Patent Publication Number: US-10768570-B2

Title: Image forming apparatus provided with recovery container for waste toner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority under 35 U.S.C. § 119 to Japanese patent application No. 2017-053933 filed on Mar. 21, 2017, the entire disclosure of which are incorporated herein by reference. 
     BACKGROUND 
     Technological Field 
     The present invention relates to an image forming apparatus. More specifically, the present invention relates to an image forming apparatus provided with a recovery container for collecting waste toner. 
     Description of the Related Art 
     As an electrophotographic image forming apparatus, there is an MFP (Multi Function Peripheral) having a scanner function, a facsimile function, a copying function, a function as a printer, a data communication function, and a server function. As an electrophotographic image forming apparatus, there are a facsimile apparatus, a copying machine, a printer, and the like. 
     Generally, an image forming apparatus forms a toner image by developing an electrostatic latent image formed on a photosensitive member with a developing device. The image forming apparatus transfers the toner image to the sheet, and then fixes the toner image on the sheet by the fixing device. As a result, the image forming apparatus forms an image on the paper. Some image forming apparatuses form a toner image by developing the electrostatic latent image on the surface of the photosensitive member using a developing device, and transfer the toner image to an intermediate transfer belt by using a primary transfer roller. The image forming apparatus secondarily transfers the toner image on the intermediate transfer belt to the paper using a secondary transfer roller. In this case, the photosensitive member and the intermediate transfer belt serve as image bearing members. Toner which was not used for development in the developing device or toner which was not transferred but remains on the photosensitive member or on the intermediate transfer belt is collected into the recovery container as waste toner. 
     Among conventional image forming apparatuses, there are various positional relationships between an image forming unit including a photosensitive member and a developing device, and a conveying path for conveying a sheet. As an example, there are an image forming apparatus having a vertical conveying path on the side of the image forming unit, and an image forming apparatus having a conveying path in a substantially horizontal direction on the underside of the image forming unit. 
     Among them, an image forming apparatus having a substantially horizontal conveying path on the underside of the image forming unit has an advantage that the space under the image forming unit can be used as a conveying path, being compared to an image forming apparatus having a vertical conveying path on the side of the image forming unit. 
     Conventional techniques related to waste toner recovery containers are disclosed in, for example, the below Documents 1 and 2. 
     The documents 1 and 2 below disclose a waste toner recovery container. The waste toner recovery container has an introduction port for accepting the waste toner discharged from the image forming unit that forms an image on the sheet. The waste toner recovery container has a waste toner accommodating chamber for accommodating the waste toner received from the introduction port. The waste toner recovery container is provided with an auger which receives driving power and transports the waste toner accommodated in the waste toner accommodating chamber while rotating. The waste toner recovery container includes a main body unit which is provided in a movement path of the waste toner moving from the introduction port to the waste toner accommodating chamber and vibrates by contacting the auger. The waste toner recovery container includes a breaking member having a sticking portion which is continuous with the main body unit and is fixed while being separated from the moving path of the waste toner. 
     DOCUMENT(S) 
     Document(s) Related to Patent(s) 
     
         
         [Document 1] Japanese Unexamined Patent Publication No. 2013-242402 
         [Document 2] Japanese Unexamined Patent Publication No. 2016-194729 
       
    
     In an image forming apparatus having a substantially horizontal conveying path on the underside of the image forming unit, the space secured in front of the image forming unit and the conveying path is narrow. This is because it is necessary to guarantee the operability when a jam recovery operation is performed by enabling the user to access the conveying path immediately from the front of the image forming apparatus, when a jam occurs in the conveying path. 
     In view of the above circumstances, in this type of conventional image forming apparatus, the waste toner caused in the image forming unit has once been conveyed to the rear portion of the image forming unit. Thereafter, the waste toner was conveyed to a recovery container provided at a side portion or a front portion of the image forming unit. As a result, the conveying path of the waste toner becomes longer, and the space for arranging the waste toner conveying path becomes larger, which hinders further downsizing of the image forming apparatus. 
     SUMMARY 
     The present invention has been made to solve the above-described problems, and an object thereof is to provide an image forming apparatus capable of downsizing. 
     To achieve at least one of the abovementioned objects, according to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention comprises: an image forming unit that forms an image on a sheet, a sheet conveying unit configured to convey a sheet along a conveying path extending in a substantially horizontal direction in a lower portion of the image forming unit, a recovery container that is provided in front of the image forming unit and above the conveying path, and that stores waste toner discharged from the image forming unit, and a waste toner conveying pipe that conveys the waste toner discharged from the image forming unit to the recovery container, without passing through a rear portion and a side portion of the image forming unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention: 
         FIG. 1  is a perspective view showing a configuration of an image forming apparatus  100 , according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view showing configurations of a sheet conveying unit  70 , an image forming unit  80 , and a fixing device  90 , in the image forming apparatus  100 , according to the embodiment of the present invention. 
         FIG. 3  is a perspective view showing a configuration of a recovery container  20 , according to the embodiment of the present invention. 
         FIG. 4  is a cross-sectional view taken along the line IV-IV (a plane including a rotation axis  25   a ) in  FIG. 3 . 
         FIG. 5  is a cross-sectional view taken along the line V-V of  FIG. 3 . 
         FIG. 6  is a cross-sectional view showing a configuration of a waste toner conveying pipe  130 , before the recovery container  20  is mounted on the image forming apparatus main body  100   a , in the embodiment of the present invention. 
         FIG. 7  is a cross-sectional view showing a configuration of a waste toner conveying pipe  130 , after the recovery container  20  is mounted on the image forming apparatus main body  100   a , in the embodiment of the present invention. 
         FIG. 8  is a perspective view showing a method of transmitting a driving force between a driving unit  120  and a drive transmission unit  23   b , according to an embodiment of the present invention. 
         FIG. 9  is a diagram schematically showing the movement of waste toner in a recovery container  20 , according to an embodiment of the present invention. 
         FIG. 10  is a cross-sectional view schematically showing a configuration in the vicinity of a sensor  126 , in an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. 
     In the present embodiment, the case where the image forming apparatus is an MFP will be described. The image forming apparatus may be a MFP, a facsimile machine, a copying machine, a printer, or the like. 
     In the drawings, the direction from the front surface to the rear surface of the image forming apparatus is defined as the positive direction of the y axis. The direction from the left side to the right side of the image forming apparatus when the image forming apparatus is viewed from the front is the positive direction of the x axis. The direction from the lower side to the upper side of the image forming apparatus along the vertical direction is the positive direction of the z axis. The x, y, and z axes shall be orthogonal to each other. 
     In the following description, the left side of the image forming apparatus viewed from the front of the image forming apparatus may be referred to as “left”. The right side of the image forming apparatus viewed from the front of the image forming apparatus may be referred to as “right”. 
     First, the configuration of the entire image forming apparatus according to the present embodiment will be described. 
       FIG. 1  is a perspective view showing a configuration of an image forming apparatus  100 , according to an embodiment of the present invention. 
     Referring to  FIG. 1 , image forming apparatus  100  in the present embodiment mainly includes recovery container  20 , control unit  50 , scanner unit  51 , an operation panel  52 , a sheet feed cassette  53 , a manual feed tray  54 , a paper discharge tray  55 , a sheet conveying unit  70 , an image forming unit  80 , a fixing device  90 , and the like. 
     The control unit  50  controls the entire image forming apparatus  100 . The control unit  50  includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a HDD (Hard Disk Drive), and the like. 
     The scanner unit  51  reads an image of a document, and is provided at the uppermost part of the image forming apparatus  100 . 
     The operation panel  52  receives various operations and performs various displays, and is provided in front of the scanner unit  51  and on the front of the image forming apparatus  100 . 
     The sheet feed cassette  53  is a portion for storing sheets, and is provided at the lowermost part of the image forming apparatus  100 . The number of sheet feed cassettes  53  is arbitrary, and it is plural (three stages) in the embodiment. 
     The manual feed tray  54  is a portion where manual feed paper is placed, and is provided on the right side surface of the image forming apparatus  100 . 
     The paper discharge tray  55  is a portion to which the printed paper is discharged, and is provided on the left side surface of the image forming apparatus  100 . 
     The sheet conveying unit  70  is a portion that conveys a sheet, which is a central portion of the image forming apparatus and is provided between the sheet feed cassette  53  and the image forming unit  80 . 
     The image forming unit  80  is a portion for forming an image (toner image) on a sheet, which is a central portion of the image forming apparatus  100  and is provided between the scanner unit  51  and the sheet conveying unit  70 . 
     The fixing device  90  is a portion that fixes the toner image on the sheet, and is provided on a conveying path TR 3  of the sheet conveying unit  70  which will be described later. 
     The recovery container  20  is a container that stores the waste toner discharged from the image forming unit  80 , and is provided in front of the image forming unit  80  and above the sheet conveying unit  70 . The recovery container  20  can be attached to and detached from the image forming apparatus main body  100   a.    
     The image forming apparatus  100  further includes a door  56  that can be opened and closed on the front surface thereof. When the door  56  is opened, the recovery container  20  and the sheet conveying unit  70  (in particular, the conveying paths TR 1 , TR 2 , and TR 3  to be described later) are exposed. The user of the image forming apparatus  100  can take out the recovery container  20  from the image forming apparatus main body  100   a  while the door  56  opened. The user of the image forming apparatus  100  can perform jam recovering action, when a jam occurs in the conveying paths TR 1 , TR 2 , or TR 3 . 
       FIG. 2  is a cross-sectional view showing configurations of the sheet conveying unit  70 , the image forming unit  80 , and the fixing device  90  in the image forming apparatus  100 , according to the embodiment of the present invention. 
     Referring to  FIG. 2 , sheet conveying unit  70  has conveying paths TR 1 , TR 2 , and TR 3  for conveying the sheet. The conveying path TR 1  extends in a substantially vertical direction from the sheet feed cassette  53  to a joining position with the conveying path TR 2 . The conveying path TR 2  extends substantially in the horizontal direction from the manual feed tray  54  to the joining position with the conveying path TR 1 . The conveying path TR 3  extends substantially in the horizontal direction at the lower portion of the image forming unit  80 . The conveying path TR 3  extends from the joining position of the conveying path TR 1  and the conveying path TR 2  to the discharge tray  55 . 
     The sheet conveying unit  70  includes conveying rollers  103   a  and  103   b , a timing roller  103   c , and a discharge roller  103   d . The paper feed tray  11  is provided at a lower portion of the image forming apparatus main body  100   a  and accommodates paper for forming images. 
     The conveying roller  103   a  is provided on the conveying path TR 1  extends from the sheet feed cassette  53 . The conveying roller  103   b  is provided on the conveying path TR 2  extends from the manual feed tray  54 . The timing roller  103   c  is provided on the conveying path TR 3  downstream from the joining position of the conveying path TR 1  and the conveying path TR 2 , and is provided on the upstream side of the secondary transfer roller  111 . The sheet discharge roller  103   d  is provided in the most downstream portion of the conveying path TR 3 . 
     The image forming unit  80  synthesizes images of four colors of Y (yellow), M (magenta), C (cyan), and K (black) in a so-called tandem system, and transfers the toner image to the paper. The image forming unit  80  includes four sets of image forming units  81 Y,  81 M,  81 C, and  81 K, and exposure devices  106   a ,  106   b ,  106   c , and  106   d . The image forming unit  80  includes rotating rollers  107 , an intermediate transfer belt  109 , and primary transfer rollers  108   a ,  108   b ,  108   c , and  108   d . The image forming unit  80  includes a secondary transfer roller  111 , a cleaning device  112 , toner bottles  118   a ,  118   b ,  118   c , and  118   d , and the like. 
     Each of the image forming units  81 Y,  81 M,  81 C, and  81 K is juxtaposed on the top of the intermediate transfer belt  109 . The image forming unit  81 Y includes a photosensitive member  102   a , a charging device  105   a , a developing device  104   a , a cleaning device  110   a , and the like. The photosensitive member  102   a  is rotationally driven in a direction indicated by an arrow AR 11  in  FIG. 2 . A charging device  105   a , a developing device  104   a , and a cleaning device  110   a  are arranged around the photosensitive member  102   a.    
     The image forming unit  81 M includes a photosensitive member  102   b , a charging device  105   b , a developing device  104   b , a cleaning device  110   b , and the like. The image forming unit  81 C includes a photosensitive member  102   c , a charging device  105   c , a developing device  104   c , a cleaning device  110   c , and the like. The image forming unit  81 K includes a photosensitive member  102   d , a charging device  105   d , a developing device  104   d , a cleaning device  110   d , and the like. Each of the image forming units  81 M,  81 C, and  81 K has the same configuration as that of the image forming unit  81 Y. 
     Each of the exposure devices  106   a ,  106   b ,  106   c , and  106   d  is provided above each of the image forming units  81 Y,  81 M,  81 C, and  81 K. The intermediate transfer belt  109  is provided under the image forming units  81 Y,  81 M,  81 C, and  81 K. The intermediate transfer belt  109  is annular, and is laid across rotating rollers  107 . The intermediate transfer belt  109  is rotationally driven in a direction indicated by an arrow AR 12  in  FIG. 2 . Each of the primary transfer rollers  108   a ,  108   b ,  108   c , and  108   d  faces each of the photosensitive members  102   a ,  102   b ,  102   c , and  102   d  with the intermediate transfer belt  109  interposed therebetween. The secondary transfer roller  111  is in contact with the intermediate transfer belt  109  on the conveying path TR 3 . The interval between the secondary transfer roller  111  and the intermediate transfer belt  109  can be adjusted by a pressure contacting and separating mechanism (not shown). 
     The rotating roller  107  includes a plurality of rotating rollers  107   a  and a rotating roller  107   b . Each of the plurality of rotating rollers  107   a  is disposed in a substantially horizontal direction to each other, and the intermediate transfer belt  109  is stretched. The rotating roller  107   b  is disposed below the plurality of rotating rollers  107   a , and the intermediate transfer belt  109  is stretched. 
     The cleaning device  112  is in contact with the intermediate transfer belt  109 , in the vicinity of the rotating roller  107   b  at the lowermost part, and between the rotating roller  107   a  and the rotating roller  107   b . The cleaning device  112  removes the waste toner on the intermediate transfer belt  109  at this position. 
     Toner bottles  118   a ,  118   b ,  118   c , and  118   d  are located above exposure devices  106   a ,  106   b ,  106   c , and  106   d.    
     The fixing device  90  is provided on the conveying path TR 3  between the secondary transfer roller  111  and the discharge roller  103   d . The fixing device  90  includes a heating roller  116  and a pressure roller  117 . The fixing device  90  fixes the toner image on the sheet by conveying it along the conveying path TR 3  while gripping the sheet bearing the toner image by the nip portion between the heating roller  116  and the pressure roller  117 . 
     The image forming apparatus  100  rotates the photosensitive member  102   a  to charge the surface of the photosensitive member  102   a  to a desired potential, by the charging device  105   a . In the image forming apparatus  100 , the surface of the charged photosensitive member  102   a  is exposed by the exposure device  106   a  according to the image formation information, and an electrostatic latent image according to the image formation information is written on the surface of the photosensitive member  102   a . The electrostatic latent image is held by the photosensitive member  102   a.    
     Next, the image forming apparatus  100  supplies toner from the developing device  104   a  to the photosensitive member  102   a  on which the electrostatic latent image has been formed (development with toner). As a result, the image forming apparatus  100  forms a toner image of Y color on the surface of the photosensitive member  102   a.    
     The image forming apparatus  100  forms toner images of MCK colors on the surfaces of the photosensitive members  102   b ,  102   c , and  102   d  in the same manner. 
     Next, the image forming apparatus  100  sequentially transfers the toner images of the respective colors formed on the photosensitive members  102   a ,  102   b ,  102   c , and  102   d  onto the surface of the intermediate transfer belt  109  (primary transfer), by using each of the primary transfer rollers  108   a ,  108   b ,  108   c , and  108   d . On the surface of the intermediate transfer belt  109 , a toner image in which toner images of respective colors are synthesized is formed. 
     Subsequently, the image forming apparatus  100  conveys the toner image formed on the surface of the intermediate transfer belt  109  to a position facing the secondary transfer roller  111 , by the rotating roller  107 . 
     Meanwhile, the image forming apparatus  100  feeds the paper placed in the sheet feed cassette  53  by a paper feed roller (not shown), conveys the paper along the conveying path TR 1  to the joining position with the conveying path TR 2  using the conveying roller  103   a . Or, the image forming apparatus  100  feeds the paper placed on the manual feed tray  54  by a paper feed roller (not shown), and conveys the paper along the conveying path TR 2  to the joining position with the conveying path TR 1  by using the conveying roller  103   b . Then, the image forming apparatus  100  guides the sheet conveyed to the joining position of the conveying path TR 1  and the conveying path TR 2  along the conveying path TR 3  between the intermediate transfer belt  109  and the secondary transfer roller  111  at a predetermined timing, using the timing roller  103   c . Then, the image forming apparatus  100  transfers the toner image formed on the surface of the intermediate transfer belt  109  to the sheet by the secondary transfer roller  111 . 
     The image forming apparatus  100  guides the sheet to which the toner image has been transferred to the fixing device  90 , and fixes the toner image on the sheet by the fixing device  90 . Thereafter, the image forming apparatus  100  discharges the sheet on which the toner image has been fixed onto the paper discharge tray  55 , by the paper discharge roller  103   d.    
     The image forming apparatus  100  supplies the toner stored in the appropriate color bottle among the YMCK toner bottles  118   a ,  118   b ,  118   c , and  118   d  to the developing devices  104   a ,  104   b ,  104   c , or  104   d  by image formation, when the amount of toner in the developing units  104   a ,  104   b ,  104   c , or  104   d  decreases due to image formation. 
     The image forming apparatus  100  further includes waste toner conveying pipes  120   a ,  120   b ,  120   c , and  120   d  (an example of a first waste toner conveying pipe). The image forming apparatus  100  further includes waste toner conveying pipes  121   a ,  121   b ,  121   c , and  121   d  (an example of a first waste toner conveying pipe) and a waste toner conveying pipe  122  (an example of a second waste toner conveying pipe). The waste toner conveying pipes  120   a ,  120   b ,  120   c , and  120   d , the waste toner conveying pipes  121   a ,  121   b ,  121   c , and  121   d  and the waste toner conveying pipe  122  convey the waste toner. The waste toner is discharged from members having different functions constituting the image forming unit  80 . 
     The image forming apparatus  100  removes residual waste toner (waste toner discharged from each of the photosensitive members  102   a ,  102   b ,  102   c , and  102   d ) on each of the photosensitive members  102   a ,  102   b ,  102   c , and  102   d  without being transferred to the intermediate transfer belt  109 , by using each of the cleaning devices  110   a ,  110   b ,  110   c , and  110   d . The image forming apparatus  100  conveys the waste toner to the recovery container  20  using each of the waste toner conveying pipes  120   a ,  120   b ,  120   c , and  120   d.    
     Each of the waste toner conveying pipes  120   a ,  120   b ,  120   c , and  120   d  projects toward the front of the image forming apparatus  100 , from each of the cleaning devices  110   a ,  110   b ,  110   c , and  110   d , and is connected to the recovery container  20 . Therefore, the image forming apparatus  100  conveys the waste toner discharged from each of the photosensitive members  102   a ,  102   b ,  102   c , and  102   d  to the front recovery container  20 , without passing through the rear portion and the side portion of the image forming unit  80 . 
     The image forming apparatus  100  conveys the waste toner discharged from each of the developing devices  104   a ,  104   b ,  104   c , and  104   d  to the recovery container  20 , by using each of the waste toner conveying pipes  121   a ,  121   b ,  121   c , and  121   d.    
     Each of the waste toner conveying pipes  121   a ,  121   b ,  121   c , and  121   d  projects toward the front of the image forming apparatus  100 , from each of the developing devices  104   a ,  104   b ,  104   c , and  104   d , and is connected to the recovery container  20 . Therefore, the image forming apparatus  100  conveys the waste toner discharged from each of the developing devices  104   a ,  104   b ,  104   c , and  104   d  to the front recovery container  20 , without passing through the rear portion and the side portion of the image forming unit  80 . 
     The image forming apparatus  100  removes the waste toner remaining on the intermediate transfer belt  109  (waste toner discharged from the intermediate transfer belt  109 ) without being transferred onto the sheet by using the cleaning device  112 . The image forming apparatus  100  transports the waste toner to the recovery container  20  using the waste toner conveying pipe  122 . 
     The waste toner conveying pipe  122  protrudes from the cleaning device  112  toward the front of the image forming apparatus  100  and is connected to the recovery container  20 . Therefore, the image forming apparatus  100  conveys the waste toner discharged from the intermediate transfer belt  109  to the front recovery container  20 , without passing through the rear portion and the side portion of the image forming unit  80 . 
     Next, the configuration of the recovery container in this embodiment will be described. 
       FIG. 3  to  FIG. 5  are diagrams showing a configuration of a recovery container  20  according to an embodiment of the present invention.  FIG. 3  is a perspective view.  FIG. 4  is a cross-sectional view taken along the line IV-IV (the plane including the rotation axis  25   a ) in  FIG. 3 .  FIG. 5  is a cross-sectional view taken along line V-V in  FIG. 3 . In  FIG. 3 , for convenience of explanation, illustration of the spiral blade portions in each of the first conveying units  23  and  24  and the second conveying unit  25  is omitted. 
     With reference to  FIG. 3  to  FIG. 5 , the recovery container  20  includes a casing  21 , first conveying units  23  and  24  (an example of a first conveying unit), a second conveying unit  25  (an example of a second conveying unit), and a detection window  30 . In the casing  21 , first conveying units  23  and  24  and a second conveying unit  25  are provided. 
     The casing  21  includes a left bottom portion  21   a , a center bottom portion  21   b , a right bottom portion  21   c , a ceiling portion  21   d , and front side walls  22   a  and  22   b . The casing  21  includes a rear side wall  22   c , a left side wall  22   d , and a right side wall  22   e . The casing  21  includes receiving ports  26   a ,  26   b ,  26   c , and  26   d  (an example of a first receiving port). The casing  21  includes receiving ports  27   a ,  27   b ,  27   c , and  27   d  (an example of a first receiving port). The casing  21  includes a receiving port  28   a  (an example of a second receiving port), a conveying pipe  29  (an example of a separating unit), and the like. 
     The left bottom portion  21   a  is a bottom portion of the left end portion of the recovery container  20  and extends in a substantially horizontal direction. The right bottom portion  21   c  is the bottom portion of the right end portion of the recovery container  20  and extends obliquely downward to the left toward the boundary with the center bottom portion  21   b . The center bottom portion  21   b  is a bottom portion between the left bottom portion  21   a  and the right bottom portion  21   c , and extends diagonally downward to the right from the boundary with the left bottom portion  21   a  toward the boundary with the right bottom portion  21   c.    
     The front side wall  22   a  is continuous with the left bottom portion  21   a  on the front left side of the recovery container  20 , and is an upright side wall. The front side wall  22   b  is continuous with the center bottom  21   b  and the right bottom  21   c  on the front right side of the recovery container  20 , and is an upright side wall. The front side wall  22   b  protrudes forward from the front side wall  22   a . The rear side wall  22   c  is continuous with the left bottom portion  21   a , the center bottom portion  21   b , and the right bottom portion  21   c  on the rear side of the recovery container  20 , and is an upright side wall. 
     The ceiling portion  21   d  is continuous with the front side walls  22   a  and  22   b , the rear side wall  22   c , the left side wall  22   d , and the right side wall  22   e , and extends in a substantially horizontal direction. 
     The portion having the center bottom portion  21   b  and the right bottom portion  21   c  of the recovery container  20  as the bottom surface is deeper than the portion having the left bottom portion  21   a  as the bottom surface. The space defined by the center bottom portion  21   b , the right bottom portion  21   c , the front side wall  22   b , the rear side wall  22   c , and the right side wall  22   e , which is the space outside the conveying pipe  29  constitutes the accommodating unit SP for accommodating the waste toner. 
     The conveying pipe  29  is provided adjacent to the center bottom portion  21   b  and the front side wall  22   b . The conveying pipe  29  accommodates a part of the second conveying unit  25 . The conveying pipe  29  separates a portion (left side portion) on the upstream side in the conveying direction of the second conveying unit  25  in the second conveying unit  25 , from the accommodating unit SP. The conveying pipe  29  exposes a portion (right side portion) of the second conveying unit  25  on the downstream side in the conveying direction of the second conveying unit  25 , to the accommodating unit SP. The conveying pipe  29  extends diagonally upward to the right from the boundary between the center bottom portion  21   b  and the right bottom portion  21   c  (the lowermost end portion of the casing  21 ). 
     The cross-sectional shape of the conveying pipe  29  is arbitrary. In addition to the rectangular shape as in this embodiment, the cross-sectional shape of the conveying pipe  29  may be a circular shape or another shape, and is preferably determined from the viewpoint of space saving. 
     Receiving ports  26   a ,  26   b ,  26   c , and  26   d , receiving ports  27   a ,  27   b ,  27   c , and  27   d  and a receiving port  28   a  are formed in the rear side wall  22   c . A receiving port  28   b  (an example of a second receiving port) is formed in the rear side wall  29   a  of the conveying pipe  29 . 
     Each of the receiving ports  26   a ,  26   b ,  26   c , and  26   d  (an example of the photosensitive member waste toner receiving port) is an opening for receiving waste toner (waste toner discharged from the photosensitive members  102   a ,  102   b ,  102   c , and  102   d ). The waste toner is conveyed by the waste toner conveying pipes  120   a ,  120   b ,  120   c , and  120   d . The receiving ports  26   a ,  26   b ,  26   c , and  26   d  are arranged in a substantially horizontal direction. 
     Each of the receiving ports  27   a ,  27   b ,  27   c , and  27   d  (an example of the developing device waste toner receiving port) is an opening for receiving waste toner (waste toner discharged from the developing devices  104   a ,  104   b ,  104   c , and  104   d ). The waste toner is conveyed by the waste toner conveying pipes  121   a ,  121   b ,  121   c , and  121   d . The receiving ports  27   a ,  27   b ,  27   c , and  27   d  are arranged in a substantially horizontal direction. 
     The receiving ports  28   a  and  28   b  are openings for receiving waste toner conveyed by the waste toner conveying pipe  122  (waste toner discharged from the intermediate transfer belt  109  and waste toner removed by the cleaning device  112 ). The receiving ports  28   a  and  28   b  are provided below the receiving ports  26   a ,  26   b ,  26   c , and  26   d  and the receiving ports  27   a ,  27   b ,  27   c , and  27   d.    
     The detection window  30  is provided at a position above the first conveying units  23  and  24 , in the rear side wall  22   c . The detection window  30  protrudes rearward from the rear side wall  22   c . The detection window  30  is a detection position of the waste toner contained in the casing  21 , for the control unit  50  to detect the waste toner using the sensor  126  ( FIG. 10 ) described later. 
     The first conveying units  23  and  24  convey the waste toner in the casing  21 . The first conveying units  23  and  24  convey the waste toner in a substantially horizontal direction and equalize the upper surface of the waste toner accommodated in the accommodating unit SP. 
     The first conveying unit  23  is provided above the left bottom portion  21   a  and includes a rotary shaft  23   a , a drive transmission portion  23   b , a blade portion  23   c , a rod portion  23   d , and a blade portion  23   e.    
     The rotary shaft  23   a  is rotatably supported with respect to each of the left side wall  22   d  and the right side wall  22   e , and extends in a substantially horizontal direction. 
     The drive transmission portion  23   b  is provided at the right end portion of the rotary shaft  23   a  protruding to the outside of the casing  21 . The drive transmission portion  23   b  transmits a driving force for rotationally driving the rotary shaft  23   a , the blade portion  23   c , the rod portion  23   d , and the blade portion  23   e.    
     The blade portion  23   c  is attached to the left side position of the rotary shaft  23   a . The blade portion  23   c  is rotatable around the rotary shaft  23   a  and has the shape of a spiral blade. The blade portion  23   c  transports the waste toner in the direction of the rod portion  23   d  (to the right). 
     The blade portion  23   e  is attached to the right side position of the rotary shaft  23   a . The blade portion  23   e  is rotatable around the rotary shaft  23   a  and has the shape of a spiral blade. The blade portion  23   e  transports the waste toner in the direction of the rod portion  23   d  (left direction). 
     The rod portion  23   d  is provided between the blade portion  23   c  and the blade portion  23   e , and does not have blades. 
     The first conveying unit  24  is provided between the first conveying unit  23  and the rear side wall  22   c , and has substantially the same configuration as the first conveying unit  23 . The first conveying unit  24  includes a rotary shaft  24   a  corresponding to the rotary shaft  23   a  and a drive transmission unit  24   b  corresponding to the drive transmission unit  23   b . The first conveying unit  24  includes a blade portion  24   c  corresponding to the blade portion  23   c , a rod portion  24   d  corresponding to the rod portion  23   d , and a blade portion  24   e  corresponding to the blade portion  23   e.    
     It is to be noted that the casing  21  may further include a wall that partitions the first conveying units  23  and  24 . 
     The second conveying unit  25  transports the waste toner in the casing  21 . The second conveying unit  25  conveys the waste toner received from the second receiving port  28   b  obliquely upward and rightward (in a direction forming an angle with respect to each of the horizontal direction and the vertical direction) from the lowermost end portion of the casing  21 . The second conveying unit  25  transports the waste toner to a position higher than the detection window  30  and the first conveying units  23  and  24 . The second conveying unit  25  includes a rotary shaft  25   a , a drive transmission portion  25   b , and a blade portion  25   c.    
     The left end portion of the rotary shaft  25   a  (the upstream end portion in the conveying direction of the second conveying unit  25 ) is rotatably supported with respect to the central bottom portion  21   b . The right end portion of the rotary shaft  25   a  (the downstream end portion in the conveying direction of the second conveying unit  25 ) is released. The right end portion of the rotary shaft  25   a  is located above the detection window  30  and the first conveying units  23  and  24 . Further, the rotary shaft  25   a  is offset toward the lower surface  29   b  side of the conveying pipe  29  in the conveying pipe  29 . 
     The drive transmission portion  25   b  is provided at the left end portion of the rotary shaft  25   a  protruding to the outside of the casing  21 . The drive transmission portion  25   b  transmits a driving force for rotationally driving the rotary shaft  25   a  and the blade portion  25   c.    
     The blade portion  25   c  is rotatable around the rotary shaft  25   a  and has the shape of a spiral blade. The blade portion  25   c  is attached over the entire rotary shaft  25   a . The blade portion  25   c  conveys the waste toner along the rotary shaft  25   a  in the upper right direction, during rotation. 
     The direction in which the waste toner is conveyed by the first conveying units  23  and  24  is arbitrary. The conveying direction is preferably parallel to at least one of the arrangement direction of the receiving ports  26   a ,  26   b ,  26   c , and  26   d  and the arrangement direction of the receiving ports  27   a ,  27   b ,  27   c , and  27   d . The recovery container  20  may include only one first conveying unit. 
     Next, the operation of the waste toner conveying pipe  130  when the recovery container  20  is mounted on the image forming apparatus main body  100   a , will be described. 
       FIG. 6  is a cross-sectional view showing a configuration of the waste toner conveying pipe  130  before the recovery container  20  is mounted on the image forming apparatus main body  100   a , in the embodiment of the present invention.  FIG. 7  is a cross-sectional view showing a configuration of the waste toner conveying pipe  130  after the recovery container  20  according to the embodiment of the present invention is mounted on the image forming apparatus main body  100   a . In  FIG. 6  and  FIG. 7 , the waste toner conveying pipe  130  corresponds to each of the waste toner conveying pipes  120   a ,  120   b ,  120   c ,  120   d ,  121   a ,  121   b ,  121   c ,  121   d , and  122 . In addition, what corresponds to each of the receiving ports  26   a ,  26   b ,  26   c ,  26   d ,  27   a ,  27   b ,  27   c ,  27   d , and  28  a is shown as the receiving port  35 . 
     Referring to  FIG. 6 , waste toner conveying pipe  130  is a member on the image forming apparatus main body  100   a  side, and includes a pipe main body  131 , a conveying screw  132 , a shutter  133 , a projecting portion  134 , and the like. The pipe main body  131  has a hollow cylindrical shape and projects linearly toward the front of the image forming apparatus  100  (left direction in  FIG. 6 ) from a member serving as a source of waste toner. The pipe main body  131  has a distal end portion  131   a  provided at the distal end portion thereof and a discharge port  131   b  opened at the lower portion of the distal end portion  131   a . The distal end portion  131   a  has a smaller diameter than other portions of the pipe main body  131 . The discharge port  131   b  is an opening for discharging the waste toner carried by the waste toner conveying pipe  130 . 
     The conveying screw  132  is provided inside the pipe main body  131 . The conveying screw  132  is driven to rotate under the control of the control unit  50  and conveys the waste toner along the pipe main body  131 . The conveying screw  132  is rotatably supported by a supporting portion provided on the distal end side of the distal end portion  131   a.    
     The shutter  133  has a cylindrical shape and is attached to the outer periphery of the distal end portion  131   a . The shutter  133  has an outer shape that is substantially the same as the inner diameter of the receiving port  35 . The shutter  133  is slidable along the outer periphery of the distal end portion  131   a . The shutter  133  is urged forward (toward the left in  FIG. 6 ) of the waste toner conveying pipe  130  by an urging member (not shown). When the recovery container  20  is not attached to the image forming apparatus main body  100   a , the shutter  133  covers the discharge port  131   b , and the discharge port  131   b  is in a closed state. 
     The projecting portion  134  is provided at the lower portion of the shutter  133  on the outer periphery of the shutter  133 . The projecting portion  134  protrudes to the outer diameter side from the outer periphery of the shutter  133 . 
     With reference to  FIG. 7 , the recovery container  20  is attached to the image forming apparatus main body  100   a . Then, the projecting portion  134  is pushed to rearward (rightward in  FIG. 6 ) of the image forming apparatus  100 , by the rear side wall  22   c  of the lower portion of the receiving port  35 . As a result, the shutter  133  slides to the rear of the image forming apparatus  100 , and the discharge port  131   b  is opened. The waste toner conveyed by the conveying screw  132  is discharged into the casing  21  through the discharge port  131   b.    
     It is to be noted that the distal end portion  131   a  of the waste toner conveying pipe  122  extends further forward beyond the distal end portion  131   a  of the other waste toner conveying pipes. When the recovery container  20  is attached to the image forming apparatus main body  100   a , the distal end portion  131   a  of the waste toner conveying pipe  122  passes through both of the receiving ports  28   a  and  28   b , and the discharge port  131   b  reaches the inside of the conveying pipe  29 . 
     Next, the operation of the image forming apparatus  100  according to the present embodiment will be described. 
       FIG. 8  is a perspective view showing a method of transmitting the driving force between the driving unit  120  and the drive transmission unit  23   b , according to the embodiment of the present invention. 
     Referring to  FIG. 8 , image forming apparatus  100  further includes a driving unit  120 . The driving unit  120  is, for example, a drive shaft of the motor, and is supplied with electric power under the control of the control unit  50  and rotates. Each of the driving unit  120  and the drive transmission unit  23   b  is in a disk shape, and a belt is provided on the outer periphery thereof. The belt of the driving unit  120  and the belt of the drive transmission unit  23   b  are in contact with each other, and the driving force is transmitted from the driving unit  120  to the drive transmission unit  23   b  by the frictional force therebetween, so that the first conveying unit  23  rotates. 
     The driving unit  120  and the drive transmission unit  23   b  may transmit the driving force from the driving unit  120  to the drive transmission unit  23   b , by meshing engagement of the rotating gears. 
     The method of transmitting the driving force between the driving unit  120  and the drive transmission unit  24   b  is also the same as the method of transmitting the driving force between the driving unit  120  and the drive transmission unit  23   b . The method of transmitting the driving force between the driving part  120  and the drive transmitting part  25   b  is also the same as the method of transmitting the driving force between the driving part  120  and the drive transmitting part  23   b . The explanation will not be repeated. 
       FIG. 9  is a diagram schematically showing the movement of the waste toner in the recovery container  20 , according to the embodiment of the present invention. 
     With reference to  FIG. 2  and  FIG. 9 , the waste toner is conveyed by each of the waste toner conveying pipes  121   a ,  120   a , and  121   b  existing on the left side of the image forming unit  80 . The carried waste toner is discharged into the recovery container  20  through the receiving ports  27   a ,  26   a , and  27   b , respectively. The waste toner falls due to its own weight as indicated by an arrow AR 1  and then is conveyed as indicated by an arrow AR 2  by the blade portions  23   c  and  24   c , and is housed in the accommodating unit SP. 
     The waste toner conveying pipes  120   b ,  121   c ,  120   c ,  121   d , and  120   d  exist in the central portion and the right side of the image forming unit  80 . The carried waste toner is discharged into the recovery container  20  through the respective receiving ports  26   b ,  27   c ,  26   c ,  27   d , and  26   d , falls due to its own weight as indicated by an arrow AR 3 , and is housed in the accommodating unit SP. 
     The waste toner conveyed by the waste toner conveying pipe  122  at the bottom of the image forming unit is discharged into the conveying pipe  29  through the receiving ports  28   a  and  28   b . The waste toner is conveyed to the downstream end portion (right end portion) of the second conveying unit  25  by the blade portion  25   c  as indicated by an arrow AR 4 . The waste toner conveyed by the second conveying unit  25  falls from the downstream end portion of the second conveying unit  25  due to its own weight, as indicated by an arrow AR 5  and is accommodated in the accommodating unit SP. 
     When the amount of waste toner in the recovery container  20  increases, the position of the upper surface of the waste toner accommodated in the accommodating unit SP rises and reaches the first conveying unit  23  or  24 . The blade portion  23   c  of the first transport portion  23  and the blade portion  24   c  of the first transport portion  24  transport the waste toner which reached the first conveying unit  23  or  24  to the positions of the rod portions  23   d  and  24   d  as indicated by the arrow AR 2  on the left side in the accommodating unit SP. The blade portion  23   e  of the first transport portion  23  and the blade portion  24   e  of the first transport portion  24  transport the waste toner which reached the first conveying unit  23  or  24  to the positions of the rod portions  23   d  and  24   d  as indicated by the arrow AR 6  on the right side in the accommodating unit SP. As a result, the height of the upper surface of the waste toner accommodated in the accommodating unit SP is equalized (leveled). 
     When the amount of waste toner in the recovery container  20  further increases, the position of the upper surface of the waste toner stored in the accommodating unit SP exceeds the first conveying units  23  and  24  and reaches the detection window  30 . The control unit  50  detects the waste toner having reached the detection window  30  by the following method. 
       FIG. 10  is a cross-sectional view schematically showing a configuration in the vicinity of the sensor  126  in the embodiment of the present invention. 
     Referring to  FIG. 10 , the detection window  30  has a rectangular shape when viewed from the rear side of the recovery container  20 . The detection window  30  includes a projecting portion  30   a  protruding rearward from the rear side wall  22   c  and a transmission window  30   b  surrounded by the projecting portion  30   a.    
     The sensor  126  (an example of a detection unit) detects the waste toner stored in the casing  21  at the detection window  30 . The sensor  126  is attached to the image forming apparatus main body  100   a . The sensor  126  irradiates light such as infrared rays forward as indicated by an arrow IF, receives the reflected light, and outputs information indicative of the received light amount to the control unit  50 . 
     A positioning portion  125  protruding forward (in the direction of the recovery container  20 ) is provided at the upper and lower portions of the sensor  126 . When the recovery container  20  is attached to the correct position of the image forming apparatus main body  100   a , the positioning unit  125  sandwiches the detection window  30  by the upper side and the lower side. As a result, the positioning portion  125  guides the recovery container  20  so as to be mounted at the correct position. 
     Each of the image forming apparatus main body  100   a  and the recovery container  20  may include an engaging portion that engages with each other when the recovery container  20  is attached to the image forming apparatus main body  100   a.    
     In a state in which the recovery container  20  is attached to the image forming apparatus main body  100   a , the light from the sensor  126  passes through the transmission window  30   b  and is irradiated inside the recovery container  20 . When the waste toner contained in the recovery container  20  reaches the detection window  30 , the amount of light received by the sensor  126  increases and exceeds a predetermined threshold. 
     When the amount of light received by the sensor  126  exceeds a predetermined threshold value, the control unit  50  determines that the recovery container  20  is full of waste toner. At this time, the control unit  50  displays (notifies) the operation panel  52  to request discarding of the waste toner in the recovery container  20 . The user who saw this display, opens the door  56 , takes out the recovery container  20  from the image forming apparatus main body  100   a , discards the waste toner in the recovery container  20 , and reattaches the recovery container  20  to the image forming apparatus main body  100   a.    
     [Effect of Embodiment] 
     According to the present embodiment, the recovery container is provided in front of the image forming unit, and the waste toner discharged from the image forming unit is conveyed to the recovery container, without passing through the rear portion and the side portion of the image forming unit. Therefore, the conveying path of the waste toner can be simplified. As a result, it is possible to reduce the size of the image forming apparatus, and it is possible to reduce the manufacturing cost of the image forming apparatus. In addition, the recovery container is provided above the conveying path for conveying the sheet. Therefore, when the user accesses the conveying path from the front of the image forming apparatus, the recovery container becomes unlikely to be an obstacle, and the operability in performing the jam recovering can be ensured. 
     Further, the waste toner from the intermediate transfer belt discharged into the recovery container is conveyed upward by the second conveying unit. The upper surface of the waste toner accommodated in the accommodating unit of the recovery container is leveled by the first conveying unit. When the upper surface of the waste toner reaches the upper part than the first conveying part, the full of the waste toner is detected. Thereby, it is possible to avoid a situation in which the full of the recovery container is detected in a state where there is an extra space in the recovery container, and the capacity of the recovery container can be effectively utilized. 
     According to the present embodiment, it is possible to provide an image forming apparatus capable of downsizing. 
     [Others] 
     In the above embodiment, the case where the image forming apparatus includes an intermediate transfer belt having an inverted triangular shape has been described. In order to miniaturize the image forming apparatus, the image forming apparatus may include a transfer belt having a structure folded back by a folding roller. In particular, when the image forming apparatus includes a folding roller between the secondary transfer section and the tension roller, it is necessary to arrange the cleaning apparatus of the transfer belt between the secondary transfer section and the folding roller. Therefore, a difference in height between the cleaning device of the transfer belt and the waste toner conveying unit of the image forming unit is liable to occur. For this reason, it is difficult to increase the capacity of the recovery container mounted on the front side of the apparatus, and the merit of the present invention is increased. 
     The first conveying unit and the second conveying unit may be made of a screw having a central axis as in the above embodiment, or may be made of a coil shaped member having no central axis. The first conveying unit and the second conveying unit may be formed of a belt-like member. 
     Although the present invention has been described and illustrated in detail, the disclosed embodiments are made for purposes of illustrated and example only and not limitation. The scope of the present invention being interpreted by terms of the appended claims.