Patent Publication Number: US-8995884-B2

Title: Developing apparatus and image forming apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2012-100229, filed on Apr. 25, 2012, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention: 
     The present invention relates to a developing apparatus and an image forming apparatus including a developing unit and a developer accommodating unit which is provided under or below the developing unit and which accommodates a developer. 
     2. Description of the Related Art: 
     Conventionally, a developing apparatus is known, including a developing unit provided with a developing roller, and a developer accommodating unit provided under or below the developing unit to accommodate a developer. In the developing apparatus as described above, those provided between the developing unit and the developer accommodating unit which are aligned vertically are a partition wall which partitions the developing unit and the developer accommodating unit, and a supply port which makes communication between the developing unit which uses a part of the partition wall as a bottom thereof and the developer accommodating unit. 
     In the developing apparatus, the developer, which is accommodated in the developer accommodating unit, is supplied to the developing unit via the supply port by means of a transport member provided in the developer accommodating unit. 
     SUMMARY OF THE INVENTION 
     In the meantime, the electrification or charging of the developer is uneven, and the developer, which has a large electric charge amount or electrification amount, is preferentially and selectively used for the development. Therefore, the developer, which has a small electric charge amount and which is not used for the development, remains in the developing unit. However, in the case of the technique as described above, the developer, which is contained in the developing unit, is not returned to the developer accommodating unit. Therefore, the developer, which has the small electric charge amount, is consequently accumulated in the developing unit. 
     In view of the above, an object of the present teaching is to provide a developing apparatus which makes it possible to return a developer contained in a developing unit to a developer accommodating unit. 
     According to a first aspect of the present teaching, there is provided a developing apparatus configured to perform development by using a developer, the developing apparatus including: 
     a developing unit including a developing roller; 
     a developer accommodating unit provided under or below the developing unit and configured to accommodate the developer; 
     a partition wall configured to construct at least a bottom of the developing unit and partitioning the developing unit and the developer accommodating unit; 
     a supply port configured to make communication between the developing unit and the developer accommodating unit and configured so that the developer accommodated in the developer accommodating unit is permitted to move to the developing unit; 
     a transport member provided in the developer accommodating unit and configured so that the developer accommodated in the developer accommodating unit is supplied to the developing unit via the supply port in accordance with rotation; 
     a return port formed at a portion corresponding to the bottom of the developing unit constructed by the partition wall and configured so that the developer contained in the developing unit is permitted to fall into the developer accommodating unit; 
     an opening/closing member provided for the developing unit and configured to be movable between an open position for opening the return port and a closed position for closing the return port; and 
     a driving mechanism configured so that the opening/closing member is moved to the closed position and the open position. 
     According to the developing apparatus constructed as described above, the opening/closing member is opened/closed, and thus the developer contained in the developing unit can be occasionally returned to the developer accommodating unit. Therefore, it is possible to reduce the accumulation of the developer having a small amount of electric charge in the developing unit. The developer, which is returned to the developer accommodating unit, is agitated in accordance with the rotation of the transport member. Accordingly, it is possible to obtain a sufficient amount of electric charge. Further, the opening/closing member is moved, and thus the developer contained in the developing unit is loosened. Therefore, it is possible to reduce the solidification of the developer at any part. 
     According to a second aspect of the present teaching, there is provided an image forming apparatus configured to form an image on a medium, including: 
     the developing apparatus in accordance with the first aspect of the present teaching; 
     a photosensitive member arranged opposingly to the developing roller; 
     an exposure apparatus arranged opposingly to the photosensitive member at a position different from that of the developing roller and configured to expose the photosensitive member; 
     an endless belt arranged over or above each of the photosensitive member; 
     a primary transfer roller arranged opposingly to each of the photosensitive member between each of the photosensitive member and the primary transfer roller with the endless belt intervening therebetween; and 
     a secondary transfer roller arranged on one end side of the endless belt. 
     According to a third aspect of the present teaching, there is provided a developing apparatus including:
         a developing roller;   a transport member;   a casing comprising a partition wall which partitions a first chamber in which the developing roller is disposed and a second chamber configured to accommodate developer and disposed below the first chamber, the partition wall having:
           a supply port for making communication between the first chamber and the second chamber, the transport member being disposed in the second chamber and configured to supply the developer accommodated in the second chamber to the first chamber via the supply port; and   a return port for permitting the developer contained in the first chamber to fall into the second chamber; and   an moving member configured to be move between an open position for opening the return port and a closed position for closing the return port.   
               

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic arrangement of a color printer provided with a developing cartridge according to one embodiment of the present teaching. 
         FIG. 2  shows a developing cartridge. 
         FIG. 3A  shows a perspective view illustrating an opening/closing member, and  FIG. 3B  shows an enlarged view illustrating a right end portion of the opening/closing member. 
         FIG. 4  shows a driving mechanism. 
         FIGS. 5A and 5B  show the developing cartridge, wherein  FIG. 5A  shows a state in which the opening/closing member closes a return port, and  FIG. 5B  shows a state in which the opening/closing member opens the return port. 
         FIGS. 6A and 6B  show a developing cartridge according to a modified embodiment, wherein  FIG. 6A  shows a state in which an opening/closing member closes a return port, and  FIG. 6B  shows a state in which the opening/closing member opens the return port. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, an embodiment of the present invention will be explained in detail appropriately with reference to the drawings. In the following description, the overall arrangement of a color printer  1  including a developing cartridge  100  will be firstly explained as an example of the developing apparatus, and then details of the feature of the present invention will be explained. 
     In the following description, the directions will be explained by using the directions as provided on the basis of a user upon the use of the color printer  1 . That is, as viewed in  FIG. 1 , the left side, which is provided while confronting the paper surface, is defined as “front side (forward side)”, and the right side, which is provided while confronting the paper surface, is defined as “rear side (rearward side)”. Further, the forward side, which is provided while confronting the paper surface, is defined as “right side”, and the backward side, which is provided while confronting the paper surface, is defined as “left side”. Further, the upward-downward direction, which is provided while confronting the paper surface, is defined as “up-down direction”. 
     &lt;Overall Arrangement of Color Printer&gt; 
     As shown in  FIG. 1 , the color printer  1  mainly includes a main body  2 , a paper feed unit  3  configured to supply the printing paper P, an image forming unit  4  configured to form an image on the supplied printing paper P, and a paper discharge roller  9  configured to discharge the printing paper P on which the image has been formed. 
     A discharge tray  21 , on which the printing paper P discharged from the main body  2  is placed, is provided at an upper portion of the main body  2 . 
     The paper feed unit  3  includes a paper feed tray  31  provided at a lower portion in the main body  2  and installed to the main body  2  removably, and a paper feed mechanism  32  configured to transport the printing paper P fed from the paper feed tray  31  to the transfer position of the image forming unit  4  (between an intermediate transfer belt  63  and a secondary transfer roller  65 ). The printing paper P, which is accommodated in the paper feed tray  31 , is separated one by one by the paper feed mechanism  32 , and the printing paper P is transported to the transfer position. 
     The image forming unit  4  is principally composed of four photosensitive drums  41 , unillustrated electrifiers (chargers), four developing cartridges  100 , four LED units  50 , a transfer unit  60 , and a fixing unit  70 . 
     The four photosensitive drums  41  are aligned in the front-rear direction. Each of the photosensitive drums  41  is arranged so that the photosensitive drum  41  is opposed to the intermediate transfer belt  63  under or below the intermediate transfer belt  63  as described later on. An upper portion of each of the photosensitive drums  41  is brought in contact with a primary transfer roller  64  with the intermediate transfer belt  63  intervening therebetween. 
     As shown in  FIG. 2 , the developing cartridge  100  principally includes a developing roller  42 , a supply roller  43  as an example of the supply member, a layer thickness regulating blade  44 , and a toner transport member  45  as an example of the transport member. With reference to  FIG. 1 , each of the four developing cartridges  100  is arranged forwardly with respect to each of the four photosensitive drums  41 , which is provided corresponding to each of the four photosensitive drums  41 . Detailed arrangement of the developing cartridge  100  will be described later on. 
     The four LED units  50  are provided corresponding to the plurality of photosensitive drums  41  respectively. Each of the LED units  50  is arranged opposingly to the photosensitive drum  41  under or below the corresponding photosensitive drum  41 . The LED unit  50  is constructed such that the light-emitting element of the LED unit  50  is turned ON/OFF on the basis of the image data, and thus the surface of the photosensitive drum  41  is exposed. 
     The transfer unit  60  is provided between the four photosensitive drums  41  and the discharge tray  21 , and the transfer unit  60  includes a driving roller  61 , a driven roller  62 , the intermediate transfer belt  63  having an endless shape provided in a stretched form between the driving roller  61  and the driven roller  62 , four primary transfer rollers  64  arranged opposingly to the photosensitive drums  41  with the intermediate transfer belt  63  intervening therebetween, a secondary transfer roller  65  arranged opposingly to the driving roller  61  with the intermediate transfer belt  63  intervening therebetween, and a cleaning unit  66  arranged over or above the intermediate transfer belt  63  on the front side and which removes the toner T (developer) disposed on the intermediate transfer belt  63 . 
     The fixing unit  70  is provided over or above the intermediate transfer belt  63  on the rear side, and the fixing unit  70  principally includes a heating roller  71 , and a pressing roller  72  arranged opposingly to the heating roller  71  and configured to press the heating roller  71 . 
     In the image forming unit  4  constructed as described above, the surfaces of the respective photosensitive drums  41  are uniformly charged by the chargers (not shown), and then the surfaces are exposed by means of the LED units  50 . Accordingly, the electric potentials are lowered at the exposed portions of the surfaces of the photosensitive drums  41 , and electrostatic latent images, which are based on the image data, are formed on the respective photosensitive drums  41 . The toners T, which are contained in the developing cartridges  100 , are agitated by the toner transport members  45 , and thus the toners T are frictionally charged. After that, the toners T are supplied to the developing rollers  42  by the aid of the supply rollers  43 . 
     The toners T carried on the developing rollers  42  are supplied from the developing rollers  42  to the electrostatic latent images on the photosensitive drums  41 . Accordingly, the electrostatic latent images are converted into visual images, and toner images are formed on the photosensitive drums  41 . The toner images, which are formed on the respective photosensitive drums  41 , are successively overlaid and transferred onto the intermediate transfer belt  63  in accordance with the action of the respective primary transfer rollers  64  to each of which the transfer bias is applied. 
     The toner images, which are transferred to the intermediate transfer belt  63 , are transferred onto the printing paper P in accordance with the action of the secondary transfer roller  65  to which the transfer bias is applied, when the printing paper P, which is supplied to the image forming unit  4 , passes through the space between the intermediate transfer belt  63  and the secondary transfer roller  65 . The printing paper P, to which the toner images are transferred, is transported to the fixing unit  70 . The printing paper P passes through the space between the heating roller  71  and the pressing roller  72 , and thus the toner images are thermally fixed. The printing paper P, on which the toner images are thermally fixed, is discharged to the outside of the main body  2  by means of the paper discharge roller  9 , and the printing paper P is accumulated in the discharge tray  21 . 
     &lt;Detailed Arrangement of Developing Cartridge&gt; 
     Next, an explanation will be made about the detailed arrangement of the developing cartridge  100  as the feature of the present teaching. 
     As shown in  FIG. 2 , the developing cartridge  100  includes a casing  101  provided with a developing unit  110  and a toner accommodating unit  120  arranged under or below the developing unit  110  and provided as an example of the developer accommodating unit for accommodating the toner T. 
     The developing cartridge  100  principally includes the developing roller  42 , the supply roller  43 , the layer thickness regulating blade  44 , and an opening/closing member  200  arranged in the developing unit  110 , the toner transport member  45  arranged in the toner accommodating unit  120 , and a gear mechanism  130  (see  FIG. 4 ) arranged on the right side surface of the casing  101 . 
     The casing  101  of the developing cartridge  100  includes a partition wall  103  extending forwardly from a back wall  102 . Accordingly, the interior of the casing  101  is partitioned, and the developing unit  110  and the toner accommodating unit  120  are formed. The partition wall  103  constitutes the bottom of the developing unit  110 . 
     An opening is formed at a back portion of the developing unit  110 . The developing roller  42  is arranged so that the developing roller  42  is exposed to the outside via the opening. 
     The supply roller  43  is arranged obliquely downwardly in front of the developing roller  42  so that the supply roller  43  is brought in contact with the developing roller  42  over or above the partition wall  103 . 
     In this arrangement, the partition wall  103  has a bent shape so that the partition wall  103  is arranged downwardly from the supply roller  43  and obliquely downwardly in front of the supply roller  43 . The partition wall  103  is formed to have a substantially L-shaped form. Specifically, the partition wall  103  passes under or below the supply roller  43  from the back wall  102  to extend obliquely upwardly in the forward direction, and then the partition wall  103  further extends obliquely upwardly in the upward direction while being inclined toward the supply roller  43  so that the partition wall  103  extends to a position disposed forwardly from the supply roller  43 . Accordingly, the toner T is stored on the lower side of the supply roller  43 . A supply port  104 , which makes communication between the developing unit  110  and the toner accommodating unit  120 , is formed between the forward end of the partition wall  103  and a wall  107 A of the casing  101  arranged on an extension line of the forward end of the partition wall  103 . The supply port  104  permits the toner T accommodated in the toner accommodating unit  120  to move to the developing unit  110 . 
     Further, a return port  105 , which penetrates in the upward-downward direction, is formed at a portion of the partition wall  103  corresponding to the bottom of the developing unit  110 , i.e., the portion of the partition wall  103  included in the portion extending from the back wall  102  to the position disposed under or below the supply roller  43  and arranged under or below the developing roller  42 . The return port  105  is constructed so that the toner T contained in the developing unit  110  is permitted to fall into the toner accommodating unit  120 . 
     The layer thickness regulating blade  44  is provided so that the layer thickness regulating blade  44  is brought in contact with the outer circumferential surface of the developing roller  42  at the downward position. Specifically, the proximal end portion of the layer thickness regulating blade  44  is supported by the back wall  102  of the casing  101 . The forward end portion of the layer thickness regulating blade  44  extends to the position disposed under the developing roller  42 , which is brought in contact with the developing roller  42 . The contact portion of the layer thickness regulating blade  44 , which is brought in contact with the developing roller  42 , is arranged over or above the return port  105 . Accordingly, the toner T, which is scraped off by the layer thickness regulating blade  44 , falls to the positions around the return port  105 . 
     The opening/closing member  200  is the member configured to open/close the return port  105 . The opening/closing member  200  is constructed to be movable between the open position (position shown in  FIG. 5B ) at which the return port  105  is open and the closed position (position shown in  FIG. 5A ) at which the return port  105  is closed. As shown in  FIGS. 2 and 3A , the opening/closing member  200  principally includes a main body portion  210 , a support portion  220 , and a shaft portion  230 . 
     The main body portion  210  is the portion of the opening/closing member  200  arranged on the return port  105 . The main body portion  210  is formed to have a substantially triangular shape as viewed in a side view. The main body portion  210  has a first surface  211  which is opposed to the return port  105  and which is formed to have substantially the same size as that of the return port  105 , a second surface  212  which is opposed to the supply roller  43 , and a third surface  213  which is opposed to the back wall  102  of the casing  101 . 
     The support portion  220  is arranged at the forward position with respect to the main body portion  210 . The support portion  220  supports a front lower portion of the main body portion  210  (portion protruding forwardly from a lower portion of the second surface  212 ) so that the main body portion  210  is swingable with respect to the support portion  220 . The support portion  220  is arranged so that the support portion  220  is interposed between stoppers  106  provided on the left and right walls of the casing  101  and the partition wall  103  (in particular a seal member  150  provided on the partition wall  103  as described later on) in the up-down direction. Accordingly, the movement of the support portion  220  in the up-down direction is regulated, and the movement of the support portion  220  in the front-rear direction is permitted. 
     The main body portion  210  and the support portion  220  form the wall portion arranged between the supply roller  43  and the return port  105 . A storage unit  111 , which is substantially U-shaped as viewed in a sectional view and which is provided to store the toner T, is formed by the second surface  212  of the main body portion  210 , the upper surface of the support portion  220 , and the surface of the partition wall  103  disposed on the side of the developing unit  110 . As for the main body portion  210 , the toner T can be also stored between the third surface  213  of the main body portion  210  and the surface of the back wall  102  disposed on the front side. This space principally stores the toner T which overflows from the storage unit  111  and the toner T which is scraped off by the layer thickness regulating blade  44 . 
     The shaft portion  230  is the shaft inserted into the hole that is formed at a lower portion of the main body portion  210  disposed on the back side to penetrate in the left-right direction. As shown in  FIG. 3B , the shaft portion  230  is formed to extend in the left-right direction. Each of the both ends portions in the left-right direction has a first portion  231  which protrudes outwardly from the hole of the main body portion  210 , a second portion  232  which extends in an oblique direction intersecting the left-right direction from each of the both ends of the first portions  231 , and a third portion  233  which extends outwardly in the left-right direction from the end portion of the second portion  232  disposed on the side opposite to the first portion  231 . The portions of the shaft portion  230 , which are exposed from the main body portion  210 , are bent in substantially S-shaped forms. In other words, the first portion  231  is arranged at the position which is deviated in the radial direction of the third portion  233  with respect to the third portion  233 . 
     The third portion  233  of the shaft portion  230  disposed at the left end is fixed to the center of rotation of an opening/closing member driving gear  134  of a gear mechanism  130  as described later on. A driving mechanism  140 , which moves the opening/closing member  200  to the closed position and the open position, is constructed by the shaft portion  230  and the opening/closing member driving gear  134 . 
     Specifically, when the first portion  231  of the shaft portion  230  is positioned at the lowermost position with respect to the third portion  233 , the opening/closing member  200  is arranged at the closed position at which the main body portion  210  approaches the return port  105  most closely. On the other hand, when the first portion  231  of the shaft portion  230  is positioned at the uppermost position with respect to the third portion  233 , then the opening/closing member  200  is arranged upwardly as compared with when the main body portion  210  is arranged at the closed position, and the opening/closing member  200  is arranged at the open position separated upwardly farthest from the return port  105 . The first portion  231  circles about the center of the third portion  233  in accordance with the rotation of the opening/closing member driving gear  134 , and thus the opening/closing member  200  is moved between the closed position and the open position. A specified operation of the opening/closing member  200  will be described later on. 
     As shown in  FIG. 2 , the seal member  150 , which is formed of, for example, sponge, is provided between the edge of the return port  105  and the opening/closing member  200 . The seal member  150  prevents the toner T contained in the developing unit  110  from falling into the toner accommodating unit  120  through any space between the edge of the return port  105  and the opening/closing member  200  when the opening/closing member  200  is positioned at the closed position. 
     The toner accommodating unit  120  is formed to have a hollow and substantially columnar form. The toner accommodating unit  120  is communicated with the developing unit  110  via the supply port  104  disposed at the upper position. The toner transport member  45  is provided in the toner accommodating unit  120 . 
     The toner transport member  45  is principally includes a rotational shaft  45 A rotatably supported by the casing  101 , and a film member  45 B having flexibility and configured to extend outwardly in the radial direction from the rotational shaft  45 A. The toner transport member  45  has the film member  45 B which is rotatable while making sliding contact with the inner surface of the casing  101 . Accordingly, the toner T, which is accommodated in the toner accommodating unit  120 , is agitated by rotating the toner transport member  45 . 
     The toner accommodating unit  120  has a recess  108  which is recessed forwardly and which is formed at an upper portion of a front wall  107 . The recess  108  is provided to range from a portion disposed below the partition wall  103  to an upper portion of the supply port  104  in the up-down direction. Accordingly, when the film member  45 B, which is rotated while being flexibly bent and making sliding contact with the front wall  107 , arrives at the recess  108 , the forward end is released to spring up. Therefore, the toner T, which has been placed on the film member  45 B, is allowed to fly toward the supply port  104 , and the toner T is transported to the developing unit  110 . 
     As shown in  FIG. 4 , the gear mechanism  130  is constructed to include an input gear  131  to which the driving force is transmitted from an unillustrated motor provided on the side of the main body  2 , a developing roller driving gear  132  and a supply roller driving gear  133  which are directly meshed with the input gear  131 , an opening/closing member driving gear  134  which is meshed with the supply roller driving gear  133 , and a toner transport member driving gear  136  which is meshed with the opening/closing member driving gear  134  with an intermediate gear  135  intervening therebetween. In this arrangement, the developing roller driving gear  132 , the supply roller driving gear  133 , and the toner transport member driving gear  136  are provided integrally at the end portions of the respective shafts of the developing roller  43 , the supply roller  43 , and the toner transport member  45  respectively. 
     As described above, the opening/closing member driving gear  134  is provided integrally at the end portion of the shaft portion  230  of the opening/closing member  200  (see  FIG. 3B ). Further, the opening/closing member driving gear  134  for rotating the opening/closing member  200  and the toner transport member driving gear  136  for rotating the toner transport member are connected as described above, and thus the opening/closing operation of the opening/closing member  200  can be interconnected with the rotational operation of the toner transport member  45 . 
     Next, the operation of the opening/closing member  200  will be explained. When the driving force is transmitted from the motor to the input gear  131 , the developing roller driving gear  132 , the supply roller driving gear  133 , the opening/closing member driving gear  134 , and the toner transport member driving gear  136  begin to rotate. 
     As for the opening/closing member  200 , as described above, when the first portion  231  of the shaft portion  230  is positioned at the lowermost position with respect to the third portion  233 , the opening/closing member  200  is positioned at the closed position for closing the return port  105  as shown in  FIG. 5A . When the opening/closing member driving gear  134  is rotated clockwise as shown in  FIG. 4 , the first portion  231  of the shaft portion  230  begin to move obliquely upwardly in the forward direction. In accordance therewith, the support portion  220  is moved forwardly, while the back end of the main body portion  210  is allowed to swing upwardly. Accordingly, the opening/closing member  200  opens the return port  105 . After the first portion  231  of the shaft portion  230  is rotated by about 90 degrees from the position of being arranged at the closed position, the movement begins obliquely upwardly in the backward direction. In accordance therewith, the support portion  220  is moved backwardly, while the back end of the main body portion  210  is allowed to swing further upwardly. 
     When the first portion  231  of the shaft portion  230  is positioned at the uppermost position (when it is rotated by about 180 degrees from the position of being arranged at the closed position), as shown in  FIG. 5B , the opening/closing member  200  is positioned at the open position at which the main body portion  210  is arranged most upwardly. 
     When the opening/closing member driving gear  134  is further rotated, the first portion  231  of the shaft portion  230  begins to move obliquely downwardly in the backward direction. In accordance therewith, the support portion  220  is moved backwardly, while the back end of the main body portion  210  is allowed to swing downwardly. After the first portion  231  of the shaft portion  230  is rotated by about 90 degrees from the position of being arranged at the open position, the movement begins obliquely downwardly in the forward direction. In accordance therewith, the support portion  220  is moved forwardly, while the lower end of the main body portion  210  is allowed to swing further downwardly, and the opening/closing member  200  is moved to the closed position. 
     According to the foregoing description, it is possible to obtain the following function and effect in this embodiment. The opening/closing member  200  is moved to the open position and the closed position to open/close the return port  105 . Accordingly, the toner T, which has been stored between the third surface  213  and the back wall  102  in the developing unit  110 , which has the small amount of electric charge, and which is not used for the development, for example, by being scraped off by the layer thickness regulating blade  44 , can be occasionally returned to the toner accommodating unit  120 . Accordingly, it is possible to reduce the accumulation of the toner T having the small electric charge amount in the developing unit  110 . Further, the toner T, which is returned to the toner accommodating unit  120 , is agitated by rotating the toner transport member  45 . Thus, the toner T can be sufficiently charged even when the returned toner T has the small electric charge amount. Further, the toner T, which is contained in the developing unit  110  (especially in the storage unit  111  around the supply roller  43 ), is loosened by allowing the main body portion  210  of the opening/closing member  200  to swing. Therefore, it is possible to reduce the solidification of the toner T at any part. 
     The opening/closing member  200  is provided between the supply roller  43  and the return port  105 , and the storage unit  111  is formed by the second surface  212  and the surface of the partition wall  103  disposed on the side of the supply roller  43 . Accordingly, even when the opening/closing member  200  is moved to the open position, the toner T, which is stored in the storage unit  111 , does not fall from the return port  105 . Accordingly, it is possible to suppress any sudden decrease in the toner T around the supply roller  43  when the opening/closing member  200  opens the return port  105 . 
     The driving mechanism  140 , which is configured to move the opening/closing member  200  to the open position and the closed position, is operated interconnectedly with the rotational operation of the toner transport member  45 . Therefore, the opening/closing member  200  is moved periodically, and the toner T contained in the developing unit  110  is returned to the toner accommodating unit  120 . Further, the toner T contained in the developing unit  110  is loosened. Accordingly, the fluidity of the toner T is improved in the developing cartridge  100  and in the developing unit  110 . 
     Further, the seal member  150  is provided between the edge of the return port  105  and the opening/closing member  200 . Therefore, it is possible to reduce the leakage of the toner T from any gap between the return port  105  and the opening/closing member  200  positioned at the closed position. Accordingly, it is possible to correctly manage the amount of the toner T to be returned from the developing unit  110  to the toner accommodating unit  120 . 
     The embodiment of the present teaching has been explained above. However, the present teaching is not limited to the embodiment described above. The specified construction can be appropriately changed within a scope without deviating from the gist or essential characteristics of the present teaching. 
     In the embodiment described above, the opening/closing member  200  has the main body portion  210  which is swingable in the up-down direction, and the support portion  220  which is movable in the front-rear direction. However, the present teaching is not limited thereto. For example, the main body of the opening/closing member  200  may be formed by one part. 
     Specifically, as shown in  FIG. 6A , an opening/closing member  300  includes a main body portion  310  configured to be substantially triangular as viewed in a side view, and a shaft portion  230  which is the same as or equivalent to that of the embodiment described above. The main body portion  310  has holes  320  disposed at front end portions of left and right side surfaces. Support shafts  109 , which are formed on the side walls of the casing  101 , are loosely fitted to the holes. 
     The opening/closing member  300  constructed as described above is movable in the up-down direction and in the left-right direction. Therefore, the opening/closing member  300  can be moved in conformity with the operation of the first portion  231  of the shaft portion  230 . In other words, when the shaft portion  230  is rotated from the closed position at which the opening/closing member  300  closes the return port  105  as shown in  FIG. 6A , and the first portion  231  is moved upwardly, then the opening/closing member  300  is moved to the open position at which the opening/closing member  300  opens the return port  105  as shown in  FIG. 6B .