Patent Publication Number: US-2005141916-A1

Title: Process unit, process cartridge, and electrophotographic image forming apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a process unit, process cartridge, and an electrophotographic image forming apparatus.  
      2. Description of the Related Art  
      Hitherto, in an electrophotographic image forming apparatus in which an electrophotographic image forming process is used, a process unit detachable from a main body of the electrophotographic image forming apparatus is employed. By replacing the process unit with a new one, the apparatus can be maintained by an operator himself or herself without resorting to a maintenance person, thereby dramatically improving the operability of the apparatus.  
      In the above-mentioned process unit, a cleaning blade is used for removing developer remaining on an electrophotographic photosensitive member after transfer, and a developing blade is used for regulating the layer depth of developer adhering to the peripheral surface of a developing roller. Support members supporting these blades are fixed to a cartridge frame with screws (see Japanese Unexamined Patent Application Publication No. 6-130877, corresponding to U.S. Pat. No. 5,966,566).  
      For example, in the case of a metal screw, sometimes a metal piece (fine article) is produced during the production process, or a plating residue (fine article) is produced during plating. In the case of a resin screw, a resin residue (fine article) is sometimes produced. Also, since these screws are often distributed in a package, the screws lie in friction with each other during the distribution, thereby causing a fine article such as a metal piece or the like to be flaked off. In addition, abutment of the screw against the top of a screwdriver when fastening the screw with a screwdriver sometimes causes a fine article such as a metal piece to be flaked off. Further, the flaked-off fine article is sometimes separated away from the head of the screw and drops in a process cartridge. Also, from a construction view point of the process cartridge, a photosensitive drum, an electrostatic charging roller, a developing roller, and the like are sometimes disposed in the vicinity of the screws, especially in the lower area of the screws. In this case, there is a risk that a flaked-off fine article adheres to the photosensitive drum, the electrostatic charging roller, the developing roller, or the like. Conventionally, even when a flaked fine article adheres to the photosensitive drum or the like, the image quality required in the past was sufficiently satisfied. However, in order to satisfy the image quality required today, the electrophotographic image forming apparatus must be improved for higher quality.  
     SUMMARY OF THE INVENTION  
      The present invention is directed to a process unit, a process cartridge, and an electrophotographic image forming apparatus which minimize a risk that a fine article adhering to an exposed portion of a fastening member dropping onto an electrophotographic photosensitive member or a process device.  
      In one aspect of the present invention, a process unit detachably attached to an electrophotographic image forming apparatus operable to form an image on a recording medium, including: a process device facilitating forming the image; a support frame supporting the process device; a fastened object; a fastening member including a portion and fastening the fastened object to the support frame such that the portion is exposed from the support frame; and a cover member adapted to cover the exposed portion.  
      Further features and advantages of the present invention will become apparent from the following description of the embodiments with reference to the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagrammatic sectional view of an electrophotographic image forming apparatus according to an embodiment of the present invention.  
       FIG. 2  is a diagrammatic sectional view of a process cartridge according to the embodiment.  
       FIG. 3  is a perspective assembly view illustrating a process incorporating a photosensitive drum into a cleaning frame.  
       FIG. 4  is a schematic perspective view of a part of the image forming apparatus associated with attaching and detaching the process cartridge.  
       FIG. 5  is a schematic perspective view of the part of the image forming apparatus associated with attaching and detaching the process cartridge.  
       FIG. 6  is a side view of the process cartridge according to the embodiment.  
       FIG. 7  is a side view of the process cartridge according to the embodiment.  
       FIGS. 8A  to  8 D are schematic sectional views illustrating the attitude of the cartridge while being loaded.  
       FIG. 9  is a perspective assembly view illustrating a process of incorporating a developing roller into a toner developing frame.  
       FIG. 10  is a perspective assembly view of the development frame.  
       FIG. 11  is a schematic perspective view of the cleaning frame and a cleaning blade.  
       FIG. 12  is a schematic perspective view illustrating the building method of the cleaning blade.  
       FIG. 13  is a schematic perspective view illustrating the building method of the cleaning blade.  
       FIG. 14  is a schematic perspective view of cover means for a screw.  
       FIG. 15  is a schematic perspective view of cover means for the screw.  
       FIG. 16  is a schematic perspective view of cover means for the screw.  
       FIG. 17  is a schematic sectional view of cover means for the screw.  
       FIG. 18  is a schematic sectional view of the cover means for the screw.  
       FIG. 19  is a schematic sectional view of the cover means for the screw.  
    
    
     DESCRIPTION OF THE EMBODIMENTS  
     Embodiments  
      The best mode of embodiments of the present invention will be described with reference to the attached drawings. However, the scope of the present invention is not limited only to shapes, materials, and relative arrangements of components described in the embodiments unless a particular description is provided.  
     First Embodiment  
      A process cartridge will be described as an embodiment of a process unit by way of example. The process cartridge and an electrophotographic image forming apparatus from which the process cartridge is detachable will be concretely described with reference to  FIGS. 1 and 2 .  FIG. 1  is a diagrammatic sectional view of an electrophotographic image forming apparatus A having a process cartridge B according to the present embodiment loaded therein.  FIG. 2  is a diagrammatic sectional view of the process cartridge B according to the present embodiment.  
      Overall Structure of Image Forming Apparatus  
      The electrophotographic image forming apparatus can be, for example, a laser beam printer (hereinafter referred to as an image forming apparatus) A. As shown in  FIG. 1 , an optical system  1  serving as an optical mechanism illuminates information light based on image information to a drum-shaped electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum)  7 . As a result, an electrostatic latent image is formed on the photosensitive drum  7 . Then, a developer image is formed by developing the electrostatic latent image with developer T.  
      In synchronization with formation of the developer image, a recording medium (a sheet of recording paper, an OHP sheet, a piece of cloth, or the like)  2  is fed from a cassette  3   a  while being separated sheet by sheet by a pickup roller  3   b  and a pressing roller  3   c  pressing against the pickup roller  3   b.  The recording medium  2  is transported along a transport guide  3   f   1 . Then, by applying a voltage on a transfer roller  4  serving as a transfer mechanism, the developer image formed on the photosensitive drum  7  is transferred to the recording medium  2 . Subsequently, the recording medium  2  is transported to a fixing mechanism  5  along transport guide  3   f   2 . The fixing mechanism  5  has a drive roller  5   a  and a fixing rotor  5   d.  The developer image is fixed onto the recording medium  2  since the fixing mechanism  5  applies heat and pressure to the recording medium  2  which is passing therethrough. Then, the recording medium  2  is transported by an ejection roller  3   d  and ejected into an ejection unit  6 . According to the present embodiment, the pickup roller  3   b,  the pressing roller  3   c,  the ejection roller  3   d,  and so forth make up a transport mechanism  3 .  
      Process Cartridge  
      As shown in  FIG. 2 , the process cartridge B is provided with the photosensitive drum  7  and at least one process device. As the process unit, for example, an electrostatic charging mechanism charging the electrophotographic photosensitive member, a developing mechanism developing an electrostatic latent image formed on the electrophotographic photosensitive member, and a cleaning mechanism for cleaning the developer T remaining on the electrophotographic photosensitive member are included.  
      As shown in  FIG. 2 , in the cartridge B according to the present invention, the photosensitive drum  7  having a photosensitive layer rotates. Also, when a voltage is applied on an electrostatic charging roller  8  serving as the electrostatic charging mechanism, the photosensitive drum  7  is uniformly charged. The charged photosensitive drum  7  is exposed to information light (an optical image) based on image information, coming from the optical system  1  through an exposure aperture  9   b.  Thus, an electrostatic latent image is formed on the photosensitive drum  7 . Then, the electrostatic latent image is developed by the developing mechanism  10 .  
      The developing mechanism  10  includes a developing roller  10   d.  More particularly, a developing blade  10   e   2  regulates the layer depth of developer adhering to the peripheral surface of the developing roller  10   d  and is integrally built with a developing-blade support member (a sheet metal portion)  10   e   1  as a fastened object. The developing-blade support member  10   e   1  is fastened to a developing frame  10   f.  The developing roller  10   d  has a stationary magnet  10   c  built therein. A rotatable feed member  10   b  as a developer feeding mechanism feeds developer T stored in a developer storage  10   a  toward the developing roller  10   d,  and the developer T adheres to the developing roller  10   d.  Then, the developer T adhering to the peripheral surface of the developing roller  10   d  is regulated by the developing blade  10   e   2 . Subsequently, a developer layer having frictional-charged particles applied thereon is formed on the surface of the developing roller  10   d.  Then, the developer T moves over to the surface of the photosensitive drum  7  from the developing roller  10   d  in response to the electrostatic latent image, thereby causing the electrostatic latent image to be developed.  
      Then, the transfer roller  4  has a voltage applied thereon, with a reverse polarity to that of the developer image, so that the developer image is transferred to the recording medium  2 . Subsequently, the developer T remaining on the photosensitive drum  7  is removed by a cleaning blade  11   a   5  serving as a cleaning mechanism  11 . In other words, the blade  11   a   5  works to remove the developer T remaining after the transfer. The blade  11   a   5  is supported by a cleaning-blade support member  11   a   1 . The developer T scraped off by the blade  11   a   5  is collected in a removed-developer storage  11   c  so that a scooping sheet  11   b  does not cause the developer to leak outside the process cartridge.  
      The cartridge B according to the present embodiment has a cleaning frame  11   d  and the developing frame  10   f  respectively serving as first and second support frames. The cleaning frame  11   d  rotatably supports the photosensitive drum  7 , the cleaning blade  11   a   2 , and the electrostatic charging roller  8  serving as the electrostatic charging mechanism. The developing frame  10   f  supports the developing roller  10   d  and is rotatably supported to the cleaning frame  11   d  such that the developing roller  10   d  faces in parallel to the photosensitive drum  7  with a predetermined gap. In order to maintain the gap between the developing roller  10   d  and the photosensitive drum  7 , spacers  10   m  are placed at both ends of the developing roller  10   d.  Also, as shown in  FIG. 2 , the developing frame  10   f  has the developer chamber (developer storage)  10   a  and a developing chamber  10   i.    
      Attachment and Detachment of Process Cartridge to and from Main Body of Image Forming Apparatus  
      The manner of attachment and detachment of the process cartridge B to and from the image forming apparatus A will be described with reference to FIGS.  4  to  7 .  
      An opening and closing door (not shown) is first opened so as to expose guide members Ga and Gb. Then, in a state in which an arc portion  18   c   1  and a rotation stopper  18   c   2  of the cartridge B lie respectively ahead of and behind the cartridge B, the arc portion  18   c   1  and the rotation stopper  18   c   2  are placed on a first guide surface Ga 1 . As a result, a positioning portion  18   b  and a projection  11   g  of the cartridge B are placed on a first guide surface Gb 1  of the other guide member Gb. In this state, the cartridge B is pressed into a main body  150  of the image forming apparatus A.  
      With this operation, the arc portion  18   c   1  and the rotation stopper  18   c   2  are guided to respective loading positions regulated by the first guide surface Ga 1 , a second guide surface Ga 2 , a third guide surface Ga 3 , and a fourth guide surface Ga 4 . On the other hand, the positioning portion  18   b  and the projection  11   g  lying on the opposite side of the cartridge B are guided to respective loading positions regulated by a plurality of the first guide surface Gb 1 , a second guide surface Gb 2 , a third guide surface Gb 3 , a fourth guide surface Gb 4 , and so fourth.  
       FIGS. 8A  to  8 D illustrate the attitudes of the cartridge B midway through the above-mentioned loading. The attitudes and the positions of the cartridge B from its position close to the opening and closing door to the final positioning portion are illustrated in the order of  FIGS. 8A  to  8 D.  FIG. 8A  illustrates a state in which the arc portion  18   c   1  and the rotation stopper  18   c   2  are respectively abutted against the second and first guide surfaces Ga 2  and Ga 1 .  FIG. 8B  illustrates a state in which the arc portion  18   c   1  and the rotation stopper  18   c   2  are respectively abutted against the third guide and second surfaces Ga 3  and Ga 2 .  FIG. 8C  illustrates a state in which the arc portion  18   c   1  and the rotation stopper  18   c   2  are respectively abutted against the fourth and third guide surfaces Ga 4  and Ga 3 .  FIG. 8D  illustrates a state in which the cartridge B is arranged at the final position.  
      In the manner as described above, the cartridge B is placed at the loading position of the main body  150  of the apparatus. Subsequently, when the door is closed, a triangular coupling (see  FIGS. 8A  to  8 D) included in the cartridge B is engaged with a drive transmission member (not shown) which has a twisted, depressed, and approximately triangular shape and is provided in the main body  150  of the apparatus, and a rotational drive force is transmitted from the main body  150  of the apparatus to the cartridge B.  
      The above described attitudes indicate the attitudes of the cartridge B during formation of an image. Then, the formation of an image starts.  
      When the cartridge B is unloaded from the main body  150  of the apparatus, the reverse operation to the foregoing loading operation is performed. More particularly, the cartridge B is pulled out along the guide members Ga and Gb from its loading position to the outside of the main body  150  of the apparatus. At the same time, a drum shutter  12  rotates so as to successively cover a photosensitive drum  7  and is finally closed.  
      The cleaning frame lid will be now described.  
      As shown in  FIG. 3 , the photosensitive drum  7  has a cylinder having an electrophotographic photosensitive layer and a drum gear  71  at one end thereof in its axial direction. The drum gear  71  is integrally formed by a gear (not shown) for transmitting a drive force to the developing roller  10   d  and the transfer roller  4  and by a coupling mechanism  70  for transmitting the drive force-transmission. Also, a flange  85  provided with a bearing is coupled with the photosensitive drum  7  at the other end of the photosensitive drum  7  in the axial direction and has a grounding unit (not shown) for grounding the photosensitive drum  7 . A portion of the photosensitive drum  7  close to the coupling mechanism  70  is rotatably supported by a bearing member  18   c.  The bearing member  18   c  serving as a fastened object is fixed to the cleaning frame  11   d  with a fastening member such as a screw. In addition, the positioning portion  18   b  is pressed into the other end of the photosensitive drum  7  by a positioning pin  18   d.  Thus, the other end of the photosensitive drum  7  is rotatably supported by the cleaning frame  11   d.    
      The support mechanism of the electrostatic charging roller  8  will be described. Core bars  8   a  of the electrostatic charging roller  8  exposed at both ends thereof are rotatably supported by a charging-roller bearing member  8   b.  The charging-roller bearing member  8   b  is fixed to the cleaning frame  11   d , is slidably supported in the direction toward the center of rotation of the photosensitive drum  7 , and is also pressed toward the same direction by a compression spring  8   c.  With this arrangement, the electrostatic charging roller  8  is abutted against the photosensitive drum  7  with a predetermined amount of pressure. When the photosensitive drum  7  rotates in this state, the electrostatic charging roller  8  is caused to rotate. Although no screw is used for fixing the charging-roller bearing member  8   b  to the cleaning frame  11   d  in the present embodiment, a screw may be used for the fixing.  
      The developing frame  10   f  of the cartridge B will be described next.  
      As shown in  FIGS. 2, 9 , and  10 , the developing frame  10   f  is formed by coupling an upper frame  10   f   1  and a rid member  10   f   2  and is provided with the developer chamber (developer storage)  10   a  and the developing chamber  10   i.    
      The upper frame  10   f   1  has an agitation axis  10   b   1  for feeding the developer T and a sheet member  10   b   2  fixed to the agitation axis  10   b   1 . A transport gear  10   b   3  regulating the lengthwise extension of the agitation axis  10   b   1  is coupled with the agitation axis  10   b   1 , together with a seal member  10   b   4  protecting the developer T from leaking outside the upper frame  10   f   1 .  
      The upper frame  10   f   1  is provided with a developer-passing aperture  10   k  through which the developer T stored in the developer storage  10   a  passes when fed to the developing roller  10   d.    
      As shown in  FIG. 10 , a developer seal member  27  is fixed by heat to a seal-fixing portion  10   h  extending along the four edges of the aperture  10   k.  Also, the upper frame  10   f   1  is provided with a developer-filling port (not shown), at one end thereof in its longitudinal direction, for filling the developer chamber  10   a  with the developer T. After the developer chamber  10   a  is filled with the developer T through this developer-filling port, the developer-filling port is sealed with a cap member  10   j.    
      End seals  10   r  for preventing the developer from leaking out from both ends of the developing roller  10   d  are fixed to both ends of the upper frame  10   f   1 . Also, at both ends of the developing blade  10   e   2 , seal members  10   s  for preventing leakage of the developer are attached on the upper frame  10   f   1  and the rid member  10   f   2  with double-sided adhesive tapes or the like.  
      Structure of End Member  
      Referring now to  FIG. 9 , the structure of an end member will be described.  
      An end member  10   g  disposed at one end of the developing roller  10   d  in its longitudinal direction covers a developing-roller gear  10   n  and a gear train. The end member  10   g,  as a fastened object, is fastened to the developing frame  10   f  with a screw  100 . The developing-roller gear  10   n  (see  FIG. 9 ) is fixed to the end of the developing roller  10   d,  and is engaged with the drum gear (not shown) fixed to the end of the photosensitive drum  7 . The gear train has two idler gears  10   p  and  10   q  for transmitting a drive force from the developing-roller gear  10   n  to the transport gear  10   b   3  of the developer feeding member  10   b.    
      The developer seal member  27  is bent twice at one end of the aperture  10   k  in its longitudinal direction and can be pulled outside through a perforation  10   f   11  (see  FIG. 9 ) of the upper frame  10   f   1  before operation.  
      Referring next to FIGS.  11  to  13 , the structure around the cleaning blade  11   a   5  will be described. The cleaning-blade support member  11   a   1  and the cleaning blade  11   a   5  serving as fastened objects are integrally formed with each other. A support member  11   a   1  is fastened to the cleaning frame  11   d  such that a top-sided edge  11   a   6  (shown in  FIG. 3 ) of the blade  11   a   5  elastically comes into contact with the surface of the photosensitive drum  7  with a predetermined amount of pressure. The screw  100  composed of metal is used for this fastening. The support member  11   a   1  is shaped so as to be positioned relative to the cleaning frame  11   d  and, as a sheet metal portion, has rectangular notches  11   a   2  disposed at both ends thereof in the longitudinal direction, whereby the position of the blade  11   a   5  in the short side thereof is determined, and the notches  11   a   2  engage with respective rectangular projections  11   d   1  disposed on the cleaning frame  11   d.  Also, the support member  11   a   1  has positioning perforations  11   a   3  disposed at both ends thereof in the longitudinal direction, whereby cylindrical projections  11   d   2  disposed on the cleaning frame  11   d  engage with the corresponding positioning perforations  11   a   3 . As a result, the longitudinal position of the blade  11   a   5  is also determined. The support member  11   a   1  also has screw holes  11   a   4  perforated therein for being fixed to the cleaning frame  11   d  and is fastened to the cleaning frame  11   d  with the screws  100  by passing them through the corresponding screw holes  11   a   4 .  
      In the present embodiment, the cartridge B is loaded in the main body  150  of the apparatus with its attitude shown in  FIG. 2 . In this state, a head  101  of each screw  100  lies above the electrostatic charging roller  8  and also, as illustrated in the loading trajectory diagrams of the cartridge B shown in  FIGS. 8A  to  8 D, lies above the photosensitive drum  7  and the electrostatic charging roller  8  with the attitudes of the cartridge in the midway through the loading.  
      After the support member  11   a   1  is fastened with the screws  100 , each screw head  101  serving as an exposed object and exposed from the support member  11   a   1  is covered by a cover member  102 . In this state, as shown in  FIGS. 14 and 15 , the cover member  102  entirely covers the screw head  101 . Covering the entire screw head  101  prevents a fine article from dropping onto the process means or the photosensitive drum  7  from the screw head  101  and from adhering to it in a simple manner. Meanwhile, the fine article indicates a metal piece, a plating residue, a resin residue, and the like. The above-mentioned fine article is produced during the production process or the distribution process of screws, or when a screw comes into contact with the top of a screwdriver. Since the screws can be placed in optimal positions, the degree of freedom of arranging the screws is increased. Also, the screws and the process device can be placed in a mutually closed state, thereby contributing to miniaturization of the process cartridge and the image forming apparatus.  
      As shown in  FIGS. 15 and 19 , a cover member  104  covers a groove  110  of the head  101 , which comes into contact with the top of a screwdriver serving at least as a tool. At least a part of the head  101  may be covered as described above. By covering only the groove  110  in the above-described manner, the same advantages as described above can be achieved while reducing the cost.  
      As the cover member  102  and the cover member  104 , a UV curable resin, an elastomer, an instant adhesive, a material for brazing, or the like entirely or partially covering the head  101  is available. Although these materials have respective viscosities at the time of covering, they are cured to the extent of not dropping out with the lapse of time after covering. With one of such materials, the head  101  can be easily covered before curing, and a fine particle such as a metal piece is reliably prevented from dropping after cured.  
      Alternatively, as shown in  FIG. 16 , an adhesive tape  105  may be used as a cover member.  
      Also, as shown in  FIG. 17 , a cover member  106  composed of a material, such as resin, which does not generate metal powder, may be used. In this case, the cover material  106  protects the screw head  101  and is fixed to the support member  11   a   1  with the fixing mechanism  5  such as a double-sided adhesive tape or an adhesive.  
      The screws  100  according to the present embodiment are disposed inside the casing of the cartridge B, not outside the cartridge B. In other words, even when the screws  100  are disposed inside the casing of the cartridge B together with the process device or the photosensitive drum  7 , a risk that an image is disturbed when a metal piece or the like drops onto any of these process device is prevented.  
      The screws  100  according to the present embodiment are disposed so as to overlap an image forming area  200  of the photosensitive drum  7  in the longitudinal direction of the cartridge B (see  FIG. 3 ). Also, the screws  100  are disposed so as to overlap the image forming area  200  of the photosensitive drum  7  and the process device, for example, the electrostatic charging roller  8  and the developing roller  10   d  acting on the photosensitive drum  7  (see  FIGS. 3 and 9 ). In addition, the screws  100  are arranged above the photosensitive drum  7 , the electrostatic charging roller  8 , and the developing roller  10   d.  Even when the screws  100  are disposed in an area which is likely to influence an image as described above, a risk that an image is disturbed when a fine particle adhering to one of the screws  100  drops onto any of these process means is prevented.  
      Furthermore, according to the present invention, an airflow occurs in the vicinity of each of the screws  100  due to a fan (not shown) provided in the image forming apparatus A and rotation of the photosensitive drum  7 , the developing roller  10   d,  and so forth, and the airflow is formed from the screw  100  towards the blade  11   a   5 . In such a case, a light fine particle which is likely to drop onto the blade  11   a   5  can be prevented from dropping by providing a cover member to the screw  100 .  
     Second Embodiment  
      A second embodiment of the present invention will be now described. Like parts as in the first embodiment are identified by the same reference numbers as those in the first embodiment, and the descriptions thereof will be omitted.  
      Referring to  FIG. 9 , the developing blade  10   e   2  will be described. The developing blade  10   e   2  is integrally formed with the developing-blade support member  10   e   1 . The support member  10   e   1  is fixed to the upper frame  10   f   1  such that a top-sided edge  10   e   3  of the blade  10   e   2  is elastically abutted against the surface of the developing roller  10   d  with a predetermined amount of pressure. The support member  10   e   1  is shaped so as to be positioned relative to the upper frame  10   f   1  and has a rectangular a notch  10   e   4  disposed at one end thereof in its longitudinal direction for being positioned in its short side direction. The notch  10   e   4  engages with a projection  10   f   4  disposed on the upper frame  10   f   1 . Also, the sheet metal portion (the support member)  10   e   1  has a positioning perforation  10   e   5  disposed at the other end thereof for being positioned both in the longitudinal and short side directions. The positioning perforation  10   e   5  engages with a cylindrical boss  10   f   5  disposed on the upper frame  10   f   1 . Also, the support member  10   e   1  has screw holes  10   e   6  perforated therein for being fixed to the upper frame  10   f   1 . The support member  10   e   1  is fastened and fixed to the upper frame  10   f   1  by passing the screws  100  serving as fastening members through the corresponding screw holes  10   e   6 . At the same time, scraping members  10   t  for scraping toner off the ends of the developing roller  10   d  are fixed to the support members  10   e   1  with the screws  100 . On this occasion, a rib  10   f   3  of the upper frame  10   f   1  becoming thin toward its top is set at dimensions with which it always digs into the developing blade  10   e   2 . The developing blade  10   e   2  and the upper frame  10   f   1  are hermetically sealed with each other without clearance.  
      After fastening the support member  10   e   1  with the screws  100 , each of the screw heads  101  as an exposed portion, exposed from the sheet metal surface, is covered by a cover member. As shown in  FIG. 18 , the entire cover member  102  may entirely cover the corresponding screw head  101 . Alternatively, as shown in  FIG. 19 , the partial cover member  104  may cover at least the groove  110 , which engages with the top of a screwdriver, of the corresponding screw head  101 .  
      According to the present embodiment, as described above, the cartridge B is loaded in the main body  150  of the apparatus with the attitude shown in  FIG. 2 . In this state, the screw head  101  lies above the developing roller  10   d  and also, as illustrated in the loading trajectory diagrams of the process cartridge B shown in  FIGS. 8A  to  8 D, lies above the photosensitive drum  7  with the attitudes of the cartridge in the midway through the loading. Even with the positional relation as in the present embodiment, by covering the screw heads  101  with cover members, the same advantages as those described in the first embodiment can be achieved. The details and the advantages of the cover member are the same as those in the first embodiment.  
      The end members  10   g  are fastened to the developing frame  10   f  with the corresponding screws  100 . Accordingly, the head  101  of the screw  100  exposed from each member  10   g  serving as a bearing member of the developing roller  10   d  is provided with a cover member. With this arrangement, a risk of adhesion of a fine article to the process means can be prevented.  
      As described above, according to the present invention, a risk that a fine article adhering to the exposed portion of a fastening member adheres to the process means or the electrophotographic photosensitive member can be reduced.  
      In the meantime, the electrophotographic image forming apparatus is such that an image is formed on a recording medium by using an electrophotographic image forming process, and an electrophotographic copying machine, an electrophotographic printer such as a laser printer and an LED printer, or the like is one of the apparatuses.  
      The process cartridge is such that the electrophotographic photosensitive member and the process means are integrated into a cartridge and that it is formed so as to be detachable from the main body of the electrophotographic image forming apparatus.  
      As the process device, for example, the electrostatic charging mechanism charging the electrophotographic photosensitive member, the developing mechanism forming a developer image on the electrophotographic photosensitive member, and the cleaning mechanism for removing developer remaining on the electrophotographic photosensitive member are included.  
      As the electrostatic charging mechanism, a corona electrostatic charger is available other than the electrostatic charging roller.  
      As the cleaning mechanism, a cleaning roller, a cleaning brush, or the like is available.  
      Those skilled in the art will appreciate that not only the support member supporting the process device but also a member other than that supporting the process device falls in the scope of the present invention as a fastened object. For example, there is a case in which a fastened object is another support frame.  
      Furthermore, it will be appreciated that the present invention is applicable to a case in which the fastened object and the process device are integrated. For example, there is a case in which the cleaning blade is composed of metal and the blade itself is fastened to the support frame.  
      Although the embodiments of the process cartridge have been described above, those skilled in the art will appreciate that the present invention is also applicable to a process unit such as a developing device, a cleaning unit, or an electrostatic charging unit, provided with no electrophotographic photosensitive member.  
      Also, although the photosensitive drum has been described as an example of the electrophotographic photosensitive member, it will be appreciated that the present invention is applicable not only to a drum shaped one but also to a belt shaped one.  
      While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.  
      This application claims priority from Japanese Patent Application No. 2003-434556 filed Dec. 26, 2003, which is hereby incorporated by reference herein.