Abstract:
A transfer apparatus of the invention includes a primary transfer unit, and a secondary transfer unit that includes a transfer roller having a bearing and being capable of contacting with and separating from the primary transfer unit, the primary transfer unit includes a guide member receiving the bearing at a position opposite to the bearing, and the guide member has a protrusion on a surface with which the bearing contacts when the transfer roller contacts with and separates from the primary transfer unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from U.S. provisional application 61/026,677, filed on Feb. 6, 2008, the entire contents of each of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a transfer apparatus and an image forming apparatus including the same, and particularly to a transfer apparatus a part of which is constructed to be openable and closable relative to the main body of an image forming apparatus and the image forming apparatus including the same. 
     BACKGROUND 
     As an image forming apparatus of an electrophotographic system, such as a laser printer, a digital copying machine, or a laser facsimile, there is a type in which a toner image formed on a photoconductor is primarily transferred to a transfer belt, and the toner image primarily transferred on the transfer belt is further secondarily transferred to a recording sheet. In this type of image forming apparatus, a transfer apparatus includes a primary transfer unit having a transfer belt and a secondary transfer unit having a secondary transfer roller. 
     The primary transfer unit includes, for example, a drive roller, a secondary transfer opposite roller, and a primary transfer roller, and the transfer belt is stretched over the drive roller and the secondary transfer opposite roller and is rotated. The primary transfer roller is disposed at a position inside of the transfer belt and opposite to the photoconductor, and a specified potential is applied to the primary transfer roller so that the toner image on the photoconductor is primarily transferred to the outer periphery of the transfer belt. 
     The secondary transfer roller of the secondary transfer unit and the secondary transfer opposite roller of the primary transfer unit form a nip through the transfer belt. A recording sheet contained in a paper feeding section passes through a specified conveyance path and passes through the nip. When the recording sheet passes through the nip, a specified potential is applied to the secondary transfer roller, and the toner image primarily transferred on the outer periphery of the transfer belt is secondarily transferred to the recording sheet. 
     The secondarily transferred toner image is fixed by a fixing apparatus, and then is discharged to a discharge tray or the like included in the image forming apparatus. 
     When the recording sheet passes through the conveyance path or passes through the nip, paper jamming may occur due to some cause. 
     In order to enable a user to remove the jammed recording sheet, the secondary transfer unit is constructed to be openable and closable relative to the outside of the main body of the image forming apparatus. For example, the lower side of the secondary transfer unit is supported to be rotatable around a support shaft provided at the main body of the image forming apparatus, and a hook to be hooked on a fixing member provided at the main body of the image forming apparatus is provided on the upper side of the secondary transfer unit. In a standing state in which the secondary transfer unit is closed, the hook urged by a spring or the like is hooked on the fixing member, and the secondary transfer unit is fixed to the main body of the image forming apparatus. When the secondary transfer unit is opened, the user operates a handle lever or the like provided at the outside of the secondary transfer unit to release the hooking between the hook and the fixing member, and opens the secondary transfer unit to the outside of the apparatus while rotating it around the support shaft. 
     In addition to this, there is a type in which a magnet is provided on the upper side of the secondary transfer unit, and the secondary transfer unit is fixed to the main body of the image forming apparatus by the magnetic force of the magnet. 
     As stated above, in the transfer apparatus (or the image forming apparatus) of the related art, the dedicated opening and closing mechanisms (the foregoing hook, spring, handle lever, magnet, etc.) for opening and closing the secondary transfer unit are required, and these opening and closing mechanisms cause the increase of the number of parts of the whole apparatus and cause the increase of cost. 
     SUMMARY 
     The present invention is made in view of the above circumstances, and has an object to provide a transfer apparatus in which an opening and closing mechanism of a secondary transfer unit is greatly simplified, and a dedicated opening and closing mechanism part can be made substantially unnecessary, and an image forming apparatus including the same. 
     In order to achieve the object, according to an aspect of the invention, a transfer apparatus includes a primary transfer unit, and a secondary transfer unit that includes a transfer roller having a bearing and being capable of contacting with and separating from the primary transfer unit, the primary transfer unit includes a guide member receiving the bearing at a position opposite to the bearing, and the guide member has a protrusion on a surface with which the bearing contacts when the transfer roller contacts with and separates from the primary transfer unit. 
     Besides, according to another aspect of the invention, an image forming apparatus includes a photoconductor on which a toner image is formed, a primary transfer unit that includes a transfer belt and primarily transfers the toner image formed on the photoconductor to the transfer belt, and a secondary transfer unit that includes a transfer roller having a bearing and being capable of contacting with and separating from the primary transfer unit and secondarily transfers the toner image primarily transferred on the transfer belt to a recording sheet, the primary transfer unit includes a guide member receiving the bearing at a position opposite to the bearing, and the guide member has a protrusion on a surface with which the bearing contacts when the transfer roller contacts with and separates from the primary transfer unit. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view showing an example of an outer appearance of an image forming apparatus of an embodiment; 
         FIG. 2  is a sectional view showing an example of a detailed structure of the image forming apparatus of the embodiment; 
         FIG. 3  is a sectional view showing an example of a structure of a transfer apparatus of the embodiment; 
         FIG. 4  is a perspective view showing an example of an outer appearance of a related art secondary transfer unit; 
         FIG. 5  is a perspective view showing an example of an outer appearance of a related art primary transfer unit; 
         FIGS. 6A and 6B  are enlarged perspective views each showing a state in which a bearing of a secondary transfer roller is received in a guide member of the related art primary transfer unit; 
         FIGS. 7A and 7B  are enlarged perspective views each showing a state in which a bearing of a secondary transfer roller is received in a guide member of a primary transfer unit in a transfer apparatus of the embodiment; 
         FIG. 8  is a sectional view schematically showing a guide member and a protrusion of the embodiment; 
         FIGS. 9A to 9C  are explanatory views showing states in which the bearing of the secondary transfer roller is pushed into the guide member of the embodiment; and 
         FIGS. 10A to 10C  are explanatory views showing states in which the bearing of the secondary transfer roller is pulled out of the guide member of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A transfer apparatus and an image forming apparatus including the same according to an embodiment of the invention will be described with reference to the accompanying drawings. 
     (1) Image Forming Apparatus 
       FIG. 1  is a view showing an example of an outer appearance of a copying machine (or MFP) as a typical example of an image forming apparatus  1  of an embodiment. 
     The image forming apparatus  1  includes a reading section  2 , an image forming section  3 , a paper feeding section  4 , an operation section  5 , an ADF (Auto Document Feeder)  6  and the like. 
     The reading section  2  optically reads an original document placed on a document stand or an original document inputted to the ADF  6  and generates image data. 
     The image forming section  3  uses an electrophotographic system to print the image data on a sheet supplied from the paper feeding section  4 . 
     The operation section  5  includes a display panel as a user interface and various operation buttons. 
       FIG. 2  is a sectional view showing a more detailed structure of the image forming apparatus  1 . 
     The reading section  2  includes a document glass stand  21 , a first carriage  22 , a second carriage  23 , a CCD substrate  26  and the like. 
     The first carriage  22  and the second carriage  23  move in a right and left direction (main scanning direction) in  FIG. 2 . The first carriage  22  includes an exposure lamp  24 , and the exposure lamp  24  irradiates an original document placed on the document glass stand  21  while moving in the main scanning direction. The reflected light from the original document is guided to the CCD substrate  26  through a mirror  25   a  of the first carriage  22  and mirrors  25   b  and  25   c  of the second carriage  23 , and is converted into an electrical signal. The electrical signal is subjected to various image processings and image data is generated, and the image data is outputted to the image forming section  3 . 
     The image forming section  3  includes a laser unit  31 , a photoconductive drum  32 , a black development unit  33 , a revolver unit  34 , a primary transfer unit  7 , a secondary transfer unit  8 , a fixing unit  37 , a manual feed unit  36 , an automatic duplex unit  35  and the like. 
     The laser unit  31  outputs a laser light modulated according to the level of the image data, and forms an electrostatic latent image on the photoconductive drum  32 . The black development unit  33  develops the electrostatic latent image and forms a black toner image on the photoconductive drum  31 . 
     Thereafter, the black toner image on the photoconductive drum  31  is primarily transferred to a transfer belt  71  of the primary transfer unit  7 . 
     The transfer belt  71  is stretched over a drive roller  72  and a secondary transfer opposite roller  73 , and the secondary transfer opposite roller  73  and a secondary transfer roller  81  of the secondary transfer unit  8  form a nip. 
     The paper feeding section  4  includes an upper paper feeding section  41  and a lower paper feeding section  42 , and a sheet is picked up from either of the paper feeding sections and reaches the nip. 
     In the case of monochrome printing, the black toner image on the transfer belt  71  is secondarily transferred to the sheet at the nip. Thereafter, the toner image is fixed to the sheet by the fixing unit  37 , and is discharged to a discharge tray  38 . 
     On the other hand, in the case of color printing, toner images of respective colors developed by a cyan development unit  34   a , a magenta development unit  34   b , and a yellow development unit  34   c  included in the revolver unit  34  are superimposed and transferred onto the black toner image on the transfer belt  71 . When the transfer belt  71  is rotated four times, the toner images of the four colors of black, cyan, magenta and yellow are superimposed and transferred onto the transfer belt  71 , and a full-color toner image is formed. The full-color toner image is secondarily transferred to the sheet at the nip. Thereafter, the toner image is subjected to a fixing process and is discharged to the discharge tray  38 . 
     In the manual feed unit  36 , paper feeding is performed when manual feed printing is performed. Besides, the automatic duplex unit  35  realizes a paper feed path to automatically reverse the front and back of the sheet when duplex printing is performed. 
     The automatic duplex unit  35  is constructed to be openable and closable around a support shaft provided at the lower side of the unit in order to remove a jammed sheet and for maintenance. 
     (2) Transfer Apparatus 
       FIG. 3  is a sectional view showing an example of a structure of a transfer apparatus  9  included in the image forming apparatus  1 .  FIG. 3  also shows the photoconductive drum  32 . 
     The transfer apparatus  9  includes the primary transfer unit  7  and the secondary transfer unit  8 . 
     As described above, the primary transfer unit  7  is constructed such that the transfer belt  71  is stretched over the drive roller  72  and the secondary transfer opposite roller  73 . The drive roller  72  is rotated by a not-shown drive motor, and the transfer belt  71  is continuously rotated in an arrow direction in  FIG. 3 . 
     A primary transfer roller  74  is provided at a position inside of the transfer belt  71  and opposite to the photoconductive drum  32 . A specified voltage is applied to the primary transfer roller  74 , so that the toner image on the photoconductive drum  32  is primarily transferred to the outer periphery of the transfer belt  71 . 
     In addition to this, a tension roller  75 , a secondary transfer guide roller  76 , and an idle roller  77  are provided inside of the transfer belt  71 . The tension roller  75  is urged upward in  FIG. 3  by a not-shown spring or the like, and applies a specified tensile force to the transfer belt  71 . The secondary transfer guide roller  76  keeps a position where the transfer belt  71  contacts with the secondary transfer roller  81 . Similarly, the idle roller  77  keeps a position where the transfer belt  71  contacts with the photoconductive drum  32 . 
     A cleaning blade  78  is provided to be adjacent to the drive roller  72 , and removes toner remaining on the surface of the transfer belt  71 . The waste toner scraped by the cleaning blade  78  is discharged to a not-shown toner bag by an auger  79 . 
     The secondary transfer unit  8  includes the secondary transfer roller  81 , and the secondary transfer roller  81  and the secondary transfer opposite roller  73  form a nip. When a sheet passes through the nip, a specified potential is applied to the secondary transfer roller  81 , so that the toner image on the transfer belt  71  is secondarily transferred to the sheet. 
     The secondary transfer unit  8  is rotatable around a support shaft  82  provided at the lower side. When rotated in a direction of an arrow A of  FIG. 3  (the secondary transfer unit  8  is opened), the secondary transfer roller  81  is separated from the primary transfer unit  7 . With the secondary transfer unit  8  opened, the maintenance of the inside can be performed and a jammed sheet can be easily removed. 
     As shown in  FIG. 2 , the automatic duplex unit  35  is disposed at the outside of the secondary transfer unit  8 . Accordingly, when the secondary transfer unit  8  is opened, the automatic duplex unit  35  is first opened, and then, the secondary transfer unit  8  is opened. 
     On the other hand, when the secondary transfer unit  8  is rotated in a direction of an arrow B of  FIG. 3  (when the secondary transfer unit  8  is closed), the secondary transfer roller  81  and the primary transfer unit  7  contact with each other, and the secondary transfer roller  81  and the secondary transfer opposite roller  73  form a nip. 
     When the secondary transfer unit  8  is closed, it is necessary to perform alignment between the secondary transfer roller  81  and the secondary transfer opposite roller  73  with high accuracy. Thus, in a related art, guide members for guiding bearings at both ends of the secondary transfer roller  81  are provided in the vicinity of the secondary transfer opposite roller  73  of the primary transfer unit  7 . 
       FIG. 4  is a perspective view showing an example of an outer appearance of a related art secondary transfer unit  800 .  FIG. 5  is a perspective view showing an example of an outer appearance of a related art primary transfer unit  700 . 
     As shown in  FIG. 4 , the secondary transfer roller  81  is disposed almost at the center of the secondary transfer unit  800 , and a front side bearing and a rear side bearing are respectively provided at both ends of the secondary transfer unit  800 . 
     As shown in  FIG. 5 , at positions of the primary transfer unit  700  corresponding to the front side bearing and the rear side bearing, a front side guide member and a rear side guide member that align and receive these are respectively provided. 
       FIGS. 6A and 6B  are enlarged views showing states in which the front side bearing and the rear side bearing are respectively received in the front side guide member and the rear side guide member of the related art. 
     As shown in  FIG. 5 ,  FIG. 6A  and  FIG. 6B , the bottom of each of the front side guide member and the rear side guide member of the related art is formed to be flat. Thus, although alignment can be performed when the secondary transfer unit  800  is closed, the closed secondary transfer unit  800  can not be fixed or held in a standing state. 
     Then, as shown in  FIG. 4 , the secondary transfer unit  800  of the related art is provided with, as dedicated opening and closing mechanisms, a front side hook, a rear side hook, a hook shaft and the like. In the standing state in which the secondary transfer unit  800  is closed, the respective hooks urged by springs or the like are hooked by fixing members provided on the housing of the image forming apparatus and are fixed and held. When the secondary transfer unit  800  is opened, the user operates a handle lever or the like provided on the outside of the secondary transfer unit  800  to rotate the hook shaft, releases the hooking between each hook and the fixing member, and opens the secondary transfer unit  800  to the outside of the apparatus while rotating it around the support shaft  82 . 
     In addition to this, there is a type in which a magnet is provided on the upper side of the secondary transfer unit  800 , and the secondary transfer unit is fixed to the main body of the image forming apparatus by the magnetic force of the magnet. 
     As stated above, in the related art transfer apparatus (or the image forming apparatus), the dedicated opening and closing mechanisms (the foregoing hook, spring, handle lever, magnet, etc.) for opening and closing the secondary transfer unit are required, and these opening and closing mechanisms cause the increase of the number of parts of the whole apparatus and cause the increase of cost. 
     In contrast, in the transfer apparatus  9  of the embodiment of the invention, protrusions  91   a  and  91   b  are provided on bottoms of a front side guide member  90   a  and a rear side guide member  90   b  of the primary transfer unit  7 . That is, the protrusions  91   a  and  91   b , for example, trapezoidal protrusions  91   a  and  91   b  are provided on surfaces with which a rear side bearing  81   a  and a front side bearing  81   b  contact when the secondary transfer roller  81  contacts with and separates from the primary transfer unit. 
       FIGS. 7A and 7B  are enlarged views showing states in which the front side bearing  81   a  and the rear side bearing  81   b  are received in the front side guide member  90   a  and the rear side guide member  90   b  of the embodiment of the invention.  FIG. 8  is an enlarged view schematically showing the section of each of the guide members  90   a  and  90   b.    
     The outer periphery of the bearing  81   a ,  81   b  may be covered with a resin member or the like. Besides, the guide member  90   a ,  90   b  can also be formed of a resin member. 
     The protrusion  91   a ,  91   b  may be formed of a resin member integrally with the guide member  90   a ,  90   b.  The protrusion  91   a ,  91   b  may be formed of a resin member or the like as a separate body, and may be bonded to the bottom of the guide member  90   a ,  90   b.    
       FIGS. 9A to 9C  are views showing states arranged in time series, in which the secondary transfer unit  8  is being closed and the bearing  81   a ,  81   b  is being received in the guide member  90   a ,  90   b.    
     The protrusion  91   a ,  91   b  is provided in the vicinity of an inlet of the guide member  90   a ,  90   b , and as shown in  FIGS. 9A to 9C , the bearing  81   a ,  81   b  climbs over the protrusion  91   a ,  91   b  while rotating, and is received in the inside of the guide member  90   a ,  90   b.    
     A surface of the guide member opposite to the protrusion  91   a ,  91   b  is inclined to be widened outwardly so that the bearing  81   a ,  81   b  can easily pass through the inlet of the guide member even when the bearing  81   a ,  81   b  climbs over the top of the protrusion  91   a ,  91   b  ( FIG. 9B ). 
     The inner diameter of the guide member at the backward of the protrusion  91   a ,  91   b , which receives the bearing  81   a ,  81   b , is substantially equal to the outer diameter of the bearing  81   a ,  81   b , and accurate alignment is possible. 
     Since the once received bearing  81   a ,  81   b  is hindered from moving toward the outside by the protrusion  91   a ,  91   b  ( FIG. 9C ), the secondary transfer unit  8  is fixed in the standing state. Thus, the dedicated opening and closing mechanisms (hook, spring, handle lever, magnet, etc.) required in the transfer apparatus of the related art become unnecessary, and the cost of parts is reduced. Besides, the assembling step and adjusting step of the opening and closing mechanisms in the manufacturing process become substantially zero, and the cost of the whole apparatus can be reduced. 
     When a user opens the secondary transfer unit  8 , the user applies a suitable outward force and pills it out.  FIGS. 10A to 10C  are views showing states arranged in time series, in which the secondary transfer unit  8  is opened, and the bearing  81   a ,  81   b  is pulled out of the inside of the guide member  90   a ,  90   b  to the outside. The bearing  81   a ,  81   b  climbs over the protrusion  91   a ,  91   b  while rotating by the pulling force applied by the user. 
     As described above, according to the transfer apparatus  9  of the embodiment and the image forming apparatus  1 , the simple protrusion is provided on the guide member of the primary transfer unit, so that the opening and closing mechanism of the secondary transfer unit required in the related art is greatly simplified, and the dedicated opening and closing mechanism parts can be made substantially unnecessary, and as a result, the cost of the apparatus can be reduced. 
     The invention is not limited to the embodiments, but the components can be modified and embodied at the practical stage within the scope not departing from the gist. Besides, the invention of various embodiments can be formed by suitable combination of plural components disclosed in the embodiments. For example, some components may be deleted from all components disclosed in the embodiment. Further, components in different embodiments may be suitably combined.