Abstract:
An image forming apparatus including an image bearing member that rotates while bearing toner image, a transfer unit including, a transfer member that rotates while contacting to the image bearing member and transfers the toner image on the image bearing member to a recording material, and a toner removing member that rotates while contacting with the transfer member, and collects the toner on the transfer member, a transmission path that transmits drive power for rotating the transfer member and the toner removing member, and a separation/contact unit that rocks the transfer unit and the transmission path integrally around a rotational center of a driving power reception member which is a part of the transmission path and to which the driving power is applied, so that the transfer member is separated from and contacted with the image bearing member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a divisional of Application Ser. No. 11/109,721, filed Apr. 20, 2005. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a residual toner removal apparatus for removing residual toner adhering to a transferring rotary member for transferring a toner image to a transfer material, and an image forming apparatus equipped with the residual toner removal apparatus. 
   2. Related Background Art 
   In conventional image forming apparatuses, there is known an image forming apparatus in which a transfer material (e.g., a sheet) is held between an intermediate transferring member having a toner image formed thereon through primary transferring, and a secondary transferring member capable of being brought into and out of contact with the intermediate transferring member, and secondary transferring of the toner image on the intermediate transferring member to the transfer material is effected (see Japanese Patent Application Laid-Open No. 11-52757).  FIG. 9  is a perspective view of a secondary transferring roller pushing mechanism of the image forming apparatus.  FIG. 10  is a front view of a main portion of an image transferring apparatus. 
   A shaft  109   a  of a secondary transferring roller  109  as a secondary transferring rotary member is rotatably supported at one end of each of arms  137  adapted to rock around rotation shafts  136 . The secondary transferring roller  109  rotates integrally with a driven gear  132  coaxial with the shaft  109   a . The arms  137  are biased so as to rotate clockwise as seen in the drawing by a spring  138  provided at the other end of one of the arms  137 . The secondary transferring roller  109  is pushed against a transfer belt  107  as an intermediate transferring member by the pulling force of the spring  138 . The rotation shafts  136  of the arms  137  are shafts common to a shaft  134  of a driving gear  131  or are at least arranged coaxially therewith. At the other end of one of the arms  137 , an eccentric cam  139  is arranged so as to be opposed to the arm. The arm  137  is pushed against the cam surface of the eccentric cam  139  by the pulling force of the spring  138 . 
   In this construction, when a flat portion  139   a  of the eccentric cam  139  is opposed to the arm  137 , the arms  137  are pulled by the spring  138  to rotate clockwise, bringing the secondary transferring roller  109  into press contact with the transfer belt  107 . When, in this state, the driving gear  131  rotates, the secondary transferring roller  109  is caused to rotate through the driven gear  132 . When a transfer material (e.g., a sheet) enters the gap between the rotating secondary transferring roller  109  and the running transfer belt  107 , a toner image on the transfer belt  107  is transferred to the transfer material. 
   When the eccentric cam  139  rotates and its maximum radius portion  139   b  comes into contact with the arm  137 , the arm  137  rotates counterclockwise against the force of the spring  138 , separating the secondary transferring roller  109  from the transfer belt  107 . The driving gear  131  and the driven gear  132  are constantly in mesh with each other regardless of whether the secondary transferring roller  109  is separated from the transfer belt  107  or is contacted with the transfer belt  107 . Residual toner on the transfer belt  107  may adhere to the secondary transferring roller  109 . Thus, when it is at a position where it is in contact with the transfer belt  107 , the secondary transferring roller  109  is also in contact with a cleaning blade  133 , by means of which the residual toner is removed. 
   In some image forming apparatuses, the residual toner adhering to the transfer belt as the intermediate transferring member is removed by electrostatic cleaning (see Japanese Patent Application Laid-Open No. 2001-337542).  FIG. 11  is a schematic front view of a cleaning device  213  of such an image forming apparatus. 
   The cleaning device  213  forms a cleaning area in a part of a portion where an intermediate transfer belt  207 A is in contact with a roller  207 B as an opposing roller. The cleaning device  213  is equipped with a first bias roller  224 , a first fur brush  223  in contact with the first bias roller  224 , a second bias roller  227 , a second fur brush  226  in contact with the second bias roller  227 , a carrying screw  229 , etc. By applying a bias voltage of reverse polarity to the first fur brush  223  and the second fur brush  226 , cleaning of the intermediate transfer belt  207 A is effected. 
   In this way, in the conventional image forming apparatuses, it is possible to remove residual toner adhering to the secondary transferring roller and the transfer belt. However, the residual toner adhering to the secondary transferring roller  109  is mechanically removed by the cleaning blade  133 . Thus, there is a fear of the secondary transferring roller being damaged. Further, the residual toner is removed by the cleaning blade  133  only when the secondary transferring roller  109  is at the position where it is in contact with the transfer belt  107 , resulting in a rather low residual toner removal efficiency. 
   When the residual toner removal efficiency is low, some residual toner is allowed to adhere to the transfer material, which leads to a deterioration in image quality. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a residual toner removal apparatus which is constantly capable of electrostatically removing residual toner adhering to the secondary transferring rotary member. 
   Another object of the present invention is to provide an image forming apparatus equipped with a residual toner removal apparatus constantly effecting electrostatic removal, thereby achieving an improvement in the quality of the image on the transfer material. 
   To attain the above objects, according to the present invention, there is provided an image forming apparatus including an image bearing member, toner image forming device for forming a toner image on the image bearing member, a transferring member for bringing into and out of contact with the image bearing member by rocking operation to electrostatically transfer the toner image on the image bearing member to a transfer material, and a toner removing device for, while the transferring member rocks, electrostatically removing the toner on the transferring member by that a bias is applied. 
   In the residual toner removal apparatus of the present invention, the toner collection rotary member is arranged such that its rotation center coincides with the rotation center of the rotary member, so that even if the toner collection rotary member is rocked using the toner collection rotary member to which a bias voltage of a polarity reverse to that of the residual toner as the fulcrum, it is possible to apply a bias voltage to the toner collection rotary member, making it possible to constantly remove the residual toner. 
   Further, since residual toner is removed electrostatically, it is possible to remove the residual toner with less damage to the toner collection rotary member than in the prior art. 
   Further, since a bias voltage of reverse polarity is applied to the toner collection rotary member that does not move, it is possible to simplify the drive construction for rotating the toner collection rotary member, whereby it is possible to achieve space saving for the image transferring apparatus and to achieve a reduction in cost; this also proves effective in achieving a reduction in the torque required for effecting the rocking movement. 
   The image forming apparatus of the present invention is equipped with the residual toner removal apparatus which constantly removes residual toner electrostatically, whereby it is possible to achieve an improvement in terms of the quality of the image on the transfer material. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic front sectional view of a color laser printer constituting an image forming apparatus according to an embodiment of the present invention; 
       FIG. 2  is a perspective view of a secondary transferring portion as an image transferring apparatus; 
       FIG. 3  is a schematic front view of the secondary transferring portion as an image transferring apparatus; 
       FIG. 4  is a diagram for illustrating how a secondary transferring outer roller is brought into and out of contact with an intermediate transfer belt; 
       FIG. 5  is a diagram showing an electrical construction of a residual toner removal apparatus; 
       FIG. 6  is a perspective view of a high bias voltage application mechanism of an electrostatic roller; 
       FIGS. 7A ,  7 B,  7 C and  7 D are diagrams for illustrating the operation of the residual toner removal apparatus, of which  FIG. 7A  is a diagram showing a state in which residual toner adheres to the secondary transferring outer roller,  FIG. 7B  is a diagram showing a state in which the residual toner is collected by a fur,  FIG. 7C  is a diagram showing a state in which the residual toner is collected by the electrostatic roller, and  FIG. 7D  is a diagram showing a state in which the residual toner is scraped off by a scraping member; 
       FIG. 8  is a front view of a residual toner removal apparatus according to another embodiment; 
       FIG. 9  is a perspective view of a secondary transferring roller pushing mechanism of a conventional image forming apparatus; 
       FIG. 10  is a front view of a main portion of a conventional image transferring apparatus; and 
       FIG. 11  is a schematic front view of a conventional cleaning device. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following a residual toner removal apparatus according to an embodiment of the present invention and an image forming apparatus equipped with this residual toner removal apparatus will be described. 
     FIG. 1  is a sectional view of an image forming apparatus according to an embodiment of the present invention taken along the direction in which a transfer material is conveyed. While in this embodiment the image forming apparatus is a color laser printer (hereinafter simply referred to as the printer)  40 , this should not be construed restrictively. 
   In the printer  40 , toner images of yellow, magenta, cyan, and black are successively formed one by one on a photosensitive drum  1 , which is an image bearing member consisting of a drum-shaped electrophotographic photosensitive member (photosensitive member). The toner images of different colors on the photosensitive drum  1  are repeatedly transferred one by one to an intermediate transfer belt  8  as an intermediate transferring member to thereby form, for example, a full color toner image on the intermediate transfer belt  8 . Thereafter, the full color toner image is collectively transferred to a transfer material by a secondary transferring outer roller  5  as a secondary transferring rotary member, and is then fixed to thereby obtain a permanent image. 
   The printer  40  has the photosensitive drum  1  substantially at its center. When image forming operation is started, the printer  40  charges the surface of the photosensitive drum  1  to a predetermined polarity and a predetermined voltage level by means of a charging roller  2 . 
   Next, a detector  10  detects the beginning position of the image, which is determined by taking into account the transfer position when the toner images on the photosensitive drum  1  are transferred to the intermediate transferring belt  8 . In synchronism with a reference signal (TOP signal) from the detector  10 , exposure scanning is performed on the photosensitive drum  1  with a laser beam L modulated by an image signal (VDO signal), whereby, first, an electrostatic latent image corresponding to the image signal of the first color is formed on the photosensitive drum  1 . At this time, a photo detector  4   e  detects a signal (BD signal) indicating the horizontal exposure scanning start point, whereby exposing in synchronism with the BD signal is effected. 
   Here, an exposing system  4  is composed of a laser unit  4   a  emitting the laser beam L, a polygon mirror  4   b  for effecting horizontal scanning with the laser beam L, a scanner motor  4   c  for rotating the polygon mirror  4   b  at low speed, an fθ lens  4   d  for effecting image formation with the laser beam L, the above-mentioned photo detector  4   e  for detecting the BD signal indicating the horizontal scanning start point, a reflection mirror  4   f  for guiding the laser beam L to the photosensitive drum, and the like. The laser beam L is on/off-modulated by the above-mentioned image signal (VDO signal), which is an input signal of the laser unit  4   a.    
   A rotary type developing member  3  is equipped with developing devices  3 Y,  3 M,  3 C, and  3 Bk respectively containing yellow, magenta, cyan, and black developers. The rotary type developing member  3  rotates with a predetermined Liming, causing the developing devices ( 3 Y,  3 M,  3 C, and  3 Bk) to face the photosensitive drum  1 . First, to develop the electrostatic latent image of the first color, the rotary type developing member  3  rotates and causes the yellow developing device  3 Y to face the photosensitive drum  1 , forming a toner image in the first color, i.e., an yellow toner image, on the photosensitive drum  1 . The photosensitive drum  1  and the rotary type developing member  3  constitute an image forming portion. 
   Thereafter, the yellow toner image on the photosensitive drum  1  is transferred to the intermediate transfer belt  8  by applying a transfer bias voltage of a polarity reverse to that of the toner to the intermediate transfer belt  8 . 
   Similar processes described above are repeatedly conducted for the second, third, and fourth colors, i.e., magenta, cyan, and black, whereby, for example, a full color toner image is transferred to the intermediate transfer belt  8  (primary transferring). 
   Further, with a predetermined timing based on the reference signal (TOP signal) from the detector  10 , a paper feed roller  13  supplies a transfer material P accommodated in a paper feed cassette  12  into the image forming apparatus. 
   The transfer material P is conveyed by conveying rollers  34  to registration rollers  14  for controlling the timing with which the toner image is transferred to the transfer material P, and is temporarily stopped there. Then, in synchronism with the predetermined transfer timing, the transfer material P is sent from the registration rollers  14  into the gap between the intermediate transfer belt  8  and the transfer roller  5  (hereinafter referred to as the “secondary transferring outer roller”). The full color toner image on the intermediate transfer belt  8  is transferred electrostatically and collectively to the transfer material P by the transfer roller  5  (secondary transferring). 
   The transfer material P bearing the unfixed full color toner image is conveyed to a fixing device  6  by a conveying belt unit  16 . The unfixed full color toner image is fused to the transfer material P by the heat and pressure of the fixing device  6  to become a permanent image. Thereafter, the transfer material P is discharged to the exterior of the image forming apparatus  40  by conveying rollers  17  and  18 . 
   Transfer residual toner (residual toner) remaining on the photosensitive drum  1  after the completion of the image transfer (for each color) to the intermediate transfer belt  8 , residual toner remaining on the surface of the intermediate transfer belt  8  after the completion of the transfer of the full color toner image to the transfer material P, or the like is removed by cleaning devices  7  and  11  each having a blade-like cleaning member. As a result, the photosensitive drum  1  and the intermediate transfer belt  8  perform image formation on the transfer material in a clean state. Also, by means of a multi-paper-feed tray  19  and a paper feed roller  15  for the multi-paper-feed tray, a plurality of kinds of transfer material P can be supplied. 
   In the above-described construction, the secondary transferring outer roller  5 , which transfers the toner on the intermediate transfer belt  8  to the transfer material, forms a secondary transferring portion  41  as an image transferring apparatus. 
   Next, a residual toner removal apparatus  47  according to this embodiment will be described with reference to  FIGS. 2 and 3 . The residual toner removal apparatus  47  is mainly composed of a fur brush  22  for collecting toner on the secondary transferring outer roller  5 , which transfers a multi-color toner image to the transfer material through secondary transferring, an electrode member, i.e., an electrostatic roller  20  for collecting toner adhering to the fur brush  22 , a scraping member  21  for scraping off toner adhering to the electrostatic roller  20 , and the like. 
   The secondary transferring outer roller  5 , the fur brush  22 , and the electrostatic roller  20  are supported at both ends by rocking arms  25  and  26  formed as rotary members. The rocking arms  25  and  26  rotate using a shaft  42  of the electrostatic roller  20  as the fulcrum. The rocking arms  25  and  26  are in contact with eccentric cams  29  and  30 . The eccentric cams  29  and  30  are rotated around a shaft  31  by a motor (not shown). Thus, the rocking arms  25  and  26  are rotated by the eccentric cams  29  and  30 , bringing the secondary transferring outer roller  5  to contact with the intermediate transfer belt  8  and to separate from the intermediate transfer belt  8  (in other words, bringing the secondary transferring outer roller  5  into and out of contact with the intermediate transfer belt  8 ). 
   Further, at the ends of the shaft  42  of the electrostatic roller  20 , a transfer driving gear  23  and a fur driving gear  27  are integrally provided. Integrally provided on a shaft  44  of the secondary transferring outer roller  5  is a transfer driven gear  24  which is in mesh with the transfer driving gear  23 . Integrally provided on a shaft  43  of the fur brush  22  is a fur driven gear  28 . The shaft  43  of the fur brush  22  is electrically insulated from the other components, and the fur brush  22  is in an electrically floating state. 
   When the transfer driving gear  23  as the driving rotary member is rotated by a driving motor (not shown), there occurs rotation of the electrostatic roller  20 , the fur driving gear  27 , the transfer driven gear  24  as the driven rotary member in mesh with the transfer driving gear  23 , and the secondary transferring outer roller  5 . The transfer driving gear  23  and the transfer driven gear  24  form a torque transmission rotary member row. It is also possible to provide an idle gear between the transfer driving gear  23  and the transfer driven gear  24 . Further, instead of the gears, it is also possible to use rollers. The fur driven gear  28 , which is in mesh with the fur driving gear  27 , also rotates, causing the fur brush  22  to rotate. Thus, when the electrostatic roller  20  rotates, the secondary transferring roller  5  and the fur brush  22  rotate. 
   When a full color image is to be formed, the secondary transferring outer roller  5  is kept away from the intermediate transfer belt  8  until the unfixed toner image of the final color has been primarily transferred to the intermediate transfer belt  8 . While the unfixed toner image of the final color is being primarily transferred to the intermediate transfer belt  8 , the secondary transferring outer roller  5  comes into contact with the intermediate transfer belt  8 . Then, secondary transferring is effected. 
   Before the secondary transferring outer roller  5  comes into contact with the intermediate transfer belt  8 , the secondary transferring outer roller  5 , the fur brush  22 , and the electrostatic roller  20  rotate for a predetermined period of time. Further, also after the secondary transferring outer roller  5  is separated from the intermediate transfer belt  8 , the secondary transferring outer roller  5 , the fur brush  22 , and the electrostatic roller  20  rotate for a predetermined period of time. Cleaning is effected on the secondary transferring outer roller  5  not only while it is in contact with the intermediate transfer belt  8  but also during the above-mentioned rotation for a predetermined period of time, thus keeping it in a clean state. 
   Namely, cleaning for the toner adhering on the secondary transferring outer roller  5  is performed, even while the secondary transferring outer roller  5  and the fur brush  22  rock in order that the secondary transferring outer roller  5  contacts with or separates from the intermediate transfer belt  8 . 
   Next, the cleaning operation for removing residual toner adhering to the secondary transferring outer roller  5  will be described. The toner transferred from the photosensitive drum  1  to the intermediate transfer belt  8  is endowed with a certain polarity, and when a bias voltage is applied to the intermediate transfer belt  8 , it is secondarily transferred to the transfer material P electrostatically. In some cases, some toner remains on the intermediate transfer belt  8 . For example, any residual toner on the intermediate transfer belt  8  outside the width in the sub scanning direction of the transfer material P is transferred to the secondary transferring outer roller  5 . This residual toner is a toner of substantially the same polarity. 
   Here, the electrical layout of the secondary transferring portion will be described with reference to  FIG. 5 . First, a bias voltage of a polarity reverse to that of the residual toner on the secondary transferring outer roller  5  is applied to the electrostatic roller  20  serving as the toner collecting rotary member. The fur brush  22  is in an electrically floating state, and the secondary transferring outer roller  5  is grounded. Here, the secondary transferring outer roller  5  rocks using the electrostatic roller  20  as the fulcrum, so that, when high voltage is to be inputted to the electrostatic roller  20 , the high voltage can be easily inputted by a plate spring  33  as shown in  FIG. 6 . The electrostatic roller  20 , the fur brush  22 , and the like constitute a residual toner removing means. 
   Further, an electrical relation among the secondary transferring outer roller  5 , the fur brush  22  and the electrostatic roller  20  in the secondary transferring portion does not change even while the secondary transferring outer roller  5  and the fur brush  22  integrally rock. Namely, during rocking, the secondary transferring outer roller  5  is grounded, and through the electrostatic roller  20  the secondary transferring outer roller  5  and the fur brush  22  are applied by high voltage. 
   The flow of the residual toner adhering to the electrostatic roller  20  is as shown in  FIGS. 7A through 7D . The residual toner adhering to the secondary transferring outer roller  5  is first electrostatically collected by the fur brush  22  ( FIGS. 7A and 7B ). The residual toner is collected from the rotating fur brush  22  by the electrostatic roller  20  ( FIG. 7C ), and is scraped off from the electrostatic roller  20  by a scraping member  21  as the toner removing member ( FIG. 7D ) before being carried by a toner carrying means (not shown). It is also possible for the residual toner to be collected by a toner collecting portion installed substantially below the secondary transferring portion  41 . Here, the scraping member  21  is in contact with the electrostatic roller  20 , so that there is no need for the scraping member  21  itself to rock. Accordingly, it is possible to achieve an improvement in the positional accuracy of the scraping member  21 . Further, the residual toner can be reliably removed. 
   Incidentally, a structure in which the secondary transferring outer roller  5  is made at least one rotation while the secondary transferring outer roller  5  rocks, in order to perform surely cleaning for the toner adhering on the secondary transferring outer roller  5 , can be employed. 
   The present invention is not restricted to the above construction. For example, as in the case of a residual toner removal apparatus  48  shown in  FIG. 8 , it is also possible to scrape off residual toner adhering to the fur brush  22  which is contact with the secondary transferring outer roller  5  by a toner scraping member  32 . In this case, the secondary transferring outer roller  5  rocks using the fur brush  22  as the fulcrum, and cleaning is effected on the secondary transferring outer roller  5  by applying to the fur brush  22  a bias voltage of a polarity reverse to that of the residual toner on the second transferring outer roller  5 . In this embodiment, the fur brush  22  serves as the toner collecting rotary member. 
   This application claims priority from Japanese Patent Application No. 2004-131473 filed on Apr. 27, 2004, which is hereby incorporated by reference herein.