Patent Publication Number: US-10317839-B2

Title: Developing device and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to 35 U.S.C. § 119 to Japanese Patent Application No. 2017-106090, filed on May 30, 2017, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a developing device and an image forming apparatus. 
     Description of the Related Art 
     Developing devices are known which include a developer bearer the surface of which moves with a developer thereon, a development housing including the developer in its inner space and an opening from which the surface of the developer bearer is partially exposed in the direction of surface movement thereof to face a latent image bearer the surface of which moves with a latent image thereon, a drive assembly to drive members disposed in the development housing, and a collision assembly to move the collision member included in the collision assembly away from the development housing and thereafter toward the development housing to collide the collision member with the development housing. 
     A developing device has been proposed which includes a filter to prevent a developer from being discharged out of a development housing through a depressurizing opening disposed to restrict a rise of the air pressure in the development housing and a vibrator to vibrate the filter to move the filter into and out of contact with the development housing, thereby colliding with the development housing. 
     However, in the developing device, a drive assembly such as the vibrator specially disposed to move the filter in the direction of detachment and attachment, which increases the cost of the device. 
     This cost-increase occurs not only to the configuration using the filter as the member for collision with a development housing but also to any configuration of moving a collision member by the drive force of a specially-disposed drive assembly to the direction of detachment and attachment for the development housing. 
     SUMMARY 
     According to the present invention, provided is an improved developing device which includes a developer bearer the surface of which moves with a developer thereon, a development housing including the developer in an inner space thereof and an opening through which the surface of the developer bearer is partially exposed in a direction of surface movement thereof to face a latent image bearer a surface of which moves with a latent image thereon, a drive assembly disposed in the development housing, configured to drive members in the development housing driven by a driven force of the drive assembly, and a collision assembly including a collision member, the collision assembly being configured to move the collision member away from the development housing and toward the development housing to collide the collision member with the development housing, utilizing the drive force of the drive assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the detailed description when considered in connection with the accompanying drawings in which like reference characters designate like corresponding parts throughout and wherein: 
         FIG. 1  is a schematic diagram illustrating an example of the photocopier according to an embodiment of the present disclosure; 
         FIG. 2  is an enlarged diagram illustrating one of the four image forming units; 
         FIG. 3  is a diagram illustrating a cross section of the developing device according to an embodiment of the present disclosure; 
         FIG. 4  is a block diagram illustrating an example of the configuration of the control system to control proper and reverse rotation of a developing sleeve; 
         FIG. 5  is a flow chart illustrating control of a development drive motor; 
         FIG. 6  is diagram illustrating a perspective view of a beating device; 
         FIG. 7  is a diagram illustrating a perspective view of members constituting a beating member; 
         FIG. 8  is a diagram illustrating a perspective view of the beating device from which a second supporting member and a compression spring are removed; 
         FIG. 9  is a diagram illustrating a perspective view of the beating device illustrated in  FIG. 8  from which a one-way clutch is further removed; 
         FIG. 10  is a diagram illustrating a perspective view of a drive transmission unit to transmit the drive force of the development drive motor to the development sleeve, the beating device, etc.; 
         FIG. 11  is a diagram illustrating a perspective view from the direction of an arrow D of  FIG. 10 ; and 
         FIG. 12  is a diagram illustrating a beating position of the beating member. 
     
    
    
     The accompanying drawings are intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views. 
     DESCRIPTION OF THE EMBODIMENTS 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result. 
     As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     Moreover, image forming, recording, printing, modeling, etc. in the present disclosure represent the same meaning, unless otherwise specified. 
     A tandem color photocopier (herein after also referred to as photocopier  500 ) as an image forming apparatus, to which the developing device according to an embodiment of the present disclosure is applied, is described below. 
       FIG. 1  is a schematic diagram illustrating the photocopier  500  according to the embodiment of the present disclosure. 
     The photocopier  500  includes an original scanning unit  4  and an original conveying unit  3  over a printer unit  100  and a sheet feeding unit  7  under the printer unit  100 . The original conveying unit  3  conveys an original to the original scanning unit  4 , which scans the original to read image information of the original. The sheet feeding unit  7  accommodates a transfer sheet P as a recording medium and includes a sheet cassette  26  where the transfer sheet P is accommodated and a sheet feeding roller  27  that sends out the transfer sheet P in the sheet cassette  26  to the printer unit  100 . The dotted line in  FIG. 1  represents the convey route of the transfer sheet P in the photocopier  500 . 
     On the upper part of the printer unit  100  is disposed a sheet ejection tray  30  where the transfer sheets P on which output images are formed are stacked. The printer unit  100  includes four image forming units  6 Y,  6 M,  6 C, and  6 K to form toner images of each color (yellow, magenta, cyan, and black) and an intermediate transfer unit  10 . The image forming units  6 Y,  6 M,  6 C, and  6 K respectively include photoconductors  1 Y,  1 M,  1 C, and  1 K having a drum-like form as latent image bearers on which respective color toner images are formed and developing devices  5 Y,  5 M,  5 C, and  5 K that develop latent images formed on the surface of photoconductors. 
     The intermediate transfer unit  10  includes an intermediate transfer belt  8  and primary transfer bias rollers  9 Y,  9 M,  9 C, and  9 K. Each color toner image formed on the surface of each of the photoconductors  1 Y,  1 M,  1 C, and  1 K is transferred and superimposed on the intermediate transfer belt  8  to form a color toner image thereon. In addition, the primary transfer bias rollers  9 Y,  9 M,  9 C, and  9 K transfer the toner image formed on the surface of each of the photoconductors  1 Y,  1 M,  1 C, and  1 K to the intermediate transfer belt  8 . 
     The printer unit  100  includes a secondary transfer bias roller  19  that transfers the color toner image on the intermediate transfer belt  8  to the transfer sheet P. In addition, the printer unit  100  also includes a pair of registration rollers  28  that suspends conveying of the transfer sheet P fed by the sheet feeding roller  27  to control the timing of conveying the transfer sheet P to a secondary transfer nip formed by the intermediate transfer belt  8  and the secondary transfer bias roller  19  facing each other. Moreover, the printer unit  100  includes a fixing device  20  disposed above the secondary transfer nip to fix the unfixed toner image on the transfer sheet P. 
     In addition, below the sheet ejection tray  30  in the printer unit  100  and above the intermediate transfer unit  10  are disposed toner containers  11 Y,  11 M,  11 C, and  11 K of each color. The toner containers  11 Y,  11 M,  11 C, and  11 K of each color respectively accommodate toners of each color supplied to the developing devices  5 Y,  5 M,  5 C, and  5 K. 
       FIG. 2  is a diagram illustrating an enlarged view of one of the four image forming units  6 Y,  6 M,  6 C, and  6 K. 
     The four image forming units  6 Y,  6 M,  6 C, and  6 K are significantly the same in terms of the configuration and operation except for the color of toner for use in the image forming. Therefore, the symbols Y, M, C, and K representing their corresponding colors are timely omitted. 
     As illustrated in  FIG. 2 , the image forming unit  6  is a process cartridge integrally supporting photoconductor  1  and a developing device  5 . The process cartridge is detachably attachable to the photocopier  500 . For this reason, the developing device  5  can be easily replaced in the photocopier  500  including the developing device  5 , which enhances maintenance property of the photocopier  500 . 
     The image forming unit  6  includes a cleaner  2  for the photoconductor, a lubricant applicator  13 , and a charger  12  around the photoconductor  1  in addition to the developing device  5 . In the image forming unit  6  of the present embodiment, the cleaner  2  has a configuration of cleaning with a cleaning blade  2   a  and the charger  12  has a configuration of charging with a charging roller  12   a.    
     Below is a description about the operation during typical color image forming in the photocopier  500  of the present embodiment. 
     Firstly, if the start button is pressed in a state in which an original is placed on a plate therefor of the original conveying unit  3 , the original is conveyed from the plate by a conveying roller of the original conveying unit  3  to the contact glass of the original scanning unit  4 . The original scanning unit  4  optically scans the original placed on the contact glass to obtain the image information of the original. 
     More specifically, the original scanning unit  4  scans the image on the original on the contact glass with light emitted from an irradiation lamp. The light reflected at the original is focused at a color sensor via a group of mirrors and lenses. After each color separation light of red, green blue (RGB) of the color image information of the original is read at the color sensor, the color image information of the original is converted into electric image signals. Furthermore, based on the color separation image signals of RGB, the signals are subject to color conversion, color calibration, spatial frequency correction, etc., at the image processing unit to obtain the color image information of yellow, magenta, cyan, and black. 
     The image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit. The writing unit emits a laser beam L based on the image information of each color to the corresponding photoconductors  1 Y,  1 M,  1 C, and  1 K. 
     On the other hand, the four photoconductors  1 Y,  1 M,  1 C, and  1 K separately rotate clockwise in  FIGS. 1 and 2 . The surface of the photoconductors  1 Y,  1 M,  1 C, and  1 K is uniformly charged at the facing part of the charging roller  12   a  of the charger  12  (charging process). The four light sources of the writing unit emit each laser beam L corresponding to the image signal to the charged surface of photoconductors  1 Y,  1 M,  1 C, and  1 K of each color. The surface of each photoconductor  1 Y,  1 M,  1 C, and  1 K is irradiated with the laser beams L that have passed through separate optical paths in accordance with each color component of yellow, magenta, cyan, and black (irradiation process). 
     The surface of the photoconductor  1 Y for yellow disposed leftmost in  FIG. 1  is irradiated with the laser beam L corresponding to yellow component. The laser beam L of the yellow component scans the photoconductor  1 Y for yellow along the direction of rotation axis (main scanning direction) by a polygon mirror rotating at high speed. Due to this scanning of the laser beam L, a latent electrostatic image corresponding to the yellow component is formed on the surface of the photoconductor  1 Y charged by the charger  12 . 
     Similarly, the surface of the photoconductor  1 M for magenta disposed second leftmost in  FIG. 1  is irradiated with the laser beam L corresponding to the magenta component to form a latent electrostatic image corresponding to the magenta component thereon. The laser beam L for the cyan component is emitted to the surface of the photoconductor  1 C for cyan disposed third leftmost in  FIG. 1  to form a latent electrostatic image corresponding to the cyan component thereon. The laser beam L for the black component is emitted to the surface of the photoconductor  1 K for black disposed fourth leftmost in  FIG. 1  to form a latent electrostatic image corresponding to the black component thereon. 
     Thereafter, the surface of the photoconductor  1 Y,  1 M,  1 C, and  1 K on which the latent electrostatic image of each color is formed reaches the position facing the developing device  5 . Thereafter, each color toner is supplied from the developing devices  5 Y,  5 M,  5 C, and  5 K accommodating the developer composed of each color toner and magnetic carrier to the surface of the photoconductor  1 Y,  1 M,  1 C, and  1 K to develop the latent image on the photoconductors  1 Y,  1 M,  1 C, and  1 K (development process). 
     The surfaces of the photoconductor  1 Y,  1 M,  1 C, and  1 K after they have passed the facing part (development area) reach the facing part (primary transfer area) facing the intermediate transfer belt  8 . In the corresponding primary transfer areas, the primary transfer bias rollers  9 Y,  9 M,  9 C, and  9 K are disposed abutting the inner periphery of the intermediate transfer belt  8 . The primary transfer nip is formed by the photoconductors  1 Y,  1 M,  1 C, and  1 K and the primary transfer rollers  9 Y,  9 M,  9 C, and  9 K facing each other with the intermediate transfer belt  8  therebetween. The toner image of each color formed on the photoconductors  1 Y,  1 M,  1 C, and  1 K is transferred and superimposed onto the intermediate transfer belt  8  at this primary transfer nip (primary transfer process). 
     The individual surfaces of the photoconductors  1 Y,  1 M,  1 C, and  1 K that have passed the primary transfer nip reach the position facing the cleaner  2  for the photoconductor. At the position facing the cleaner  2  for the photoconductor, untransferred toner remaining on the photoconductor is scraped off by the cleaning blade  2   a  and retrieved (cleaning process for photoconductor). 
     The surfaces of the photoconductors  1 Y,  1 M,  1 C, and  1 K that have passed the part facing the cleaner  2  for the photoconductor passes a quenching unit facing a quenching device to quench the remaining charges so that a series of image forming process for the photoconductor is finished and the system is ready for the next image forming. 
     Each color toner image on the four photoconductors  1 Y,  1 M,  1 C, and  1 K is transferred and superimposed. The surface of the intermediate transfer belt  8  bearing the color toner image moves counterclockwise in  FIG. 1  and reaches the secondary transfer nip which is the position facing the secondary transfer bias roller  19 . On the other hand, the transfer sheet P fed from the sheet cassette  26  accommodating the transfer sheet P by the sheet feeding roller  27  passes the conveyor guide, is guided by the pair of the registration rollers  28 , hits the registration rollers  28 , and temporarily stops. The transfer sheet P that has hit the pair of registration roller  28  is conveyed to the secondary transfer nip in timing with forwarding the color toner image formed on the intermediate transfer belt  8 . The color toner image borne on the intermediate transfer belt  8  is transferred onto the transfer sheet P at the secondary transfer nip (secondary transfer process). 
     The surface of the intermediate transfer belt  8  that has passed the secondary transfer nip reaches the facing part with an intermediate transfer belt cleaner. At this facing part, the remaining toner adhering to the intermediate transfer belt  8  is retrieved by the intermediate transfer belt cleaner to finish the series of the transfer process at the intermediate transfer belt  8 . 
     The transfer sheet P onto which the color toner image is transferred at the secondary transfer nip is guided to the fixing device  20 . 
     In the fixing device  20 , the color image is fixed onto the transfer sheet P at the fixing nip formed by a fixing roller and a pressure roller by application of heat and pressure (fixing process). The transfer sheet P that has passed the fixing device  20  is ejected as the output image outside the printer unit  100  by a pair of ejection rollers  25  and stacks on the sheet ejection tray  30   
       FIG. 3  is a diagram illustrating a cross section of the developing device  5  according to the present embodiment. 
     The developing device  5  of the present embodiment includes a housing  58  as the development housing to accommodate the developer in the inner space of the developing device  5 . The housing  58  includes a development lower housing  58   a,  a development upper housing  58   b,  and a development cover  58   c.  The developing device  5  includes a development roller  50  as a developer bearer forming the development area facing the photoconductor  1 , a supply screw  53  as a supply conveying member, a retrieving screw  54  as a retrieving conveying member, a doctor blade  52  as a developer regulating member, and a separation member  57 . The supply screw  53  and the retrieving screw  54  include a spiral wing part disposed onto a rotation shaft and rotate to convey the developer along the axis direction of the rotation shaft. 
     The housing  58  includes an opening from which the surface of the development roller  50  is partially exposed in the development area where the development roller  50  faces the photoconductor  1 . The doctor blade  52  is disposed upstream of the development area where the photoconductor  1  faces the development roller  50  in the direction of the surface movement of the development roller  50  and below the development roller  50  facing the development roller  50  and regulates the amount of the developer borne on the development roller  50 . 
     The supply screw  53  and the retrieving screw  54  are conveying members to stir and convey the developer accommodated in the inner space of the housing  58  in the longitudinal direction (direction perpendicular to the page of  FIG. 3 ) while partially forming the circulation path. The supply screw  53  is disposed facing the development roller  50  and supplies the developer to the development roller  50  while rotating in the direction (counterclockwise) indicated by the arrow C in  FIG. 3  to convey the developer in the longitudinal direction. The retrieving screw  54  receives the developer on the development roller  50  that has passed through the development area and rotates in the direction (clockwise in  FIG. 3 ) indicated by the arrow B in  FIG. 3  to convey replenished toner and the developer while mixing and stirring them. 
     In the inner space in the housing  58 , a supply conveying path  53   a  to which the supply screw  53  is disposed and a retrieving conveying path  54   a  to which the retrieving screw  54  is disposed are spatially separated by the separation member  57 . In addition, the end part of the separation member  57  in the cross section (illustrated in  FIG. 3 ) vertically crossing the axis direction faces the surface of the development roller  50  and is disposed closely so that the separation member  57  also serves as a separation plate to promote detachment of the developer from the surface of the development roller  50 . Due to this feature of the separation member  57  as the separation plate, the developer that has been borne on the development roller  50  and passed through the development area is prevented from reaching the supply conveying path  53   a  and is moved toward inside of the retrieving conveying path  54   a  without delay. 
     The development roller  50  includes a magnet roller  55  including multiple magnets fixed inside and a development sleeve  51  rotating in the direction (counterclockwise in  FIG. 3 ) indicated by the arrow A around the magnet roller  55 . The development sleeve  51  encloses the magnet roller  55  and has a rotatable cylindrical form made of a non-magnetic material. On the surface of the development sleeve  51 , five magnetic poles of the first magnetic pole (south pole), the second magnetic pole (north pole), the third magnetic pole (south pole), the fourth magnetic pole (south pole), and the fifth magnetic pole (north pole) are formed as the multiple magnetic poles by the magnet roller  55 . 
     In this embodiment, around the end part disposed downstream of the development roller  50  exposed from the housing  58  in the direction of surface movement of the development roller  50  (hereinafter also referred to as development downstream area), the surface movement of the development roller  50  generates suction air stream toward the inner space of the housing  58 . Due to this suction air stream, scattering toner isolated from the carrier in the development downstream area can be suctioned and retrieved in the housing  58  together with air. This prevents toner scattering from the development area. In addition, in the present embodiment, to increase this suction air stream, the path space through which the suction air stream passes between a facing part  582  of the development cover  58   c  against the development roller  50  and the surface of the development roller  50  is narrowed. 
     Moreover, to avoid toner spraying out of the housing through a gap where the suction force into the housing  58  is weak when the inner pressure in the housing  58  rises due to this suction air stream, a depressurizing opening  581  is disposed on (formed by) the development cover  58   c  to eject the air in the housing  58  to the outside to restrict a rise of the air pressure in the housing  58 . Furthermore, the depressurizing opening  581  includes a filter  59  to restrict ejection of the toner from this depressurizing opening  581 . The air containing the toner in the inner space of the housing  58  passes through the filter  59 , at which the toner and the air are separated so that only the air is ejected outside the housing  58  through the depressurizing opening  581 . 
     Since the developing device  5  uses a two-component developer (including a case in which additives, etc., are added), the toner is suitably replenished into the inner space of the housing  58  through a toner replenishing opening  56  ( FIG. 10 ) disposed on the housing  58  in accordance with the tone consumption in the developing device  5 . The replenished toner is mixed and stirred together with the developer in the housing  58  while the retrieving screw  54  and the supply screw  53  convey them. 
     A development power source applies a development voltage to the development sleeve  51  of the development roller  50  and forms a development electric field in the development area by which the properly-charged (for example, negative polarity) toner is moved toward the latent electrostatic image part on the surface of the photoconductor  1 . Due to this development electric field, the toner in the developer on the surface of the development roller  50  is attached to the latent electrostatic image on the surface of the photoconductor  1 , thereby rendering the latent electrostatic image visible as a toner image. 
     The developer in the housing  58  is supplied to the surface of the outer perimeter of the development roller  50  due to the action of the magnetic field generated by the fifth magnetic pole P 5  of the magnet roller  55  while being conveyed in the longitudinal direction by the supply screw  53  disposed in parallel with and in the vicinity of the surface of the development roller  50 . The developer relayed to the surface of the development roller  50  is regulated by the doctor blade  52  and reaches the development area in accordance with the rotation counterclockwise of the development sleeve  51  as illustrated in the direction indicated by the arrow A in  FIG. 3 . 
     By the development electric field formed in the development area upon application of the development voltage to the development sleeve  51  by the development power source, the latent electrostatic image on the photoconductor  1  is developed with the toner. 
     The developer on the surface of the development roller  50  that has passed through the development area is returned to the inner space of the housing  58  in accordance with the rotation of the development sleeve  51  and detached from the surface of the development roller  50  as a result of the action of the repulsion magnetic field of the third magnetic pole P 3  and the fourth magnetic pole P 4  having the same polarity. The developer detached from the surface of the development roller  50  drops on the upper surface of the separation member  57  and slides down to the retrieving screw  54 . 
     The doctor blade  52  has a gap from the surface of the development sleeve  51  facing the doctor blade  52  to adjust the developer borne on the development sleeve  51  to have a predetermined thickness. However, depending on foreign objects entered into the housing, the environment condition in which the developing device is installed, toner aggregation appearing in the housing  58  is stopped by the doctor blade  52 , which may clog the gap. If the gap is clogged by such foreign objects and toner aggregation, the developer cannot pass through the portion where the gap is clogged so that the latent image corresponding to the portion is not developed, resulting in occurrence of images with white streaks. 
     Therefore, the development sleeve  51  is reversely rotated after development in the present embodiment. 
       FIG. 4  is a block diagram illustrating an example of the configuration of the control system to control proper and reverse rotation of the development sleeve  51 . A control unit  300  as the control device is disposed corresponding to each of the four developing devices  5 . However, the basic configuration thereof is the same. Therefore, the color separation symbols Y, M, C, and K are omitted in the description. As illustrated in  FIG. 4 , the control unit  300  includes a central processing unit (CPU  301 ), a read only memory (ROM  302 ), a random access memory (RAM  303 ), etc. In the present embodiment, the control unit  300  of each of the developing devices  5  is partially used in common in the multiple developing devices  5 , for example, the CPU  301 , the ROM  302 , and the RAM  303 . 
     In  FIG. 4 , the control unit  300  includes the the CPU  301 , the ROM  302 , and the RAM  303 . 
     The control unit  300  controls drive of the development drive motor  550  as the drive source of the rotation of the development sleeve  51  and rotationally drives the development sleeve  51  counterclockwise in  FIG. 3  as the normal rotation of the development sleeve  51  constituting the development roller  50  during the drive. Conversely, for the reverse control, the development sleeve is rotated clockwise in  FIG. 3 . 
       FIG. 5  is a control flow chart illustrating the control of the development drive motor  550 . 
     Upon receipt of the print signal (Yes to S 1 ), the control unit  300  properly rotates the development drive motor  550  (S 2 ). In accordance with the proper rotation of the development drive motor  550 , the development sleeve  51  properly rotates (counterclockwise in  FIG. 3 ) to convey the developer on the surface of the development sleeve  51  to the development area, thereby developing the latent image on the photoconductor  1 . 
     When the image forming is complete (Yes to S 3 ), the control unit  300  rotates the development drive motor  550  (S 4 ) in the reverse direction against the direction during the image forming to reversely rotate the development sleeve  51  (clockwise in  FIG. 3 ). Due to this reverse rotation of the development sleeve  51 , foreign objects and toner aggregation clogging the gap between the doctor blade  52  and the development sleeve  51  are removed and drop onto the supply conveyor path  53   a.    
     After the development sleeve  51  is reversely rotated at an angle (Yes to S 5 ), the development drive motor  550  halts (S 6 ). In the present embodiment, the development sleeve  51  is reversely rotated about 20 to about 30 degrees. Due to this reverse rotation of the development sleeve  51  about 20 to 30 degrees, foreign objects and toner aggregation clogging the gap between the doctor blade  52  and the development sleeve  51  are caused to drop onto the supply conveyor path  53   a.    
     The filter  59  disposed at the depressurizing opening  581  clogs as a result of usage over time, so that the amount of air in the housing  58  ejected through the depressurizing  581  decreases. As a consequence, the amount of air entering into the housing  58  due to the suction air flow surpasses the amount of air ejected through the depressurizing opening  581 , so that the inner pressure in the housing  58  increases, which may cause spraying out of the toner. 
     In addition, due to the usage over time, the toner adheres to the inner wall of the housing  58  and grows to form agglomeration of the toner. The agglomeration may be peeled off from the inner wall of the housing  58  in time and clog the gap between the development sleeve  51  and the doctor blade  52 , which may cause production of defective images, as described above. 
     In addition, the scattering toner isolated from carrier and retrieved at the development downstream area together with the suction air flow tends to adhere to the facing part  582  of the development cover  58   c,  facing the development roller  50 . Therefore, the scattering toner easily accumulates at this facing part  582 . In due course, the toner accumulating at the facing part  582  grows to form a block, which may be peeled off from the facing part  582 , spill outside the housing  58 , and contaminate the image forming apparatus. 
     To deal with this issue, in the present embodiment, a beating device  40  is disposed to beat the housing  58 . The beating device  40  beats the housing  58  to provide an impact shock to it. This impact shock vibrates the filter  59  held by the housing  58  and shakes off the toner clogged in the filter  59 , thereby restricting clogging in the filter  59  over time. In addition, due to the impact shock to the housing  58  provided by beating the housing  58  by the beating device  40 , the toner adhering to the inner wall of the housing  58  drops, thereby preventing agglomeration of the toner and accumulation of the toner at the facing part  582 . 
       FIG. 6  is a diagram illustrating a perspective view of the beating device  40 .  FIG. 7  is a diagram illustrating a perspective view of the members constituting the beating device  40 . In addition,  FIG. 8  is a diagram illustrating a perspective view of the beating device  40  from which a second support member  48  and a compression spring  43  are removed.  FIG. 9  is a diagram illustrating a perspective view of the beating device  40  illustrated in  FIG. 8  from which a one-way clutch  44  is further removed. 
     The beating device  40  includes a beating member  41  as a collision member to collide with the housing  58  and the compression spring  43  as a biasing member to bias the beating member  41  to the housing  58 . 
     In addition, the beating device  40  includes a beating gear  42  to which the drive force of the development drive motor  500  is transmitted, the one-way clutch  44  to transmit the drive force during the reverse rotation, and a cam  45  to move the beating member  41  away from the housing  58  against the biasing force of the compression spring  43 . 
     The beating gear  42  is fixed onto the one-way clutch  44 . The one-way clutch  44  is attached to a cam shaft  49  onto which the cam  45  is fixed and shuts off the transmission of the drive force to the cam shaft  49  during the development (proper rotation of the development sleeve  51 ). Also, the one-way clutch  44  is linked to the cam shaft  49  during the reverse rotation to transmit the drive force to rotate the cam  45 . 
     The beating member  41  is made of metal. This metal constitution of the beating member  41  is rigid in comparison with the beating member  41  made of plastic. This high rigidity of the beating member  41  makes it possible to prevent elastic deformation of the beating member  41 , which leads to absorption of the impact shock of the beating member  41  against the housing  58 , so that the impact shock to the housing  58  becomes great. 
     A cam follower  46  is put around the beating member  41 . The cam follower  46  includes a putting-around part  46   a  having a ring-like form put around the beating member  41  and an arm  46   b  extending along the normal line from the putting-around part  46   a  with the front end abutting the cam  45 . 
     As illustrated in  FIG. 6 , the beating member  41  pierces a first support member  47 . The compression spring  43  is disposed compressed between the putting around part  46   a  of the cam follower  46  and the second support member  48 . In addition, the putting-around part  46   a  of the cam follower  46  abuts the first support member  47  and serves to prevent the beating member  41  from dropping out of the first support member  47  due to the biasing force of the compression spring  43 . 
     As illustrated in  FIGS. 8 and 9 , a pair of whirl stops  47   a  to stop the cam follower  46  from revolving is disposed onto the first support member  47 . The arm  46   b  of the cam follower  46  extends between the pair of whirl stops  47   a  to the position where the front end abuts against a slant surface  45   a  of the cam  45 . 
     The cam  45  is fixed onto the cam shaft  49  and includes multiple slant parts  45   c  around the circumference direction. The slant part  45   c  includes the slant surface  45   a  slanting against the plane orthogonal to the cam shaft  49 . Specifically, the slant surface  45   a  gradually slants away from the first support member  47  as the slant surface  45   a  goes upstream of the cam  45  in the rotation drive direction (direction indicated by the arrow D in  FIG. 7 ) by the development drive motor  550 . The slant surface  45   a  abuts the front end of the arm  46   b  and raises the arm  46   b  by the rotation of the cam  45  against the biasing force of the compression spring  43  to move the beating member  41  away from the housing  58 . This slant surface  45   a  includes two stoppers  45   b   1  and  45   b   2  spaced a predetermined distance therebetween to hold the front end of the arm  46   b.  In the present embodiment, the slant surface  45   a  has steps to form the stoppers  45   b   1  and  45   b   2 . 
       FIG. 10  is a diagram illustrating a perspective view of a drive transmission unit  70  to transmit the drive force of the development drive motor  550  to the development sleeve  51 , the beating device  40 , etc. 
     The drive transmission unit  70  includes an input gear  71  engaged with a drive output gear  170  disposed on the side of the printer unit  100  to which the drive force of the development drive motor  550 . The input gear  71  is fixed on one end of the shaft of the supply screw  53  and the drive force is transmitted from the drive output gear  170  to the input gear  71  to rotate the supply screw  53 . 
     In addition, a step gear  72  rotating with the input gear  71  is disposed on the shaft of the supply screw  53  and an idler gear  73  is engaged with the step gear  72 . The idler gear  73  is engaged with a bifurcating input gear  74 . A bifurcating output gear  75  integrally rotating with the bifurcating input gear  74  is engaged with a development gear  76  fixed onto the development sleeve  51  and the beating gear  42  of the beating device  40 . Due to this, the drive force of the development drive motor  550  as the drive device to drive the development sleeve  51  is transmitted to the beating device  40  to drive the beating device  40 . Therefore, in comparison with a configuration including a drive device to drive the beating device  40  separating from the drive device to drive the development sleeve  51 , the device can be inexpensively manufactured. 
     At the end on the reverse side positioned opposite to the side on which the input gear  71  of the shaft of the supply screw  53  is disposed, a retrieving output gear is disposed onto the retrieving screw  54  to transmit the drive force of the development drive motor  550 . The drive force is transmitted from the retrieving output gear to the retrieving screw  54  via one or more gears to rotate the retrieving screw  54 . 
       FIG. 11  is a diagram illustrating a perspective view from the direction indicated by the arrow D in  FIG. 10 .  FIG. 12  is a diagram illustrating the beating position of the beating member  41 . 
     The beating member  41  is disposed in such a manner that the beating member  41  collides at a position close to the part (indicated by the dotted line T in  FIG. 12 ) where the filter  59  of the development cover  58   c  is held. Due to this, the shock impact at the time of the collision of the beating member  41  is transmitted to the filter  59  with less attenuation to appropriately drop the toner from the filter  59 . In addition, beating the development cover  58   c  also directly conveys the impact shock to the facing part  582  disposed on the development cover  58   c  as well. Due to this, the toner adhering to the facing part  582  can be beaten off to restrict accumulation of the toner at the facing part  582 . Therefore, it is possible to prevent the device from being contaminated by the toner block appearing as a result of accumulation at the facing part  582  and falling off outside the housing  58 . 
     In addition, the impact shock is transmitted from the development cover  58   c  to the development upper housing  58   b  and the development lower housing  58   a,  thereby beating off the toner adhering to the inner wall of the development lower housing  58   a  and the development upper housing  58   b.  Due to this, it is possible to restrict occurrence of toner aggregation in the housing  58 . 
     In addition, as illustrated in  FIG. 11 , a shock absorber  81  is disposed on the part where the beating member  41  of the development cover  58   c  collides. The shock absorber  81  relieves the impact noise occurring at the time of collision of the beating member  41 . 
     In the present embodiment, at the reverse rotation after image forming, the drive force of the development drive motor  550  is transmitted to the cam  45  to drive the beating device  40 . Due to this, the beating member  41  can provide a shock impact to the housing  58  during non-image forming so that this shock impact has no adverse impact on produced images. 
     It is also possible to shut off the drive force to the cam  45  during image forming by using an electromagnetic clutch and connect the electromagnetic clutch during non-image forming to transmit the drive force to the cam  45 . However, in general, electromagnetic clutches are more expensive and larger than one-way clutches. Moreover, electromagnetic clutches consume much power. Therefore, the present embodiment takes a configuration of using the one-way clutch  44  to transmit the drive force of the development drive motor  550  to the cam  45  during the reverse rotation, thereby avoiding increasing the size and cost of a device. 
     In the present embodiment, as described above, the reverse rotation is complete when the development sleeve  51  is reversely rotated about 20 to 30 degrees. Therefore, the arm  46   b  of the cam follower  46  cannot climb over the slant surface  45   a  of the cam  45  in the reverse rotation once. The arm  46   b  presses the slant surface  45   a  by the biasing force of the compression spring  43 . If the arm  46   b  stops in the middle of the slant surface  45   a,  the cam  45  receives a force to rotate in the direction reverse to the proper rotation direction (indicated by the arrow D in  FIG. 7 ). 
     If the development drive motor  550  properly rotates during the image forming, the force to stop the force to reversely rotate the cam  45  is lost. Therefore, without the stoppers  45   b   1  and  45   b   2  to the slant surface  45   a,  the cam  45  reversely rotates due to the biasing force of the compression spring  43  to follow the beating gear  42  and the front end of the arm  46   b  climbs down the slant surface  45   a.  As a result, the front end of the arm  46   b  of the cam follower  46  never climb over an apex  451   a  ( FIG. 7 ) of the slant surface  45   a  so that the beating member  41  never beats the housing  58 . 
     To solve this issue, it is possible to increase the amount of the reverse rotation. However, it causes the following problem if the amount is excessive. That is, due to the reverse rotation of the development sleeve  51 , the developer on the separation member  57  detached from the surface of the development sleeve  51  partially adheres to the development sleeve  51  again and is conveyed to the development area. The developer that adheres to the development sleeve  51  again is conveyed to the development area with no regulation by the doctor blade  52 . Therefore, the thickness of the developer is thicker than that of the developer after passing the doctor blade  52 . When this developer that has adhered to the development sleeve  51  again is conveyed to the development area having a narrow gap between the photoconductor  1  and the development sleeve  51 , the developer is partially regulated by the photoconductor  1 . As a result, the developer regulated by the photoconductor  1  falls off and contaminates the image forming apparatus. Therefore, to prevent this problem, as illustrated in  FIG. 3 , the rotation angle of the development sleeve  51  during the reverse rotation is required to be not greater than an angle θ, which is from the end on the downstream of the facing part  582  in the direction of the surface moving of the development sleeve  51  during the proper rotation of the development sleeve  51  to the end of the development area on the downstream of the surface moving. As a result, the reverse rotation cannot continue to a degree that the arm  46   b  climbs over the apex  451   a  of the slant surface  45   a  during the reverse rotation. 
     In addition, to beat off the toner on the filter  59  or adhering to the inner surface of the housing  58 , an impact of about 1,000 G is required. Therefore, the beating member  41  is moved away from the housing  58  in some degree to sufficiently accelerate the beating member before the collision with the housing  58 . Therefore, the length of the slant surface  45   a  along the rotation direction is shortened for the arm  46   b  to climb over the apex  451   a  of the slant surface  45   a  with a less reverse rotation. However, the beating member  41  cannot be moved away from the housing  58  to a degree that the shock impact is about 1,000 G. 
     In addition, the slant angle of the slant surface  45   a  can be enlarged to move the beating member  41  away from the housing  58  to a degree that the shock impact is about 1,000 G even if the length of the slant surface  45   a  is short along the rotation direction. However, the torque of the cam  45  increases as the slant angle of the slant surface  45   a  increases. Therefore, generally, to rotate the cam  45 , an expensive and high power motor is required for the development drive motor  550 , which may increase the size and cost of the machine. In addition, the load to the gears constituting the drive transmission unit  70  increases, which accelerates abrasion of the gears, thereby shortening the working life of the gears. 
     Therefore, in the present embodiment, as described above, the stoppers  45   b   1  and  45   b   2  are disposed on the slant surface  45   a.    
     If the reverse rotation starts from the state illustrated in  FIG. 7  after image forming and the cam  45  rotates in the direction indicated by the arrow D illustrated in  FIG. 7 , the arm  46   b  of the cam follower  46  climbs up the slant surface  45   a.  Due to this, the beating member  41  moves in the direction away from the housing  58  against the biasing force of the compressions spring  43 . Thereafter, when the arm  46   b  climbs over the first stopper  45   b   1  disposed downstream in the rotation direction of the cam  45 , the reverse rotation is finished. At this point, the biasing force of the compression spring  43  is applied to the slant surface  45   a  of the cam  45  via the arm  46   b  so that a force is applied to the cam  45  in the direction reverse to the direction indicated by the arrow D illustrated in  FIG. 7 . As a result, the first stopper  45   b   1  positioned downstream of the arm  46   b  in the direction indicated by the arrow D illustrated in  FIG. 7  abuts the arm  46   b.  Since the first stopper  45   b   1  abuts the arm  46   b,  a force to rotate the cam follower  46  with the beating member  41  as the point of support occurs to the arm  46   b.  However, the arm  46   b  abuts the whirl stop  47   a  illustrated in  FIG. 9  to prevent the rotation of the cam follower  46 . Due to this, the reverse rotation of the cam  45  against the direction indicated by the arrow D illustrated in  FIG. 7  is prevented. Therefore, the arm  46   b  stays between the first stopper  45   b   1  and the second stopper  45   b   2  without climbing down the slant surface  45   a.    
     In the following reverse rotation, if the cam  45  rotates in the direction indicated by the arrow D illustrated in  FIG. 7  again, the arm  46   b  of the cam follower  46  further climbs up the slant surface  45   a  and moves into the direction in which the beating member  41  further moves away from the housing  58  against the biasing force of the compression spring  43 . When the arm  46   b  climbs over the second stopper  45   b   2 , the reverse rotation is finished. At this point, again the biasing force of the compression spring  43  is applied to the slant surface  45   a  of the cam  45  via the arm  46   b  so that a force is applied to the cam  45  in the direction reverse to the direction indicated by the arrow D illustrated in  FIG. 7 . However, since the second stopper  45   b   2  abuts the arm  46   b   2 , the rotation reverse to the direction indicated by the arrow D illustrated in  FIG. 7  is stopped. 
     In the further following reverse rotation, if the cam  45  rotates in the direction indicated by the arrow D illustrated in  FIG. 7  again, the arm  46   b  of the cam follower  46  further climbs up the slant surface  45   a  and climbs over the apex  451   a  of the slant surface  45   a.  As a result, the arm  46   b  does not abut the slant surface  45   a  any more, and the beating member  41  furiously moves toward the housing  58  by the biasing force of the compression spring  43  and collides the housing  58 . 
     In the present embodiment, as described above, since the stopper  45   b   1  and the  45   b   2  are disposed on the slant surface  45   a,  the arm  46   b  finally climbs up the apex  451   a  of the slant surface  45   a  in multiple reverse rotation operations even when the drive amount during the reverse rotation is small. Therefore, it is possible to move the beating member  41  away from the housing  58  in such a manner that a shock impact of about 1,000 G to the housing  58  can be applied. In addition, the arm  46   b  can climb up the apex  451   a  of the slant surface  45   a  in multiple reverse rotations, so that the slant angle of the slant surface  45   a  can be reduced in comparison with the case in which the arm  46   b  climbs up the apex  451   a  of the slant surface  45   a  on a single reverse rotation. Therefore, it is possible to reduce an increase of the torque to rotate the cam  45  in comparison with the case in which the arm  46   b  climbs up the apex  451   a  of the slant surface  45   a  on a single reverse rotation. Therefore, in comparison with the case in which the arm  46   b  climbs up the apex  451   a  of the slant surface  45   a  on a single reverse rotation, it is possible to use a motor with lower power as the development drive motor  550 , thereby reducing the size and the cost of a device. 
     The stopper can be disposed in such a manner that the arm  46   b  can climb over the stopper in accordance with the rotation angle of the cam  45  during reverse rotation. The number of stoppers and the positions thereof can be determined to suit to the configuration of the device. 
     The above-described is just an example and other aspects of the present disclosure are, for example, as follows. 
     Aspect 1 
     1. The developing device  5  includes a developer bearer such as the development roller  50 , the surface of which moves with a developer thereon, a development housing such as the housing  58  including the developer in an inner space thereof and an opening through which the surface of the developer bearer is partially exposed in a direction of surface movement thereof to face a latent image bearer such as the photoconductor  1  the surface of which moves with a latent image thereon, a drive assembly such as the development drive motor  550  disposed in the development housing, configured to drive members in the development housing driven by a driven force of the drive assembly, and a collision assembly such as the beating device  40  including a collision member such as the beating member  41 , the collision assembly being configured to move the collision member away from the development housing and toward the development housing to collide the collision member with the development housing, utilizing the drive force of the drive assembly. 
     According to this, the drive assembly such as the development drive motor  550  to drive members disposed in the development housing such as the developer bearer such as the development roller  50  and conveying members (supply screw  53 , the retrieving screw  54 , etc.) to convey the developer in the development housing such as the housing  58  moves the collision member such as the beating member  41  to the direction in which the collision member is moved away from and toward the development housing. Therefore, the developing device is inexpensive in comparison with the configuration requiring another drive assembly to move the collision member to the direction in which the collision member is moved away from and toward the development housing, 
     Aspect 2 
     In Aspect 1, the developing device further includes a control device such as the control unit  300  configured to reversely move the surface of the developer bearer such as the development sleeve  51  in a determined amount of the surface movement after development of the latent image on the latent image bearer such as the photoconductor  1 , and wherein the collision assembly such as the beating device  40  further includes a one-way clutch configured to transmit the drive force of the drive assembly such as the development drive motor  550  to the collision member while the control device reversely moves the surface of the developer bearer. 
     According to this, as described in the embodiment, it is possible to reduce the size and the cost of a device in comparison with a configuration of conveying the drive force during the reverse rotation using an electromagnetic clutch. 
     Aspect 3 
     In Aspect 2, the collision device such as the beating device  40  further includes a bias member such as the compression spring  43  to bias the collision member such as the beating member  41  toward the development housing such as the housing  58  and the cam  45  including a slant surface to move the collision member away from the development housing while abutting a coupling member such as the cam follower  46  coupled to the collision member in accordance with the rotation of the cam  45  disposed rotatable around an axis in parallel with the direction of the collision member moving away and toward the development housing, and the stoppers  45   b   1  and  45   b   2  are disposed on the slant surface  45   a  of the cam  45  to stop the coupling member from climbing down the slant surface  45   a.    
     According to this, as described in the embodiment, even when the moving amount of the reverse rotation is small, the coupling member such as the cam follower  46  can climb up the slant surface  45   a  in the reverse rotation multiple times, so that the collision member such as the beating member  41  can be moved away from the development housing to a degree that the toner adhering to the inner wall of the development housing can be suitably beaten off. In addition, the slant angle of the slant surface  45   a  can be gentle, thereby reducing the torque to rotate the cam  45 . 
     Aspect 4 
     In Aspect 3, at the rotation angle of the cam  45  in the reverse rotation, the stoppers  45   b   1  and  45   b   2  are disposed in such a manner that the coupling member such as the cam follower  46  can climb over the stoppers  45   b   1  and  45   b   2  based on the rotation angle of the cam  45  during the reverse rotation. 
     Therefore, the coupling member such as the cam follower  46  climbs over the stopper per reverse rotation, thereby climbing up the slant surface. 
     Aspect 5 
     In any one of Aspects 1 to 4, the development housing such as the housing  58  includes the depressurizing opening  581  to discharge air in the development housing therethrough to restrict a rise of an air pressure in the development housing, and a filtering member such as the filter  59  is disposed on the depressurizing opening  581  to prevent the developer from being discharged out of the development housing through the depressurizing opening  581 . 
     According to this, it is possible to prevent the inner pressure in the housing from rising and restrict spraying out of the developer through the gap between the developing roller and the development housing. 
     In addition, the shock impact due to the collision of the collision member such as the beating member  41  into the development housing is transmitted to the filtering member such as the filter  59 , thereby beating off the developer clogging in the filtering member. 
     According to this, it is possible to restrict clogging in the filtering member over time. This makes it possible to suitably discharge the air in the development housing through the depressurizing opening  581  over time, thereby restricting a rise of the inner pressure in the development housing. 
     Aspect 6 
     In Aspect 5, the development housing such as the housing  58  includes multiple members, and the depressurizing opening is disposed on one of the multiple members, wherein one of the multiple members such as the development cover  58   c  further includes the facing part  582  disposed downstream of development area in the direction of the surface movement of the developer bearer during development, facing along the surface of the developer bearer with a distance therebetween. 
     This makes it possible to suitably beat off the developer accumulating on the facing part  582  and the developer clogging in the filtering member. 
     Aspect 7 
     In any one of Aspects 1 to 5, the development housing such as the housing  58  further includes the facing part  582  disposed downstream of development area in a direction of the surface movement of the developer bearer during development, facing along the surface of the developer bearer with a distance therebetween. 
     As described in the embodiment, this makes it possible to beat off the developer adhering to the facing part  582  due to the shock impact of the collision of the collision member such as the beating member  41  into the development housing. According to this, it is possible to prevent the developer from accumulating on the facing part  582 . 
     Aspect 8 
     In any one of Aspects 1 to 7, the shock absorbing member such as the shock absorber  81  is disposed at the position of the development housing such as the housing  58  where the collision member such as the bearing member  41  collides the development housing. 
     As described in the embodiment, this makes it possible to reduce the impact noise occurring at the time of the collision of the collision member such as the beating member  41  into the development housing such as the housing  58 . 
     Aspect 9 
     An image forming apparatus includes the development  5  of any one of Aspects 1 to 8 to develop a latent image formed on the latent image bearer such as the photoconductor  1  to obtain a toner image, which is finally transferred onto a recording medium such as a transfer sheet. 
     According to the present disclosure, the developing device can be inexpensively prepared. 
     This makes it possible to reduce the cost of an apparatus. 
     Having now fully described embodiments of the present invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit and scope of embodiments of the invention as set forth herein.