Patent Publication Number: US-8989638-B2

Title: Developer carrying device, development device and image forming apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is related to, claims priority from and incorporates by reference Japanese Patent Application No. 2012-074602, filed on Mar. 28, 2012. 
     TECHNICAL FIELD 
     The present invention relates to an image forming apparatus that uses an electrographic method, such as a printer, a photocopy apparatus and the like, a development device forming a developer image and a developer carrying device that are included in the image forming apparatus. 
     BACKGROUND 
     In a conventional development device, a surface of a photosensitive drum evenly charged by a charge device is exposed by an exposure device to form an electrostatic latent image. And then, the electrostatic latent image is developed by the development device to form a toner image as a developer image on the photosensitive drum. After that, the toner image is transferred to a sheet, and is fixed on the sheet. Thereby, an image is formed on the sheet. At this time, in the development device, toner supplied by a toner cartridge is supplied by a supply roller to a development roller. An even toner layer is formed on the development roller with a restriction blade to develop the toner image on the photosensitive drum. During the development, the toner that remains on the development roller is collected with a toner collection roller, and is scraped off the toner collection roller with a toner collection blade (see JP Laid-Open Patent Application No. 2011-197219, columns 0014-0018,  FIG. 2 , for example). 
     However, in the conventional art, while the collection toner scraped off the toner collection roller is mixed with new toner supplied from the toner cartridge by an agitation member of the development device, toner that accumulates in the vicinity of the development roller exists. The collection toner is unnecessarily damaged, and a charging characteristic thereof deteriorates in comparison with the new toner. When the collection toner is insufficiently mixed with the new toner, portion having a high proportion of the collection toner occurs. Therefore, there is a problem that detects of the developer image such as fog and blur occur. 
     An objection of the present invention is to improve image quality of the developer image to solve such a problem. 
     SUMMARY 
     Accordingly, a developer carrying device disclosed in the application includes a first developer containing part configured to contain developer, a first rotational member arranged in the first developer containing part, a second developer containing part arranged side by side with the first developer containing part, a second rotational member arranged in the second developer containing part, an opening part formed between the first developer containing part and the second developer containing part, and a restriction part arranged between the first rotational member and the second rotational member. 
     According to the present invention, an effect that the image quality of the developer image is improved is obtained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side diagram of a configuration of a development device according to a first embodiment. 
         FIG. 2  is a schematic side diagram of a configuration of a printer according to a first embodiment. 
         FIG. 3A  is an enlarged diagram of a main part of the configuration of the development device according to the first embodiment.  FIG. 3B  is a further enlarged diagram around agitation bar  15 . 
         FIG. 4  is a perspective view of an agitation bar according to the first embodiment. 
         FIG. 5  is explanatory diagrams illustrating the agitation bar and a backflow prevention member according to the first embodiment. 
         FIG. 6  is a schematic side diagram of a configuration of a development device according to a second embodiment. 
         FIG. 7A  is an enlarged diagram of a main part of a configuration of the development device according to the second embodiment.  FIG. 7B  is a further enlarged diagram around carrying roller  41 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of a developer carrying device, a development device and an image forming apparatus according to the present invention are explained below with reference to the drawings. 
     First Embodiment 
       FIG. 2  is a schematic side diagram of a configuration of a printer according to a first embodiment. 
     In  FIG. 2 , an image forming apparatus  1  is a monochrome printer that includes a development unit  61  as a development device and uses an electrographic method. A sheet feeding tray  23  is installed to the image forming apparatus  1 . The sheet feeding tray  23  accommodates recording sheets  25  as recording mediums therein. A hopping roller  33  and registration rollers  31  are arranged in the image forming apparatus  1 . The hopping roller  33  feeds the recording sheet  25  from the sheet feeding tray  23 . The registration rollers  31  corrects skew of the fed recording sheet  25 , and carries to a later-discussed image forming part. 
     In addition, the development unit  61  as an image forming part is arranged in the image forming apparatus  1 . The development unit  61  forms an image made of toner as developer. An LED (Light Emitting Diode) head  53  and a transfer roller  26  are arranged in the image forming apparatus  1 . The LED head  53  is adjacent to the development unit  61 , and selectively irradiates the surface of a photosensitive drum  51  in the development unit with light based on image data to form an electrostatic latent image on the surface of the photosensitive drum  51 . The transfer roller  26  is adjacent to the photosensitive drum  51 , and transfers a toner image formed on the photosensitive drum  51  onto the recording sheet  25 . The fed recording sheet  25  is carried in a direction indicated by an arrow in  FIG. 2 . 
     Furthermore, a fuser device  30  and ejection rollers  32  are arranged in the image forming apparatus  1 . The fuser device  30  fixes the toner image, which has been transferred by the transfer roller  26  and formed on the recording sheet  25 , on the recording sheet  25  by applying heat and pressure. The recording sheet  25  on which the toner image has been fixed passes the fuser device  30 . The ejection rollers  32  carry and eject the recording sheet  25  on a stacker  35  on which the recording sheets  25  pile. 
       FIG. 1  is a schematic side diagram of a configuration of the development device according to the first embodiment.  FIG. 3A  is an enlarged diagram of a main part of the configuration of the development device according to the first embodiment.  FIG. 3B  is a further enlarged diagram around agitation bar  15 . 
     In  FIGS. 1 and 3 , the development unit  61  includes a development roller  8  as a developer carrier, a supply roller  9  as a developer supply member and a collection roller  11  as a developer collection member, and is a development device that carries the developer collected by the collection roller  11  to the development roller  8  side. The development roller  8  supplies the toner on the photosensitive drum  51  as an image carrier. The photosensitive drum  51  carries the toner image as a developer image. The supply roller  9  supplies the toner on the development roller  8 . The collection roller  11  collects the toner from the development roller  8 . 
     To discuss in detail, the development unit  61  is configured by the photosensitive drum  51  as the image carrier, a charging roller  52 , the development roller  8  as the developer carrier, the supply roller  9  as the developer supply member, a subsidiary supply roller  14 , a first restriction blade  13 , a second restriction blade  10 , the collection roller  11  as the developer collection member, a collection blade  12  as a developer removal member, an agitation bar  15  as a first rotational member, an agitation bar  16  as a second rotational member, a backflow prevention member  18  as a restriction part, a toner containing part  21  as a developer storage part, a toner cartridge  19  and a agitation bar  17 . The charging roller  52  supplies electric charges on the surface of the photosensitive drum  51  to charge the surface of the photosensitive drum  51 . The development roller  8  is arranged to contact the surface of the photosensitive drum  51 . The supply roller  9  is arranged to keep a slight space between the supply roller  9  and the development roller  8 . The subsidiary supply roller  14  attaches the toner to the supply roller  9 . The first restriction blade  13  is arranged so that a front edge part thereof abuts on the supply roller  9 . The second restriction blade  10  is arranged so that a front edge part thereof abuts on the development roller  8 . The collection roller  11  is arranged to contact the development roller  8 . A front edge of the collection blade  12  abuts on the collection roller  11 , and the collection blade  12  scrapes the collection toner attached to the surface of the collection roller  11 . The agitation bar  15  faces the collection roller  11  in the vicinity of the collection roller  11 , and is arranged between the collection blade  12  and the subsidiary supply roller  14 . The agitation bar  16  is arranged in the vicinity of the subsidiary supply roller  14  and at a position in which the agitation bar  16  faces the agitation bar  15 . The backflow prevention member  18  is arranged between the agitation bar  15  and the agitation bar  16 , and inhibits backflow of the toner in a direction from the agitation bar  16  side to the agitation bar  15 . The toner cartridge  19  is arranged above the subsidiary supply roller  14 , and refills new toner. The agitation bar  17  is provided between the subsidiary supply roller  14  and the agitation bar  16 . 
     The agitation bar  15  as the first rotational member is arranged between the collection roller  11  as the developer collection member and the supply roller  9  as the developer supply member. The agitation bar  16  as the second rotational member is arranged between the agitation bar  15  and the supply roller  9 . The backflow prevention member  18  as the restriction part is arranged between the agitation bar  15  and the agitation bar  16 . 
     The agitation bar  15  carries the toner collected by the collection roller  11  to the agitation bar  16  side by rotating. The agitation bar  16  carries the toner carried by the collection roller  15  to the supply roller  9  side by rotating. The backflow prevention member  18  is arranged between the first toner containing part  21   a  (first developer containing part) and a second toner containing part  21   b  (second developer containing part). The first toner containing part  21   a  contains the toner collected by the collection roller  11 . The second toner containing part  21   b  contains the toner carried from the first toner containing part  21   a  by the agitation bar  15 . The backflow prevention member  18  prevents the toner contained in the second toner containing part  21   b  from flowing into the first toner containing part  21   a.    
     The first toner containing part  21   a  that retains the collection toner is formed of an outer circumference of the collection roller  11 , an outer circumference of the collection blade  12 , a bottom surface  22   a  of a frame  22  of the development unit  61 , an outer circumference of the backflow prevention member  18  and an outer circumference of the first restriction blade  13  as illustrated by the dotted hatch part in  FIG. 3A . 
     In addition, the second toner containing part  21   b  that retains unused toner (new toner) and the collection toner carried from the first toner containing part  21   a  is formed of an outer circumference of the subsidiary supply roller  14 , an outer circumference of the supply roller  9 , an outer circumference of the first restriction blade  13 , an outer circumference of the backflow prevention member  18 , and the bottom surface  22   a  of the frame  22  of the development unit  61  and a side surface  22   b  as illustrated by the solid hatch part in  FIG. 3A . 
     The first toner containing part  21   a  communicate with the second toner containing part  21   b  through an opening part  27  formed between the bottom surface  22   a  of the frame  22  of the development unit  61  and the backflow prevention member  18 . The toner is sent and received through the opening part  27 . 
     The agitation bar  15  is arranged in a region of the first toner containing part  21   a . The agitation bar  16  is arranged in a region of the second toner containing part  21   b . The agitation bar  15  and the agitation bar  16  rotate in directions indicated by the respective arrows in  FIGS. 1 and 3 , carry the collection toner retained in the first toner containing part  21   a  to the second toner containing part  21   b  in order to prevent the collection toner collected by the collection roller  11  from accumulating in the vicinity of the development roller  8 . 
     Furthermore, the development unit  61  includes a photosensitive body cleaning device  56 . The photosensitive body cleaning device  56  scrapes and disposes the toner that has not been transferred and remains on the photosensitive drum  51 . 
     A developer carrying device is configured by the first toner containing part  21   a , the agitation bar  15 , the second toner containing part  21   b , the agitation bar  16 , the opening part  27  and the backflow prevention member  18 . 
     The bottom surface  22   a  that is a part of frame  22  has a first surface  22   a   1 , which faces the agitation bar  15 , and a second surface  22   a   2 , which faces the agitation bar  16 . Herein, the two surfaces  22   a   1  and  22   a   2  are not arranged on a single plane, but arranged with a gap. Thereby, there is a ridge line  22   a   3  therebetween. A region  22   a   11  of the first surface  22   a   1  in the vicinity of the ridge line  22   a   3  is formed along the outer surface of the agitation bar  15 . 
     The photosensitive drum  51  is rotatably driven in a direction indicated by an arrow in  FIGS. 1 and 3  by a drum drive gear (not illustrated). The drum drive gear is rotatably driven by a drive motor (not illustrated). The charging roller  52  is rotatably driven in a direction indicated by an arrow in  FIG. 1  by a driving power transmitted by friction between the charging roller  52  and the surface of the photosensitive drum  51 . The development roller  8  is rotatably driven in a direction indicated by an arrow in  FIGS. 1 and 3  by a driving power transmitted through gears from the photosensitive drum  51 . The supply roller  9  is rotatably driven in a direction indicated by an arrow in  FIGS. 1 and 3  by a driving power transmitted through an idler gear from the development roller  8 . The subsidiary supply roller  14  is rotatably driven in a direction indicated by an arrow in  FIGS. 1 and 3  by a driving power transmitted through gears from the photosensitive supply roller  9 . The collection roller  11  is rotatably driven in a direction indicated by an arrow in  FIGS. 1 and 3  by a driving power transmitted through an idler gear from the supply roller  9 . 
     Rotation shafts of the agitation bar  15 , the agitation bar  16  and the agitation bar  17  are arranged in parallel to each other. The agitation bar  15  and the agitation bar  16  are rotatably driven in a direction indicated by an arrow in  FIGS. 1 and 3  by a driving power transmitted through idler gears from the collection roller  11 , for example. The agitation bar  17  is rotatably driven in a direction indicated by an arrow in  FIGS. 1 and 3  by a driving power transmitted through gears from the subsidiary supply roller  14 . 
     Here, the rotational directions of the agitation bar  15  and the agitation bar  16  are the opposite direction from the rotational direction of the collection roller  11 . However, the directions are not limited to the opposite direction, but may be the same direction as the rotational direction of the collection roller  11  in the present embodiment. Note that it is necessary that the rotational directions of the agitation bar  15  and the agitation bar  16  are the same direction from each other to smoothly carry the toner. 
     In addition, the development roller  8  is rotated in a direction with the rotation of the rotation of the photosensitive drum  51  at a circumferential speed ratio of 1.21 times relative to the photosensitive drum  51 . The toner supplying roller  9  is rotated in a direction with the rotation of the rotation of the development roller  8  at a circumferential speed ratio of 1.25 times relative to the development roller  8 . The subsidiary supply roller  14  is rotated in a direction with the rotation of the rotation of the supply roller  9  at a circumferential speed ratio of 0.92 times relative to the supply roller  9 . The collection roller  11  is rotated in a direction with the rotation of the rotation of the development roller  8  at a circumferential speed ratio of 0.98 times relative to the development roller  8 . Note that the circumferential speed ratios are not limited those described above. 
     Next, materials and configurations of respective parts are explained below with reference to  FIGS. 1 ,  4  and  5 . 
     The toner used in the present embodiment is made as follows: toner particles are produced by an emulsion polymerization method; styrene-acrylic copolymer resin, colorant and wax are mixed; such a mixture is aggregated to produce the toner particles; and silica, titanium oxide fine particles are added to the toner particles and mixed by a mixer, for example. The toner is formed to have an average particle size of 6 μm, for example. The emulsion polymerization method represents a method for producing a toner particle as follows: a primary particle of a polymer as blinding resin for the toner is produced in water solvent; colorant emulsified by emulsifying agent (surface active agent) is mixed with the solvent used for primary particle production; wax, charge control agent, and the like are mixed as may be needed; and such a mixture is aggregated to produce the toner particles in the solvent. The toner particles are removed from the solvent, washed and dried, so that an unnecessary solvent component and a by-product component are removed from the toner particle. 
     Here, the styrene-acrylic copolymer resin is generated from styrene, acrylic acid, and methylmethacrylate. The colorant includes the carbon black used as black, pigment yellow 74 used as yellow, pigment red 238 used as magenta and pigment blue 15:3 used as cyan. Furthermore, the wax includes stearyl stearate used as high-class fatty acid ester wax. 
     The photosensitive drum  51  is formed of an electric charge generation layer having a film thickness of 0.5 μm and an electric charge transportation layer having a film thickness of 18 μm provided on an aluminum tube having a thickness of 0.75 mm and an outside diameter of 30 mm, for example. The electric charge generation layer is preferably formed of an electric charge generation material made of selenium, selenium alloy, a selenium arsenic compound, cadmium sulfide, zinc oxide, other inorganic photoconductive material, or various organic pigment/dye such as phthalocyanine, azo color, quinacridon, polycyclic quinone, pyrylium salt, thiapyrylium salt, indigo, thioindigo, anthanthrone, pyranthrone, and cyanine, for example. 
     In addition, the electric charge transportation layer is preferably formed of an electric charge transportation material made of aniline derivative, a hydrazone compound, aromatic amino-derivative, stilbene derivative, or a heterocyclic compound such as carbazol, indole, imidazole, oxazole, pyrazole, pyrazoline, thiadiazole and the like, or an electron-donating material such as a polymer including a group made by combination of such substances or materials in a main chain or a side chain, for example. 
     The charging roller  52  is a device that uniformly charges the surface of the photosensitive drum  51 . The charging roller  52  is formed of a conductive member as a shaft made of stainless steel and the like and a conductive elastic layer made of epichlorohydrin and the like, for example. The charging roller  52  is arranged in contact with an outer circumferential surface of the photosensitive drum  51 . 
     The LED head  53  is an exposure device that selectively exposes the uniformly charged surface of the photosensitive drum  51  to light thereof to form an electrostatic latent image pattern on the surface of the photosensitive drum  51 . The LED head  53  is configured from LED elements, LED drive elements, and a lens array. The LED head  3  is arranged at a position in which the light radiated by the LED elements forms an image on the surface of the photosensitive drum  51 . 
     The development roller  8  is configured by a conductive shaft (core) made of, for example, a steel use machinerbility (SUM) material, an elastic layer provided on the conductive shaft in such a manner as to be in a roll shape, and a surface layer covering the elastic layer. The development roller  8  is arranged to contact the outer circumferential surface of the photosensitive drum  51 . The elastic layer is made of urethane rubber or silicone rubber. The surface layer is formed by processing a surface of the elastic layer with urethane solution, or by applying acrylic resin, acrylic-fluoro copolymer resin on the surface of the elastic layer. When the surface layer is formed of the acrylic resin, acrylic-fluoro copolymer resin, carbon black is blended in the acrylic resin to impart the conductivity to the surface layer. Herein, one part by weight of the carbon black is blended to one hundred parts by weight of the acrylic resin. 
     The supply roller  9  is a round bar or a pipe made of aluminum or stainless steel, for example. Surface roughness Ra of the surface of the supply roller  9  is adjusted to be Ra=1.6 or less by blast process or polish process. The subsidiary supply roller  14  is formed of a conductive shaft (core) made of, for example, a SUM material, and an elastic layer. The supply roller  9  is arranged to contact the outer circumferential surface of the supply roller  9 . The elastic layer is a conductive silicone rubber foam layer or a conductive urethane rubber foam layer. When an elastic layer having a semi-conductive property is used, acetylene black and carbon black are added, for example. 
     The first restriction blade  13  is configured by a conductive rubber blade or a conductive resin film. The first restriction blade  13  is arranged so that a front edge of the blade abuts on the surface of the supply roller  9  in a trail direction. The second restriction blade  10  is formed of a SUS material having a thickness of 0.08 mm, for example. The second restriction blade  10  includes a contact part that contacts the development roller  8 , and the contact part undergoes a bending process to form a curvature part having a curvature radius R of 0.2 mm. The second restriction blade  10  has a linear pressure of 30 gf/cm to the development roller  8 . Note that the curvature radius R and the linear pressure of the restriction blade  10  are not limited to the values described above, but is adjustable according to the charge amount of the toner. 
     The collection roller  11  is made of a conductive body that is formed by nickel plating on a SUM material, for example. The collection roller  11  is arranged to contact the outer circumferential surface of the development roller  8 . When the collection roller  11  is made of metal, a load to the development roller  8  is minimized. In addition, a degree of smoothness of the surface of the collection roller  11  increases to reduce a friction coefficient of the surface of the collection roller  11 . Thereby, the toner is easily scraped off when the toner attached to the surface of the collection roller  11  is scraped off with the collection blade  12 . The collection roller  11  is configured by metal in the present embodiment. However, the collection roller  11  is not limited to metal, but is also configured by a member having a conductive property, a high degree of smoothness and an excellent durability. 
     The collection blade  12  is configured by, for example, a rubber blade. The collection blade  12  is arranged so that a front edge of the rubber blade abuts on the surface of the collection roller  11  in a counter (opposite) direction from the rotational direction of the collection roller  11 . 
     The agitation bar  15 , agitation bar  16  and agitation bar  17  are configured to be a rod-shaped member that is a stainless shaft bended in a crank shape. For example, as illustrated in  FIG. 4 , a crank part  15   b  rotates around a rotation center  15   a  in the agitation bar  15 . The agitation bar  15  agitates and carries the toner. In addition, the agitation bar  16  has a same shape as the agitation bar  15 , rotates, agitates and carries the toner in the same manner as the agitation bar  15 . As shown in  FIG. 4 , the rotation centers  15   a  and  16   a , which are positioned at the both ends, are arranged on an axis. The crank parts  15   b  and  16   b  are arranged at a place that is offset with a gap Lb from the axis. The degree of offset can be set flexibly considering features of materials, scale of the device etc. For a general sized MPF, the gap is preferably within 0.05 mm to 2.0 mm. 
     The backflow prevention member  18  is formed of a film member, for example, a polyester film having a thickness of 0.2 mm, which extends in a direction parallel to the rotation shafts of the agitation bar  15 , the agitation bar  16  and the agitation bar  17 . As illustrated in  FIG. 5 , one end as a fixed end  18   b  of the backflow prevention member  18  is affixed on a holder of the first restriction blade  13  on the opposite side from a bottom surface  22   a  (one surface of the first toner containing part  21   a ) with a double-faced tape and the like. The other end (free end  18   a ) of the backflow prevention member  18  is arranged in the vicinity of a line L 1  that links the rotation shaft  15   a  of the agitation bar  15  to the rotation shaft  16   a  of the agitation bar  16 . The free end  18   a  is in contact with the line L 1 , or is arranged to extend to a position in which the free end  18   a  protrudes into the line L 1 . The imaginary line L 1  is defined as an imaginary linkage line. Accordingly, an opening part  27  is formed between the free end  18   a  and the bottom surface  22   a  of the first toner containing part  21   a . Toner carried in a direction indicated by an arrow A in  FIG. 5  by the agitation bar  15  passes through the opening part  27 . Further, the backflow prevention member  18  is arranged at a position, in a rotation region of the agitation bar  16 , that faces a region S 18  with respect to a toner carrying direction (or arrow A direction). The region S 18  is defined by a rotation area from the second toner containing part  21   b  toward the first toner containing part  21   a . The opening part  27  is arranged at another position, in a rotation region of the agitation bar  15 , that faces a region S 27  with respect to the toner carrying direction (or arrow A direction). The side S 27  is defined by a rotation area from the first toner containing part  21   a  toward the second toner containing part  21   b . The regions S 18  and  27  are illustrated in  FIG. 5 . 
     In order not to interrupt the agitation bar  15  when the agitation bar  15  presses the toner in the direction of the agitation bar  16 , the free end  18   a  of the backflow prevention member  18  is attached to the agitation bar  16  side while the fixed end  18   b  of the backflow prevention member  18  is attached to the agitation bar  15  side. The backflow prevention member  18  inclines with respect to the line L 1  that links the rotation shaft  15   a  of the agitation bar  15  to the rotation shaft  16   a  of the agitation bar  16 . There is an acute angle α between the backflow prevention member  18  (film) and the line L 1 . 
     In order to prevent the backflow of the toner in a direction from the agitation bar  16  to the agitation bar  15 , the free end  18   a  (front edge) of the backflow prevention member  18  needs to extend from a tangential line L 2  that links a rotational outer circumference of the agitation bar  15  and a rotational outer circumference of the agitation bar  16  to the line L 1  side that links the rotation shaft  15   a  of the agitation bar  15  to the rotation shaft  16   a  of the agitation bar  16 . 
     As illustrated in  FIG. 5 , the agitation bar  16  is provided in a downstream side of the agitation bar  15  in the direction indicated by the arrow A in  FIG. 5  in which the toner is carried. The backflow prevention member  18  as the restriction part is provided between the agitation bar  15  and the agitation bar  16 . The backflow prevention member  18  is arranged a position in which the backflow prevention member  18  restricts the carriage of the toner due to an operation in an opposite direction from the direction in which the agitation bar  16  carries the toner. The agitation bars  15 ,  16  are provided in a downstream side in the direction in which the collection roller  11  carries the toner in the present embodiment. 
     In addition, the agitation bar  15  rotates in the same direction (counterclockwise direction) as the agitation bar  16 . The backflow prevention member  18  is formed to extend from the vicinity of the line L 1  that links the rotation shaft  15   a  of the agitation bar  15  to the rotation shaft  16   a  of the agitation bar  16  to the outer tangential line L 2  on the opposite side from the bottom surface  22   a . The bottom surface  22   a  restricts the carriage of the toner to the opposite side from the direction in which the toner is carried by the agitation bar  16 . Thereby, the toner is carried in the direction indicated by the arrow A in  FIG. 5  from the first toner containing part  21   a  to the second toner containing part  21   b.    
     The backflow prevention member  18  is formed of a film member, and the one end of the backflow prevention member  18  is the free end  18   a . Thereby, the backflow prevention member  18  oscillates. Accordingly, there is an effect that the aggregation of the toner in the vicinity of the backflow prevention member  18  reduces. 
     The quality of material and the thickness of the backflow prevention member  18  are not limited to those of a film, but may be those of a metal plate, a resin molded article and the like. 
     The transfer roller  26  is, for example, formed of a conductive shaft and a foam elastic member having a conductive property. The photosensitive body cleaning device  56  is configured by, for example, a rubber blade, and is arranged so that a front edge of the rubber blade abuts on the surface of the photosensitive drum  51 . 
     A function of the configurations discussed above is explained with reference to  FIGS. 1 to 3 . 
     The surface of the photosensitive drum  51  of the development unit  61  is uniformly charged by the charging roller  52  to which the charge voltage is applied by a power source device (not illustrated). The LED head  53  emits light in accordance with image data, and selectively exposes the uniformly charged surface of the photosensitive drum  51  to the light thereof, thereby forming the electrostatic latent image on the surface of the photosensitive drum  51 . In the meantime, the subsidiary supply roller  14  rotates while the subsidiary supply roller  14  scoops up and carries the toner on the sponge surface thereof and in cell openings thereon. The subsidiary supply roller  14  arrives at an abutting part at which the subsidiary supply roller  14  abuts on the supply roller  9 . A direct current bias voltage of −300V, an alternating current bias voltage at 600V peak-to-peak and a rectangle wave frequency of 2 kHz are applied to the supply roller  9 . 
     Accordingly, alternating current bias voltage within the range of 0V through −600V is applied to the supply roller  9 . A bias voltage of −1 kV through −4 kV is applied to the subsidiary supply roller  14  so that a current of approximately 10 μA flows from the supply roller  9  to the subsidiary supply roller  14 . Therefore, negative electric charges passes the toner between the subsidiary supply roller  14  and the supply roller  9 , and moves at the abutting part from the subsidiary supply roller  14  to the supply roller  9 . At this time, the toner is charged and attached to the surface of the supply roller  9  by image a function and an image force of an electric field between the subsidiary supply roller  14  and the supply roller  9 . 
     The toner attached to the supply roller  9  is charged and thinned by the first restriction blade  13  to which the same bias voltage as the supply roller  9  is applied. The thinned toner on the supply roller  9  arrives at a facing part at which the supply roller  9  faces the development roller  8  by the rotation of the supply roller  9 . A direct current bias voltage of −200V is applied to the development roller  8  and a development blade  10 . Accordingly, since an electric field of +200V through −400V is formed as an oscillating electric field between the supply roller  9  and the development roller  8 , the toner on the surface of the supply roller  9  soars in a direction of the development roller  8  and is carried on the surface of the development roller  8 . After the toner is thinned by the development blade  10 , the toner corresponds to the electrostatic latent image formed on the photosensitive drum  51  and is developed. 
     In the meantime, the recording sheet  25  accommodated in the sheet feeding tray  23  is picked up from the sheet feeding tray  23  by the hopping roller  33 . After the skew of the recording sheet  25  is corrected by the registration rollers  31 , the recording sheet  25 , and is carried to the vicinity of the transfer roller  26 . And then, when the toner image on the surface of the photosensitive drum  51  obtained by the development reaches the vicinity of the transfer roller  26  by the rotation of the photosensitive drum  51 , the toner image on the surface of the photosensitive drum  51  is transferred onto the recording sheet  25  by the transfer roller  26  to which a voltage is applied by the power source device (not illustrated). 
     Next, the recording sheet  25  including the toner image formed on the surface thereof is carried to the fuser device  30  by the rotation of the transfer roller  26 . The toner image on the recording sheet  25  is fused and fixed on the recording sheet  25  when the fuser device  30  applies a pressure to and heat the recording sheet  25 . Furthermore, the recording sheet  25  is ejected on the stacker  35  by the carrying rollers  32 . The operation of the image formation performed by the image forming apparatus  1  is completed. 
     In a step of the image formation described above, in order to collect the development residual toner that has remained on the surface of the development roller  8  without moving to the photosensitive drum  51  during the development, the collection roller  11  is connected to ground through the resistance so that a collection voltage whose polarity is opposite to the charge polarity of the toner is applied to the collection roller  11 . The development residual toner moves onto the collection roller  11 . Furthermore, the development residual toner is scraped off the collection roller  11  by the collection blade  12 . The residual toner scraped off the collection roller  11  is agitated by the rotation operation of the agitation bar  15 . One part of the toner passes below the backflow prevention member  18  and moves to the agitation bar  16  side. While the toner that has moved to the agitation bar  16  side is agitated by the rotation operation of the agitation bar  16 , one part of the toner moves into the second toner containing part  21   b , is mixed into toner in the second toner containing part  21   b  by the agitation bar  17 , is attached to the subsidiary supply roller  14  again, and moves to the supply roller  9  and the development roller  8 . 
     At this time, the toner is sent and received between the agitation bar  15  and the agitation bar  16 . The flow of the toner that moves from the agitation bar  16  to the agitation bar  15  side is restricted by the backflow prevention member  18 . Furthermore, as the toner collected from the development roller  8  gradually increases, a pressure of the toner in the first toner containing part  21   a  increases. Therefore, a movement amount Ta of the toner that moves in the direction from the agitation bar  15  to the agitation bar  16  is more than a movement amount Tb of the toner that moves in the direction from the agitation bar  16  to the agitation bar  15  with the rotation of the agitation bar  16 . The relationship between the movement amount Ta and the movement amount Tb is expressed as follows:
 
(Movement amount Ta of the toner)&gt;(Movement amount Tb of the toner)
 
Therefore, a cycle, in which the collected toner is mixed into the toner in the second toner containing part  21   b  and is reused, is realized.
 
     As described above, the toner collected by the collection roller  11  moves from the agitation bar  15  to the agitation bar  16  side by the rotation of the agitation bar  15  and the agitation bar  16  as well as the function of the backflow prevention member  18 . The collected toner does not accumulate in the vicinity of the development roller  8 . Thereby, defects of the developer image such as fog and blur are prevented. Accordingly, the quality of the image of the developer image is improved. In addition, the collected toner is efficiently reused. 
     As explained above, in the first embodiment, the agitation bars that rotate and the backflow prevention member that restricts the backflow of the toner are provided. The toner collected by the collection roller moves from the first toner containing part that retains the collection toner to the second toner containing part side that retains unused toner. The collected toner does not accumulate in the vicinity of the development roller. Accordingly, an effect that the quality of the image of the developer image is improved is obtained. 
     In addition, an effect that the collected toner is efficiently reused is obtained. 
     Second Embodiment 
       FIG. 6  is a schematic side diagram of a configuration of a development device according to a second embodiment.  FIG. 7A  is an enlarged diagram of a main part of a configuration of the development device according to the second embodiment.  FIG. 7B  is a further enlarged diagram around carrying roller  41  Duplicative explanations on parts that are the same as the first embodiment discussed are omitted, and elements that are the same as or corresponding to the first embodiment are indicated with the same symbols. 
     In  FIGS. 6 ,  7 A and  7 B, a carrying roller  41  (roller member) as a first rotational member faces the collection roller  11  in the vicinity of the collection roller  11 , and is arranged between the collection blade  12  and the subsidiary supply roller  14 . The carrying roller  41  is configured by a conductive shaft (core) made of, for example, a steel use machinerbility (SUM) material and a silicone rubber foam layer or a urethane rubber foam elastic layer formed on the shaft in such a manner as to be in a roll shape. The carrying roller  41  rotates in a direction indicated by an arrow in  FIGS. 6 and 7  by a driving power transmitted through an idler gear (not illustrated) from the collection roller  11 . 
     In addition, a backflow prevention member  42  as a restriction part is arranged between the carrying roller  41  and the agitation bar  16  on the subsidiary supply roller  14  side of the carrying roller  41 . The backflow prevention member  42  inhibits the backflow of the toner in a direction from the agitation bar  16  side to the carrying roller  41 . 
     The backflow prevention member  42  is a blade shaped, resin molded article, and extends in a direction in parallel to a rotation shaft of carrying roller  41  and the rotation shafts of the agitation bar  16  and agitation bar  17 . One end as a fixed end of the backflow prevention member  42  is fixed on a holder of the first restriction blade  13  by a screw  45 . A front edge part  42   a  as a free end of the backflow prevention member  42  is formed in an R shape, and has a curvature radius R of 0.2 mm. A direction from the fixed end to the free end is a counter (opposite) direction from a rotational direction of the carrying roller  41 . The front edge part  42   a  is arranged to abut on an outer circumferential surface of the carrying roller  41 . The front edge part  42   a  is formed in the R shape to prevent attrition of the carrying roller  41 . 
     In addition, one part of the bottom surface  22   a  of the frame  22  of the development unit  61  is formed as a guide part  43  that curves along the outer circumferential surface of the carrying roller  41  so that a gap of approximately 1 mm is formed between the bottom surface  22   a  and the carrying roller  41  below the carrying roller  41 . The opening part  27  is formed between a top part  43   a  of the guide part  43  and the front edge part  42   a  as the free end of the backflow prevention member  42 . The opening part  27  causes the first toner containing part  21   a  to communicate with the second toner containing part  21   b , and the toner passes through the opening part  27 . 
     The agitation bar  16  as the second rotational member is arranged on the second toner containing part  21   b  side of the opening part  27 . Furthermore, the agitation bar  17  is arranged between the agitation bar  16  and the subsidiary supply roller  14 . 
     More specifically described, as shown in  FIG. 7B , a projection part  43   b  is formed between a first surface  22   a   1  and a second surface  22   a   2 . The projection part  43   b  is formed projecting toward the backflow prevention member  42 . The top part  43   a  is formed at the leading edge of the projection part  43   b . In a region between a center  41   a  of the carrying roller  41  and the top part  43   a  with respect to the toner carrying direction, the guide part  43  is formed along from the first surface  22   a   1  to the top part  43   a . In other words, the guide part  43  is formed along a rotational outer surface of the carrying roller  41 . 
     The rotation shafts of the carrying roller  41 , the agitation bar  16  and the agitation bar  17  are arranged in parallel to each other. The agitation bar  16  and the agitation bar  17 , respectively, rotate in directions indicated by arrows in  FIGS. 6 and 7  by a driving power from the subsidiary supply roller  14 . 
     In the present embodiment, the backflow prevention member  42  preferably contacts, or slightly presses the outer circumferential surface of the carrying roller  41  to scrape the toner off the carrying roller  41  and to prevent the backflow of the toner. 
     In addition, the rotational direction of the carrying roller  41  is not limited to the direction indicated by the arrow in  FIGS. 6 and 7 . However, the backflow prevention member  42  contacts the outer circumferential surface of the carrying roller  41  in a counter direction from the rotation of the backflow prevention member  42  from below, and the guide part  43  is arranged in one part of the frame  22  on the opposite side across the carrying roller  41  when the rotational direction of the carrying roller  41  is opposite from the direction. 
     A function of the configurations discussed above is explained with reference to  FIGS. 6 and 7 . Since an operation for image formation that the image forming apparatus  1  performs is the same as the first embodiment, duplicative explanations on the operation are omitted. 
     In a step of the image formation, in order to collect the development residual toner that has remained on the surface of the development roller  8  without moving to the photosensitive drum  51  during the development, the collection roller  11  is connected to ground through the resistance so that a collection voltage whose polarity is opposite to the charge polarity of the toner is applied to the collection roller  11 , and the development residual toner moves onto the collection roller  11 , and is scraped off the collection roller  11  by the collection blade  12 . 
     The development residual toner that has been scraped off and has fallen from the collection roller  11  into the first toner containing part  21   a  by the collection blade  12  is carried in the rotational direction indicated by the arrow of the carrying roller  41  in  FIGS. 6 and 7  by concave and convex parts on the surface of the carrying roller  41 . When the carried toner passes through the opening part  27  and reaches the position of the backflow prevention member  42 , the carried toner is scraped off the carrying roller  41  by the backflow prevention member  42  and moves to the second toner containing part  21   b  side since the backflow prevention member  42  contacts the carrying roller  41 . 
     The toner that has moved to the second toner containing part  21   b  is agitated by the agitation bar  16 . One part of the toner moves in a direction of the agitation bar  17 , is mixed into toner provided from the toner cartridge  19 , and is reused. 
     In addition, since the carrying roller  41  contacts the backflow prevention member  42 , and a gap between the carrying roller  41  and the guide part  43  is small, almost all the toner does not move in a direction from the agitation bar  16  to the carrying roller  41 . Accordingly, the toner in the first toner containing part  21   a  effectively moves to the second toner containing part  21   b.    
     As explained above, in the second embodiment, the carrying roller that rotate and the backflow prevention member that restricts the backflow of the toner are provided. The toner collected by the collection roller moves from the first toner containing part that retains the collection toner to the second toner containing part side that retains unused toner. The collected toner does not accumulate in the vicinity of the development roller. Accordingly, an effect that the quality of the image of the developer image is improved is obtained. 
     In addition, an effect that the collected toner is efficiently reused is obtained. 
     The first and second embodiments are explained with a printer as an image forming apparatus. However, the image forming apparatus is not limited thereto, but may be a photocopy apparatus, a facsimile device, and a multi function peripherals (MFP) that includes the photocopy apparatus and the facsimile device.