and  14 ( b ) are sectional views of a process cartridge according to an embodiment of the present invention. 
       FIGS. 15(   a ) and  15 ( b ) are sectional views of a process cartridge according to an embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   A description will be provided as to a developing unit, a process cartridge and an electrophotographic image forming apparatus according to an embodiment of the present invention. 
   (General Arrangement of Image Forming Apparatus) 
   Referring to  FIG. 1 , a description will first be provided as to the general arrangement of the multi-color image forming apparatus.  FIG. 1  is a longitudinal sectional view illustrating a general arrangement of a full-color laser beam printer  100  which is an example of a multi-color image forming apparatus. 
   The multi-color image forming apparatus  100  shown in this figure includes four photosensitive drums  1   a ,  1   b ,  1   c ,  1   d  which are arranged substantially vertically. The photosensitive drum  1  is rotated in the counterclockwise direction in the figure by a driving means (unshown). Around the photosensitive drum  1 , there are provided charging means  2  for electrically charging the associated photosensitive drum  1  to a uniform potential, a scanner unit ( 3   a ,  3   b ,  3   c ,  3   d ) for forming an electrostatic latent image on the photosensitive drum  1  by exposing it with a laser beam modulated in accordance with image information, and a developing unit  4  ( 4   a ,  4   b ,  4   c ,  4   d ) for developing the electrostatic latent image with a developer, electrostatic transferring means  5  for transferring the toner image provided by the development from the photosensitive drum  1  onto a recording material S, and cleaning means ( 6   a ,  6   b ,  6   c ,  6   d ) for removing untransferred toner remaining on the surface of the photosensitive drum  1  after the image transfer, in the order named. 
   In this embodiment, the photosensitive drum  1 , the charging means  2 , the developing unit  4 , and the cleaning means are contained in a cartridge  7  ( 7   a – 7   d ) as a unit. 
   The photosensitive drum  1  has a photosensitive layer on an outer surface of an aluminum cylinder, for example. The photosensitive drum  1  is rotatably supported on a cleaning frame  51  (first frame) by end supporting members (unshown) at the opposite ends. At one axial end of the photosensitive drum  1  (longitudinal end of the cartridge  7 ), there is provided a coupling member  25  mounted thereto as shown in  FIG. 3 . A driving force is transmitted from a driving motor (unshown) to the coupling member  25  through a main assembly coupling (unshown). As shown in  FIG. 2 , the photosensitive drum  1  is rotated in the counterclockwise direction as indicated by arrow D 1 . 
   In this embodiment, a contact charging type charging means  2  is used. The charging means  2  is in the form of an electroconductive roller, which is contacted to the peripheral surface of the photosensitive drum  1 . The roller  2  is supplied with a charging bias voltage. By this, the peripheral surface of the photosensitive drum  1  is uniformly charged. In this embodiment, the use is made of reverse development, and therefore, the peripheral surface of the photosensitive drum  1  is charged to a negative polarity. 
   The scanner unit ( 3   a ,  3   b ,  3   c ,  3   d ) is disposed substantially at the same levels as the associated photosensitive drum  1  and is extended substantially in a horizontal direction. The image light produced by a laser diode (unshown) correspondingly to an image signal is projected onto one of polygonal mirrors  9 ( a )– 9 ( d ), which are rotated at a high speed by a scanner motor (unshown). The image light reflected by the polygonal mirror is projected on the surface of the photosensitive drum  1  which has been electrically charged, through one of imaging lenses ( 10   a ,  10   b ,  10   c ,  10   d ). By the imagewise exposure of the photosensitive drum to the image light, an electrostatic latent image is formed in accordance with the image signal. 
   As shown in  FIG. 2 , the developing units  4  ( 4   a ,  4   b ,  4   c ,  4   d ) contain yellow color, magenta color, cyan color and black color developers (toner particles) in respective toner containers. The toner is supplied to an associated toner supplying roller  43  by a toner feeding mechanism  42  provided in the toner accommodating container  46 . The toner supplying roller  43  rotates in the clockwise direction (arrow D 3  direction) in the figure to supply the toner to the developing roller  40 , which effects the development of the photosensitive drum  1 . The toner supplying roller  43  removes the toner from the developing roller  40  after the development. Then, the toner supplied to the developing roller  40  is applied on the outer surface of the developing roller  40  which is rotating in the clockwise direction in the figure, by a developing blade  44  press-contacted to the outer surface of the developing roller  40 . The developing roller  40  is supplied with a developing bias voltage to develop the latent image on the photosensitive drum  1  into a toner image. The rotational axis of the developing roller  40  is parallel with the axis of the photosensitive drum  1 . 
   On the other hand, as shown in  FIG. 1 , the image forming apparatus  100  includes an electrostatic transfer belt  11  which makes a circulation movement by all of the photosensitive drums  1   a – 1   d . The transfer belt  11  is an electrostatic conveyer belt made of resin film, a multi-layer film having a rubber base layer and a resin material layer thereon. While the belt  11  circulates, it electrostatically attracts the recording material S on the outer surface at the left side in  FIG. 1  and contacts the recording material S to the photosensitive drum  1 . The recording material S is fed to the image transfer station by the transfer belt  11 , where the toner image is transferred from the photosensitive drum  1  onto the recording material S. 
   Transfer rollers ( 12   a ,  12   b ,  12   c ,  12   d ) are disposed in the electrostatic transfer belt  11  which is an endless belt, and are contacted to the inside of the electrostatic transfer belt  11  at a position opposed to their associated photosensitive drum ( 1   a ,  1   b ,  1   c ,  1   d ). The transfer rollers apply charge of a positive polarity to the recording material S through the electrostatic transfer belt  11 . By this, the toner image is transferred from the photosensitive drum  1  onto the recording material S. 
   A feeding portion  16  functions to feed the recording material S to such an image forming station. Here, a cassette  17  accommodates a plurality of recording materials S. During the image forming operation, a paper feeding roller  18  (crescent roller) and registration roller  19  are rotated in accordance with the image forming operation. By this, the recording material S in the cassette  17  is fed out one by one. A leading end of the recording material S is abutted to the registration roller  19 , and temporarily stops to form a loop. The recording material S is fed to the electrostatic transfer belt  11  in timed relation with the rotation of the electrostatic transfer belt  11  and the image writing position by the registration roller  19 . 
   The fixing portion  20  functions to fix the toner images of different colors having been transferred onto the recording material S. The fixing portion  20  includes a rotatable heating roller  21   a  and a pressing roller  21   b  press-contacted thereto to apply heat and pressure to the recording material S. The recording material S having the toner image transferred from the photosensitive drum  1 , is fed by the pressing roller  21   b  in the nip of the fixing portion  20 , provided by the heating and pressing rollers  21   a  and  21   b . In the fixing portion  20 , the recording material is pressed and heated by the pressing roller  21   b  and the heating roller  21   a . By doing so, the toner image comprising toner particles having a plurality of colors is fixed on the surface of the recording material S. 
   The image forming operation is as follows. 
   The cartridges  7   a ,  7   b ,  7   c ,  7   d  are sequentially rotated in timed relation with the image forming operation. By this, the photosensitive drums ( 1   a ,  1   b ,  1   c ,  1   d ) are rotated in response thereto. The scanner unit is sequentially actuated corresponding to the cartridges. By the actuation, the charging roller  2  applies uniform charge on the peripheral surface of the photosensitive drum  1 . The scanner unit exposes the peripheral surface of the photosensitive drum  1  in accordance with image signal to form an electrostatic latent image on the peripheral surface of the photosensitive drum  1 . The developing roller  40  in the developing unit  4  transfers the toner to a low potential portion of the electrostatic latent image, thus forming a toner image on the peripheral surface of the photosensitive drum  1 . 
   As described in the foregoing, the toner image is sequentially transferred from the photosensitive drums  1  onto the recording material S by the electric fields formed between the photosensitive drums  1  and the transfer rollers. 
   The recording material S onto which the toner image has been transferred, is separated from electrostatic transfer belt  11  by the belt driving roller  13  using the curvature of the belt driving roller  13 , and is fed into the fixing portion  20 . The recording material S is subjected to the heat fixing operation of the fixing portion  20  so that the toner image is fixed, and then is discharged from a discharging portion  24  onto the tray  28  with the image side facing down. 
   (Structure of Process Cartridge) 
   Referring to  FIGS. 2 and 3 , a description will be provided in detail as to the process cartridge (cartridge) according to an embodiment of the present invention.  FIGS. 2 and 3  are a main section and a perspective view of the cartridge  7  accommodating the developer. The cartridges  7   a ,  7   b ,  7   c ,  7   d  for yellow color, magenta color, cyan color and black color have substantially or exactly the same structure. The cartridge  7  comprises a cleaner unit  50  containing the electrophotographic photosensitive drum  1 , the charging means and the cleaning means, and a developing unit  4  containing the developing roller for developing the electrostatic latent image on the photosensitive drum  1 . 
   In the cleaner unit  50 , the photosensitive drum  1  is rotatably mounted to the cleaning frame  51  (first frame) through bearing members  31  (first cartridge positioning portion). The photosensitive drum  1  has a photosensitive layer on the outer surface thereof. Around the photosensitive drum  1 , there are provided a charging means  2  for electrically charging the photosensitive layer to a uniform potential, a cleaning blade  60  for removing the toner remaining on the photosensitive drum  1  after the image transfer, and a flexible sheet. The charging means  2 , the cleaning blade  60  and the flexible sheet are supported by the cleaning frame  51 . The toner removed from the surface of the photosensitive drum  1  by the cleaning blade  60  is sequentially fed to a residual toner chamber  55  provided at a rear side of the cleaning frame  51 . 
   The developing unit  4  contains a developing roller  40  rotating with a small gap from the photosensitive drum  1  and a developing device frame  45  (second frame). The developing roller  40  is rotatable in the direction indicated by arrow D 2 . 
   The developing device frame  45  comprises an upper frame  45   a  and a lower frame member  45   b . The upper frame  45   a  and the lower frame member  45   b  are welded by ultrasonic welding to constitute a toner accommodating portion  46  for accommodating the toner. The developing roller  40  is rotatably supported by the developing device frame  45  through bearing members (unshown). 
   To the developing roller  40 , the toner supplying roller  43  and the developing blade  44  are contacted. The toner supplying roller  43  is rotatable in the direction indicated by arrow D 3 . In the toner accommodating container  46 , there is provided a toner feeding mechanism  42  for stirring and feeding the toner to the toner supplying roller  43 . 
   The developing unit  4 , as shown in FIG.  8 – FIG. 10 , is supported rotatably on the cleaner unit  50 . As shown in  FIG. 8 , one end of the developing device frame  45  is provided with an arm  45   a   1 . The arm  45   a   1  is provided with a hole  47   a  which functions as an engaging portion. The cleaning frame  51  of the cleaner unit  50  is also provided at one end with a hole  52   a . As shown in  FIG. 9 , a pin  49  (connecting member) having a circular section is penetrated through the holes  52   a ,  47   a ,  52   b  in this order, so that cleaning frame  51  and the developing device frame  45  are rotatably connected with each other. 
   Similarly, as shown in  FIGS. 14   a ,  14   b , at the other side of the cartridge  7 , a pin  49  is inserted through a hole  47   b  formed in other end of the developing device frame  45 , the holes  53   a ,  53   b  formed in the other end of the cleaning frame  51 . The developing unit  4  is normally urged by a pressing spring  22  so that the developing roller  40  is contacted to the photosensitive drum  1 . 
   During the developing operation, the toner accommodated in the toner accommodating container  46  is fed to the toner supplying roller  43  by the toner stirring mechanism  42 . The toner supplying roller  43  rotating in the direction indicated by an arrow D 3  is in rubbing relation with the developing roller  40  rotating in the direction indicated by arrow D 2 , so that toner is supplied to the developing roller  40  to deposit the toner on the peripheral surface of the developing roller  40 . The toner deposited and carried on the peripheral surface of the developing roller  40  is moved to the developing blade  44  with the rotation of the developing roller  40 . The developing blade  44  regulates the toner to form a predetermined thin toner layer while applying a desired amount of the charge to the toner. The thin layer of the toner thus provided on the developing roller  40  is fed to the developing zone where the developing roller  40  is close to the photosensitive drum  1 . The toner is deposited onto the electrostatic latent image formed on the surface of the photosensitive drum  1  by a developing bias applied to the developing roller  40  from a voltage source (unshown) in the developing zone, thus forming a developed image. 
   The toner not used for the development and remaining on the surface of the developing roller  40  is returned into the developing device with the rotation of the developing roller  40 . The toner is removed from the developing roller  40  at the sliding portion which the developing roller  40  is in sliding relation with the toner supplying roller  43  and is collected. The collected toner is stirred and mixed with the other toner by the toner stirring mechanism. 
   (Mounting and Demounting of the Process Cartridge Relative to the Main Assembly of the Image Forming Apparatus) 
   Referring to  FIG. 4 , a description will be provided as to the mounting and demounting method of the cartridge  7  relative to the main assembly  100  of the image forming apparatus. As shown in  FIG. 4 , the main assembly  100  of the image forming apparatus is provided with a front door  101  which is rotatable relative to the main assembly  100 . On the front door  101 , the electrostatic transferring means  5  is rotatably supported. When the front door  101  is opening, the cartridge  7  is capable of being mounted and demounted relative to the main assembly  100  of the image forming apparatus. Adjacent the photosensitive drum supporting portion at the respective ends of the cartridge  7 , there are provided grip members  90  which facilitate the mounting and demounting of the cartridge  7 . The cartridge  7  is mounted to the main assembly  100  of the image forming apparatus while engaging a guide portion (unshown) of the cartridge  7  on a guiding rail portion (unshown) provided in the main assembly  100  of the image forming apparatus. 
   (Positioning of Process Cartridge) 
   As shown in  FIGS. 5–7 , the driving input gear  76  provided in the developing unit is engaged with the driving gear  70  provided in the main assembly  100  of the image forming apparatus to transmit the driving force. The driving force received by the driving input gear  76  is transmitted to the developing roller  40 , the toner supplying roller  43 , and the toner feeding mechanism  42  in the developing unit  4 . By doing so, the developing roller  40 , the toner supplying roller  43  and the toner feeding mechanism  42  are rotated. Referring to  FIGS. 6 , and  7 , a description will be provided as to the driving force transmission path. The driving input gear  76  for receiving the rotational driving force from the driving gear  70  has two gears  76   a  and  76   b  which are coaxial. The driving input gear  76  is rotatably supported on a supporting shaft  26 . One end of the supporting shaft  26  is supported on the developing device frame  45 . The other end of the supporting shaft  26  is supported on the supporting portion  45   a   2 . Furthermore, the developing device frame  45  supports by a supporting shaft  27  an idler gear  82  which receives the driving force from the driving input gear  76 . The idler gear  82  has two coaxial gears  82   a  and  82   b . The gear  76   b  is in meshing engagement with a toner feeding mechanism gear  81  for rotating the toner feeding mechanism  42  to transmit the rotational driving force. The gear  76   a  is in meshing engagement with the gear  82   a  to transmit the rotational driving force to the idler gear  82 . In addition, the gear  82   b  is engaged with a toner supplying roller gear  79  for rotating the toner supplying roller  43  and a developing roller gear  78  for rotating the developing roller  40  to transmit the driving force to the developing roller  40 . 
   Thus, the rotational driving force from the driving gear  70  rotates the developing roller  40 , the toner supplying roller  43  and the toner feeding mechanism  42 , and the torque required for rotating them all is quite large. Therefore, as shown in  FIG. 11 , the input gear  76  receives a force Y corresponding to the torque at the engaging portion K between the driving gear  70  and the driving input gear  76 . 
   Referring to  FIGS. 5 , and  10 , a description will be provided as to the structure by which the cleaner unit  50  supporting the developing unit  4  which receives the force Y is supported by the main assembly  100  of the image forming apparatus. The cleaner unit  50  rotatably supporting the developing unit  4  is abutted against a supporting portion  71  of the main assembly  100  with a support force X from the main assembly  100  of the image forming apparatus at the outer periphery of the bearing member  31  (first positioning portion) which functions to rotatably support the photosensitive drum  1 . The structure is the same at the other end with respect to axial direction of the photosensitive drum  1 . With this structure, the cartridge  7  can be correctly positioned with respect to a direction crossing with longitudinal direction of the cartridge  7 . As shown in  FIGS. 5 and 11 , the cartridge  7  receives the force Y at the driving input gear  76  by the rotational driving force from the driving gear  70 , as described hereinbefore. Therefore, the cartridge  7  receives a force tending to rotate about the bearing member  31 , and a positioning portion  51   a  of the cleaning frame  51  is abutted to a supporting portion  72  provided in the main assembly  100  of the image forming apparatus. In other words, the rotation of the cartridge  7  about the bearing member  31  is limited by the second supporting portion  72 . By doing so, the cartridge  7  is positioned in place relative to the main assembly  100  of the apparatus. 
     FIG. 15  ( a ) is a detailed illustration of the supporting portion  72  and the second cartridge positioning portion  51   a  as seen in the longitudinal direction of the cartridge  7  (a direction of the axis of the photosensitive drum  1 ).  FIG. 15  ( b ) is a detailed illustration of the second supporting portion  72  and the cartridge positioning portion  51   a  as seen in a direction perpendicular to the longitudinal direction of the cartridge  7  (the direction of the axis of the photosensitive drum  1 ). The supporting portion  72  has a flat surface configuration to provides a reference surface HP. The cartridge  7  is positioned by abutting the supporting portion  72  at the cartridge positioning portion  51   a.    
   (Positional Relation Between the Driving Input Gear and Positioning Portion) 
     FIGS. 10 , and  11  show a positional relation between driving input gear  76  and the positioning portion  51   a .  FIG. 10  is a view as seen in the direction V 1  in  FIG. 11 . The direction V 1  is parallel with the reference surface HP. As will be understood from these figures, when the cartridge  7  is seen in the direction V 1 , the positioning portion  51   a  is included in an engagement width (engagement range) Z between the driving input gear  76  and the driving gear  70  with respect to the direction perpendicular to the longitudinal direction of the cartridge  7 . Then, the relation between the positioning portion  51   a  and the force Y is as follows. As shown in  FIG. 11 , the force Y is expressed as a vector having a starting point at the engaging portion K between the driving input gear  76  and the driving gear  70  and having an orientation which is upward when the cartridge  7  is mounted to the main assembly  100  of the image forming apparatus. An extension line ELI of the force Y intersects the reference surface HP at point P 1 . In the longitudinal direction of the cartridge  7 , the positional relation of the force Y and the positioning portion  51   a  is as shown in  FIG. 10 . The force Y is a vector having a starting point at a center of the engagement range Z (a point Z/2 away from the end of the driving input gear  76 ) between the driving input gear  76  and the driving gear  70 . An extension line ELI of the force Y is at such a position overlapping with the positioning portion  51   a  with respect to the direction perpendicular to the longitudinal direction of the cartridge  7  as seen in the direction V 1 . 
   In other words, the positional relation between the driving input gear  76  and the positioning portion  51   a  is as follows. As shown in  FIGS. 10 ,  11 , the engagement range Z in the longitudinal direction is seen in a direction which is perpendicular to the longitudinal direction and which passes through the second cartridge positioning portion  51   a . Then, engagement range Z is at a position overlapping with the second cartridge positioning portion  51   a.    
   Further, the positional relation is described as follows. The longitudinal engagement range Z shown in  FIGS. 10 and 11  is projected on the axis  76   c  of the driving input gear  76 . When the projected range (projection range) is seen in a direction (unshown) which is perpendicular to the longitudinal direction and which passes through the cartridge positioning portion  51   a , the projection range overlaps the cartridge positioning portion  51   a.    
   Furthermore, the driving input gear  76 , as seen in the direction V 1 , overlaps at least a part of the positioning portion  51   a , with respect to the longitudinal direction of the cartridge  7 . 
   With this structure, even when the cartridge  7  receives the rotational driving force at the driving gear  70 , the cleaning frame  51  is not subjected to a moment about the positioning portion  51   a , as shown in  FIG. 10 . Therefore, a deformation of the cleaning frame  51  is suppressed, so that the cartridge  7  can be properly positioned relative to the main assembly  100  of the apparatus. Thus, the deformation of the developing device frame  45  supported rotatably to the cleaning frame  51  can be suppressed. 
   In this manner, the positioning accuracies of the developing roller  40  and the toner supplying roller  43  relative to the photosensitive drum  1  is improved. This is effective to improve the image quality of the image provided by the apparatus. In addition, the positioning accuracy of the cleaning blade  60  supported on the cleaning frame  51  relative to the photosensitive drum  1  is improved, so that the removal property of the residual toner from the surface of the photosensitive drum  1  improved. 
   In this embodiment, as described hereinbefore, the cartridge positioning portion  51   a  is included in the engagement range Z with respect to the direction perpendicular to the longitudinal direction of the cartridge  7 . However, only a part of the positioning portion  51   a  may overlap the engagement width Z. On the contrary, the width of the positioning portion  51   a  may be larger than the engagement width Z. 
   In the case that driving input gear  76  is a helical gear, the force Y is inclined correspondingly to the angle of twist of the gear teeth. However, when considering the deformation of the cleaning frame  51  by the moment about the positioning portion  51   a , it will suffice if the component in the direction perpendicular to the supporting portion  72  (reference surface HP) is considered. That is, it is sufficient that component in the direction of the force Y shown  FIG. 10  is considered. 
   The positioning portion  51   a  is disposed above the driving input gear  76  when the cartridge  7  is set in place in the main assembly  100  of the apparatus. With this structure, the driving gear  70  and the second supporting portion  72  can be at different positions in the main assembly  100  of the apparatus, the main assembly  100  of the apparatus can be downsized, and the cartridge  7  can be downsized. 
   Moreover, the positioning portion  51   a  is provided by the peripheral surface of a cylindrical projection which is coaxial with the supporting hole supporting the pin  49 . The projected portion is projected from the cleaning frame  51 . The pin  49  is supported inside the projected portion. With this feature, the main assembly  100  of the apparatus can be downsized, and the cartridge  7  can be downsized. 
   The second cartridge positioning portion  51   a  may be provided only at one end side of the cartridge  7  with respect to the longitudinal direction. With the above-described positional relation between the engagement range Z and the cartridge positioning portion  51   a , the deformation of the cleaning frame  51  can be suppressed, and the cartridge  7  can be correctly positioned to the main assembly  100  of the apparatus, even if the cartridge positioning portion is not provided at the other longitudinal end. This eliminates the necessity of the space for providing the positioning structure at the other side, so that the main assembly  100  of the apparatus and the cartridge  7  can be downsized. This advantage is significant particularly when the cartridges  7  are arranged substantially in the vertical direction in the main assembly of the multi-color image forming apparatus  100  as in this embodiment. 
   (Checking) 
     FIG. 13  illustrates a checking method for the deformation of the cartridge  7 . For example, a deformation amount of the cleaning frame at a position predetermined distance L 1  away from an end of the driving gear  70  (reference point), which is displaced from a reference surface HP at the point P 2 , or a deformation amount of the developing device frame (a displacement from the reference plane HP at point P 3 ), are measured. More particularly, the deformations are compared with deformations which are measured when the supporting portion  172  is at a position L 2  away from the point ELI. By doing so, the effect of the embodiment can be confirmed. The measurements may be carried out using a dial gauge. 
   Second Embodiment 
   The mounting structure of the developing device is frame  45  relative to the cleaning frame  51  may be as shown in  FIG. 12 . Here, a position, in the longitudinal direction of the cartridge  7 , of an arm  45   a   1  having the hole  52   a  for penetration of the pin  47  is seen in the direction which is perpendicular to the longitudinal direction of the cartridge  7  and which passes through the cartridge positioning portion  51   a  (direction V 3  in  FIGS. 11 and 12 ). Then, the arm  45   a   1  which is an engaging portion relative to the pin  47  is at a position overlapping with the second cartridge positioning portion  51   a.    
   When they are seen in the direction V 1  in  FIG. 11 , the structure is as follows. Namely, the position of the arm  45   a   1  having the hole  52   a  for penetration of the pin  47  overlaps with an extension line ELI of the force Y received by the driving input gear  76  with respect to the longitudinal direction of the cartridge  7 . Similarly, to the structure in  FIG. 10 , an extension ELI of the force Y also overlaps positioning portion  51   a  with respect to the longitudinal direction, as seen in the direction V 1 . 
   With this structure, the cleaning frame  51  is not subjected to a moment about positioning portion  51   a . The deformation of the developing device frame on the cleaning frame  51  can be suppressed, and therefore, the positioning accuracies of the developing roller  40  and the toner supplying roller  43  relative to the photosensitive drum  1  can be improved, so that image quality can be improved. The positioning accuracy of the cleaning blade  60  supported on the direction relative to the photosensitive drum  1  can be improved, so that the removal property of the residual toner from the photosensitive drum  1  can be improved, too. In addition, the cartridge  7  and the main assembly  100  of the apparatus can be downsized. 
   In the first and second embodiments, the material of the cleaning frame  51  and the developing device frame  45  is a styrene material, such as high impact polystyrene (HIPS), acrylic nytril butadiene polymer (ABS) or the like. From the standpoint of moldability and the cost, the thicknesses of the cleaning frame  51  and the developing device frame  45  are small. However, in order to assure the mechanical strength of the frame, a certain degree of thickness (approx. 2 mm) is required even when such a material is used. According to the present invention, the thickness can be reduced (for example, to degree 1.5 mm). In some cases, in order to reinforce the frame, a metal plate has been used at an upper part of the cartridge. However, according to the present invention, there is no need to use such a metal plate. This accomplishes cost reduction, downsizing, lightening, and better assembling properties. 
   As described in the foregoing, according to the present invention, the deformation of the developing cartridge or the process cartridge is suppressed when the rotational driving force is transmitted from the main assembly of the electrophotographic image forming apparatus. The positional accuracy of the developing roller is improved when the rotational driving force is transmitted from the main assembly of the electrophotographic image forming apparatus in the developing cartridge, the process cartridge and the electrophotographic image forming apparatus. In addition, the developing cartridge, the process cartridge and the electrophotographic image forming apparatus can be downsized. 
   While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims. 
   This application claims priority from Japanese Patent Application No. 293846/2004 filed Oct. 6, 2004, which is hereby incorporated by reference.