Abstract:
A process cartridge is detachably mountable to an electrophotographic image forming apparatus that includes a drum unit and a developing unit. The cartridge also includes a charging roller for charging a surface of a photosensitive drum by being urged and contacted to the photosensitive drum. The cartridge further includes a link engaged with an end of a rotation shaft of the charging roller, and a locking member locked with the link in a state that the charging roller is spaced from the drum for holding a spaced state of the charging roller from the drum. When the process cartridge is mounted to the apparatus, a space releasing member of the developing unit is moved by a driving force from a gear train through a connecting member, and the space releasing member releases locking between the link and the locking member, thereby ceasing the spaced state of the charging roller.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a process cartridge having a development unit and a drum unit. It also relates to an electrophotographic image forming apparatus in which a process cartridge having a development unit and a drum unit is removably mountable. 
     There have been known a process cartridge which has a development unit and a drum unit and is removably mountable in the main assembly of an electrophotographic image forming apparatus (which may be referred to simply as image forming apparatus). The development unit has a development roller, whereas the drum unit has a photosensitive drum, a charge roller, and cleaning member. The two units are connected to each other. Since a process cartridge of this type integrally holds the above described multiple components, it makes it possible for a user to maintain an image forming apparatus by himself or herself, that is, without relying on a service person. Thus, it can drastically improve an image forming apparatus in operational efficiency. 
     There has been also known a process cartridge which keeps its charge roller separated from the peripheral surface of its photosensitive drum when it is not being used for image formation. If a charge roller is kept in contact with the peripheral surface of a photosensitive drum for a substantial length of time, it is possible that the charge roller will be made to deform by the contact pressure between the charge roller and photosensitive drum. Thus, the deformation of a charge roller can be prevented by keeping the charge roller separated from the peripheral surface of a photosensitive drum when the charge roller is not being used for image formation. The deformation can also be prevented by reducing the contact pressure between the charge roller and the peripheral surface of the photosensitive drum. The technologies related to this subject are disclosed in U.S. Pat. Nos. 7,072,603 and 7,720,412. 
     However, process cartridges such as those disclosed in the abovementioned patents have the following problems. 
     In the case of the structure of the process cartridges disclosed in the abovementioned patents, if the process cartridge is subjected to vibrations and/or impacts, its charge roller sometimes comes into contact with the peripheral surface of the photosensitive drum with an unexpected timing. As for the means for preventing the occurrence of this problem, it is necessary to increase the process cartridge components in rigidity and/or to provide the process cartridge with additional components to improve the process cartridge in structure in order to ensure that the charge roller is kept separated from the peripheral surface of the photosensitive drum. However, these solutions are likely to invite the increase in the size, cost, etc., of a process cartridge. 
     SUMMARY OF THE INVENTION 
     Thus, the primary object of the present invention related to a process cartridge which is structured so that its charge roller is separable from the peripheral surface of its photosensitive drum is to provide a process cartridge which is simple in structure, and yet, is capable of reliably keeping the charge roller separated from the peripheral surface of the photosensitive drum when the charge roller is not being used for image formation. 
     According to an aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising: a drum unit including a photosensitive drum; a developing unit for developing an electrostatic latent image formed on said photosensitive drum, said drum unit and said developing unit being connected swingable relative to each other; a charging roller for charging a surface of said photosensitive drum by being urged and contacted to said photosensitive drum; a link engaged with an end of a rotation shaft of said charging roller; a locking member, locked with said link in a state that charging roller is spaced from said photosensitive drum, for holding a spaced state of said charging roller from said photosensitive drum; said developing unit including, 
     a gear train for transmitting an externally inputted driving force to a member provided in said developing unit: a space releasing member for contacting and moving said link to release said link from said locking member, thereby to cease the spaced state of said charging roller, said space releasing member being provided with a drive receiving portion; a connecting member including an input gear portion for receiving a driving force from said gear train, and a drive transmitting portion engageable with said drive receiving portion, wherein a play is provided between said drive receiving portion and said drive transmitting portion in a direction of movement of said drive transmitting portion, when said process cartridge is mounted to the main assembly of the apparatus and is operated, said space releasing member is moved by the driving force from said gear train through said connecting member, and said space releasing member releases locking between said link and said locking member, thereby ceasing the spaced state of said charging roller, wherein the play provides a movable distance of said space releasing member which is larger than a movement distance through which said space releasing member moves at the time when said developing unit is swung relative to said drum unit. 
     These and other objects, features, and advantages of the present invention will become more apparent upon 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 schematic side view of the charge roller releasing mechanism of the process cartridge in the preferred embodiment of the present invention, and shows the structure of the mechanism. 
         FIG. 2  is a schematic sectional view of the electrophotographic image forming apparatus in the preferred embodiments of the present invention, and shows the general structure of the apparatus. 
         FIG. 3  is a schematic sectional view of the process cartridge in the preferred embodiment of the present invention. 
         FIG. 4  is a perspective view of the image forming apparatus and process cartridges in the preferred embodiment of the present invention when one of the process cartridges is being inserted into the main assembly of the image forming apparatus and others are already in the main assembly. 
         FIG. 5  is a plan view of the process cartridge in the preferred embodiment, as seen from the side from which the driving force from the main assembly of the image forming apparatus is inputted into the process cartridge. 
         FIG. 6  is a plan view of the process cartridge in the preferred embodiment, as seen from the opposite side from the side from which cartridge is seen in  FIG. 5 . 
         FIG. 7  is a perspective view of the process cartridge in the preferred embodiment. 
         FIG. 8  is a plan view of the development unit driving force input portion of the process cartridge in the preferred embodiment. 
         FIG. 9  also is a plan view of the development unit driving force input portion of the process cartridge in the preferred embodiment. 
         FIG. 10  is a schematic plan view of the development roller separating mechanism of one (first) of the lengthwise end portions of the process cartridge in the preferred embodiment, when the development roller is kept separated from the photosensitive drum. 
         FIG. 11  is a schematic plan view of the development roller separating mechanism of one (first) of the lengthwise end portions of the process cartridge in the preferred embodiment, when the development roller is in contact with the photosensitive drum. 
         FIG. 12  is a schematic plan view of the development roller separating mechanism of the other (second) lengthwise end portion of the process cartridge in the preferred embodiment, when the development roller is kept separated from the photosensitive drum. 
         FIG. 13  is a perspective view of the development roller separating mechanism of the other (second) lengthwise end portion of the process cartridge in the preferred embodiment, when the development roller is kept separated from the photosensitive drum. 
         FIG. 14  is a schematic plan view of the development roller separating mechanism of the other (second) lengthwise end portion of the process cartridge in the preferred embodiment, when the development roller is in contact with the photosensitive drum. 
         FIG. 15  is a perspective view of the development roller separating mechanism of the other (second) lengthwise end portion of the process cartridge in the preferred embodiment, when the development roller is in contact with the photosensitive drum. 
         FIG. 16  is a schematic drawing of the mechanism which is located at the other (second) lengthwise end portion of the process cartridge (drum unit) to keep the charge roller separated from the photosensitive drum, in the preferred embodiment, and shows the structure of the mechanism. 
         FIG. 17  is a plan view of the development unit of the process cartridge in the preferred embodiment, as seen from the other (second) lengthwise end of the process cartridge, when the charge roller is kept separated from the photosensitive drum, and shows the structure of the other (second) lengthwise end portion of the development unit. 
         FIG. 18  is a plan view of the development unit of the process cartridge in the preferred embodiment, as seen from the other (second) lengthwise end of the process cartridge, when the charge roller is in contact with the photosensitive drum, and shows the structure of the other (second) lengthwise end of the development unit. 
         FIG. 19  is a perspective view of the charge roller releasing mechanism of the process cartridge in the preferred embodiment, and shows the structure of the mechanism. 
         FIG. 20  is a plan view of the charge roller releasing mechanism and its adjacencies of the process cartridge in the preferred embodiment, when the charge roller is kept separated from the photosensitive drum, and shows the structure of the mechanism. 
         FIG. 21  is a plan view of the charge roller releasing mechanism and its adjacencies of the process cartridge in the preferred embodiment, when the charge roller is in contact with the photosensitive drum, and shows the structure of the mechanism. 
         FIG. 22  is a plan view of the charge roller releasing mechanism of the process cartridge in the preferred embodiment, and shows the structure of the mechanism. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, one of the preferred embodiments of the present invention is illustratively described in detail with reference to the appended drawing. Incidentally, the measurements, materials, and shapes of the structural components, and the positional relationship among the structural components, in the following embodiment of the present invention, are not intended to limit the present invention in scope, unless specifically noted. 
     Embodiment 1 
     &lt;1: General Structure of Image Forming Apparatus&gt; 
     First, referring to  FIGS. 2 and 4 , the electrophotographic image forming apparatus which is compatible with the process cartridge  7  (which here after will be referred to simply as cartridge  7 ) in this embodiment of the present invention is described about its general structure. The image forming apparatus in this embodiment is a full-color laser beam printer, which uses an electrophotographic image forming method. 
     The image forming apparatus  100  has four cartridge chambers  22  ( 22   a - 22   d ) into which four cartridges  7  ( 7   a - 7   d ) are mountable, one for one. The four cartridge chambers  22  are positioned so that they are parallel to each other and align at an angle relative to the horizontal direction ( FIG. 4 ). As for the method for mounting the cartridges  7  into the corresponding cartridge chambers  22 , first, a door  21  hinged at the bottom is to be opened to expose the cartridge chambers  22 . Then, the cartridges  7  are to be inserted (direction indicated by arrow mark F) into the corresponding cartridge chambers  22  in such a manner that each cartridge  7  is kept in contact with the top guide portion  80  ( 80   a - 80   d ) and bottom guide portions  81  ( 81   a - 81   d ) of the corresponding cartridge chamber  22 . Thus, the cartridges  7  can be precisely positioned in the image forming apparatus  100 . 
     Each of the cartridges  7  ( 7   a - 7   d ) is provided with an electrophotographic photosensitive drum  1  ( 1   a - 1   d ). The electrophotographic photosensitive drum  1  (which hereafter will be referred to simply as “photosensitive drum  1 ”) is rotated in the clockwise direction (indicated by arrow mark Q in  FIG. 2 ), by a photosensitive drum driving member (unshown). Each cartridge  7  has also the following means for processing the photosensitive drum  1 , which are sequentially arranged in the rotational direction of the photosensitive drum  1 . They are: a cleaning member  6  ( 6   a - 6   d ) which removes the developer remaining on the peripheral surface of the photosensitive drum  1  after the transfer of an image from the peripheral surface of the photosensitive drum  1 ; a charge roller  2  ( 2   a - 2   d ) which charges the peripheral surface of the photosensitive drum  1 ; and a development unit  4  ( 4   a - 4   d ) which develops an electrostatic latent image into a visible image, that is, an image formed of toner, by supplying the electrostatic latent image with toner. The cleaning member  6  and charge roller  2  are held by a drum unit  26  ( 26   a - 26   d ). Incidentally, the developer (which hereafter will be referred to as toner) used by the image forming apparatus  100  in this embodiment is such toner that is negative in inherent polarity. 
     The drum unit  26  and development unit  4  make up the cartridge  7  by being connected to each other. The cartridge  7  is structured so that it can be removably mountable in the apparatus main assembly  100   a  of the image forming apparatus  100  by a user. Incidentally, the “apparatus main assembly  100   a ” of the image forming apparatus  100  means the image forming apparatus  100  minus the cartridges  7 . 
     The apparatus main assembly  100   a  has: a scanner unit  3  which forms an electrostatic latent image on the peripheral surface of the photosensitive drum  1  by scanning the peripheral surface of the photosensitive drum  1  with a beam of laser light which it projects while modulating the beam based on the information from the image to be formed; and an intermediary transfer belt  5 , onto which the toner images on the photosensitive drums  1  are transferred. The intermediary transfer belt  5  is suspended and kept stretched by a drive roller  10  and a tension roller  11 , and is circularly movable in the direction indicated by an arrow mark in the drawing. The apparatus main assembly  100   a  has also first transfer rollers  12  ( 12   a - 12   d ) which are on the inward side of the loop which the intermediary transfer belt  5  forms. The transfer rollers  12  are positioned so that they oppose the photosensitive drums  1  ( 1   a - 1   d ) one for one. When a toner image on the peripheral surface of the photosensitive drum  1  is to be transferred onto the intermediary transfer belt  5 , transfer bias is applied to the first transfer roller  12  ( 12   a - 12   d ) by a bias applying means (unshown). 
     The photosensitive drums  1  rotate in the direction indicated by the arrow mark Q, while a toner image is formed on the peripheral surface of each photosensitive drum  1  and the intermediary transfer belt  5  is circularly moved in the direction indicated by an arrow mark R. Then, as positive bias is applied to the first transfer rollers  12 , the toner images formed on the photosensitive drums  1  one for one are sequentially transferred in layers (firs transfer) onto the intermediary transfer belt  5 . Then, the four monochromatic toner images, different in color, on the intermediary transfer belt  5  are moved to a second transfer portion  15  by the movement of the intermediary transfer belt  5 . 
     Meanwhile, a sheet S, which is recording means, is conveyed to the second transfer portion  15  in synchronism with the progression of the above described image forming operation, by a recording medium conveying means which comprises a sheet feeding apparatus  13 , a pair of registration rollers  17 , etc. The sheet feeding apparatus  13  has: a sheet feeder cassette  24  in which sheets S are stored; a sheet feeding roller which feeds the sheet S into the apparatus main assembly  100   a ; and a pair of sheet conveyance rollers  16  which convey the sheet S further into the apparatus main assembly  100   a . The sheet feeder cassette  24  can be pulled out of the apparatus main assembly  100   a  in the frontward direction of the apparatus main assembly  100   a  in  FIG. 2 . The sheets S in the sheet feeder cassette  24  are kept pressed upon the sheet feeding roller  8 . As the roller  8  is rotated, the sheets S are fed into the apparatus main assembly  100   a  while being separated one by one from the rest by a separation pad  9  (frictional separation method). 
     After being fed into the apparatus main assembly  100   a  by the sheet feeding apparatus  13 , each sheet S is conveyed to the second transfer portion  15  by the pair of registration rollers  17 . In the second transfer portion  15 , positive bias is applied to a second transfer roller  18 . Therefore, as the sheet S is conveyed through the second transfer portion  15 , the toner images on the intermediary transfer belt  5  are transferred (second transfer) onto the sheet S. 
     A fixing portion  14 , which is a fixing means, is what fixes the toner images (unfixed) on the sheet S to the sheet S by applying heat and pressure to the toner images on the sheet S. A fixation belt  14   a  is cylindrical, and is guided by a belt guiding member (unshown) which has a heat generating means, such as a heater, which is bonded to the belt guiding means. The fixation belt  14   a  and a pressure roller  14   b  form a fixation nip by being kept pressed upon each other so that a preset amount of contact pressure is maintained between the belt  14   a  and roller  14   b . It is through this nip that the sheet S, on which the unfixed toner images are present, is conveyed from the image forming portion. Then, as the sheet S is conveyed through the fixation nip, the unfixed toner images on the sheet S are fixed to the sheet S. After the fixation of the unfixed toner images to the sheet S, the sheet S is discharged into a delivery tray  20  by a pair of discharge rollers  19 . 
     The toner remaining on the intermediary transfer belt  5  after the second transfer, that is, the transfer of the toner images onto the sheet S, is removed by a transfer belt cleaning apparatus  23 . The removed toner is conveyed through a waste toner passage (unshown), and is recovered into a waste toner recovery container (unshown) which is in the rear portion of the apparatus main assembly  100   a.    
     &lt;2: Cartridge&gt; 
     Next, referring to  FIG. 3 , the cartridge  7  ( 7   a - 7   d ) in this embodiment is described.  FIG. 3  is a sectional view of the cartridge  7  at a plane perpendicular to the lengthwise direction of the cartridge  7 . There is toner t in the cartridge  7 . Incidentally, the cartridge  7   a  which contains yellow toner t, cartridge  7   b  which contains magenta toner t, cartridge  7   c  which contains magenta toner t, and cartridge  7   d  which contains black toner t are the same in structure. 
     As described before, the cartridge  7  is made up of two units, that is, the drum unit  23  which has the photosensitive drum  1 , charge roller  2 , and cleaning member  6  (photosensitive drum cleaning means), and the development unit  4  which has the development roller  25 . 
     A cleaning means frame  27  is a part of the frame of the drum unit  26 . It is the cleaning means frame  27  that the photosensitive drum  1  is rotatably attached with the presence of bearings between the drum shaft and frame  27 . The bearings are described later. Thus, the photosensitive drum  1  can be rotated in the direction indicated by an arrow mark X in  FIG. 3  by transmitting driving force to the drum unit  26  from a motor (unshown). The drum unit  26  has the charge roller  2  and cleaning member  6 , which are in the adjacencies of the peripheral surface of the photosensitive drum  1 , as described before. The drum unit  26  is structured so that as the toner remaining on the peripheral surface of the photosensitive drum  1  after the second transfer is removed by the cleaning member  6 , it falls into the residual toner storage chamber  27   a.    
     The charge roller bearings  28  are attached to the cleaning means frame  27 , and are movable in the direction indicated by an arrow mark D, the stem portion of which coincides with the straight line which connects the center of the charge roller  2  and the center of the photosensitive drum  1 . The shaft  2   j  of the charge roller  2  is rotatably borne by the charge roller bearings  28 . Further, each charge roller bearing  28  is kept pressed toward the photosensitive drum  1  by a charge roller pressing member  46 . Thus, the charge roller  2  remains under such pressure that works in the direction to cause the charge roller  2  to be placed in contact with the peripheral surface of the photosensitive drum  1 . 
     As for the development unit  4 , it has: the development roller  25  which rotates in the direction indicated by an arrow mark B, while remaining in contact with the photosensitive drum  1 ; and a developing means frame  31 , which is the primary frame of the development unit  4 . The development roller  25  is rotatably supported by the development unit frame  31 , with the presence of a pair of bearings which are attached to the lengthwise ends of the development unit frame  31 , one for one. The development unit  4  has also: a toner supply roller  34  which rotates in the direction indicated by an arrow mark C, while remaining in contact with the development roller  25 ; and a development blade  35  for regulating the amount by which toner is allowed to be laid on the peripheral surface of the development roller  25 . That is, the toner supply roller  34  and development blade  35  are in contact with the peripheral surface of the development roller  25 . Further, the development unit  4  has a toner conveying member  36 , which is for conveying the toner t to the toner supply roller  34  while stirring the toner t. The toner conveying member  36  is in the toner storage chamber  31   a  of the developing means frame  31 . 
     In the case of the cartridge  7  in this embodiment, the development unit  4  and drum unit  26  are connected to each other so that they can be rotationally moved relative to each other. More concretely, the bearings  32 R and  32 L are provided with holes  32 Rb and  23 Lb, and the shafts  37  ( 37 R and  37 L) are put through the holes  32 Rb and  32 Lb, respectively. Thus, the development unit  4  is rotationally movable relative to the cleaning means frame  27  of the drum unit  26 , about the shafts  37 . Further, the development unit  4  is under the pressure from compression springs  38  which are between the two units  26  and  4 . That is, the development unit  4  is connected to the drum unit  26  in such a manner that the development unit  4  is rotationally movable relative to the drum unit  26 , about the shafts  37 . Therefore, the development roller  25  can be placed in contact with, or separated from, the photosensitive drum  1 . More concretely, as an image forming operation is started, the development unit  4  rotationally moves in the direction indicated by an arrow mark A, about the shafts  37 , placing thereby the development roller  25  in contact with the photosensitive drum  1 , whereas as the image forming operation ends, the development unit  4  moves back into the position in which it keeps the development roller  25  separated from the photosensitive drum  1 . 
     Next, referring to  FIGS. 5-9 , the rotational driving force receiving portion of the development roller  25  is in connection to an Oldham&#39;s coupling  39 , which is a shaft connecting member. The component designated by a referential code  30  is a member for driving the photosensitive drum  1 . The Oldham&#39;s coupling  39  can transmit the driving force from the apparatus main assembly  100   a  to the development roller  25  while tolerating the misalignment between the axial line of the driving force transmitting member of the apparatus main assembly  100   a  and the axial line of the development roller  25 . That is, the Oldham&#39;s coupling is a member necessary for transmitting to the development roller  25  the driving force inputted into the cartridge  7  from outside of the cartridge  7 . Moreover, the Oldham&#39;s coupling can transmit the driving force from the apparatus main assembly  100   a  to the cartridge  7  not only when the development unit  4  is in the position in which the development roller  25  is in contact with the photosensitive drum  1  ( FIG. 8 ), but also, when the development unit  4  is in the position in which the development roller  25  is not in contact with the photosensitive drum  1  ( FIG. 9 ). 
     &lt;3: Operation for Separating Development Roller from Photosensitive Drum, or Placing Development Roller in Contact with Photosensitive Drum&gt; 
     The cartridge  7  has a pair of development roller separating members  40  and  41  for keeping the development roller  25  separated from the photosensitive drum  1  when the development roller  25  is not being used for image formation. Next, referring to  FIGS. 10-15 , the operation for separating and keep separated the development roller  25  from the photosensitive drum  1  with the use of the development roller separating members  40  and  41  is described. 
     As described above, the development unit  4  is connected with the drum unit  26  with the pair of shafts  37 , being therefore rotationally movable about the shafts  37  in the direction to place the development roller  25  in contact with the peripheral surface of the photosensitive drum, or to separate the development roller  25  from the photosensitive drum. Further, the compression springs  38  are between the development unit  4  and drum unit  26 . Thus, when there is no interference from the development roller separating members  40  and  41 , the development roller  25  is kept in contact with the peripheral surface of the photosensitive drum  1  by the resiliency of the compression springs  38 . Hereafter, the development roller separating member  40 , which will be at the rear of the apparatus main assembly  100   a  when the cartridge  7  is properly situated in the apparatus main assembly  100   a , may be referred to as the first development roller separating member, whereas the development roller separating member  41 , which will be at the front of the apparatus main assembly  100   a  when the cartridge  7  is properly situated in the apparatus main assembly  100   a , may be referred to as the second development roller separating member. Next, the operation for separating the development roller  25  from the photosensitive drum  1  with the use of the first and second development roller separating members  40  and  41  is described. 
     The first development roller separating member  40  is rotatably supported by its shaft  40   c  ( FIGS. 10 and 11 ) and the corresponding side wall of the development unit  4 , whereas the portion of the cleaning means frame  27 , which corresponds in position to the first development roller separating member  40 , is provided with a hole  27   b . When it is necessary to keep separated the lengthwise end of the development roller  25 , which corresponds in position to the first development roller separating member  40 , from the photosensitive drum  1 , the first development roller separating member  40  is rotationally moved about its shaft  43   c  so that the first development roller separating member  40  is put through the hole  27   b  of the cleaning means frame  27  and the surface  40   a  of the first development roller separating member  40  will be in the hole  27   b . The placement of the surface  40   a  of the first development roller separating member  40  in the hole  27   b  of the cleaning means frame  27  prevents the development unit  4  from being rotationally moved. Therefore, the development unit  4  is kept in the position, against the resiliency of the compression springs  37 , in which the development roller  25  is kept separated from the photosensitive drum  1 . Moreover, the first development roller separating member  40  is provided with a projection  40   d , which is kept engaged with the outward edge portion of the hole  27  by the resiliency of the first development roller separating member  40 , preventing thereby the problem that as the cartridge  7  is impacted or subjected to the like situation, the projection  40   d  comes out of the hole  27   b.    
     As for the second development roller separating member  41 , it is rotatably supported by the shaft  27   c , with which the lengthwise end of the cleaning means frame  27 , which corresponds in position to the second development roller separating member  41 , is provided, and about which the second development roller separating member  41  is rotationally movable ( FIGS. 12 and 14 ). When it is necessary to keep separated the lengthwise end of the development roller  25 , which corresponds in position to the second development roller separating member  41 , from the photosensitive drum  1 , the second development roller separating member  41  is rotationally moved so that its portion  41   a  rotates into the cleaning means frame  27  and engages with the development roller separation projection  31 , with which the lengthwise end of the developing means frame  31  of the development unit  4 , which corresponds in position to the second development roller separating member  41 , is provided. Thus, the lengthwise end of the development unit  4 , which corresponds in position to the second development roller separating member  41 , is prevented from moving (rotationally moving). Therefore, the development unit  4  is kept in the position, against the resiliency of the compression springs  38 , in which the development roller  25  is kept separated from the photosensitive drum  1 . Moreover, the cleaning means frame  27  is provided with a projection  27   d , which is kept engaged in the groove  41   c  of the second development roller separating member  41  by the resiliency of the cleaning means frame  26 , preventing thereby the problem that as the cartridge  7  is impacted or subjected to the like situation, the second development roller separating member  41  moves out of the position in which its keeps the development roller  25  separated from the photosensitive drum  1 . 
     It is as the cartridge  7  is inserted into the apparatus main assembly  100   a  that the development roller  25 , which has been kept separated from the photosensitive drum  1  by the first and second development roller separating members  40  and  41 , are allowed to come into contact with the photosensitive drum  1 . More concretely, as the cartridge  7  is inserted into the apparatus main assembly  100   a , the portions  40   b  and  41   b  of the development roller separating members  40  and  41 , respectively, are pushed by the disengagement projections (unshown) with which the apparatus main assembly  100   a  is provided. Therefore, the first and second development roller separating members  40  and  41  are rotationally moved, being thereby disengaged from the projections  27   b  and  40   d , respectively ( FIGS. 11 ,  14  and  15 ). 
     As described above, by rotationally moving the development unit  4  relative to the drum unit  26 , it is possible to put the development unit  4  in the state in which the development roller  25  is kept in contact with the peripheral surface of the photosensitive drum  1 , or the state in which the development roller  25  remains separated in contact with the photosensitive drum  1 . 
     &lt;4: Operation for Placing Charge Roller in Contact with Photosensitive Drum, or Separating Charge Roller from Photosensitive Drum&gt; 
     Next, the operation for placing the charge roller  2  in contact with, or separating the charge roller  2  from, the photosensitive drum  1  is described. In this embodiment, the cartridge  7  has a member  42  for keeping the charge roller  2  separated from the photosensitive drum  1  when the cartridge  7  is not being used for image formation. Hereafter, this member  42  will be referred to as the charge roller separating member  42 . The charge roller separating member  42  is a linkage, one end of which is in connection to one of the lengthwise ends of the shaft of the charge roller  2 . It keeps the charge roller  2  separated from the photosensitive drum  1  when the cartridge  7  is not being used for image formation. Therefore, the charge roller  2  can be kept separated from the photosensitive drum  1  at least when the cartridge  7  is not being used for image formation (for example, until cartridge  7  is used for the very first time after it is shipped from factory). Therefore, the charge roller  2  can be prevented from being deformed. Further, in the case of the cartridge  7  in this embodiment, even if the development unit  4  is made to oscillatory move by the vibrations, impacts, and/or the like, the problem that the charge roller  2  is placed in contact with the photosensitive drum  1  with an unintended timing is prevented by this structural feature of the cartridge  7 , which characterizes the present invention. Next, referring to  FIGS. 16-22 , this characteristic structural feature of the cartridge  7 , which is for keeping the charge roller  2  separated from the photosensitive drum  1 , is described. 
     The cartridge  7  is provided with a pair of the charge roller separating members  42 , that is, the members for keeping the charge roller  2  separated from the photosensitive drum  1 . The charge roller separating members  42  are fitted around the lengthwise end portions of the shaft  2   j  of the charge roller  2 , one for one, and are rotatably about the shaft  2   j  ( FIG. 16 ). The charge roller  2  can be separated from the photosensitive drum  1  by pulling the charge roller  2  away from the photosensitive drum  1 , with the use of the charge roller separating members  42 , against the force which keeps the charge roller  2  in contact with the photosensitive drum  1 . More concretely, when the charge roller  2  is kept separated from the photosensitive drum  1 , a pair of engagement claws  42   a  of the charge roller separating member  42  are in engagement with the claws  27   e , one for one, with which the lengthwise end portions of the cleaning means frame  26  are provided. Thus, the charge roller  2  remains separated from the photosensitive drum  1 . 
     Next, referring to  FIGS. 17-22 , the structural feature of the cartridge  7 , which is for preventing the charge roller  2  from being unintendedly placed in contact with the photosensitive drum  1 , and the structural feature of the cartridge  7 , which is for allowing the charge roller  2  to be kept in contact with the photosensitive drum  1  when the cartridge  7  is being used for image formation, are described. The charge roller separating member  42 , which is a linkage, has a hole  42   b  for releasing the charge roller  2 . Further, the development unit  4  has a drive train (gear train) for transmitting the driving force inputted from the apparatus main assembly  100   a  through the Oldham&#39;s coupling, to the toner supply roller  34  and toner conveying member  36 . The drive train is at the second lengthwise end of the development unit  4  ( FIGS. 17 and 18 , which show drive train when charge roller  2  is kept separated from photosensitive drum  1  and when charge roller  2  is allowed to remain in contact with photosensitive drum  1 , respectively). 
     The drive train comprises: a development roller gear  52  which rotates with the development roller  25 ; a first idler gear  53  which is driven by the development roller gear  52 ; a toner supply roller gear  54  which rotates with the toner supply roller  34  and is driven by the first idler gear  53  to drive the toner supply roller  34 ; a second idler gear  55  which is driven by the first idler gear  53  in order to transmit the driving force to the toner conveying gear  56  which drives the toner conveying member  36  in the toner storage chamber  31   a ; and an input gear portion  57   a  which is driven by the second idler gear  55  in order to transmit the force for allowing the charge roller  2  to be placed in contact with the photosensitive drum  1 . 
     Next, referring to  FIG. 19 , the input gear  57   a  in this embodiment is a segment gear, which is a part of a connector  57 . The connector  57  comprises a shaft portion  57   b , a driving force transmitting portion  57   c , and a disengagement preventing portion  57   d , in addition to the input gear portion  57   a . As shown in  FIG. 19 , the connector  57  connects the above-described drive train to the charge roller release lever  58 , which will be described later. 
     The connector  57  is put through the lengthwise end wall  31   b  of the developing means frame  31  of the development unit  4 , being thereby supported by the wall  31   b . The shaft portion  57   b  of the connector  57 , which is on the opposite side of the lengthwise end wall  31   b  from the input gear  57   a , supports the charge roller release lever  58 , which is the charge roller releasing member, in such a manner that the charge roller release lever  58  is allowed to be rotated by only a preset angle. The charge roller release lever  58  has: a charge roller releasing portion  58   a , a hole  58   b , and a driving force receiving portion  58   c  ( FIG. 19 ). The charge roller releasing portion  58   a  is a portion the charge roller release lever  58 , which projects from the end of the arm portion of the charge roller release lever  58 . The charge roller release lever  58  can be connected to the charge roller separating member  42  by inserting the charge roller releasing portion  58   a  into the hole  42   b  of the charge roller separating member  42 . 
     Next, the movement of the charge roller releasing portion  58   a  of the charge roller release lever  58  is described. As described above, the development unit  4  is rotationally movable relative to the drum unit  26  by a preset angle. The rotational movement of the development unit  4  causes the connector  57  to move with the drive train, and therefore, the charge roller releasing portion  58   a  of the charge roller release lever  58  supported by the connector  57  moves with the connector  57  ( FIG. 19 ). Referring to  FIG. 1 , a referential code L 1  stands for the maximum amount (distance) by which the charge roller releasing portion  58   a  of the charge roller release lever  58  is moved by this rotational movement of the development unit  4  (it is only development unit  4  that is moved; drive train and input gear  57   a  are yet to move). 
     As for the charge roller release lever  58 , it is rotationally movable relative to the connector  57  by a preset angle, which is determined by the amount of the driving force transmission play G (which hereafter is referred to simply as play G) between the driving force transmitting portion  57   c  of the connector  57  and the driving force receiving portion  58   c  of the charge roller release lever  58 , in terms of the direction of the rotational movement of the charge roller release lever  58 , as shown in  FIG. 22 . Because of the presence of this play G, the charge roller release lever  58  is rotationally movable about the shaft portion  57   a  of the connector  57 . A referential code L 2  in  FIG. 22  stands for the amount (distance) by the release portion  58   a  of the charge roller release lever  58  is moved by the rotational movement of the charge roller release lever  58 . 
     The primary characteristics of this embodiment of the present invention are that the cartridge  7  is structured so that the distance L 2  is larger than the distance L 1  ( FIG. 1 ), and also, that the cartridge  7  is structured to ensure that before the cartridge  7  is used for the very first time, the play G, the amount of which is no less than the distance L 2  (&gt;distance L 1 ), is provided between the driving force transmitting portion  58   c  of the connector  57  and the driving force receiving portion  58   c  of the charge roller release lever  58 . 
     Because the cartridge  7  is structured as described above, the rotational movement of the development unit  4  causes the charge roller releasing portion  58   a  of the charge roller release lever  58  to move only as far as it comes into contact with the inward surface of the hole  42   b  of the charge roller separating member  42 . Further, the charge roller release lever  58  rotationally moves relative to the connector  57 . In other words, the maximum distance L 1  by which the development unit  4  is rotationally moved is absorbed by the play G, which is equivalent to the distance L 2 . Therefore, when the development unit  4  is rotationally moved, the charge roller releasing portion  58   a  of the charge roller release lever  58  does not press on the inward surface of the hole  42   b  of the charge roller separating member  42 , and therefore, the charge roller separating member  42  is not moved. 
     Because of the above described structural features of the cartridge  7 , even if the development unit  4  is rocked by the impact or the like of the shock to which it is subjected before it begins to be used for the very first time after being mounted in the apparatus main assembly  100   a , and also, even after a user intentionally separates the development roller  25  from the photosensitive drum  1 , the charge roller  2  does not separate from the photosensitive drum  1 , unless a further step is taken. Further, even if the range in which the development unit  4  is rotationally movable relative to the drum unit  26  is substantial, and the stroke (moving distance L 1 ) of the charge roller releasing portion  58   a  of the charge roller release lever  58  is also substantial, this condition can be dealt with by adjusting the play G, which is equivalent to the moving distance L 2  of the charge roller releasing portion  53   a  (adjusting play G so that it can absorb moving distance L 1 ). Therefore, it is possible to reduce the cartridge  7  in the size of the hole  42   b  of the charge roller separating member  42 , which is turn makes it possible to reduce the cartridge  7  in size. 
     As for the release of the charge roller  2  for image formation, the charge roller  2  is released as the driving force is transmitted to the development unit  4 . More concretely, referring to  FIG. 18 , as the drive train of the development unit  4  is driven, the input gear  57   a  of the connector  57  rotates, whereby the charge roller release lever  58  is rotated in the direction indicated by the arrow mark Q. Thus, the charge roller releasing portion  58   a  presses the charge roller separating member  42  in the direction indicated by an arrow mark P ( FIGS. 18 and 21 ), whereby the claw  42   a  of the charge roller separating member  42  disengages from the charge roller separating claw  27   e  of the cleaning means frame  27 . Consequently, the charge roller  2  is placed in contact with the photosensitive drum  1  by the resiliency of the charge roller pressing member  46 . 
     As described above, there is the play G between the connector  57  and charge roller release lever  58  in terms of their rotational direction (moving direction). Therefore, it is after the connector  57  is rotated by an angle equivalent to the play G that the connector  57  begins to rotate the charge roller release lever  58 . Thus, the segment gear which is greater in angle than the sum of the angle equivalent to the amount of the stroke required of the charge roller releasing portion  58   a  of the charge roller release lever  58  to release the charge roller  2 , and the angle equivalent to the play G, is used as the input gear portion  57   a . Because of the engagement of this segment gear portion  57   a  and second idler gear  55 , the charge roller releasing portion  58   a  of the charge roller releasing lever  58  is made to stroke by only the distance necessary to release the charge roller  2 , and disengages the charge roller separating member  42 . Thereafter, the transmission of the driving force to the segment gear portion  57   a  is stopped to drive the charge roller separating member  42 . 
     As is evident from the description of the preferred embodiment of the present invention, as the cartridge  7 , which is in the state in which the charge roller  2  is kept separated from the photosensitive drum  1 , is mounted into the apparatus main assembly  100   a , the development unit  4  receives the driving force from the apparatus main assembly  100   a , whereby the charge roller  2  is released from the charge roller separating member  42 . Thus, the charge roller  2  is allowed to come into contact with the photosensitive drum  1 , readying thereby the cartridge  7  for image formation. Further, this embodiment of the present invention makes it possible to prevent the charge roller  2  from being unintendedly released. In other words, the present invention makes it possible to provide a process cartridge which can reliably keep its charge roller separated from the peripheral surface of its photosensitive drum, and yet, is simple in structure. 
     Incidentally, in the description of this embodiment given above, the mechanism for releasing the charge roller  2  was described with reference to only the second lengthwise end portion of the cartridge  7 . However, the first lengthwise end of the development unit  4  also is provided with a drive train, an input gear, a charge roller separating gear, etc., like those with which the second lengthwise end of the development unit  4  is provided, in order to release the charge roller  2 . Further, the mechanism for releasing the charge roller  2  at the first lengthwise end of the development unit  4  may be different from the mechanism for releasing the charge roller  2  at the second lengthwise end of the development unit  4 . 
     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 purposes of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Application No. 109175/2010 filed May 11, 2010 which is hereby incorporated by reference.