Patent Publication Number: US-9411265-B2

Title: Developer conveying mechanism, image forming apparatus

Description:
INCORPORATION BY REFERENCE 
     This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2014-173273 filed on Aug. 27, 2014, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a developer conveying mechanism and an image forming apparatus including the same. 
     In general, an electrophotographic image forming apparatus is provided with a developer conveying mechanism that conveys powdery developer by a conveyance member such as a screw-type conveyance member or a coil-type conveyance member. The developer conveying mechanism conveys developer that is to be supplied to a developing portion or developer (waste developer) that has been collected by a cleaning portion which removes residual developer from the surface of an image carrier. 
     In addition, the developer conveying mechanism may include a first lateral conveyance path, a longitudinal passage, and a second lateral conveyance path. The first lateral conveyance path is a passage that is formed to extend along a lateral direction, and includes, inside thereof, the conveyance member that conveys the developer in the lateral direction. An outlet from which the developer falls down is formed in the first lateral conveyance path. The longitudinal passage extends in a longitudinal direction, and the developer that has fallen down from the outlet passes through the longitudinal passage. The second lateral conveyance path is a passage that is formed to extend along a lateral direction, and includes, inside thereof, the conveyance member that further conveys, in the lateral direction, the developer that has passed through the longitudinal passage. 
     SUMMARY 
     A developer conveying mechanism according to an aspect of the present disclosure includes a first lateral conveyance path forming portion, a longitudinal passage forming portion, and a second lateral conveyance path forming portion. The first lateral conveyance path forming portion includes, inside thereof, a first conveyance member that is configured to convey the developer in the first lateral direction. The first lateral conveyance path forming portion forms a first lateral conveyance path for conveying developer in a first lateral direction. A lower opening is formed on the first lateral conveyance path forming portion as an outlet from which the developer falls down. The longitudinal passage forming portion forms a longitudinal passage of the developer that has fallen down from the lower opening. The second lateral conveyance path forming portion includes, inside thereof, a second conveyance member that is configured to convey, in the second lateral direction, the developer that has passed through the longitudinal passage. The second lateral conveyance path forming portion forms a second lateral conveyance path for conveying the developer in a second lateral direction. In the present developer conveying mechanism, the lower opening of the first lateral conveyance path forming portion is formed such that width thereof expands from an upstream side to a downstream side in the first lateral direction. 
     A developer conveying mechanism according to another aspect of the present disclosure includes the first lateral conveyance path forming portion, the longitudinal passage forming portion, and the second lateral conveyance path forming portion. In the present developer conveying mechanism, the lower opening of the first lateral conveyance path forming portion is formed in a range that extends, when viewed from above, from a predetermined position toward a downstream side in the first lateral direction. The predetermined position is a position that is, when viewed from above, closer to a center line of the second lateral conveyance path that extends along the second lateral direction, than an edge of an inlet of the longitudinal passage, the edge being in an upstream side in the first lateral direction. 
     An image forming apparatus according to a further aspect of the present disclosure includes the developer conveying mechanism according to the aspect of the present disclosure or the developer conveying mechanism according to the other aspect of the present disclosure. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description with reference where appropriate to the accompanying drawings. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a configuration diagram of an image forming apparatus according to the first embodiment of the present disclosure. 
         FIG. 2  is an approximate cross-sectional view of a primary cleaning portion provided in the image forming apparatus according to the first embodiment of the present disclosure. 
         FIG. 3  is a partially cut plan view of a developer conveying mechanism provided in the image forming apparatus according to the first embodiment of the present disclosure. 
         FIG. 4  is a vertical cross-sectional view of the developer conveying mechanism provided in the image forming apparatus according to the first embodiment of the present disclosure. 
         FIG. 5  is a cross-sectional plan view of a first lateral conveyance path forming portion of the developer conveying mechanism provided in the image forming apparatus according to the first embodiment of the present disclosure. 
         FIG. 6  is a vertical cross-sectional view of the developer conveying mechanism that is conveying the developer in the image forming apparatus according to the first embodiment of the present disclosure. 
         FIG. 7  is a cross-sectional plan view of the first lateral conveyance path forming portion of the developer conveying mechanism provided in the image forming apparatus according to the second embodiment of the present disclosure. 
         FIG. 8  is a cross-sectional plan view of the first lateral conveyance path forming portion of the developer conveying mechanism provided in the image forming apparatus according to the third embodiment of the present disclosure. 
         FIG. 9  is a vertical cross-sectional view of the developer conveying mechanism provided in the image forming apparatus according to the fourth embodiment of the present disclosure. 
         FIG. 10  is a vertical cross-sectional view of the developer conveying mechanism provided in the image forming apparatus according to the fifth embodiment of the present disclosure. 
         FIG. 11  is a cross-sectional plan view of the first lateral conveyance path forming portion of the developer conveying mechanism provided in the image forming apparatus according to the fifth embodiment of the present disclosure. 
         FIG. 12  is a vertical cross-sectional view of the developer conveying mechanism that is conveying the developer in the image forming apparatus according to the fifth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following describes embodiments of the present disclosure with reference to the attached drawings. It should be noted that the following description is examples of specific embodiments of the present disclosure and should not limit the technical scope of the present disclosure. 
     First Embodiment 
     First, a description is given of an image forming apparatus  10  according to the first embodiment of the present disclosure with reference to  FIGS. 1-6 . The image forming apparatus  10  is an electrophotographic image forming apparatus. 
     [Configuration of Image Forming Apparatus  10 ] 
     In the example shown in  FIG. 1 , the image forming apparatus  10  is a tandem image forming apparatus and is a color printer. Other examples of the image forming apparatus  10  include a copier, a facsimile apparatus, and a multifunction peripheral having an image forming function. 
     The image forming apparatus  10  includes, in a housing  100 , a sheet supply portion  2 , a sheet conveying portion  3 , a plurality of developer supply portions  40 , a plurality of image forming portions  4 , an optical scanning portion  51 , a secondary transfer portion  52 , a fixing portion  53 , and an intermediate transfer belt  48 . 
     The sheet supply portion  2  includes a sheet cassette  21  and a sheet feed portion  22 , wherein the sheet cassette  21  can be attached to and detached from the housing  100 , and the sheet feed portion  22  feeds a recording sheet  9  stored in the sheet cassette  21  to the image forming portion  4 . It is noted that the recording sheet  9  is a sheet-like image formation medium such as a sheet of paper, a sheet of coated paper, a postcard, an envelope, or an OHP sheet. 
     The sheet feed portion  22  picks up the recording sheets  9  one by one from within the sheet cassette  21 , and feeds the recording sheets  9  to a sheet conveyance path  300  of the sheet conveying portion  3 . 
     The sheet conveying portion  3  includes a registration roller  31 , a conveyance roller  32 , and a discharge roller  33 . The registration roller  31  and the conveyance roller  32  convey the recording sheet  9  in the sheet conveyance path  300 . After an image is formed on the recording sheet  9  in the middle of the sheet conveyance path  300 , the discharge roller  33  discharges the recording sheet  9  from a discharge port of the sheet conveyance path  300  onto a discharge tray  101 . 
     The developer supply portions  40  and the image forming portions  4  are provided respectively in correspondence with the colors of the developer (toner). The colors of the developer are yellow, cyan, magenta and black. The developers of the respective colors are supplied from the developer supply portions  40  to the image forming portions  4 . The developer supply portions  40  are, for example, attached to the housing  100  in a detachable manner. 
     Each of the developer supply portions  40  delivers the developer from a supply container storing the developer, to a corresponding developing portion  43  that is described below. The developer may be supplied directly to the developing portions  43  from the developer supply portions  40 . Alternatively, the developer may be supplied to the developing portions  43  via an intermediate conveyance portion (not shown) from the developer supply portions  40 . 
     The image forming portions  4  are disposed along the endless intermediate transfer belt  48  that rotates. The image forming portions  4  form a color toner image by overlaying images of different colors (toner images) on the surface of the rotating intermediate transfer belt  48 . 
     Each image forming portion  4  includes a drum-like photoconductor  41 , a charging portion  42 , a developing portion  43 , a primary transfer portion  45 , and a primary cleaning portion  47 . The photoconductor  41  is an example of the image carrier. 
     The intermediate transfer belt  48  is a belt-like member formed in the shape of an endless loop. The intermediate transfer belt  48  is rotated in the state where it is suspended between two rollers. In each image forming portion  4 , the photoconductor  41  is rotated at a peripheral speed that corresponds to a peripheral speed (moving speed) of the intermediate transfer belt  48 , and the charging portion  42  uniformly charges the surface of the photoconductor  41 . 
     Furthermore, the optical scanning portion  51  including a laser light source (not shown), a polygon mirror  511 , and an optical deflection instrument  512  scans laser light. With this operation, the optical scanning portion  51  writes an electrostatic latent image on the charged surface of the photoconductor  41 . 
     The developing portion  43  includes a developing roller  431  that supplies developer to the photoconductor  41 . The developing portion  43  develops the electrostatic latent image by supplying the developer to the photoconductor  41  by the developing roller  431 . It is noted that the developing roller  431  may also be called a developing sleeve. In addition, the optical scanning portion  51  is generally called a laser scanning unit (LSU) or the like. 
     Furthermore, the primary transfer portions  45  transfer images (the developer) on the surfaces of the photoconductors  41  to the surface of the intermediate transfer belt  48 . The secondary transfer portion  52  transfers an image (toner image) from the surface of the intermediate transfer belt  48  to the recording sheet  9  that is moving in the sheet conveyance path  300 . 
     The fixing portion  53  nips the recording sheet  9  with the image formed thereon between a fixing roller  531  and a pressure roller  532  and feeds the sheet to a downstream step. The fixing roller  531  includes a heater  5310 , such as a halogen heater, that is embedded therein. In this operation, the fixing portion  53  heats the developer on the recording sheet  9  and fixes the image to the recording sheet  9 . 
     The primary cleaning portions  47  clean the surfaces of the photoconductors  41  by removing the developer  90  that remains on the surfaces of the photoconductors  41 . In the example shown in  FIG. 2 , the primary cleaning portion  47  includes a cleaning blade  471 , a cleaning roller  472 , and a waste developer receiving portion  470 , wherein the cleaning blade  471  and the cleaning roller  472  remove the developer  90  from the surface of the photoconductor  41 . It is noted that in  FIG. 2 , the photoconductor  41  is drawn by an imaginary line (two-dot chain line). 
     The waste developer receiving portion  470  temporarily stores the developer  90  that has been removed from the surface of the photoconductor  41  by the cleaning blade  471  and the cleaning roller  472 . The image forming apparatus  10  further includes a developer conveying mechanism  7  that conveys the developer  90  in the waste developer receiving portion  470  to a waste developer collection container  8 . 
     [Developer Conveying Mechanism  7 ] 
     The following describes the developer conveying mechanism  7  with reference to  FIGS. 3-6 . The developer conveying mechanism  7  includes a first lateral conveyance path forming portion  71 , a first conveyance member  711 , a longitudinal passage forming portion  72 , a second lateral conveyance path forming portion  73 , and a second conveyance member  731 . 
     The first lateral conveyance path forming portion  71  forms a conveyance path of the developer  90  that extends along a lateral direction. The first lateral conveyance path forming portion  71  is, for example, a cylindrical member supported along the lateral direction. The first conveyance member  711  conveys the developer  90  in the lateral direction by rotating in the conveyance path formed by the first lateral conveyance path forming portion  71 . 
     It is noted that the lateral direction includes a horizontal direction (right sideways) and such directions that are slightly inclined with respect to the horizontal direction, for example, a direction (a diagonally horizontal direction) that forms an acute angle less than 45 degrees to the horizontal direction. 
     In the following description, the conveyance path of the developer  90  in the first lateral conveyance path forming portion  71  is referred to as a first lateral conveyance path  710 . The first lateral conveyance path forming portion  71  includes, inside thereof, the first conveyance member  711  disposed in the first lateral conveyance path  710 . In addition, the direction in which the first conveyance member  711  conveys the developer  90  is referred to as a first lateral direction R 1 . 
     The first conveyance member  711  is, for example, a conveyance screw that includes a rotation shaft portion  7111  and a blade portion  7112  that is formed in a spiral shape around the rotation shaft portion  7111 . It is noted that the first conveyance member  711  may be a coil-like member. 
     The first lateral conveyance path  710  communicates with the inside of the waste developer receiving portion  470  of the primary cleaning portion  47 . In addition, the first conveyance member  711  is continuously formed along the first lateral direction R 1  from the inside of the waste developer receiving portion  470  to the first lateral conveyance path  710 . In this case, the first lateral direction R 1  is a direction parallel to the rotation center line of the photoconductor  41 , and is a so-called main scanning direction. 
     Furthermore, a lower opening  712  as an outlet from which the developer  90  falls down, is formed in the vicinity of an end of the first lateral conveyance path forming portion  71  in the downstream side in the first lateral direction R 1 . 
     As a result, when the first conveyance member  711  rotates, the developer  90  is conveyed from the inside of the waste developer receiving portion  470  to the first lateral conveyance path  710 , further conveyed in the first lateral conveyance path  710  in the first lateral direction R 1 , and then falls down from the lower opening  712 . 
     The longitudinal passage forming portion  72  forms a passage that extends along a longitudinal direction so as to allow the developer  90  that has fallen down from the lower opening  712  to pass therethrough. The longitudinal passage forming portion  72  is, for example, a cylindrical member supported along a vertical direction. In the following description, the passage extending along a longitudinal direction formed by the longitudinal passage forming portion  72  is referred to as a longitudinal passage  720 . 
     It is noted that the longitudinal direction includes the vertical direction and such directions that are slightly inclined with respect to the vertical direction, for example, a direction (a diagonally vertical direction) that forms an acute angle less than 45 degrees to the vertical direction. 
     In the following description, the conveyance path of the developer  90  formed by the second lateral conveyance path forming portion  73  is referred to as a second lateral conveyance path  730 . The second lateral conveyance path forming portion  73  includes, inside thereof, the second conveyance member  731  disposed in the second lateral conveyance path  730 . In addition, the direction in which the second conveyance member  731  conveys the developer  90  is referred to as a second lateral direction R 2 . 
     When viewed from above, the second lateral direction R 2  intersects with the first lateral direction R 1 . That is, the first lateral conveyance path  710  and the second lateral conveyance path  730  are in a so-called twisted positional relation. In the present embodiment, when viewed from above, the second lateral direction R 2  is perpendicular to the first lateral direction R 1 . 
     In addition, the center line of the second lateral conveyance path  730  that extends along the second lateral direction R 2  is referred to as a second lateral conveyance path center line L 1 . When viewed from above, for example, the second lateral conveyance path center line L 1  matches the rotation center line of the second conveyance member  731 . 
     The developer  90  discharged from the lower opening  712  enters the longitudinal passage  720  from an inlet  721  of the longitudinal passage  720  that is provided at an upper end of the longitudinal passage forming portion  72 , and further passes through the longitudinal passage  720  downward. In the example shown in  FIG. 5 , when viewed from above, the lower opening  712  is formed inside the rim of the inlet  721  of the longitudinal passage  720 . For example, the lower opening  712  and the inlet  721  of the longitudinal passage  720  may have the same center in the second lateral direction R 2 . It is noted that, in  FIG. 5 , the first lateral conveyance path forming portion  71  is drawn by an imaginary line. 
     The second lateral conveyance path forming portion  73  is positioned below the longitudinal passage  720  and forms a conveyance path of the developer  90  that extends along a lateral direction. The second lateral conveyance path forming portion  73  is, for example, a cylindrical member supported along the lateral direction. The second conveyance member  731  is a member that conveys the developer  90  in the lateral direction by rotating in the second lateral conveyance path  730  formed by the second lateral conveyance path forming portion  73 . 
     The second conveyance member  731  is, for example, a conveyance screw that includes a rotation shaft portion  7311  and a blade portion  7312  that is formed in a spiral shape around the rotation shaft portion  7311 . It is noted that the second conveyance member  731  may be a coil-like member. 
     The image forming apparatus  10  further includes a driving source such as a motor (not shown). The first conveyance member  711  and the second conveyance member  731  are rotationally driven by, for example, the driving source and a gear mechanism that operates in conjunction with the movement of the driving source. 
     As shown in  FIG. 3 , the image forming apparatus  10  includes a plurality of first lateral conveyance path forming portions  71 , and the same number of first conveyance members  711  and longitudinal passage forming portions  72 . The first lateral conveyance path forming portions  71 , first conveyance members  711 , and longitudinal passage forming portions  72  are respectively provided in correspondence with the primary cleaning portions  47 , namely, in correspondence with the colors of the developer  90 . 
     On the other hand, the second lateral conveyance path forming portion  73  and the second conveyance member  731  are common to the plurality of first lateral conveyance path forming portions  71  and the plurality of longitudinal passage forming portions  72 . The plurality of first lateral conveyance path forming portions  71  are arranged at intervals in the second lateral direction R 2 . Similarly, the plurality of longitudinal passage forming portions  72  are arranged at intervals in the second lateral direction R 2 . 
     The developer  90  that has fallen into the second lateral conveyance path  730  is conveyed in the second lateral conveyance path  730  in the second lateral direction R 2  by the rotating second conveyance member  731 . The developer  90  is then conveyed to the vicinity of an end of the second lateral conveyance path  730  in the downstream side in the second lateral direction R 2 , and falls into the waste developer collection container  8  from an opening formed in the lower side of the second lateral conveyance path forming portion  73 . This allows the waste developer  90  of all colors to be collected in one waste developer collection container  8 . 
     As described above, the first lateral conveyance path  710  and the second lateral conveyance path  730  are conveyance paths of waste developer that has been removed from the surface of the photoconductor  41  by the primary cleaning portion  47  that cleans the surface of the photoconductor  41 . 
     Meanwhile, if the developer  90  discharged from the first lateral conveyance path  710  falls down in a state of deviating toward an inner wall surface  722  of the longitudinal passage  720 , a conveyance failure of the developer  90  may occur. 
     For example, the developer  90  discharged from the first lateral conveyance path  710  may stick to and accumulate on the inner wall surface  722 , and the longitudinal passage  720  may be clogged. In addition, the developer  90  that has passed through the longitudinal passage  720  may intensively accumulate on the peripheral of the outer edge of the second conveyance member  731  in the second lateral conveyance path  730 . In that case, the efficiency of conveyance of the developer  90  by the second conveyance member  731  in the second lateral conveyance path  730  may be degraded. 
     On the other hand, the developer conveying mechanism  7  has a configuration for preventing such a conveyance failure from occurring. In the following, the configuration is described. 
     As shown in  FIG. 5 , the lower opening  712  of the first lateral conveyance path forming portion  71  is formed such that its width expands from the upstream side to the downstream side in the first lateral direction R 1 . In the example shown in  FIG. 5 , the lower opening  712  is formed in the shape of an isosceles triangle where the width gradually expands from an edge  7121  in the upstream side in the first lateral direction R 1  along the pair of straight lines. The edge  7121  of the lower opening  712  in the upstream side in the first lateral direction R 1  corresponds to a vertex of a vertical angle of the isosceles triangle. 
     In the example shown in  FIG. 5 , the lower opening  712  is formed such that its width gradually expands from the upstream side to the downstream side in the first lateral direction R 1  in a range which, when viewed from above, extends from the edge  7121  of the lower opening  712  in the upstream side in the first lateral direction R 1  to a position exceeding the second lateral conveyance path center line L 1 . 
     Furthermore, in the example shown in  FIG. 5 , the lower opening  712  is formed in a range that extends, when viewed from above, from a predetermined position toward the downstream side in the first lateral direction R 1 . The predetermined position (the position of the edge  7121 ) is a position that is, when viewed from above, between the second lateral conveyance path center line L 1  and an edge  7211  of the inlet  721  of the longitudinal passage  720  in the upstream side in the first lateral direction R 1 . It is noted that the effect produced by forming the lower opening  712  in the above-described range is described in the fourth embodiment. 
       FIG. 6  is a vertical cross section of the developer conveying mechanism  7  that is conveying the developer  90 . In the present embodiment, upon reaching the lower opening  712 , the developer  90  falls down little by little as it advances with the width of the lower opening  712  gradually expanding. 
     With the above-described configuration, the developer  90  falls down in a state of dispersing in a relatively wide range that extends from a position in the upstream side in the first lateral direction R 1  to a position in the downstream side, not in the state of deviating toward the inner wall surface  722  of the longitudinal passage  720 . As a result, the developer  90  is difficult to stick to the inner wall surface  722  of the longitudinal passage  720 . Furthermore, the configuration restricts the efficiency of conveyance of the developer  90  from being degraded due to the intensive accumulation of the developer  90  on the peripheral of the outer edge of the second conveyance member  731 . 
     As understood from the above description, in the case where the developer  90  falls down from the first lateral conveyance paths  710  at an upper position to the second lateral conveyance path  730  at a lower position which both extend in the lateral direction, it is suitable to adopt the developer conveying mechanism  7  and the image forming apparatus  10  that includes the developer conveying mechanism  7 . This makes it possible to prevent a conveyance failure of the developer  90  from occurring. 
     In addition, in the example shown in  FIG. 5 , when viewed from above, the lower opening  712  is formed inside the rim of the inlet  721  of the longitudinal passage  720 . That is, when viewed from above, the rim of the lower opening  712  does not protrude outside of the rim of the inlet  721 . This makes it possible to prevent the developer  90  from sticking to the inner wall surface  722  of the longitudinal passage  720  in a more reliable manner. 
     Second Embodiment, Third Embodiment 
     Next, a description is given of a developer conveying mechanism  7 A provided in an image forming apparatus according to the second embodiment of the present disclosure, and a developer conveying mechanism  7 B provided in an image forming apparatus according to the third embodiment of the present disclosure, with reference to  FIGS. 7 and 8 . 
     The following describes the differences of the developer conveying mechanism  7 A and the developer conveying mechanism  7 B from the developer conveying mechanism  7 . The developer conveying mechanism  7 A and the developer conveying mechanism  7 B differ from the developer conveying mechanism  7  in the shape of the lower opening provided in the first lateral conveyance path forming portion  71 . 
       FIG. 7  is a plan cross-sectional view of the first lateral conveyance path forming portion  71  in the developer conveying mechanism  7 A.  FIG. 8  is a plan cross-sectional view of the first lateral conveyance path forming portion  71  in the developer conveying mechanism  7 B. In  FIGS. 7 and 8 , the same components as those shown in  FIGS. 1-6  are assigned the same reference signs. It is noted that in  FIGS. 7 and 8 , the first lateral conveyance path forming portion  71  is drawn by an imaginary line. 
     A lower opening  712 A as an outlet from which the developer  90  falls down, is formed in the vicinity of an end of the first lateral conveyance path forming portion  71  of the developer conveying mechanism  7 A in the downstream side in the first lateral direction R 1 . 
     Similarly, a lower opening  712 B as an outlet from which the developer  90  falls down, is formed in the vicinity of an end of the first lateral conveyance path forming portion  71  of the developer conveying mechanism  7 B in the downstream side in the first lateral direction R 1 . 
     As is the case with the lower opening  712 , when viewed from above, the lower openings  712 A and  712 B are each formed inside the rim of the inlet  721  of the longitudinal passage  720 . For example, the lower openings  712 A and  712 B and the inlet  721  have the same center in the second lateral direction R 2 . 
     As is the case with the lower opening  712 , the lower openings  712 A and  712 B are each formed such that the width expands from the upstream side to the downstream side in the first lateral direction R 1 . 
     More specifically, the lower openings  712 A and  712 B are each formed such that in a first range in the upstream side in the first lateral direction R 1 , the width gradually expands from the upstream side to the downstream side in the first lateral direction R 1 , and in a remaining second range, the width is constant. 
     In the example shown in  FIG. 7 , when viewed from above, the first range in which the width of the lower opening  712 A gradually expands, extends from the edge  7121  of the lower opening  712 A in the upstream side in the first lateral direction R 1  to the second lateral conveyance path center line L 1 . 
     On the other hand, in the example shown in  FIG. 8 , when viewed from above, the first range in which the width of the lower opening  712 B gradually expands, extends from the edge  7121  of the lower opening  712 B in the upstream side in the first lateral direction R 1  to a position exceeding the second lateral conveyance path center line L 1 . 
     Furthermore, in the examples shown in  FIGS. 7 and 8 , when viewed from above, the lower openings  712 A and  712 B are each formed in a range that extends from a position that is disposed between the second lateral conveyance path center line L 1  and the edge  7211  of the inlet  721  of the longitudinal passage  720  in the upstream side in the first lateral direction R 1 , toward the downstream side in the first lateral direction R 1 . It is noted that the effect produced by forming the lower openings  712 A and  712 B in the above-described range is described in the fourth embodiment. 
     In the first range of the lower opening  712 A, the lower opening  712 A is formed such that its width gradually expands from the edge  7121  in the upstream side in the first lateral direction R 1  along a pair of straight lines. On the other hand, in the first range of the lower opening  712 B, the lower opening  712 B is formed such that its width gradually expands from the edge  7121  in the upstream side in the first lateral direction R 1  along a pair of curved lines. 
     The adoption of the developer conveying mechanism  7 A or the developer conveying mechanism  7 B produces the same effect as the adoption of the developer conveying mechanism  7 . 
     Fourth Embodiment 
     Next, a description is given of a developer conveying mechanism  7 C provided in an image forming apparatus according to the fourth embodiment of the present disclosure with reference to  FIG. 9 . In  FIG. 9 , the same components as those shown in  FIGS. 1-8  are assigned the same reference signs. 
     The following describes the differences between the developer conveying mechanism  7 C and the developer conveying mechanism  7 . The developer conveying mechanism  7 C differs from the developer conveying mechanism  7  in the shape of the longitudinal passage forming portion. 
       FIG. 9  is a vertical cross-sectional view of the developer conveying mechanism  7 C. 
     A longitudinal passage forming portion  72 C of the developer conveying mechanism  7 C is a portion that forms the longitudinal passage  720  of the developer  90  that has fallen down from the lower opening  712 . The longitudinal passage  720  formed by the longitudinal passage forming portion  72 C spreads from above to below. That is, the inner wall surface  722  of the longitudinal passage forming portion  72 C is formed to spread from above to below. 
     With the adoption of the developer conveying mechanism  7 C, it becomes possible to prevent the developer  90  from sticking to the inner wall surface  722  of the longitudinal passage  720  in a more reliable manner. 
     Fifth Embodiment 
     Next, a description is given of a developer conveying mechanism  7 D provided in an image forming apparatus according to the fifth embodiment of the present disclosure with reference to  FIGS. 10-12 . 
     The following describes the differences between the developer conveying mechanism  7 D and the developer conveying mechanism  7 . The developer conveying mechanism  7 D differs from the developer conveying mechanism  7  in the position and shape of the lower opening. 
       FIG. 10  is a vertical cross-sectional view of the developer conveying mechanism  7 D.  FIG. 11  is a plan cross-sectional view of the first lateral conveyance path forming portion  71  in the developer conveying mechanism  7 D.  FIG. 12  is a vertical cross-sectional view of the developer conveying mechanism  7 D that is conveying the developer  90 . In  FIGS. 10-12 , the same components as those shown in  FIGS. 1-9  are assigned the same reference signs. It is noted that in  FIG. 11 , the first conveyance members  711  is drawn by an imaginary line. 
     In the vicinity of an end of the first lateral conveyance path forming portion  71  of the developer conveying mechanism  7 D in the downstream side in the first lateral direction R 1 , a lower opening  712 D as an outlet from which the developer  90  falls down, is formed. 
     As is the case with the lower opening  712 , when viewed from above, the lower opening  712 D is formed inside the rim of the inlet  721  of the longitudinal passage  720 . For example, the lower opening  712 D and the inlet  721  may have the same center in the second lateral direction R 2 . 
     The lower opening  712 D is formed in a range that extends, when viewed from above, from a predetermined position toward the downstream side in the first lateral direction R 1 . The predetermined position (the position of the edge  7121 ) is a position that is disposed between the second lateral conveyance path center line L 1  and the edge  7211  of the inlet  721  of the longitudinal passage  720  in the upstream side in the first lateral direction R 1 . 
     For example, the lower opening  712 D is formed in a range that extends, when viewed from above, from a position that overlaps with the rotation shaft portion  7311  of the second conveyance member  731 , toward the downstream side in the first lateral direction R 1 . 
     It is noted that the lower opening  712 D is not necessarily be formed such that its width expands from the upstream side to the downstream side in the first lateral direction R 1 . In the example shown in  FIG. 11 , the lower opening  712 D is formed such that its width is constant from the upstream side to the downstream side in the first lateral direction R 1 . 
     As shown in  FIG. 12 , the developer  90  discharged from the lower opening  712 D falls from a position that is, when viewed from above, disposed away from the inner wall surface  722  of the longitudinal passage  720  toward the second lateral conveyance path center line L 1 . As a result, the developer  90  is difficult to stick to the inner wall surface  722  of the longitudinal passage  720 . 
     Furthermore, the developer  90  falls onto the rotation shaft portion  7311  of the second conveyance member  731  and its peripheral. As a result, the configuration restricts the degradation of the efficiency of conveyance of the developer  90  due to the intensive accumulation of the developer  90  on the peripheral of the outer edge of the second conveyance member  731 . 
     In the case where the developer  90  falls down from the first lateral conveyance paths  710  at an upper position to the second lateral conveyance path  730  at a lower position which both extend in the lateral direction, it is suitable to adopt the developer conveying mechanism  7 D and an image forming apparatus including the developer conveying mechanism  7 D. This makes it possible to prevent a conveyance failure of the developer  90  from occurring. 
     Application Examples 
     In the developer conveying mechanisms  7 ,  7 A,  7 B, and  7 D, the inner wall surface of the longitudinal passage  720  may be formed in the shape of a cylinder, an elliptic cylinder, or a rectangular cylinder. In addition, in the developer conveying mechanism  7 C, the inner wall surface of the longitudinal passage forming portion  72  may be formed in the shape of a remaining part of a cone, an elliptic cone, or a rectangular cone except for a part including the apex. 
     The developer conveying mechanisms  7 ,  7 A,  7 B,  7 C, and  7 D may each be a mechanism that conveys, to the developing portion  43 , the developer supplied from the developer supply portions  40 . For example, the first lateral conveyance path  710  may be a conveyance path of the developer supplied from the developer supply portions  40 . Furthermore, the second lateral conveyance path  730  may be a conveyance path that extends from a lower position below the longitudinal passage  720  to an upper position above the developer inlet of the developing portion  43 . 
     In addition, an edge of the lower opening  712 ,  712 A,  712 B,  712 D in the downstream side in the first lateral direction R 1  may be positioned more in the downstream side in the first lateral direction R 1  than an edge of the inlet  721  of the longitudinal passage  720  in the downstream side in the first lateral direction R 1 . 
     It is noted that the developer conveying mechanism and the image forming apparatus of the present disclosure may be configured by freely combining, within the scope of claims, the above-described embodiments and application examples, or by modifying the embodiments and application examples or omitting a part thereof. 
     It is to be understood that the embodiments herein are illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.