Patent Publication Number: US-10775716-B2

Title: Image forming unit and image forming apparatus

Description:
CROSS-REFERENCE to RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2019-023104 filed Feb. 13, 2019. 
     BACKGROUND 
     (i) Technical Field 
     The present disclosure relates to an image forming unit and an image forming apparatus. 
     (ii) Related Art 
     Known is an image forming unit that includes a developing member that develops an electrostatic latent image on a rotating image carrier, a container member that accommodates a developing member and includes an end portion opposing the image carrier at a portion downstream of the developing member in a direction in which the image carrier moves, and a guide member that guides a recording medium to the image carrier and that opposes the end portion at a portion downstream of the container member in the direction in which the image carrier moves. The image forming unit has a flow path between the end portion of the container member and the guide member. The flow path guides a current of air caused by rotation of the image carrier in a direction away from the image carrier (Japanese Patent Application Publication No. 2015-079134). 
     SUMMARY 
     Aspects of non-limiting embodiments of the present disclosure relate to an image forming unit that keeps floating toner produced therein within itself to prevent the floating toner from intruding into an image forming apparatus. 
     Aspects of certain non-limiting embodiments of the present disclosure address the features discussed above and/or other features not described above. However, aspects of the non-limiting embodiments are not required to address the above features, and aspects of the non-limiting embodiments of the present disclosure may not address features described above. 
     According to an aspect of the present disclosure, there is provided an image forming unit that includes an image carrier that forms an electrostatic latent image, a developer carrier that is in contact with the image carrier while rotating about a rotation axis and facing the image carrier to develop the electrostatic latent image, a development housing that accommodates a developer and that rotatably supports the developer carrier at one end with an opening portion that is open to the image carrier, the development housing including an agitation path in which the developer is agitated and a feed path through which the developer is fed to the developer carrier, and a guide member disposed below the opening portion and including an inner surface opposing the development housing to form a flow path that guides a current of air produced with rotation of the developer carrier in a direction away from the developer carrier, and to guide a recording medium to the image carrier with an outer surface opposite to the inner surface. Dust contained in the current of air is deposited on the inner surface of the guide member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic cross-sectional view of an internal structure of an image forming apparatus according to an exemplary embodiment; 
         FIG. 2  is a perspective view of the entire structure of an image forming unit; 
         FIG. 3  is a perspective view of an undersurface of the image forming unit; 
         FIG. 4  is a schematic cross-sectional view of a structure of the image forming unit; 
         FIG. 5  is an enlarged schematic cross-sectional view of a flow path in a developing device; 
         FIG. 6  is a schematic plan view of a flow path in a developing device; 
         FIG. 7  is a perspective view of a flow path in the developing device without illustrating a photoconductor unit and the developing device; 
         FIG. 8  is a schematic cross-sectional view of a moment around a pivot shaft in the developing device; 
         FIG. 9  is a schematic cross-sectional view of a current of air around a photoconductor drum and a development roller of the image forming unit; 
         FIG. 10  is a perspective view of a current of air in a flow path without illustrating the developing device and the photoconductor unit; and 
         FIG. 11  illustrates an operation of removing the image forming unit of an image forming apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments and specific examples are described below with reference to the drawings to describe the disclosure in further detail. The disclosure, however, is not limited to these exemplary embodiments and specific examples. 
     In the following description with reference to the drawings, the drawings are schematic, and the ratios between the dimensions or other details differ from the actual ones. For easy understanding, components other than those needed for the description are omitted, as appropriate. 
     For easy understanding of the following description, in the drawings, the lateral direction of an image forming apparatus  1  is referred to as a X axis direction, the depth direction of the image forming apparatus  1  is referred to as a Y axis direction, and the vertical direction of the image forming apparatus  1  is referred to as a Z axis direction. 
     (1) Entire Structure and Operation of Image Forming Apparatus 
       FIG. 1  is a schematic, vertically sectional view of the internal structure of the image forming apparatus  1  according to an exemplary embodiment. 
     The entire structure and an operation of the image forming apparatus  1  will be described below, with reference to the drawings. 
     The image forming apparatus  1  includes a controlling device  10 , a sheet transport device  20 , an image forming unit  100  including an integrated unit of a photoconductor unit  30  and a developing device  40 , a toner cartridge  50 , an exposure device  60 , a transfer device  70 , and a fixing device  80 . 
     The controlling device  10  includes an image forming apparatus controller  11 , which controls the operation of the image forming apparatus  1 , a controller unit  12 , which prepares image data corresponding to a printing request, an exposure controller  13 , which controls lighting of a light source of the exposure device  60 , and a power supply device (not illustrated). The power supply device applies predetermined voltages to components such as a charging roller  32 , a development roller  42 , and a transfer roller  71 , which are described later, and feeds power to the exposure device  60 . 
     The controller unit  12  converts, to image information for forming latent images, image data input from an image reading device (not illustrated) or print information input from an external-information transmitting device (such as a personal computer), and outputs a driving signal to the exposure controller  13  at predetermined timing. The exposure controller  13  drives the exposure device  60  to scan the surface of a photoconductor drum  31  with light modulated in accordance with the formed image data. 
     The exposure device  60  according to the present exemplary embodiment includes an LED head including light emitting diodes (LEDs) arranged in a line. 
     The sheet transport device  20  is disposed at a bottom portion of the image forming apparatus  1 . The sheet transport device  20  includes a paper cassette  21 , and a large number of sheets P are stacked on the upper surface of the paper cassette  21 . The sheets P having the widthwise positions fixed by a regulation board are drawn out backward (in the X direction) one by one from the top by a sheet drawing portion  22 , and then transported to a contact portion of a pair of registration rollers  24  via relay rollers  23 . 
     The photoconductor unit  30  is disposed above the sheet transport device  20  and includes the photoconductor drum  31  that is driven to rotate. The charging roller  32 , the developing device  40 , the transfer roller  71 , and a cleaning blade  34  are disposed in the rotation direction of the photoconductor drum  31 . A cleaning roller  33 , which cleans the surface of the charging roller  32 , opposes the charging roller  32  in contact with the charging roller  32 . 
     The developing device  40  includes a development housing  41 , which accommodates a developer. The development housing  41  accommodates a development roller  42 , disposed to oppose the photoconductor drum  31 , and a pair of a feed auger  43 A and an agitation auger  43 B, disposed on the back side of and obliquely below the development roller  42 . The feed auger  43 A and the agitation auger  43 B feed the developer toward the development roller  42  while agitating the developer. Above the developing device  40 , a developer containing portion  44 , which accommodates a developer, is disposed. Before being attached to the image forming apparatus  1 , the developer containing portion  44  is divided by a seal member (not illustrated) from the development housing  41 , so that the developer is retained in the developer containing portion  44 . 
     Below the development housing  41 , an upper guide chute  45 , which is an example of a guide member, is disposed. The upper guide chute  45  guides a sheet P registered by the pair of registration rollers  24  to a transfer portion TR. The toner cartridge  50  is disposed above the developing device  40  while being supported by the image forming unit  100 . The toner cartridge  50  accommodates toner (not illustrated), and feeds the toner to the developing device  40  as needed. 
     The surface of the rotating photoconductor drum  31  is charged by the charging roller  32  and on which an electrostatic latent image is formed by the exposure device  60 . An electrostatic latent image formed on the photoconductor drum  31  is developed by the development roller  42  into a toner image. 
     The transfer device  70  includes the transfer roller  71  and a transport guide  72 . The transfer roller  71  receives a predetermined transfer voltage from the power supply device controlled by the image forming apparatus controller  11  to transfer the toner image on the photoconductor drum  31  to a sheet P that passes through a gap between the photoconductor drum  31  and the transfer roller  71 . 
     The remaining toner on the surface of the photoconductor drum  31  is removed by the cleaning blade  34 , and reclaimed into a waste toner box (not illustrated). Thereafter, the surface of the photoconductor drum  31  is recharged by the charging roller  32 . Remnants adhering to the charging roller  32  without being removed by the cleaning blade  34  are captured by the surface of the cleaning roller  33  rotating in contact with the charging roller  32 , and then discharged again onto the photoconductor drum  31  via the charging roller  32 . 
     The fixing device  80  includes a pair of a heating module  81  and a pressing module  82 . The area over which the heating module  81  and the pressing module  82  are in pressure contact with each other forms a fixing nip portion (fixing area). 
     The sheet P to which a toner image has been transferred by the transfer roller  71  is transported to the fixing device  80  via the transport guide  72  while having the toner image unfixed. 
     The sheet P transported to the fixing device  80  has the toner image fixed by the heating module  81  and the pressing module  82  with heat and pressure. The sheet P carrying the fixed toner image is discharged to a paper output tray  1   a  on the upper surface of the image forming apparatus  1  through a pair of discharging rollers  83 . 
     (2) Structure of Related Portion 
       FIG. 2  is a perspective view of the entire structure of the image forming unit  100 ,  FIG. 3  is a perspective view of an undersurface of the image forming unit  100 ,  FIG. 4  is a schematic cross-sectional view of a structure of the image forming unit  100 ,  FIG. 5  is an enlarged schematic cross-sectional view of a flow path  48  in the developing device  40 ,  FIG. 6  is a schematic plan view of the flow path  48  in the developing device  40 ,  FIG. 7  is a perspective view of the flow path  48  of the developing device  40  without illustrating the photoconductor unit  30  and the developing device  40 , and  FIG. 8  is a schematic cross-sectional view of a moment around a pivot shaft  101  in the developing device  40 . 
     Now, the structure of the developing device  40  and the air flow path  48  in the developing device  40  will be described with reference to the drawings. 
     (2.1) Entire Structure of Image Forming Unit 
     The image forming unit  100  includes the photoconductor unit  30 , the developing device  40 , and a waste toner reclaim container TB, which are formed as an integrated unit, and is attachable to and removable from the image forming apparatus  1  when an open-close cover  1   b  (refer to  FIG. 1 ) of the image forming apparatus  1  is open. 
     The photoconductor unit  30  and the developing device  40  are coupled together with the pivot shaft (refer to  FIG. 2  and  FIG. 8 )  101 , serving as a rotation shaft. When the development housing  41  of the developing device  40  is pressed by a pressing spring S (refer to  FIG. 4 ), the photoconductor unit  30  and the developing device  40  rotate about the pivot shaft  101 , and the development roller  42  and the photoconductor drum  31  come into contact with each other with a contact roller (not illustrated) interposed therebetween to have a predetermined gap held between each other. 
     The toner cartridge  50  is attached to an upper recess  102  of the image forming unit  100 , and feeds toner mixed with a developer by a toner feeding mechanism  105  into the development housing  41  of the developing device  40 . 
     The remaining toner on the photoconductor drum  31  removed by the cleaning blade  34  is transported into the waste toner reclaim container TB by a transport auger  35  and a transport coil auger (not illustrated) to be reclaimed. 
     (2.2) Structure of Photoconductor Unit 
     As illustrated in  FIG. 4 , the photoconductor drum  31  of the photoconductor unit  30  is rotatably supported by an image forming unit housing  104 . Besides the photoconductor drum  31 , the photoconductor unit  30  includes a unit of the charging roller  32 , the cleaning roller  33 , the cleaning blade  34 , and the transport auger  35 , which transports toner removed by the cleaning blade  34  into the waste toner reclaim container TB. 
     (2.3) Structure of Developing Device 
     As illustrated in  FIG. 4 , in the developing device  40 , the development roller  42  is rotatably supported by the development housing  41 . The development housing  41  defines a feed path  41   a , through which the developer is fed to the development roller  42  with rotation of the feed auger  43 A, and an agitation path  41   b , through which the developer is transported toward one end of the feed path  41   a  with rotation of the agitation auger  43 B while the developer is agitated. 
     A developer G to which toner fed from the toner cartridge  50  is mixed is transported from the near side (outer side or the Y side) to the far side (inner side or the −Y side) while being agitated by the agitation auger  43 B, and moved to the feed auger  43 A on the far side (inner side or the −Y side). The developer fed from the feed auger  43 A is then fed to the development roller  42 . 
     An ATC sensor SR is installed on the developing device  40 . The ATC sensor SR serves as a developer detection member that measures a ratio (TC value) of toner to a carrier in the developer circulating in the development housing  41 . The TC value of the developer is retained at a predetermined value by the image forming apparatus controller  11  of the image forming apparatus  1  instructing feeding of toner from the toner cartridge  50  on the basis of a measurement value from the ATC sensor SR. 
     The feed path  41   a  and the agitation path  41   b  in the development housing  41  are filled with the developer fed from the developer containing portion  44 , and covered with a covering member  41 A. 
     A layer regulation member  49  is disposed above a feed path  41   a  near the development roller  42  to regulate the thickness of a developer layer adhering to the development roller  42  with a magnetic force. 
     As illustrated in  FIG. 5  in detail, an opening  41   d  is formed below (on the −Z side of) an opening portion  41   c , in which the development roller  42  of the development housing  41  is rotatably supported, to extend in the widthwise direction (Y direction) of the development housing  41 . The opening  41   d  is open to the opposing surfaces of the development roller  42  and the photoconductor drum  31 . 
     The upper guide chute  45  is disposed below (on the −Z side of) the opening portion  41   c . The upper guide chute  45  has its inner surface  45   a  facing an outer surface  41   e  of the development housing  41 . A guide plate  45   d  is attached to an outer surface  45   b  of the upper guide chute  45  opposite to the inner surface  45   a . The guide plate  45   d  guides a sheet P transported after being registered by the pair of registration rollers  24  to a transfer portion TR, nipped by the photoconductor drum  31  and the transfer roller  71 . 
     An elastic body  46  made of a polyurethane sponge, which is a polyurethane foam, is attached to the outer surface  41   e  of the opening portion  41   c  of the development housing  41  opposing the inner surface  45   a  of the upper guide chute  45 . 
     As illustrated in  FIG. 6 , the elastic body  46  is attached to an area along the opening  41   d  extending in the widthwise direction (Y direction) of the development housing  41  and an area on both sides of the area in the sheet transport direction (X direction) to form an angular C shape. The elastic body  46  is compressed between the development housing  41  and the inner surface  45   a  of the upper guide chute  45 . As illustrated in  FIG. 6 , the elastic body  46  may be attached to the inner surface  45   a  of the upper guide chute  45 . 
     As illustrated in  FIG. 5 , the opening  41   d , the outer surface  41   e  of the development housing  41 , and the inner surface  45   a  of the upper guide chute  45  form part of the flow path  48 , which guides a current of air produced by rotation of the development roller  42  in a direction away from the development roller  42  (in the −X direction) at uniform airtightness. 
     A film member  47  made of a polyurethane film with a thickness of 0.2 to 0.3 mm is attached to the inner surface  45   a  of the upper guide chute  45  at a portion away from the development roller  42  (in the −X direction). As illustrated in  FIG. 5 , the film member  47  has its base end  47 a attached to the inner surface  45   a  of the upper guide chute  45 , and its free end  47   b  in contact with the outer surface  41   e  of the development housing  41 . As illustrated in  FIG. 6 , the film member  47  is attached over a certain amount of area (in the Y direction) on the downstream side (inner side) of the feed path  41   a  in the developer transport direction to extend in the widthwise direction of the developing device  40 . 
     Thus, a certain amount of area of the flow path  48  on the upstream side (inner side) of the feed path  41   a  in the developer transport direction extends in the axial direction (Y direction) of the development roller  42  to serve as a space sealed and defined by the elastic body  46  and the film member  47 , the entire area of the flow path  48  along the opening  41   d  on the downstream side (outer side) of the feed path  41   a  in the developer transport direction is sealed with the elastic body  46 , and the side (−X side) away from the development roller  42  is open to the outside. 
     As illustrated in  FIG. 7 , the outer surface  41   e  of the development housing  41  and the inner surface  45   a  of the upper guide chute  45  define a space below the opening portion  41   c  of the development housing  41 , the entire portion on the side closer to the development roller  42  is sealed with the elastic body  46 , and a partial portion on the side away from the development roller  42  is sealed with the free end  47   b  of the film member  47  in contact with the development housing  41 . Thus, the flow path  48  is formed over the inner surface  45   a  of the upper guide chute  45  of the developing device  40 . 
     As illustrated in  FIG. 8 , when the flow path  48  is viewed with reference to the pivot shaft  101  to which the photoconductor unit  30  and the developing device  40  are coupled together, the area closer to the pivot shaft  101  is sealed with the elastic body  46  compressed between the development housing  41  and the inner surface  45   a  of the upper guide chute  45 , and the area away from the pivot shaft  101  (on the −X side) is sealed with the film member  47  having its free end  47   b  in contact with the development housing  41 , the film member  47  having its base end  47   a  attached to the inner surface  45   a  of the upper guide chute  45 . 
     In the flow path  48  thus hermetically sealed, a distance L 2  between the pivot shaft  101  and the contact position of the free end  47   b  of the film member  47  is longer than a distance L 1  between the pressure contact position of the elastic body  46  and the pivot shaft  101 . However, a contact force F 2  of the film member  47  is far smaller than a pressure contact load F 1  of the elastic body  46 . Thus, a moment exerted on the photoconductor drum  31  when the development roller  42  comes into contact with the photoconductor drum  31  with rotation about the pivot shaft  101  negligibly increases, so that an increase of the load borne by the photoconductor drum  31  is reduced. 
     (3) Operation of Flow Path 
       FIG. 9  is a schematic cross-sectional view of a current of air around the photoconductor drum  31  and the development roller  42  of the image forming unit  100 .  FIG. 10  is a perspective view of a current of air in the flow path  48  without illustrating the developing device  40  and the photoconductor unit  30 .  FIG. 11  illustrates an operation of removing the image forming unit  100  in the image forming apparatus  1 . 
     When the image forming unit  100  develops an electrostatic latent image formed on the surface of the photoconductor drum  31 , a floating toner (referred to as cloud toner, below) may be produced in the developing device  40 . 
     Specifically, in the developing device  40 , toner may rise in the development housing  41  when, for example, toner is agitated by the feed auger  43 A or the agitation auger  43 B, or insufficiently charged toner is additionally fed to the development housing  41 , so that cloud toner may be produced in the development housing  41 . 
     Here, in the developing device  40 , a current of air that flows into the development housing  41  occurs as a result of, for example, rotation of the feed auger  43 A, the agitation auger  43 B, or the development roller  42 . Thus, the inside of the development housing  41  has a higher pressure than the outside of the development housing  41 . Thus, cloud toner may leak together with air from the inside of the development housing  41  of the developing device  40 , and may waft around the developing device  40 . Particularly, cloud toner frequently occurs on the upstream side of the feed path  41   a  of the development housing  41  in the developer transport direction, which is arranged on the side of the downstream side of the agitation path  41   b  in the developer transport direction. 
     When cloud toner leaks out around the developing device  40  and arrives at the transport path of the sheet P beyond the upper guide chute  45 , the toner may adhere to the sheet P to stain the sheet P. 
     When the image forming unit  100  is removed from the image forming apparatus  1  for replacement while toner is adhering to the outer surface  45   b  of the upper guide chute  45 , the adhering toner may fall into the image forming apparatus  1 , adhere to, for example, hands of a user that replaces the image forming unit  100 , or fall on, for example, clothes of a user to stain the clothes. 
     In the image forming unit  100  according to the present exemplary embodiment, the opening  41   d , which is open to the opposing surfaces of the development roller  42  and the photoconductor drum  31 , is formed below the opening portion  41   c  of the development housing  41  to extend in the widthwise direction (Y direction) of the development housing  41 . The flow path  48  is continuous with the opening  41   d  to extend toward the upstream side in the sheet transport direction and away from the development roller  42 . Thus, a current of air R 1  produced by rotation of the development roller  42  and the photoconductor drum  31  flows through the opening  41   d  into the flow path  48 . 
     As illustrated in  FIG. 9 , on the inner surface  45   a  of the upper guide chute  45  forming a lower wall of the flow path  48 , multiple ribs  45   c  extend in the axial direction of the development roller  42  to protrude in a direction crossing the direction in which the current of air R 1  flows. The ribs  45   c  have gradually higher heights from the one on the upstream side to the one on the downstream side in the direction in which the current of air R 1  flows. Thus, the surface area in the flow path  48  is increased to keep a larger amount of cloud toner in the flow path  48 . 
     As illustrated in  FIG. 10 , a certain amount of area of the flow path  48  on the upstream side of the feed path  41   a  in the developer transport direction on the downstream side of the flow path  48  in a direction in which the current of air R 1  flows extends in the axial direction of the development roller  42  to serve as a space sealed with and defined by the film member  47 , and the area on the downstream side of the feed path  41   a  in the developer transport direction is open to the outside. 
     Thus, a current of air (current of air R 2 ) flows in the space sealed with and defined by the film member  47  from the upstream side of the feed path  41   a  to the downstream side of the feed path  41   a  in the developer transport direction. This structure guides, in the axial direction of the development roller  42 , floating toner in the area on the upstream side of the feed path  41   a  in the developer transport direction in which the floating toner is particularly more likely to occur to keep cloud toner produced in the image forming unit  100  within the image forming unit  100 . 
     The ATC sensor SR is disposed on the upstream side of the feed path  41   a  in the developer transport direction. The current of air (current of air R 2 ) flows through the space sealed with and defined by the film member  47  from the upstream side of the feed path  41   a  to the downstream side of the feed path  41   a  in the developer transport direction. 
     Thus, the cloud toner is prevented from adhering to the ATC sensor SR. 
     In the image forming unit  100  according to the present exemplary embodiment, a handle  103  held for attachment or removal is disposed at a position away from the photoconductor drum  31  and most upstream in a direction in which the sheet P is guided. Thus, as illustrated in  FIG. 11 , when the image forming unit  100  is removed from the image forming apparatus  1  so as to hang down, cloud toner reclaimed into the flow path  48  is prevented from falling from the image forming unit  100  with the elastic body  46  attached to the flow path  48  in an angular C shape in the widthwise direction (Y direction) of the development housing  41  (refer to  FIG. 6  and  FIG. 7 ). 
     The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.