Patent Publication Number: US-8983342-B2

Title: Developer storage container, image forming unit and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a developer storage container, an image forming unit and an image forming apparatus. 
     An image forming apparatus such as a printer, a copier, a facsimile machine and a multifunction peripheral includes an image forming unit. The image forming unit includes a main body (i.e., an image forming unit main body) and a toner cartridge (i.e., a developer storage container) detachably mounted to the image forming unit main body. 
     The toner cartridge includes a case storing a toner (i.e., a developer) therein. The case has an opening through which the toner is supplied to the image forming unit main body. A shutter is rotatably provided in the case so as to open and close the opening. The image forming unit main body has a receiving opening for receiving the toner supplied by the toner cartridge (see, for example, Japanese Laid-open Patent Publication No. 2006-243446). 
     In this regard, when the shutter is rotated to close the opening, the toner adhering to the receiving opening of the image forming unit main body may adhere to an outer surface of the shutter. Therefore, when the toner cartridge is detached from the main body, the toner adhering to the shutter may scatter outside. The scattered toner may contaminate surroundings, i.e., a case of the toner cartridge, a housing of the image forming unit main body, and an interior of the image forming apparatus. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is intended to provide a developer storage container, an image forming unit and an image forming apparatus capable of preventing scattering of a developer upon detaching of the developer storage container, and capable of preventing the developer from contaminating surroundings. 
     According to an aspect of the present invention, there is provided a developer storage container including a storage portion for storing a developer therein, an opening for ejecting the developer stored in the storage portion, and an opening-and-closing member for opening and closing the opening. A concave portion is formed on the opening-and-closing member so that the concave portion faces the opening. 
     Since the opening-and-closing member has the convex portion at the position facing the opening, the developer is prevented from adhering to an outer surface of the shutter. Therefore, it becomes possible to prevent the developer from scattering, and to prevent the developer from contaminating the surroundings. 
     According to another aspect of the present invention, there is provided an image forming unit including the developer storage container. 
     According to further aspect of the present invention, there is provided an image forming apparatus including the developer storage container. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific embodiments, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the attached drawings: 
         FIG. 1  is a schematic sectional view showing a printer as an image forming apparatus according to the first embodiment of the present invention; 
         FIG. 2  is a schematic sectional view showing an image forming unit according to the first embodiment; 
         FIG. 3  is a perspective view showing a toner cartridge according to the first embodiment; 
         FIG. 4  is a sectional view showing a state where a shutter of the toner cartridge is in a closing position according to the first embodiment; 
         FIG. 5  is a sectional view showing a state where the shutter of the toner cartridge is in an opening position according to the first embodiment; 
         FIG. 6  is an enlarged sectional view showing a main part of the shutter according to the first embodiment in a state where the shutter is not yet mounted to the toner cartridge; 
         FIG. 7  is a sectional view showing a state where the toner cartridge is detached from an image forming unit main body according to the first embodiment; 
         FIG. 8  shows a state where a shutter of a toner cartridge is in the closing position according to a comparison example; 
         FIG. 9  shows a state where the toner cartridge is detached from an image forming unit main body according to the comparison example; 
         FIG. 10  is a sectional view showing a state where a shutter of a toner cartridge is in a closing position according to the second embodiment of the present invention; 
         FIG. 11  is an enlarged sectional view showing a main part of the shutter according to the second embodiment, and 
         FIG. 12  is a diagram showing a pressure applied to the shutter when the shutter rotates from the opening position toward the closing position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, embodiments of the present invention will be described with reference to drawings. Description will be made of a color printer as an example of an image forming apparatus. 
     First Embodiment 
       FIG. 1  is a schematic sectional view showing a printer as an example of an image forming apparatus according to the first embodiment of the present invention.  FIG. 2  is a schematic sectional view showing an image forming unit according to the first embodiment.  FIG. 3  is a perspective view showing a toner cartridge of the image forming unit according to the first embodiment. In this regard, the image forming units  16 Bk,  16 Y,  16 M and  16 C (described later) have the same configurations, and therefore  FIGS. 2 and 3  show the image forming unit  16 Bk only. 
     As shown in  FIG. 1 , the printer  10  includes a medium cassette  11  at a lower part thereof. The medium cassette  11  stores a stack of sheets (i.e., media) P. A medium feeding mechanism is provided on a front side (i.e., right side in  FIG. 1 ) of the medium cassette  1 . The medium feeding mechanism is configured to feed the sheets P one by one into a conveying path. The medium feeding mechanism includes a hopping roller  13   a , a separating device  13   b  and the like. Conveying rollers  14  are provided on a downstream side of the medium feeding mechanism in a conveying direction of the sheet P along the conveying path. 
     The conveying rollers  14  are configured to convey the sheet P to an image forming portion Ar 1  provided on a downstream side of the conveying rollers  14  in the conveying direction of the sheet P. 
     The image forming portion Ar 1  includes the image forming units (also referred to as image drum units)  16 Bk,  16 Y,  16 M and  16 C. The image forming units  16 Bk,  16 Y,  16 M and  16 C are arranged in this order from an upstream side to a downstream side in the conveying direction of the sheet P. The image forming units  16 Bk,  16 Y,  16 M and  16 C are respectively configured to form toner images (i.e., developer images) of black, magenta, yellow and cyan. The image forming units  16 Bk,  16 Y,  16 M and  16 C are detachably mounted to a main body of the printer  10 . 
     The image forming portion Ar 1  further includes a transfer unit u 1  provided along and below the image forming units  16 Bk,  16 Y,  16 M and  16 C. The image forming portion An further includes LED (Light Emitting Diode) heads  22  as an exposure device provided so as to face photosensitive drums  31  (described below) of the image forming units  16 Bk,  16 Y,  16 M and  16 C. 
     Each of the image forming units  16 Bk,  16 Y,  16 M and  16 C includes a main body (i.e., an image forming unit main body)  23  and a toner cartridges  41  (i.e., a developer storage container) detachably mounted to the image forming unit main body  23 . The toner cartridges  41  of the image forming units  16 Bk,  16 Y,  16 M and  16 C respectively store toner T (i.e., developer) of black, yellow, magenta and cyan. 
     The photosensitive drum  31  (i.e., an image bearing body) is rotatably provided in the image forming unit main body  23 . The photosensitive drum  31  rotates at a constant speed by a power transmitted from a not shown driving motor (i.e., a driving source). A charging roller  32  (i.e., a charging member) is rotatably provided so as to contact the photosensitive drum  32 . The charging roller  32  is applied with a predetermined voltage by a charging power source (not shown). The charging roller  32  rotates in a direction opposite to the photosensitive drum  31 , and uniformly charges a surface of the photosensitive drum  31 . The LED head  22  emits light so as to expose the surface of the photosensitive drum  31 , and forms a latent image on the surface of the photosensitive drum  31 . 
     A developing unit  30  is provided adjacent to the photosensitive drum  31 . The developing unit  30  is configured to develop the latent image on the surface of the photosensitive drum  31  to form a toner image (i.e., a developer image). The developing unit  30  includes a developing roller  33  (i.e., a developer bearing body) rotatably provided so as to contact or face the photosensitive drum  31 . The developing roller  33  rotates in a direction opposite to the photosensitive drum  31 , and causes the toner T to adhere to the latent image. The developing unit  30  further includes a toner supply roller  34  (i.e., a developer supply member) rotatably provided so as to contact the developing roller  33 . The toner supply roller  34  rotates in the same direction as the developing roller  33 , and supplies the toner T to the developing roller  33 . A circumferential speed of the toner supply roller  34  is different from a circumferential speed of the developing roller  33  by a predetermined value. The developing unit  30  further includes a developing blade  35  (i.e., a developer layer regulating member) is provided so that a tip of the developing blade  35  contacts the developing roller  33 . The developing blade  35  regulates a thickness of a layer of the toner T on the surface of the developing roller  33 . The developing unit  30  is configured to perform development using a single component developing method. Therefore, the toner T is a non-magnetic single component toner. 
     Further, a cleaning device  36  is provided so as to face the photosensitive drum  31 . The cleaning device  36  includes a cleaning blade  37  as a cleaning member made of a resilient body. A tip of the cleaning blade  37  is pressed against the photosensitive drum  31  with a predetermined pressure. The cleaning blade  37  scrapes off the toner T remaining on the surface of the photosensitive drum  31  after transfer of the toner image. The cleaning device  36  further includes a spiral  38  that conveys the toner T scraped off by the cleaning blade  37 . 
     The transfer unit u 1  includes a driving roller r 1  (i.e., a driving member), and a driven roller r 2  (i.e., a driven member), and a transfer belt  15  (i.e., a conveying member) stretched around the driving roller r 1  and the driven roller r 2 . The transfer belt  15  is moved by a rotation of the driving roller r 1 . The transfer unit u 1  further includes transfer rollers  21  (i.e., transfer members) provided so as to face the photosensitive drums  31 . The transfer belt  15  and the transfer rollers  21  are connected to not shown transfer power sources, and are applied with predetermined transfer voltages. 
     A fixing unit  17  (i.e., a fixing device) is provided on a downstream side of the image forming unit Ar 1  in the conveying direction of the sheet P. The fixing unit  17  is configured to apply heat and pressure to the sheet P thereby to fix the toner image to the sheet P. Conveying rollers  18  are provided on a downstream side of the fixing unit  17 , and ejection rollers  19  are provided on a downstream side of the conveying rollers  18 . The conveying rollers  18  are configured to convey the sheet P with the fixed toner image. The ejection rollers  19  are configured to eject the sheet P outside the printer  10 . A stacker portion  20  is provided on an upper wall of a housing Cs 1  of the printer  10 , and the ejected sheet P is placed on the stacker portion  20 . 
     In each of the image forming units  16 Bk,  16 Y,  16 M and  16 C, the photosensitive drum  31  rotates, and the surface of the photosensitive drum  31  is uniformly charged by the charging roller  32 . The surface of the photosensitive drum  31  is exposed with light emitted by the LED head  22 , and a latent image is formed on the surface of the photosensitive drum  31 . 
     In the developing unit  30 , the toner supply roller  34  supplies the toner T to the developing roller  33  by means of a potential difference between the toner supply roller  34  and the developing roller  33 , and also scrapes off excess toner on the developing roller  33 . 
     As the developing roller  33  rotates, the toner T on the developing roller  33  is regulated by the developing blade  35 , and a toner layer of a constant thickness is formed on the developing roller  33 . When the toner T on the developing roller  33  reaches a region (i.e., a developing region) facing the photosensitive drum  31 , the toner T adheres to the latent image on the photosensitive drum  31  by means of electrostatic force caused by the latent image on the photosensitive drum  31 , so that a toner image is formed. 
     The sheets P stored in the medium cassette  11  are fed and separated into a single sheet P by the hopping roller  13   a  and the separation device  13   b . The conveying rollers  14  correct skew of the sheet P, and convey the sheet P to the image forming portion Ar 1 . 
     The sheet P reaching the image forming portion An is conveyed by the transfer belt  15 , and passes through between the image forming units  16 Bk,  16 Y,  16 M and  16 C and the transfer rollers  21 . As the sheet P passes through between the image forming units  16 Bk,  16 Y,  16 M and  16 C and the transfer rollers  21 , toner images of respective colors are transferred to the sheet P by the transfer rollers  21 . As a result, a color toner image is transferred to the sheet P. 
     Then, the sheet P is conveyed to the fixing unit  17 , and the color toner image is fixed to the sheet P. The sheet P is conveyed by the conveying rollers  18 , and is ejected outside the printer  10  by the ejection rollers  19 . The ejected sheet P is placed on the stacker portion  20 . 
     In this regard, the toner cartridges  41  are detachably mounted to the image forming unit main bodies  23  of the image forming units  16 Bk,  16 Y,  16 M and  16 C. The toner cartridges  41  supply the toner T to the developing units  30  of the image forming unit main bodies  23 . 
     As shown in  FIG. 2 , the toner cartridge  41  has a case  43  (i.e., a housing). The case  43  is divided by a partition wall  101  into a toner storage chamber  102  (i.e., a developer storage portion or a reservoir) and a waste toner storage chamber  103  (i.e., a waste developer storage chamber). The toner storage chamber  102  stores a fresh toner T. The waste toner storage chamber  102  stores a waste toner having been conveyed by the spiral  38 . 
     The case  43  includes an upper half portion  43 U having a rectangular cross section and a lower half portion  43 L having a semicircular cross section (i.e., a semicylindrical shape). An opening  44  (i.e., a developer opening) is formed on a bottom of the lower half portion  43 L. The toner T (stored in the toner storage chamber  102 ) is supplied to the image forming unit main body  23  through the opening  44 . The opening  44  is elongated in a longitudinal direction of the toner cartridge  41 . In this regard, the longitudinal direction of the toner cartridge  41  is the same as a widthwise direction of the transfer belt  15 , and is perpendicular to the conveying direction of the sheet P. 
     The image forming unit main body  23  has a housing Cs 2  including a lower frame fL and an upper frame fU. A mounting portion S 1  is formed on the upper frame fU. The mounting portion S 1  is provided for mounting the toner cartridge  41 . The mounting portion S 1  has a concave shape having a semicircular cross section (i.e., semicylindrical shape) corresponding to the lower half portion  43 L of the toner cartridge  41 . The mounting portion S 1  is elongated in the widthwise direction of the transfer belt  15 , and is perpendicular to the conveying direction of the sheet P. A receiving opening  45  (i.e., a developer receiving portion) is formed on the mounting portion S 1 . The receiving opening  45  is provided so as to correspond to the opening  44  of the toner cartridge  41 . The receiving opening  45  receives the toner T supplied via the opening  44 . The opening  44  and the receiving opening  45  have the same shape and the same size. When the toner cartridge  41  is mounted to the image forming unit main body  23 , the opening  44  and the receiving opening  45  are aligned with each other. 
     A shutter  42  (i.e., an opening-and-closing member or a shield member) is provided in the toner storage chamber  102  for opening and closing the opening  44 . The shutter  42  has a cylindrical shape. The shutter  42  is movable. More specifically, in this embodiment, the shutter  42  is rotatable about a rotation axis that coincides with a center axis of the shutter  42  having the cylindrical shape. The shutter  42  is rotatable in a direction shown by an arrow B ( FIG. 4 ) and in an opposite direction. As the shutter  42  rotates (more specifically, rotates), an inner circumferential surface of the lower half portion  43 L and an outer circumferential surface of the shutter  42  slide with respect to each other. 
     A supply opening  42   a  (i.e., a developer supply portion) and a connecting portion  42   b  are formed on the shutter  42 . The supply opening  42   a  is provided at a predetermined position in a circumferential direction corresponding to the opening  44 . A connecting portion  42   b  is provided at a position different from the supply opening  42   a . The supply opening  42   a  and the connecting portion  42   b  are elongated in an axial direction (i.e., the longitudinal direction of the toner cartridge  41 ). 
     When an operator operates an operation lever  46  formed integrally with the shutter  42  to rotate the shutter  42  in a direction shown by an arrow A, the shutter  42  rotates in the direction shown by the arrow A by a predetermined amount, and reaches an opening position where the shutter  42  opens the opening  44 . In the opening position, the opening  44  and the supply opening  42   a  are aligned with each other, so that the toner storage chamber  102  and an interior of the image forming unit main body  23  are connected with each other. In this state, the toner T in the toner storage chamber  102  is supplied to a toner hopper  23   a  (i.e., a developing holding portion) of the image forming unit main body  23  via the opening  44 , the supply opening  42   a  and the receiving opening  45 . The toner hopper  23   a  is a portion where the toner T is temporality held. 
     Further, when the operator operates the operation lever  46  to rotate the shutter  42  in the direction shown by the arrow B, the shutter  42  rotates in the direction shown by the arrow B, and reaches a closing position where the shutter  42  closes the opening  44 . In the closing position, the opening  44  and the supply opening  42   a  are displaced from each other, so that the toner storage chamber  102  and the interior of the image forming unit main body  23  are not connected with each other. Therefore, supply of the toner T is stopped. 
     If an amount of the toner T stored in the toner cartridge  31  becomes small, the operator replaces the toner cartridge  41  with new toner cartridge. Upon replacement of the toner cartridge  41 , when the operator operates the operation lever  46  to rotate the shutter  42  in the direction shown by the arrow B from the opening position to the closing position to close the opening  44 , the toner T adhering to the receiving opening  45  of the image forming unit main body  23  may adhere to the shutter  42 . Therefore, when the toner cartridge  41  is detached from the image forming unit main body  23 , the toner T adhering to the shutter  42  may scatter outside. The scattered toner may contaminate components around the opening  44  such as, for example, the case  43  of the cartridge  41 , the housing Cs 2  of the image forming unit main body  23 , and an interior of the housing Cs 1  of the printer  10 . 
     Therefore, the first embodiment is intended to prevent the toner T (adhering to the receiving opening  45  of the image forming unit main body  23 ) from adhering to the shutter  42  when the shutter  42  closes the opening  44 . 
     Next, mounting and detachment of the toner cartridge  41  to and from the image forming unit main body  23  will be described. 
       FIG. 4  is a sectional view showing a state where the shutter  42  of the toner cartridge  41  is in the closing position.  FIG. 5  is a sectional view showing a state where the shutter  42  of the toner cartridge  41  is in the opening position.  FIG. 6  is an enlarged sectional view showing a main part of the shutter  42  in a state where the shutter  42  is not yet mounted to the toner cartridge  41 .  FIG. 7  is a sectional view showing a state where the toner cartridge  41  is detached from the image forming unit main body  23 . 
     As described above, in  FIG. 4 , the toner cartridge  41  is mounted to the mounting portion S 1  of the image forming unit main body  23  of the image forming unit (for example, the image forming unit  16 Bk). Supporting portions  111  and  112  are formed on both edges of the mounting portion S 1  so as to protrude upward. Supported portions  113  and  114  are formed on the lower half portion  43 L of the case  43  so as to protrude horizontally. When the toner cartridge  41  is mounted to the image forming unit main body  23 , the supporting portions  111  and  112  contact the supported portions  113  and  114  from below, so that the toner cartridge  41  is correctly positioned with respect to the image forming unit main body  23 . In a state where the supporting portions  111  and  112  contact the supported portions  113  and  114 , the opening  44  and the receiving opening  45  are aligned with each other. 
     A closing portion  50  is provided at a predetermined portion of the shutter  42 . More specifically, the closing portion  50  is provided at a portion that faces the opening  44  in a state where the shutter  42  is in the closing position. The closing portion  50  is elongated in the axial direction of the shutter  42  (i.e., the longitudinal direction of the toner cartridge  41 ). 
     A recess portion  51  is formed on an outer circumference of the closing portion  50 . The recess portion  51  is in the form of a groove having a length in the axial direction of the shutter  42 . The recess portion  51  has a width over a predetermined region in the circumferential direction of the shutter  42 . As shown in  FIG. 6 , step portions St 1  and St 2  (i.e., first and second regulating portions or abutting portions) are formed on both ends of the recess portion  51 . The step portions St 1  and St 2  are provided so as to correspond to the opening  44 . Further, a pair of seal members  52  and  53  (i.e., first and second resilient members) are provided so as to be pressed against the step portions St 1  and St 2 . The seal members  52  and  53  are apart from each other in the rotational direction (i.e., movable direction) of the seal member  42 . The seal members  52  and  53  extend in the longitudinal direction of the recess portion  51 . The seal members  52  and  53  are bonded to a bottom surface S 4  of the recess portion  51  using a not shown double-faced adhesive tape (i.e., a fixing member) in such a manner that the seal members  52  and  53  contact the inner circumferential surface  43 M of the lower half portion  43 L. The recess portion  51 , the seal members  52  and  53  and the step portions St 1  and St 2  constitute a concave portion D. 
     In this regard, the seal member  52  is provided on an upstream side of the seal member  53  in a direction in which the shutter  42  rotates from the opening position toward the closing position. More specifically, the seal member  52  is provided on the upstream side of the seal member  53  in the rotational direction shown by the arrow B. Further, a width of each of the seal members  52  and  53  in the circumferential direction of the shutter  42  is wider than a width of the opening  44  in the same direction. The step portion St 1  is provided on the upstream side of the seal member  52  in the rotational direction shown by the arrow B. The position of the step portion St 1  is determined based on the widths of the opening  44  and the seal member  52 . The step portion St 2  is provided on the downstream side of the seal member  53  in the rotational direction shown by the arrow B. The position of the step portion St 2  is determined based on the widths of the opening  44  and the seal member  53 . 
     The seal members  52  and  53  are made of resilient material whose hardness is lower than hardness of plate material of the housing Cs 2  of the image forming unit main body  23  and the case  43  of the toner cartridge  41 . For example, the seal members  52  and  53  are made of urethane sponge. As shown in  FIG. 6 , in a state where the shutter  42  is not yet mounted to the toner cartridge  41 , outer circumferential surfaces S 3  of the seal members  52  and  53  are positioned outside an outer circumferential surface S 2  of the shutter  42 . That is, a distance h 2  from a bottom surface S 4  of the recess portion  51  to the outer circumferential surface S 3  of the seal members  52  and  53  is longer than a distance h 1  from the bottom surface S 4  of the recess portion  51  to the outer circumferential surface S 2  of the shutter  42 . The shutter  42  is inserted into the toner cartridge  41  while causing the seal members  52  and  53  to be compressed (deformed). 
     Therefore, in a state where the shutter  42  is in the closing position, the outer circumferential surface S 2  of the shutter  42  and the inner circumferential surface of the lower half portion  43 L tightly contact each other due to a force caused by deformation of the seal members  52  and  53 . Accordingly, the toner T in the toner cartridge  41  is prevented from leaking outside. 
     Further, the seal members  52  and  53  are pressed against the step portions St 1  and St 2 , and therefore deformation of the seal members  52  and  53  in the circumferential direction can be prevented. Therefore, sealing between the outer circumferential surface S 2  of the shutter  42  and the inner circumferential surface  43 M of the lower half portion  43 L can be ensured. In the state where the toner cartridge  41  is mounted to the image forming unit main body  23 , when the operator operates the operation lever  46  ( FIG. 4 ) to rotate the shutter  42  in the direction shown by the arrow B from the opening position to the closing position to close the opening  44 , the opening  44  and the supply opening  42   a  are displaced from each other. In this state, the closing portion  50  of the shutter  42  faces the opening  44  and the receiving opening  45 . 
     In this regard, as shown in  FIG. 4 , the toner T is divided by the closing portion  50  into a toner Ta in the toner storage chamber  102  and a toner Tb in the image forming unit main body  23 . In this state, since the closing portion  50  has the recess portion  51 , a clearance CL where no toner T exists is formed between the closing portion  50  and a top surface of the toner Tb in the image forming unit main body  23 . 
     Therefore, in the state where the shutter  42  is in the closing position, the toner Tb in the image forming unit main body  23  does not adhere to the surface of the shutter  42  (more specifically, the bottom surface S 4  of the recess portion  51 ). 
     Further, since a width (i.e., a distance) between the seal members  52  and  53  is wider than the width of the opening  44 , the toner Tb in the image forming unit main body  23  does not adhere to the seal members  52  and  53 . 
     As a result, as shown in  FIG. 7 , when the toner cartridge  41  is detached from the image forming unit main body  23 , scattering of the toner T does not occur. Accordingly, components around the opening  44  of the toner cartridge  41  such as, for example, the case  43  of the toner cartridge  41 , the housing Cs 2  of the image forming unit main body  23  and the housing Cs 1  of the printer  10  ( FIG. 2 ) are not contaminated with the toner T. 
     In addition, seal members  55  and  56  (i.e., a second seal member) are provided on the mounting portion S 1  of the image forming unit main body  23 . The seal members  55  and  56  are located on both ends of the receiving opening  45 , and contact the outer circumferential surface of the lower half portion  43 L along the receiving opening  45 . The seal members  55  and  56  are made of resilient material whose hardness is lower than hardness of plate material of the housing Cs 2  of the image forming unit main body  23  and the case  43  of the toner cartridge  41 . For example, the seal members  55  and  56  are made of urethane sponge. The seal members  55  and  56  have end surfaces facing each other. The seal members  55  and  56  extend in a longitudinal direction of the receiving opening  45  (i.e., in the longitudinal direction of the mounting portion S 1 ). The end surfaces of the seal members  55  and  56  are aligned with inner an peripheral wall of the receiving opening  45 . 
     As shown in  FIG. 7 , taper surfaces tp 1  and tp 2  are formed on the inner periphery of the opening  44 . The taper surfaces tp 1  and tp 2  are formed so that a thickness of the inner periphery of the opening  44  decreases toward inside the opening  44 . The taper surfaces tp 1  and tp 2  are formed so as to face outward (i.e., an outer circumferential side) of the lower half portion  43 L. When the toner cartridge  41  is mounted to the image forming unit main body  23 , portions of the seal members  55  and  56  corresponding the taper surfaces tp 1  and tp 2  are pressed by the lower half portion  43 L. In this state, as shown in  FIG. 4 , taper surfaces  55   a  and  56   a  are formed on the seal members  55  and  56 . The taper surfaces  55   a  and  56   a  are formed so that the thicknesses of the seal members  55  and  56  increase toward inside the opening  44 . 
     Since most part of the inner periphery of the opening  44  is covered with the taper surfaces  55   a  and  56   a , the toner Tb existing in the vicinity of the opening  44  and the receiving opening  45  is prevented from entering into between the outer circumferential surface of the lower half portion  43 L and the mounting portion S 1 . Further, an area where the inner periphery of the opening  44  faces the toner Tb in the image forming unit main body  23  is reduced. Therefore, the toner Tb is prevented from adhering to the inner periphery of the opening  44 . 
     In this regard, as shown in  FIG. 7 , in a state where the toner cartridge  41  is detached from the image forming unit main body  23 , the seal members  55  and  56  are not pressed by the lower half portion  43 L. Therefore, upper surfaces of the seal members  55  and  56  become substantially flat. 
     As described above, according to the first embodiment of the present invention, the closing portion  50  has the recess portion  51 , and therefore the toner T is prevented from adhering to the outer circumferential surface of the shutter  42  when the shutter  42  is in the closing position. Therefore, when the toner cartridge  41  is detached from the image forming unit main body  23 , scattering of the toner T can be prevented. Accordingly, components around the opening  44  of the toner cartridge  41  such as, for example, the case  43  of the toner cartridge  41 , the housing Cs 2  of the image forming unit main body  23  and the housing Cs 1  of the printer  10  are not contaminated with the toner T. 
     COMPARISON EXAMPLE 
       FIGS. 8 and 9  show a comparison example with respect to the first embodiment.  FIG. 8  shows a state where the shutter  42  is in the closing position.  FIG. 9  shows a state where the toner cartridge  41  is detached from the image forming unit main body  23 . For convenience, same reference numerals as those of the first embodiment are used. 
     In the comparison example, the recess portion  51  (see  FIGS. 4 through 7 ) is not provided on the closing portion  50 . Instead, a seal member  60  is provided on the closing portion  50 . When the shutter  42  is in the closing position, the toner T is divided by the closing portion  50  into a toner Ta in the toner storage container  102  and a toner Tb in the image forming unit main body  23 . In this state, the toner Tb in the image forming unit main body  23  adheres to the surface of the seal member  60 . 
     Therefore, as shown in  FIG. 9 , when the toner cartridge  41  is detached from the image forming unit main body  23 , the toner T adhering to the seal member  60  may scatter outside. The scattered toner may contaminate components around the opening  44  such as, for example, the case  43  of the cartridge  41 , the housing Cs 2  of the image forming unit main body  23 , and the interior of the housing Cs 1  of the printer  10 . 
     Second Embodiment 
     Next, the second embodiment of the present invention will be described. Components which are the same as those of the first embodiments are assigned the same reference numerals. Regarding advantages obtained by these components, descriptions in the first embodiment are herein incorporated. 
       FIG. 10  is a sectional view showing a state where a shutter  42  of a toner cartridge  41  is in a closing position according to the second embodiment.  FIG. 11  is an enlarged sectional view showing a main part of the shutter  42  according to the second embodiment. 
     The shutter  42  (i.e., an opening-and-closing member or a shield member) has a taper surface tp 3  (i.e., slope portion) formed on an inner periphery of a supply opening  42   a  (i.e., developer supply portion). More specifically, the taper surface tp 3  is formed on an upstream part Wu ( FIG. 11 ) of the inner periphery of the supply opening  42   a . Further, the taper surface tp 3  is formed so that a thickness of the shutter  42  decreases toward inside the supply opening  42   a . The taper surface tp 3  is located at a downstream side of the recess portion  51  in the rotational direction of the shutter  42  (shown by the arrow B) from the opening position to the closing position. The taper surface tp 3  is formed so that a thickness of the shutter  42  decreases toward inside the supply opening  42   a . The taper surface tp 3  is formed so as to face inward (i.e., an inner circumferential side) of the shutter  42 . 
     When the shutter  42  rotates from the opening position to the closing position, the toner T (i.e., developer) is divided into two a toner Ta in toner storage chamber  102  (i.e., a developer storage portion or a reservoir) and a toner Tb in the image forming unit main body  23 . In this state, a toner Te existing on or in the vicinity of the taper surface tp 3  slides in a direction shown by an arrow C in  FIG. 11  along the taper surface tp 3 . Therefore, a pressure applied to the shutter  42  by the toner Te can be reduced. 
     Next, description will be made of the pressure applied to the shutter  42  by the toner Te during the rotation of the shutter  42  from the opening position to the closing position. As shown in  FIG. 11 , a downstream part of the inner periphery of the opening  44  (i.e., a developer opening) is expressed as Wd. A gap between the above described part Wu of the inner periphery of the supply opening  42   a  and the part Wd of the inner periphery of the opening  44  is expressed by At as shown in  FIG. 11 . 
       FIG. 12  is a diagram showing a pressure applied to the shutter  42  when the shutter  42  rotates from the opening position toward the closing position. A horizontal axis shows the gap At (mm), and a vertical axis shows the pressure P (Pa). 
     A line L 1  (shown by a solid line) indicates a pressure P (Pa) when the taper surface Tp 3  is not formed on the part Wu of the inner periphery of the supply opening  42   a . A line (shown by a dashed line) L 2  indicates a pressure P (Pa) when the taper surface Tp 3  is formed on the part Wu of the inner periphery of the supply opening  42   a.    
     As shown in  FIG. 12 , as the gap At decreases, the pressure P (Pa) increases. The pressure P reaches the maximum value P 1  (Pa) when the gap Δt is t 1  (mm). 
     When the taper surface Tp 3  is not formed on the part Wu of the inner periphery of the supply opening  42   a , the pressure P exhibits the maximum value P 1  (Pa). When the taper surface Tp 3  is formed on the part Wu of the inner periphery of the supply opening  42   a , the pressure P exhibits the maximum value P 2  (Pa). It is understood that the maximum value P 2  (Pa) is remarkably smaller than the maximum value P 1  (Pa). 
     As described above, according to the second embodiment of the present invention, the taper surface tp 3  is formed on the part Wu of the inner periphery of the supply opening  42   a  of the shutter  42 . Therefore, during the rotation of the shutter  42  from the opening position to the closing position, a pressure applied to the shutter  42  by the toner Te can be reduced. 
     Further, since the pressure (force) applied to the shutter  42  by the toner T can be reduced, the entry of the toner T into between the outer circumferential surface of the lower half portion  43 L and the mounting portion S 1  can be prevented. 
     In the above described embodiments, a color printer has been described as an example of the image forming apparatus. However, the present invention is also applicable to a monochrome printer. Further, the present invention is also applicable to an image forming apparatus such as a copier, a facsimile machine, a multifunction peripheral or the like. 
     While the preferred embodiments of the present invention have been illustrated in detail, it should be apparent that modifications and improvements may be made to the invention without departing from the spirit and scope of the invention as described in the following claims.