Abstract:
A cleaning device capable of reducing the apparatus and prolonging the service life of the cleaning blade is disclosed. The cleaning device includes a cleaning blade including an elastic blade, a pressing member disposed near the downstream side of the image carrier with respect to the elastic blade, and a driving mechanism for driving the pressing member so as to be in contact with and press the elastic blade. The driving mechanism operates so as to press the elastic blade in the upstream direction to separate the elastic blade from the surface of the image carrier for a while. Then, the driving mechanism operates to move the pressing member to be separated from the elastic blade so that the elastic blade is in contact with the surface of the image carrier.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to a cleaning device, a process cartridge, and an image forming apparatus, and more specifically to a cleaning device, a process cartridge, and an image forming apparatus having an electrophotographic process unit. 
         [0003]    2. Description of the Related Art 
         [0004]    The electrophotographic process performed in an image forming apparatus generally includes charging, exposing, developing, transferring, fixing, and cleaning. In the cleaning process performed as a final process, a blade cleaning method is usually used. 
         [0005]    Some full-color image forming apparatuses employ the blade cleaning method. Such full-color image forming apparatus includes developing devices for developing yellow (Y), magenta (M), cyan (C), and black (Bk) images, respectively. Each developing device includes a photosensitive drum serving as an image carrier capable of being rotatably driven, and the surface of the photosensitive drum is uniformly charged by a charging device. Then, a laser beam is irradiated onto the surface by an optical system for exposure so that the surface of the photosensitive drum is exposed to form an electrostatic latent image on the surface of the photosensitive drum. Then, a developing agent in the developing unit is applied to the surface of the photosensitive drum so that a visible image is formed on the photosensitive drum. 
         [0006]    The image forming apparatus further includes an intermediate transferring device, and the formed visible image is transferred in a contacting section between the intermediate transferring device and the photosensitive drum. More specifically, the formed visible image on the surface of the photosensitive drum is transferred onto a surface of a transfer belt by a transferring roller in the intermediate transferring device. The transferred developing agent forming the visible toner image is transferred onto a sheet serving as an image carrier in a secondary transferring section. Then, the sheet is fed into a fixing device, where the toner image is fixed on the sheet. On the other hand, the developing agent remaining on the surface of the photosensitive drum is cleaned and removed by a cleaning blade in a cleaning device. An image forming apparatus having the above configuration is described in Patent Document 1 (Japanese Patent Application Publication No. 2006-243411). 
         [0007]    The cleaning blade accommodated in a developing device has a plate shape and is made of an elastic member of such material as polyurethane. The cleaning blade is fixed to a supporting body and is pressed to and in contact with a surface of the rotating photosensitive body. Generally, there are two types of developing units. 
         [0008]      FIG. 13  is a cut-open view schematically showing a first type of the developing unit. As shown in  FIG. 13 , in this developing device  4 , a head of a cleaning blade  11   a  of a cleaning device  11  is in contact with a photosensitive drum  1 . The cleaning blade  11   a  is directly fixed to a chassis  4   j  of the developing device  4  with a bolt so that the cleaning blade  11   a  is pressed to and in contact with the photosensitive drum  1  with a prescribed contacting pressure. This contacting pressure is produced by a restoration force due to elastic deformation of the cleaning blade  11   a , the restoration force being used as a blade pressing force applied to the photosensitive drum  1 . 
         [0009]      FIG. 14  is a cut-open view schematically showing a second type of the developing unit. As shown in  FIG. 14 , in the developing device  4 , a pressure promoting member  4   k  includes a supporting shaft and a spring so that the pressure promoting member  4   k  is rotatably attached to a part of a supporting body of the developing device  4 . As a result, the cleaning blade  11   a  is in contact with the surface of the photosensitive drum  1  due to a pressing force produced by the pressure promoting member  4   k.    
         [0010]    The cleaning blade  11   a  fixed to the chassis  4   j  of the first developing unit  4  has some advantages: a simple structure, easy to reduce the size, and low cost because such units as a driving unit and a biasing unit are not necessary. However, since the cleaning blade  11   a  always in contact with the image carrier (photosensitive drum), the cleaning blade  11   a  is likely to be deformed and the pressure applied to the image carrier is likely to be reduced due to the permanent distortion of the cleaning blade  11   a . Further, it is difficult to remove toner or any foreign matter such as paper powder remaining in a contacting part between the elastic cleaning blade  11   a  and the image carrier  1 , which often causes abnormal images. 
         [0011]    On the other hand, in the second developing unit  4 , the movable cleaning blade  11   a  can be put in contact with and separated from the image carrier by an added contacting and separating mechanism for separating the cleaning blade  11   a  from the image carrier and a position controlling member for adjusting the position of the cleaning blade  11   a  with respect to the image carrier. This method is being employed in systems requiring long service life. 
         [0012]    As described above, implementing such a movable cleaning blade or such a contacting and separating mechanism is useful to avoid damage to the edge of the cleaning blade caused by the residual toner or foreign matter. However, recently there has been a demand for reducing the size of the image forming apparatus. Unfortunately, it is difficult to achieve a good balance between the implementation and the demand because of cost increases with conventional technology. As a result, the implementation is tending to be neglected and long service lives of the cleaning blade and the photosensitive body are not being provided in many cases. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention is made in light of the circumstances, and may provide a cleaning device, a process cartridge, and an image forming apparatus capable of reducing the size of the apparatus and prolonging the service life of the cleaning blade. 
         [0014]    According to a first aspect of the present invention, there is provided a cleaning device installed in an image forming apparatus including an image carrier, a charging device for uniformly charging a surface of the image carrier, an exposing device for exposing the uniformly-charged surface of the image carrier to form an electrostatic image, a developing device for developing the formed electrostatic image with a developing agent so as to form a visible image on the image carrier, a transferring device for transferring the image on the image carrier onto a transferring member, and the cleaning device for removing the developing agent remaining on the image carrier after the visible image has passed through the transferring device, the cleaning device including a cleaning blade including an elastic blade, the elastic blade being fixed to a chassis of the cleaning device, and an edge of the elastic blade being in contact with the surface of the image carrier on a steady basis, a pressing member disposed near the downstream side of the image carrier with respect to the elastic blade and extending in the longitudinal direction of the elastic blade; and a driving mechanism for driving the pressing member so that the pressing member is in contact with and presses a downstream side surface of the elastic blade, wherein, when an image forming process is ended, the driving mechanism operates so that the pressing member presses the elastic blade in the upstream direction of the image carrier so as to separate the elastic blade from the surface of the image carrier for a while, and then, the driving mechanism operates to move the pressing member to be separated from the elastic blade so that the elastic blade is in contact with the surface of the image carrier. 
         [0015]    According to a second aspect of the present invention, the pressing member is a rod-shaped member. 
         [0016]    According to a third aspect of the present invention, the pressing member is a thin plate-shaped member. 
         [0017]    According to a fourth aspect of the present invention, the cleaning device further includes a removing member having a sheet shape, disposed on the upstream side of the image carrier with respect to the cleaning blade, and in contact with the edge of the elastic blade when the elastic member is pressed by the pressing member to be separated from the image carrier. 
         [0018]    According to a fifth aspect of the present invention, the removing member is made of urethane resin. 
         [0019]    According to a sixth aspect of the present invention, the cleaning device further includes a brush roller disposed on the upstream side of the image carrier with respect to the cleaning blade so that the brush roller is in contact with the image carrier and the circumference of the brush roller is in contact with the edge of the elastic blade when the elastic blade separates from the image carrier. 
         [0020]    According to a seventh aspect of the present invention, just before the elastic blade separates from the image carrier, the image carrier rotates in the direction opposite to the normal direction for forming an image. 
         [0021]    According to an eighth aspect of the present invention, there is provide a process cartridge including a charging device for uniformly charging a surface of an image carrier, a developing device for developing an electrostatic image formed on the image carrier with a developing agent so as to form a visible image on the image carrier; and a cleaning device as described above. 
         [0022]    According to a ninth aspect of the present invention, there is provided an image forming apparatus including the above cleaning device. 
         [0023]    According to a tenth aspect of the present invention, there is provided an image forming apparatus including the above process cartridge. 
         [0024]    According to an embodiment of the present invention, there is provided a pressing member having a simple structure for deforming an elastic blade to separate the elastic blade from the surface of an image carrier and making contact between the elastic blade and the surface of an image carrier again. Due to the impact when the elastic blade is in contact with the surface of the image carrier, remaining toner (developing agent) and foreign matter attached to the edge of the elastic blade are blown off, thereby securing stable toner cleaning performance for a long period of time and avoiding the formation of an abnormal image. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Other objects, features, and advantages of the present invention will become more apparent from the following descriptions when read in conjunction with the accompanying drawings, in which: 
           [0026]      FIG. 1  is a cut-open view schematically showing the image forming apparatus according to an embodiment of the present invention; 
           [0027]      FIG. 2  is a cut-open view schematically showing a configuration of the cleaning device according to a first embodiment of the present invention; 
           [0028]      FIG. 3  is a perspective view showing the pressing member shown in  FIG. 2 ; 
           [0029]      FIG. 4  is a cut-open view schematically showing the pressing member and the driving mechanism in  FIG. 2 ; 
           [0030]      FIG. 5  is a schematic diagram showing a cleaning device according to a modified first embodiment of the present invention; 
           [0031]      FIG. 6  is a schematic diagram showing a cleaning device according to another modified first embodiment of the present invention; 
           [0032]      FIG. 7  is a cut-open view schematically showing a cleaning device according to a second embodiment of the present invention; 
           [0033]      FIG. 8  is a perspective view showing a pressing member pressing the cleaning blade in the cleaning device; 
           [0034]      FIG. 9  is a cut-open view schematically showing an operation of the pressing member in the cleaning device; 
           [0035]      FIG. 10  is a drawing showing a mechanism for driving the pressing member; 
           [0036]      FIG. 11  is a cut-open view schematically showing a cleaning device according to a modified second embodiment of the present invention; 
           [0037]      FIG. 12  is a cut-open view schematically showing a cleaning device according to another modified second embodiment of the present invention; 
           [0038]      FIG. 13  is a cut-open view schematically showing a first type of a conventional developing unit; and 
           [0039]      FIG. 14  is a cut-open view schematically showing a second type of a conventional developing unit. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    Exemplary embodiments of the present invention are described with reference to the accompanying drawings. 
       Embodiment 1 
       [0041]    In the following, an image forming apparatus according to an embodiment of the present invention is described.  FIG. 1  is a cut-open view schematically showing the image forming apparatus according to an embodiment of the present invention. The image forming apparatus according to an embodiment of the present invention is a full-color image forming apparatus employing the electrophotographic method. The image information apparatus includes developing devices  4  for developing yellow (Y), magenta (M), cyan (C), and black (Bk) images, respectively. In the vicinity of the each developing device, there is provided a photosensitive drum  1  having an optical conductive layer made of organic material such as OPC and serving as an image carrier capable of rotating in both normal and opposite directions. In the vicinity of the photosensitive drum  1 , along the normal rotating direction, there are provided a charging roller  2 , an exposing device  3 , a developing device  4 , and a cleaning device  11  to perform an image forming process. Those devices for each color are arranged in parallel to constitute a process cartridge. 
         [0042]    The charging roller  2  is a conductive roller in contact with the photosensitive drum so as to rotate in accordance with the rotation of the photosensitive drum  1 . A direct current voltage or a superimposed voltage including a direct current voltage and an alternative current voltage from a high voltage source is applied to the photosensitive drum  1  through the charging roller  2 , so that the optical conductive layer is uniformly charged. 
         [0043]    Then, an electrostatic latent image is formed on the photosensitive drum  1  by the exposing device  3 . The electrostatic latent image on the photosensitive drum  1  is developed by the developing device  4 . As the developing device  4 , a contact-type one-component developing device is used. In the contact-type one-component developing device, a developing roller  4   a  made of, for example, an elastic body is in contact with the photosensitive drum  1 , and toner  5  stored in a hopper is supplied and fed to the developing roller  4   a  through a supplying roller  4   b . Then, a thin toner layer is formed on the developing roller with the supplied and fed toner by using a regulating blade in contact with the developing roller. When the thin toner layer is in contact with the electrostatic latent image, the electrostatic latent image is formed (visualized). 
         [0044]    The visualized images formed on the photosensitive drum  1  by the corresponding developing devices  4  of four colors are sequentially transferred and superposed onto a transferring belt  8   a  in a primary transferring section, so that a full color image is formed on the transferring belt  8   a.    
         [0045]    As shown in  FIG. 1 , a transferring device  8  includes a driving roller  8   b , a transferring belt  8   a  stretched between a pair of rollers including the driving roller  8   b , transferring bias rollers  8   d  disposed inside the transferring belt  8   a  and facing the photosensitive drums  1  of each color, a contacting and separating mechanism (not shown) for causing the transferring belt  8   a  and the transferring bias rollers  8   d  to contact the photosensitive drums  1 , and a transferring belt cleaning device (not shown) having an elastic blade  8   e.    
         [0046]    In the transferring device  8 , the visualized image on each of the photosensitive drums  1  is transferred onto the transferring belt  8   a  by applying a bias voltage from a high voltage source through the transferring bias roller  8   d . Then, a transferring sheet fed from a sheet supplying device at resist timing set by a resist roller is fed to a roller  8   c  in the transferring device  8  so that the transferring sheet is pressed by a secondary transferring roller  9 . Then, the full color image formed on the transferring belt  8   a  is transferred onto the transferring sheet by applying a bias voltage from a high voltage source to the secondary transferring roller  9 . 
         [0047]    The transferring sheet onto which the full color image is transferred by the transferring device  8  is fed to a fixing device  10  and is ejected onto an ejection tray (not shown). In each developing device  4 , after a visualized image is formed on the photosensitive drum  1 , the toner remaining on the photosensitive drum  1  as transfer remaining toner not transferred in the primary transferring section is conveyed in accordance with the rotation of the photosensitive drum  1  and is collected in the cleaning device  11 . 
         [0048]      FIG. 2  is a cut-open view schematically showing a configuration of the cleaning device  11 . As shown in  FIG. 2 , the cleaning device  11  includes a cleaning blade  11   a , a conveying screw  11   b , and a screw  11   e . The cleaning blade  11   a  includes an elastic blade  11   c  having a rectangular shape and a supporting member  11   d  supporting the elastic blade  11   c . The supporting member  11   d  of the cleaning blade  11   a  is fixed to a prescribed position in the chassis  11   f  of the cleaning device  11  with the screw  11   e , so that the edge of the elastic blade  11   c  is in contact with the photosensitive drum  1  when the cleaning device  11  and the photosensitive drum  1  are in contact with each other. The conveying screw  11   b  conveys the remaining toner collected by the cleaning device  11  to a toner collecting bottle (not shown). 
         [0049]    In this example shown in  FIG. 2 , there is provided a pressing member  12  manufactured by bending a round-rod member and disposed in the vicinity of a surface of the elastic blade  11   c  on a downstream side of the photosensitive drum  1 . The pressing member  12  is driven by a driving mechanism  30 . When an image forming process ends, the pressing member  12  presses the elastic blade  11   c  in the upstream direction of the photosensitive drum  1 , so that the elastic blade  11   c  separates from the surface of the photosensitive drum  1 . Then, after a prescribed time period, the pressing member  12  is moved in the direction so that the pressing member  12  separates from the elastic blade  11   c . As a result, the elastic blade  11  is in contact with the photosensitive drum  1  again. 
         [0050]      FIG. 3  is a perspective view showing the pressing member  11 .  FIG. 4  is a cut-open view schematically showing the pressing member  12  and the driving mechanism  30 . As shown in  FIG. 3 , the pressing member  12  extends in the direction parallel to the longitudinal direction of the elastic blade  11   c . The pressing member  12  has a bent part  12   a  and a bent part  12   b  disposed beyond each end of the elastic blade  11   c  across an extended part  12   c  and bent with a prescribed crank angle. Further, at least one of the ends  12   d  of the pressing member  12  is rotatably supported by a supporting part of the chassis  11   f  of the cleaning device  11  and is extended through the chassis  11   f  of the cleaning device  11  to the outside where an arm member  13  is fixed to the end  12   d.    
         [0051]    The pressing member  12  is driven by a driving mechanism  30 . The driving mechanism  30  includes the arm member  13  fixed to the end  12   d  of the pressing member  12  and a spring  14  interposed between the arm member  13  and a fixing part  15  on the chassis  11   f  of the cleaning device  11 . The arm member  13  is biased toward the fixing part  15  by the spring  14 . Further, in the cleaning device  11 , as shown in  FIG. 4 , there is provided a cam  16  capable of being rotated by a driving motor  17  and in contact with the arm member  13  so as to drive the arm member  13  to oscillate in the up and down direction. 
         [0052]    To drive the arm member  13  so that the end of the arm member  13  oscillates in the up and down direction, the outer circumferential contour shape of the cam  16  is formed in a manner so that the radius of the cam increases from the minimum radius to the maximum radius as the cam rotates 360 degrees and suddenly decreases from the maximum radium to the minimum radius, as shown in  FIG. 4 . Because of the contour shape of the cam  16 , when the cam  16  is rotated by the driving motor  17  and the distance between the center of the cam  16  and the arm member  13  equals an effective radius (refers to the shortest distance between the center of the cam  16  and the arm member  13 ) of the cam  16 , the cam  16  is in contact with the arm member  13  and starts rotating the arm member  13  as the cam  16  rotates. 
         [0053]    As shown in  FIG. 4 , as the arm member  13  rotates, the pressing member  12  also rotates and the extended part  12   c  of the pressing member  12  is in contact with and presses the surface of the elastic blade  11   c  so that the elastic blade  11   c  elastically deforms in the upstream direction of the photosensitive drum  1 . By doing this, the edge of the elastic blade  11   c  is separated from the surface of the photosensitive drum  1 . When the effective radius of the cam  16  equals the maximum radius of the cam  16 , the distance between the edge of the elastic blade  11   c  and the surface of the photosensitive drum  1  is also maximized. Then, the cam  16  further rotates, the effective radius suddenly decreases and accordingly, the pressing force of the arm member  13  is also suddenly released. As a result, the arm member  13  is pulled toward the fixing part  15  by the spring  14 ; the pressing member  12  separates from the surface of the elastic blade  11   c ; and the elastic blade  11   c  is in contact with the surface of the photosensitive drum  1  again. Due to the impact when the elastic blade  11   c  makes contact with the surface of the photosensitive drum  1 , remaining toner and foreign matter attached to the edge of the elastic blade  11   c  are blown off and collected by the conveying screw  11   b  provided in the chassis  11   f  of the cleaning device  11 . 
         [0054]    The driving mechanism  30  is controlled by a driving controlling device (not shown). When an image forming process is ended, the driving mechanism  30  is driven by the driving controlling device so that the pressing member  12  presses the elastic blade  11   c  to the upstream side of the photosensitive drum  1  to separate the elastic blade  11   c  from the surface of the photosensitive drum  1 . After a prescribed time period, the pressing member  12  is driven and moved in the downstream direction of the photosensitive drum  1  so that the pressing member  12  separates from the elastic blade  11   c . As a result, the elastic blade  11   c  is in contact with the surface of the photosensitive drum  1  again. 
         [0055]    Next, a modified embodiment of the present invention is described.  FIG. 5  is a schematic diagram showing a cleaning device according to a modified first embodiment of the present invention. In this modified embodiment, there is provided a removing section  18  made of urethane resin sheet material. The removing section  18  is disposed on the upstream side of the photosensitive drum  1  with respect to the cleaning blade  11   a , so that the removing section  18  is in contact with the edge of the elastic blade  11   c  when the elastic blade  11   c  is pressed by the pressing member  12  and separated from the surface of the photosensitive drum  1 . 
         [0056]    According to this modified embodiment of the present invention, when the elastic blade  11   c  of the cleaning blade  11   a  is deformed by the pressing member  12 , the edge of the elastic blade  11   c  is in contact with the edge of the removing section  18  so that the remaining toner and foreign matter attached to the edge of the elastic blade  11   c  can be effectively removed. 
         [0057]      FIG. 6  is a schematic diagram showing a cleaning device according to another modified first embodiment of the present invention. In this modified embodiment, there is provided a brush roller  19  disposed on the upstream side of the photosensitive drum  1  with respect to the cleaning blade  11   a , so that the brush roller  19  is in contact with the photosensitive drum  1  and the circumference of the brush roller  19  is in contact with the edge of the elastic blade  11   c  when the elastic blade  11   c  is pressed by the pressing member  12  and separated from the surface of the photosensitive drum  1 . 
         [0058]    According to this modified embodiment of the present invention, when the elastic blade  11   c  is separated from the photosensitive drum  1 , the edge of the elastic blade  11   c  is in contact with the circumference of the brush roller  19 , so that the remaining toner and foreign matter attached to the edge of the elastic blade  11   c  can be effectively removed. 
         [0059]    Further, it is possible to arrange that just before the elastic blade  11   c  separates from the photosensitive drum  1  or while the elastic blade  11   c  separates from the photosensitive drum  1 , the photosensitive drum  1  rotates by a prescribed angular distance in the direction opposite to the normal direction for forming an image. As a result of this arrangement, when the elastic blade  11   c  is in contact with the photosensitive drum  1  again, the elastic blade  11   c  is in contact with the downstream side of the photosensitive drum  1  by the prescribed angular distance. Therefore, it becomes possible to remove the toner remaining on the surface of the photosensitive drum  1  when the cleaning blade  11   a  is separated from photosensitive drum  1 , thereby avoiding the contamination of the charging roller  2  disposed on the downstream side with respect to the cleaning blade  11   a.    
       Embodiment 2 
       [0060]    Next, an image forming apparatus according to a second embodiment of the present invention is described with reference to  FIGS. 7 through 10 . It is assumed that a configuration of the image forming apparatus according to the second embodiment of the present invention is the same as that of the image forming apparatus according to the first embodiment of the present invention unless otherwise described. 
         [0061]      FIG. 7  is a cut-open view schematically showing a cleaning device  11  according to the second embodiment of the present invention.  FIG. 8  shows a configuration of the pressing member  20  shown in  FIG. 7  pressing the cleaning blade  11   a  in the cleaning device  11 .  FIG. 9  is a cut-open view schematically showing an operation of the pressing member  20  in the cleaning device  11 .  FIG. 10  is a drawing showing a mechanism for driving the pressing member  20 . It should be noted that the cleaning device  11  according to this second embodiment of the present invention is similar to the cleaning device  11  according to the first embodiment of the present invention. Namely, the cleaning device  11  according to the second embodiment of the present invention includes a cleaning blade  11   a , a conveying screw  11   b , and a screw  11   e . The cleaning blade  11   a  includes an elastic blade  11   c  having a rectangular shape and a supporting member  11   d  supporting the elastic blade  11   c . The supporting member  11   d  of the cleaning blade  11   a  is fixed to a prescribed position in the chassis  11   f  of the cleaning device  11  with the screw  11   e , so that the edge of the elastic blade  11   c  is in contact with the photosensitive drum  1  when the cleaning device  11  and the photosensitive drum  1  are in contact with each other. The conveying screw  11   b  conveys the remaining toner collected by the cleaning device  11  to a toner collecting bottle (not shown). 
         [0062]    The configuration of the pressing member  20  according to this second embodiment of the present invention is different from that of the first embodiment of the present invention. More specifically, as shown in  FIG. 8 , the pressing member  20  includes a contacting plate member  20   a  and a holding member  20   b . The contacting plate member  20   a  has a thin plate shape and is in contact with the elastic blade  11   c . The holding member  20   b  has a rod shape and supports the contacting plate member  20   a . Further, as shown in  FIG. 9 , the pressing member  20  extends in the direction parallel to the longitudinal direction of the elastic blade  11   c , and is disposed so that the edge of the contacting plate member  20   a  is in contact with the surface of the elastic blade  11   c  at a prescribed angle “θ”. 
         [0063]    In this embodiment, both ends of the holding member  20   b  of the pressing member  20  are supported by supporting parts  20   c  of cleaning cartridge side plates and are in contact with the cam  23  so that the prescribed angel “θ” is substantially constant as the pressing member  20  changes its position according to the rotation of the cam  23 . Further, the holding member  20   b  is biased to the side of the cam  23  by a compression spring  21 . 
         [0064]    The cam  23  has the same shape as that of the cam  16  and is driven by a driving motor  22 . As the cam  23  rotates, the pressing member  20  moves along the contour of the cam  23  and the edge of the contacting plate member  20   a  is in contact with the photosensitive drum  1  side of the elastic blade  11   c  at the prescribed angle “θ”. As the pressing member  20  moves, the pressing member  20  deforms the elastic blade  11   c  so that the elastic blade  11   c  separates from the photosensitive drum  1 . As the cam  23  further rotates, the pressing member  20  moves into a position where the effective radius of the cam  23  is minimum. Then, the holding member  20   b  is biased by the compression spring  21 , and the contacting plate member  20   a  separates from the elastic blade  11   c . As a result, the elastic blade  11   c  is in contact with the photosensitive drum  1  again. 
         [0065]    When an image forming process ends and the stopped status of the photosensitive drum  1  is detected, as shown in  FIG. 10 , a controlling unit (not shown) drives and rotates the driving motor  22  to rotate the cam  23 . As a result, the cam  23  moves the holding member  20   b  so that the contacting plate member  20   a  is moved in the direction of the elastic blade  11   c.    
         [0066]    As the cam  23  rotates, the outer circumference of the cam  23  is in contact with the holding member  20   b . Then, the holding member  20   b  is pressed in the direction of the photosensitive drum  1 , and the contacting plate member  20   a  is in contact with the elastic blade  11   c  at a prescribed angle “θ”. Then, the elastic blade  11   c  is elastically deformed and separates from the surface of the photosensitive drum  1 . When the holding member  20   b  moves and is in contact with the cam  23  at a position where the effective radius of the cam  23  is maximum, the separation distance between the elastic blade  11   c  and the surface of the photosensitive drum  1  is maximized. 
         [0067]    As the cam  23  further rotates, the effective radius suddenly decreases. Then, the holding member  20   b  separates from the cam  23 , and the holding member  20   b  is moved by the compression spring  21  into a position where the holding member  20   b  does not deform the elastic blade  11   c . Then, the edge of the elastic blade  11   c  is in contact with the surface of the photosensitive drum  1  due to the restoration force of the elastic blade  11   c . Due to the impact when the elastic blade  11   c  regains contact with the surface of the photosensitive drum  1 , remaining toner and foreign matter attached to the edge of the elastic blade  11   c  are blown off and collected by the conveying screw  11   b  provided in the chassis  11   f  of the cleaning device  11 . 
         [0068]    Next, a modified second embodiment of the present invention is described.  FIG. 11  is a cut-open view schematically showing a cleaning device  11  according to the modified second embodiment of the present invention. In this modified embodiment, there is provided a removing section  18  made of urethane resin sheet material. The removing section  18  is disposed on the upstream side of the photosensitive drum  1  with respect to the cleaning blade  11   a , so that the removing section  18  is in contact with the edge of the elastic blade  11   c  when the elastic blade  11   c  is pressed by the pressing member  12  and separated from the surface of the photosensitive drum  1 . 
         [0069]    According to this modified embodiment of the present invention, when the elastic blade  11   c  of the cleaning blade  11   a  is deformed by the pressing member  20 , the edge of the elastic blade  11   c  is in contact with the edge of the removing section  18  so that the remaining toner and foreign matter attached to the edge of the elastic blade  11   c  can be effectively removed. 
         [0070]      FIG. 12  is a cut-open view schematically showing a cleaning device  11  according to another modified second embodiment of the present invention. In this modified embodiment, there is provided a brush roller  19  disposed on the upstream side of the photosensitive drum  1  with respect to the cleaning blade  11   a , so that the brush roller  19  is in contact with the photosensitive drum  1  and the circumference of the brush roller  19  is in contact with the edge of the elastic blade  11   c  when the elastic blade  11   c  is pressed by the pressing member  20  and separated from the surface of the photosensitive drum  1 . 
         [0071]    According to this modified embodiment of the present invention, when the elastic blade  11   c  is separated from the photosensitive drum  1 , the edge of the elastic blade  11   c  is in contact with the circumference of the brush roller  19 , so that the remaining toner and foreign matter attached to the edge of the elastic blade  11   c  can be effectively removed. 
         [0072]    Further, it is possible to arrange that just before the elastic blade  11   c  separates from the photosensitive drum  1  or while the elastic blade  11   c  separates from the photosensitive drum  1 , the photosensitive drum  1  rotate by a prescribed angular distance in the direction opposite to the normal direction for forming an image. As a result of this arrangement, when the elastic blade  11   c  is in contact with the photosensitive drum  1  again, the elastic blade  11   c  is in contact with the downstream side of the photosensitive drum  1  by the prescribed angular distance. Therefore, it becomes possible to remove the toner remaining on the surface of the photosensitive drum  1  when the cleaning blade  11   a  is separated from photosensitive drum  1 , thereby avoiding the contamination of the charging roller  2  disposed on the downstream side with respect to the cleaning blade  11   a.    
         [0073]    As described above, in a cleaning device according to an embodiment of the present invention, a simple contacting and separating mechanism is provided so as to control the cleaning blade fixed to the chassis of the cleaning device. As a result, it becomes possible to provide a compact cleaning device and to obtain high quality images for a long time period. 
         [0074]    Further, according to an embodiment of the present invention, there is provided a removing section made of urethane resin sheet material. The removing section is disposed on the upstream side of the photosensitive drum with respect to the cleaning blade, so that the removing section is in contact with the edge of the elastic blade when the elastic blade is pressed by the pressing member and separated from the surface of the photosensitive drum. Because of this configuration, when the elastic blade of the cleaning blade is deformed by the pressing member, the edge of the elastic blade is in contact with the edge of the removing section so that the remaining toner and foreign matter attached to the edge of the elastic blade can be effectively removed, thereby providing a simple configuration and a stable toner cleaning performance. 
         [0075]    Still further, according to an embodiment of the present invention, there is provided a brush roller disposed on the upstream side of the photosensitive drum with respect to the cleaning blade, so that the brush roller is in contact with the photosensitive drum and the circumference of the brush roller is in contact with the edge of the elastic blade when the elastic blade is pressed by the pressing member and separated from the surface of the photosensitive drum. When the elastic blade is separated from the photosensitive drum, the edge of the elastic blade is in contact with the circumference of the brush roller, so that the remaining toner and foreign matter attached to the edge of the elastic blade can be effectively removed, thereby providing a simple configuration and a stable cleaning performance. 
         [0076]    Still further, according to an embodiment of the present invention, the image carrier is driven and rotated in the direction opposite to the normal direction for forming an image just before the elastic blade separates from the photosensitive drum. As a result of this arrangement, when the elastic blade is in contact with the photosensitive drum again, the toner remaining on the surface of the photosensitive drum can be collected by the cleaning blade without being skipped, thereby avoiding the contamination of the charging roller disposed on the downstream side with respect to the cleaning blade. 
         [0077]    The present invention is not limited to the above embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
         [0078]    The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2007-159714, filed on Jun. 18, 2007, the entire contents of which are hereby incorporated herein by reference.