Patent Publication Number: US-7899354-B2

Title: Cleaning device, process cartridge and image formation apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2006-263409 filed Sep. 27, 2006. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a cleaning device, a process cartridge and an image formation apparatus. 
     2. Related Art 
     In recent years, the contact charging method, which causes an electrically conductive charging roll or the like, to be directly contacted with a photosensitive material for charging the photosensitive material has become a leading method, because the amount of ozone and nitrogen oxides generated is smaller to a large extent, and the power efficiency is good. 
     With such a contact charging method, the charging roll is press-contacted with the surface of a photosensitive material with a pressure more than or equal to a predetermined value, thus foreign matters, such as toner, paper dust or the like, left on the photosensitive material are adhered to the charging roll, which may cause poor charging. Thus, a cleaning member which is contacted with the overall length in the longitudinal direction of the surface of the charging roll is provided, however, deflection of the cleaning member and the like make it difficult to cause the cleaning member to be contacted uniformly in the longitudinal direction of the charging roll. 
     SUMMARY 
     A cleaning device of an aspect of the present invention includes a cleaning member that cleans a surface of a rotating cylindrical element to be cleaned, and whose length in a longitudinal direction is longer than a length of the maximum operating region of the element to be cleaned, a length of a contact part of the cleaning member at which the cleaning member contacts with the element to be cleaned being shorter than the length in the longitudinal direction of the cleaning member, and the contact part being moved in the longitudinal direction of the element to be cleaned. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention will be described in detail with reference to the following figures, wherein: 
         FIG. 1  is a schematic configuration drawing illustrating an image formation apparatus pertaining to a first exemplary embodiment of the present invention; 
         FIG. 2  is a configuration drawing illustrating a charging roll, a cleaning brush, a contact part moving device, and components in the vicinity thereof which are used in the image formation apparatus as shown in  FIG. 1 ; 
         FIG. 3A  is a perspective view of a contact part moving device;  FIG. 3B  is a side view of the contact part moving device; and  FIG. 3C  is a front view of the contact part moving device; 
         FIG. 4A  is a side view of a cleaning brush, and  FIG. 4B  is a front view of the cleaning brush; 
         FIGS. 5A and 5B  are a side view and a front view, respectively, illustrating a phase of operation of the cleaning brush and the contact part moving device; 
         FIGS. 6A and 6B  are a side view and a front view, respectively, illustrating a phase of operation of the cleaning brush and the contact part moving device; 
         FIGS. 7A and 7B  are a side view and a front view, respectively, illustrating a phase of operation of the cleaning brush and the contact part moving device; 
         FIGS. 8A and 8B  are a side view and a front view, respectively, illustrating a phase of operation of the cleaning brush and the contact part moving device; 
         FIGS. 9A ,  9 B, and  9 C are drawings illustrating a modification of the contact part moving device,  FIG. 9A  being a perspective view of the modified contact part moving device;  FIG. 9B  a side view of the modified contact part moving device; and  FIG. 9C  a front view of the modified contact part moving device; 
         FIGS. 10A and 10B  are drawings illustrating a modification of the contact part moving device,  FIG. 10A  being a side view of the modified contact part moving device, and  FIG. 10B  a front view of the modified contact part moving device; 
         FIGS. 11A and 11B  are drawings illustrating a modification of the cleaning brush,  FIG. 11A  being a side view of the modified cleaning brush, and  FIG. 11B  a front view the modified cleaning brush; 
         FIGS. 12A and 12B  are drawings illustrating a modification of the cleaning brush,  FIG. 12A  being a side view of the modified cleaning brush, and  FIG. 12B  a front view the modified cleaning brush; 
         FIG. 13  is a front view illustrating a modification of the cleaning brush; 
         FIG. 14  is a front view illustrating a modification of the cleaning brush; 
         FIGS. 15A and 15B  are drawings illustrating a modification of the cleaning brush,  FIG. 15A  being a side view of the modified cleaning brush, and  FIG. 15B  a front view the modified cleaning brush; 
         FIG. 16  is a schematic configuration drawing illustrating an image formation apparatus pertaining to another exemplary embodiment of the present invention; 
         FIG. 17  is a perspective view illustrating plural cleaning brushes, contact part moving devices, and components in the vicinity thereof which are used in the image formation apparatus as shown in  FIG. 16 ; and 
         FIG. 18A  is a perspective view illustrating the operation of moving the contact part between the cleaning brush and the charging roll in the longitudinal direction, and  FIG. 18B  is a front view of the cleaning brush and the charging roll. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinbelow, exemplary embodiments of an image formation apparatus pertaining to the present invention will be described with reference to the drawings. 
       FIG. 1  shows an image formation apparatus  1  of a first exemplary embodiment of the present invention. 
     This image formation apparatus  1  is a digital color printer, and image data which is sent from a reading device for an original document (illustration thereof is omitted), a personal computer, or the like, is sent to an image processing device  12  to be subjected to a prescribed image process. The image data which has been subjected to the prescribed image process by the image processing device  12  is converted into tone data of coloring materials for reproducing original documents, i.e., tone data of yellow (Y), magenta (M), cyan (C), and black (K), (each eight bits) by the same image processing device  12 , which, as described later, is sent to an exposure device  14  for image formation units  13 Y,  13 M,  13 C, and  13 K for respective colors of yellow (Y), magenta (M), cyan (C), and black (K). With this exposure device  14 , image exposure by a laser beam LB is performed according to the tone data of coloring materials for reproducing documents. 
     In the inside of the image formation apparatus  1 , the four image formation units  13 Y,  13 M,  13 C, and  13 K for yellow (Y), magenta (M), cyan (C), and black (K) are disposed in parallel manner in the horizontal direction with a predetermined space therebetween. These four image formation units  13 Y,  13 M,  13 C, and  13 K are all configured in the same manner, each of the image formation units is configured to include a photosensitive drum  15  which is rotationally driven; a charging roll  16  which uniformly charges a surface of this photosensitive drum  15 ; an exposure device  14  which exposes an image-light corresponding to a predetermined color on the surface of the photosensitive drum  15  for forming an electrostatic latent image; a developer unit  17  which develops the electrostatic latent image formed on the photosensitive drum  15  with toner of the predetermined color; and a cleaning device  18  which cleans the surface of the photosensitive drum  15 . 
     The exposure device  14  is configured commonly to the four image formation units  13 Y,  13 M,  13 C, and  13 K, and is configured such that, according to the tone data of respective coloring materials for reproducing original documents, four semiconductor lasers (not shown) are modulated to cause laser beams LB-Y, LB-M, LB-C, and LB-K to be emitted from these semiconductor lasers according to the tone data. The exposure device  14  may, of course, be individually configured for each of the plural image formation units. The laser beams LB-Y, LB-M, LB-C, and LB-K emitted from the above-mentioned semiconductor lasers are irradiated onto a polygon mirror (a multiple-face mirror)  19  through a f-θ lens (not shown), and deflect-scanned by this polygonal mirror  19 . The laser beams LB-Y, LB-M, LB-C, and LB-K deflect-scanned by the polygonal mirror  19  are scan-exposed onto the exposure position on the photosensitive drum  15  from slantwise lower side through an imaging lens and plural mirrors (not shown). 
     The exposure device  14  scan-exposes an image-light onto the photosensitive drum  15  from lower side, thus there is a possibility that, onto this exposure device  14 , the toner or the like may be dropped from the developer units  17  or the like of the four image formation units  13 Y,  13 M,  13 C, and  13 K which are located above, resulting in the exposure device  14  being contaminated. Therefore, the exposure device  14  is sealed at the surroundings thereof by a frame  20  in the shape of a rectangular parallelepiped, and on the top of the frame  20 , window parts  21 Y,  21 M,  21 C, and  21 K as shield members that are made of a transparent glass are provided in order to expose the four laser beams LB-Y, LB-M, LB-C, and LB-K onto the photosensitive drums  15  in the respective image formation units  13 Y,  13 M,  13 C, and  13 K. 
     From the image processing device  12 , image data of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) is sequentially outputted to the exposure device  14 , which is commonly provided for the image formation units  13 Y,  13 M,  13 C, and  13 K for the respective colors. The laser beams LB-Y, LB-M, LB-C, and LB-K emitted from the exposure device  14  according to the image data are scan-exposed onto the surface of the corresponding photosensitive drums  15  for formation of electrostatic latent images. The electrostatic latent images formed on the photosensitive drums  15  are developed by the developer units  17 Y,  17 M,  17 C, and  17 K as toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively. 
     The toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) that have been sequentially formed on the photosensitive drums  15  in the respective image formation units  13 Y,  13 M,  13 C, and  13 K are multiply transferred, by four primary transfer rolls  26 Y,  26 M,  26 C, and  26 K, onto an intermediate transfer belt  25  in the transfer unit  22  that is disposed above across the respective image formation units  13 Y,  13 M,  13 C, and  13 K. These primary transfer rolls  26 Y,  26 M,  26 C, and  26 K are disposed on the side of the rear face of the intermediate transfer belt  25 , corresponding to the photosensitive drums  15  of the respective image formation units  13 Y,  13 M,  13 C, and  13 K. To the primary transfer rolls  26 Y,  26 M,  26 C, and  26 K, a transfer bias power supply (not shown) is connected, and a transfer bias having a polarity opposite to a predetermined toner polarity (a positive polarity in the present exemplary embodiment) is applied at a predetermined timing. 
     The intermediate transfer belt  25  is wound around a drive roll  27  for driving the intermediate transfer belt  25 , a tension roll  24  for providing a tension for the intermediate transfer belt  25 , and a backup roll  28  for supporting the intermediate transfer belt from back side  25  in the secondary transfer section, with a constant tension, and is driven for circulation in a clockwise direction in the figure at a predetermined speed by the drive roll  27  which is rotationally driven by a motor (not shown). 
     The toner images of the respective colors of yellow (Y), magenta (M), cyan (C), black (K) that have been multiply transferred onto the intermediate transfer belt  25  are secondarily transferred onto a recording paper  30  as a sheet by a secondarily transfer roll  29  which is pressure contacted with the backup roll  28 , and the recording paper  30  to which the toner images of these respective colors have been transferred is conveyed to a fuser  31  which is located above. The secondarily transfer roll  29  is pressure contacted with the backup roll  28  at the side, and secondarily transfers the toner images of the respective colors onto the recording paper  30  conveyed upward from the lower side. The fuser  31  includes a heat roll  56  which is heated to a predetermined temperature, and a pressure roll  58  which is pressure contacted with this heat roll  56 . The recording paper  30  onto which the toner images of the respective colors have been transferred is subjected to a fixing process with heat and pressure in the pressure contact portion of the heat roll  56  and the pressure roll  58 , thereafter, the recording paper  30  is output onto an exit tray  33  provided on the top of the image formation apparatus  1  by an exit roll  32 . 
     The recording paper  30  of a predetermined size is once conveyed from a feed cassette  34  to a registration roll  38  for determining the position of the paper in the axial direction through a paper convey path  37  by a pickup roller  35  and a paper separation feeding roller pair  36 , and stopped. The paper convey path  37  for the fed recording paper  30  is directed upward in the vertical direction. The recording paper  30  supplied from the feed cassette  34  is fed out to the secondary transfer position of the intermediate transfer belt  25  by the registration roll  38  rotated at a predetermined timing. 
     In the image formation apparatus  1 , in a case of a double-sided copy of full color or the like, a recording paper  30  on one side of which an image is fixed is not output onto the exit tray  33  by the exit roll  32  as it is, but the convey direction of the recording paper  30  is switched by a switching gate (not shown) such that the recording paper  30  is conveyed to a convey unit for double-sided copy  40  through a paper convey roller pair  39 . In this convey unit for double-sided copy  40 , the recording paper  30  in a state of being inverted to be backside-up is conveyed by a convey roller pair (not shown) provided along a convey path  41  again to the registration roll  38 . Then, after an image being transferred and fixed on the back side of the recording paper  30 , the recording paper  30  is output onto the exit tray  33 . 
     In addition, the surface of the photosensitive drum  15  after the process of transferring the toner image having been completed is cleaned of the residual toner, the paper dust and the like by a cleaning device  18  to prepare for the subsequent image formation process. The cleaning device  18  is provided with a cleaning blade (not shown), and with this cleaning blade, the residual toner, the paper dust and the like on the photosensitive drum  15  are removed. 
     In addition, the surface of the intermediate transfer belt  25  after the process of transferring the toner image having been completed is cleaned of the residual toner, the paper dust and the like by a cleaning device  43  to prepare for the subsequent image formation process. The cleaning device  43  includes a cleaning brush  43   a  and a cleaning blade  43   b , and with these cleaning brush  43   a  and cleaning blade  43   b , the residual toner, the paper dust and the like on the intermediate transfer belt  25  are removed. 
     In the upper part of the inside of the image formation apparatus  1 , toner cartridges  44 Y,  44 M,  44 C, and  44 K which accommodate toner of yellow, magenta, cyan, and black are provided, respectively, for supplying the toners of predetermined colors to the developer units  17  of the respective colors. 
     In addition, at the side face (the left side face in  FIG. 1 ) of the image formation apparatus  1 , a manual feed tray  47  on which an optional sheet can be loaded is attached. On this manual feed tray  47 , a recording paper  52  as a sheet is put, and the recording paper  52  is fed by a feed roller  54  to be conveyed to the registration roll  38 . The recording paper  52  is different in type and size from the above-mentioned recording paper  30 . 
     As shown in  FIG. 2 , the photosensitive drum  15  is rotationally driven in the direction of arrow A (a counterclockwise direction) by a motor (not shown). In addition, the charging roll  16  is configured such that it is contacted with the surface of the photosensitive drum  15  to be rotated in the direction of arrow B, by being driven by (following) the rotation of the photosensitive drum  15 . In addition, under the charging roll  16  (on the side opposite to the photosensitive drum  15 ), a cleaning device  60  which cleans the surface of the charging roll  16  is provided. 
     In this cleaning device  60 , a cleaning brush  62  which is contacted with the surface of the charging roll  16  for cleaning it is provided. As shown in  FIGS. 4A and 4B , with the cleaning brush  62 , plural brush bristles  66  are planted on one side of a support member  64  which is folded at an obtuse angle, and the support member  64  is supported so as to be able to swing by a pivotal shaft  65  provided on the other side of the support member  64 . The pivotal shaft  65  is inserted into a long hole formed in a frame (not shown) in the vertical direction to be movable in the vertical direction. As shown in  FIG. 4B , a portion of the support member  64  on which the brush bristles  66  are planted is formed in the shape of a flat plate having an approximately uniform thickness along the longitudinal direction of the charging roll  16 . 
     On the back face side of the support member  64  (the side opposite to the charging roll  16 ), a contact part moving device  68  is provided. The contact part moving device  68  causes the cleaning brush  62  to be contacted with the charging roll  16  in a region shorter than the length in the longitudinal direction, and causes a contact part of the cleaning brush  62 , at which part the cleaning brush  62  contacts with the charging roll  16 , to be moved in the longitudinal direction of the charging roll  16 . As shown in  FIGS. 3A ,  3 B, and  3 C, the contact part moving device  68  includes two cam members  72 ,  74  on both sides of a shaft  70 , and in the end portion of the shaft  70 , a motor  78  which causes the shaft  70  to be rotated is provided. As shown in  FIG. 3B , the cam members  72 ,  74  are substantially in the shape of an ellipse, having the same profile, however, being attached to the shaft  70  with their phases being shifted (different) from each other. The drive of the motor  78  and the timing are controlled by a control section  80 . As the motor  78 , a stepping motor which is changeable in rotational speed is used. The cam members  72 ,  74  may be members having a circular cross section and a position of an axis of rotation (a shaft center) being shifted from a center thereof, that is, so-called, eccentric cams 
     The contact part moving device  68  is configured such that, by the cam members  72 ,  74  butting against the support member  64  respectively while being rotated, the amount of pressing the cleaning brush  62  against the charging roll  16  is changed so that the cleaning brush  62  is caused to be apart from or contacted with the charging roll  16 . 
     Next, the details of the charging roll  16  will be described. 
     In this charging roll  16 , on an electrically conductive shaft  16 A, an electrically conductive elastic layer and a surface layer are formed in that order as a charging layer  16 B. 
     The diameter of the charging roll  16  is 7 mm to 15 mm, and more preferably, from 8 mm to 14 mm, and the thickness of the charging layer  16 B is preferably from 2 mm to 4 mm. If the diameter of the charging roll  16  is more than or equal to 15 mm, the number of times of contacting with the external additive per given spot on the circumferential face are decreased and the number of times of discharging are decreased, thus although the contamination avoidability and the long-term stability in charging performance are excellent, there arises a need for consideration of the layout with the increase in diameter. If the diameter of the charging roll  16  is less than of equal to 7 mm, the image formation apparatus  1  can be advantageously made compact in size, but the number of times of contacting with the external additive per given spot on the circumferential face are increased and the number of times of discharging are increased. 
     Needless to say, this charging roll  16  is not limited to the following constitutions, provided that it has a prescribed charging performance. 
     As the material of the shaft  16 A, free-cutting steel, stainless steel, or the like, is used, and according to the required characteristic, such as slidability, the material and the surface treatment method are selected as appropriate, and a material having no electrical conductivity may be subjected to a general treatment, such as plating treatment, or the like, for providing conductivity. 
     The above-mentioned electrically conductive elastic layer constituting the charging layer  16 B of the charging roll  16  is made up of, for example, an elastic material having elasticity, such as rubber, or the like, and an electrically conductive agent for adjusting the resistance of the electrically conductive elastic layer, such as a carbon black, an ionic electrically conductive agent, or the like. Further, a material which can generally be added to rubber, such as a softener, a plasticizer, a curing agent, a vulcanizing agent, a vulcanization accelerator, an age resistor, and a filler, such as silica, calcium carbonate, or the like, may be added to the electrically conductive elastic layer as required. The electrically conductive elastic layer is formed by coating the circumferential face of the electrically conductive shaft  16 A with a mixture into which a material which is generally added to rubber is added. As the electrically conductive agent for adjusting the resistance value, material of which electron or an ion served as a charge carrier electric-conducts, such as a carbon black, an ionic electrically conductive agent or the like, which is mixed into a matrix material, can be dispersed in electrically conductive elastic layer. In addition, the above-mentioned elastic material may be a foaming material. 
     The elastic material constituting the above-mentioned electrically conductive elastic layer is formed by, for example, dispersing an electrically conductive agent into the rubber material. Examples of the rubber material include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylenepropylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-arylglycidyl ether copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber, natural rubber, and the like, and blended rubbers of these. Among these, silicone rubber, ethylenepropylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-arylglycidyl ether copolymer rubber, acrylonitrile-butadiene copolymer rubber, and blended rubbers of these are preferably used. These rubber materials may be those foamed or nonfoamed. 
     As the electrically conductive agent, an electronic electrically conductive agent or an ionic electrically conductive agent is used. Examples of electronic electrically conductive agent include impalpable powder of carbon blacks, such as ketjen black, acetylene black, and the like; pyrolytic carbon, graphite; various electrically conductive metals or alloys, such as aluminum, copper, nickel, stainless steel, and the like; various electrically conductive metal oxides, such as tin oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, tin oxide-indium oxide solid solution, and the like; insulating substances which surfaces have been subjected to a conductive treatment; and the like. In addition, examples of ionic electrically conductive agent include a perchlorate, a chlorate, and the like, such as tetraethyl ammonium, lauryl trimethyl ammonium, or the like; and a perchlorate, a chlorate, and the like, of an alkaline metal, an alkaline-earth metal, such as lithium, magnesium, or the like. 
     The above-mentioned surface layer constituting the charging layer  16 B is formed to prevent contamination due to a foreign matter, such as toner, or the like, and as the material of the surface layer, any of resin, rubber, and the like, may be used, with no particular restriction being given. Examples include polyester, polyimide, copolymer nylon, silicone resin, acrylic resin, polyvinyl butylal, ethylene tetrafluoroethylene copolymer, melamine resin, fluorine rubber, epoxy resin, polycarbonate, polyvinyl alcohol, cellulose, polyvinylidene chloride, polyvinyl chloride, polyethylene, ethylene vinyl acetate copolymer, and the like. Among these, from the view point of external additive contamination prevention, polyvinylidene fluoride, 4-ethylene fluoride copolymer, polyester, polyimide, and copolymer nylon are preferably used. 
     In addition, by adapting the above-mentioned surface layer to contain an electrically conductive material, the resistance value therefor can be adjusted. The electrically conductive material preferably has a particle diameter of 3 μm or under. In addition, as the electrically conductive agent for adjusting the resistance value, material of which electron or an ion served as a charge carrier electric-conducts, such as a carbon black, electrically conductive metallic oxide particle, an ionic electrically conductive agent or the like, which is mixed into a matrix material, can be dispersed in electrically conductive elastic layer. 
     In addition, for the above-mentioned surface layer, a fluorine-based or silicone-based resin can be used, and particularly it is preferable to be constituted by a fluorine-modified acrylate polymer. In addition, into the surface layer, fine particles may be added. Thereby, the surface layer is rendered hydrophobic, which acts so as to prevent foreign matters from being deposited onto the charging roll  16 . In addition, by adding nonconductive particles, such as alumina and silica ones, irregularities can be provided at the surface of the charging roll  16  in order to minimize the load in sliding on/abrasion with the photosensitive drum  15  for obtaining an improvement in mutual abrasion resistance between the charging roll  16  and the photosensitive drum  15 . 
     Next, the cleaning brush  62  will be described. 
     As the material of the support member  64  for the cleaning brush  62 , stainless steel, resin, or the like, is used. In addition, as the material of the brush bristles  66 , a resin, such as nylon, or the like, is used. 
     Next, the operation of the image formation apparatus  1  as configured above will be described. 
     When the cleaning operation is started, as shown in  FIG. 2 , the photosensitive drum  15  is rotated in the direction of arrow A, and the charging roll  16  which is contacted with the photosensitive drum  15  is rotated in the direction of arrow B, by being driven by (following) the rotation of the photosensitive drum  15 . In addition, the control section  80  drives the motor  78  to rotate the shaft  70  for rotating the cam members  72 ,  74 . 
     As shown in  FIGS. 5A and 5B , by rotating the cam members  72 ,  74  to the separating position, the cleaning brush  62  and the charging roll  16  are separated from each other. When the shaft  70  is rotated in a counterclockwise direction (the direction of the arrow) from this separating position, as shown in  FIGS. 6A and 6B , first, the cam member  72  which is on this side in  FIG. 6A  causes this side of the cleaning brush  62  to be contacted with the charging roll  16  to clean the charging roll  16 . At this time, the other side of the cleaning brush  62  is separated from the charging roll  16  (brought into the state as shown in  FIG. 6B ). In other words, the cleaning brush  62  is contacted with the charging roll  16  in the region shorter than the length in the longitudinal direction. Here, “this side” corresponds to the left side and the other side corresponds to the right side in  FIGS. 6B ,  7 B and  8 B and the like. 
     Then, as the shaft  70  is further rotated in a counterclockwise direction (the direction of the arrow), the contact part of the cleaning brush  62  with the charging roll  16  is moved from the this side to the other side, and soon, as shown in  FIGS. 7A and 7B , this side of the cleaning brush  62  in  FIG. 7A  is separated from the charging roll  16 , and the cam member  74  on the other side causes the other side of the cleaning brush  62  to be contacted with the charging roll  16  (brought into the state as shown in  FIG. 7B ). Thus, the contact part between the cleaning brush  62  and the charging roll  16  is moved from this side to the other side, thereby cleaning is carried out over the entire surface of the charging roll  16  in the axial direction. 
     Thereafter, the shaft  70  is further rotated in a counterclockwise direction (the direction of the arrow), and as shown in  FIGS. 8A and 8B , the cleaning brush  62  is separated from the charging roll  16 , thereby the cleaning operation is finished. 
     With such a method, the charging roll  16  is cleaned once in the axial direction by the cleaning operation of one time. However, the control section  80  may reversely turn the motor  78  in order to turn the shaft  70  in the reverse direction (in a clockwise direction) for operating the cleaning brush  62  from the state as shown in  FIGS. 7A and 7B  to the state as shown in  FIGS. 6A and 6B  so as to clean the charging roll  16  in reciprocating manner (in to-and-fro directions) along the axis (that is, the contact part between the cleaning brush  62  and the charging roll  16  is moved in to-and-fro directions). 
     In addition, the control section  80  may also control the directions of rotating of the shaft  70  by controlling of driving the motor  78  in order to repeat the operations of the cleaning brush  62  as shown in  FIGS. 6A and 6B  and as shown in  FIGS. 7A and 7B  plural times so that cleaning is performed more certainly before separating the cleaning brush  62  from the charging roll  16 . 
     In addition, the control section  80  can control the direction of rotating of the shaft  70  in the constant direction by rotating the motor  78  in the constant direction such that the operation of the cleaning brush  62  as shown in  FIGS. 6A and 6B , the operation of the cleaning brush  62  as shown in  FIGS. 7A and 7B , the state of the cleaning brush  62  as shown in  FIGS. 8A and 8B , the state of the cleaning brush  62  as shown in  FIGS. 5A and 5B , and again the operation of the cleaning brush  62  as shown in  FIGS. 6A and 6B  are repeated in that order so that cleaning is performed more certainly. 
     In addition, because both end portions of the charging roll  16  are easier to become dirty than the central portion thereof, the control section  80  may control the drive of the motor  78  to lower the rotational speed of the shaft  70  substantially when the cleaning brush  62  contacting with the ends of the charging roll  16 . Thereby, the moving speed of the contact part of the cleaning brush  62  can be lowered in the vicinity of the both ends of the charging roll  16 . 
     Next, modifications of the first exemplary embodiment of the cleaning device of the present invention will be described. The same members as those in the first exemplary embodiment will be provided with the same signs and numerals, and the duplicated descriptions are omitted. 
     As shown in  FIGS. 9A ,  9 B, and  9 C, as the contact part moving device  90  which moves the contact part between the charging roll  16  (see  FIG. 2 ) and the cleaning brush  62  (see  FIG. 2 ) in the longitudinal direction, a cam member  92  can be additionally provided between the cam members  72 ,  74  of the shaft  70 , in other words, in the central portion of the shaft  70 . As shown in  FIG. 9B , the cam member  92  is substantially in the shape of an ellipse, having the same profile as those of the cam members  72 ,  74 , however, the phases of the cam members  72 ,  92 ,  74  are shifted in the order of these, and the cam members  72 ,  92 ,  74  are mounted on the shaft  70 . That is, the phase of the cam member  92  is set between the phases of the cam members  72  and  74 . Thereby, even though the cleaning brush  62  (see  FIGS. 4A and 4B ) has a lower rigidity such that the central portion in the longitudinal direction would be deflected, it is suppressed that the contact pressure between the cleaning brush  62  (see  FIGS. 4A and 4B ) and the charging roll  16  (see  FIG. 2 ) in the central portion is weakened. The cam members  72 ,  74 ,  92  may be members having a circular cross section and a position of an axis of rotation (a shaft center) being shifted from a center thereof, that is, so-called, eccentric cams 
     As shown in  FIGS. 10A and 10B , as the contact part moving device  100  which moves the contact part between the charging roll  16  (see  FIG. 2 ) and the cleaning brush  62  (see  FIG. 2 ) in the longitudinal direction, the shaft  70  can be provided with a cam member  102  in the shape of a roll which has a cross section in the shape of an ellipse, and whose cross section is varied along the longitudinal direction. The cam member  102  is formed longer than the charging width (the maximum operating width) in the longitudinal direction of the charging roll  16 , and is formed such that the cross section thereof is gradually varied between one end  102 A and the other end  102 B in the longitudinal direction. Because such a cam member  102  can support the cleaning brush  62  (see  FIG. 2 ) over the axial direction, certainly contact state between the cleaning brush  62  (see  FIG. 2 ) and the charging roll  16  (see  FIG. 2 ) can be obtained. The cam member  102  may be a member having a circular cross section and a position of an axis of rotation (a shaft center) being changed along the longitudinal direction thereof, that is, so-called, a cylinder eccentric cam member. 
     As shown in  FIGS. 11A and 11B , in a cleaning brush  110 , it is possible that the central portion of the support member  112  in the longitudinal direction is projected toward the side of the charging roll  16  (see  FIG. 2 ) so as to have an angled geometry. On this portion of the angled geometry of the support member  112 , plural brush bristles  66  are planted. 
     As shown in  FIGS. 12A and 12B , in a cleaning brush  120 , it is possible that the central portion of the support member  122  in the longitudinal direction is projected toward the side of the charging roll  16  (see  FIG. 2 ) so as to have a circular-arc geometry. On this portion of the circular-arc geometry of the support member  122 , plural brush bristles  66  are planted. 
     As shown in  FIG. 13 , in a cleaning brush  130 , it is possible that the central portion of the support member  132  in the longitudinal direction is projected toward the side opposite to (the back side of) the charging roll  16  (see  FIG. 2 ) so as to have an angled geometry. On the flat portion, which is at the side opposite to the angled geometry, of the support member  132 , plural brush bristles  66  are planted. 
     As shown in  FIG. 14 , in a cleaning brush  140 , it is possible that the central portion of the support member  142  in the longitudinal direction is projected toward the side opposite to (the back side of) the charging roll  16  (see  FIG. 2 ) so as to have a circular-arc geometry. On the flat portion, which is at the side opposite to the circular-arc geometry, of the support member  142 , plural brush bristles  66  are planted. 
     As shown in  FIGS. 15A and 15B , a cleaning brush  150  is used. In the cleaning brush  150 , an heteromorphy roll  152 , which has a cross section in the shape of an ellipse and whose cross sectional shape is varied along the longitudinal direction, is provided around the shaft  151 , and on the circumferential face of the heteromorphy roll  152 , plural brush bristles  66  are planted. The heteromorphy roll  152  is formed longer than the charging width (the maximum operating width) in the longitudinal direction of the charging roll  16 , and the cross section thereof is gradually varied between one end  152 A and the other end  152 B in the axial direction. By rotating this cleaning brush  150 , the contact part between the cleaning brush  150  and the charging roll  16  (see  FIG. 2 ) can be moved in the longitudinal direction, and the cleaning brush  150  can be separated from the charging roll  16  (see  FIG. 2 ). Such a cleaning brush  150  can be used both as a contact part moving device and a cleaning brush. The heteromorphy roll  152  may be a roll having a circular cross section and a position of an axis of rotation (a shaft center) being changed along the longitudinal direction thereof. 
     Here, “cross section is varied” includes a case in which the cross sectional shapes is the same but is varied in orientation thereof, and a case in which the cross sectional shape itself is different along the longitudinal direction. 
     Next, an image formation apparatus which is another exemplary embodiment of the present invention will be described. The same members as those in the above-described exemplary embodiment will be provided with the same signs and numerals, and the duplicated descriptions are omitted. 
     As shown in  FIG. 16 , in this image formation apparatus  200 , at a lower portion of the charging roll  16  which is provided in each of the image formation units  13 Y,  13 M,  13 C, and  13 K, a cleaning device  202  which cleans the surface of the charging roll  16  is provided. As shown in  FIG. 16  and  FIG. 17 , this cleaning device  202  includes four cleaning brushes  62  for cleaning the surfaces of the four charging rolls  16 , respectively. Each of the cleaning brushes  62  is swingably supported by a pivotal shaft  65  provided in the support member  64 . 
     In addition, in this cleaning device  202 , a contact part moving device  204  which moves each contact part of the cleaning brush  62  with the charging roll  16  in the longitudinal direction is provided. This contact part moving device  204  includes two drive transmission members  206 ,  208  made of a sheet metal that, as shown in  FIG. 17 , are formed, being folded in a prescribed geometry, such that they bridge both end portions of the four cleaning brushes  62 , respectively. To each one end of the drive transmission member  206 ,  208 , one end of a plate-like part  212  is connected via a hinge part  210 , and at the other end of the plate-like part  212 , a cylindrical connection part  212 A is formed. In addition, at an outer side of the image formation unit  13 Y, a shaft  214  is disposed approximately in parallel with the cleaning brush  62 , and in this shaft  214 , a first crank part  214 A which is projected substantially in the shape of a letter U in a prescribed direction, and a second crank part  214 B which is projected substantially in the shape of a letter U in the direction perpendicular to that of the first crank part  214 A are formed. Here, it is not limited that projecting direction of the second crank part  214 B is perpendicular to that of the first crank part  214 A, it is possible that an angle between the projecting directions of the second crank part  214 B and the first crank part  214 A is an angle other than 90 degree. The connection part  212 A of the plate-like part  212  connected to the drive transmission member  206  is rotatably mounted to the first crank part  214 A, and the connection part  212 A of the plate-like part  212  connected to the drive transmission member  208  is rotatably mounted to the second crank part  214 B. At one end of the shaft  214 , a motor  216  is provided, and by driving the motor  216 , the shaft  214  is rotated in a constant direction. 
     In addition, in each of the drive transmission member  206 ,  208 , a horizontal lower plate part  220 A which is connected to the hinge part  210 ; a short inclined plate part  220 B which is provided, inclined slantwise upward from this lower plate part  220 A; an upper plate part  220 C which is horizontally provided at the end of this inclined plate part  220 B; and a short inclined plate part  220 D which is provided, inclined slantwise downward from this upper plate part  220 C are formed as a section for one image formation unit, and three sections whose structure are similar to that of the section are formed for the other three image formation units, respectively, such that the four sections are connected to one another over the four image formation units. In other words, the upper plate part  220 C is as a protruding part which is projected from the lower plate part  220 A. The upper plate part  220 C of each of the drive transmission member  206 ,  208  is butted against the support member  64  of the cleaning brush  62 , respectively, to press the cleaning brush  62  against the charging roll  16 . 
     The drive transmission members  206 ,  208  are disposed, bridging the image formation units  13 Y,  13 M,  13 C, and  13 K, and the drive transmission members  206 ,  208  are moved in the horizontal direction (in the direction orthogonal to the longitudinal direction of the charging roll  16 ) by the rotation of the shaft  214  with the drive transmission members  206 ,  208  being supported by a frame (not shown). At that time, because, in the first crank part  214 A of the shaft  214 , the connection part  212 A of the drive transmission member  206  is provided, while in the second crank part  214 B of the shaft  214 , the connection part  212 A of the drive transmission member  208  is provided, the drive transmission members  206 ,  208  can be moved in reciprocate manner with the respective phases being different from each other. In other words, as shown in  FIG. 18A , the drive transmission members  206 ,  208  are moved in reciprocate manner while the positions of the upper plate parts  220 C at this side and the other side of the cleaning brush  62  being different. The upper plate part  220 C is butted against the back side of the support member  64 , the cleaning brush  62  being pressed against the charging roll  16 . Thus, as shown in  FIGS. 18A and 18B , the timing of contact of the cleaning brush  62  with the charging roll  16  is shifted between this side and the other side. In addition, by the movement of the drive transmission members  206 ,  208 , the contact part between the cleaning brush  62  and the charging roll  16  is moved in the longitudinal direction, and the cleaning brush  62  is separated from the charging roll  16 . 
     In the above-described exemplary embodiments, the cleaning brush  62  for cleaning the charging roll  16  is used, however, the present invention is not limited to this configuration. For example, as the cleaning member, a cleaning pad including a sponge made up of a foamed resin may be used in place of the cleaning brush. 
     In the above-described exemplary embodiments, the cleaning device is one which cleans the charging roll  16 , however, the cleaned object (an element to be cleaned) is not limited to the charging roll  16 . For example, if the element to be cleaned is one which is rotatable, such as a transfer roll, the cleaning device of the present invention is applicable thereto. 
     The image formation apparatus  1 ,  200  in the above-mentioned exemplary embodiments is configured to arrange the image formation units for yellow, magenta, cyan, and black side by side along the moving direction of the intermediate transfer belt, however, the present invention is not limited to this configuration. For example, even if the image formation apparatus is one which, using a rotary developer unit, in which developer units of four colors are arranged repetitively, forms a toner image on the photosensitive drum four times (four cycles), the present invention is applicable thereto. 
     Hereinbelow, the configurations and the effects thereof in the above-described modifications of the exemplary embodiment pertaining to the present invention will be described. 
     1) In the cleaning brush  110 , the central portion of the support member  112  in the longitudinal direction is projected toward the side of the charging roll  16  so as to have an angled geometry. On this portion of the angled geometry of the support member  112 , plural brush bristles  66  are planted. Thus, at the time of cleaning in the vicinity of the central portion of the charging roll  16  (see  FIG. 2 ), it can be suppressed that the length of the contact part between the cleaning brush  110  and the charging roll  16  (see  FIG. 2 ) is increased resulting in an increase in load. 
     2) In the cleaning brush  120 , the central portion of the support member  122  in the longitudinal direction is projected toward the side of the charging roll  16  (see  FIG. 2 ) so as to have a circular-arc geometry. By using such the support member  122 , the degree of opening of the brush bristles  66  is rendered uniform over the longitudinal direction, therefore which eliminates the possibility that the brush bristles may be opened in the summit portion (the central portion in the longitudinal direction) resulting in the cleaning capacity being nonuniform, as would be happened when the support member having an angled geometry is used.