Patent Publication Number: US-6671473-B2

Title: Developing apparatus provided with seal functions on both sides of developing roller

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a developing apparatus to be mounted in an image forming apparatus, which uses a recording technique such as an electrophotographic process, an electrostatic recording process or the like, like a copying machine, a printer and the like. In particular, the present invention relates to a developing apparatus suitable for being mounted in a process cartridge capable of being detachably attachable to an image forming apparatus. 
     2. Related Art 
     An image forming apparatus using an electrophotography requires maintenance, such as the exchange of its photosensitive body drum, the replenishment or the exchange of its developer, the adjustment, the cleaning or the exchange of its other parts (its charger, its cleaner container, or the like), when the image forming apparatus has been used for a long time. It is practically difficult for a person other than a serviceperson having an expert knowledge to do such maintenance work. 
     Accordingly, an image forming apparatus employing an electrophotographic image forming process has employed a process cartridge system in which an electrophotographic photosensitive body and process means working on the electrophotographic photosensitive body are integrally formed to be a cartridge and the cartridge is made to be detachably attachable to the main body of the image forming apparatus. Because the process cartridge system enables a user to perform the maintenance of the apparatus by himself or herself without relying on a serviceperson, the process cartridge system has been able to improve the operability of the image forming apparatus remarkably. Consequently, the process cartridge system is widely used in the image forming apparatus. 
     Thereby, when the maintenance of an aforesaid process device becomes necessary, a user himself or herself can simply maintain or exchange a process cartridge, and consequently, it has become able to obtain a high grade image quality cheaply and easily. 
     Developing means (or a developing apparatus) built in such a process cartridge is provided with seal members for preventing the outflow of toner to an area other than the developing area at both end portions of a developer bearing body such as a rotating developing roller mounted in the developing apparatus. An elastic body made of a felt, a expanded rubber or the like is widely used as a conventional seal member preventing the outflow of toner. 
     A developing roller is provided with a magnet roller therein, and is rotatably supported by a developing container with sleeve bearings. Consequently, toner fed from the developing container attaches to the surface of the developing roller by a magnetic force of the magnet roller. After the thickness of the attached toner layer has been regulated by a developing blade, the toner attaches to a latent image on a photosensitive drum at a position opposed to the latent image on the photosensitive drum as the developing roller rotates. Consequently, the latent image is developed. 
     The developing apparatus is further provided with elastic seal members attached at both end portions of the developing roller at the outsides of the developing area in the lengthwise direction thereof and at the inner part on the side opposite to the opening side of the developing roller attached to a developing frame body of the developing apparatus. The elastic seal member is pressed to the outer peripheral surface of the developing roller for preventing the outflow of toner. 
     As for the aforesaid contact type seal members, because the elastic seals are pressed to the half of the outer peripheral surface of the developing roller, the conventional developing apparatus has the problem such that the load of the developing roller, which rotates at the time of a developing operation, is large, and the problem such that the elastic seal members deteriorate owing to the contact with the developing roller to make the sealing performance of the elastic seal members worse. Moreover, toner sometimes enters into the gaps between the developing roller and the elastic seal members, although the amount of the so entering toner is small. The invasion of the toner sometimes causes an increase of torque or an increase of fluctuations of torque to produce the unevenness of the rotations of the developing roller. And then, a bad influence is sometimes exerted upon image formation. 
     Accordingly, for solving those problems, a noncontact type seal member has been proposed. In the noncontact type seal member, seal members made of a magnetic body (hereinafter referred to as “magnetic seals”) are disposed at both end portions of the developing roller with predetermined spaces between them for preventing the outflow of toner. 
     The magnetic seal is made of a magnet. The magnetic seals are attached to both end portions of the developing roller in the state of being wound around the end portions for being disposed with a predetermined gap (about 0.1 mm to 0.7 mm) to the outer peripheral surface of the developing roller. The magnetic seals are attached to the developing container in the wound state along with the developing roller. The surfaces of the magnetic seals opposed to the developing roller are magnetized. Magnetic brushes formed by chained toner formed along each line of magnetic force fill up the gaps between the outer peripheral surface of the developing roller and the surfaces of the magnetic seals to prevent the outflow of toner from the developing area. 
     Moreover, because it is needed to locate the magnetic seals highly precisely to the developing roller, various locating methods have conventionally been devised. 
     Incidentally, in both cases of the use of the aforesaid contact type seal member and the use of the noncontact type seal member, high accuracy of the attachment of them to the main body of the developing apparatus is required for securing their seal performances. 
     SUMMARY OF THE INVENTION 
     The present invention was made in consideration of the aforesaid problems, and an object of the invention is to provide a developing apparatus in which toner does not easily leak out. 
     Another object of the invention is to provide a developing apparatus in which seal members for preventing the leakage of the toner from the end portions of the developing roller can be attached with high accuracy. 
     A further object of the invention is to provide a developing member to which seal members for preventing the leakage of toner from the end portions of its developing roller can be attached simply and accurately. 
     A still further object of the invention is to provide a developing apparatus in which the positional accuracy of seal members to its developing roller is high. 
     A still further object of the invention is to provide a developing apparatus including a rotatable developer bearing member, a bearing member for holding the developer bearing member rotatably, and a seal member for preventing the leakage of a developer from an end portion of the developer bearing member in the lengthwise direction thereof into the lengthwise direction, wherein the seal member is located by the bearing member. 
     The still further object of the invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of the principal section of a process cartridge according to an embodiment of the present invention; 
     FIG. 2 is a schematic diagram of the principal section of the apparatus main body according to the embodiment of the invention; 
     FIG. 3 is a side elevation showing the process cartridge of the embodiment of the invention seen from a side face thereof; 
     FIG. 4 is a side elevation showing the process cartridge of the embodiment of the invention seen from another side face thereof; 
     FIG. 5 is a perspective view of the process cartridge in the embodiment of the invention; 
     FIG. 6 is another perspective view of the process cartridge in the embodiment of the invention; 
     FIG. 7 is a disassembled perspective view of a process cartridge frame body in the embodiment of the invention; 
     FIG. 8 is a front view of a developing apparatus; 
     FIG. 9 is a sectional view of the developing apparatus taken along IX—IX line in FIG. 8; 
     FIG. 10 is a sectional view of the developing apparatus taken along X—X line in FIG. 9; 
     FIG. 11 is a sectional view of the developing apparatus taken along XI—XI line in FIG. 8; 
     FIG. 12 is a perspective view showing a state of each part of the developing apparatus before they are assembled; 
     FIG. 13 is a perspective view of a simplex magnetic seal; 
     FIG. 14 is a perspective view showing only a developing bearing frame body and a developing frame body before they are assembled; 
     FIG. 15 is a perspective view of another embodiment of the developing bearing frame body; 
     FIG. 16 is a perspective view showing only a developing roller and a magnetic seal; and 
     FIG. 17A is a sectional view of the developing roller and the magnetic seal taken along an XVII—XVII line in FIG. 16, and FIG. 17B is a macrograph of the part of  17 B in FIG.  17 A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 to FIG. 17B are referenced while an preferred embodiment of the present invention is described. 
     Description of Process Cartridge and Apparatus Main Body 
     FIG. 1 is a diagram of the principal section of a process cartridge according to the present invention, and FIG. 2 is a diagram of the principal section of an image forming apparatus according to the invention. The process cartridge is equipped with an image bearing body and process means working on the image bearing body. The process means includes, for example, charging means for charging the surface of the image bearing body, a developing apparatus for forming a toner image on the image bearing body, and cleaning means for removing the toner remaining on the surface of the image bearing body. 
     The process cartridge  15  of the present embodiment disposes, as shown in FIG. 1, a charging roller  12  being the charging means; a developing roller  18 , a developing blade  26  and a toner containing frame body  16  for containing toner as the developing means; and a cleaning blade  14  as the cleaning means around the electrophotographic photosensitive body drum (hereinafter referred to as a “photosensitive body drum”)  11  being the image bearing body. Each component is integrally covered by a housing to be the process cartridge  15 . The process cartridge  15  is configured to be detachably attachable to an image forming apparatus main body C. 
     FIG. 2 shows the image forming apparatus in the state capable of forming an image after the process cartridge  15  has been mounted in the apparatus main body C. The process cartridge  15  can be detached from the apparatus main body C in conformity with the following procedures. That is: at first, a hoist arm  2  capable of supporting the left side end portion of the process cartridge  15  is raised with a not shown handle to swing the process cartridge  15  on a guide rail  24  of the apparatus main body C around a fulcrum foot  5  of the process cartridge  15 ; a guide portion  15   a  of the process cartridge  15  is thereby made to accord with a guide rail  24  of the apparatus main body C; and then the process cartridge  15  is pulled out toward the front side of FIG. 1 by a user, being gripped by the user&#39;s hand on a handle  25  (see FIG.  3 ). 
     The attachment of the process cartridge  15  to the apparatus main body C is performed in conformity with the reverse procedures of the procedures at the detachment thereof described above. 
     The process cartridge  15  is used for image formation in the state of being mounted in the apparatus main body C shown in FIG.  2 . The image formation is performed in conformity with the following procedures. That is, at first, a sheet S as a recording medium is conveyed from sheet cassettes  6  mounted at the lower part of the apparatus with conveying rollers  7 , and an exposing apparatus  8  selectively exposes the photosensitive body drum  11 , which has uniformly been charged by the charging roller  12 , to light synchronously with the sheet conveyance for forming a latent image. After that, toner contained in the toner containing frame body  16  is carried toward the developing roller  18 , and a thin toner layer is borne on the surface of the developing roller  18  with the developing blade  26 . And then, a developing bias is applied to the developing roller  18  to feed toner on the surface of the photosensitive body drum  11  according to the latent image. The toner image on the photosensitive body drum  11  is then transferred to the conveyed sheet S by the application of a bias voltage to a transferring roller  9 . The sheet S is conveyed to a fixing apparatus  10 , and the toner image transferred on the sheet S is fixed by the fixing apparatus  10 . Then, the sheet S is delivered to a discharging portion  3  at the upper part of the apparatus by discharging rollers  1 . 
     Frame Body Configuration of Process Cartridge 
     FIG.  1  and FIGS. 3 to  7  are referred while the configuration of the process cartridge  15  is described. FIG. 7 is a perspective view showing the frame configuration of the process cartridge  15  before it is assembled. The process cartridge  15  is chiefly composed of three frame bodies: a cleaning frame body  13  in which the photosensitive body drum  11 , the charging roller  12  and the cleaning blade  14  are integrally incorporated; a developing frame body  17  in which the developing roller  18  and the developing blade  26  (not shown in FIG.  7 . See FIG. 1) are integrally supported; and the toner containing frame body  16  containing toner T therein. Moreover, side covers  19  and  20  for supporting the three frame bodies  13 ,  17  and  16  integrally fix them on both the side faces of them to constitute the process cartridge  15 . 
     The cleaning frame body  13  fixes the cleaning blade  14  with machine screws or the like thereto, and supports the charging roller  12  rotatably at the core metal portions on both end portions of the charging roller  12  with bearing members (not shown) being put between the cleaning frame body  13  and the charging roller  12 . Moreover, the cleaning frame body  13  rotatably supports the photosensitive body drum  11  at flange portions  11   a  and  11   b  on both end portions of the photosensitive body drum  11  with bearing members  22  and  23  being put between the cleaning frame body  13  and the photosensitive body drum  11 . Incidentally, as shown in FIG.  4  and FIG. 5, the flange portion  11   a  supports the so-called triangle coupling  11   c  to engage with a driving coupling of the apparatus main body C at an end portion of the flange portion  11   a , and the flange portion  11   a  is driven from a driving apparatus in the apparatus main body C through the triangle coupling  11   c  to drive the photosensitive body drum  11 . The toner containing frame body  16  contains toner T in its inside together with toner carrying members  27 . 
     The developing roller  18  including a magnet roller  18   a , the developing blade  26  and a magnetic seal (not shown in FIG. 7) are disposed in the developing frame body  17 . One side end of the magnet roller  18   a  is supported by a projecting portion  17   e  being a developing roller bearing of the developing frame body  17  and the other side end thereof is supported by the developing frame body  17 , and the magnet roller  18   a  keeps a gap with the developing roller  18 . The developing roller  18  is configured to perform the electric power supply thereto through an electric contact point disposed in the inside of the developing roller  18 . Moreover, an anti-climbing roller (not shown) for keeping the interval from the photosensitive body drum  11  constant is provided on the developing roller  18 . 
     The developing frame body  17  is supported by the cleaning frame body  13  swingably around a suspension hole  17   d  formed on one side face side of the developing roller  18  such that the center of the developing roller  18  goes toward the center of the photosensitive body drum  11 . 
     Moreover, the process cartridge  15  is configured to pressurize the projecting portion  17   e , which is fixed on a central axis line of the developing roller  18  in the lengthwise direction thereof on the other side face side of the developing frame body  17 , toward the center of the photosensitive body drum  11 . The projecting portion  17   e  is configured to be inserted into a groove  19   e  (an elongated hole in the shape of a straight line substantially parallel in the center direction of the photosensitive body drum  11  in the present embodiment) formed on the side cover  19  in the state movable to the center direction of the photosensitive body drum  11 . Moreover, an elastic member (not shown) is disposed in the inside of the groove  19   e  such that the elastic body pressurizes the projecting portion  17   e  to bias the developing roller  18  along the photosensitive body drum  11 . 
     On the other hand, the groove  19   e  also has the role of a locating hole for regulating the moving direction of the developing roller  18 . 
     When a driving force works on the process cartridge  15 , high gears (not shown), which are respectively provided on the photosensitive body drum  11  and the developing roller  18 , and mesh with each other, are designed to receive a force respectively in the direction of interlocking with each other around the suspension hole  17   d  lest the forces should work in the direction to separate the photosensitive body drum  11  and the developing roller  18  from each other. Moreover, the elastic member provided in the groove  19   e  also pressurizes the developing roller  18  toward the photosensitive body drum  11  at all times. 
     The side cover  19  on one side has a size covering a principal section of the process cartridge  15 . The side cover  19  is disposed on one end of the process cartridge  15  in the lengthwise direction. The side cover  19  integrally supports the cleaning frame body  13  and the toner containing frame body  16  by fixing them thereto respectively. A hole portion  19   a  in the side cover  19  is located on the same axis as that of the center of the photosensitive body drum  11 . At this time, if the location of the side cover  19  is performed by the use of the bearing member  22 , the location can be determined highly precisely. Moreover, a locating portion  19   b  formed at a position distant from the photosensitive body drum  11  as far as possible locates the position of side cover  19  in the rotational direction thereof together with a locating portion  13   b  formed on a side face of the cleaning frame body  13 , and the side cover  19  and the cleaning frame body  13  are fixed to each other with several machine screws. Furthermore, the toner containing frame body  16  forms locating portions  16   a  and  16   b  on its one end face. The toner containing frame body  16  is located to the side cover  19  by means of the locating portions  16   a  and  16   b  and locating portions  19   c  and  19   d  disposed on the side cover  19 . The toner containing frame body  16  is fixed to the side cover  19  with several machine screws. The side cover  20  on the other side is similarly configured. 
     Moreover, the bearing member  22  also has the role of a locating member of the process cartridge  15  to the apparatus main body C. Opening portions  16   c  and  17   a  are respectively formed in the toner containing frame bode  16  and the developing frame body  17  for the supply of toner from the toner containing frame body  16  to the developing roller  18 . The opening portions  17   a  and  16   c  in the developing frame body  17  and the toner containing frame body  16  are connected through a seal member  21 . Moreover, the toner containing frame body  16  is located by the side covers  19  and  20 , the developing frame body  17  is located by the cleaning frame body  13 . There is consequently the possibility that distortion is produced in either of the developing frame body  17  and the toner containing frame body  16  owing to dimension errors between them. Accordingly, the seal member  21  is made from a flexible material. In such a configuration, if toner increases in the process cartridge  15 , the load owing to the increased toner is imposed on the side covers  19  and  20 , and no loads are imposed on the developing roller  18 . Consequently, no surplus loads are imposed on the photosensitive body drum  11 , and stable images can be obtained. Moreover, because the three frame bodies  13 ,  17  and  16  are connected to the side covers  19  and  20  on their side faces, the locations of the respective frame bodies  13 ,  17  and  16  can be determined by means of only the side covers  19  and  20 . Consequently, the frame bodies  13 ,  17  and  16  can precisely be connected to each other. 
     Description of Developing Apparatus 
     Next, the developing apparatus is described more minutely. FIG. 8 is a plan view of the developing apparatus seen from the direction orthogonal to the lengthwise direction of the developing roller  18 . FIG. 9 is a sectional view of the developing apparatus taken along IX—IX line in FIG.  8 . FIG. 10 is a sectional view of the developing apparatus taken along X—X line in FIG.  9 . FIG. 11 is a sectional view of the developing apparatus taken along XI—XI line in FIG.  8 . FIG. 12 is a perspective view showing a state of each part of the developing apparatus before they are assembled. FIG. 13 is a perspective view of a simplex magnetic seal. FIG. 14 is a perspective view showing only a developing bearing frame body and the developing frame body  17  before they are assembled. FIG. 15 is a perspective view of another embodiment of the developing bearing frame body. FIG. 16 is a perspective view showing only a developing roller and a magnetic seal. FIG. 17A is a sectional view of the developing roller and the magnetic seal taken along XVII—XVII line in FIG. 16, and FIG. 17B is a macrograph of the part of  17 B in FIG.  17 A. 
     As described above, the developing roller  18  and the developing blade  26  are incorporated into the developing frame body  17  as the components related to image formation. 
     As shown in FIG. 12, the developing blade  26  is composed of a sheet metal  26   a  having the thickness of about 1 mm to 2 mm and a polyurethane rubber  26   b  fixed on the sheet metal  26   a  by hot melt adhering or with a pressure sensitive adhesive double coated tape or the like. By the contact of the polyurethane rubber  26   b  with a generating line of the developing roller  18 , the quantity of the toner on the peripheral surface of the developing roller  18  is regulated. Incidentally, a silicon rubber may be employed as the developing blade  26 . Female screws  17   g  are provided on anti-climbing planes  17   f  formed in the developing frame body  17  as blade fitting portions, and dowels (not shown) for location are formed at positions near to the centers of the anti-climbing planes  17   f  a little. Accordingly, fitting holes  26   d  formed in the sheet metal  26   a  are fitted to the dowels (not shown) each other. After that, machine screws  57  are screwed into the female screws  17   g  through tapped holes  26   c  to fix the sheet metal  26   a  to the anti-climbing planes  17   f . Thus, the position of the leading edge of the polyurethane rubber  26   b  is determined, and then the touching pressure of the polyurethane rubber  26   b  to the developing roller  18  is determined. Consequently, the distance from the leading edge of the polyurethane rubber  26   b  to the touching position is determined, and the development condition is determined. Moreover, one end of the sheet metal  26   a  of the developing blade  26  is bent by the angle of about 90 degrees to form a bent portion  26   e  for the heightening of the rigidity of the sheet metal  26   a  in order that the polyurethane rubber  26   b  is touched to the developing roller  18  uniformly in the lengthwise direction of the developing roller  18 . 
     Incidentally, an elastic seal member  51 , which is made from a moltopren (trade name) or the like and is formed in a shape of substantially a letter U, is stuck to the developing frame body  17  along its elastic seal seat surface  17   h  (see FIG. 12) at the upper part of the opening portion  17   a  in the lengthwise direction and its seat surfaces  17   j  in the widthwise direction for the prevention of the leakage of toner to the outside. A first straight line portion  51   c  of the elastic seal member  51  is stuck to the seat surface  17   h  of the developing frame body  17 , and second straight line portions  51   a  of the seal member  51  are stuck to the seat surfaces  17   j . The elastic seal member  51  is put between the developing frame body  17  and the developing blade  26  to be pinched out by them, and thereby the leakage of toner is prevented. Lug portions  51   b  are formed on the elastic seal member  51  at both end portions thereof to project from the end portions in the lengthwise direction of the seal member  51  by several millimeters. The lug portions  51   b  perform the role of locating the magnetic seal  50 , which will be described later. 
     Moreover, as shown in FIG.  9  and FIG. 12, the magnetic seals  50  are attached to grooves  17   k  formed on the surfaces adjoining (at the insides of arc surfaces  17   l  in the lengthwise direction of the developing roller  18 ) to the arc surfaces  17   l  and flat surfaces continuing upward from the arc surfaces  17   l  along the peripheral direction of the developing roller  18  at both end portions of the opening portion  17   a  in the lengthwise direction of the developing roller  18 . The magnetic seals  50  will be described later in detail. 
     Furthermore, a thin film elastic seal member (not shown), which abuts on a generating line of the developing roller  18 , is stuck to a seat surface  17   m   1  in the upper part of a lower jaw portion  17   m  of the developing frame body  17 . 
     The developing roller  18  is a cylindrical member made of a metal material of aluminum, stainless steel or the like. The outer diameter of the cylindrical shape of the developing roller  18  is about 16 mm to 20 mm, and the thickness of the cylindrical shape is about 0.5 mm to 1 mm. A surface treatment such as carbon coating, abrasive blasting or the like is performed to the surface of the developing roller  18  for the heightening of the electrification characteristic of developer. Only the carbon coating is performed in the present embodiment. 
     Sleeve flanges (only one end portion of them is shown in FIG. 12)  18   s , which are stepped cylindrical members made of a metal material of aluminum, stainless steel or the like, are force-fitted into both end portions of the developing roller  18 . Each of the sleeve flanges  18   s  is coaxial with the developing roller  18 , and is composed of a first cylindrical portion  18   b  and a second cylindrical portion  18   c , the outer diameters of which are smaller in the stated order. The first cylindrical portion  18   b  is provided with a spacer roller  53  being a ring-shaped distance regulating member for regulating the opposed distance between the developing roller  18  and the photosensitive body drum  11 . The spacer roller  53  is made from an insulating material, such as polycetal or the like. A developing bearing frame body  55  (its especially enlarged perspective view seen from the reverse side is shown in FIG. 14) for supporting the developing roller  18  rotatably and locating it to the developing frame body  17  is disposed around the second cylindrical portion  18   c . Moreover, two flat surfaces  18   d  are formed at the tip portion of the second cylindrical portion  18   c , and a developing roller gear  54  made from a synthetic resin is fitted to the cylindrical portion  18   c  having the flat surfaces  18   d . The developing roller gear  54  is driven by a helical drum gear (not shown) provided at an edge portion of the photosensitive body drum  11  to rotate the developing roller  18 . The helical teeth of the drum gear are twisted such that the thrust thereof in the axial direction thereof works in the lengthwise direction of the developing roller  18 . Moreover, a magnet roller (designated by a reference numeral  18   a  in FIG. 17A) for making toner adhere to the peripheral surface of the developing roller  18  is built in the developing roller  18 . Because the sleeve flange on the other end portion of the developing roller  18  has a similar configuration, the descriptions thereof is omitted here. The developing bearing frame body  55  is made from a resin material producing a good slidable property, and is shaped to be a flat plate having a thickness of about 2 mm to 5 mm. At approximately the center of the flat plate portion, a cylindrical bearing portion  55   a  is formed. The inner diameter of the bearing portion  55   a  is 8 mm to 15 mm. The bearing portion  55   a  fits to the second cylindrical portion  18   c  of the sleeve flange  18   s , and thereby the developing roller  18  slides therein while rotating. Moreover, a dowel  55   c  including a first step portion  55   d , and a second step portion  55   e  at its end portion, both being for locating the developing bearing frame body  55  against the developing frame body  17 , is formed on the surface  55   g  of the flat plate portion of the developing bearing frame body  55  in substantially parallel with the bearing portion  55   a . The dowel  55   c  performs the role of locating the developing bearing frame body  55  against the developing frame body  17 . The first step portion  55   d  and the second step portion  55   e , both being coaxial with the dowel  55   c  at the end portion of the dowel  55   c  are used for the location of the magnetic seal  50 , which will be described later. Moreover, on the same surface  55   g , tapped holes  55   b  for the fixation of the developing bearing frame body  55  to the developing frame body  17  with machine screws  56  or the like, and a dowel  55   f  for the location of the developing bearing frame body  55  to the developing frame body  17  are formed. The dowel  55   c  of the developing bearing frame body  55  is fitted into a location hole  17   c  (shown in FIG. 14) formed in the developing frame body  17 , and the dowel  55   f  is fitted into a fitting elongated hole  17   o  formed in e developing frame body  17 , and further the surface  55   g  of the developing bearing frame body  55  is touched to a surface  17   p  of the developing frame body  17 . Then, the machine screws  56  are screwed into female screws  17   q  and  17   r  formed on the developing frame body  17  through the two tapped holes  55   b , and the developing bearing frame body  55  is fixed to the developing frame body  17 . Thereby, the positions of the developing blade  26  and the developing roller  18 , both being fixed to the developing frame body  17 , are surely determined, and stable images can be outputted. 
     Because the developing roller  18  slides in the bearing portion  55   a  of the developing bearing frame body  55  mentioned above, the material of the developing bearing frame body  55  is preferably a comparatively high priced material having a good sliding property (for example, a bearing material based on poly phenylene sulfide (PPS) or polyamide (PA)). Accordingly, as shown in FIG. 15, if only a bearing portion is separated from a housing  100  as a bearing bushing  101 , the quantity of the expensive material to be used is not needed so much, and the housing  100  can be made from a comparatively cheap material such as high-impact polystyrene (HIPS). 
     Magnetic Seal 
     The magnetic seal  50  (shown in an especially enlarged figure in FIG. 13) is an injection-molded article having a width of 3 mm to 4 mm. A magnet  50   a  being a component of the magnetic seal  50  includes Nd—Fe—B magnetic power with a nylon binder. A magnetic plate  50   b  being another component of the magnetic seal  50  is made from iron and has a thickness of 1 mm to 1.5 mm. The magnet  50   a  and the magnetic plate  50   b  are molded by the insert molding such that the magnetic plate  50   b  is embedded in the magnet  50   a  except for the remaining inner periphery and the outside side face of the magnet  50 . However, the joining by an adhesive, the joining by a pressure sensitive adhesive double coated tape, or the attraction joining only by a magnetic force can similarly bring about the advantages that will be described later. Moreover, the gap between the developing roller  18  and the magnetic seal  50  is 0.1 mm to 0.7 mm, and the magnetic flux density on the surface of the developing roller  18  owing to the magnetic force of the magnetic seal  50  in this case is about 1,000 Gs to 2,000 Gs. Then, as shown in FIG.  16 , in the state such that two magnetic seals  50  are fixed to the developing frame body  17 , the magnets  50   a  of the two magnetic seals  50  are located to be opposed to each other. 
     By the disposition of the two magnetic seals  50  in the way described above, the lines of magnetic forces  75  of each of the magnetic seals  50  are formed between the magnet  50   a  and the magnetic plate  50   b  to enter into the magnetic plate  50   b  having a higher permeability as shown in FIG. 17B, which is a macrograph of the part of  17 B in FIG.  17 A. Consequently, no lines of magnetic forces expand to the outside of the width of the magnetic seal  50 . 
     Consequently, toner diffusing along the lines of magnetic forces  75  on the surface of the magnetic seal  50  does not exist on the outside of the magnetic plate  50   b  on the side of the magnetic plate  50   b  (or the outside of the opening portion  17   a ). The phenomenon such that toner is touched to the spacer roller  53  being a distance regulating member owing to the rotations of the developing roller  18  does not happen. Consequently, the spacer roller  53  can be approached to the side face of the magnetic seal  50 , and thereby naturally the process cartridge  15  can be miniaturized, and the apparatus main body C can also be miniaturized. 
     Moreover, because the toner on the magnetic seal  50  does not diffuse to the outside of the opening portion  17   a  of the developing frame body  17  from the magnetic plate  50   b , the toner can securely be held within a range where the magnetic force on the surface of the magnetic seal  50  is strong. Consequently, a good seal property such that toner does not leak out even if impact or the like is imposed on the process cartridge  15  when a user attaches or detaches the process cartridge  15  to the apparatus main body C can be obtained. 
     Moreover, the fact that the lines of magnetic forces  75  enter into the magnetic plate  50   b  by the disposition of the magnetic plate  50   b  on the side face of the magnet  50   a  is to converge the lines of magnetic forces  75 , which has the tendency of divergence, into the magnetic plate  50   b . Consequently, the magnetic flux density on the surface of the magnet  50   a  becomes large, which makes the magnetic force of the magnet  50  large. Hence, it is achieved to improve the sealing property furthermore. In addition, because a cheap magnet, which has a small magnetic force, can be used if the sealing property is not needed so strictly, the cost of the process cartridge  15  can be decreased. 
     Location Configuration of Magnetic Seal 
     The magnetic seal  50  is located to the developing roller  18  by means of the developing frame body  17 , the elastic seal member  51  and the developing bearing frame body  55 , all being described above. That is, the magnetic seal  50  is located by a location hole  50   d  of the magnetic seal  50  shown in FIG.  9  and by the biasing of the magnetic seal  50  in the rotation direction around the location hole  50   d . The location is described on the basis of FIG. 8, FIG. 9, FIG. 10, FIG.  11  and FIG. 13 in detail. 
     As shown in FIG. 9, both the magnet  50   a  and the magnetic plate  50   b  have a half arc portion  50   e  (or the half arc portion of the magnetic seal  50 ), the inner periphery side of which forms a gap g 1  with the developing roller  18 , and an end face portion  50   c , which offsets to the side of he developing frame body  17  halfway on the half arc portion  50   e  to extend upward in a straight line from the upper part of he half arc portion  50   e . The cross section of the magnet  50   a  is nearly a square, and the cross section of the magnet  50   a  combined with the magnetic plate  50   b  is a square. An arc-shaped bending portion  50   h  projects towards the outside in the radial direction from the outer periphery  50   f  of the magnet  50   a , and the location hole  50   d  is exists at the center of the arc of the bending portion  50   h . As shown in FIG. 13, the upper end of the magnetic plate  50   b  is fitted into the end face portion  50   c , and the magnet  50   a  and the magnetic plate  50   b  form the same plane on the outside side face of the magnetic seal  50  in the lengthwise direction. 
     As shown in FIG.  9  and FIG. 12, a groove  17   k  ( 17   k   1 ,  17   k   2  and  17   k   3 ) for the attachment of the magnetic seal  50  is formed from the anti-climbing plane  17   f , to which the developing blade  26  is attached, to an adjoining position to the arc surface  17   l  along an end portion of the developing roller  18 . The groove  17   k  is composed of an arc groove  17   k   1  along the arc of the arc surface  17   l  (see FIG.  12 ), a straight line groove  17   k   2  along the anti-climbing plane  17   f  in a vertical direction, and a location groove  17   k   3 , in which the bending portion  50   h  (the inner periphery of which forms the location hole  50   d ) of the magnetic seal  50  is just fitted. These grooves  17   k   1 ,  17   k   2  and  17   k   3  are continuously formed. The location groove  17   k   3  is recessed from the base of the arc groove  17   k   1 . The width H (noted in FIG. 10) of the groove  17   k  and the width of the magnetic seal  50  are formed to be the same. And, the magnetic seal  50  is fitted into the groove  17   k . Thereby, the position of the magnetic seal  50  to the developing roller  18  in the lengthwise direction of the developing roller  18  is determined. Moreover, the depth of each portion of the groove  17   k  for the attachment of the magnetic seal  50  thereto is deeper than the thickness of each corresponding portion of the magnetic seal  50  by 0.1 mm to 0.7 mm when the magnetic seal  50  is fitted into a predetermined position (the fitting will be described later). That is, the surface of the outer periphery  50   f  of the magnetic seal  50  keeps a gap g 2  (see FIG. 9) from the groove  17   k  of the developing frame body  17 . For the prevention of the leakage of toner through the gap g 2 , a magnetic pole is disposed on the surface of the outer periphery  50   f  of the magnetic seal  50  as a magnetic pole is disposed on the surface opposed to the developing roller  18 , and the leakage of toner to the outside can be prevented by the magnetic force caused by the magnetic pole. Moreover, the magnetic seal  50  may be configured such that the magnetic plate  50   b  is extended to the surface of the outer periphery  50   f  to prevent the leakage of the magnetic force to the outside likewise on the developing roller  18  side for heightening the effect of the magnetic force. 
     Next, the location of the magnetic seal  50  is described in detail. As shown in FIG. 10, the first step portion  55   d  at the end of the dowel (or a shaft)  55   c  projecting from the developing bearing frame body  55  described above is fitted into the location hole  50   d  of the magnetic seal  50 , and thereby the magnetic seal  50  is rotatably supported around the first step portion  55   d . Moreover, the second step portion  55   e  at the end of the fist step portion  55   d  is fitted into a location hole  17   s , which is coaxial with the location hole  17   c  of he developing frame body  17  and is formed on the side opposed to the groove  17   k . Thereby, both the end faces of the magnetic seal  50  are supported. Because the magnetic seal  50  is supported at both the end faces, even if the shaft for location is slender in some degree, the magnetic seal  50  can be supported with a sufficient strength. Thereby, the space of the magnetic seal  50  can be reduced. Furthermore, although the dowel  55   c  being a location shaft easily falls in its formation process by molding, it is comparatively attained by molding to locate the center positions of the location holes  17   c  and  17   s  of the developing frame body  17  on the same axis precisely. Consequently, the location of the magnetic seal  50  can precisely be performed. 
     Next, the location of the magnetic seal  50  in its rotation direction is, as shown in FIG. 9, performed by the contact thereof to a lower end face  17   k   4  of the arc groove  17   k   1  of the developing frame body  17 , i.e. an end face  17   k   4  falling down from the seat surface  17   m   1  with an elastic seal (not shown) at the lower jaw portion  17   m  described above. Moreover, a biasing force F for contacting the magnetic seal  50  to the end face  17   k   4  surely is caused by a repulsive force generated by the compression of mainly the lug portion  51   b  (see FIG. 12) of the elastic seal member  51  lying between the portion of the end face  50   c  in a straight line at the upper part of the magnetic seal  50  and the sheet metal  26   a  of the developing blade  26 . Thus the biasing force F works on the magnetic seal  50  in the clockwise direction around the location hole  50   d , and thereby the magnetic seal  50  is surely located to the developing roller  18 . Moreover, only the developing bearing frame body  55  exists between the magnetic seal  50  and the developing roller  18 , and consequently the dispersion of the length of the gap g 1 , which generally becomes large by the accumulation of tolerances, is suppressed to be as small as possible. Consequently, the allowance for the leakage of toner can be improved. Moreover, although the gap g 1  has conventionally been measured during a manufacturing process, the examination of the gap g 1  becomes unnecessary because the accumulation of tolerances becomes small. Moreover, the biasing force F is produced by means of a part of the elastic seal member  51 , and thereby the location of the magnetic seal  50  can surely be performed at low cost without surplus parts. Furthermore, the elastic seal member  51  uses an insulating material, and thereby the elastic seal member  51  also performs the role of preventing leakage of a voltage when a high voltage is not desired to be applied to the sheet metal  26   a  of the developing blade  26 , for example. 
     Next, the assembly of the magnetic seals  50  until their positions are determined is described on the basis of FIG.  12 . 
     As shown in FIG. 12, the magnetic seals  50  are brought into the grooves  17   k  of the developing frame body  17  for the attachment of the magnetic seals  50  as indicated by an arrow D. Then, the half arc portions  50   e  of the magnetic seals  50  are fitted into the arc grooves  17   k   1 , and the end face portions  50   c  are fitted into the straight line grooves  17   k   2 . After that, the magnetic seals  50  are pushed into the arc grooves  17   k   1  and the straight line grooves  17   k   2  until the inner peripheral surfaces of the half arc portions  50   e  are at substantially the same heights as those of the arc surfaces  171 . Next, the first straight line portion  51   c  of the elastic seal member  51  is stuck to the elastic seat surface  17   h  being the end face of a rib of the developing frame body  17  in the lengthwise direction, and the second straight line portions  51   a  are stuck to the seat surfaces  17   j  of the developing frame body  17 . And further, the lug portions  51   b  are stuck to the end face portions  50   c  of the magnetic seal  50 . At this time, because the heights of the elastic seal seat surface  17   h  and the magnetic seal  50  are different from each other, the elastic seal member  51  is not easy for such to stick together (see FIG.  11 ). For making it easy to stick the elastic seal member  51 , a tapered plane  50   g  (shown in FIG. 13) is formed. Moreover, the lug portions  51   b  and the second straight line portions  51   a  may be formed to be separate bodies in view of material allotting. As for the incorporation of the developing blade  26 , as described above, the fitting holes  26   d  formed in the sheet metal  26   a  are fitted to each of their respective dowels (not shown). After that, the machine screws  57  are screwed into the female screws  17   g  through the tapped holes  26   c  formed in the sheet metal  26   a  to fix the sheet metal  26   a  to the anti-climbing planes  17   f . Next, the unit of the developing roller  18  is temporarily put in the developing frame body  17  to be coaxial with the half arc portions  50   e  of the magnetic seals  50 . At this time, the developing roller  18  does not directly contact with the magnetic seals  50  owing to the repulsive force of the polyurethane rubber  26   b  of the developing blade  26 , and consequently the surface of the developing roller  18  is not injured by the magnetic seals  50 . 
     Lastly, the developing bearing frame bodies  55  are assembled from both side face sides of the developing frame body  17  (though FIG. 12 shows one end side of the developing frame body  17 , the other end side thereof is in the same configuration). That is, as described above by reference to FIG. 14, the dowels  55   f  are fitted into the fitting elongated holes  17   o  (which are elongated in the up and down direction in parallel to the surface of the sheet of FIG.  10 ), and further the surfaces  55   g  of the developing bearing frame bodies  55  are touched to the surfaces  17   p  of the developing frame body  17 . Then, the machine screws  56  are screwed into the female screws  17   q  and  17   r  formed on the surfaces  17   p  through the tapped holes  55   b  formed in the developing bearing frame bodies  55 , and the developing bearing frame bodies  55  are fixed to the developing frame body  17 . Thereby, the magnetic seals  50  are located around the first step portions  55   d  in the states of being able to tilt. The magnetic seals  50  receive moments around the first step portions  55   d  by forces biased by the repulsive force of the elastic seal member  51  lying between the magnetic seals  50  and the developing blade  26 , and the lower end faces of the magnetic seals  50  are touched to the lower end faces  17   k   4  of the grooves  17   k  of the developing frame body  17 . 
     As described above, the positions of the magnetic seals  50  to the developing roller  18  are surely determined by a simple assembling method. 
     The present invention is not bounded to the aforesaid embodiments, and many modifications within the scope of the technical concepts of the present invention can be included therein.