Patent Publication Number: US-7224926-B2

Title: Flight developer regulating member, developing apparatus and method of assembling developing apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a flight developer regulating member, a developing apparatus and a method of assembling a developing apparatus preferably used in an image forming apparatus of an electrophotographic type or an electrostatic recording type. 
   2. Related Background Art 
   There has heretofore been adopted a process cartridge method whereby an electrophotographic photosensitive member, charging means, developing means, cleaning means, etc. are integrally made into a cartridge, which is made detachably mountable on an image forming apparatus main body. By this cartridge method, operability is more improved and it becomes possible for a user himself to easily effect the maintenance of the above-mentioned process means and therefore, this cartridge method is widely used in image forming apparatuses of the electrophotographic type. 
   As a developing method in such a process cartridge, there is a developing method whereby a developer carrying member and an image bearing member are in non-contact with each other and an AC electric field (oscillating electric field) is given to between the two to thereby effect developing. This method causes a developer flying from the developer carrying member to adhere to an electrostatic latent image formed on the image bearing member to thereby effect developing. In a case where the developer is thus caused to fly from the developer carrying member to the image bearing member, there has arisen the problem that even if a latent image which should be equal in density is formed on the moving image bearing member, more developer adheres to the rear end portion of the latent image. Thus, the density sometimes becomes high only on the rear end of the image, and in order to cope with a desire for a high quality of image required in recent years, a further improvement has come to be desired. 
   To solve this, there is known a method of providing a plate-shaped member in a developing area as shown in Japanese Patent Application Laid-Open No. H08-22185. 
   The plate-shaped member, however, is disposed in a minute interstice between the developer carrying member and the image bearing member and therefore, the fore end thereof must be attached with high accuracy, and this has led to the problem that much time is required for assembly, and a further improvement has been necessary. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a flight developer regulating member, a developing apparatus and a method of assembling a developing apparatus which regulate an area for a developer flying in the gap between an image bearing member and a developer carrying member. 
   It is another object of the present invention to provide a flight developer regulating member, a developing apparatus and a method of assembling a developing apparatus which prevent any density change from occurring to an image which should be equal in image density. 
   It is another object of the present invention to provide a flight developer regulating member, a developing apparatus and a method of assembling a developing apparatus which suppress the phenomenon that image density becomes high in the trailing edge portion of an image. 
   It is another object of the present invention to provide a flight developer regulating member which can be highly accurately and simply attached to a developing apparatus, a developing apparatus and a method of assembling a developing apparatus. 
   It is another object of the present invention to provide a flight developer regulating member, a developing apparatus and a method of assembling a developing apparatus which can improve the assembling property of the flight developer regulating member and the developing apparatus. 
   Further objects and features of the present invention will become more apparent from the following detailed description when read with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  are cross-sectional views showing an example of a developing apparatus according to the present invention. 
       FIG. 2  is a perspective view showing a method of assembling the developing apparatus according to the present invention. 
       FIG. 3  is a cross-sectional view showing a process cartridge according to the present invention. 
       FIG. 4  is a cross-sectional view showing the process cartridge according to the present invention. 
       FIGS. 5A and 5B  are perspective views showing the process cartridge according to the present invention. 
       FIG. 6  is a schematic perspective view showing the time when the process cartridge is mounted on an image forming apparatus main body according to the present invention. 
       FIG. 7  is an exploded perspective view showing the process cartridge according to the present invention. 
       FIGS. 8A and 8B  are exploded perspective views showing the process cartridge according to the present invention. 
       FIGS. 9A ,  9 B and  9 C are assembly illustrations showing the process partridge according to the present invention. 
       FIG. 10  is a perspective view showing the process cartridge according to the present invention. 
       FIGS. 11A ,  11 B and  11 C are illustrations of a developing blade. 
       FIG. 12  is an illustration of a supporting member which supports a flight developer regulating sheet. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Some embodiments of the present invention will be described with reference to the drawings. 
   An embodiment of a multi-color image forming apparatus which can use the developing apparatus of the present invention will first be described in detail with reference to the drawings. 
   &lt;General Construction of the Multi-Color Image Forming Apparatus&gt; 
   The general construction of the multi-color image forming apparatus will first be schematically described with reference to  FIG. 3 .  FIG. 3  is a longitudinal cross-sectional view showing the general construction of a full-color laser beam printer  100  which is an embodiment of the multi-color image forming apparatus. 
   The multi-color image forming apparatus  100  shown in  FIG. 3  is provided with photosensitive drums  1   a ,  1   b ,  1   c  and  1   d  which are four image bearing members juxtaposed in a vertical direction. Each photosensitive drum  1  is rotatively driven in a counter-clockwise direction in  FIG. 3  by driving means (not shown). Around the photosensitive drum  1 , there are disposed a charging device  2  ( 2   a ,  2   b ,  2   c ,  2   d ) which is charging means for uniformly charging the surface of the photosensitive drum  1 , a scanner unit  3  ( 3   a ,  3   b ,  3   c ,  3   d ) for applying a laser beam on the basis of image information to thereby form an electrostatic latent image on the photosensitive drum  1 , a developing apparatus  4  ( 4   a ,  4   b ,  4   c ,  4   d ) which is developing means for causing a toner which is a developer to adhere to the electrostatic latent image to thereby develop the latent image as a toner image, an electrostatic transferring device  5  for transferring the toner image on the photosensitive drum  1  to a transfer material S, a cleaning device  6  ( 6   a ,  6   b ,  6   c ,  6   d ) which is cleaning means for removing any untransferred toner residual on the surface of the photosensitive drum  1  after the transfer, etc. in the named order in the rotational direction of the photosensitive drum  1 . 
   Here, as shown in  FIG. 4 , the photosensitive drum  1 , the charging device  2 , the developing apparatus  4  and the cleaning device  6  are integrally made into a cartridge, and a process cartridge  7  is formed for each color. 
   Detailed description will hereinafter be made of in succession from the photosensitive drum  1 . 
   The photosensitive drum  1  is constituted by providing a photosensitive layer on the outer peripheral surface of e.g. an aluminum cylinder having a diameter of 24 mm. The photosensitive drum  1  has its opposite end portions rotatably supported by supporting members, and a driving force is transmitted from a drive motor (not shown) to one end portion thereof, whereby the photosensitive drum is rotatively driven in a counter-clockwise direction. 
   As the charging device  2 , use can be made of one of a contact charging type. A charging member is an electrically conductive roller formed into a roller shape, and this roller is brought into contact with the surface of the photosensitive drum  1  and a bias voltage is applied to this roller to thereby uniformly charge the surface of the photosensitive drum  1 . In the present embodiment, use is made of a reversal developing system, and the surface of the photosensitive drum  1  is charged to the minus polarity. 
   The scanner unit  3  is such that by a laser diode (not shown), image light corresponding to an image signal is applied to a polygon mirror  9  ( 9   a ,  9   b ,  9   c ,  9   d ) rotated at a high speed by a scanner motor (not shown). Design is made such that the charged surface of the photosensitive drum  1  is selectively exposed to the image light reflected by the polygon mirror through an imaging lens  10  ( 10   a ,  10   b ,  10   c ,  10   d ) to thereby form an electrostatic latent image. 
   The developing apparatus  4  is provided with toner containing portions containing yellow, magenta, cyan and black toners, respectively, therein, and feeds the toners in a developing container unit  4  which is the developing apparatus onto a toner supplying roller  43  by a feeding mechanism  42 . 
   The toner supplying roller  43  is rotated in a clockwise direction Z as viewed in  FIG. 4 , and effects the supply of the toner to a developing sleeve  40  which is a developer carrying member, and the stripping of the toners after the developing on the photosensitive drum  1  has been effected from the developing sleeve  40 . The developing sleeve  40  is of the shape of a hollow cylinder formed of aluminum or the like. 
   The toner supplied to the developing sleeve  40  is applied to the outer periphery of the developing sleeve  40  rotated in the clockwise direction as viewed in  FIG. 4  by a developing blade  44  which is a developer layer regulating member brought into pressure contact with the outer periphery of the developing sleeve  40 , and have minus charges imparted thereto. The developing blade  44  regulates the thickness of the developer layer on the developing sleeve  40 . 
   A developing bias is then applied to the developing sleeve  40  opposed to the photosensitive drum  1  on which the latent image has been formed, whereby the latent image on the photosensitive drum  1  is developed. In the present embodiment, use is made of a reversal developing process in which the charging polarity of the photosensitive drum  1  and the charging polarity of the toners are the same. 
   The electrostatic transferring device  5  has disposed therein an electrostatic conveying belt  11  opposed to all the photosensitive drum  1   a ,  1   b ,  1   c ,  1   d  and circulatively moved so as to contact therewith. As the electrostatic conveying belt  11 , use is made of resin film or a multi-layer film-like member comprising a rubber base layer and a resin layer provided thereon. This electrostatic conveying belt  11  is passed over a drive roller  13 , driven rollers  14   a ,  14   a  and a tension roller  15 , and is circulatively moved so as to electrostatically attract the transfer material S to the left outer peripheral surface thereof as viewed in  FIG. 3  and bring the transfer material S into contact with the photosensitive drum  1 . Thereby, the transfer material S is conveyed to a transferring position by the electrostatic conveying belt  11  and has the toner image on the photosensitive drum  1  transferred thereto. 
   Transfer rollers  12  ( 12   a ,  12   b ,  12   c ,  12   d ) are juxtaposed at positions in contact with the inside of this electrostatic conveying belt  11  and opposed to the four photosensitive drums  1   a ,  1   b ,  1   c ,  1   d . A bias of the plus polarity is applied to these transfer rollers  12  during transfer, and charges of the plus polarity are applied to the transfer material S through the electrostatic conveying belt  11 . By an electric field produced at this time, the toner image of the minus polarity on the photosensitive drum  1  is transferred to the transfer material S which is in contact with the photosensitive drum  1 . 
   A sheet feeding portion  16  serves to feed and convey the transfer material S to an image forming portion, and a plurality of transfer materials S are contained in a sheet supplying cassette  17 . During image formation, a sheet feeding roller  18  (halfmoon-shaped roller)  18  and registration rollers  19  are rotatively driven in conformity with an image forming operation to thereby separate and feed a sheet of transfer material S in the sheet supplying cassette  17 , and the leading edge of the transfer material S strikes against the registration rollers  19  and the transfer material S is once stopped thereby and forms a loop, whereafter it is fed to the electrostatic conveying belt  11  by the registration rollers  19  in synchronism with the rotation of the electrostatic conveying belt  11  for an image writing-out start position. 
   A fixing portion  20  serves to fix the toner images of plural colors transferred to the transfer material S, and comprises a rotated heating roller  21   a  and a pressure roller  21   b  brought into pressure contact therewith for applying heat and pressure to the transfer material S. 
   That is, the transfer material S to which the toner images on the photosensitive drums  1  have been transferred is conveyed by the pressure roller  21   b  and is given heat and pressure by the heating roller  21   a  when it passes through the fixing portion  20 . Thereby, the toner images of plural colors are fixed on the surface of the transfer material S. 
   As the image forming operation, the process cartridges  7   a ,  7   b ,  7   c ,  7   d  are successively driven by the main body of the image forming apparatus in timed relationship with printing, and in conformity with the driving, the photosensitive drums  1   a ,  1   b ,  1   c ,  1   d  are rotatively driven in a counter-clockwise direction as viewed in  FIG. 3 . The scanner units  3  corresponding to the respective process cartridges  7  are then successively driven. By this driving, the charging roller  2  imparts uniform charges to the peripheral surface of the photosensitive drum  1 , and the scanner unit  3  effects exposure on the peripheral surface of the photosensitive drum  1  in conformity with an image signal to thereby form an electrostatic latent image on the peripheral surface of the photosensitive drum  1 . The developing sleeve  40  in the developing apparatus  4  causes the toner to shift to the low potential portion (light portion) of the electrostatic latent image to thereby form (develop) a toner image on the peripheral surface of the photosensitive drum  1 . 
   At the timing whereat the leading edge of the toner image of the photosensitive drum  1  which is most upstream with respect to the electrostatic conveying belt  11  is rotatively conveyed to a point opposed to the electrostatic conveying belt  11 , the registration rollers  19  start rotation and feed the transfer material S to the electrostatic conveying belt  11  so that the printing start position of the transfer material S may coincide with the opposed point. 
   Design is made such that the transfer material S is brought into pressure contact with the outer periphery of the electrostatic conveying belt  11  in such a manner as to be nipped between an electrostatic attracting roller  22  and the electrostatic conveying belt  11 , and a voltage is applied to between the electrostatic conveying belt  11  and the electrostatic attracting roller  22  to thereby induce charges in the dielectric material layer of the transfer material S and the electrostatic conveying belt  11  which are dielectric materials, and electrostatically attract the transfer material to the outer periphery of the electrostatic conveying belt  11 . Thereby, the transfer material S is stably attracted to the electrostatic conveying belt  11  and is conveyed to the transferring portion most downstream with respect to the movement direction of the electrostatic conveying belt  11 . 
   The transfer material S has the toner images on the respective photosensitive drums  1  successively transferred thereto by an electric field formed between the respective photosensitive drums  1  and the transfer rollers  12  while being thus conveyed. 
   The transfer material S to which the toner images of four colors have been transferred is curvature-separated (self-stripped) from the electrostatic conveying belt  11  by the curvature of the belt driving roller  13  and is conveyed into the fixing portion  20 . The transfer material S has the toner images thereon heat-fixed by the fixing portion  20 , and thereafter is discharged from a sheet discharging portion  24  to the outside of the main body by discharge rollers  23  with its image surface facing down. 
   &lt;Construction of the Process Cartridge&gt; 
   The process cartridge according to the present embodiment will now be described in detail with reference to  FIGS. 4 ,  5 A,  5 B and  6 .  FIGS. 4 ,  5 A,  5 B and  6  show the main cross section and perspective views of the process cartridge  7  containing the toner therein. The yellow, magenta, cyan and black process cartridges  7   a ,  7   b ,  7   c  and  7   d  are of the same construction. 
   The process cartridge  7  is divided into the electrophotographic photosensitive drum  1  which is an image bearing member, a cleaner unit  50  provided with charging means and cleaning means, and the developing unit  4  having developing means for developing the electrostatic latent image on the photosensitive drum  1 . The process cartridge  7  can be provided with at least one of the charging means, the developing means and the cleaning means, and the photosensitive drum  1 . 
   The cleaner unit  50  of  FIG. 4  is such that the photosensitive drum  1  is rotatably mounted on a cleaning frame member  51  through a bearing member. On the periphery of the photosensitive drum  1 , there are disposed in contact therewith the charging roller  2  for uniformly charging the photosensitive layer provided on the outer periphery of the photosensitive drum  1 , and a cleaning blade  60  and a flexible sheet member  80  for removing any developer (residual developer) residual on the photosensitive drum  1  after transfer. The residual toner (waste toner) removed from the surface of the photosensitive drum  1  by the cleaning blade  60  is contained in a waste toner chamber  55  provided rearwardly of the cleaning frame member. Also, the untransferred residual toner on the drum passes through that portion of the flexible sheet member  80  which is contact with the drum and arrives at the position of the cleaning blade  60 , and the contact condition of the flexible sheet member  80  with the drum is set so that the residual toner removed from the drum by the cleaning blade  60  may not leak to the outside of the cleaning frame member  51 . 
   The developing unit  4  is provided with the developing sleeve  40  keeping a minute gap between it and the photosensitive drum  1  and rotated in the direction of arrow Y, and developing frame members  45   a  and  45   b  constituting a toner containing portion containing the toner therein. 
   The developing frame members  45   a  and  45   b  are coupled together (coupled together by ultrasonic welding or the like) to thereby provide the developing container unit  4 . 
   The developing sleeve  40  is rotatably supported in the developing container unit  4  through a bearing member, and a toner supplying roller  43  rotated in the direction of arrow Z and the developing blade  44  are disposed on and in contact with the periphery of the developing sleeve  40 . Further, in the developing container unit  4 , there is provided a toner conveying mechanism  42  for agitating the toner contained in the developing container unit  4  and conveying it to the toner supplying roller  43 . 
   The developing container unit  4  is of suspended structure in which the entire developing unit  4  is supported for rocking movement relative to the cleaner unit  50  by coupling holes  47  formed in the end portions of the developing container unit  4  and supporting holes  52  and  53  (see  FIGS. 5A and 5B ) formed in the opposite ends of the cleaning frame member  51  of the cleaner unit  50  being aligned with each other, and a pin  49  being inserted thereinto from the opposite ends of the cleaner unit  50 . 
   Also, the developing unit  4  is always biased by a pressure spring so that the developing sleeve  40  may go toward the photosensitive drum  1  about a supporting hole (not shown). During development, the toner contained in the toner containing portion is carried to the toner supplying roller  43  by the toner agitating mechanism  42 . The toner supplying roller  43  rotated in the direction of arrow Y supplies the toner to the developing sleeve  40  by the frictional contact thereof with the developing sleeve  40  rotated in the direction of arrow Z, and causes the toner to be carried on the developing sleeve  40 . 
   The toner carried on the developing sleeve  40  comes to the position of the developing blade  44  with the rotation of the developing sleeve  40 , and the developing blade  44  regulates the amount of toner to thereby form a predetermined thin toner layer, and a desired amount of charging charge is imparted thereto. The toner made into a thin layer on the developing sleeve  40  is carried to a developing area in which the photosensitive drum  1  and the developing sleeve  40  are proximate to each other with the rotation of the developing sleeve  40 , and in the developing area, the toner adheres to the electrostatic latent image formed on the surface of the photosensitive drum  1 , by a developing bias applied from a voltage source, not shown, to the developing sleeve  40 , to thereby develop the latent image. As the developing bias, use was made of a DC bias of −260V superimposed on an AC peak-to-peak voltage of 2 kV and an AC bias of an AC frequency of 3 kHz. The waveform of the developing bias is set so as to intersect with both of the value of the dark portion surface potential of the photosensitive drum  1  and the value of the light portion surface potential of the photosensitive drum  1 , whereby an alternate electric field is formed between the developing sleeve  40  and the photosensitive drum  1 . Between the developing sleeve  40  and the photosensitive drum  1 , there is provided a gap in the developing area, and in this gap, the toner flies from the developing sleeve  40  to the drum  1  by the formed alternate electric field. In the present embodiment, the gap between the developing sleeve  40  and the photosensitive drum  1  is 280 μm. 
   The toner which has not contributed to the developing of the electrostatic latent image and is residual on the surface of the developing sleeve  40  is returned into the developing device with the rotation of the developing sleeve  40 , and is stripped and collected from the developing sleeve  40  by the frictional contact portion thereof with the toner supplying roller  43 . The collected toner is agitated and mixed with the remaining toner by the toner agitating mechanism  42 . 
   &lt;Method of Detachably Mounting the Process Cartridge on the Image Forming Apparatus Main Body&gt; 
   A method of detachably mounting the process cartridge  7  on the image forming apparatus main body  100  will now be described with reference to  FIG. 6 . As shown in  FIG. 6 , a front door  101  is provided on the image forming apparatus main body  100 , and is provided for pivotal movement relative to the main body  100 . 
   Also, the electrostatic transferring device  5  is pivotably provided at the back of the front door  101 . With the front door  101  and the electrostatic transferring device  5  opened relative to the apparatus main body  100 , the process cartridges  7  of the four colors become detachably mountable on the image forming apparatus main body  100 . Handle members  90  are provided near the photosensitive drum supporting portions at the opposite end portions of the process cartridge  7 , and protrude to the front door side of the main body during the mounting and dismounting of the cartridge. 
   The process cartridge  7  become detachably mountable on the image forming apparatus main body  100  by a guide rail portion (not shown) provided in the image forming apparatus main body  100  and an insertion guide portion (not shown) provided on the process cartridge  7  being engaged with each other. 
   &lt;Developer Layer Regulating Member&gt; 
   The construction of the developing blade which is a developer layer regulating member in the developing unit which is the developing apparatus and the surroundings thereof will now be described with reference to  FIGS. 7 to 10  and  11 A to  11 C. 
   The developing blade  44  is provided with a regulating portion formed of an elastic material such as rubber or a thin metal for regulating the thickness of a layer of developer carried on the developing sleeve  40 , and a regulating portion supporting member formed of a metal for supporting the regulating portion. In the present embodiment, a phosphor bronze plate which is a metal plate is used as the regulating portion. 
   The developing blade  44 , near the longitudinal opposite end portions thereof, is fixed to the developing frame member  45  by screws  71  and  72  ( FIGS. 7 ,  8 A,  8 B and  10 ). The regulating portion supporting member of the developing blade is a metal plate and it is difficult for the distortion thereof due to fixing to occur and therefore, it is desirable in positional accuracy to reliably fix it to the developing frame member by screws which are fastening members. 
   The developing frame member  45  is provided with a first flat surface  45   e  which is a flat surface parallel to the developing sleeve  40 , positioning portions  45   c  and  45   d  provided protrudingly from the first flat surface  45   e , a second flat surface  45   f  differing from the first flat surface  45   e , and a positioning portion  45   b  provided protrudingly from the second flat surface  45   f.    
   As shown in  FIGS. 7 ,  8  and  9 , in the contact portion between the developing blade  44  and the developing sleeve  40 , the position of the developing blade  44  relative to the tangential direction (a direction orthogonal to the longitudinal direction of the blade) of the developing sleeve  40  is determined by the positioning portions  45   c  and  45   d , and the position of the developing blade  44  relative to the longitudinal direction of the developing sleeve  40  is determined by the positioning portion  45   b.    
   The supporting member of the developing blade  44  is formed with U-shaped grooves  44   c  and  44   d  in the longitudinal end portions thereof, and in the present embodiment, a laterally U-shaped groove  44   b  is disposed in a surface orthogonal thereto. 
   By these positioning portions, the developing blade  44  is positioned relative to the developing frame member  45 , as shown in  FIG. 11A . 
   By adopting this construction, it becomes possible for the fixing screw  71  and the positioning portion  45   c  to become proximate to each other, and this leads to a construction leading to the downsizing of the apparatus. 
   In contrast, a conventional popular positioning method is shown in  FIGS. 11B and 11C . In a case where as shown in  FIG. 11B , an attempt is made to position developing blades  144  and  244  by the round-shaped boss of the developing frame member, if for example, positioning bosses are disposed in the developing frame member as indicated at  145   c  and  145   d , a space indicated by a width V will become necessary in a longitudinal end portion of the blade in  FIG. 11B . Also, if as shown in  FIG. 11C , for example positioning bosses are disposed in the developing frame member as indicated at  245   c  and  245   d , a space indicated by Y will become necessary in an end portion in the width direction (a direction orthogonal to the longitudinal direction) of the blade in  FIG. 11C . 
   As shown in  FIG. 11A , however, the construction of the developing blade  44  in the present embodiment is adopted, whereby these spaces become unnecessary and the downsizing of the apparatus becomes possible. 
   Description will now be made of a method of assembling the developing apparatus. 
   In the present embodiment, as shown in  FIG. 8B , slopes  45   c - 2  are provided on the positioning portion  45   c  of the developing frame member, and these are set so that as shown in  FIG. 9B , during assembly, the developing blade  44 , even if somewhat inclined, may be easily inserted owing to the presence of a gap E. Also, the assembly of the developing blade to the developing frame member is set so that the fitting of the positioning portion  45   b  and the laterally U-shaped groove  44   b  may begin earlier, and then the fitting of the positioning portion  45   c  and the U-shaped groove  44   c  may be completed. That is, the length E indicated in  FIG. 8A  is set so that as shown in  FIG. 9A , a gap C may exist even if a fitting length D occurs. Also, during assembly, as shown in  FIG. 9A , a gap A is provided between the developing blade  44  and the developing frame member  45 , and the relation between the gap A and a gap B between the positioning portion  45   c  and the portion  44   c  indicated in  FIG. 9A  is rendered into A&lt;B, whereby even if A=0 during assembly, the slopes  45   c - 2  are provided so that the portions  45   c  and  44   c  may easily fit to each other. 
   Description will now be made of the relation between the screws and the positioning portions. 
   The developing blade, near the longitudinal opposite end portions thereof, has its supporting member for supporting the regulating portion fixed to the developing frame member by the screws which are fastening members. The positioning portion  45   c  has areas  44   c - 1  and  45   c - 1  hidden by screwing ( FIG. 8B ). These areas are constituted by a surface  45   c - 1  lower by a step in height than the surrounding surface so that the bearing surfaces of the screws may be fastened in contact with the developing blade  44 . By adopting such a construction, the screws are fastened in the area  44   c - 1 , and the fixing of the developing blade  44  is effected properly and accurately. Also, the presence of the surface  45   c - 1  makes it possible to secure the fitting length (longitudinal direction) of  45   c  and  44   c  more greatly by an amount indicated by W. 
   &lt;Flight Developer Regulating Member&gt; 
   Description will now be made of a regulating member for regulating the reciprocal moving area of the developer in the developing area (hereinafter referred to as the flight developer regulating member in order to clearly distinguish from the developer layer regulating member). 
   The flight developer regulating member in the present embodiment is shown in  FIGS. 1A ,  1 B,  2  and  3 .  FIG. 1B  is an enlarged view of the portion  1 -B of  FIG. 1A . 
   The flight developer regulating member is provided with a flight developer regulating sheet  91  for regulating an area in which the developer flies, and a regulating sheet supporting member  90  for supporting this regulating sheet  91 . The regulating sheet  91  is fixed to the developing blade  44  which is a developer layer regulating member through the regulating sheet supporting member  90 . As shown in  FIGS. 1A and 1B , a space defined by the developing blade, the developing sleeve and the photosensitive drum is narrow, and it becomes spatially advantageous to downsizing to provide the flight developer regulating member in this space and therefore, it is better to mount the flight developer regulating member on the developing blade than to mount it on the developing frame member. Also, the upper side of the developing frame member is an optical path for applying light for image forming, and an attempt to mount the flight developer regulating member on the developing frame member hinders the optical path. However, mounting the flight developer regulating member on the developing blade does not hinder the space on the upper side of the developing frame member and is therefore advantageous. 
   As the flight developer regulating sheet  91 , use is made, for example, of an insulative flexible resin sheet, which is an insulative or electrically floating member. 
   The flight developer regulating sheet  91  regulates a portion of the developing area upstream of the drum  1  with respect to the rotational direction thereof. When the rotation of the drum  1  is stopped and the developing operation is performed after such a latent image as assumes maximum image density has been formed on the drum, in a case where the regulating sheet  91  is provided, the toner adhering range in the rotational direction of the drum  1  becomes small as compared with a case where the regulating sheet  91  is not provided. As described above, the flight developer regulating sheet  91  is provided at such a position as regulates a portion of the developing area. The regulating sheet  91  is provided so as to contact with the photosensitive drum  1  and not to contact with the developer carried on the developing sleeve. The regulating sheet  91  is inserted into the narrow gap between the photosensitive member and the developing sleeve and therefore, the positional accuracy thereof becomes important. 
   The free end of the flight developer regulating sheet  91  is inserted into the upstream side in the developing area with respect to the direction of movement of the photosensitive drum  1 , whereby such a phenomenon as sweeping-together in which density becomes high only in the trailing edge of an image such as a solid image (maximum density image) can be suppressed. The phenomenon of this sweeping-together is also described in U.S. 2005-0008401 A, but will hereinafter be described. 
   Sweeping-together is the phenomenon that much toner gathers on the trailing edge of an image. When an oscillating electric field is formed between the photosensitive drum and the developing sleeve by a developing bias, a barrel-shaped electric field is produced between the photosensitive drum and the developing sleeve in the developing area because the two are of an arcuate shape. Thereupon, the toner adhering to the surface of the developing sleeve reciprocally moves between the photosensitive drum and the developing sleeve along an electric line of force formed by the electric field and therefore, moves toward the outside of the most proximate point between the photosensitive drum and the developing sleeve. When the toner reciprocally moves, the photosensitive drum is being rotated and therefore, the toner is gathered toward the upstream side of the photosensitive drum. That is, when an AC bias is applied, the toner in the developing area always comes to have a speed component moving toward the upstream side outside the developing area. Thereby the phenomenon of sweeping-together occurs. 
   In a construction wherein an electrode is provided on the flight developer regulating sheet to thereby effect the supply of electric power, a strong electrostatic force comes to work between the electrode and the developing sleeve, and together with the vibration of the flight developer regulating sheet, an increase in a developing sound is great, and chatter is liable to occur in the portion of contact with the photosensitive drum and the portion of contact with the developing sleeve. When chatter occurs, the developer goes round onto that surface of the flight developer regulating sheet which is opposed to the photosensitive drum, and the sweeping-together image preventing effect decreases, and this is not preferable. Therefore, as in the present embodiment, no electrode is provided on the flight developer regulating sheet. Or even if an electrode is present, a construction in which it does not supply electric power and it is electrically floated is more preferable. 
   The supporting member  90  is positioned by positioning bosses  44   j  provided on the portions of the developing blade  44  which are near the longitudinal opposite end portions of the supporting member, and the contact between the two is effected on that surface of the developing sleeve  40  which contacts with the developing blade. As another embodiment, instead of providing the positioning bosses  44   j , the position of the supporting member  90  may be determined by the use of a jig (not shown) and the supporting member may be attached to the developing sleeve  40 . In this case, if the reference of the jig is made coincident with the reference position (not shown) of the developing frame member, positioning can be effected accurately. In the present embodiment, a two-side adhesive coated tape  92  is used for a fixing method, but an adhesive agent or a screw is usable. However, that portion of the flight developer regulating member which is fixed to the developing blade and the photosensitive member are proximate to each other and therefore, the use of the adhesive agent is more advantageous than using the screw for fixing. This is because the use of the screw is spatially disadvantageous since the head portion of the screw protrudes, and the proximity of the head portion of the screw to the photosensitive member may sometimes disturb the latent image. The space defined by the developing blade and the photosensitive member is originally narrow and therefore, in a case where the flight developer regulating member is mounted on the developing blade, it is more preferable to use the adhesive agent than to use the screw. 
   In a case where a two-side adhesive coated tape or an adhesive agent are used for fixing, in order to prevent the inclination of the supporting member  90 , the supporting member must be attached to a range within an area Y indicated in  FIG. 1B  so as to avoid a position at which the thin-walled portion (phosphor bronze in the present embodiment) of the developing blade  44  begins to flex when the developing roller  40  is mounted. 
   Also, when the photosensitive drum  1  has been mounted, in order to prevent the supporting member  90  and the regulating sheet  91  from sandwiching the two-side adhesive coated tape at the corners thereof, and the fore end position thereof becoming irregular even if the flight developer regulating sheet  91  contacts with the photosensitive drum  1 , whereby the flight developer regulating sheet  91  is flexed, the width X 1  of the two-side adhesive coated tape is made smaller than the width X 2  of the flat portion of the supporting member, as shown in  FIG. 1B , to thereby achieve the stabilization of the fore end position. 
   Also, as shown in  FIGS. 1A and 2 , the flight developer regulating sheet  91  is positioned by being rammed against a highly accurate surface  90   f  provided on the supporting member  90 . The fore end (free end side) of the regulating sheet is brought into contact with the photosensitive drum, and it is in such a positional relation that it enters to the order of 1 mm from the surface of a virtual photosensitive drum in a state in which the photosensitive drum has been removed. 
   By doing so, there is the effect that the supporting member  90  and the developing blade  44  can obtain accurate and stable positions. 
   In the present embodiment, polyethylene terephthalate resin is selected as the flight developer regulating sheet  91 . Also, polystyrene resin is used for the supporting member  90 , and an aperture through which the attached surface of the developing blade  44  and the positioning bosses  44   j  fit to each other, and a supporting surface  90   g  for supporting the regulating sheet  91  are highly accurately molded by injection molding. This is because a developing bias is applied to the developing blade  44  and an electrically insulative material is used as the material of the flight developer regulating sheet  91  so that the developing bias may not leak to the photosensitive drum  1 . 
   The flight developer regulating sheet  91 , as shown in  FIG. 1A , is mounted at an angle α with respect to a line (indicated as the tangent of the photosensitive drum in  FIG. 1A ) orthogonal to a line passing through the center of rotation of the photosensitive drum  1  which is an image bearing member and the center of rotation of the developing sleeve  40  which is a developer carrying member. This means that an optimum angle is selected to prevent the flight developer regulating sheet  91  from vibrating and producing a noise during development. The angle α is such that on the aforementioned orthogonal line (tangent), with a line upstream of the line passing through the aforementioned centers of rotation with respect to the rotational direction of the photosensitive drum as the reference, a direction pivotally moving to the developing sleeve side is defined as plus, and a direction pivotally moving to the photosensitive drum side is defined as minus. 
   Here, in the case of α=0° (the case of being orthogonal), the noise is highest, and the thinner is the flight developer regulating sheet  91 , the higher is the noise. In the present embodiment, in order to avoid this, the thickness of the flight developer regulating sheet  91  is selected to 20 μm to 200 μm, and the angle α is selected to a range of +1° to 45° to thereby obtain the effect of reducing the noise. A greater thickness is advantageous against the noise, but increases the probability with which the photosensitive drum is injured (Table 1). Accordingly, the aforementioned thickness is selected within a range which will not frictionally injure the photosensitive drum, and further, in order that burr formed by the severing of the flight developer regulating sheet  91  during manufacture may not contact with the photosensitive drum, the sheet  91  is attached so that of the sides of the flight developer regulating sheet  91 , that side on which the burr is formed may be the developing roller side. Also, the aforementioned angle is determined in view of the limitation of the space and a reduction in the noise. 
   
     
       
         
             
             
           
             
                 
               TABLE 1 
             
             
                 
                 
             
           
          
             
                 
               Relation between 
             
             
                 
               Noise and Thickness 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
          
             
                 
               thickness 
               small 
               → 
               great 
             
             
                 
               noise 
               great 
                 
               small 
             
             
                 
                 
             
          
         
         
             
             
          
             
                 
               Relation between 
             
             
                 
               Angle and Noise 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
          
             
                 
               angle 
               +45° 
               → 
               0° 
             
             
                 
               noise 
               small 
               → 
               great 
             
             
                 
                 
             
          
         
       
     
   
   When the angle α assumes the negative direction (−α), the supporting member  90  becomes too proximate to the photosensitive drum  1 , and this has been unsuitable from the viewpoint of space. 
   A fixing end portion which is a first portion (first side) of the supporting member for the flight developer regulating member is attached to the blade for regulating the developer layer on the developer carrying member, whereby an end portion which is a second portion (second side) of the supporting member for the flight developer regulating member is provided upstream of the line passing through the center of rotation of the image bearing member and the center of rotation of the developer carrying member with respect to the rotational direction of the developer carrying member (or the image bearing member), i.e., on the left side in the plane of the drawing sheet of  FIG. 1A . In the present embodiment, the aforedescribed first portion is that portion of the supporting member  90  which is mounted on the developing blade, and the aforedescribed second portion is that portion of the supporting member  90  which supports the regulating sheet  91 . 
   A method of assembling the flight developer regulating member will now be described with reference to  FIG. 2 . 
   After the developing blade  44  has been mounted on the developing frame member  45 , the developing roller  40  is mounted on the developing frame member  45 . Thereafter, the supporting member  90  is attached to a regulating portion surface  44   s  by means of a two-side adhesive coated tape  92 , and lastly the flight developer regulating sheet  91  is rammed against the ramming portion  90   f  of the supporting member  90  and is attached to the supporting surface  90   g  thereof. By doing so, it is possible for a worker to assemble accurately even when he manually assembles, and there is the effect that manufacture becomes possible at a low cost. In the present embodiment, as the regulating portion, use is made of a phosphor bronze plate which is a metal plate. 
   Also, as another embodiment, after the flight developer regulating sheet  91  has been attached to the supporting member  90 , the supporting member  90  may be attached to the regulating portion surface  44   s  of the developing blade  44  by means of a two-side adhesive coated tape. Particularly in this case, the regulating sheet  91  and the supporting member  90  can be made into a unit, and the attachment of the regulating sheet  91  and the supporting member  90  can be effected easily. Also, in the present embodiment, in order to prevent the wrinkling or waving of the regulating sheet  91 , when the regulating sheet is to be attached to the supporting member  90 , the supporting member  90  is warped so that tension may be applied to the regulating sheet  91  after attached. If with the regulating sheet  91  attached to the supporting member  90 , the free end side of the regulating sheet  91  is accurately cut relative to the reference of the supporting member  90 , whereafter the supporting member is attached to the regulating portion surface  44   s  of the developing blade  44 , the positional accuracy of the fore end will be good. Also, the regulating sheet  91  and the supporting member  90  are formed of resin and are thin and therefore, are liable to be distorted and thus, when the supporting member  90  is to be fixed to the blade, it is preferable to secure it not by screwing, but by a two-side adhesive coated tape or the like. This is because if screwing is used, the vicinity of the fixed portion becomes liable to be distorted. Thus fixing the flight developer regulating member to the developing blade by adhesively securing is preferable for the purpose of improving the positional accuracy of the flight developer regulating member in the developing area. 
   Also,  FIG. 12  shows another embodiment of the supporting member  90 . When the regulating sheet  91  is to be attached to the supporting member  90 , tension is applied to the regulating sheet  91  as described above, but near the longitudinal end portions of the regulating sheet  91 , tension is not sufficiently applied but wrinkles or waving may sometimes occur and therefore, in order to prevent this, it is preferable to construct the supporting member  90  as follows. 
   The fixed surface of the supporting member  90  is provided with a first fixed surface  90   a  fixed to the developing blade, second fixed surfaces  90   b  having a level difference relative to the first fixed surface  90   a  and fixed to the developing blade, and slopes  90   c  which are fixed surfaces linking the first fixed surface  90   a  and the second fixed surfaces  90   b  together. In  FIG. 12 , apertures formed in the second fixed surfaces  90   b  are apertures into which the positioning bosses  44   j  are fitted. 
   After the regulating sheet  91  has been attached to the supporting member  90  and tension has been applied thereto, the supporting member  90  is mounted on the developing blade  44  by the first fixed surface  90   a , the slopes  90   c  and the second fixed surfaces  90   b  opposed to the surface of the developing blade  44 , through a two-side adhesive coated tape. The second fixed surfaces  90   b  formed on the opposite end portions of the supporting member  90  are formed lower by a step than the first fixed surface  90   a , and the first fixed surface  90   a  and the second fixed surfaces  90   b  are smoothly connected together by the slopes  90   c . Specifically, the second fixed surfaces  90   b  are formed lower by 0.2 mm than the first fixed surface  90   a . In other words, the first fixed surface  90   a  is provided more protrudingly than the second fixed surfaces  90   b . By adopting such a construction, when the two-side adhesive coated tape is attached to the first fixed surface  90   a , the slopes  90   c  and the second fixed surfaces  90   b , and the supporting member  90  is brought into close contact with the surface of the developing blade, the opposite end portions of the supporting member  90  are arcuately warped and as the result, tension is applied to the end portions of the flight developer regulating sheet  91 , whereby the wrinkling and waving of the end portions of the flight developer regulating sheet  91  can be prevented from occurring. That is, the wrinkling and waving caused by the regulating sheet  91  being flexible and very thin can be prevented. When such wrinkling and waving occur, the regulating sheet  91  may contact with the developing sleeve to thereby disturb the toner layer carried on the developing sleeve. Particularly, the gap between the photosensitive member and the developing sleeve is as narrow as 280 μm and therefore, the positional accuracy of the regulating sheet  91  inserted between the photosensitive member and the developing sleeve is important. In the present embodiment, in  FIG. 12 , in the longitudinal direction of the supporting member  90 , the length of the entire supporting member is 225.4 mm, the length of each of the second fixed surfaces  90   b  is 19.6 mm, and the sum of the length of the second fixed surfaces  90   b  and the length of the slopes  90   c  is 24.6 mm. Also, in  FIG. 12 , the width of the supporting member  90  in a direction h is 4.7 mm. It is also preferable to make the first fixed surface, the slopes and the second fixed surfaces into a curved surface as a whole to thereby flex the supporting member  90  when it is attached to the developing blade. 
   While in the present embodiment, the supporting member  90  is attached to the regulating portion  44   s  of the blade, instead it is also possible to attach the supporting member  90  to the supporting member of the blade. 
   Also, while in the above-described embodiment, the developing sleeve is used as the developer carrying member, instead it is also possible to use a developing roller provided with a mandrel and rubber provided on the mandrel. 
   Further, as the image bearing member, a dielectric member can also be used instead of the photosensitive member, and the shape thereof is not limited to a drum shape, but use can also be made of a belt-shaped member. 
   This application claims priority from Japanese Patent Application Nos. 2004-104633 filed on Mar. 31, 2004 and 2005-071278 filed on Mar. 14, 2005, which are hereby incorporated by reference herein.