Patent Publication Number: US-9836009-B2

Title: Image forming apparatus and image forming unit having rotatable stay connecting side plates

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image forming apparatus such as an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer, an LED printer, etc.), and a facsimile apparatus, which forms an image to a recording medium using, for example, an electrophotographic image forming system. In addition, the invention relates to an image forming unit mounted in the image forming apparatus. 
     Description of the Related Art 
     In an image forming apparatus, there is left a minute but uncontrollable toner in the vicinity of a developing nip portion where the charged toner is delivered from a developing sleeve to a photosensitive drum. The majority of the toner is conveyed by an air flow and collected and trapped by a filter portion. However, part of the toner is scattered by a viscous flow generated in accordance with the rotation of a photosensitive drum, and attached and accumulated onto members around the developing nip portion without being conveyed to the filter portion. 
     In this way, when the toner is accumulated on the members around the developing nip portion and the amount of the accumulated toner is increased, the toner accumulates exceeding the angle of repose of the toner and falls down and may cause contamination of an intermediate transfer belt. Then, there is a concern about that the unintended toner is transferred onto a sheet due to the contamination, thereby causing an image defect. 
     Therefore, there is proposed a method of preventing the intermediate transfer belt from being contaminated when the uncontrollable toner is scattered in the vicinity of the developing nip portion. For example, Japanese Patent Laid-Open No. 2003-156934 discloses a configuration in which a toner receiving tray is provided below the developing nip portion and the toner scattering and falling from the developing nip portion is received into the toner receiving tray. 
     Herein, a stay for securing a strength of a photosensitive unit may be provided in the configuration in which the photosensitive unit (an image forming unit) which includes the photosensitive drum and a support member to support the photosensitive drum is mounted to a main body of the apparatus so as to form an image forming portion. Then, the stay may be disposed on a downstream side in a rotation direction of the photosensitive drum and above the toner receiving tray from the developing nip portion formed between the developing sleeve and the photosensitive drum when the photosensitive unit is mounted on the main body of the apparatus. 
     This is because the photosensitive drum and a cleaning unit are generally unitized in the photosensitive unit. Then, the cleaning unit also serves as the stay of the photosensitive unit, and thus the strength of the cleaning unit is easily secured. On the other hand, since a diagonal region from the cleaning unit with the photosensitive drum interposed therebetween is easily decreased in strength, the stay is provided in the region to secure the strength in many cases. Then, when the photosensitive unit provided with the stay at the position is mounted on the main body of the apparatus, the stay is easily disposed on the downstream side in the rotation direction of the photosensitive drum from the developing nip portion. 
     In this way, in a case where the stay is disposed on the downstream side in the rotation direction of the photosensitive drum from the developing nip portion, the toner scattered from the developing nip portion due to the viscous flow generated according to the rotation of the photosensitive drum may be accumulated on the stay without being received into the toner receiving tray (see  FIG. 9A ). When the photosensitive drum is rotated in such a state where the scattered toner is accumulated on the stay, the toner accumulated on the stay is likely to go along the viscous flow and slide down so as to fall down onto the intermediate transfer belt without falling down into the toner receiving tray provided below the stay as illustrated in  FIG. 9B . Then, in a case where the toner falls down onto the intermediate transfer belt, the unintended toner is transferred onto the sheet. Therefore, the image defect occurs. 
     Further, in a case where the toner is not accumulated on the stay, as illustrated in  FIG. 9C , the toner scattered from the developing nip portion is not blocked by the toner receiving tray. Therefore, the intermediate transfer belt is not contaminated. 
     SUMMARY OF THE INVENTION 
     It is desirable to provide an image forming unit or an image forming apparatus which can lessen an influence of the toner accumulated on a stay provided in an image forming unit onto an image. 
     According to a representative configuration of the present invention, an image forming apparatus includes: an image forming unit configured to be detachably attachable to the image forming apparatus and to include a rotatable image bearing member, a first support side plate which supports one end of the image bearing member in a rotational axis direction of the image bearing member, and a second support side plate which supports the other end of the image bearing member in the rotational axis direction; a development device configured to form a toner image on the image bearing member; a transfer device configured to transfer the toner image formed by the development device onto a transfer member; a rotatable stay configured to be disposed at a position on a downstream side from the development device and on an upstream side from the transfer device in a rotation direction of the image bearing member to face the image bearing member and to connect the first support side plate and the second support side plate; an operation portion configured to be provided at an end portion of the stay to rotate the stay; and a toner containing portion configured to contain the toner accumulated on the stay. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view schematically illustrating an image forming apparatus according to a first embodiment. 
         FIG. 2  is a perspective view illustrating a photosensitive unit according to the first embodiment. 
         FIG. 3  is a perspective view illustrating the photosensitive unit according to the first embodiment. 
         FIGS. 4A and 4B  are cross-sectional views schematically illustrating a configuration before and after the photosensitive unit according to the first embodiment is mounted. 
         FIGS. 5A and 5B  are diagrams for describing a stay operation according to the first embodiment. 
         FIGS. 6A and 6B  are diagrams for describing an operation of the stay and a stay cleaning member according to the first embodiment. 
         FIG. 7  is a perspective view of a photosensitive unit according to another configuration. 
         FIG. 8  is a cross-sectional view schematically illustrating a configuration in a state where the photosensitive unit according to another configuration is mounted. 
         FIGS. 9A to 9C  are diagrams for describing a problem in the related art. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     &lt;Image Forming Apparatus&gt; 
     Hereinafter, first the entire configuration of an image forming apparatus  1  according to a first embodiment of the invention will be described with reference to an operation at the time of image formation and the drawings. 
     As illustrated in  FIG. 1 , the image forming apparatus  1  includes an image forming portion which transfers a toner image onto a sheet P of a recording medium, a sheet feeding portion which feeds the sheet P to the image forming portion, and a fixing portion which fixes the toner image to the sheet P. 
     The image forming portion includes a photosensitive unit  15  ( 15 Y,  15 M,  15 C, and  15 K) as an image forming unit provided to be detachably attachable to the main body of the apparatus  1 . In addition, a charging portion  12  ( 12 Y,  12 M,  12 C, and  12 K), a development device ( 14 Y,  14 M,  14 C, and  14 K), a laser scanner unit  13  ( 13 Y,  13 M,  13 C, and  13 K), and an intermediate transfer unit are provided. 
     The photosensitive unit  15  includes a photosensitive drum  11  ( 11 Y,  11 M,  11 C, and  11 K) and a cleaning unit  20  ( 20 Y,  20 M,  20 C, and  20 K) as a cleaning device. 
     The intermediate transfer unit includes a primary transfer roller  35  ( 35 Y,  35 M,  35 C, and  35 K), an intermediate transfer belt  31 , a drive roller  33 , a tension roller  34 , a secondary transfer roller  32 , a secondary transfer counter roller  41 , and a cleaning device  36 . The intermediate transfer belt  31  is an endless cylinder-shaped belt, and suspended on the drive roller  33 , the tension roller  34 , and the secondary transfer roller  32 . 
     At the time of image formation, when a controller (not illustrated) issues a print signal, the sheet P stacked and stored in a sheet feeding cassette  61  is fed to a sheet conveying path by a feeding roller  62 . After being separated one by one by a separation unit (not illustrated), the fed sheet P is conveyed to a pair of registration rollers  76  by a conveying roller  75  through a conveying path  3 . 
     In the pair of registration rollers  76 , a skew feeding of the sheet P is corrected by causing the leading edge of the fed sheet to abut on a conveyance guide (not illustrated). Thereafter, the sheet P is sent to a pair of conveying rollers  77 , and the sheet P herein is conveyed to a secondary transfer portion at a timing of image formation (that is, a predetermined timing in synchronization with the rotation of the intermediate transfer belt  31  onto which the toner image is primarily transferred). 
     On the other hand, first the surface of the photosensitive drum  11  is charged by the charging portion  12  in the image forming portion. Then, the laser scanner unit  13  emits a laser light from a light source (not illustrated) provided therein, and irradiates the photosensitive drum  11  with the laser light. Therefore, an electrostatic latent image is formed on the surface of the photosensitive drum  11 . The toner image is formed on the photosensitive drum  11  by developing the electrostatic latent image by the development device  14 . 
     The toner image formed on the photosensitive drum  11  is primarily transferred onto the intermediate transfer belt  31  by applying a transfer bias to the primary transfer roller  35 . When the drive roller  33  receives a rotational force from a drive source such as a motor (not illustrated), the intermediate transfer belt  31  starts to be rotated. The primarily transferred toner image reaches the secondary transfer portion which is formed by the secondary transfer roller  32  and the secondary transfer counter roller  41  on the downstream side in a rotation direction by the rotation of the intermediate transfer belt  31 . Herein, the toner image is transferred onto the sheet P. 
     The sheet P with the toner image transferred thereon is sent to a fixing device  5  where the toner image is fixed onto the sheet P with heating and pressuring. Thereafter, the sheet P is conveyed by a discharge roller  90  and discharged to a discharge portion  66 . 
     Further, in a case where both surfaces of the sheet P are subjected to the image formation, first the sheet P passes through the fixing device  5  and then is conveyed to a reversing path  83 , and drawn back from the reversing path  83  to a switchback path  84 . Then, the leading end and the tailing end of the sheet are switched by changing a rotation direction of a pair of reverse rollers  79  forwardly or reversely, and the sheet is conveyed to a duplex conveying path  85 . Thereafter, the sheet P is conveyed by the conveying roller  75 , and conveyed to the secondary transfer portion again through the pair of registration rollers  76 . The subsequent image forming processes are similar to the above description. 
     &lt;Photosensitive Unit&gt; 
     Next, a configuration of the photosensitive unit  15  according to this embodiment will be described in detail. As illustrated in  FIG. 2 , the photosensitive unit  15  includes a front and rear side plate  19  as a support member. A casing  18  is screwed to the front and rear side plate  19 . The casing  18  includes a bearing, and a rotating shaft of the photosensitive drum  11  is fitted to the bearing such that the photosensitive drum  11  is rotatably supported thereto. 
     In addition, the cleaning unit  20  is supported to the front and rear side plate  19 . The cleaning unit includes a cleaning blade (not illustrated) and a fur brush (not illustrated), and collects the residual toner attached to the photosensitive drum  11 . Further, the collected residual toner is conveyed backward to the main body by a screw, and conveyed to a collect toner box which is exchangeable. 
     In addition, a stay  16  of a cylindrical shaft shape is supported to the casing  18  in order to prevent that the front and rear side plate  19  is opened and to secure a strength of the photosensitive unit  15  and the front and rear side plate  19 . The stay  16  is disposed diagonally to the cleaning unit  20  with the photosensitive drum  11  interposed in the center. In other words, the stay  16  is at a position on a side opposed to the cleaning unit  20  with respect to the center axis of the photosensitive drum  11 . Since the cleaning unit  20  serves as the stay, the stay  16  is provided at the above-described position in order to secure more strength of the photosensitive unit  15  and the front and rear side plate  19 . Further, the photosensitive unit  15  can be realized in a small space by providing the stay  16  near the photosensitive drum  11 . 
       FIG. 3  is a diagram illustrating the photosensitive unit  15  in the middle of being inserted into a side plate  23  of the main body of the image forming apparatus  1 . When the photosensitive unit  15  is mounted in the main body, as illustrated in  FIG. 3 , first the posture of the stay  16  is maintained by being inserted into the main body while being fitted to a fitting member  24  fixed to the side plate  23 . In this embodiment as described above, the stay  16  also serves as a guide unit which guides the position of the apparatus when the photosensitive unit  15  is mounted in the main body. 
     Next, after the insertion of the stay  16 , a fitting piece  21  of the casing  18  is fitted into a fitting hole  25  of the side plate  23 , so that the photosensitive unit  15  is positioned. 
       FIG. 4A  illustrates a peripheral configuration of the image forming portion before the photosensitive unit  15  is mounted, and  FIG. 4B  illustrates a peripheral configuration of the image forming portion after the photosensitive unit  15  is mounted. 
     As illustrated in  FIG. 4A , there are a developing sleeve  26  as a toner bearing member of the development device  14  and the primary transfer roller  35  as a transfer member in the vicinity of the portion where the photosensitive unit  15  is mounted. In addition, a toner receiving tray  17  (a toner receiving member) is provided near the intermediate transfer belt  31  below the developing sleeve  26 . The toner receiving tray  17  is used to catch the toner in order to prevent that the uncontrollable toner scattering from a developing nip portion N 1  formed between the photosensitive drum  11  and the developing sleeve  26  falls down onto the intermediate transfer belt  31 . Further, the toner receiving tray  17  is made of an elastically deformable member such as a polyethylene terephthalate sheet or a thin stainless steel plate, so that it is possible to prevent that the stay  16  used as a guide unit is hindered from being inserted or removed at the time when the photosensitive unit  15  is attached or detached. 
     As illustrated in  FIG. 4B , when the photosensitive unit  15  is mounted, first the development device  14  is pressed up to a predetermined position in a direction toward the photosensitive drum  11 , and a distance between the photosensitive drum  11  and the developing sleeve  26  is secured. Therefore, the developing nip portion N 1  is formed between the developing sleeve  26  and the photosensitive drum  11 , and the toner is delivered in the developing nip portion N 1  at the time of image formation. 
     In addition, the primary transfer roller  35  is pressed with respect to the photosensitive drum  11 , and a primary transfer nip portion N 2  is formed between the primary transfer roller  35  and the photosensitive drum  11 . In the primary transfer nip portion N 2 , the toner image formed in the surface of the photosensitive drum  11  at the time of image formation is transferred onto the intermediate transfer belt  31 . 
     Herein, when the photosensitive unit  15  is mounted in the main body of the image forming apparatus  1  according to this embodiment, the stay  16  is disposed on the downstream side in a rotation direction of the photosensitive drum  11  from the developing nip portion N 1  and on the upstream side in the rotation direction from the primary transfer nip portion N 2  as illustrated in  FIG. 4B . In addition, the toner receiving tray  17  is disposed below the stay  16 . For this reason, the toner scattering from the developing nip portion N 1  does not directly fall into the toner receiving tray  17  due to a viscous flow generated in accordance with the rotation of the photosensitive drum  11  but falling onto the stay  16 . Therefore, there is a concern that the toner accumulates on the stay  16 . 
     In this embodiment, the stay  16  is rotatably provided in order to prevent that the toner is accumulated on the stay  16 . Therefore, when the toner is accumulated on the stay  16  (see  FIG. 5A ), the stay  16  is rotated as illustrated in  FIG. 5B  so that the toner can be made to fall into the toner receiving tray  17  by the weight of the toner. Therefore, it is possible to prevent that the toner accumulated on the stay  16  is scattered by the viscous flow, and to prevent that the toner falls down to the intermediate transfer belt  31 . Accordingly, it is possible to prevent an image defect from occurring. 
     In addition, as described in this embodiment, since the stay  16  is a member of the cylindrical shaft shape, the stay  16  is easily rotated, and the toner is hardly accumulated on the stay  16 . In addition, the same effect can be achieved regardless of whether the stay  16  is rotated in the clockwise direction or in the counterclockwise direction. 
     Further, as a method of rotating the stay  16 , the stay  16  may be configured to be manually rotated by a serviceman or a user. Alternatively, a driving force may be transmitted from a drive source such as a motor to rotate the stay  16 . In a case where the stay is manually rotated, a holding portion or handling member  22  illustrated in  FIG. 2  can be provided at the end portion of the stay  16  as described in this embodiment. Therefore, since the serviceman or the user can hold the holding portion  22  to rotate the stay  16 , the stay  16  can be easily rotated. On the other hand, as a configuration of the rotation using a motor, there can be exemplified a drum unit configuration in which a gear  220 , which is a driving force transmission member to transmit the driving force from the drive source (motor) M illustrated in  FIG. 8  to the stay, is disposed at the end portion of the stay  16  as illustrated in  FIG. 7 . 
     In addition, as illustrated in  FIG. 6A , a stay cleaning member  27  for removing the toner accumulated on the stay  16  may be configured to be provided to abut on the stay  16 . With this configuration, the stay cleaning member  27  can sweep off the toner on the stay  16 , so that the cleaning performance can be improved. The toner swept off by the stay cleaning member  27  is held in the toner receiving tray  17  as illustrated in  FIG. 6B . 
     Further, the stay cleaning member  27  can be provided between the stay  16  and the toner receiving tray  17 . Therefore, the toner swept off by the stay cleaning member  27  is easily held in the toner receiving tray  17 . 
     In addition, a capillaceous member such as a fur brush, a fiber-implanted member, and a felt material can be used as a material of the stay cleaning member  27 . Alternatively, there may be used an elastic member such as a spongy material having roughness in its surface. Therefore, abrasion of the stay  16  can be reduced while improving the cleaning performance. 
     In addition, this embodiment has been described about an example of a color image forming apparatus of an intermediate transfer system, but the invention is not limited thereto. The invention may be applied to a monochrome image forming apparatus in which the toner image formed in the photosensitive drum is directly transferred on to the sheet. In other words, at the time when the photosensitive unit is mounted in the main body of the apparatus, the stay may be configured to be rotatably provided on the downstream side in the rotation direction of the photosensitive drum from the developing nip portion and on the upstream side from the transfer nip portion formed between the photosensitive drum and the transfer roller. With this configuration, it is possible to prevent that the toner is accumulated on the stay. It is possible to prevent that the toner on the stay falls down to the sheet causing an image defect. 
     In addition, the invention can be applied even to a process cartridge which is detachably attachable to the main body of the image forming apparatus. In other words, the apparatus may be configured to include the development device, the photosensitive unit which includes the photosensitive drum (the photosensitive unit which is detachably attachable to the main body of the process cartridge) and a support member for supporting the photosensitive drum, and the stay which secures the strength of the support member and is rotatably provided. With this configuration, it is possible to prevent that the toner is accumulated on the stay by rotating the stay when the process cartridge is mounted in the main body of the apparatus and the stay is disposed on the downstream side in the rotation direction of the photosensitive drum from the developing nip portion, and on the upstream side from the transfer nip portion, and above the toner receiving tray. Therefore, it is possible to prevent that the toner on the stay falls down to the intermediate transfer belt and the sheet causing an image defect. 
     According to the invention, since the stay is rotatably provided, the toner on the stay falls down to the toner receiving member according to the rotation of the stay. Therefore, since the toner is hardly accumulated on the stay, it is possible to prevent that the toner accumulated on the stay is scattered by the viscous flow and falls down to the intermediate transfer belt causing an image defect. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2015-118296, filed Jun. 11, 2015, which is hereby incorporated by reference herein in its entirety.