Patent Publication Number: US-7917077-B2

Title: Waste-toner housing device, and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and incorporates by reference the entire contents of Japanese priority document, 2006-277341 filed in Japan on Oct. 11, 2006 and 2007-177437 filed in Japan on Jul. 5, 2007. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a waste-toner housing device for use in an image forming apparatus, and an image forming apparatus. 
     2. Description of the Related Art 
     In conventional image forming apparatuses such as copiers, facsimile machines, and printers, a service staff generally carries out replacement of consumable or life-limited components and maintenance of them. However, the trend is changing and the user is carrying out exchange of supplies and maintenance. In addition, smaller components are used for suppressing the size and the cost of the image forming apparatus. Therefore, the user needs to periodically exchange parts that deteriorate in quality earlier than the life of the apparatus or a waste-toner container. The waste-toner container contains residual materials such as toner, which is a developer, or fiber from transfer sheets. Moreover, because the image forming apparatus is installed adjacent to a user of a personal computer in the times of widespread use of personal computers reduction of noise during operation of the image forming apparatus is another problem that needs attention. 
     Toner that fails to be transferred onto the transfer sheet is removed and conveyed into a waste-toner container. To recycle the waste toner, an additional path and an additional driving unit for collecting the waste toner becomes necessary. As a result, the image forming apparatus becomes larger. The waste toner contains foreign materials such as fiber from the transfer sheets. Removal of the fiber makes control process or reuse process complicated. If a full-color image forming apparatus that uses three or four toners performs the waste-toner recycling process, considerably larger waste-toner container is required so that structure of the full-color image forming apparatus becomes much complicated. For this reason, in some of the image forming apparatuses, the waste toner is just conveyed into the waste-toner container and the waste-toner container is replaced with another one when the waste-toner container is full with the waste toner. 
     It is possible to provide a waste-toner container that can contain all the waste toner generated during a whole life of the apparatus. However, such a waste-toner container is considerably large. Therefore, there is a need for filling the waste toner into the waste-toner container in an effective manner to decrease the frequency of replacing the waste-toner container. The waste toner is poured into the waste-toner container from the top, and a sensor is installed on the top part of the waste-toner container. The sensor is a detecting unit for detecting whether the waste-toner container is filled to its capacity and for notifying time of exchange. Exchange cycle of the waste-toner container is prolonged if the waste-toner container is filled with the waste toner without an unfilled space, that is, the waste toner does not accumulate in one particular part of the waste-toner container. 
     In the conventional image forming apparatus two methods are used to properly fill up the waste-toner container. One method is to periodically shake the waste-toner container and the other method is to locate an agitating screw on the top part of the waste-toner container to flatten a pile of the waste toner inside the waste-toner container. 
     Japanese Patent Application Laid-Open No. H11-258962 discloses an image forming apparatus in which waste toner removed by the cleaning device is mixed with fresh toner supplied to a developing device, and mixed toner is conveyed to an agitating unit. An accumulating unit is formed in front of the mixing unit in the image forming apparatus. In the image forming apparatus the fresh toner is fed to the accumulating unit and the waste toner is returned to the accumulating unit. Japanese Patent Application Laid-Open No. 2004-102137 discloses an image forming apparatus that includes a waste-toner housing device that is shaped able to fit into a spare space in a main body of the image forming apparatus. The waste-toner housing device includes a waste container and a conveying member that conveys collected waste toner within the waste-toner container. 
     However, in the conventional image forming apparatus, collected waste toner is piled up in one part of the waste-toner container, and space in the waste-toner container is not effectively filled. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to at least partially solve the problems in the conventional technology. 
     According to an aspect of the present invention, there is provided a waste-toner housing device detachably attached to an image forming apparatus for housing waste toner generated in the image forming apparatus. The waste-toner housing device includes a waste-toner container; and a first conveying member and a second conveying member that convey the wasted toner. The first conveying member and the second conveying member are arranged inside the waste-toner container in such a manner that the second conveying member is located on an elevated level with respect to the first conveying member. 
     According to another aspect of the present invention, there is provided an image forming apparatus. The image forming apparatus includes the waste-toner housing device described above. 
     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an image forming apparatus according to an embodiment of the present invention; 
         FIG. 2  is a schematic diagram of a waste-toner conveying unit shown in  FIG. 1 ; 
         FIG. 3  is a schematic diagram of a waste-toner housing device and relevant parts shown in  FIG. 1 ; 
         FIGS. 4A and 4B  are schematic diagrams for explaining efficiency of a space for waste toner depending on levels on which waste-toner conveying screws shown in  FIG. 3  are located; 
         FIG. 5  is a schematic diagram of another example of the waste-toner housing device and relevant parts; and 
         FIG. 6  is an overhead view of the waste-toner housing device shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawings. 
       FIG. 1  is a schematic diagram of an image forming apparatus  10  according to an embodiment of the present invention. The image forming apparatus  10  includes four image forming units  20   a ,  20   b ,  20   c , and  20   d  for different colors that are arranged in tandem. 
     The image forming units  20   a ,  20   b ,  20   c , and  20   d  each include a drum-like image carrier  22  ( 22   a ,  22   b ,  22   c ,  22   d ), around which are arranged a charging device  21  ( 21   a ,  21   b ,  21   c ,  21   d ), a developing device  31  ( 31   a ,  31   b ,  31   c ,  31   d ), and a cleaning device  23  ( 23   a ,  23   b ,  23   c ,  23   d ). The charging device  21  uniformly charges the surface of the image carrier  22 . The developing device  31  develops an image with developer, i.e., toner, of one of the colors. The cleaning device  23  removes residual toner from the surface of the image carrier  22  after primary transfer. The image forming unit  20  ( 20   a ,  20   b ,  20   c ,  20   d ) further includes a first waste-toner conveying screw  24  ( 24   a ,  24   b ,  24   c ,  24   d ), a waste-toner conveyor belt  25  ( 25   a ,  25   b ,  25   c ,  25   d ), and a waste-toner housing device  59  ( 59   a ,  59   b ,  59   c ,  59   d ). The first waste-toner conveying screw  24  conveys the residual toner removed by the cleaning device  23  out of the cleaning device  23 . The waste-toner conveyor belt  25  conveys the residual toner to the waste-toner housing device  59 . The image forming unit  20  is detachably attached to the image forming apparatus  10 . The developing device  31  can be built in the image forming unit  20 . The image forming apparatus  10  includes an intermediate transfer belt  28  that extends around a driving roller  27   a , a driven roller  27   b , and a primary transfer roller  29  ( 29   a ,  29   b ,  29   c ,  29   d ). The image carrier  22  is exposed to a laser beam  36  ( 36   a ,  36   b ,  36   c ,  36   d ). 
     The charging device  21  uniformly charges the surface of the image carrier  22  when negative bias charge is applied to each of the charging devices  21 , using a direct current (DC) from other source of bias supply. The image carrier  22   a  of the image forming unit  20   a  is exposed to the laser beam  36   a . The image carrier  22   b  of the image forming unit  20   b  is exposed to the laser beam  36   b . Thus, a periphery of the image carrier  22   a , which is uniformly charged with high voltage charge, is selectively exposed to the laser beam  36   b  based on image data. Low and high voltage areas formed due to the exposure create a latent image. Bias voltage of alternating current (AC) and DC, from a bias supply (not shown), is applied to the center of an image roller  32  of the developing device  31  that creates an electric field. The electric field created on the developing device  31  helps in creating a toner image by developing the latent image. 
     The toner image is carried by the rotating image carrier  22   a , and is transferred onto the intermediate transfer belt  28 . The image forming unit  20   b  operates in the same manner as previously described for the image carrier  22   a  correspondingly to the timing at which the toner image on the intermediate transfer belt  28  comes in contact with the image carrier  22   b . Specifically, the developing device  31   b  develops a latent image formed on the image carrier  22   b  into a toner image, and the toner image on the image carrier  22   b  is transferred onto the intermediate transfer belt  28  such that the toner image is superimposed on the previous one. The same operation is performed by the image forming unit  20   c  and the image forming unit  20   d.    
     After the image is transferred onto the intermediate transfer belt  28 , a cleaning blade in the cleaning device  23  removes residual toner from the surface of the image carrier  22   a . Thus, the next image forming operation can be performed on the image carrier  22   a.    
       FIG. 2  is a schematic diagram of a waste-toner conveying unit for conveying waste toner to the waste-toner housing device  59 . The waste-toner housing device  59  includes a waste-toner container  58  for containing waste toner generated in the image forming apparatus  10 . The waste-toner container  58  is detachably attached to the image forming apparatus  10 , and is shaped able to fit in the spare space within a main body of the image forming apparatus  10 . A second waste-toner conveying screw  50  and a third waste-toner conveying screw  51  that agitate and convey the waste toner are arranged inside the waste-toner container  58 . A surface of the waste-toner container  58  adjacent to components of the image forming apparatus  10  in the attached position is shaped along shapes of the components. For example, if the components are the cleaning devices  23   a ,  23   b ,  23   c , and  23   d  each arranged at an angle, the surface of the waste-toner container  58  is inclined in the same direction as a line that links the cleaning devices  23   a ,  23   b ,  23   c , and  23   d , or is parallel to the line. 
     The waste toner is conveyed by the first waste-toner conveying screw  24  to an outlet portion  41 . The waste toner is held in between protruding portions  43  on the waste-toner conveyor belt  25 , which rotates in a direction of an arrow  42 , and an outer wall  44  of a waste-toner conveying path. Thus, the waste toner is conveyed to a waste-toner inlet portion  53 . 
       FIG. 3  is a schematic diagram of the waste-toner housing device  59  and relevant parts. The waste-toner housing device  59  includes a waste-toner space  54 . Waste toner entered from the waste-toner inlet portion  53  (not shown in  FIG. 3 ) is conveyed by the second waste-toner conveying screw  50  to the waste-toner space  54 . When the waste toner is accumulated in the front (inlet) side of the waste-toner space  54 , the waste toner is conveyed towards the depth side thereof by the second waste-toner conveying screw  50  and the third waste-toner conveying screw  51 . With this configuration, the waste toner can be conveyed to desired areas in a desired order, and the space in the waste-toner container  58  is effectively used. The waste-toner housing device  59  also includes a deformable divider  52  that divides the waste-toner container  58  into a new-toner reservoir and the waste-toner space  54  so that a capacity of the waste-toner space  54  is variable depending on a volume of the waste toner. That is, when new toner is larger in quantity at the initial stage, the capacity of the waste-toner space  54  is small. On the other hand, when waste toner is larger in quantity at the terminal stage, the capacity of the waste-toner space  54  is large. 
     In the waste-toner housing device  59 , the second waste-toner conveying screw  50  and the third waste-toner conveying screw  51  are located on different levels in height in the waste-toner container  58 .  FIGS. 4A and 4B  are schematic diagrams for explaining efficiency of the waste-toner space  54  depending on the levels on which the second waste-toner conveying screw  50  and the third waste-toner conveying screw  51  are located. When both the second waste-toner conveying screw  50  and the third waste-toner conveying screw  51  are located on the same level as shown in  FIG. 4B , an unfilled space SP indicated by a doted line in  FIG. 4B  is created, which undermines the effective use of the space in the waste-toner container  58 . However, as shown in  FIG. 4A , when the second waste-toner conveying screw  50  and the third waste-toner conveying screw  51  are located on different levels, the unfilled space SP is not created. Thus, the space in the waste-toner container  58  is effectively used. 
       FIG. 5  is a schematic diagram of the waste-toner housing device  59  including the deformable divider  52 .  FIG. 6  is an overhead view of the waste-toner housing device  59  shown in  FIG. 5 . As shown in  FIG. 6 , the inside of the waste-toner container  58  is separated into Areas A 1 , A 2 , and A 3 . Area A 3  is closest to the waste-toner inlet portion  53 . Waste toner conveyed by the waste-toner conveyor belt  25  is then conveyed by the second waste-toner conveying screw  50  towards Area A 1 . When Area A 1  is completely filled with waste toner, the third waste-toner conveying screw  51  conveys to Area A 2  or A 3  waste toner that fails to be filled in Area A 1 . To effectively deform a shape of the deformable divider  52 , there is a need for filling the waste toner in the waste-toner container  58  in an order from Area A 1  to A 3 . However, before Area A 1  is completely filled with the waste toner, the waste toner may accumulate in Area A 2  or A 3 . Difference in level of the second waste-toner conveying screw  50  and the third waste-toner conveying screw  51  makes it possible to fill the waste toner in the desirable order from Area A 1  to A 3 . As a result, the space inside the waste-toner container  58  is effectively used. The waste-toner conveying screw extends, from the waste-toner inlet portion, to a point that is located in a range from a one-third to a two-third of a longitudinal length of the waste-toner housing device. This makes it possible to convey the waste toner to Area A 1  shown in  FIG. 6 . As a result, the waste toner first accumulates near the center portion so that the deformable waste-toner space expands around the center portion, that is, the waste-toner space can expand efficiently. The third waste-toner conveying screw  51  extends over one-third of the longitudinal length of the waste-toner housing device  58  at its center portion. This is why the toner accumulating on Area A 1  is conveyed by the third waste-toner conveying screw  51  in the opposite direction to Area A 3 . The waste toner accumulating on Area A 3  swells the waste-toner space efficiently. Consequently, there is no wasteful space in the waste-toner container. 
     The image forming apparatus  10  operates as described below. In the image forming unit  20   a  for black image, the image carrier  22  is charged by the charging device  21   a  and a latent image is formed by the laser beam  36  thereafter. The latent image is developed with black toner by the developing device  31  to form a toner image. The toner image formed on the image carrier  22  is carried by the primary transfer roller  29  and is transferred onto the intermediate transfer belt  28 . A surface of the image carrier  22  is cleaned by the cleaning device  23  after the image is transferred, to prepare the image carrier  22  for the next image forming operation. 
     A transfer sheet P is fed into the image forming apparatus  10  by a paper feed roller  37  and a pair of conveyor rollers  38 . The toner image formed on the intermediate transfer belt  28  is transferred onto the transfer sheet P by a secondary transfer roller  39 . The transfer sheet P with the toner image passes through a fusing unit  60  for fusing the image and is discharged to a catch tray  62  by a pair of discharging rollers  61 . 
     In the image forming apparatus each of toner containers, the intermediate transfer belt  28 , and cartridges are arranged at a tilt and are oriented in the same direction. This allows formation of a compact image forming apparatus. Specifically, the image forming unit  20   a  for black image is located adjacent to a transfer nip. The image forming unit  20   a  is inclined such that the image forming unit  20   a  is lower than the image forming unit  20   d . Because the black-and-white printing operation is performed most frequently even in the full-color printer, such an arrangement shortens the time required for printing a black-and-white image. 
     The image forming apparatus  10  includes the waste-toner housing device  59  for housing the waste toner after the image carrier  22  is cleaned. The waste-toner container  58  is configured to be detachable from the image forming apparatus  10  so that the waste-toner container  58  is appropriately exchanged. 
     When a color image is to be formed in the image forming apparatus  10 , the image forming units  20   b ,  20   c , and  20   d  for yellow, cyan, and magenta perform an identical image forming process performed by the image forming unit  20   a  for black. Thus, toner images for each of the colors are formed, which are then sequentially transferred onto the intermediate transfer belt  28 . The transfer sheet P is fed from a paper feed cassette  11 . The toner image formed on the intermediate transfer belt  28  is transferred by the secondary transfer roller  39  onto the transfer sheet P. The transfer sheet P, with the toner image, passes through the fusing unit  60 . The toner image is fused onto the transfer sheet P in the fusing nip that is formed of a fusing roller and a pressure roller. Thereafter, the transfer sheet P is discharged to the catch tray  62  that is located on the top end surface of the image forming apparatus  10  by the discharging roller  61 , which is located downstream of the transfer-sheet conveying path. The residual toner on the intermediate transfer belt  28  is removed by the cleaning device  23  in a similar manner that the image carrier  22  is cleaned and is conveyed by the waste-toner conveying unit to the waste-toner housing device  59 . 
     In the embodiment described above, an image carrier, a charging device, a developing device, a cleaning device, and a waste-toner housing device are integrally formed into one unit that is detachable from the image forming apparatus. However, the waste-toner housing device can be separately detachable from the image forming apparatus. Only the waste-toner housing device and the image carrier can be formed into one unit, or can be formed into one unit with any one of the charging device, the developing device, and the cleaning device. 
     As set forth hereinabove, according to an embodiment of the present invention, unevenly accumulated waste toner is leveled or smoothed in the waste-toner housing device, so that every part of the waste-toner housing device can be effectively filled with waste toner. Thus, the cycle of exchanging the housing device becomes longer. As a result, frequency of exchanging the waste-toner housing device decreases. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.