Abstract:
A rotatable coupling member is provided for transmitting driving forces to a first driver for driving a seal member for sealing an opening for discharging a developer from a developer accommodating container for accommodating the developer to unseal the opening and a second driver for driving a stirring member for stirring the developer in the developer accommodating container. The coupling member receives a driving force from a main assembly of an image forming apparatus to rotate in a first rotational direction to unseal the opening and to rotate in a second rotational direction, which opposite from the first rotational direction, to drive the second driver. The coupling member includes a first portion for substantially aligning a rotational center of the coupling member with a rotational center of a main assembly coupling member when the coupling member rotates in the first rotational direction, and a second portion for permitting deviation between the rotational center of the coupling member and the rotational center of the main assembly coupling member.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a coupling member and a process cartridge, which are usable for an image forming apparatus. It also relates to an image forming apparatus. 
     In this specification, the term “image forming apparatus” refers to an apparatus for forming an image on a recording medium, using a given image forming method, preferably, an electrophotographic image forming method. As for examples of such an image forming apparatus, there are electrophotographic copying machines, electrophotographic printers (laser beam printers, LED printers, and the like), facsimile apparatuses, word processors, and the like. 
     The term “process cartridge” refers to a cartridge that is removably installable in the main assembly of an image forming apparatus, and in which at least one means among a charging means, a developing means, and a cleaning means, and an image bearing member, are integrally disposed. 
     Conventionally, an image forming apparatus that employs an electrophotographic image formation process also employs a process cartridge system, according to which an electrophotographic photosensitive member as an image bearing member, and one or a plurality of processing means that act on the electrophotographic photosensitive member, are integrated into the form of a cartridge, which is removably installable in the main assembly of an image forming apparatus. Also according to this process cartridge system, an image forming apparatus can be maintained by a user alone, without relying on a service person, drastically improving operational efficiency. Therefore, the process cartridge system has been widely used in the image-forming-apparatus field. 
     A process cartridge such as the one described above comprises one or a plurality of processing means. One of such processing means is a developing means, which integrally comprises a developer storage container (toner container) in which toner is stored, and a developing means frame for supporting a developing member. Until a process cartridge is put to use for the first time, the passage between the toner container and developing means frame remains sealed with a sealing member (toner seal). This sealing member is torn open when a process cartridge is put to use for the first time. 
     It is common knowledge that some process cartridges or electrophotographic image forming apparatuses (hereinafter, “image forming apparatus”), are provided with a driving force transmitting means for receiving the driving force from the main assembly of an image forming apparatus to automatically wind up the sealing member to tear open it. 
     The sealing member winding driving force transmitting means of a conventional image forming apparatus, process cartridge, or toner container, is structured so that as the winding of the sealing member ends, it must stop transmitting the driving force, or it shuts down. Therefore, an apparatus main assembly, process cartridge, or toner container, must be provided with a driving force transmitting means dedicated to the winding of a sealing member. Further, in many image forming apparatus main assemblies, a toner seal winding unit and a toner stirring unit are simultaneously driven. 
     Such an arrangement complicates the driving means on the apparatus main assembly side. Further, the simultaneous driving of the stirring unit and toner seal winding unit leads to increase in power consumption. 
     The present invention is one of the results of the further development of the above described conventional technologies. 
     As a means for solving the above-described problems, it was conceivable to divide a driving force transmitting portion into a two portions, that is, a portion for transmitting a driving force to a photosensitive drum and a toner stirring member, and a portion for transmitting a driving force to a sealing-member winding unit, and to begin driving the photosensitive drum and toner stirring member after finishing driving the toner-seal winding unit. In addition to the above-described problems, the conventional structure suffers another problem. That is, when a sealing member begins to be wound, the process cartridge is yet to be securely positioned relative to the apparatus main assembly, and therefore, while the sealing member is wound to be torn open, the process cartridge is sometimes caused to vibrate by the driving force from the image-forming-apparatus main assembly. 
     As the process cartridge vibrates, the coupling member on the process cartridge side, through which the electrophotographic photosensitive drum is driven by the driving force from the image forming apparatus main assembly, fails to align with the coupling member on the image forming apparatus main assembly side, making it difficult for the coupling member on the cartridge side to be inserted into the coupling member on the main assembly side. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a driving force transmitting coupling member, a process cartridge, and an image forming apparatus, which make it possible to approximately fix the positional relationship between a driving force transmitting coupling member and a coupling member on the main assembly side when the driving force transmitting coupling member transmits driving force to a driving means for tearing open a sealing member. 
     Another object of the present invention is to provide a driving force, transmitting-coupling member, a process cartridge, and an image forming apparatus, that make it possible to virtually unfix the previously fixed positional relationship between a driving-force, transmitting-coupling member and a coupling member on the main-assembly side when a driving-force, transmitting-coupling member transmits a driving force to a stirring member. 
     Another object of the present invention is to provide a coupling member for driving a driving means which does not cause a process cartridge to vibrate when a sealing member is torn open, and allows the coupling member on the image forming apparatus main assembly side to easily engage with the coupling member of an image bearing member after the completion of the tearing of the sealing member, and driving a driving means for a stirring member, a process cartridge comprising such a coupling member, and an image forming apparatus in which such a process cartridge is removably installable. 
    
    
     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 sectional view of the essential portion of the process cartridge in the preferred embodiment of the present invention, at a plane perpendicular to the longitudinal direction of the cartridge. 
     FIG. 2 is a schematic sectional view of the essential portion of the image forming apparatus in the preferred embodiment of the present invention, at a plane perpendicular to the longitudinal direction of the process cartridge. 
     FIG. 3 is a schematic perspective view of the toner storage container of the process cartridge in the first embodiment of the present invention which is in the brand-new condition. 
     FIG. 4 is a schematic perspective view of the toner storage container of the process cartridge in the first embodiment of the present invention, from which the toner seal has been wound away. 
     FIG. 5 is a schematic perspective view of the toner storage container of the process cartridge in the first embodiment, in which the toner stirring member has begun to be rotated. 
     FIG. 6 is a schematic perspective view of the process cartridge in the first embodiment, when the toner seal is being wound. 
     FIG. 7 is a schematic perspective view of the process cartridge in the first embodiment, when the photosensitive drum and stirring member are being rotated. 
     FIG. 8 is a schematic perspective view of the first coupling of the process cartridge, and the first coupling of the image forming apparatus main assembly, in the first embodiment. 
     FIG. 9 is a sectional view of a combination of the second coupling of the process cartridge and the second coupling of the image forming apparatus main assembly, in the first embodiment, at a plane perpendicular to the axial lines of the two coupling members, when the two couplings are rotating in the direction to tear open the toner seal. 
     FIG. 10 is a sectional view of a combination of the second coupling of the process cartridge and the second coupling of the image forming apparatus main assembly, in the first embodiment, at a plane perpendicular to the axial lines of the two coupling members, when the two couplings are rotating in the direction to drive the stirring member. 
     FIG. 11 is a flow chart for the first embodiment. 
     FIG. 12 is an abbreviated circuit diagram for the first embodiment. 
     FIG. 13 is a sectional view of a combination of the second coupling of the process cartridge and the second coupling of the image forming apparatus main assembly, in the second embodiment, at a plane perpendicular to the axial lines of the two coupling members, when the two couplings are rotating in the direction to tear open the toner seal. 
     FIG. 14 is a sectional view of a combination of the second coupling of the process cartridge and the second coupling of the image forming apparatus main assembly, in the second embodiment, at a plane perpendicular to the axial lines of the two coupling members, when the two couplings are rotating in the direction to drive the stirring member. 
     FIG. 15 is a sectional view of a combination of the second coupling of the process cartridge and the second coupling of the image forming apparatus main assembly, in the third embodiment, at a plane perpendicular to the axial lines of the two coupling members, when the two couplings are rotating in the direction to tear open the toner seal. 
     FIG. 16 is a sectional view of a combination of the second coupling of the process cartridge and the second coupling of the image forming apparatus main assembly, in the third embodiment, at a plane perpendicular to the axial lines of the two coupling members, when the two couplings are rotating in the direction to drive the stirring member. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 1 and 2. 
     Description of Process Cartridge and Image Forming Apparatus Main Assembly 
     FIG. 1 illustrates a cross section of the essential portion of a process cartridge in accordance with the present invention, at a plane perpendicular to the longitudinal direction of the cartridge. FIG. 2 illustrates a cross section of the essential portion of an image forming apparatus in accordance with the present invention, at a plane perpendicular to the longitudinal direction of the process cartridge. This process cartridge is provided with an image bearing member and one or a plurality of processing means which act on the image bearing member. As for the processing means, there are, for example, a charging means for charging the peripheral surface of the image bearing member, a developing apparatus for forming a toner image on the image bearing member, and a cleaning means for removing the toner remaining on the peripheral surface of the image forming apparatus. The process cartridge is provided with an electrophotographic photosensitive member as the image bearing member, and at least one processing means among the above listed processing means. 
     Referring to FIG. 1, in the case of the process cartridge  15  in this embodiment, a charging roller  12  as the charging means, a development roller  18  and a development blade, which constitute the developing apparatus, a toner storage frame  16  as a developer storage container in which toner as developer is stored, a stirring member  20  as a rotational member for stirring the toner in the toner storage frame  16 , a cleaning blade  14  as the cleaning means, and an electrophotographic photosensitive drum  11 , along the peripheral surface of which the preceding processing means are disposed, are integrally disposed in a housing to form the process cartridge  15  removably installable in the main assembly of an image forming apparatus. 
     This process cartridge  15  is installed into an image forming apparatus C illustrated in FIG. 2 to be used for image formation, which is carried out through the following steps. First, a sheet S is conveyed to an image transfer location adjacent to the peripheral surface of the photosensitive drum  11 , from a sheet cassette  6  installed in the bottom portion of the image forming apparatus C, by a pickup roller  4 , a pair of conveyer rollers  7 , and a registration roller  5 . Meanwhile, the photosensitive drum  11  is selectively exposed to light modulated with image information by an exposing apparatus  8  after being charged by the charge roller  12 . As a result, an electrostatic latent image is formed. The exposure by the exposing apparatus  8  is carried out in synchronism with the sheet conveyance by the registration roller  5 . After the formation of the electrostatic latent image, the toner that has been delivered into the developing means frame  17  from the toner-storage frame  16  is coated in a thin layer on the peripheral surface of the development roller  18  by the development blade  19 . As a development bias is applied to the development roller  18 , the toner is supplied from the development roller  18  to the photosensitive drum  11  in a pattern corresponding to the pattern of the electrostatic latent image, forming a toner image on the photosensitive drum  11 . This toner image is transferred onto the sheet S, which is being conveyed, by applying a bias (voltage) to the transfer roller  9  at the transfer location. Thereafter, the sheet S is conveyed to a fixing apparatus  10 , in which the toner image is fixed to the sheet S, and then, the sheet S is discharged by a pair of discharge rollers  1 , into a delivery portion  2  located at the top of the image forming apparatus. 
     Frame Structure of Process Cartridge 
     Referring to FIG. 1, the above described process cartridge  15  comprises the toner storage frame  16 , the developing means frame  17 , and the cleaning means frame  13 , which are sandwiched by a pair of side covers  36  as shown in FIG.  6 . The toner storage frame  16  contains the toner stirring member  20 , and the toner delivery opening  31  of which is sealed with a toner sealing member  21 . The developing means frame  17  supports the development roller  18  and development blade  19 . The cleaning means frame  13  supports the cleaning blade  14 , and also pivotally supports the developing means frame  17 . The side covers  36  cover the entire longitudinal ends of the toner storage frame  16 , developing means frame  17 , and cleaning means frame  13 . 
     The toner storage frame  16  and developing means frame  17  are connected to each other, with the toner delivery opening  31  of the toner storage frame  16  and the toner receiving opening of the developing means frame  17  connected by a flexible sealing member  37 , forming an airtight passage between the two frames  16  and  17 . 
     Description of Tearing of Toner Seal and Driving of Stirring Member 
     FIGS. 3 to  5  depict the toner storage frame in accordance with the present invention, and FIGS. 6 and 7 depict the process cartridge and the gear train within the image forming apparatus main assembly. Referring to FIG. 3, in the case of a brand-new process cartridge, the opening  31  of the toner storage frame  16  for supplying toner into the developing means frame  17  is covered with the toner sealing member  21 , which is welded or glued to the toner storage frame  16  in a manner to cover the opening  31 . The one end  21   a  of the toner sealing member  21  is folded back at a line slightly outward beyond the welding line, is extended back across the opening  31 , and is fixed to the round shaft of a winding member rotatably supported by the toner storage frame  16 . The width of the folded-back portion of the toner sealing member  21  is narrower than the width of the portion of the toner sealing member  21  welded or glued to the toner storage frame  16  in a manner to cover the opening  31 . 
     The toner sealing member  21  is provided with an electrically conductive portion  22 , which is laid across the electrically nonconductive polyethylene terephthalate portion of the toner sealing member  21 , to detect whether or not the opening  31  has been entirely exposed; the conductive portion  22  is laid across the downstream side of the toner sealing member  21  in terms of the direction in which the toner sealing member  21  is torn. In this embodiment, the conductive portion  22  is a piece of aluminum foil pasted to the toner sealing member, across the downstream side of the toner sealing member  21  in terms of the tearing direction of the toner sealing member  21 . Across this conductive portion  22 , voltage is applied from the detecting portion of the image forming apparatus main assembly. More specifically, the process cartridge  15  is provided with a metallic plate equipped with a pair of contacts  34   a  and  34   b,  and the voltage is applied to the conductive portion  22  through this metallic plate. 
     As the process cartridge  15  in the brand-new condition is installed into the image forming apparatus main assembly, the detecting portion  35  and conductive portion  22  are electrically connected through the contacts  34   a  and  34   b.  Thus, until the toner sealing member  21  is almost completely wound up, electrical current is allowed to conduct through the conductive portion  22 , and is detected by the detecting portion  35  of the image forming apparatus main assembly. Upon detection of this current flow through the conductive portion, a motor  26  provided as a driving force source on the image forming apparatus main assembly side begins to rotate in the direction indicated by an arrow mark A. 
     Referring to FIG. 6, the image forming apparatus main assembly is provided with the motor  26 , an idler gear  42 , a first coupling  43 , an idler gear  33 , and a second coupling  25 . 
     Referring to FIGS. 3 and 6, as the motor  26  rotates in the direction of the arrow mark A, a motor gear  26   a,  integral with the output shaft of the motor  26 , rotates. Upon receiving the rotational force transmitted from the motor gear  26   a  through the idler gear  42 , the first coupling  43  in the image-forming-apparatus main assembly moves in the direction of an arrow mark D while rotating in the direction of an arrow mark C, without coupling with the first driving-force transmission coupling  44 , with which one of the longitudinal ends of the photosensitive drum  11  in the process cartridge  15  is provided. Therefore, the photosensitive drum  11  does not rotate in the direction reverse to the normal direction. The second driving-force transmission coupling gear  24  in the process cartridge  15  receives a driving force by engaging with the second coupling  25  on the image-forming-apparatus-main-assembly side, to which the driving force is transmitted from the motor  26  of the image-forming-apparatus main assembly through the idler gear  33 . The second driving-force transmission coupling gear  24  transmits the driving force to an oscillatory gear  29 , with which the process cartridge  15  is provided, and which is illustrated in FIG. 3, which shows the toner-storage frame  16  from which the pair of side covers  36  have been removed. Upon the transmission of the driving force to this oscillatory gear  29 , the oscillatory gear  29  moves toward the idler gear  30 , and meshes therewith, transmitting thereby the driving force thereto. As a result, the gear  23   a  of the winding member  23 , which meshes with the idler gear  30 , rotates, causing the toner sealing member  21  to be wound in the direction of an arrow mark B. At this point, the oscillatory gear  29  is not in meshing engagement with an oscillatory idler gear  27 ; there is a gap between the two oscillatory gears. 
     The oscillatory gear  29  is rotatably supported by the end portion of an unillustrated oscillatory arm axially attached to the toner storage frame  16 , in such a manner that the center of the oscillatory gear  29  is on a line perpendicular to the line that connects the centers of the oscillatory idler gear  27  and idler gear  30 . The oscillatory axis of the oscillatory arm coincides with the rotational axis of the second driving-force transmission coupling gear  24 . When not in operation, the oscillatory gear is retained where it does not mesh with either of the oscillatory idler gear  27  and idler gear  30 , by pulling the oscillatory arm with the use of a pair of springy members that pull the oscillatory arm in opposing directions. The oscillatory gear  29  meshes with the gear portion  24   g  (FIGS.  9  and  10 ), that is, the peripheral portion, of the second coupling gear  24 . In other words, the inward portion of the second coupling  24  constitutes the actual coupling portion, and the peripheral portion of the second coupling gear  24  constitutes the gear portion  24   a.    
     Thus, as the second coupling gear  24  rotates in the clockwise direction as shown in FIG. 3, the oscillatory gear  29  pivots about the same axis as the second coupling gear  24  due to the tooth load between the gear portion  24   a  of the second coupling gear  24 , and the oscillatory gear  29 , and meshes with the idler gear  30  which drives the winding gear  23   a.  As the second coupling gear  24  stops, the oscillatory gear  29  is retracted from the idler gear  30  by the aforementioned springy members; the meshing between the oscillatory gear  29  and idler gear  30  is disengaged. 
     Referring to FIG. 5, as the second coupling gear  24  rotates in the counterclockwise direction (direction of arrow mark I), the oscillatory gear  29  pivots about the same axis as the second coupling gear  24  due to the tooth load between the gear portion  24   g  of the second coupling gear  24  and the oscillatory gear  29 , and meshes with the oscillatory idler gear  27  for transmitting the driving force to the stirring gear  32 . 
     The oscillatory idler gear  27  is a compound gear integrally comprising a pair of gears different in diameter, the smaller of which meshes with an idler gear  28 . The idler gear  28  is also a compound gear integrally comprising a pair of gears different in diameter, the smaller of which meshes with the stirring gear  32 . 
     The idler gears  27  and  28 , and the stirring gear  32 , are individually and rotatably attached to one of the side walls of the developing means frame  17 . The stirring gear  32  is connected to the toner stirring member  20 . 
     The above does not means that the means for changing the direction in which the oscillatory gear  29  pivots, in accordance with rotational direction in which the coupling gear  24  rotates, is limited to the above described means. 
     The idler gear  30  is rotatably supported by the toner storage frame  16  of the process cartridge  15 . The idler gear  30  is a compound gear integrally comprising a spur gear  30   a,  with or from which the oscillatory gear  29  engages or disengages, and a bevel gear  30   b,  which meshes with the bevel gear  23   a  integral with the winding member  23 . 
     Referring to FIG. 4, as the toner sealing member  21  is wound in the direction of the arrow mark B, the conductive portion  22  is severed after the opening  31  is fully exposed. Consequently, the electrical connection between the contacts  34   a  and  34   b  is lost. Referring to FIG. 5, as this severed state of the conductive portion, that is, a state in which the electrical connection between the contacts  34   a  and  34   b  has been lost, is detected by the detecting portion  35  of the image forming apparatus main assembly, the CPU (FIG. 12) of the image forming apparatus main assembly controls the motor driving portion so that the motor  26 , which has been supplying the second coupling  25  on the main assembly side with the force for driving the winding member  23 , rotates in reverse. Next, referring to FIG. 7, as the motor  26  rotates in reverse, that is, in the direction of an arrow mark F, the first coupling  43  on the image-forming-apparatus-main-assembly side moves in the direction of the arrow mark H while remaining in mesh with the idler gear  42  and rotating in the direction of an arrow mark G, couples with the first driving force transmission coupling  44 , with which one of the longitudinal ends of the photosensitive drum  11  in the process cartridge  15  is provided, and rotates while remaining coupled with the first driving force transmission coupling  44 , to transmit the driving force to the photosensitive drum  11 . 
     Referring back to FIG. 5, the second driving force transmission coupling  24  in the process cartridge  15  also rotates in reverse. As a result, the oscillatory gear  29  moves away from the idler gear  30 , becoming disengaged therefrom, and engages with the oscillatory idler gear  27 , causing the oscillatory idler gear  27  to rotate, which in turn transmits, through the idler gear  28 , the driving force to the stirring gear  32  for rotating the stirring member  20  in the toner storage frame  16  shown in FIG.  1 . 
     Description of Driving Force Transmitting Method and Coupling Members 
     Here, referring to FIGS. 8 to  10 , the configurations of the couplings will be described. 
     Referring to FIG. 8, the first driving force transmission coupling  44  is provided with a projection  44   a  which is approximately in the form of a triangular prism, more specifically, a triangular prism twisted about its rotational axis in its rotational direction. The first coupling  43  on the main assembly side is provided with a recess which is approximately in the form of a triangular prism twisted about its rotational axis, and in which the projection  44   a  engages. With this arrangement, as the first driving force transmission coupling  44  fits into the first coupling  43  on the main assembly side, and is rotated thereby, the edges of the projection  44   a  make contact with the interior surfaces of the recess  43   a,  one for one, simultaneously and in the same manner. Therefore, the axial lines of the two couplings become aligned with each other while transmitting driving force. 
     Since the coupling portion of the first coupling  44 , and the coupling portion of the coupling  43  on the main assembly side, are constituted of a projection and a recess, respectively, in the form of a twisted triangular prism, the rotation of the first coupling  44  after its engagement with the coupling portion  43  generates thrust in their axial direction. More specifically, referring to FIG. 6, as the first coupling  43  on the main assembly side rotates in the direction of the arrow mark C, it is moved in the direction of the arrow mark D. Referring to FIG. 7, as the first coupling  43  on the main assembly side rotates in the direction of the arrow mark G after its engagement with the first coupling  44 , it is moved in the direction of the arrow mark H by being pulled by the first coupling  44  because of their twisted shape. 
     As is evident from the above description, as the first coupling on the main-assembly side rotates in the direction of the arrow mark C, it does not remain engaged with the first coupling  44 , and therefore, the two couplings are not positioned relative to each other in any specific manner. On the other hand, as the first coupling  43  on the main-assembly side rotates in the direction of the arrow mark G, it engages with the first coupling  44 , with a progressively increasing margin, while establishing a proper positional relationship relative to the first coupling  44 . 
     Next, referring to FIGS. 9 and 10, the second coupling  25  on the image forming apparatus main assembly side is provided with a projection in the form of a flatted round column, and the portions adjacent to the two parallel edges of each of the pair of flat surfaces of this projection constitute a pair of contact portions  25   a  and  25   b.  The contact portions  25   a  and  25   b  on one of the flat surfaces are symmetrical in position and size to those on the other flat surface with respect to the axial line of the second coupling  25 . On the other hand, the second coupling gear  24  in the process cartridge  15  is provided with a cylindrical recess  24   d,  and the wall of the cylindrical recess  24  is provided with an opposing pair of right-angled ribs. The surfaces of each rib, which are perpendicular to each other, constitute flat contact portions  24   a  and  24   b.    
     Referring to FIG. 9, as the second coupling  25  on the main assembly side rotates in the recess  24   d  of the second coupling gear  24 , in the direction of an arrow mark E to tear open the toner seal, the contact portions  24   a  of the angular ribs of the second coupling gear  24  and the contact portions  25   a  of the coupling  25  come into contact with each other, whereby the driving force is transmitted. 
     Also referring to FIG. 9, in order to reduce the gap  40 , which is formed between the surface of the recess  24   d  of the second coupling gear  24  and the corresponding curved surface of the projection of the second coupling  25  on the main-assembly side, in terms of the radial direction of the two couplers  24  and  25 , as the second coupling  25  on the main-assembly side rotates in the recess  24   d  of the second coupling gear  24 , in the direction of the arrow mark E to tear open the toner seal, and the contact portions  24   a  of the angular ribs of the second coupling gear  24  and the contact portions  25   a  of the coupling  25  come into contact with each other, the two portions  24   e  of the surface of the recess  24   d,  which oppose each other with respect to the axial line of the coupling  24 , and face the opposing curved surfaces of the projection of the second coupling  25 , one for one, after the contact between the corresponding contact portions of the couplers  24  and  25 , are rendered greater in diameter, making these surfaces virtually parallel to the corresponding surfaces  24   b.    
     In cross section, the pair of opposing curved portions  25   d  (surfaces) of the second coupling  25  on the main-assembly side, form an arc, which is included in a circle, the center of which coincides with the rotational axis of the second coupling  25  on the main-assembly side. Further, the two virtually flat surfaces  24   e  of the recess of the second coupling  24  are an equal distance away from the rotational axis of the second coupling  24 . 
     In this embodiment, the gap between the second coupling gear  24 , and the second coupling  25  on the main assembly side, in terms of the radial direction of the two couplings, is made to be approximately 0.5 mm. Next, referring to FIG. 10, as the driving for tearing open the toner sealing member  21  ends, the second coupling  25  on the main assembly side rotates in reverse in the direction of the arrow mark I, causing the contact portions  24   b  of the second coupling gear  24  to come in contact with the contact portion  25   b  of the second coupling on the main assembly side. As a result, the second coupling gear  24  is driven, and the driving force is transmitted to the toner stirring member  20 . Further, the two couplings  25  and  24  are configured so that during this driving of the second coupling gear  24  in the direction of the arrow mark I by the second coupling  25  on the apparatus main assembly side, there will be a gap  41  between the two couplings in terms of the radial direction of their rotational axes. In this embodiment, this gap is approximately 2 mm. 
     With the provision of the above structural arrangement, while the toner sealing member  21  is torn open, the positions of the rotational axes of the second coupling  25  on the main assembly side and second coupling gear  24  are stabilized virtually in alignment with each other, without rotationally driving the photosensitive drum  11 . During the period after the toner sealing member  21  is torn open, that is, during image formation, the rotational axis of the first coupling  44  with which the photosensitive drum  11  is provided, and the rotational axis of the first coupling  43  on the main assembly side, become the primary rotational axes, and therefore, even when the rotational axis of the second coupling  24  for transmitting the driving force to the stirring member  20 , and the rotational axis of the second coupling  25  on the main assembly side, are deviated from each other, the aligning of these two axes does not occur. Thus, the driving force is transmitted to the second coupling for driving the stirring member  20 , without interfering with the aligning of the rotational axis of the first coupling  43  on the main assembly side and the rotational axis of the first coupling  44 . In other words, it is permitted that the rotational axis of the second coupling  44  and the rotational axis of the first coupling  43  become misaligned with each other. 
     The above described operation may be summarized in the form of a flow chart given in FIG.  11 . FIG. 12 shows the abbreviated diagram of the circuit which controls the operation. 
     Upon installation of the process cartridge in this embodiment into the image forming apparatus, it is confirmed in step S 1  whether or not current is allowed to flow through the conductive portion. When current flow is detected, step S 2  is taken, in which the winding of the toner sealing member  21  is started. Next, in step S 3 , the tearing of the toner sealing member  21  continues, and eventually, the conductive portion  22  is severed. In step S 4 , the severing of the conductive portion  22  is detected, and therefore, it is determined that the tearing of the toner sealing member  22  has been completed. Next, in step S 5 , the motor  26  within the image forming apparatus main assembly is rotated in reverse to begin rotating the toner stirring member  20 . 
     The detecting portion  35  comprises a DC power source and a current monitor. It applies voltage from the power source, and measures the current by the monitor to detect whether or not the toner sealing member  21  has been completely torn open. 
     Embodiment 2 
     Referring to FIGS. 13 and 14, this embodiment is different from the first embodiment in terms of the configuration of the contacting surfaces of the second coupling gear and the second coupling on the main assembly side. Otherwise, this embodiment is identical to the first embodiment. Thus, only the contact surfaces in this embodiment will be described below. 
     The second coupling  25  on the image forming apparatus main assembly side is provided with a projection in the form of a flatted round column. This projection is provided with a pair of ribs  25   c,  which are approximately semicircular in cross section, and symmetrical to each other with respect to the rotational axis of the second coupling  25  on the main assembly side. On the other hand, the second coupling  24  of the process cartridge  15  is provided with a cylindrical recess  24   d,  the cylindrical wall of which is provided with a pair of opposing, approximately right-angled ribs, which are symmetrical with respect to the rotational axis of the second coupling gear  24 . These ribs are provided with contact portions  24   a  and  24   b.  The contact portions  24   a  and  24   b  of one of the ribs are symmetrical with the contact portions  24   a  and  24   b  of the other rib, with respect to the rotational axis of the second coupling  24 . Both contact portions  24   a  are provided with a recess  24   f  which is approximately semicircular in cross section. 
     Referring to FIG. 13, as the second coupling  25  rotates in the direction of the arrow mark E, that is, the direction to tear open the toner seal, the ribs  25   c,  that is, the contact portions of the coupling  25 , which are approximately semicircular in cross section, engage in the recesses  24   f  with which the angular ribs of the second coupling gear  24  are provided, and transmits the driving force. 
     As the second coupling gear  24  rotates in the direction of the arrow mark E, that is, the direction to tear open the toner sealing member  21 , the ribs  25   c  which are approximately semicircular in cross section, and with which the coupling  25  on the main assembly side is provided, engages in the recesses  24   f  which are approximately semicircular in cross section, and with which the angular ribs of the second coupling gear  24  are provided. As a result, the movement of the two couplings  24  and  25  in the their radial direction relative to each other is regulated; the rotational axes of the coupling  24  and  25  are made to approximately align with each other. 
     As the ribs  25   c  engage into the recesses  24   f,  the contact portion  25   a  of the second coupling  25  on the main-assembly side comes into, and remains in, contact with the contact portion  24   a  of the second coupling gear  24 , transmitting the rotational force, or the driving force, from the second coupling  25  on the main-assembly side to the second coupling gear  24 . It should be noted here that instead of making the contact portions  24   a  and  25   a  contact each other, the surface of each rib  25   c  may be placed in contact with the surface of the corresponding recess  24   f.    
     Referring to FIG. 14, after the completion of the drive for tearing open the toner sealing member  21 , the second coupling  25  on the main assembly side is rotated in reverse in the direction of the arrow mark I, causing the contact portion  24   b  of the second coupling gear  24  to come into contact with the contact portion  25   b  of the second coupling  25  on the main assembly side. As a result, the second coupling gear  24  is driven to transmit the driving force to the stirring member  20 . 
     Embodiment 3 
     Referring to FIGS. 15 and 16, the second coupling gear, and the second coupling gear on the main assembly side, in this embodiment, which will be described below, are different in configuration from those in the second embodiment. Otherwise, this embodiment is identical in configuration to the second embodiment. More specifically, while the coupling portions in the second embodiment are approximately semicircular in cross section, the coupling portions in this third embodiment are rendered approximately triangular in cross section. 
     The second coupling  25  on the image forming apparatus main assembly side is provided with a projection in the form of a flatted round column. This projection is provided with a pair of ribs  25   c  which are approximately triangular in cross section. The second coupling gear  24  within the process cartridge  15  is provided with a cylindrical recess  24   d,  the cylindrical wall of which is provided with a pair of ribs, which are approximately triangular in cross section, with the surfaces of each rib serving as contact portions  24   a  and  24   b.    
     Referring to FIG. 15, as the second coupling  25  on the main assembly side is rotated in the direction of the arrow mark E, that is, the direction to tear open the toner sealing member  21 , the ribs  25   c  of the second coupling  25  on the main assembly side engage into the recesses  24   f  of the second coupling gear  24 , transmitting the driving force. 
     While the second coupling gear  24  is rotationally driven in the direction of the arrow mark E, that is, the direction to tear open the toner sealing member  21 , the ribs  25   c  which are triangular in cross section, and with which the second coupling  25  on the main assembly side, engage into, and remain in, the recesses  24   f  which are triangular in cross section, and with which the second coupling gear  24  is provided. As a result, the movement of the second coupling gear  24  in terms of the radial direction is regulated, and the rotational axes of the two couplings  24  and  25  are virtually aligned, and remain aligned, with each other. 
     As the ribs  25   c  engage into the recesses  24   f,  the contact portion  25   a  of the second coupling  25  on the main-assembly side comes into, and remains in, contact with the contact portion  24   a  of the second coupling gear  24 , transmitting the rotational force, or the driving force, from the second coupling  25  on the main-assembly side to the second coupling gear  24 . It should be noted here that instead of making the contact portions  24   a  and  25   a  contact each other, the surface of each rib  25   c  may be placed in contact with the surface of the corresponding recess  24   f.    
     Referring to FIG. 16, after the completion of the drive for tearing open the toner sealing member  21 , the second coupling  25  on the main assembly side is rotated in reverse in the direction of the arrow mark I, causing the contact portion  24   b  of the second coupling gear  24  to come into contact with the contact portion  25   b  of the second coupling  25  on the main assembly side. As a result the second coupling gear  24  is driven to transmit the driving force to the stirring member  20 . 
     As described regarding the first to third embodiments, according to the present invention, while the sealing member is torn open, the positional relationship between the second driving-force transmission coupling, and the second coupling on the main-assembly side, is virtually fixed, and remains virtually fixed, preventing a process cartridge from vibrating. Further, during this tearing of the toner sealing member, the first driving-force transmission coupling, and the first coupling on the main-assembly side, for transmitting a driving force to an image bearing member, are not engaged with each other, and therefore, it does not occur that the image-bearing member is rotated in reverse. In other words, during this period, the process cartridge is positioned at a position different from the position for image formation. 
     Further, when a driving force is transmitted to a stirring member, the first driving-force transmission coupling, and the first coupling on the main-assembly side, are engaged with each other, and are fixed in positional relationship relative to each other. Therefore, the process cartridge is prevented from vibrating. Also during this period, the process cartridge is placed in the position for image formation. Further, when the positional relationship between the first driving-force transmission coupling, and the first coupling on the main-assembly side, changes from the unengaged state to the engaged state, a certain amount of deviation is permitted between the rotational axis of the second driving-force transmission coupling, and the rotational axis of the second coupling on the main-assembly side. Therefore, the change of the positional relationship between the first driving-force transmission coupling, and the first coupling on the main-assembly side, from the unengaged state to the engaged state, is smooth. 
     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.