Abstract:
An image forming apparatus including an image forming section that forms an image with a recording material on a recording medium to an edge thereof, and a cleaning section that cleans off the recording material adhering to an edge surface of the recording medium after the image forming section forms the image thereon.

Description:
This application is based on Japanese Patent Application No. 2006-149482 filed on May 30, 2006 in Japanese Patent Office, the entire content of which is hereby incorporated by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to an image forming apparatus, such as an electro-photographic copier, printer or facsimile, and particularly relates to an image forming apparatus having a cleaning device that cleans the edge surfaces of sheets as recording mediums. 
   BACKGROUND OF THE INVENTION 
   When an image is output to peripheral edge portions of a recording medium (al so referred to as a sheet), recording material (such as toner or ink) spreads out of the image area to peripheral portions of the sheet, as shown in  FIG. 4 , which causes a problem of contaminating the hands of a user and other print sheets in taking out a stack of sheets or handling a file. 
     FIG. 4  shows an example of contamination of edge surfaces of sheets. 
   In order to avoid such toner contamination, there are offered methods (for example, refer to Patent Document 1: Japanese Patent Publication TOKKAI No. H07-239617) which bias, in the same polarity as transfer, a transfer entrance guide plate for guiding a sheet to the transfer area to keep toner away and control the timing of biasing, methods (for example, refer to Patent Document 2: Japanese Patent Publication TOKKAI No. H07-271256 and Patent Document 3: Japanese Patent Publication TOKKAI No. 2002-244462) which remove toner adhered to the back side surface of a sheet, and methods (for example, refer to Patent Document 3: Japanese Patent Publication TOKKAI No. 2002-244462) which arrange a suction fan between the transfer area and fixing to absorb spattering or floating toner. 
   However, just by the method which is a technology disclosed in above Patent Document 1 to prevent toner contamination of edge surfaces of a sheet by the timing of biasing a transfer entrance guide plate, it is difficult to remove toner having been adhered. 
   The technology disclosed in Patent Document 2 only removes toner contaminating the back side surface of a sheet, but does not disclose about contamination of edge surfaces. The technology disclosed in Patent Document 3 is effective for collecting toner spattering from a sheet, but is not capable of removing toner adhered to a sheet, and may degrade an unfixed image with a large air flow rate. 
   An object of the present invention is to provide an image forming apparatus having a cleaning device for preventing contamination by excess toner (or ink) adhered to edge surfaces of a sheet even when outputting an image to edge portions. 
   SUMMARY OF THE INVENTION 
   To solve an object, as described above, in an aspect of the invention, there is provided a structure described below. 
   An image forming apparatus, comprising: 
   an image forming section being enable to form an image with a recording material on a recording medium to an edge thereof; and 
   a cleaning section that cleans off the recording material adhering to an edge surface of the recording medium after the image forming section forms the image thereon. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of an inkjet printer in a first embodiment of the invention; 
       FIG. 2  is a top view of a conveying path for a sheet in  FIG. 1 ; 
       FIGS. 3   a  and  3   b  are diagrams illustrating the structures of cleaning members in  FIG. 1 ; 
       FIG. 4  is a diagram showing contamination of edge surfaces of a sheet; 
       FIG. 5  is a schematic diagram of a full-color electro-photographic apparatus in a second embodiment; 
       FIG. 6  shows a sheet conveying path in  FIG. 5 ; 
       FIGS. 7   a  to  7   b  are diagrams showing three types of cleaning members in  FIG. 5 ; and 
       FIGS. 8   a  to  8   d  are plane views of places where the three types of cleaning members are respectively disposed. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Image recording apparatuses in accordance with the invention will be described below, according to preferred embodiments. 
     FIG. 1  is a schematic diagram of an inkjet printer in a first embodiment of the invention. 
   In  FIG. 1 , a sheet  2  conveyed from a sheet feeding cassette  1  is fed out with a pickup roller  5 ; guided by upper and lower guide plates  3  and  4 ; nipped and conveyed by upper and lower conveying rollers  6  and  7 . The conveyed sheet is synchronized with printing by a registration unit, not shown, in the process passing upper and lower guide plates  8  and  9  during conveyance; and is subjected to printing by a recording head section W, which slides in the main scanning direction along guide rails  11 , up to the edge portion of the sheet in the main scanning direction. Then excess ink adhered to the both edge surfaces in the main scanning direction of the sheet is adsorbed by cleaning members  12  being cleaning devices disposed on the both sides in the conveying process at the a conveying section F. The sheet is conveyed further and the leading edge surface of the sheet reaches a cleaning member  13  when excess ink at the leading edge surface is adsorbed. Then, the sheet is ejected onto a slanted sheet ejection tray  15 , and thereafter ink at the trailing edge surface is adsorbed by the cleaning member  13 . 
   The cleaning members  12  and  13  will be described in detail below. 
     FIG. 2  is a top view of the conveying path for the sheet in  FIG. 1 . 
     FIGS. 3   a  and  3   b  are diagrams illustrating the structures of the cleaning members in  FIG. 1 . 
     FIG. 3   a  shows a cross section of the cleaning member  12 , which is constructed with a sponge roller  122 , core metal  123  being the rotation shaft of the sponge roller  122 , and a nonwoven fabric  121  wound around the sponge roller  122 , and the like. The cleaning members  12  are mounted on sliding members, not shown, slidable in arrow direction H, and the positions of the slide rollers  122  are controlled by a control unit so that both side edge surfaces of a sheet contact the sponge rollers  122 , corresponding to the width size of the sheet. The core metals  123  are driven by a driving section, not shown, and thus the sponge rollers  122  rotate in the same direction as the conveyance of the sheet at a contact section S. At the contact section S in the process where a sheet, which has been subjected to printing by the printing section W of a recording head  10 , passes the conveying section F, excess ink at the both side edge surfaces of the sheet is adsorbed, and the leading edge of the sheet reaches the cleaning member  13 . 
     FIG. 3   b  shows the cross-section of the cleaning member  13 , which is constructed with a nonwoven fabric  131  wound around a rotation shaft  132 , sponge guide roller  133 , take up shaft  135 , and the like. A web belt  136  is tension-supported by the nonwoven web roll  131 , which is the source side edge, and the take up shaft  135  via the guide roller  133 . The take up shaft  135  is driven by a driving section, not shown, and rotates at a predetermined rotation speed to take up the belt. 
   When the leading edge surface of a printed sheet has reached the cleaning member  13 , the sheet comes in contact with a web-belt  136  so that excess ink at the leading edge surface is adsorbed, and the sheet slides on a the guide roller  133  with a spur  14  to be conveyed and ejected onto a sheet ejection tray  15 . The ejected sheet slides down due to the slant, and the trailing edge surface of the sheet hits the cleaning member  13  and stops there, by which excess ink at the trailing edge surface is adsorbed. 
   In such a manner, ink at peripheral edge surfaces of a sheet is adsorbed, which prevents contamination of edge surfaces of the sheet and accompanying contamination of the hands of a user and the like. 
   Next, a second embodiment will be described. 
     FIG. 5  is a schematic diagram of a full-color electro-photographic apparatus in a second embodiment. 
     FIG. 6  shows a sheet conveying path in  FIG. 5 . 
   An image forming unit  1 A is constructed with a photoreceptor drum  21 , charger  24 , developer  22 , cleaning unit  23  and the like. Writing device  25  is a digital type exposure writing unit. An intermediate transfer belt  20  is an intermediate transferor. Image forming units  1 A for respective colors are disposed in the order of Y, M, C, and K with respect to the running direction of the intermediate transfer belt  20 . At the time of transfer, each primary transfer roller  26  presses the intermediate transfer belt  20  against the photoreceptor  21  to make them press-contact with each other. In the press-contact area, each photoreceptor drum  21  rotates at the same linear speed and in the same direction as the intermediate belt  20 . 
   The mechanical structures of the image forming units  1 A for the respective colors are the same, and accordingly reference numerals are shown only for the structure for Y color in  FIG. 1 , and description of the reference numerals representing the elements of structures for the other three colors are omitted. 
   The intermediate transfer belt  20  is tension-supported by a drive roller  27 , earth roller  28 , tension roller, driven roller, etc. These rollers, the intermediate transfer belt  20 , primary transfer roller  26 , cleaning device  29  and the like construct an intermediate transfer belt unit  2 A. The charger  25  statically charges photoreceptor drum  21 , and electrical signals corresponding to image data are converted into optical signals by an image forming laser so that a writing device  25  projects light onto the photoreceptor  21  to form a latent image. The latent image is visualized (toner image) by the developer  22 . 
   The intermediate transfer roller  2   o  runs with rotation of the drive roller  27  driven by a drive motor, not shown. 
   The primary transfer roller  26  is applied with a DC voltage in the polarity opposite to the toner, and presses the intermediate transfer belt  20  against the photoreceptor drum  21  from the inner side edge of the belt with a pressing-and-releasing mechanism, not shown, thereby primarily transferring the toner image onto the intermediate transfer belt  29 . 
   The image forming process starts with color Y, such that a toner image is transferred onto the intermediate transfer belt  20 . In synchronization with this, superimposed toner images are formed on the intermediate transfer belt  20  in the order of M, C and K in the same image forming process. The intermediate transfer belt  20  carrying the superimposed toner images is transported clockwise, as shown with the arrow. A sheet P is fed out from a sheet cassette  72  by a sheet feed-out roller  70 , conveyed through a conveying roller  73  to a timing roller  71  and temporarily stopped there, then synchronized, driven by the timing roller  71 , with the superimposed toner images on the intermediate transfer roller  20 , conveyed to a nip section S (secondary transfer section) of a secondary transfer roller  30  (in a state pressed against the intermediate transfer belt  20 ) which is applied with a DC voltage in the polarity opposite to the toner, and the superimposed toner images on the intermediate transfer belt  20  are transferred onto the sheet P at a time. 
   A fixing device  40  is provided with a heat roller  41  and a press roller  42 . The heat roller  41  is formed in a thin tube shape of aluminum provided with a halogen heater  43  that heats the heat roller  41  up to a predetermined temperature from inside, wherein the temperature is detected by a contact-temperature sensor, not shown, arranged for the heat roller  41  and controlled. 
   A sheet ejection roller  81  ejects a transfer medium having been subjected to fixing, to a sheet ejection tray  82  having a certain inclination angle. 
   A control section B 1  which serves as a control unit performs image forming process control, fixing temperature control, transfer medium conveying control, cleaning member driving control, toner density control and the like. 
   The structure related to the image forming process has been described. Now, a conveying path of a sheet will be described, referring to  FIG. 6 . 
   For normal (with a margin) printing, a sheet P with a toner image transferred at the nip section S 1 , passes the fixing device  40 , conveyed through the conveying path  51  and then ejected onto the sheet ejection tray  82 . For double side edged printing, a sheet P is subjected to fixing, then passes a conveying path  52 , gets reversed by a reverse feed roller  54  without being stacked on the stack  53 , passes a sheet feeding path  55 , and a superimposed toner image, which has been formed on the intermediate transfer belt  20 , is transferred onto the back side edge surface of the sheet P by the image forming process same as described above. Them the sheet P is subjected to fixing by the fixing device  40 , passes the conveying path  51 , and is ejected onto the ejection tray  82 . 
   Now, cleaning of edge surfaces of a sheet will be described for a case of printing on an entire sheet. 
   In a case of printing on an entire sheet, the sheet is subjected to transferring of toner images onto the entire sheet at the nip section S 1 , passes the fixing device  40 , and conveyed to the conveying path  52  side edge. The both side edge surfaces are cleaned by cleaning members  56  at a midway of the conveying path  52 , and stacked on the stacker  53  to be temporarily stopped. A cleaning member  57  is arranged in the stacker  53  to clean the surface of the trailing edge portion (with respect to the conveying direction) of the stopping sheet. After completion of cleaning, the sheet is re-fed from the stacker  53  to return to the conveying path  52  side, passes through the conveying path  51 , and is ejected by the sheet ejection roller  81  onto the sheet ejection tray  82 . At the position where the sheet is ejected, the rest of the edge surfaces of the sheet (Herein, the edge which was the trailing edge before re-feeding becomes the leading edge after re-feeding.) is cleaned. 
   The structures of the cleaning members  56  to  58  will be described below. 
     FIGS. 7   a  to  7   c  show three types of cleaning members, shown in  FIG. 6 . 
     FIGS. 8   a  to  8   d  are plan views of structures where the three types of cleaning members are respectively arranged. 
     FIG. 7   a  shows the cross-sectional view of a cleaning member  56 , which is constructed with a sponge roller  562 , core metal  563  being the rotation shaft of the sponge roller  562 , nonwoven fabric  561  wound around the outer circumference of the sponge roller  562 , and the like. 
   In  FIGS. 8   a  and  8   b , the cleaning members  56  are mounted between the conveying rollers A and B on slide members (on both sides along the sheet conveying direction), not shown, which can respectively slide in arrow direction T, and the sponge rollers  562 , which change in the distance therebetween corresponding to the width size of a sheet, are position-controlled by a control unit so that the both side edge surfaces of the sheet can contact the sponge rollers  562 . The metal cores  563  are driven by a driving section, not shown, and thus the sponge rollers  562  rotate at the contact sections S 2 , where the sponge rollers  562  contact the side edge surfaces of the sheet, in the direction opposite to the sheet conveying direction.  FIGS. 8   a  and  8   b  are plan views from arrow direction X in  FIG. 6 . 
   In  FIG. 8   a , the cleaning members  56  retreat at a position where the cleaning members  56  do not cause a load on sheet conveyance until a sheet having been subjected to printing on its both sides and passed the conveying path  52  is nipped at the leading edge by the conveying rollers A. When the leading edge of the sheet gets nipped, the cleaning members  56  contact the side edge surfaces of the sheet, and rotate in the direction opposite to the sheet conveying direction so as to clean off toner at the both side edge surfaces. 
     FIG. 7   b  shows a cross-sectional view of the cleaning member  57 , and  FIG. 8   c  shows a cross-sectional view, viewed from above, of the stacker  53  having the cleaning member  57  thereon. The cleaning member  57  is structured such that a nonwoven fabric  573  in a belt shape is tension-supported by a pair of rollers constructed with a core metal  571  and an elastic body  572 . Either roller is driven by a driving source to rotate in the arrow direction, and thus the nonwoven fabric  573  reciprocally moves at a predetermined frequency in arrow direction U (perpendicular to the thickness of the sheet). A backup member  574  is arranged inside the nonwoven fabric  573 , and the edge surface of the sheet hits the outer surface of the nonwoven fabric  573  and stops there. The reciprocal motion of the belt cleans off ink at the trailing edge surface of the sheet P which is stopping on the stacker. The trailing edge of cleaned sheet P becomes the leading edge, and the sheet is re-fed. Herein, the stacker  53  is provided with a leading edge (namely, trailing edge in re-feeding) restricting plate  575  and side surface restricting plates  576  which slide along guides, to align stacked sheets P and push the trailing edge surface (namely, leading edge surface in re-feeding) of a sheet having been conveyed there, against the cleaning member  57 . 
     FIG. 7   c  shows a cross-sectional view of the cleaning member  58 , and  FIG. 8   d  shows a cross-sectional view, viewed from above, of the sheet ejection tray  82  having the cleaning member  58  thereon. The cleaning member  58  is structured such that a nonwoven fabric  583  in a belt shape is tension-supported by a pair of rollers constructed with a core metal  581  and an elastic body  582 . Either roller is driven by a driving source to rotate in the arrow direction, and thus the nonwoven fabric  583  reciprocally moves in arrow direction V (perpendicular to the thickness of the sheet). A backup member  584  is arranged inside the nonwoven fabric  583 , and the edge surface of the sheet hits the outer surface of the nonwoven fabric  583  and stops there. The reciprocal motion of the belt cleans off ink at the trailing edge surface of the sheet P having been ejected. 
   The three types of cleaning members have been described. However, for an image recorded on a single side of a sheet P which sticks out on the trailing edge side, the sheet P having been conveyed through the conveying path  51  without being conveyed to the stacker  53 , and ejected onto the sheet ejection tray  82  may be cleaned only by the cleaning member  58 . 
   In accordance with invention, contamination of edge surfaces of a recording medium can be removed, and particularly, a problem of contaminating the hands of a user in taking out sheets stacked on a tray and a problem of contaminating other print sheets can be solved.