Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2012-193649 filed on Sep. 4, 2012. 
     BACKGROUND 
     Technical Field 
     The present invention relates to an image forming apparatus and a transport device. 
     SUMMARY 
     According to an aspect of the invention, there is provided an image forming apparatus including an image forming apparatus member, a toner image forming unit including a housing that accommodates at least one of a toner image retainer to retain a toner image and a toner retainer to supply a toner to the toner image retainer, and a recording medium transport unit including a transport belt, having an endless shape, that is openably and closably mounted to the image forming apparatus member and transports a recording medium, with being wound between a pair of support rollers provided along a transport direction of the recording medium, and a regulation member that faces the transport belt to regulate a posture of the recording medium, wherein when the recording medium transport unit is closed with respect to the image forming apparatus member, the regulation member is positioned to come into contact with the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic cross-sectional view illustrating an inside configuration of an image forming apparatus; 
         FIG. 2  is a schematic cross-sectional view partially illustrating principal parts of a paper feed device, a paper transport device, and one image forming unit which constitute a paper transport path of the image forming apparatus; 
         FIG. 3A  is a perspective view illustrating a paper posture regulating member when viewed from the surface side thereof,  FIG. 3B  is a perspective view illustrating a member holder portion and a film member which constitute the paper posture regulating member when viewed from the back surface sides of the member holder portion and the film member, and  FIG. 3C  is a longitudinal cross-sectional view, about cross-section A-A shown in  FIG. 3B , schematically illustrating the paper posture regulating member; 
         FIG. 4  is a schematic cross-sectional view illustrating a state in which an opening and closing cover is opened with respect to an image forming apparatus member; 
         FIG. 5A  is a diagram illustrating a bordered print, and  FIG. 5B  is a diagram illustrating a borderless print; and 
         FIG. 6  is a schematic cross-sectional view partially illustrating principal parts of a paper feed device, a paper transport device, and one image forming unit which constitute a paper transport path of an image forming apparatus according to a comparative example. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments and specific examples of the invention will be described in more detail below with reference to the drawings, but the invention is not limited thereto. 
     It should be noted that the drawings are schematic only and the ratios of each dimension or the like are different from those actually used, in the explanation using the following drawings. Components other than those required to facilitate understanding of the description are omitted as appropriate. 
     In order to facilitate understanding of the following description, the forward and rearward direction refers to an X-axis direction, the left and right direction refers to a Y-axis direction, and the vertical direction refers to a Z-axis direction. 
     (1) Overall Configuration and Operation of Image Forming Apparatus 
       FIG. 1  is a schematic cross-sectional view illustrating an inside configuration of an image forming apparatus  1  according to an exemplary embodiment. 
     Hereinafter, the overall configuration and the operation of the image forming apparatus  1  will be described with reference to the drawings. 
     The image forming apparatus  1  includes a control device  10 , a paper feed device  20 , image forming units  30 , a paper transport device  40 , an exposure device  50 , and a fixing device  60 . An upper surface (Z direction) of the image forming apparatus  1  is formed with a discharge tray  1   a  to discharge and accommodate paper on which an image is recorded. 
     The control device  10  has a controller  11  to control the operation of the image forming apparatus  1 , an image processing portion  12  of which the operation is controlled by the controller  11 , a power supply  13 , etc. The power supply  13  applies a bias voltage to charging rollers  32 , development rollers  36 , transfer rollers  44 , etc. which are described later. 
     The image processing portion  12  converts printed information input from an external information transmitting device (for example, a personal computer or the like) into image information for latent image formation to output a driving signal to the exposure device  50  at a preset timing. 
     The paper feed device  20  is provided on the bottom of the image forming apparatus  1 . The paper feed device  20  includes a paper loading plate  21 , and paper P as multiple recording media is loaded onto an upper surface of the paper loading plate  21 . The paper P, which is loaded onto the paper loading plate  21  and has a position in the width direction decided by a regulation plate (not shown), is drawn one by one from above in the forward direction (−X direction) by a paper drawing portion  22 , and is then transported up to a nip portion of a pair of resist rollers  23 . 
     Each of the image forming units  30  includes a photoconductor unit  30 A and a development unit  30 B which are integral with each other as an exchange unit and detachably mounted to the image forming apparatus  1 . 
     The photoconductor unit  30 A includes a photoconductor drum  31 , a charging roller  32 , a cleaning roller  33  to clean a surface of the charging roller  32 , a cleaning blade  34 , and a drum housing  35 . 
     The development unit  30 B has a development housing  39  within which developer is accommodated. The development housing  39  is provided therein with a development roller  36  disposed to face the photoconductor drum  31 , and an auger  37  which is arranged obliquely downward to the back surface side of the development roller  36  and agitates and transports the developer to the development roller  36  side. The development roller  36  is closely provided with a layer regulating member  38  to regulate a layer thickness of the developer. 
     In the image forming unit  30 , the photoconductor unit  30 A and the development unit  30 B as the exchange unit may be provided and detachably mounted to the image forming apparatus  1  respectively. 
     A surface of the rotating photoconductor drum  31  is electrically charged by the charging roller  32  and formed with electrostatic latent images by latent image forming light emitted from the exposure device  50 . The electrostatic latent images formed on the rotating photoconductor drum  31  are respectively developed as yellow (Y), magenta (M), cyan (C), and black (K) toner images by the development roller  36 . 
     The residual toner on the surface of the photoconductor drum  31  is removed by the cleaning blade  34  and collected in a waste toner accommodating portion provided in the drum housing  35 . The surface of the photoconductor drum  31  is electrically charged again by the charging roller  32 . 
     Meanwhile, the residue, which adheres to the charging roller  32  without being removed by the cleaning blade  34 , comes into contact with the charging roller  32  to be captured and accumulated on a surface of the rotating cleaning roller  33 . 
     The paper transport device  40  is used as a transfer unit and includes a transport belt  41  which circulates along a paper transport path, a pair of tension rollers  42  and  43  which span the transport belt  41  in an annular shape (endless shape), transfer rollers  44 , and a paper posture regulating member  45 . 
     In the paper transport device  40 , the above-mentioned respective members are integral with each other as the transfer unit and detachably mounted to the image forming apparatus  1 . 
     The transport belt  41  is made of a belt material (rubber or resin) which may electrostatically adsorb paper, and is laid across the pair of tension rollers  42  and  43  in an annular shape (endless shape). 
     In the pair of tension rollers  42  and  43 , the tension roller  42  of the lower side (−Z direction) is used as a driving roller to drive the transport belt  41 , whereas the tension roller  43  of the upper side (Z direction) is used as a driven roller. 
     Each of the transfer rollers  44  is arranged on the back surface side of the transport belt  41  which corresponds to the photoconductor drum  31  of each image forming unit  30 . 
     A predetermined transfer bias is properly applied between each photoconductor drum  31  and the associated transfer roller  44  by the power supply  13 . Consequently, the paper P is closely attached between the photoconductor drum  31  and the transport belt  41  and each toner image on the photoconductor drum  31  is transferred onto the paper P. 
     The fixing device  60  is constituted by a heating roller  61  and a pressure roller  62 , and is formed with a nip portion (fixing region) by a pressured region between the heating roller  61  and the pressure roller  62 . In addition, the fixing device  60  is provided downstream of the transport belt  41  in a paper transport direction thereof, and is used as a downstream side transport unit to transport the paper P supplied from the transport belt  41 . The speed to transport the paper in the fixing device  60  is set to slower than the speed at which the transport belt  41  transports the paper. 
     The paper P onto which the toner image is transferred in the paper transport device  40  is transported to the fixing device  60  via a transport guide in a state in which the toner image is not fixed. The paper P transported to the fixing device  60  passes through the nip portion (fixing region) formed by the pair of heating roller  61  and pressure roller  62 , with the consequence that the toner image is fixed on the paper P by action such as pressing and heating. The paper P on which the fixed toner image is formed is guided by the transport guide and discharged from a pair of discharge rollers  63  to the discharge tray  1   a  of the upper surface of the image forming apparatus  1 . 
     (2) Configuration and Operation of Paper Transport Device 
     Hereinafter, the configuration and the paper transport operation of the paper transport device  40  according to the exemplary embodiment will be described with reference to the drawings. However, it will be first described with respect to problems of an image forming apparatus  100  according to a comparative example with reference to the drawings. 
     In the following description, the common components in the paper transport device are respectively denoted by the same reference numerals and a detailed description thereof is omitted. 
     Image Forming Apparatus of Comparative Example 
       FIG. 6  is a schematic cross-sectional view partially illustrating principal parts of a paper feed device  20 , a paper transport device  40 , and one image forming unit  30  which constitute a paper transport path of an image forming apparatus  100  according to a comparative example. 
     A pair of resist rollers  23  is provided at the downstream side of a paper drawing portion  22 . The pair of resist rollers  23  gives a transport force to paper P drawn in the forward direction (−X direction) by the paper drawing portion  22 , and is used as a supply unit to supply the paper P to a transport belt  41 . The pair of resist rollers  23  has a driving side resist roller  23   a  and a driven side resist roller  23   b.    
     The driving side resist roller  23   a  and the driven side resist roller  23   b  come into contact with each other to form a nip portion, and thus a leading edge portion of the paper P, which is drawn from the paper drawing portion  22  and to which the transport force is given, is temporarily stopped by the nip portion. In a temporarily stopped state, the paper P is formed with a predetermined loop and the leading edge portion is pressured, and thereby the skew of a sheet is corrected. 
     The driving side resist roller  23   a  is connected with a driving source (not shown) through an electromagnetic clutch (not shown) which is used as a release unit to release the transport force to the paper P from the pair of resist rollers  23 . 
     After the paper P is temporarily stopped, the electromagnetic clutch turns ON at a predetermined timing and a rotational driving is transferred from the driving source. Thereby, the driving side resist roller  23   a  supplies the paper P, which is supplied from the paper drawing portion  22 , to a nip portion between the transport belt  41  and the image forming unit  30 (Y) of the furthest upstream side at a predetermined timing. Meanwhile, the driven side resist roller  23   b  rotates depending on driving of the driving side resist roller  23   a.    
     The paper P sent out from the pair of resist rollers  23  is rushed from the furthest upstream end (tension roller  42  side) of the transport belt  41  to the paper feed device  40  and transported to the nip portion between the transport belt  41  and the image forming unit  30 Y of the furthest upstream side. 
     In this case, for thick paper, when the leading edge portion of the paper P is lifted from a surface of the transport belt  41  due to resilience of the paper P and a lifted amount is large, there is a problem in that the leading edge portion of the paper P comes into contact with each toner image before transfer which is retained on a photoconductor drum  31  and toner contamination is generated at the leading edge portion of the paper. 
     In addition, there is a case of performing a so-called borderless print which prints an image until reaching an edge portion of the paper P without provision of a margin portion throughout the periphery of the edge portion of the paper P. 
       FIG. 5A  illustrates a bordered print (hereinafter, referred to as a normal print), and  FIG. 5B  illustrates a borderless print. During the bordered print, the toner image is entirely settled in the paper P and a peripheral margin, such as an upper margin (mh), a lower margin (mb), a left margin (ml), and a right margin (mr), exists around the paper P. 
     In contrast, during the borderless print, the toner image reaches up to the edge portion of the paper P and the peripheral margin disappears. Although  FIG. 5B  illustrates a state in which none of an upper margin, a lower margin, a left margin, and a right margin are, the borderless print, which does not have the margin at a portion of the edge portion, for example, does not have the only upper and lower margins, is also performed. In a case of performing such a borderless print, there is a problem in that the leading edge portion of the paper P comes into contact with the toner image before transfer which is retained on the photoconductor drum  31  and image omission is generated at the leading edge portion. 
     Image Forming Apparatus of Exemplary Embodiment 
       FIG. 2  is a schematic cross-sectional view partially illustrating principal parts of the paper feed device  20 , the paper transport device  40 , and one image forming unit  30  which constitute the paper transport path of the image forming apparatus  1  according to the exemplary embodiment. 
       FIG. 3A  is a perspective view illustrating the paper posture regulating member  45  when viewed from the surface side thereof,  FIG. 3B  is a perspective view illustrating a member holder portion and a film member which constitute the paper posture regulating member  45  when viewed from the back surface sides of the member holder portion and the film member, and  FIG. 3C  is a longitudinal cross-sectional view schematically illustrating the paper posture regulating member  45 . 
     The paper transport device  40  of the image forming apparatus  1  according to the exemplary embodiment includes the paper posture regulating member  45  to regulate the paper P, which is transported from the pair of resist rollers  23  at the upstream side of a nip portion between the transport belt  41  and the image forming unit  30 (Y) of the furthest upstream side, being lifted from the transport belt  41 . 
     As shown in  FIGS. 3A and 3B , the paper posture regulating member  45  includes a member holder portion  46 , a film member  47  which comes into contact with the paper P at a leading edge portion thereof to regulate a transport posture of the paper P, bearings  48  to pivotably support shaft portions  46   a  formed at opposite side ends of the member holder portion  46 , and spring members  49  to urge the member holder portion  46  and the film member  47  in a direction of being spaced apart from the upper surface side of the transport belt  41 . 
     As shown in  FIGS. 3B and 3C , the member holder portion  46  is formed so that a planar portion  46   b , to which the film member  47  is affixed at a front end side (paper transport downstream side) of the member holder portion  46 , extends in a width direction (a direction perpendicular to the transport direction; Y direction) of the paper P. 
     Each of the shaft portions  46   a , which is an entire pivot center of the paper posture regulating member  45 , is integrally formed at a rear end side (paper transport upstream side) of the member holder portion. 
     In addition, protrusion portions  46   c  are formed at opposite sides of the surface of the front end side (paper transport downstream side) of the member holder portion which faces a leading edge portion of the development housing  39  of the image forming unit  30 (Y) of the furthest upstream side. The member holder portion  46  may be integrally formed using, for example, a synthetic resin. 
     The film member  47  is made of an elastic material and formed to face the upper surface of the transport belt  41  while making a predetermined angle therewith. For this reason, the paper leading edge when the leading edge of the paper P passes through an edge  47   a  of the film member  47  of the paper transport direction downstream side is in linear contact while making a predetermined angle with the film member  47 , and the paper P is transported without being in surface contact with the planar portion of the film member  47 . 
     Specifically, the film member  47  may be made of a PET (polyethylene terephthalate) sheet having a thickness of approximately 0.1 mm to 0.2 mm. That is, when the leading edge of the paper P is rushed into a gap defined between the upper surface of the transport belt  41  and the edge  47   a  of the film member  47 , an impact occurring when coming into contact with the film member  47  is relieved and bending or curvature of the paper leading edge is prevented since the film member  47  has elasticity due to the thickness of approximately 0.1 mm to 0.2 mm. 
     In addition, since PET has high wear resistance, there is no case where the gap is enlarged due to wear even when the paper P is transported while the upper surface of the paper P comes into contact with the edge  47   a  of the film member. Furthermore, there is no case where an applied transfer bias voltage is leaked at a transfer nip portion to cause deterioration of transfer properties by insulating properties. 
     The bearings  48  support both side ends of the shaft portions  46   a  formed at the rear end side (paper transport upstream side) of the member holder portion  46  so as to be pivotable around central axes of the shaft portions. 
     Specifically, the bearings  48  are attached to a side frame constituting a housing of the paper transport device  40 , and pivotably support the member holder portion  46  and the film member  47  by the spring members  49  so that the member holder portion  46  and the film member  47  are urged with respect to the side frame in the direction of being spaced apart from the upper surface side of the transport belt  41 . 
     In addition, an opening and closing cover (opening and closing unit)  1   b  is provided at a front surface of the image forming apparatus  1 . As shown in  FIG. 4 , the opening and closing cover  1   b  is rotatable (openable and closable) about a pivot C provided at a lower portion of the front surface of the image forming apparatus  1 , with respect to an image forming apparatus  1  member. 
     The paper transport device  40  including the paper posture regulating member  45  is connected to the opening and closing cover  1   b , thereby moving by opening or closing the opening and closing cover  1   b  and coming into contact with or being separated from each image forming unit  30 . In a state of closing the opening and closing cover  1   b , the paper transport device  40  is positioned to face the image forming unit  30  in a state of being urged toward the image forming unit  30 . 
     When the paper transport device  40  is positioned to face the image forming unit  30  in a state of being urged toward the image forming unit  30 , the protrusion portions  46   c  of the member holder portion  46  of the paper posture regulating member  45  come into contact with the leading edge portion  39   a  of the development housing  39  of the image forming unit  30 (Y) and the paper posture regulating member  45  is positioned to face the transport belt  41 . 
     The paper posture regulating member  45  retains a preset gap defined between the edge  47   a  of the film member  47  and the upper surface of the transport belt  41  in a state of being positioned so that the protrusion portions  46   c  come into contact with the leading edge portion  39   a  of the development housing  39  of the image forming unit  30 (Y). 
     If the edge  47   a  of the film member  47  is operated in a state of being always in contact with the surface of the transport belt  41  which rotates and moves, there is a problem in that the surface of the transport belt  41  and the edge  47   a  of the film member  47  are worn or the paper P peels off from the film member  47  during transport of the thin paper. 
     Therefore, it is positioned to retain the gap of approximately 0.3 mm to 1.0 mm, preferably approximately 0.3 mm to 0.7 mm. 
     Since the paper posture regulating member  45  is positioned to face the transport belt  41  while the protrusion portions  46   c  of the member holder portion  46  come into contact with the leading edge portion  39   a  of the development housing  39  of the image forming unit  30 (Y), the related gap is retained with good precision. 
     In addition, even when the image forming unit  30 (Y) is exchanged or attached and detached, the image forming unit  30 (Y) is positioned so that the protrusion portions  46   c  of the member holder portion  46  come into contact with the leading edge portion  39   a  of the development housing  39  of the image forming unit  30 (Y). Accordingly, the related gap is retained with good precision regardless of the usage conditions of the image forming apparatus  1 . 
     Since the paper posture regulating member  45  is urged in the direction of being spaced apart from the upper surface side of the transport belt  41  by the spring members  49  in a state in which the opening and closing cover  1   b  is opened, the paper posture regulating member  45  is spaced apart from the upper surface side of the transport belt  41  around the central axes of the shaft portions  46   a  supported by the bearings  48 . 
     Accordingly, for example, in a case where paper blockage (paper jam) or the like is generated to thereby remove the jam by opening the opening and closing cover  1   b , since the paper posture regulating member  45  is spaced apart from the upper surface side of the transport belt  41  by the spring members  49 , the jam is easily removed and the film member  47  is not damaged by the removed paper P. 
     (3) Operation and Effect of Image Forming Apparatus and Paper Transport Device 
     In the image forming apparatus  1  according to the exemplary embodiment, in a case where a borderless print mode is selected, even when the paper P is supplied in a state of being slightly distorted in all directions, the size of the toner image on the photoconductor drum  31  is formed slightly larger than the size of the selected paper so that margins are not generated at the paper P. 
     The paper P sent out from the pair of resist rollers  23  is transported from the furthest upstream end (tension roller  42  side) of the transport belt  41  to the paper feed device  40 , and enters the gap defined between the film member  47  of the paper posture regulating member  45  and the upper surface of the transport belt  41 . 
     In this case, for the thick paper, the leading edge portion of the paper P is lifted from the surface of the transport belt  41  due to resilience of the paper P, but the lifting of the paper leading edge is regulated by the edge  47   a  of the film member  47  of the paper posture regulating member  45 . Therefore, the toner image of the upstream side of the transfer nip portion does not come into contact with the surface of the carried photoconductor drum  31  and the paper leading edge is transported to the nip portion between the transport belt  41  and the image forming unit  30 (Y) of the furthest upstream side, and thereby the toner image is transferred from the leading edge of the paper P without being omitted. 
     The gap between the edge  47   a  of the film member  47  and the upper surface of the transport belt  41  has approximately 0.3 mm to 1.0 mm, preferably approximately 0.3 mm to 0.7 mm. Consequently, the lifting of the leading edge of the thick paper is regulated, and the thin paper does not peel off by the related gap. 
     In addition, since the paper posture regulating member  45  is positioned so that the protrusion portions  46   c  come into contact with the leading edge portion of the development housing  39  of the image forming unit  30 (Y), the related gap is retained with good precision. 
     The film member  47  is made of the PET (polyethylene terephthalate) sheet having the thickness of approximately 0.1 mm to 0.2 mm. Therefore, when the leading edge of the paper P is rushed into the gap defined between the upper surface of the transport belt  41  and the edge  47   a  of the film member  47 , an impact occurring when coming into contact with the film member  47  is relieved and bending or curvature of the paper leading edge is prevented. 
     In addition, when the paper passes through the gap defined between the film member  47  and the upper surface of the transport belt  41  and the toner image of each color is transferred at the nip portion between the transport belt  41  and each of the image forming units  30 , there is no case where an applied transfer bias voltage is leaked at the transfer nip portion to cause deterioration of transfer properties. 
     In a case where paper blockage (paper jam) or the like is generated, the jam is removed by opening the opening and closing cover  1   b . In this case, since the paper posture regulating member  45  is rotated and spaced apart from the upper surface side of the transport belt  41  by the spring members  49 , the jam is easily removed and the film member  47  is not damaged by the removed paper P. 
     Although the exemplary embodiment of the present invention has been described above, the invention is not limited thereto. Various modifications may be made without departing from the spirit or scope of the invention described in the following claims. 
     Although the image forming apparatus  1  according to the exemplary embodiment has been described as a so-called tandem type color image forming apparatus, the invention is not limited thereto. If the image forming apparatus includes a transport belt which performs transfer and transport of toner images to paper sent out from a paper feed device, the above method may be used. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention 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 invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

Technology Category: 3