Patent Publication Number: US-8989634-B2

Title: Developer case that suppresses clogging due to developer, developer replenishment unit having the same, and image forming apparatus having the same

Description:
INCORPORATION BY REFERENCE 
     This application is based upon and claims the benefit of priority from the corresponding Japanese Patent application No. 2011-217171, filed Sep. 30, 2011, the entire contents of which is incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a developer case that replenishes a developer, such as toner, and the developer replenishment unit and an image forming apparatus equipped with same. 
     Presently, image forming apparatuses such as printers use a developer replenishment unit that includes a developing device and a toner container (developer case) positioned above the developing device. Toner is supplied to the developing device from a toner supply unit provided in the toner container. 
     When the toner container is located above the developing device, the developer replenishment unit is dimensioned so that its height corresponds to the developing device and the toner container. As a result, the space occupied by the image forming apparatus in the vertical direction is increased. 
     In order to reduce the space occupied by the image forming apparatus in the vertical direction as much as possible, a structure in which the toner container and the developing device are arranged in a substantially horizontal direction may be used. However, when the toner container is located at such a position, the developing device is not replenished with the toner from the toner container due to the natural dropping of the toner. That is, it is necessary to provide a transportation path in the horizontal direction from the toner container to the developing device. In this situation, the horizontal transportation path is provided above the toner container and the developing device. Thus, a supply member that scoops up the toner contained in the toner container is needed. 
     However, since the toner is transported upwardly against gravity, with such a structure, transportation efficiency tends to decrease. In order to compensate for the decrease in transportation efficiency of the supply member, transportation performance in the horizontal transportation path, through which the toner having been transported upward is transported, may be increased. However in such a case, the toner tends to clog the horizontal transportation path on the downstream side. To this end, clogging due to the toner is particularly likely to occur near a discharge port, through which the toner drops into the developing device, so as to replenish the developing device with the toner. This is due to the fluidity of the toner degrading by an amount corresponding to the amount of the toner required to be replenished and the amount of the developer existing in the developing device. 
     SUMMARY 
     A developer case according to an embodiment of the present disclosure is provided that includes a main body, a first transportation portion, a first transportation member, a supply member, a discharge port, and a second transportation portion. The main body has a bottom wall and contains developer. The first transportation portion has a first region and a second region. The first region is located above the bottom wall of the main body and receives the developer from the main body. The second region extends from the first region so as to project further in a first direction than the main body does. The first transportation member is located in the first transportation portion and transports the developer in the first direction. The supply member is located in the main body and supplies the developer to the first region of the first transportation portion. The discharge port is located in the second region of the first transportation portion. The developer is discharged through the discharge port. The second transportation portion has an inlet port communicating with the second region of the first transportation portion. The developer that has not been discharged through the discharge port is supplied to the second transportation portion through the inlet port. The second transportation portion transports the developer in a second direction. 
     A developer replenishment unit according to another embodiment of the present disclosure is provided that includes a developing device, and the above-described developer case. The developing device has a housing, a developer transportation path set in the housing, and a receiving port that is located at a position opposite a discharge port of the housing and allows the developer that is discharged through the discharge port to pass therethrough so that the housing receives the developer. 
     An image forming apparatus according to another embodiment of the present disclosure is provided that includes an image carrying body, the above-described developing device, and the above-described developer case. An electrostatic latent image is formed on the image carrying body and the image carrying body carries a developer image formed by visualizing the electrostatic latent image using developer. 
     Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a sectional view illustrating an internal structure of an image forming apparatus according to an embodiment of the present disclosure; 
         FIG. 2  is a plan view illustrating a developing device according to the embodiment of the present disclosure; 
         FIG. 3  illustrates a toner replenishment portion of the developing device according to the embodiment of the present disclosure; 
         FIG. 4  is a side view of a toner container of an embodiment of the present disclosure; 
         FIG. 5  is a plan view of the toner container of the embodiment of the present disclosure illustrated in  FIG. 4 ; 
         FIG. 6  is a perspective view of the toner container of the embodiment of the present disclosure illustrated in  FIG. 4 ; 
         FIG. 7  is a plan view of a toner container of another embodiment of the present disclosure; 
         FIG. 8  is a plan view of a toner container of yet another embodiment of the present disclosure; and 
         FIG. 9  is a reference drawing of another toner container. 
     
    
    
     DETAILED DESCRIPTION 
     A toner container  30  (developer case) according to an embodiment of the present disclosure will be described below with reference to the drawings.  FIG. 1  is a sectional view schematically illustrating the structure of an image forming apparatus  1  including the toner container  30  according to the embodiment of the present disclosure. The image forming apparatus  1  includes an optical scanning device  11 , a developing device  20 , a charger  13 , a photoconductor drum  14  (image carrying body), a transfer roller  15 , a fixing device  16 , and a sheet feed cassette  17 . In some cases, the developer case is included in the developing device. The unit combined the developer case and the developing device is called a developer replenishment unit. 
     The photoconductor drum  14  is a cylindrical member. An electrostatic latent image and a toner image are formed on a circumferential surface of the photoconductor drum  14 . The photoconductor drum  14  receives a drive force from a motor (not shown), thereby being rotated in a direction that is the clockwise direction in  FIG. 1 . The charger  13  substantially uniformly charges the surface of the photoconductor drum  14 . 
     The optical scanning device  11  includes a light source, a deflector, a scanning lens, and an optical element, and so forth. The light source uses a laser diode or the like. The optical scanning device  11  radiates a laser beam in accordance with image data toward the circumferential surface (scanned surface) of the photoconductor drum  14 , which is substantially uniformly charged by the charger  13 , so as to form an electrostatic latent image of the image data. 
     The developing device  20  supplies toner to the circumferential surface of the photoconductor drum  14 , on which the electrostatic latent image has been formed, thereby forming a toner image. The developing device  20  includes components such as a developing roller, which carries the toner, and screws, which agitate and transport the toner. The toner image formed on the photoconductor drum  14  is transferred to a recording sheet picked up from the sheet feed cassette  17  and transported through a transportation path P. The developing device  20  is replenished with the toner from the toner container  30 . The developing device  20  and the toner container  30  will be described in detail hereinafter. 
     The transfer roller  15  is positioned below the photoconductor drum  14  so as to face the photoconductor drum  14 , thereby forming a transfer nip therebetween. The transfer roller  15  is formed of an electrically conductive rubber material or the like. A transfer bias is applied to the transfer roller  15  by a bias application unit (not shown). The transfer roller  15  causes the toner image formed on the photoconductor drum  14  to be transferred to the recording sheet. 
     The fixing device  16  includes a fixing roller  160 , which includes a heater therein, and a pressure roller  161  located at a position opposite the fixing roller  160 . The fixing device  16  causes the toner image formed on the recording sheet to be fixed to the recording sheet through heating performed while the recording sheet on which the toner image is formed is being transported. 
     Description of Developing Device 
       FIG. 2  is a plan view of an internal structure of the developing device  20 . The developing device  20  includes a developing housing  210  (housing). The developing housing  210  has a box shape elongated in a single direction (axial direction of a developing roller  21 ). An internal space  220  is formed in the developing housing  210 . The developing roller  21 , a first transportation screw  23  and a second transportation screw  24  are positioned parallel to one another in the internal space  220 . When a one-component development method is used, the internal space  220  is filled with toner that is used as a developer. When a two-component development method is used, the internal space  220  is filled with a mixture of carrier formed of a magnetic material and toner, the mixture serving as the developer. 
     In the internal space  220 , toner is transported while being agitated, successively supplied to the developing roller  21 , and consumed so as to develop the electrostatic latent image. The toner for replenishment is supplied as appropriate in an amount corresponding to the consumed amount from the toner container  30  (developer case), which will be described hereinafter. The developing roller  21  has a cylindrical shape that extends in the elongated direction of the developing housing  210  and has a sleeve portion, which is rotated, on an outer circumference thereof. When a one-component developing method is used, the toner having been charged by frictional electrification is attracted to the sleeve portion from the second transportation screw  24 . When a two-component developing method is used, the carrier as a magnetic material together with the toner, which is attracted to the carrier by electrostatic force, are attracted from the second transportation screw  24  to a surface of the sleeve portion by an electric field formed by a magnetic pole fixed inside the sleeve portion. The toner (developer) carried on the surface of the sleeve portion is transported to an opening (not shown) formed in the developing housing  210  so as to be supplied to the photoconductor drum  14  opposite the sleeve portion. 
     The internal space  220  of the developing housing  210  is separated into a first path  221  and a second path  222 , which are both elongated in a left-right direction (axial direction), by a separator plate  22 , which extends in the left-right direction. The separator plate  22  is shorter than the width of the developing housing  210  in the left-right direction. An upstream communication path  223  and a downstream communication path  224  are respectively formed at the right and left ends of the separator plate  22 . The upstream communication path  223  and the downstream communication path  224  allow the first path  221  and the second path  222  to communicate with each other. Thus, the developing housing  210  has a circulation path (developer transportation path) formed therein from the first path  221 , the upstream communication path  223 , the second path  222 , to the downstream communication path  224 . 
     The first path  221  contains the first transportation screw  23 , and the second path  222  contains the second transportation screw  24 . The first transportation screw  23  (third transportation member) and the second transportation screw  24  include respective rotation shafts and respective agitating blades protruding from the peripheries of the rotation shafts in a spiral shape. The first transportation screw  23  is rotated about its rotation shaft, thereby transporting the toner in a direction indicated by arrow a in  FIG. 2 . The second transportation screw  24  is rotated about its rotation shaft, thereby transporting the toner in a direction indicated by arrow b in  FIG. 2 . Rotation of the first and second transportation screws  23  and  24  causes the toner to be transported in a circulating manner through the above-described circulation path. 
     The first transportation screw  23  and the second transportation screw  24  of the developing device  20  are covered with a top plate (not shown). The developing device  20  has a toner replenishment port  25  (receiving port), through which the developing device  20  is replenished with the toner. The toner replenishment port  25  is defined by an opening (indicated by a dotted box in  FIG. 2 ) formed in the top plate at an upper position near a right end of the first path  221 . The toner container  30  is located above the toner replenishment port  25 . The toner container  30  has a toner transportation path formed therein. The toner container  30  is combined with the developing device  20  such that the lengthwise direction of the toner container  30  (direction in which the toner transportation path extends) is perpendicular to the lengthwise direction of the developing device  20  (direction in which the developer is transported by the first transportation screw  23 ). The developing device  20  is replenished with toner that drops down from the toner container  30  through the toner replenishment port  25 . 
     Description of Developer Accumulation Portion 
     Next, the flow of the toner, with which the developing device  20  is newly replenished through the toner replenishment port  25 , will be described.  FIG. 3  is a schematic diagram illustrating the toner replenishment port  25 , a toner discharge port  33 , and an area around them. The toner replenishment port  25  is formed in the developing device  20 , and the toner discharge port  33  is formed in the toner container  30 , which will be described later. For convenience of description, in  FIG. 3 , the arrangement of the toner container  30  is rotated by 90 degrees in the horizontal direction. In the actual toner container  30 , a first transportation member  321  extends toward the front side of the page of  FIG. 3 , and the first transportation screw  23  and the first transportation member  321  in the toner container  30  are perpendicular to each other. 
     Toner T 2  supplied through the toner discharge port  33  of the toner container  30  drops into the first path  221 , and is mixed with existing toner T 1 . The mixture of the toner T 2  and T 1  is then transported in a direction indicated by arrow a by the first transportation screw  23 . In so doing, the toner is agitated and charged. 
     Here, the first transportation screw  23  has a transportation capacity reducing portion  26  on the downstream side of the toner replenishment port  25  in the toner transportation direction. The transportation capacity reducing portion  26  is formed by omitting part of an agitating blade of the first transportation screw  23 . In the first transportation screw  23 , the amount of toner to be transported by this blade-omitted portion is decreased compared to other portions that do not have the blade-omitted portion. Because of this, the toner transported through the first path  221  accumulates on the upstream side of the transportation capacity reducing portion  26  in the transportation direction. 
     In an embodiment, the transportation capacity reducing portion  26  is defined by the portion of the first transportation screw  23  where part of the agitating blade is omitted. Alternatively, the first transportation screw  23  may include a bar member positioned parallel to the rotation shaft thereof at a periphery of the agitating blade of thereof, and the transportation capacity reducing portion  26  may be defined by a portion of the first transportation screw where the bar member is located. Because the bar member is attached to the agitating blade, toner transportation capacity can be reduced, and accordingly, the toner can accumulate. 
     With the transportation capacity reducing portion  26 , the toner transported in the direction indicated by arrow a through the first path  221  accumulates at a position immediately upstream of the transportation capacity reducing portion  26  and opposite the toner replenishment port  25 . Thus, an accumulation portion  26 A (developer accumulation portion) is formed. Accordingly, when the amount of the toner in the developing housing  210  is increased due to replenishment of the toner through the toner replenishment port  25 , the toner accumulated in the accumulation portion  26 A blocks the toner replenishment port  25 , thereby suppressing further replenishment of the toner. After that, when the amount of the toner having accumulated in the accumulation portion  26 A decreases due to consumption of the toner in the developing housing  210 , the amount of the toner that blocks the toner replenishment port  25  decreases. This causes the toner to move into the developing housing  210  again through the toner discharge port  33 . 
     When the toner is then forcibly discharged through the toner discharge port  33  of the toner container  30 , while the toner replenishment port  25  is being blocked by the toner in the accumulation portion  26 A, toner is compressed and a toner block is formed. Once the toner block is formed near the toner discharge port  33  and the toner replenishment port  25 , toner replenishment is then prevented, and accordingly, the amount of the toner in the developing housing  210  gradually decreases. As a result, toner image formation on the photoconductor drum  14  is unsatisfactorily performed, leading to image fading or the like. 
     Description of Toner Container 
     Next, the structure and function of the toner container  30  according to an embodiment will be described.  FIG. 4  is a side sectional view of the toner container  30  according to an embodiment of the present disclosure.  FIG. 5  is a plan view of the toner container  30  with a top plate  301  removed. The top plate  301  will be described hereinafter.  FIG. 6  is a perspective view illustrating the positional relationship inside the toner container  30 . 
     The toner container  30  includes a toner containing portion  31  (main body) and a projection portion  31 A. The toner containing portion  31  contains the toner. The projection portion  31 A has the toner discharge port  33 , through which the toner is supplied to the developing device  20 . The toner container  30  also has a first transportation portion  32  and a second transportation portion  34 . The first transportation portion  32  receives the toner from the toner containing portion  31  and transports the toner to the toner discharge port  33 . The second transportation portion  34  returns part of the toner that is not discharged through the toner discharge port  33  to the toner containing portion  31 . 
     The toner containing portion  31  has a container bottom wall  311  (bottom wall), side wall portions  312  and  313 , a front wall portion  314 , and a rear wall portion  315 . The container bottom wall  311  has a substantially arc shape in sectional view and extends in a first direction. The side wall portions  312  and  313  extend vertically upwardly from both sides of the container bottom wall  311 . The front wall portion  314  extends vertically upwardly from a front surface of the container bottom wall  311 . The rear wall portion  315  extends vertically upwardly from the rear surface of the container bottom wall  311 . The upper part of the toner containing portion  31  is closed by the top plate  301 , which is connected to the side wall portions  312  and  313 , the front wall portion  314 , and the rear wall portion  315 . The toner (developer) is contained in this closed space. 
     A rotating paddle  35  (supply member) is located in the toner containing portion  31  such that the rotating paddle  35  is rotatably supported by the toner containing portion  31 . Specifically, the rotating paddle  35  has a shaft portion  352 , which is rotatably supported by shaft support portions  312   a  and  313   b  respectively, formed on the side wall portions  312  and  313 . The rotating paddle  35  is located on the shaft portion  352  and has a paddle portion  351  that agitates and transports the toner in the toner containing portion  31 . The paddle portion  351  is formed of four plate-shaped members, which are positioned in the axial direction of the shaft portion  352  so as to be adjacent to one another. The rotating paddle  35  is rotated in a direction indicated by arrow R in  FIG. 5 , by a motor M 0  positioned externally to the toner container  30 . 
     The first transportation portion  32  is located above the container bottom wall  311  of the toner containing portion  31  along the rear wall portion  315 . The first transportation portion  32  is parallel to the shaft portion  352  of the rotating paddle  35 . The first transportation portion  32  has a semi-cylindrical shape in sectional view, an upper surface side of which opens and a lower surface side of which has a semi-circular shape. The first transportation portion  32  extends in the horizontal direction. The semi-circular lower surface is formed of a first transportation bottom wall  322  formed of a curved surface having a semi-circular section. The first transportation portion  32  has an opening portion  322 B on a side surface thereof opposite the toner containing portion  31  in the axial direction of the rotating paddle  35  so as to communicate with the toner containing portion  31 . The region of the first transportation portion  32  opposite the toner containing portion  31  is defined as a first region A 1  ( FIG. 6 ). The toner contained in the toner containing portion  31  is scooped upward as the rotating paddle  35  rotates, thereby being delivered to the first region A 1  through the opening. 
     In addition to the first region A 1  that opposes the toner containing portion  31 , the first transportation portion  32  has a second region A 2  ( FIG. 6 ) having a cylindrical shape extending from the first region A 1  in a first direction (a direction indicated by an arrow D 1  in  FIG. 5 ) so as to project further outward than does the toner containing portion  31 . The first transportation member  321 , which transports the toner received from the toner containing portion  31  in the first direction, is positioned in the first transportation portion  32  throughout the first region A 1  and the second region A 2 . The first transportation member  321  has a shaft portion  321   a  and a blade portion  321   b  (spiral portion), which has a screw shape and is positioned on the shaft portion  321   a . The first transportation member  321  is rotated in the direction indicated by arrow R 1 , by a motor M 1  (first drive unit, see  FIG. 5 ) positioned externally to the toner container  30 , thereby transporting the toner received from the toner containing portion  31  in the first direction (direction indicated by the arrow D 0 . 
     The toner discharge port  33  is formed near the downstream end of the second region A 2  in the lower surface of the first transportation bottom wall  322 . The developer is discharged toward the developing device  20  through the toner discharge port  33 . The toner transported by the first transportation member  321  through the first region A 1  and the second region A 2  reaches the toner discharge port  33 . When the toner container  30  and the aforementioned developing device  20  are combined with each other, the toner replenishment port  25  formed in the developing housing  210  comes to a position below the toner discharge port  33  so as to oppose the toner discharge port  33 . The toner having been transported to the toner discharge port  33  is discharged outside of the toner container  30  through the toner discharge port  33  whenever necessary and moves into the developing housing  210  through the toner replenishment port  25 . In the situation where the toner container  30  is not combined with the developing device  20 , the toner discharge port  33  is covered with a shutter  331 , which is slidably positioned on the outside of the toner discharge port  33 , so as to prevent toner from leaking. 
     In an embodiment, the toner container  30  and the developing device  20  are adjacent to each other in the horizontal direction as illustrated in  FIG. 1 . Thus the area where the toner container  30  and the developing device  20  are superposed on each other in the up-down direction is decreased, thereby reducing the space occupied by the whole image forming apparatus  1  in the up and down direction. In the situation where the developing device  20  needs to be replenished with the toner, in order to supply the toner through the toner discharge port  33  without delay, the inside of the second region A 2  needs to be constantly filled with the toner. As has been previously described, the accumulation portion  26 A is formed by the agitating blade of the first transportation screw  23  in the developing housing  210  of the developing device  20 . Accordingly, the toner having been transported through the first transportation portion  32  of the toner container  30  cannot be discharged through the toner discharge port  33  in the situation where there is much toner accumulating in the accumulation portion  26 A of the developing housing  210 . In this situation, the toner is compressed, thereby forming a toner block. 
     In an embodiment, in order to prevent the toner from accumulating, or to prevent clogging due to the toner from occurring near the toner discharge port  33 , the second transportation portion  34  is provided. The second transportation portion  34  has a semi-cylindrical shape in sectional view similar to that of the first transportation portion  32 , an upper surface side of which opens and a lower surface side of which has a semi-circular shape. The second transportation portion  34  is positioned adjacent to and parallel to the second region A 2  of the first transportation portion  32 . The second transportation portion  34  has an inlet port (first communication portion  36 ), which is formed on the downstream side in the transportation direction (first direction) of the first transportation member  321  in the first transportation portion  32  at a position opposing the toner discharge port  33 . The second transportation portion  34  communicates with the first transportation portion  32  through the inlet port. 
     Out of the toner having been transported by the first transportation member  321  through the first transportation portion  32 , part of the toner not discharged from the toner discharge port  33  is blocked at a space formed by a side end wall  323  and an end wall  324  ( FIG. 5 ), which form an end portion of the first transportation portion  32 . This toner is caused to move into the second transportation portion  34  side through the first communication portion  36  by a transportation force applied thereto by the first transportation member  321 . 
     A second transportation member  341 , which transports toner in the second direction that is not discharged through the toner discharge port  33 , is rotatably positioned in the second transportation portion  34 . The second transportation member  341  has a shaft portion  341   a  and a blade portion  341   b , which has a screw shape and is located on the shaft portion  341   a . The shaft portion  341   a  and the blade portion  341   b  have diameters that are the same as those of the shaft portion  321   a  and the blade portion  321   b  of the first transportation member  321 , respectively. The blade portion  321   b  of the first transportation member  321  and the blade portion  341   b  of the second transportation member  341  are respectively formed on the shaft portion  321   a  and the shaft portion  341   a  such that the pitch of turns of the blade portion  321   b  in its transportation direction is the same as that of the blade portion  341   b  in its transportation direction. Also in an embodiment, the number of rotations per unit time of the first transportation member  321  is the same as that of the second transportation member  341 . The second transportation member  341  is rotated by a motor M 2  (second drive unit), thereby transporting the toner received through the first communication portion  36  in a direction (second direction) opposite to the first direction ( FIG. 5 ). 
     An end portion (outlet port) of the second transportation portion  34 , the end portion being on the downstream side in the transportation direction of the second transportation member  341 , is connected to the side wall portion  312  of the toner containing portion  31 , and the second transportation portion  34  and the toner containing portion  31  are communicate with each other through a second communication portion  37 . Thus, the toner received by the second transportation portion  34  through the first communication portion  36  is transported by the second transportation member  341 , and then drops again into the toner containing portion  31  to be mixed with the toner in the toner containing portion  31 . 
     As described above, in an embodiment, the excess toner, which is part of the toner that has been transported by the first transportation member  321  and then not discharged through the toner discharge port  33 , is blocked by the side end wall  323  and the end wall  324  and moves into the second transportation portion  34  through the first communication portion  36 . Thus, excessive compression of the toner does not occur, and accordingly, clogging due to the toner is unlikely to occur near the toner discharge port  33 . Furthermore, the excess toner having moved into the second transportation portion  34  is transported in the second direction by the second transportation member  341  and moves into the toner containing portion  31  again. The excess toner in the toner containing portion  31  is transported in a circulating manner to the toner discharge port  33  through agitation and transportation performed by the rotating paddle  35  and the first transportation member  321 . Thus, the excess toner can be reused and wastage of the toner can be suppressed. 
     In an embodiment, the first communication portion  36  is formed by cutting an upper end portion  322 A of the first transportation bottom wall  322 . Accordingly, a communication wall  361  having a specific height is formed under the first communication portion  36  ( FIG. 6 ). With this structure, the toner having been transported by the first transportation member  321  does not easily move toward the second transportation portion  34  side, thereby ensuring the density of the toner around the toner discharge port  33 . 
     Furthermore, in order to facilitate passage of the toner through the first communication portion  36 , the rotation direction of the first transportation member  321  is set such that, in sectional view, an outer edge of the blade portion  321   b  of the first transportation member  321  moves toward the first communication portion  36  along the first transportation bottom wall  322 . Likewise, the rotation direction of the second transportation member  341  is set such that, in sectional view, an outer edge of the blade portion  341   b  of the second transportation member  341  moves away from the first communication portion  36  along a second transportation bottom wall  342  (see arrows R 1  and R 2  in  FIGS. 4 and 5 ). 
     Next, the toner container  30  according to another embodiment of the present disclosure is described.  FIG. 7  is a plan view of the toner container  30  according to an embodiment with the top plate  301  removed. The difference between this embodiment and the previous embodiment is that, in this embodiment, the shape of a second transportation member  343  is different from that of the first transportation member  321 . Thus, this structure is described below and description of the other structures is omitted. 
     As is the situation with the first transportation member  321 , the second transportation member  343  has a shaft portion  343   a  and a blade portion  343   b . However, the pitch of turns of the blade portion  343   b  (spiral portion) is set to be larger than that of the blade portion  321   b  of the first transportation member  321 . That is, the amount of the developer to be fed per rotation of the blade portion  343   b  is larger. As a result, compared to the first transportation member  321 , the amount of the developer to be transported per unit time by the second transportation member  343  is larger. 
     With the above described structure, the excess toner overflowed near the toner discharge port  33  can be immediately transported in the second direction by the second transportation member  343  after the excess toner has been received by the second transportation portion  34  through the first communication portion  36 . Thus, the developer does not accumulate near the first communication portion  36 , and accordingly, clogging due to the developer near the toner discharge port  33  is further suppressed. 
     As described above, in this embodiment, the amount of the developer to be transported per unit time by the second transportation member  343  is set to be greater than that by the first transportation member  321 , thereby further suppressing clogging due to the developer near the toner discharge port  33 . Here, adjustment of the amount of the developer to be transported per unit time by the second transportation member  343  is not limited to a change in the pitch of the turns of the blade portion  343   b . The same effect can also be obtained by, for example in  FIG. 5 , increasing the number of rotations of the second transportation member  341  while the pitch of the turns of the blade portion  341   b  of the second transportation member  341  and the pitch of the turns of the blade portion  321   b  of the first transportation member  321  are kept unchanged. Specifically in this situation, the motor M 1  rotates the first transportation member  321  at a first number of rotations per unit time. The motor M 2  rotates the second transportation member  341  at a second number of rotations, which is greater than the first number of rotations by a specified number of rotations. 
     Next, the toner container  30  according to yet another embodiment of the present disclosure is described.  FIG. 8  is a plan view of the toner container  30  according to this embodiment having the top plate  301  removed. The difference between this embodiment and the previous embodiment is that, in this embodiment, the outlet port of the second transportation portion  34  communicates with the first transportation portion  32  instead of communicating with the toner containing portion  31 . Thus, this structure is described below and the description of the other structures is omitted. 
     The second transportation portion  34  is partitioned by a partition wall  381  downstream in the transportation direction of the second transportation member  341 . In addition, part of the upper end portion  322 A of the first transportation bottom wall  322 , by which the first transportation portion  32  and the second transportation portion  34  are separated from each other, is cut so as to form an opening (outlet port). The opening defines a third communication portion  38 , which communicates the second transportation portion  34  with the first transportation portion  32 . The toner having been transported in the second direction through the second transportation portion  34  is blocked by the partition wall  381  and receives a transportation force applied thereto by the second transportation member  341 , thereby moving into the first transportation portion  32  through the third communication portion  38 . Then, the toner receives a transportation force applied thereto by the first transportation member  321  of the first transportation portion  32 , thereby being transported again toward the toner discharge port  33 . 
     As described above, using the toner container  30  of this embodiment, excessive compression of the toner does not occur, and accordingly, clogging due to the toner does not occur near the toner discharge port  33 . Furthermore, the excess toner that moves into the second transportation portion  34  is transported in the second direction by the second transportation member  341 , and then moves into the first transportation portion  32  through the third communication portion  38 . As a result, excess toner can be reused through agitation and transportation performed by the first transportation member  321 . Thus, waste of the toner can be suppressed. 
     In the developing device  20  including the toner container  30  according to any of the aforementioned embodiments, clogging due to the toner is unlikely to occur in a toner replenishment path. This suppresses the occurrence of a situation in which a toner block moves into the developing device. This can also prevent the following situation from occurring: the developing housing  210  not being replenished with the toner because of clogging due to the toner, and accordingly, the amount of the toner in the developing housing  210  is decreased. 
     In particular, clogging due to toner easily occurs with a structure in which the accumulation portion  26 A is formed by the first transportation screw  23  at a position in the developing housing  210  opposite the toner replenishment port  25 , and the developing housing  210  is replenished with the toner through the toner discharge port  33  as the amount of the developer in the accumulation portion  26 A decreases. Even with such a structure, by using the toner container  30  according to any of the aforementioned embodiments, clogging due to the toner near the toner discharge port  33  and the toner replenishment port  25  can be suppressed. 
     Furthermore, with the toner container  30  according to any of the aforementioned embodiments and the image forming apparatus  1  including the developing device  20  equipped with the toner container  30  according to any of the aforementioned embodiments, the occurrence of image fading due to a decrease in the amount of the toner in the developing housing  210  is suppressed. Image flaws caused by a toner block entering the developing housing  210  can also be prevented from occurring. 
     Although the toner containers  30  according to the embodiments of the present disclosure have been described above, the present disclosure is not limited to these and the embodiment may be modified, for example, as follows. 
     (1) In the another embodiment, transportation performance of the second transportation member  341  in transporting the developer is set to be greater than that of the first transportation member  321 , thereby further suppressing clogging due to the developer near the toner discharge port  33 . In the aforementioned structures, the transportation performance of the second transportation member  341  in transporting the developer is adjusted by changing the pitch of the turns of the blade portion  341   b  or changing the number of rotations of the second transportation member  341 . However, the methods of adjusting transportation performance are not limited to these. The relationship between the degree of transportation performance between the first transportation member  321  and the second transportation member  341  may be adjusted by making the first transportation member  321  and the second transportation member  341  of different shapes or the like. 
     (2) In the aforementioned embodiments, the second transportation member  341  is located in the second transportation portion  34 . However, the structure is not limited to this. That is, the second transportation portion  34  may have a surface inclined from the first communication portion  36  toward the container bottom wall  311  of the toner containing portion  31 . In this situation, excess toner is pushed out through the first communication portion  36  to the second transportation portion  34  only by a transportation force applied thereto by the first transportation member  321 , and then slides on the inclined surface so as to be transported to the toner containing portion  31 . In addition to the above-described structure in which excess toner is returned to the toner containing portion  31 , excess toner may be discharged from the second transportation portion  34  to another transportation path or another containing portion outside the toner container  30 . 
     By way of example and not limitation, examples of the present disclosure will be given: 
     EXAMPLES 
     With examples of the toner container  30 , clogging due to toner near the toner discharge port  33  was evaluated. The results are as follows: 
     The examples and a comparative example were prepared under the specifications and evaluated under the conditions as follows. 
     Toner Container  30   
     Comparative Example 1 
     With the first transportation portion  32  (first transportation member  321 ) only (without the second transportation portion:  FIG. 9 ). 
     Example 1 
     With the first transportation portion  32  (first transportation member  321 ) and the second transportation portion  34  (second transportation member  341 ). The first transportation member  321  and the second transportation member  341  have the same structure. 
     Example 2 
     With the first transportation portion  32  (first transportation member  321 ) and the second transportation portion  34  (second transportation member  341 ). The second transportation member  341  is rotated at a number of rotations greater than that of the first transportation member  321 . 
     Example 3 
     With the first transportation portion  32  (first transportation member  321 ) and the second transportation portion  34  (second transportation member  343 ). The pitch of the turns of the blade portion  343   b  of the second transportation member  343  is greater than that of the first transportation member  321 . 
     Example 4 
     With the first transportation portion  32  (first transportation member  321 ) and the second transportation portion  34  (second transportation member  341 ). The second transportation member  341  is rotated at the number of rotations less than that of the first transportation member  321 . 
     Apparatus Conditions 
     In each of the examples and the comparative example, printing was performed under the same conditions with the image forming apparatus  1  using the developing device  20  that includes the toner container  30 . 
     Printing time (driving time of first transportation member  321 ): 120 minutes. 
     Printing condition: 1% coverage rate. 
     Average toner particle diameter: 6.8 μm. 
     Clogging due to the toner near the toner discharge port  33  was evaluated under the above-described conditions. Main conditions and results of the evaluation are listed in Table 1. Notations indicate the following results. 
     A: Clogging due to toner occurred. 
     B: Clogging due to toner occurred in some occasions. 
     C: Clogging due to toner did not occur. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 first transportation portion 
                 second transportation portion 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 rotation 
                 outer 
                   
                 rotation 
                 outer 
                   
                   
               
               
                   
                 per minute 
                 diameter 
                 pitch 
                 per minute 
                 diameter 
                 pitch 
               
               
                   
                 (rpm) 
                 (mm) 
                 (mm) 
                 (rpm) 
                 (mm) 
                 (mm) 
                 results 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Example 1 
                 15 
                 14 
                 10 
                 15 
                 14 
                 10 
                 A 
               
               
                 Example 2 
                 15 
                 14 
                 10 
                 30 
                 14 
                 10 
                 A 
               
               
                 Example 3 
                 15 
                 14 
                 10 
                 15 
                 14 
                 15 
                 A 
               
               
                 Example 4 
                 15 
                 14 
                 10 
                 7.5 
                 14 
                 10 
                 B 
               
               
                 Comparative 
                 15 
                 14 
                 10 
                 — 
                 — 
                 — 
                 C 
               
               
                 example 1 
               
               
                   
               
            
           
         
       
     
     As described in Table 1, with examples 1 to 4, in which the toner container  30  includes the second transportation portion  34  (second transportation member  341  or  343 ), desirable results with respect to clogging due to the toner near the toner discharge port  33  were obtained compared to the result with the comparative example 1, in which the toner container  30  does not include the second transportation portion  34 . Here, with the example 4, in which the number of rotations at which the second transportation member  341  is rotated was set to be lower than that at which the first transportation member  321  is rotated, the flow of the toner tended to lack smoothness to a small degree near the toner discharge port  33  compared to the other examples. However, since the second transportation portion  34  was provided, the excess toner near the toner discharge port  33  moved toward the second transportation portion  34  side, and accordingly, clogging due to the toner as occurred with the comparative example did not occur. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.