Patent Publication Number: US-7899345-B2

Title: Waste toner collecting device and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the priority from U.S. Provisional Application No. 60/972,225 filed on Sep. 13, 2007, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an image forming apparatus of an electrophotographic system that superimposes toners of plural colors to obtain a color image, and, more particular to an image forming apparatus including a waste toner collecting device that collects a used waste toner. 
     BACKGROUND 
     In general, in an image forming apparatus of an electrophotographic system, plural photoconductive drums are arranged in parallel and toner images of plural colors formed on the respective photoconductive drums are multiply transferred onto a sheet to obtain a color image. In such an image forming apparatus, a residual toner remains on each of the photoconductive drums. When an intermediate transfer belt is used, a residual toner also remains on the intermediate transfer belt. 
     Therefore, the residual toners remaining on the plural photoconductive drums and the intermediate transfer belt are removed by cleaning devices such as blades. The removed residual toners (waste toners) are collected in a waste toner box. 
     In the waste toner box in the past, when the waste toner box is filled with the waste toner, it is detected by an optical sensor that the waste toner box is full. The waste toner box is replaced with a new waste toner box. The waste toner falls from a collection port of the box and piles up below the collection port in a mountain shape. The height of the waste toner in the box is the largest in a portion where the waste toner piles up in the mountain shape. Therefore, the sensor is set in a position where the sensor can detect, before the mountain-like portion reaches the collection port, that the box is filled with the waste toner. 
     JP-A-2002-149022 and JP-A-2002-149023 disclose image forming apparatuses including waste toner containers. 
     In some image forming apparatus, a system for performing development while replacing a carrier little by little is adopted. The mountain shape of the waste toner formed in the box is different depending on the content of the carrier in the waste toner. The mountain shape is also different depending on an amount of the waste toner. Therefore, even if the sensor detects that the box is full, an amount of the waste toner in the box may fluctuate. 
     SUMMARY 
     It is an object of the present invention to provide a waste toner collecting device and an image forming apparatus adapted to stabilize a shape of a waste toner that piles up in a waste toner box. 
     According to an aspect of the present invention, there is provided a waste toner collecting device that collects a waste toner unnecessary in image formation, the waste toner collecting device including a box that stores the waste toner, a collection port that is provided in an upper part of a main body of the box, receives the waste toner, and drops the waste toner into the box, a triangular obstacle provided in a position opposed to a falling port for the waste toner and near a bottom surface in the box, and a sensor that is provided in a position lower than the collection port and higher than the obstacle and detects that an amount of the waste toner stored in the box reaches a predetermined amount. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing an image forming apparatus according to an embodiment; 
         FIG. 2  is a diagram showing the internal structure of the image forming apparatus; 
         FIG. 3  is a perspective view showing a waste toner collecting device according to the embodiment; 
         FIGS. 4A and 4B  are perspective views of a waste toner box used in the waste toner collecting device; 
         FIG. 5  is a front view of the waste toner box used in the waste toner collecting device; 
         FIGS. 6A and 6B  are a perspective view and a sectional view for explaining an arrangement of a sensor in the waste toner collecting device; 
         FIGS. 7A and 7B  are front views for explaining a setting position of an obstacle and an attaching position of a sensor in the waste toner box; 
         FIGS. 8A and 8B  are front views showing deposit states of a waste toner deposited when the obstacle is not provided in the waste toner box; and 
         FIGS. 9A and 9B  are front views showing a deposit state of the waste toner deposited when the obstacle is provided in the waste toner box. 
     
    
    
     DETAILED DESCRIPTION 
     Throughout this description, the embodiment and example shown should be considered exemplars, rather than limitations on the apparatus of the present invention. 
     An embodiment of the present invention is explained in detail below with reference to the accompanying drawings. In the figures, the same components are denoted by the same reference numerals and signs. 
       FIG. 1  is a diagram showing an image forming apparatus according to the embodiment. In  FIG. 1 , reference numeral  100  denotes the image forming apparatus. The image forming apparatus is, for example, an MFP (multi-function peripheral) as a complex machine, a printer, or a copying machine. In the following explanation, an MFP is explained as an example of the image forming apparatus  100 . 
     A document table (not shown) is provided in an upper part of a main body  11  of the MFP  100 . An automatic document feeder (ADF)  12  is openably and closably provided on the document table. An operation panel  13  is provided in an upper part of the main body  11 . The operation panel  13  has an operation unit  14  including various keys and a display unit  15  of a touch panel type. 
     A scanner unit  16  is provided below the ADF  12  in the main body  11 . The scanner unit  16  scans an original document fed by the ADF  12  or an original document placed on the document table and generates image data. A printer unit  17  is provided in the center in the main body  11 . Plural cassettes  18  that store sheets of various sizes are provided in a lower part of the main body  11 . 
     The printer unit  17  includes photoconductive drums and a laser (details of which are described later). The printer unit  17  processes the image data scanned by the scanner unit  16  and image data created by a PC (personal computer) or the like and forms an image on a sheet. 
     The sheet having the image formed thereon by the printer unit  17  is discharged to a paper discharge unit  40 . The printer unit  17  includes, for example, a color laser printer of a tandem system. The printer unit  17  scans a photoconductive member with a laser beam from a laser exposing device  19  and generates an image. 
     The printer unit  17  includes image forming units  20 Y,  20 M,  20 C, and  20 K for respective colors of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units  20 Y,  20 M,  20 C, and  20 K are arranged in parallel below an intermediate transfer belt  21  from an upstream side to a downstream side. 
     In the following explanation, since the image forming units  20 Y,  20 M,  20 C, and  20 K have the same configuration, the image forming unit  20 Y is explained below as a representative image forming unit. The structure of details of the image forming units  20 Y,  20 M,  20 C, and  20 K is shown in  FIG. 2  in enlargement. 
     As it is seen from  FIG. 2 , the image forming unit  20 Y has a photoconductive drum  22 Y as an image bearing member. An electrifying charger  23 Y, a developing device  24 Y, a primary transfer roller  25 Y, a cleaner  26 Y, a blade  27 Y, and the like are arranged around the photoconductive drum  22 Y along a rotating direction t of the photoconductive drum  22 Y. A yellow laser beam from the laser exposing device  19  is irradiated on an exposing position of the photoconductive drum  22 Y to form a latent image on the photoconductive drum  22 Y. 
     The electrifying charger  23 Y of the image forming unit  20 Y uniformly charges the surface of the photoconductive drum  22 Y. The developing device  24 Y supplies a two-component developer including a yellow toner and a carrier to the photoconductive drum  22 Y using a developing roller  24   a  to which a developing bias is applied. The cleaner  26 Y removes a residual toner on the surface of the photoconductive drum  22 Y using the blade  27 Y. 
     Toner cartridges  28  ( FIG. 1 ) that supply toners to the developing devices  24 Y to  24 K are provided above the image forming units  20 Y to  20 K. The toner cartridges  28  include toner cartridges for the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). 
     The intermediate transfer belt  21  circulatingly moves. For example, semi-conductive polyimide is used for the intermediate transfer belt  21  from the viewpoint of heat resistance and abrasion resistance. The intermediate transfer belt  21  is looped around a driving roller  31  and driven rollers  32  and  33  and is opposed to and in contact with photoconductive drums  22 Y to  22 K. A primary transfer voltage is applied to a position of the intermediate transfer belt  21  opposed to the photoconductive drum  22 Y by the primary transfer roller  25 Y to primarily transfer a toner image on the photoconductive drum  22 Y onto the intermediate transfer belt  21 . 
     A secondary transfer roller  34  is arranged to be opposed to the driving roller  31  around which the intermediate transfer belt  21  is looped. When a sheet S passes between the driving roller  31  and the secondary transfer roller  34 , a secondary transfer voltage is applied to the sheet S by the secondary transfer roller  34  to secondarily transfer the toner image on the intermediate transfer belt  21  onto the sheet S. A belt cleaner  35  is provided near the driven roller  33  of the intermediate transfer belt  21 . 
     On the other hand, the laser exposing device  19  scans a laser beam emitted from a semiconductor laser element in an axial direction of the photoconductive drum  22 . The laser exposing device  19  includes a polygon mirror  19   a , a focusing lens system  19   b , and a mirror  19   c.    
     As shown in  FIG. 1 , a separation roller  36  that extracts the sheet S in the paper feeding cassette  18 , conveying rollers  37 , and registration rollers  38  are provided between the paper feeding cassettes  18  and the secondary transfer roller  34 . A fixing device  39  is provided downstream of the secondary transfer roller  34 . 
     The paper discharging unit  40  is provided downstream of the fixing device  39 . A reversal conveying path  41  is also provided. The reversal conveying path  41  reverses the sheet S and guides the sheet S in a direction of the secondary transfer roller  34 . The reversal conveying path  41  is used when duplex printing is performed. Since the reversal conveying path  41  is not the point of the present invention, detailed explanation thereof is omitted. 
     In order to collect residual toners on the respective photoconductive drums  22 Y,  22 M,  22 C, and  22 K and a residual toner on the intermediate transfer belt  21 , a waste toner box  50  is provided. Details of a waste toner collecting device including the waste toner box  50  are described later. 
     Operations of the image forming apparatus  100  shown in  FIGS. 1 and 2  are explained. When image data is inputted from the scanner  16 , the PC, or the like, images are sequentially formed by the image forming units  20 Y to  20 K. 
     The image forming unit  20 Y is explained as an example. A laser beam corresponding to image data of yellow (Y) is irradiated on the photoconductive drum  22 Y and an electrostatic latent image is formed thereon. A yellow (Y) toner image is formed on the photoconductive drum  22 Y by the developing device  24 Y. Subsequently, the photoconductive drum  22 Y comes into contact with the rotating intermediate transfer belt  21  and primarily transfers the yellow (Y) toner image onto the intermediate transfer belt  21  using the primary transfer roller  25 Y. 
     In the same manner as the yellow (Y) toner image forming process, magenta (M), cyan (C), and black (K) toner images are formed by the image forming units  20 M to  20 K. The toner images are sequentially transferred onto an identical position where the yellow (Y) toner image is present on the intermediate transfer belt  21 . In this way, the yellow (Y), magenta (M), cyan (C), and black (K) toner images are multiply transferred onto the intermediate transfer belt  21  to obtain a full-color toner image. 
     The intermediate transfer belt  21  secondarily transfers the full-color toner image onto the sheet S collectively using a transfer bias of the secondary transfer roller  34 . In synchronization with the full-color toner image on the intermediate transfer belt  21  reaching the secondary transfer roller  34 , the sheet S is fed from the paper feeding cassettes  18  to the secondary transfer roller  34 . The sheet S having the toner image secondarily transferred thereon reaches the fixing device  39  and the toner image is fixed on the sheet S. The sheet S having the toner image fixed thereon is discharged to the paper discharging unit  40 . 
     On the other hand, after the secondary transfer is finished, a residual toner on the intermediate transfer belt  21  is cleaned by the belt cleaner  35 . After the toner image is primarily transferred onto the intermediate transfer belt  21 , residual toners on the photoconductive drums  22 Y to  22 K are removed by cleaners  26 Y to  26 K and blades  27 Y to  27 K. The photoconductive drums  22 Y to  22 K are prepared for the next image formation. 
     A waste toner collecting device according to the embodiment of the present invention is explained. 
       FIG. 3  is a perspective view showing a configuration of a main part of the waste toner collecting device. In  FIG. 3 , residual toners on the photoconductive drums  22 Y to  22 K are removed by the cleaners  26 Y to  26 K and the blades  27 Y to  27 K ( FIG. 2 ). A residual toner on the intermediate transfer belt  21  is removed by the belt cleaner  35 . The removed waste toners are stored in the waste toner box  50  via carrying paths  42 . 
     The carrying paths  42  are arranged between the cleaners  26 Y to  26 K and the waste toner box  50  and between the belt cleaner  35  and the waste toner box  50 . 
     The waste toner box  50  (which may be referred to as box  50  below) includes a cubic main body  51  that stores a waste toner, a collection port  52  for collecting a waste toner from the carrying paths  42 , and a sensor  53  (FIG.  4 B) that detects that the waste toner box  50  is full. 
       FIGS. 4A and 4B  are perspective views of the box  50  viewed from different angles.  FIG. 4A  is a perspective view of the box  50  viewed from an angle same as that in  FIG. 3 .  FIG. 4B  is a perspective view of the box  50  viewed from the back. In the following explanation, it is assumed that a side shown in  FIG. 4A  is a front side of the box  50  and a side shown in  FIG. 4B  is a rear side of the box  50 . 
     As shown in  FIGS. 4A and 4B , the collection port  52  of the box  50  is provided in a position offset on one side in an upper part of the main body  51 . A handle  54  is provided on the opposite side of the collection port  52 . An obstacle is formed in a position to which a waste toner falls in a lower part of the box  50 . This obstacle is preferably triangular but may be circular. In this embodiment, a hole  55  of a tunnel shape, which pierces from the front side to the rear side of the main body  51 , is formed in a lower part of the box  50 . The hole  55  is triangular and formed in the position to which the waste toner falls. An oblique side of the triangle corresponds to a falling port for the waste toner. The triangular hole  55  serves as a first obstacle when the waste toner falls. The hole  55  is hereinafter referred to as obstacle  55 . 
     In a position diagonal to the triangular obstacle  55  of the main body  51 , a long hole  56  piercing from the front side to the rear side is formed. The long hole  56  serves as a second obstacle when the waste toner falls. 
     As shown in  FIG. 4B , the sensor  53  that detects that the box  50  is full is attached to the rear side of the main body  51 . The sensor  53  is attached to a hollow projection  57  protruding from the main body  51  by an attaching member  60 . The projection  57  is formed in a position close to the long hole  56  and lower than the collection port  52  and higher than the triangular obstacle  55 . The projection  57  is provided in the vertical direction substantially parallel to the long hole  56 . The projection  57  configures a sensor attaching section. 
     A cap  58  is detachably attached to a side of the main body  51 . The cap  58  is removed and used for closing the collection port  52  when the waste toner box  50  is replaced with a new one. The cap  58  can prevent the waste toner from spilling. 
       FIG. 5  is a front view of the waste toner box  50  viewed from the front side. A waste toner carried from the carrying paths  42  is received by the collection port  52 . As indicated by a dotted line in  FIG. 5 , the waste toner falls from a falling port  52   a  toward an inclined surface of the triangular obstacle  55 . 
       FIG. 6A  is a perspective view showing the sensor  53  attached to the projection  57 . The projection  57  protrudes in a U shape from the main body  51  and formed in the vertical direction. The sensor  53  detects a waste toner accumulated in the projection  57 . The sensor  53  includes a first sensor  531  that detects that the box  50  is full and a second sensor  532  that detects a state of the box  50  before becoming full (near full). The sensor  532  that detects the near full is attached to a position lower than the full detection sensor  531 . 
     The sensors  531  and  532  are, for example, optical sensors including a pair of a light-emitting element and a light-receiving element. As shown in  FIG. 6B , the light-emitting element and the light-receiving element are attached to be opposed to each other across the projection  57 . 
     In a state in which there is only a small amount of a waste toner  59  in the projection  57 , light from the light-emitting element is transmitted through the projection  57  and reaches the light-receiving element. However, when the projection  57  is filled with the waste toner  59 , the light from the light-emitting element does not reach the light-receiving element due to the waste toner. Therefore, it is possible to detect the full or the near full on the basis of a result of the detection in the light-receiving element. In  FIGS. 6A and 6B , the attaching member  60  ( FIG. 4B ) is not shown. 
     A position where the triangular obstacle  55  is formed and an attaching position of the sensor  531  are explained with reference to  FIGS. 7A and 7B . 
       FIG. 7A  shows distances and an angle set in determining a position of the obstacle  55 . An angle A is an angle of the inclined surface with respect to the base of the triangular obstacle  55 . A distance B is a distance from the center of the inclined surface to a bottom surface of the main body  51 . A distance C is a distance between the center point of the waste toner falling port  52   a  and the center point of the inclined surface. 
     When a position of the obstacle  55  was determined, deposit states of a waste toner were measured by changing the angle A and distances B and C. Deposit states of the waste toner were also measured by changing the content of a carrier included in the waste toner. 
     According to several experiments performed, a deposit state (a mountain shape) of the waste toner is stabilized when the angle A is about 30 degrees with respect to the bottom surface of the main body  51 . Concerning the distance B, the deposit state of the waste toner is more stabilized when the obstacle  55  is in a position close to the bottom surface of the main body  51  than in a position close to the collection port  52 . The deposit state of the waste toner is more stabilized when the center of the inclined surface of the obstacle  55  is in a position of the distance C slightly away from the center of the waste toner falling port  52   a  than when the waste toner is dropped to the center of the inclined surface of the obstacle  55 . 
       FIG. 7B  shows distances set in determining a position of the sensor  531 . A distance D is a distance from the sensor  531  to the bottom surface of the main body  51  (height). A distance E is a distance from a perpendicular line of the waste toner falling port to the sensor  531 . 
     It is meaningless to provide the sensor  531  in an excessively low position. The full of the box  50  cannot be detected when the sensor  531  is provided in an excessively high position. Therefore, a height position where the sensor  531  is set (the distance D) is set in a position slightly lower than the top of the long hole  56  on the basis of a deposit state of the waste toner. Concerning the distance E, the perpendicular line is suitably in a position between the long hole  56  and the side of the main body  51 . 
     An example of an experiment result is explained below. 
     Dotted lines  59  in  FIGS. 8A and 8B  indicate a deposit state of the waste toner deposited when the triangular obstacle  55  is not provided. In  FIG. 8A , the content of the carrier included in the waste toner is small. In  FIG. 8B , the content of the carrier included in the waste toner is large. 
     As it is seen from  FIGS. 8A and 8B , when the obstacle  55  is not provided, a mountain shape of the waste toner  59  is different depending on the content of the carrier. When the content of the carrier is small, the mountain shape is relatively gentle. As the content of the carrier increases, the waste toner is deposited high in a portion right below the falling port  52   a . Therefore, the detection of the full of the box  50  by the sensor  53  changes according to the content of the carrier. 
     On the other hand,  FIGS. 9A and 9B  show a deposit state of the waste toner deposited when the triangular obstacle  55  is provided. A dotted lines  59  in  FIG. 9A  indicates a state in which the content of the carrier included in the waste toner is small. A dotted lines  59  in  FIG. 9B  indicates a state in which the content of the carrier included in the waste toner is large. 
     It is seen from  FIGS. 9A and 9B  that, when the obstacle  55  is provided, the waste toner  59  is deposited substantially the same shapes regardless of whether the content of the carrier is large or small. Therefore, the sensor  53  can stably detect the full of the box  55 . 
     When the triangular obstacle  55  is formed in the box  50 , a base of a mountain of the waste toner is formed by the obstacle  55  in an initial stage when the waste toner in the box  50  is little. In the initial stage, since the waste toner slips down on the inclined surface of the obstacle  55 , the waste toner does not pile up high on the obstacle  55  and the mountain of the waste toner is prevented from piling up too high. Therefore, when the box  50  is full, a similar mountain shape of the waste toner is formed. 
     When the waste toner in the box  50  gradually increases to be higher than the long hole  56 , the waste toner that crosses over the long hole  56  deposits in the projection  57 . The sensor  532  detects the near full and, then, the sensor  531  detects the full. 
     The near-full detection sensor  532  is used to notify a user that the box  50  is nearly full and urge the user to prepare the box  50  for replacement. 
     As described above, according to the embodiment of the present invention, it is possible to form the waste toner deposited in the box  50  substantially the same shape regardless of the content of the carrier and stabilize detection of the full by the sensor  531 . 
     When the hole  55  and the long hole  56  are too large, an amount of the waste toner that can be stored in the box  50  decreases. Therefore, it is undesirable to form the hole  55  and the long hole  56  too large. 
     The present invention is not limited to the embodiment described above. Various modifications of the embodiment are possible. For example, the first obstacle  55  is not limited to the hole  55  of a tunnel shape and may be a triangular bridge that connects the front surface and the rear surface of the main body  51 . Similarly, the second obstacle is not limited to the long hole  56  and may be a bridge that connects the front surface and the rear surface of the main body  51 . 
     Although exemplary embodiments are shown and described, it will be apparent to those having ordinary skill in the art that a number of changes, modifications, or alterations as described herein may be made, none of which depart from the spirit. All such changes, modifications, and alterations should therefore be seen as within the scope.