Abstract:
The present invention relates to a seal member contacted with a rotatable body for sealing a developer borne on the rotatable body which has a surface layer contacted with the rotatable body, wherein the seal member&#39;s surface layer includes felt. The surface layer has a first portion formed by a plurality of fibers being intertwined, and a second loop portion in which the fibers are raised in a loop shape.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a developing apparatus which can be used in an image forming apparatus such as an electrophotographic apparatus, and to a developer sealing member which can be used in the developing apparatus. 
     2. Related Background Art 
     An electrophotographic image forming apparatus, such as a printer, effects selective exposure on an image bearing body (photosensitive drum) uniformly charged by a charging device to thereby form a latent image, and visualizes the latent image with a developer (toner) by a developing device and transfers the image by the developer to a recording medium to thereby effect image recording. After the transfer, any developer remaining on the image bearing body is removed by a cleaning blade and the removed developer is stored in a cleaning container and the next development is effected by the image bearing body, the surface of which is clean. 
     In recent years, there has been put into practical use an apparatus in which the image bearing body, the charging device, the developing device, the cleaning portion, the waste toner box, etc. are collected into an integral structure and made into a cartridge, whereby a user loads the main body of the apparatus with the cartridge to enable the interchange of the parts of the developer image bearing body and thereby facilitate the maintenance thereof. 
     Further, when the life of the image bearing body extends and the number of printable sheets is increased, the developing device, which is otherwise limited in its supplying capability, is made into an independent unit. The apparatus is divided into the developing unit and a drum unit comprising the image bearing body, the charging device and the cleaning portion integral as image forming process means. Like the process cartridge, the mounting and maintenance of the main body of the apparatus are simplified, and the way of use conforming to the lives of the main parts has come to be adopted. In this drum unit, the waste toner produced by cleaning is stored in the cleaning container having a volume capable of being sufficiently contained in the life of the image bearing body, and is removed during the interchange of the drum unit. 
     In recent years, the demand for color electrophotographic image forming apparatuses capable of effecting the formation color images has been increasing. There is known, for example, a construction in which developing devices  105 M,  105 C,  105 Y and  105 K of four colors are all disposed in a rotary (for example, U.S. Pat. No. 4,707,108, U.S. Pat. No. 5,040,031, etc.). 
     Such a construction is very effective for forming colored images. 
     On the other hand, the future color electrophotographic image forming apparatus for copying with a network needs to cope with a large-quantity high-speed output irrespective of the propriety of the output of a color document. It is also desirable to reduce the cost per page to the level in a monochromatic electrophotograhic image forming apparatus. 
     To cope with such a desire, it is necessary to lengthen the lives of expendables used in this apparatus (such as the developing unit and the image bearing body unit which is the drum unit, or a process cartridge comprising the developing unit and the image bearing body unit constructed integrally with each other). 
     The developing unit is generally provided with developer sealing members on the opposite end portions of a developing roller. 
     The conventional developer sealing members, however, cannot sufficiently cope with the lengthening of the lives in some cases, and there has been a case where the developer (toner) leaks to the outside of the developer sealing members and contaminates the interior of the apparatus. 
     Also, in a situation in which the leakage of the developer occurs, the toner may adhere to a portion in which the developer sealing members are in close contact with a cylindrical member (such as the image bearing body or the developing roller (developing means)). Thus, there has arisen a case where the rotational torque of the cylindrical member becomes great and the load to the driving motor in the main body of the apparatus increases and stable operation cannot be accomplished. 
     SUMMARY OF THE INVENTION 
     The present invention is the further development of the above-described prior art and a main object thereof is to provide a developer sealing member which can improve a developer catching capability and can prevent the outflow of the developer. 
     Another main object of the present invention is to provide a developing apparatus provided with a developer sealing member which can improve the developer catching capability and can prevent the outflow of the developer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a color laser printer according to an embodiment of the present invention. 
     FIG. 2 is a cross-sectional view of the surroundings of a black developing unit in the embodiment. 
     FIG. 3 is an enlarged cross-sectional view of the black developing unit in the embodiment. 
     FIG. 4 is a front view of the black developing unit in the embodiment. 
     FIG. 5 is a main cross-sectional view of the black developing unit in the embodiment. 
     FIG. 6 is a side view of the black developing unit in the embodiment. 
     FIG. 7 is an exploded perspective view of a toner containing portion in the black developing unit in the embodiment. 
     FIG. 8 is a perspective view of the toner containing portion in the black developing unit in the embodiment. 
     FIG. 9 is a perspective view of a portion of the black developing unit in the embodiment. 
     FIG. 10 is an illustration of an opening seal member in the embodiment. 
     FIG. 11 is a front view of a toner containing portion provided with the opening seal member shown in FIG.  10 . 
     FIG. 12 is an illustration of another opening seal member in the embodiment. 
     FIG. 13 is a front view of a toner containing portion provided with the opening seal member shown in FIG.  12 . 
     FIG. 14 is an illustration of still another opening seal member in the embodiment. 
     FIG. 15 is a front view of a toner containing portion provided with the opening seal member shown in FIG.  14 . 
     FIG. 16 is a cross-sectional view of a developing portion frame in the black developing unit in the embodiment. 
     FIG. 17 is an enlarged cross-sectional view showing the manner of assembling an agitating member in the black developing unit in the embodiment. 
     FIG. 18 is an enlarged cross-sectional view showing the manner of assembling the agitating member in the black developing unit in the embodiment. 
     FIGS. 19A and 19B are illustrations of a toner sealing member in the embodiment. 
     FIG. 20 is an illustration of the working of the toner sealing member in the embodiment. 
     FIG. 21 is an enlarged perspective view of the black developing unit in the embodiment. 
     FIG. 22 is a joint cross-sectional view of a black developing unit according to the prior art. 
     FIG. 23 is a joint cross-sectional view of the black developing unit in the embodiment. 
     FIG. 24 is an illustration of the opening of an opening seal member according to the prior art. 
     FIG. 25 is an illustration of the opening seal member in the embodiment. 
     FIG. 26 is a pictorial perspective view of the black developing unit in the embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A color electrophotographic image forming apparatus according to the present invention will hereinafter be described with reference to the drawings. 
     Description of the Whole of the Image Forming Apparatus 
     The general construction of the color electrophotographic image forming apparatus will first be schematically described with reference to FIG.  1 . 
     FIG. 1 is an illustration of the general construction of a laser beam printer which is a form of the color toner image forming apparatus. 
     The image forming portion of the color laser beam printer is provided with an image bearing body (photosensitive drum (cylinder member))  15  as an electrophotographic photosensitive body rotatable at a constant speed, a fixed type black developing unit  21 B and three rotatable color developing units (a yellow developing unit  20 Y, a magenta developing unit  20 M and a cyan developing unit  20 C). 
     Below the image forming portion, there is disposed an intermediate transfer body  9  holding a developed and multiplexly transferred color toner image thereon and further transferring it to a recording medium  2  fed from a feeding portion. 
     The recording medium  2  to which the color toner image has been transferred is conveyed to a fixing portion  25 , whereby the color toner image is fixed on the recording medium  2 , which is then discharged to a discharging portion  37  on the upper surface of the apparatus by discharge rollers  34 ,  35  and  36 . The recording medium is, for example, a sheet of paper or an overhead projector sheet or the like. 
     The rotatable color developing units  20 Y,  20 M,  20 C and the fixed type black developing units  21 B are individually detachably attachable to the main body  100  of the printer (i.e., the main body of the image forming apparatus). Also, a sheet feeding roller  3 , a feeding roller  4 , a double feeding preventing retard roller  5 , a feeding guide  6 , a conveying roller  7 , registration rollers  8  and discharge rollers  34 ,  35 ,  36  together constitute conveying means  70 . 
     The construction of each portion of the image forming apparatus will now be described in detail. 
     Image Bearing Body Unit 
     A drum unit  13  as a process cartridge is such that the image bearing body  15 , a cleaning device provided with a cleaning member (cleaning blade)  16 , a charging device provided with a charging member (charging means)  17 , and the cleaner container  14  of the cleaning device serving also as a holder for the image bearing body  15  are constructed integrally with one another. This drum unit  13  is horizontally inserted into a unit containing portion through a mounting port, not shown, provided in the main body  100  of the printer, and is made detachably attachable to a mounting guide (not shown) as mounting means provided in the unit containing portion. Accordingly, the drum unit  13  can be easily detached with respect to the main body  100  of the printer by a user, and is interchanged when the image bearing body  15  has reached the end of its life. 
     The image bearing body  15  according to the present embodiment is such that an organic photoconductive material layer is applied to the outer side of the aluminum cylinder, which has a diameter of about 62 mm. It is rotatably supported on the container  14  of the cleaning device serving also as the holder for the image bearing body  15 . 
     The cleaner blade  16  as the cleaning member and the primary charging means  17  as the charging member are disposed along the peripheral surface of the image bearing body  15 . 
     Also, a driving motor, not shown, is disposed on one rear end of the image bearing body  15 . By the driving force of this motor being transmitted, the image bearing body  15  is rotated counter-clockwise in conformity with the image forming operation. 
     The cleaner blade  16  abuts against the image bearing body  15 , and removes any toner remaining on the surface of the image bearing body  15  after the toner image has been transferred. 
     Charging Means 
     The charging means  17  uses a contact charging method. A charging roller, e.g. an electrically conductive roller, as the charging member, is made to abut against the image bearing body  15 . 
     By applying a voltage to this charging roller, the surface of the image bearing body  15  is uniformly charged. 
     Exposure Means 
     The exposure to the image bearing body  15  is effected from a laser scanner portion  30 . That is, when an image signal is given to a laser diode (not shown), this laser diode applies a light  18  corresponding to the image signal to a polygon mirror  31 . 
     This polygon mirror  31  is rotated at a high speed by a scanner motor  31   a,  and the light  18  reflected by the polygon mirror  31  selectively exposes the surface of the image bearing body  15  rotated at a constant speed via an imaging lens  32  and a reflecting mirror  33 . As a result, an electrostatic latent image conformity to image information is formed on the image bearing body  15 . 
     Developing Mechanism 
     The developing mechanism of the present embodiment is provided with three rotatable developing units  20 Y,  20 M,  20 C and a black developing unit  21 B which enable the development of yellow, magenta, cyan and black in order to visualize the electrostatic latent image. 
     During color image formation, a developing rotary  23  rotates for each one full rotation of the intermediate transfer body  9 . The developing steps are carried out in the order of the yellow developing unit  20 Y, the magenta developing unit  20 M, the cyan developing unit  20 C and lastly the black developing unit  21 B. 
     Color Developing Units 
     Each of the three rotatable developing units  20 Y,  20 M and  20 C contains therein a toner corresponding in quantity to about 7000 images (A4 size, print percentage of 4%). They are detachably attachably held on the developing rotary  23  as holding means rotated about a rotary shaft (hereinafter referred to as the shaft)  22 . On this developing rotary  23 , there is provided a mounting guide (not shown) as mounting means for detachably mounting the rotatable developing units  20 Y,  20 M and  20 C. In case of image formation, the developing units  20 Y,  20 M and  20 C are rotatively moved about the shaft  22  while being held on the developing rotary  23 . A predetermined one of the developing units  20 Y,  20 M and  20 C is stopped at a position opposed to the image bearing body  15 . 
     During color toner image formation, the developing rotary  23  is rotated for each one full rotation of the intermediate transfer body  9  and the developing steps are carried out in the order of the yellow developing unit  20 Y, the magenta developing unit  20 M, the cyan developing unit  20 C and the black developing unit  20 B. The developer of the developing unit of each color is a non-magnetic monocomponent developer. 
     FIG. 2 shows a state in which the yellow rotatable developing unit  20 Y rests at a position opposed to the image bearing body  15 . The rotatable developing unit  20 Y feeds a yellow toner (yellow developer) in the container to an applying roller  20 YR by a feeding member  20 YT. 
     The yellow toner is applied in the form of a thin layer to the outer periphery of a developing roller  20 YS rotated clockwise by the applying roller  20 YR rotated clockwise and a developing blade  20 YB urged against the outer periphery of a developing roller (cylinder member)  20 YS as developing means, and charges are imparted (frictional charging) to the yellow toner. 
     A developing bias is applied to the developing roller  20 YS opposed to the image bearing body  15  on which the latent images have been formed, whereby a yellow toner image is formed on the image bearing body  15  in conformity with the latent image. With respect also to the magenta developing unit  20 M and the cyan developing unit  20 C, toner development of each color is effected by a mechanism similar to what has been described above. 
     The yellow developing unit  20 Y has the applying roller  20 YR, the developing blade  20 YB, the developing roller  20 YS and a yellow toner containing portion  20 YG containing a yellow toner therein. Likewise, the magenta developing unit  20 M has an applying roller  20 MR, a developing blade  20 MB, a developing roller  20 MS and a magenta toner containing portion MG containing a magenta toner therein. Also, the cyan developing unit  20 C has an applying roller  20 CR, a developing blade  20 CB, a developing roller  20 CS and a cyan toner containing portion CG containing a cyan toner therein (see FIG.  1 ). 
     Also, the developing rollers  20 YS,  20 MS and  20 CS in the rotatable developing units  20 Y,  20 M and  20 C, respectively, are connected to respective high voltage sources for color development and driving portions (none of these being shown) provided in the main body  100  of the printer when the developing units  20 Y,  20 M and  20 C have been rotatively moved to the developing position. A voltage is selectively applied to each of the color developing units  20 Y,  20 M and  20 C and the drive is connected. 
     Intermediate Transfer Body 
     The intermediate transfer body  9  receives the multiplex transfer of the toner images on the image bearing body  15  visualized by the respective developing units  20 Y,  20 M and  20 C four times (the images of four colors Y, M, C and B) during the color toner image forming operation. Therefore, it is rotated clockwise in synchronism with the outer peripheral velocity of the image bearing body  15  (see FIG.  1 ). 
     Also, the intermediate transfer body  9  which has received the multiplex transfer conveys the recording medium  2  while sandwiching the recording medium  2  between the intermediate transfer body  9  and the transfer roller  10 , to which a voltage has been applied, whereby the respective color toner images on the intermediate transfer body  9  are multiplexly transferred to the recording medium  2  at a particular time. 
     The intermediate transfer body  9  according to the present embodiment comprises an aluminum cylinder  12  having a diameter of 186 mm and an elastic layer  11  of medium resistance sponge, medium resistance rubber or the like covering the outer periphery thereof. This intermediate transfer body  9  is driven and rotated by a gear (not shown) rotatably supported on and fixed integrally with the main body  100  of the printer. 
     Cleaning Means 
     The cleaning means removes any toner remaining on the image bearing body  15  after the toner images visualized on the image bearing body  15  by the developing rollers (developing means)  20 YS,  20 MS,  20 CS and  21 BS of the developing units  20 Y,  20 M,  20 C and  21 B, respectively have been transferred to the intermediate transfer body  9 . Thereafter, the removed toner is stored in the cleaner container  14 . This cleaner container  14  can contain therein removed toner more than will be generated during the life (about 50,000 images) of the image bearing body  15 . 
     Accordingly, when the image bearing body  15  reaches the end of its life, the cleaner container  14  is interchanged with it. In the present embodiment, a cleaning blade  16  is used as the cleaning member. This cleaning blade  16  abuts against the surface of the image bearing body  15 . 
     Sheet Feeding Portion 
     The sheet feeding portion feeds the recording medium  2  to the image forming portion, and as shown in FIG. 1, it is comprised chiefly of a sheet feeding cassette  1  containing a plurality of recording mediums  2  therein, a feeding roller  3 , a feeding roller  4 , a double feeding preventing retard roller  5 , a feeding guide  6 , a conveying roller  7  and registration rollers  8 . 
     During image formation, the feeding roller  3  is rotatively driven in response to the image forming operation and separates and feeds the recording mediums  2  in the sheet feeding cassette  1  one by one and also, the recording medium is guided by the feeding guide plate  6  and comes to the registration rollers  8  via the conveying roller  7 . 
     During the image forming operation, the registration rollers  8  perform the non-rotating operation of making the recording medium  2  reset and wait and the rotating operation of conveying the recording medium  2  toward the intermediate transfer body  9 , at a predetermined sequence, and effects the alignment between the toner image and the recording medium  2  during the transferring step, which is the next step. 
     Secondary Transfer Portion 
     The secondary transfer portion, as shown in FIG. 1, is provided with a transfer belt  10  pivotally movable as a transfer member. The transfer belt  10  is a belt having its surface layer formed of rubber of high resistance (the surface resistance being 10 9  to 10 13  Ω), and is vertically pivotally movable and rotatable. 
     During the time when the toner images on the intermediate transfer body  9  are being formed, i.e., during the time when the intermediate transfer body  9  is rotated a plurality of times, the transfer belt  10  is positioned below and spaced apart from the intermediate transfer body  9  as indicated by solid line so as not to disturb the images. 
     Specifically, during the time when toner images of four colors are being formed on the intermediate transfer body  9 , i.e., during the time when the intermediate transfer body  9  is rotated a plurality of times, the transfer belt  10  is downwardly retracted relative to the intermediate transfer body  9  so as not to disturb those toner images. 
     After the toner images of four colors have been formed on the intermediate transfer body  9 , the transfer belt  10  is urged against the intermediate transfer body  9  with predetermined pressure with the recording medium  2  interposed therebetween at an upper position indicated by thin line by a cam member, not shown, in synchronism with the timing at which the color toner images are transferred to the recording medium  2 . At the same time, a bias is applied to the transfer belt  10  and therefore, the toner images on the intermediate transfer body  9  are transferred to the recording medium  2 . 
     Each of the intermediate transfer body  9  and the transfer belt  10  is driven. Therefore, the recording medium  2  sandwiched between the two is subjected to the transferring step and at the same time, it is conveyed to the left (as viewed in FIG. 1) at a predetermined speed and is conveyed toward a heating and fixing device, which is the next step. 
     Fixing Portion 
     The toner images formed on the image bearing body  15  by the respective developing rollers (developing means)  20 YS,  20 MS,  20 CS and  21 BS of the developing units  20 Y,  20 M,  20 C and  21 B are transferred onto the recording medium  2  through the intermediate transfer body  9 . The heating and fixing device  25  melts and mixes the toner images transferred onto the recording medium  2  by the use of heat and fixes the toner images on the recording medium  2 . 
     As shown in FIG. 1, the heating and fixing device  25  is provided with a fixing roller for applying heat to the recording medium  2  and a pressing roller  27  for urging the recording medium  2  against the fixing roller  26 , and the rollers  26  and  27  are hollow rollers. They have heaters  28  and  29  therein. They are rotatively driven to thereby convey the recording medium  2  at the same time. 
     That is, the recording medium  2  holding the toner image thereon is conveyed by the fixing roller  26  and the pressing roller  27  and has heat and pressure imparted thereto, whereby the toner image is fixed on the recording medium  2 . 
     Black Developing Unit 
     The black developing unit  21 B in the present embodiment is detachably fixed to and mounted in the main body  100  of the printer. That is, the black developing unit  21 B is horizontally inserted into a unit containing portion through a mounting port provided in the main body  100  of the printer, and is detachably supported relative to a mounting guide (not shown) as mounting means provided in the unit containing portion. The black developing unit  21 B has a toner containing portion  21 BG as a developer containing portion containing a black toner therein, and the developing roller  21 BS (see FIG.  2 ). 
     As shown in FIG. 2, the black developing unit  21 B feeds the toner in the container into a first agitating portion  21 BM by the second feeding member  21 BU of a second agitating portion  21 BN, and feeds the toner toward the developing roller  21 BS by a first feeding member  21 BT through an opening portion  21 BA. The toner is applied to the outer peripheral surface of the developing roller  21 BS by an applying blade (applying means)  21 BB urged against the outer periphery of the developing roller  21 BS and imparts charges (frictional charging) to the toner (see FIGS.  2  and  3 ). 
     A developing bias is applied to the developing roller  21 BS to thereby effect reversal developing (jumping developing) correspondingly to the electrostatic latent image on the image bearing body  15 , thus forming a toner image by the black toner on the surface of the image bearing body  15 . 
     Spacer rollers  21 BK are coaxially disposed on the opposite end portions of the developing roller  21 BS of the black developing unit  21 B, as shown in FIG. 21, and the outer diameter of the spacer rollers  21 BK is slightly greater than the outer diameter of the developing roller  21 BS. 
     These spacer rollers  21 BK bear against the outer peripheral surface of the image bearing body  15 , whereby the developing roller  21 BS secures a minute interval (of the order 300 μm) relative to the image bearing body  15 . 
     A toner image by the black toner is formed correspondingly to the electrostatic latent image on the image bearing body  15 . The construction in which a minute interval is provided between the image bearing body  15  and the developing roller  21 BS is similarly present in the other colors. 
     The toner capacity of the black developing unit  21 B, with the amount of toner consumption taken into account, corresponds to 17000 images (A4 size, 4%) which is approximately double the toner capacity of the other rotatable developing units  20 Y,  20 M and  20 C. 
     Also, the installed position of the black developing unit  21 B is between a laser scanner portion  30  which is an exposure device and the rotatable developing units  20 Y,  20 M,  20 C, as shown in FIG.  1 . 
     By so disposing the black developing unit  21 B, even if the toners leak when the rotatable developing units  20 Y,  20 M and  20 C are rotated, the toners are prevented from scattering to optical parts such as the laser scanner portion  30 , etc. 
     Thus, the toners are prevented from adhering to a polygon mirror  31 , an imaging lens  32 , a reflecting mirror  33 , etc. and thereby hampering the latent image formation, and a clear output image can be obtained. 
     Measures for Preventing the Adherence of Floating Toners to the Bottom of the Toner Containing Portion 
     The black developing unit  21 B, as shown in FIGS. 1 and 2, is mounted in the main body  100  of the printer and the bottom  21 BG 1  of the toner containing portion  21 BG thereof is opposed to the developing rotary  23 . Therefore, color toners scattering from the developing units  20 M,  20 Y and  20 C held by the developing rotary  23  and floating in the main body  100  of the printer may adhere to the bottom  21 BG 1  of the black developing unit  21 B. 
     Thus, in the present embodiment, as shown in FIGS. 2 and 4, a cover sheet  21 BR which is a low resistance member is adhesively secured to the bottom surface of the bottom  21 BG 1  of the toner containing portion  21 BG. In the present embodiment, the cover sheet  21 BR is formed of a super-high molecular polyethylene sheet material having surface resistance 10 6  Ω or less (specifically, surface resistivity of 10 13  Ω/sq. or less). 
     The cover sheet  21 BR is of low resistance and therefore its surface is not significantly charged. Also, it is formed of a sheet material of a low coefficient of friction, such as a super-high molecular polyethylene sheet material, and therefore is excellent in the slipping property of its surface. By these two characteristics, the adherence of the color toners floating in the main body  100  of the printer is prevented. 
     Thus, the adherence of the color toners to the bottom  21 BG 1  of the toner containing portion  21 BG can be prevented and therefore, there can be realized a black developing unit  21 B excellent in usability. 
     Although not shown, the cover sheet  21 BR is formed with an aperture in least one location. By virtue of the cover sheet  21 BR being formed with an aperture in at least one desired location as described above, the air in the space of the housing of the cover sheet  21 BR and the toner containing portion  21 BG can be drawn out when the cover sheet  21 BR is adhered to the bottom  21 BG 1  of the toner containing portion  21 BG, and the cover sheet  21 BR can be prevented from being wrinkled during the adhesive securing thereof. Also, the air in the space of the housing of the cover sheet  21 BR and the toner containing portion  21 BG can be prevented from being expanded by temperature rise to thereby inflate the cover sheet  21 BR. 
     Construction of the Housing of the Black Developing Unit 
     The black developing unit  21 B, as shown in FIG. 23, comprises a toner containing portion  21 BG and a developing portion frame  21 BL coupled together by an ultrasonic joining method. 
     A projected portion  62  is formed on a portion of the developing portion frame  21 BL, and the projected portion  62  bears against the bottom surface  63   a  of a recess  63  formed in a portion of the housing of the toner containing portion  21 BG. 
     When in this state, a portion of the housing of the toner containing portion  21 BG is held by a pedestal  61  and a portion of the developing portion frame  21 BL is pressed and vibrated by a horn  60 , the projected portion  62  is melted in the recess  63 , and the toner containing portion  21 BG and the developing portion frame  21 BL are joined together. 
     The conventional ultrasonic joining method for the toner containing portion  21 BG and the developing portion frame  21 BL will now be described with reference to FIG.  21 . 
     As shown in FIG. 22, the toner containing portion  21 BG and the developing portion frame  21 BL have been ultrasonically joined together, in a state in which when on a blow-out preventing sheet  21 BF side provided on the developing portion frame  21 BL, the distance between the inner end  60   a   1  of a close contact area  60   a  in which a horn  61  is in close contact with the developing portion frame  21 BL and the projected portion  62  of the developing portion frame  21 BL is defined as B and the distance between the outer end  60   a   2  of the close contact area  60   a  in which the horn  61  is in close contact with the developing portion frame  21 BL and the projected portion  62  of the developing portion frame  21 BL is defined as A, B and A are adjusted so that B≧A, and in a state when on the side opposite to the blow-out preventing sheet  21 BF of the developing portion frame  21 BL, the distance between the inner end  60   b  of a close contact area  60   b  in which the horn  61  is in close contact with the developing portion frame  21 BL and the projected portion  62  of the developing portion frame  21 BL is defined as B and the distance between the outer end  61   b   2  of the close contact area  60   b  in which the horn  61  is in close contact with the developing portion frame  21 BL and the projected portion  62  of the developing portion frame  21 BL is defined as A, B and A are adjusted so that B&lt;A. 
     In such an ultrasonic joining method, however, the moment M of the distance B by the pressing force (distribution load) of the horn  60  in the close contact areas  60   a  and  60   b  of the developing portion frame  21 BL is great as compared with the moment (not shown) of the distance A and therefore, the housing of the developing portion frame  21 BL is deformed inside an opening indicated by arrow A. As a result, the blow-out preventing sheet (blow-out preventing means)  21 BF strongly abuts against the developing roller  21 BS, not shown, and scrapes off a part of the black toner applied to the developing roller  21 BS. This causes either the floating of the black toner or an uneven image to occur in the portion wherein the blow-out preventing sheet strongly abuts against the developing roller  21 BS. 
     So, in the present embodiment, when the toner containing portion  21 BG and the developing portion frame  21 BL are to be joined together, when, as shown in FIG. 23, the distance between the inner end  60   a   1  of the close contact area  60   a  in which the horn  60  is in close contact with the developing portion frame  21 BL and the projected portion  62  is defined as B, and the distance between the outer end  60   a   2  of the close contact area  60   a  in which the horn  60  is in close contact with the developing portion frame  21 BL and the projected portion  62  is defined as A, B and A are adjusted so that B&lt;A. 
     By effecting the adjustment of the joint as previously described, the warp of the developing portion frame  21 BL can be made small. That is, in the ultrasonic joining method according to the present embodiment, the moment M of the distance A by the pressing force (distribution load) of the horn  60  in the close contact area  60   a  of the developing portion frame  21 BL becomes great as compared with the moment (not shown) of the distance B. Therefore, it can be corrected for the housing of the developing portion frame  21 BL to be deformed toward the inside of an opening indicated by arrow A in FIG.  23 . As a result, the warp of the blow-out preventing sheet  21 BF adhesively secured to the developing portion frame  21 BL becomes small and the blow-out preventing sheet  21 BF can be made to stably abut against the developing roller  21 BS. 
     Thereby, it becomes possible to effect the stable application of the black toner to the developing roller  21 BS, and both the occurrence of the floating or scattering of the black toner by the blow-out preventing sheet  21 BF scraping off part of the black toner applied to the developing roller  21 BS and the occurrence of an uneven image in the portion wherein the blow-out preventing sheet  21 BF strongly abuts can be suppressed. 
     The aforedescribed joining method can also be suitably applied to the yellow developing unit  20 Y, the magenta developing unit  20 M and the cyan developing unit  20 C. 
     Supporting Structure for the Agitating Member of the Developing Portion 
     Also, as shown in FIGS. 2,  3  and  5 , an agitating member (developer agitating member)  21 BH and a rotatable member  21 BI are disposed in the developing portion  21 BV. The agitating member  21 BH in the present embodiment, as shown in FIG. 16, has one end portion  21 BH 1  thereof supported in an aperture  21 BC in the developing portion frame  21 BL, and has the other end portion  21 BH 2  thereof supported in an aperture  21 BI 1  in the rotatable member  21 BI. The agitating member  21 BH is fixed against axial movement relative to the rotatable member  21 BI. 
     Specifically, as shown in FIG. 18, a portion  21 BH 2   a  of the other end portion  21 BH 2  of the agitating member  21 BH is pressed and thickened, and this thick portion  21 BH 2   a  is forced into the aperture  21 BH 1  in the rotatable member  21 BI. In the present embodiment, the height dimension D of the thick portion  21 BH 2   a  of the agitating member  21 BH and the diameter H of the aperture  21 BI 1  in the rotatable member  21 BI are in the dimensional relation that D−H≧0.1 mm. 
     By adopting the above-mentioned dimensional relation, the pull strength of the agitating member  21 BH relative to the rotatable member  21 BI can be 500 gf. 
     On the other hand, the aperture  21 BC in the developing portion frame  21 B is of a tapered shape as shown in FIG. 17 so that one end portion  21 BH 1  of the agitating member  21 BH may not slide. Specifically, the taper angle is α≧2° with respect to the peripheral surface of one end portion  21 BH 1  of the agitating member  21 BH. 
     Also, in the present embodiment, when the depth of the aperture  21 BC in the developing portion frame  21 BL is defined as L 1  and the length of the straight portion of one end portion  21 BH 1  of the agitating member  21 BH is defined as L 2 , L 2 &gt;L 1 . By adopting such a dimensional relation, the bend root  21 BH 3  of one end portion  21 BH 1  of the agitating member  21 BH is prevented from axially interfering with the entrance of the aperture in the developing portion frame  21 BL. 
     Also, the entrance of the aperture  21 BC in the developing portion frame  21 BL is chamfered at  21 BC 1  and is made to escape more positively relative to the bend root  21 BH 3  of the agitating member  21 BH so that the interference with the bend root  21 BH 3  of the agitating member  21 BH may not occur. 
     In the agitating member  21 BH in the present embodiment, a stopper  21 BJ as an anti-slippage member is held on the inner side of the rotatable member  21 BI so that the agitating member may not fall off the developing portion frame  21 BL after the assembly thereof. 
     As described above, in the agitating member supporting structure according to the present embodiment, the agitating member  21 BH is fixed against axial movement relative to the rotatable member  21 BI and therefore, the axial reciprocal movement of the agitating member  21 BH can be suppressed. Thus, it never happens that the black toner is positively forced into the aperture  21 BC in the developing portion frame  21 BL. 
     Also, the aperture  21 BC in the developing portion frame  21 BL is provided with a taper angle of 2° or greater with respect to the peripheral surface of one end portion  21 BH 1  of the agitating member  21 BH. Therefore, with the rotating operation of the agitating member  21 BH, the black toner can be discharged from the aperture  21 BC. Moreover, the circumferential surface of one end portion  21 BH 1  of the agitating member  21 BH is not in surface contact with the aperture  21 BC and therefore, the adherence of the black toner to the inner surface of the aperture  21 BC can be reduced. 
     Also, since the dimensional relation between the depth L 1  of the aperture  21 BC in the developing portion frame  21 BL and the length L 2  of the straight portion of one end portion  21 BH 1  of the agitating member  21 BH is L 2 &gt;L 1 , it can be avoided for the bend root  21 BH 3  of the agitating member  21 BH to axially interfere with the entrance of the aperture  21 BC in the developing portion frame  21 BL, and such a situation that the black toner adheres to the entrance of the aperture  21 BC in the developing portion frame  21 BL can be prevented. 
     The aforedescribed agitating member supporting structure can also be suitably applied to the yellow developing unit  20 Y, the magenta developing unit  20 M and the cyan developing unit  20 C. 
     In the present embodiment, the aperture  21 BC is formed in the developing portion frame  21 BL to support one end portion  21 BH 1  of the agitating member  21 BH. However, as an alternative to the aperture  21 BC, a groove can be formed in the developing portion frame  21 BL to thereby support one end portion  21 BH 1  of the agitating member  21 BH. 
     Measure for Catching the Toner in the Developing Portion 
     Also, in the developing portion  21 BV, as shown in FIGS. 2,  3  and  5 , there are disposed, besides the agitating member  21 BH, the developing roller  21 BS, the applying blade  21 BB, an openable shutter (protective member)  21 BO for protecting the developing roller  21 BS, etc. The shutter  21 BO, as shown in FIGS. 4,  6  and  26 , is openably supported on the developing portion frame  21 BL through a shutter shaft  21 BQ, and is opened to thereby expose the developing roller  21 BS when the black developing unit  21 B is mounted in the main body  100  of the printer, and is closed to thereby protect the developing roller  21 BS when the black developing unit  21 B is detached from the main body  100  of the printer. 
     In the present embodiment, as shown in FIG. 3, a magnet sheet  42  as developer catching means is disposed within 15 mm from the surface of the developing roller  21 BS. It can be mounted by being adhesively secured, for example, to a portion of the developing portion frame  21 BL, a portion of the shutter  21 BO or a portion of the applying blade  21 BB. 
     The full length of the magnet sheet  42  is longer than the application area (coat length) of the black toner applied onto the developing roller  21 BS. Also, the magnet sheet  42  is disposed parallel to the axis of the developing roller  21 BS. 
     By so disposing the magnet sheet  42 , the toner floating from the developing roller  21 BS (the toner floating around the developing roller  21 BS) can be positively caught (captured) by the utilization of the adsorbing action by the magnetic force of the magnet sheet  42 . Thereby, the stains of the housing of the black developing unit  21 B by the black toner and the contamination of the outer surface of the drum unit  13  disposed near the black developing unit  21 B can be prevented. 
     By so disposing the magnet sheet  42  as developer catching means in the developing portion  21 BV, the black toner can be prevented from adhering to the other areas other than the developing portion  21 BV. 
     Measure for Reducing the Toner Pressure to an Opening Seal Member by Falling (1) 
     The toner containing portion  21 BG, as shown in FIG. 7, is formed with upper and lower opening portions  21 BA, and the upper opening portion  21 BA is sealed with a lid  21 BD joined thereto, and the lower opening portion  21 BA is sealed with an opening seal member  43  adhesively secured thereto. 
     The direction of detachment of the black developing unit  21 B relative to the main body  100  of the printer is the same as the lengthwise direction of the black developing unit  21 B (the axial direction of the developing roller  21 BS). 
     Just above the lower opening portion  21 BA, there is provided a partition member  44  which partitions the interior of the toner containing portion  21 BG into a plurality of containing chambers. This partition member  44  includes a first partition wall  44 A extending in the direction of detachment of the black developing unit  21 B relative to the main body  100  of the printer, and a plurality of second partition walls  44 B extending in a direction perpendicular to the direction of detachment of the black developing unit  21 B relative to the main body  100  of the printer. 
     The first partition wall  44 A of the partition member  44  is formed so that the wall surface thereof may be larger than the opening area of the lower opening portion  21 BA (see FIG.  5 ). 
     Also, the first partition wall  44 A is disposed so that, as shown in FIG. 5, the wall surface thereof may have an angle of inclination of 30° or less (in the present embodiment, an angle of inclination of about 15°) with respect to the adhesively secured surface of the opening seal member  43  and have an angle of inclination of 65° or less (in the present embodiment, an angle of inclination of about 55°) with respect to the horizontal plane H of the main body  100  of the printer. 
     The first partition wall  44 A is formed and disposed in the toner containing portion  21 BG as described above and thus, the black toner trying to be moved toward the opening seal member  43  side by the shock or vibration to the black developing unit  21 B during shipment impinges on the wall surface of the first partition wall  44 A, whereby the movement of the black toner toward the opening seal member  43  side can be blocked by the first partition wall  44 A. 
     Thereby, the powder pressure to the opening seal member  43  by the black toner can be reduced and the breakage or the like of the opening seal member  43  by the powder pressure of the black toner can be suitably prevented. 
     Also, the plurality of second partition walls  44 B of the partition member  44  are provided in the toner containing portion  21 BG in a direction perpendicular to the direction of detachment of the black developing unit  21 B relative to the main body  100  of the printer. Therefore, the black toner can be distributed to the toner containing chambers among the second partition walls  44 B, and the inclination of the black toner in the toner containing portion  21 BG can be reduced. 
     Measure for Reducing the Toner Pressure to the Opening Seal Member by Falling (2) 
     Also, a first agitating portion  21 BM and a second agitating portion  21 BN are in the interior of the toner containing portion  21 BG, and a first feeding member  21 BT and a second feeding member  21 BU are rotatably supported on the respective agitating portions  21 BM and  21 BN. 
     In the present embodiment, the endmost portion of the second feeding member  21 BU in the direction of rotational radius thereof is stopped so as to be opposed to the tip end portion of the first partition wall  44 A of the partition member  44  (see FIG.  5 ). 
     Further, the first feeding member  21 BT and the second feeding member  21 BU are provided with a phase difference of an angle of rotation of about 90° (specifically, 90°±15°). Particularly, the first feeding member  21 BT is stopped at a position rotated by about 90° toward the upstream side relative to the second feeding member  21 BU. 
     In a factory, the first feeding member  21 BT and the second feeding member  21 BU are adjusted to the previously described stopped positions and are shipped. 
     As described above, the second feeding member  21 BU is stopped so that the embodiment portion thereof may be opposed to the tip end portion of the first partition wall  44 A, and the second feeding member  21 BU is stopped with its phase of rotation shifted to the upstream side of about 90° relative to the first feeding member  21 BT. Therefore, in the toner containing portion  21 BG, a substantially meandering space portion is formed by the first partition wall  44 A, the second feeding member  21 BU and the first feeding member  21 BT. Thus, the black toner trying to be moved toward the opening seal member  43  side by the shock or vibration to the black developing unit  21 B during shipment impinges on the first partition wall  44 A, the second feeding member  21 BU or the first feeding member  21 BT, and the movement of the black toner toward the opening seal member  43  side can be blocked by the first partition wall  44 A, the second feeding member  21 BU and the first feeding member  21 BT. 
     The driving shafts  21 BW of the first feeding member  21 BT and the second feeding member  21 BU, as shown in FIG. 7, are inserted into a side aperture  21 BG 1  in the toner containing portion  21 BG with oil seals  21 BE. The first and second feeding members  21 BT and  21 BU are driven and rotated by the driving shafts  21 BW. 
     Construction of the Opening Seal Member 
     The opening seal member  43  is constructed as a toner sealing member comprising, as shown in FIGS. 7 and 8, film  43 A as a first sheet member covering (sealing) the lower opening portion  21 BA of the toner containing portion  21 BG in a hermetically sealed state, and a tape  43 B which is a flexible member as a second sheet member, the film  43 A and the tape  43 B being heat-welded together as a unit. The film  43 A utilizes a uniaxial oriented film material or a sheet material having a tearing property in one direction. For example, use is made of uniaxial oriented polyethylene, uniaxial oriented polypropylene, uniaxial oriented foamed polypropylene or the like. 
     Also, the tape  43 B must have sufficient strength to tear the film  43 A, and should desirably have tensile strength about three times as great as the film  43 A. As the material of the tape  43 B, use is made, for example, of film or a sheet material of biaxial oriented polypropylene, polystyene, biaxial oriented poypropylene, polystyrene, biaxial oriented nylon or the like. 
     The film  43 A and the tape  43 B, as shown in FIG. 10, are joined together by a rectangular joint portion (first joint portion)  45  of which the four sides along the lower opening portion  21 BA of the toner containing portion  21 BG are continuous, and the free end side of the tape  43 B is turned back to the film  43 A. When the turned-back free end side of the tape  43 B is pulled, the film  43 A is torn in a predetermined direction while keeping the width of the tape  43 B. 
     In the present embodiment, besides the rectangular joint portion  45  comprising the four sides, a joint portion (second joint portion)  46  joined in a spot-like fashion to the vicinity of the turned-back portion  43 B 1  of the tape  43 B is discontinuously provided on the film  43 A and the tape  43 B, as shown in FIGS. 10,  11  and  25 . By this second joint portion  46 , an unjoined blank portion  43 A 1  created near the turned-back portion  43 B 1  of the film  43 A shown in FIG. 24 when the tape  43 B is torn can be prevented from being folded doubly or trebly. 
     Thereby, the tape  43 B can be pulled out smoothly without being caught on the way, and the lower opening portion  21 BA of the toner containing portion  21 BG can be stably opened. 
     In FIG. 11, the reference numeral  47  designates an adhesively securing area for adhesively securing the film  43 A to the toner containing portion  21 BG. 
     Now, comparing the amounts of tensile extension of the film  43 A and the tape  43 B with each other, the film  43 A is greater in extensibility than the tape  43 B. When for example, the black developing unit  21 B is made to fall, the black toner inclines in the container and, by its powder pressure, the opening seal member  43  is inflated. The greater the amount of inflation, the more the fracture of the film  43 A can be suppressed. 
     In the present embodiment, as shown in FIGS. 12 and 13, the corner portion at which the adjacent two sides of the rectangular joint portion  45  intersect is formed into an arcuate joint portion  45   a.  Even if, by the shock or vibration or the like during shipment, the powder pressure of the black toner acts on the film  43 A, the arcuate joint portions  45   a  become liable to be inflated in the direction in which the powder pressure of the toner acts, and the amount of stretch in the widthwise direction of the opening seal member  43  (the direction in which the two shorter sides of the joint portion  45  extend) can be increased. Thereby, the opening seal member  43  can be prevented from being fractured in the two shorter sides of the joint portion  45  by the shock or vibration during shipment. 
     Also, in this embodiment, as shown in FIGS. 14 and 15, an arc-like bent portion  45   b  is formed at each of two shorter sides of the rectangular joint portion  45 . With the bent portion  45   b,  even if, by the shock or vibration or the like during shipment, the powder pressure of the black toner acts on the film  43 A, each bent portion  45   b  of the two sides become liable to be inflated in the direction in which the powder pressure of the toner acts, and the amount of stretch in the widthwise direction of the opening seal member  43  (the direction in which the two shorter sides of the joint portion  45  extend) can be increased. Thereby, the opening seal member  43  can be prevented from being fractured in the two shorter sides of the joint portion  45  by the shock or vibration during shipment. 
     By adopting the construction as described above, a toner containing portion  21 BG of a large capacity capable of containing a great deal of black toner can be provided in the black developing unit  21 B. 
     While in the present embodiment, a bent portion  45   b  is formed at a location in each of the two shorter sides of the joint portion  45 , the bent portion  45   b  may be formed at a plurality of locations. 
     The aforedescribed joint structure between the film  43 A and tape  43 B of the opening seal member  43  can also be suitably applied to the yellow developing unit  20 Y, the magenta developing unit  20 M and the cyan developing unit  20 C. 
     Construction of a Toner Sealing Member (Developer Sealing Member) 
     The construction of a toner sealing member  40  as a developer sealing member according to the present invention will hereinafter be described. 
     As shown in FIGS. 19A and 19B, the toner sealing member  40  is divided into a first layer  40 A as a surface layer and a second layer  40 C as an inner layer. The first layer  40 A is fiber having a low coefficient of friction and wear resistance, and should desirably be a synthetic fiber, such as fluorine resin fiber, polyester, acryl or nylon, a chemical fiber such as rayon, or a mixture of these. 
     Generally, it is desirable to use fluorine resin fiber, and use can be made, for example, of polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FPT), tetrafluoroethylene-parfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene copolymer (ETFE) or the like. 
     In the present embodiment, fiber having PTFE mixed therewith and made into felt is used as the first layer  40 A. As shown in FIG. 20, the felt has its fiber projected from the felt surface to a height of 0.5 to 5 mm by the use of a fork needle  41 , and is formed with loop-like projections  40 AC. 
     Next, the raising holding process is carried out, and by the use of roll press RP or the like, the loop-like projections  40 AC is laid in a predetermined direction, i.e., the same direction as the axial direction of the developing roller  21 BS to thereby make the thickness of the texture uniform. Further, the direction in which the projections  40 AC of the developer sealing member  40  is laid is toward the inside of the developing roller  21 BS. 
     Then, the first layer  40 A and the polyurethane foam (e.g. Poron produced by INOAC Inc.) of the second layer  40 C, which is a cushion material, are joined together by a both-surface tape  40 B having no base material (e.g., No. 5619 produced by Nitto Electric Industrial Co., Ltd., F-69PC produced by Sumitomo 3M Ltd. or the like). 
     Further, the same both-surface tape  40 D having no base material as the aforedescribed both faces (both-surface) tape  40 B is adhered to the outer side of the second layer  40 C (the side opposite to the first layer  40 A). 
     The toner sealing member  40  is fixed to the developing portion frame  21 BL on the outer side of the lower opening portion  21 BA of the toner containing portion  21 BG in a state bent along the circumferential surface (outer peripheral surface) of the lengthwise end portion of the developing roller  21 BS by the both-surface tape  40 D. The black toner is supplied from the opening portion  21 BA to the developing roller  21 BS, and the projections  40 AC of the belt surface of the first layer  40 A is in close contact with a portion of the circumferential surface (outer peripheral surface) of the developing roller  21 BS (a portion of the outside of the area to which the black toner is applied (the outside of the black toner bearing area)). 
     The toner sealing member  40  fixed to the developing portion frame  21 BL as described above is such that the loop-like projections  40 AC of the felt surface of the first layer  40 A catches the black toner on the outer peripheral surface of the developing roller  21 BS and prevents the outflow of the black toner to the outside. 
     Also, the direction in which the loop-like raising  40 AC of the first layer  40 A is laid down is toward the lengthwise center of the developing roller  21 BS. Therefore, the resistance in the outflow direction of the black toner can be increased and thus, the outflow of the black toner can be better prevented. 
     Also, the both-surface tape  40 B having no base material is used for the joining of the first layer  40 A and the second layer  40 C and therefore, when the toner sealing member  40  is bent along the circumferential surface of the developing roller  21 BS and fixed to the developing portion frame  21 BL, the felt surface of the first layer  40 A can be prevented from being wrinkled. 
     Also, the both-surface tape  40 D having no base material is adhesively secured to the outer side of the second layer  40 C, whereby the toner sealing member  40  can be bent so as to be along the circumferential surface of the developing roller  21 BS and accurately fixed to the developing portion frame  21 BL. 
     While in the present embodiment, the toner sealing members  40  are disposed on the lengthwisely opposite end portions of the developing roller  21 BS of the black developing unit  21 B, of course they may be disposed on the lengthwisely opposite end portions of each of the developing rollers  20 YS,  20 MS and  20 CS of the yellow developing unit  20 Y, the magenta developing unit  20 M and the cyan developing unit  20 C, respectively, or on the lengthwisely opposite end portions of the image bearing body  15  as a process cartridge. By the toner sealing members  40  of the construction as previously described being thus disposed on the lengthwisely opposite end portions of each of the developing rollers  20 YS,  20 MS and  20 CS or the image bearing body  15 , an effect similar to the effect obtained by the aforedescribed toner sealing members  40  can be obtained. 
     Construction of the Shutter 
     Now, on the black developing device  21 B, as previously described, the shutter  21 BO for protecting the developing roller  21 BS is held so as to be rotatively movable (see FIGS. 2,  5  and  26 ). As shown in FIG. 26, a shutter opening-closing member  21 BP is rotatably mounted on a holder  21 BY disposed on the rear side of the black developing device  21 B, and is biased in one direction by a spring (not shown). 
     Also, a shutter shaft  21 BQ is disposed astride a holder  21 BX disposed on the front side of the black developing device  21 B, and is rotatably supported by a mounting member, not shown, provided on the same axis as the axis of the developing roller  21 BS. 
     When in this state, a rotational moment is given to the other end portion (arm end)  21 BP 1  of the shutter opening-closing member  21 BP in a direction perpendicular to the bus line of the image bearing body  15 , the shutter opening-closing member  21 BP is rotated and the shutter  21 BO is smoothly rotatively moved. 
     In order to realize the rotation of the shutter opening-closing member  21 BP, in the present embodiment, an opening-closing guide member  51  is disposed in a pivotally movable guide portion  50  provided in the main body  100  of the printer (see FIG.  2 ). The opening-closing guide member  51  is fixed to the pivotally movable guide portion  50  and is a wall surface formed by a gentle slope. 
     When the user inserts the developing unit  21 B into the pivotally movable guide portion  50  to some extent, the arm end  21 BP 1  of the shutter opening-closing member  21 BP bears against the opening-closing guide member  51 . When the insertion of the black developing unit  21 B is further continued, the arm end  21 BP 1  of the shutter opening-closing member  21 BP moves along the gentle slope formed on the opening-closing guide member  51 . 
     The shutter  21 BO as the protective member in the present embodiment is formed of permanent charging preventing resin, of which the surface resistivity is 10 5  to 10 13  Ω/sq. By the shutter  21 BO being formed of permanent charging preventing resin, dust, nap, etc. can be prevented from electrostatically adhering to the shutter  21 BO. 
     As hydrophilic polymers used in permanent charging preventing resin, there are, for example, polyethylene glycol methacrylate copolymer, poly(ethyleneoxide/proyleneoxide) copolymer, polyamide of polyethylene glycol series, polyester amide of polyethylene glycol series, poly(epichlorohydrin/ethyleneoxide) copolymer, etc. 
     Other Embodiments 
     In the aforedescribed embodiment, a color toner image forming apparatus has been exemplified as the electrophotographic image forming apparatus, whereas the present invention need not be restricted thereto, but a similar construction can also be adopted in an electrophotograhic image forming apparatus such as a monochromatic electrophotographic image forming apparatus, an electrophotographic copying apparatus, an electrophotographic facsimile apparatus or an electrophotographic word processor. 
     Also, the electrophotographic photosensitive body is not restricted to the photosensitive drum (image bearing body), but for example, the following are included. First, a photoconductive body may be used as the photosensitive body, and for example, amorphous silicon, amorphous selenium, zinc oxide, titanium oxide and organic photoconductive material (OPC) may be included as the photoconductive body. Also, as a shape carrying the photosensitive body thereon, use may be made, for example, of a drum-like shape or a belt-like shape, and for example, in a drum type photosensitive body, a photoconductive material is deposited by evaporation or applied onto a cylinder of an aluminum alloy or the like. 
     Also, as the developing method, it is possible to use one of several developing methods, such as the conventional two-component magnetic brush developing method, the cascade developing method, the touchdown developing method and the cloud developing method. 
     Also, while in the aforedescribed embodiment, the so-called contact charging method has been used as the construction of the charging means, it is a matter of course that as other construction, use may be made of a construction in which a metallic shield of aluminum or the like is provided around a heretofore used tungsten wire, and positive or negative ions created by applying a high voltage to the tungsten wire are moved to the surface of a photosensitive drum, and the surface of this drum is uniformly charged. 
     As the charging means, use may be made of a blade (charging blade), a pad type one, a block type one, a rod type one, a wire type one or the like, besides the aforedescribed roller type one. 
     Also, as the method of removing any toner residual on the photosensitive drum, a blade, a fur brush, a magnetic brush or the like may be used to construct cleaning means. 
     Also, the drum unit as the aforedescribed process cartridge is provided, for example, with an electrophotographic photosensitive body and at least one process means acting on this electrophotographic photosensitive body. Accordingly, as the modes of the process cartridge, there are, besides the aforedescribed embodiment, for example, one detachably attachable to the main body of the image forming apparatus, one comprising an electrophotographic photosensitive body and cleaning means integrally made into a cartridge so as to be detachably attachable to the main body of the image forming apparatus, and further, such cartridge also provided with a developing apparatus.