Patent Publication Number: US-8113515-B2

Title: Paper sheet transporting device and image forming apparatus using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2009-075058 filed Mar. 25, 2009. 
     BACKGROUND 
     1. Technical Field 
     This invention relates to a paper sheet transporting device and to an image forming apparatus using the paper sheet transporting device. 
     2. Related Art 
     In image forming apparatus such as printers and copiers utilizing a recording system such as an electrophotographic system, sometimes there is used a paper sheet transporting device with a configuration that holds (sucks) paper sheets to be used in image formation and transports the paper sheets through a constant section by sucking the paper sheets onto the outer peripheral surface of a rotating transport belt disposed with air holes. 
     SUMMARY 
     According to an aspect of the present invention, there is provided a paper sheet transporting device including: a transport belt having an endless belt that is wound around and rotates on support rolls and in which plural air holes are formed, the transport belt sucking a paper sheet onto an outer peripheral surface of that belt and transporting the paper sheet through a constant section; a suction duct that is disposed in a state where it exists at least in an inside space surrounded by an inner peripheral surface of the transport belt, the suction duct being equipped with a suction surface portion in which plural suction openings that face and open to the inner peripheral surface of the transport belt passing a paper sheet suction section are formed at intervals in an rotating axial direction of the transport belt and an air duct portion that is connected to an inner surface side of the suction surface portion and allows air taken in from the suction openings to pass through; and an air suction device that is connected via a connecting duct to the air duct portion of the suction duct and sucks air, wherein in the air duct portion of the suction duct, a suction confluence opening that collects the air that is sucked and allows the air to pass through is disposed in a position included in a region where the suction openings whose suction force is relatively the highest of the plural suction openings exist and which position is away from the inner surface side of the suction surface portion, with the air duct portion being formed in a shape where the opening cross-sectional area of that air duct becomes relatively narrower away from the suction confluence opening in the rotating axial direction of the transport belt. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the present invention will be described in detail below with reference to the drawings, wherein: 
         FIG. 1  is an explanatory diagram showing an overview of an image forming apparatus using a paper sheet transporting device pertaining to the exemplary embodiment; 
         FIG. 2  is a perspective view showing the paper sheet transporting device pertaining to the exemplary embodiment; 
         FIG. 3  is a top view showing a state where the paper sheet transporting device of  FIG. 2  is seen from above; 
         FIG. 4  is a perspective view showing a state where transport belts have been removed from the paper sheet transporting device of  FIG. 2 ; 
         FIG. 5  is a top view showing a state where the paper sheet transporting device of  FIG. 4  is seen from above; 
         FIG. 6  is a top view showing a state where a suction surface portion of a suction duct has been removed from the paper sheet transporting device of  FIG. 5 ; 
         FIG. 7  is a cross-sectional view along line Q 1 -Q 1  of the paper sheet transporting device of  FIG. 5 ; 
         FIG. 8  is a partial cross-sectional perspective view showing a portion along line Q 1 -Q 1  of the paper sheet transporting device of  FIG. 5 ; 
         FIG. 9  is a cross-sectional view along line Q 2 -Q 2  of the paper sheet transporting device of  FIG. 5 ; 
         FIG. 10  is a cross-sectional overview diagram schematically showing the configuration of the paper sheet transporting device of  FIG. 2 ; 
         FIG. 11  is a cross-sectional overview diagram schematically showing a state during the operation (action) of the paper sheet transporting device of  FIG. 2 ; 
         FIG. 12  is a graph showing results of investigating air suction amounts in four transport belts; 
         FIG. 13  is a cross-sectional overview diagram schematically showing another configural example of the paper sheet transporting device (a case where a suction duct with a different configuration is applied); 
         FIG. 14  is a cross-sectional overview diagram schematically showing another configural example of the paper sheet transporting device (a case where a suction duct with a different configuration is applied); 
         FIG. 15  is a cross-sectional overview diagram schematically showing another configural example of the paper sheet transporting device (a case where a suction duct and a connecting duct with different configurations are applied); and 
         FIG. 16  is a cross-sectional overview diagram showing the configuration of a suction duct of a comparative example. 
     
    
    
     DETAILED DESCRIPTION 
     A mode for implementing this invention (hereinafter simply called “exemplary embodiment”) will be described below with reference to the drawings. 
       FIG. 1  shows an overview of an image forming apparatus using a paper sheet transporting device pertaining to this exemplary embodiment, and  FIG. 2  to  FIG. 9  show all or part of that paper sheet transporting device.  FIG. 4  and  FIG. 5  show a state where transport belts have been removed, and  FIG. 6  shows a state where part (a suction surface portion) of a suction duct has been removed. Further,  FIG. 10  and  FIG. 11  schematically show that paper sheet transporting device. 
     An image forming apparatus  100  includes, as shown in  FIG. 1 , an image forming section  101  that is disposed within an unillustrated casing, a paper supply section  105  that houses and feeds recording paper sheets  9  to be supplied to the image forming section  101 , and a paper sheet transporting device  1  that is disposed in part of the image forming section  101 . Reference sign  106  in  FIG. 1  represents a control device that controls the operation of each component of the image forming apparatus  100 , and the arrowed one-dotted chain line represents a main transporting path of the recording paper sheets  9 . 
     The image forming section  101  is configured by an image creating device  110  that employs an intermediate transfer system and by a fixing device  140 . Of these, the image creating device  110  has a configuration where plural (in the present example, four) image creating units  120  (Y, M, C, K) that form toner images of mutually different colors (in the present example, a total of four colors of yellow (Y), magenta (M), cyan (C) and black (K)) are disposed in a state where they face the outer peripheral surface of an intermediate transfer belt  130  in the intermediate transfer system and where they are arranged in tandem at intervals in a rotational movement direction of the intermediate transfer belt  130 . 
     Each of the image creating units  120 Y,  120 M,  120 C and  120 K in the image creating device  110  is configured by a drum-form photoconductor  121  that is disposed so as to rotate and by a charging device  122 , an exposure device  123 , a developing device  124 , a primary transfer device  125  and a cleaning device  126  that are disposed around the photoconductor  121 . 
     The photoconductor  121  is configured by forming a photoconductive layer or the like configured by an organic sensitive material or the like on the peripheral surface of a circular cylinder of a conductive circular cylinder-shaped base material that is supported such that it may freely rotate and is grounded. The photoconductor  121  is driven to rotate at a required velocity in a required direction (direction indicated by the arrow) by the power of an unillustrated rotary drive device. The charging device  122  is configured by disposing a charging roll that contacts and rotates on at least an image formation valid region in an rotating axial direction of the photoconductor  121  and applying a charge-use voltage of only a direct current or an alternating current superimposed on a direct current to the charging roll from an unillustrated power source. 
     The exposure device  123  irradiates the photoconductor  121  with light corresponding to image information inputted to the image forming apparatus  100  to form an electrostatic latent image. As the exposure device  123 , for example, there is used a scanning type exposure device that is configured using a semiconductor laser and optical parts such as a polygon mirror or a non-scanning type exposure device that is configured using a light-emitting diode and optical parts. Image signals after the image information inputted to the image forming apparatus  100  has undergone required processing in an unillustrated image processing device are inputted to the exposure device  123 . 
     The developing device  124  supplies a developer (a toner) adapted to the development system to a development region of the photoconductor  121  to develop the electrostatic latent image. As the developing device  124 , for example, there is used a two-component developing device that performs reversal development using a two-component developer that includes a (nonmagnetic) toner and a (magnetic) carrier. The primary transfer device  125  is configured by disposing a primary transfer roll that contacts and rotates on at least the charged region in the rotating axial direction of the photoconductor  121  and applying a primary transfer-use voltage of the opposite polarity of the charge polarity of the toner to the transfer roll from an unillustrated power source. The cleaning device  126  is configured by a cleaning member such as an elastic plate that contacts the peripheral surface of the photoconductor  121  after transfer and a recovery container that recovers extraneous matter such as the toner removed by that cleaning member. 
     The intermediate transfer belt  130  is wound around plural support rolls  131   a ,  131   b  and  131   c , is supported such that it may freely rotate under a required tension, and is disposed in a state where it sequentially passes and moves through a primary transfer position between the photoconductor  121  and the transfer device  125  (the transfer roll) of each of the image creating units  120  of the image creating device  110 . The intermediate transfer belt  130  is rotated at a required velocity in a required direction (direction indicated by the arrows) by the drive-use roll  131   a  that is driven to rotate by an unillustrated drive device. 
     As the intermediate transfer belt  130 , there is used a belt that has been molded in an endless shape using a material such as resin or rubber that includes a conductive agent and has been prepared to a required volume resistivity. On the outer peripheral surface side of the portion of the intermediate transfer belt  130  that is supported by the secondary transfer support roll  131   c , there is disposed a secondary transfer roll  135  that contacts and rotates on the outer peripheral surface of that belt with a required pressure. A secondary transfer voltage is applied from an unillustrated power source to either one of the secondary transfer support roll  131   c  or the secondary transfer roll  135 . Further, on the outer peripheral surface side of the portion of the intermediate transfer belt  130  that is supported by the drive-use support roll  131   a , there is disposed an unillustrated cleaning device that cleans the outer peripheral surface of the intermediate transfer belt  130  after secondary transfer. 
     The fixing device  140  is configured by disposing, within a thermally insulated casing  141 , a roll-form or belt-form heat-applying rotor  142  that is driven to rotate in the direction indicated by the arrow and whose surface temperature is heated to a required temperature by heating means and which is held and a roll-form or belt-form pressure-applying rotor  143  that contacts the heat-applying rotor  142  with a required pressure substantially along an axial direction of the heat-applying rotor  142  and passively rotates. 
     In the image forming section  101 , there is disposed a paper supply path that is configured by plural paper sheet transporting roll pairs  138   a ,  138   b , etc. and a transporting guide member that transport the recording paper sheets  9  supplied from the paper supply section  105  to a secondary transfer position. Further, between the secondary transfer position and the fixing device  140 , there is disposed the paper sheet transporting device  1  that sucks the recording paper sheets  9  after secondary transfer onto a transport belt by suction and introduces the recording paper sheets  9  to the fixing device  140 . The details of the paper sheet transporting device  1  will be discussed later. In addition to this, there is disposed a discharge path that is configured by paper sheet transporting roll pairs and a transporting guide member that transport the recording paper sheets  9  discharged from the fixing device  140  toward an unillustrated paper discharge section. 
     The paper supply section  105  is configured by a paper sheet housing  151  that is disposed in an interior space of the unillustrated casing and by a feeding device  152  that feds the recording paper sheets  9  housed in the paper sheet housing  151  one sheet at a time. The paper sheet housing  151  is attached such that it may be freely loaded into and removed from the casing. 
     Image formation by this image forming apparatus  100  is performed as follows. Here, there will be supposed a case where full-color printing that forms a full-color image configured by toner images of the four colors of Y, M, C and K is requested, and the content of operation at that time will be described. 
     When full-color printing is requested, as shown in  FIG. 1 , in each of the image creating units  120  (Y, M, C, K) of the image creating device  110  in the image forming section  101 , the photoconductor drum  121  that begins rotating is charged to a predetermined potential by the charging device  122 , exposure based on the image signals is performed from the exposure device  123  on the photoconductor drum  121  after charging, such that an electrostatic latent image is formed in accordance with each color component, thereafter the electrostatic latent image is developed by the toner of the corresponding color in the developing device  124 , and a toner image of each color (Y, M, C, K) is formed. The toner images that have been formed by these image creating units  120  are electrostatically transferred such that they are sequentially superimposed on the intermediate transfer belt  130  in the primary transfer positions where the photoconductor drums  121  face the primary transfer devices  125 , and the toner images are thereafter transported to the secondary transfer position where that intermediate transfer belt  130  faces the secondary transfer roll  135 . 
     Next, when the recording paper sheet  9  transported at a required timing by the feeding device  152  from the paper supply section  105  is fed to the secondary transfer position in the image forming section  101 , the toner images on the intermediate transfer belt  130  are electrostatically transferred all at once to one side of the recording paper sheet  9 . The recording paper sheet  9  to which the toner images have been transferred is transported in a state where it is sucked onto a transport belt by the paper sheet transporting device  1  and is introduced to the fixing device  140  of the image forming section  101 . In the fixing device  140 , the paper sheet  9  to which the toner images have been transferred is subjected to heat and pressure when it passes through the contact portion between the heat-applying rotor  142  and the pressure-applying rotor  143 , whereby the toner images are fused and fixed to the paper sheet  9 . The recording paper sheet  9  after fixing has ended is discharged from the fixing device  140  and is thereafter transported to and collected in the unillustrated discharge section or the like. 
     As described above, a full-color image is formed on one side of one sheet of the recording paper sheet  9 . Further, when the formation of full-color images on several sheets is requested, the above-described operation is similarly repeated for the amount of sheets that have been requested. Moreover, in the image forming apparatus  100 , it is also possible to form a black-and-white image configured by a black color toner image by allowing only the black color image creating unit  120 K of the plural image creating units  102  to operate. 
     Next, the paper sheet transporting device  1  will be described. 
     The paper sheet transporting device  1  includes, as shown in  FIG. 2  and the like, four transport belts  2  (A, B, D, E), a suction duct  3  that is disposed in a state where it exists at least in an inside space surrounded by the inner peripheral surfaces of the four transport belts  2 , and a suction fan  6  that is connected to the suction duct  3 . In  FIG. 2  and the like, reference sign  11  represents a basal frame that configures part of the suction duct  3 , reference signs  12  and  13  represent attachment support frames, and reference signs SE 1  and SE 2  represent paper sheet detection sensors (detection windows) that detect the passage of the recording paper sheets  9 . 
     The transport belts  2  (A, B, D, E) are endless belts in which numerous suction holes  21  that penetrate the belts are formed in a state where they are substantially evenly distributed, the transport belts  2  are wound in a side-by-side state at a required interval m around two support rolls  25  and  26  that are disposed in a state where they are substantially parallel, and the transport belts  2  are disposed such that they rotate in the direction indicated by the dotted line arrow (see  FIG. 3 ). The two support rolls  25  and  26  respectively include a rotating shaft  25   a  and a rotating shaft  26   a , which are attached to the attachment support frame  12  such that they may freely rotate, and four elastic roll bodies  25   b  and four elastic roll bodies  26   b  that are fixed at the same intervals with respect to the rotating shaft  25   a  and the rotating shaft  26   a . The one support roll  26  is configured as a drive roll that obtains power from an unillustrated rotary drive device via a driven gear  27  and is driven to rotate. 
     The transport belts  2  (A, B, D, E) suck the recording paper sheets  9  onto outer peripheral surface portions on an upper side (in the direction of arrow Y 1 ) passing a required section (paper sheet suction section TA) between the two support rolls  25  and  26 . In this connection, the paper sheet transporting device  1  employs a so-called center registration transporting system where the paper sheet detection sensors SE 1  and SE 2  disposed in the center portion between the two transport belts  2 B and  2 D toward the center portion correspond to a center position in a width direction (direction substantially parallel to arrow Y) substantially orthogonal to the paper sheet transporting direction (direction substantially parallel to arrow X 1 ) and where the paper sheet transporting device  1  regulates the transport position and transports the recording paper sheets such that feed width center portions of various types of the recording paper sheets  9  pass a certain center position of these sensors. 
     The suction duct  3  is equipped with a suction surface portion  31  in which plural suction openings  32  and  33  that face and open to the inner peripheral surfaces of the transport belts  2  passing the paper sheet suction section TA are formed and an air duct portion  35  that is connected to an inner surface side of the suction surface portion  31  and allows air taken in from the suction openings  32  and  33  to pass through. 
     The suction fan  6  is connected to (the air duct portion  35  of) the suction duct  3  via a connecting duct  7  and has the function of sucking air such that the air is drawn (through the air duct portion  35 ) toward the fan  6  by blade members  62  that are rotated at a required rotational speed by the power of a motor or the like in the interior space of a casing  61 . Further, the suction fan  6  has a structure where it expels the air it has sucked to the outside of the image forming apparatus  100  via an unillustrated exhaust duct or the like (see  FIG. 3 ). The suction fan  6  in this exemplary embodiment is disposed in a position on the outside a little away from the end portion of the suction duct  3  on the side where the transport belt  2 A is disposed. One part of the connecting duct  7  is configured using a square duct  71  whose opening cross-sectional shape is substantially square between the suction fan  6  and the suction duct  3  (see  FIG. 7  and  FIG. 8 ). The remaining configural portion ( 73 ) of the connecting duct  7  will be discussed later. Reference sign in  FIG. 3  and the like is a connecting portion (clearance-filling elastic material or the like) for interconnecting one end portion of the square connecting duct  71  and (a connecting portion of the casing  61  of) the suction fan  6 . 
     The suction surface portion  31  of the suction duct  3  is configured by forming the plural (in the present example, roughly a total of four) suction openings  32  and in a state where they penetrate a flat plate-shaped member. 
     The suction openings  32  and  33  are formed at intervals in an rotating axial direction of the transport belts  2  (direction substantially parallel to the direction of arrow Z); in this exemplary embodiment, the suction openings  32  and  33  are formed in a relationship where at least one suction opening exists in correspondence to each of the four transport belts  2 . The two suction openings  32  are formed in correspondence to the two transport belts  2 B and  2 D on the center side and are formed such that their opening area is relatively wide. Further, the two suction openings  33  are formed in correspondence to the two transport belts  2 A and  2 E on both end portion sides and are formed such that their opening area is relatively narrower than that of the suction openings  32 . 
     Further, the suction openings  32  and the suction openings  33  are set to dimensions where the lengths of their openings overall with respect to the paper sheet transporting direction (direction substantially parallel to arrow X 1 ) indicated by the arrowed one-dotted chain line in the paper sheet transporting section TA are mutually the same but where the widths of their openings overall with respect to the rotating axial direction of the transport belts  2  are different (dimensions where the widths of the suction openings  33  are shorter than those of the suction openings  32 ). Moreover, gratings are disposed within the spaces of the openings of the suction openings  32  and the suction openings  33 ; thus, for example, traveling stability of the transport belts  2  is ensured (e.g., a situation where the transport belts  2  are deformed by suction so as to sag is prevented). 
     A surface  34  having the property that it is easy for the transport belts  2  to slide thereon is formed on the portion of the outer surface (top side) of the suction surface portion  31  surrounding the suction openings  32  and the suction openings  33  in order to ensure that the transport belts  2  do not encounter unnecessary frictional resistance and that their traveling stability is not adversely affected when parts of the transport belts  2  such as their end portions contact the suction surface portion  31 . Further, detection-use windows (openings) for the paper sheet detection sensors SE 1  and SE 2  are formed in portions of the surface  34  that are between the two suction openings  32  toward the center and are on an upstream side and a downstream side in the paper sheet transporting direction. 
     The suction duct  3  in this exemplary embodiment is formed as a structure including a boxlike shape whose outer appearance is substantially rectangular. 
     Specifically, the suction duct  3  has a structure where the suction surface portion  31  is given a cover-like shape in which frame-shaped side plate portions  31   b  to  31   d  ( FIG. 4  and  FIG. 9 ) are formed around three sides of a flat plate-shaped portion  31   a  with that rectangular shape and where those side plate portions  31   b  to  31   d  are attached to and disposed on the tabular basal frame  11 . Thus, the suction duct  3  has a structure where its outer appearance overall has a substantially rectangular boxlike shape because of the combination of the suction surface portion  31  with the cover-like shape and the flat plate-shaped basal frame  11 . Further, the suction duct  3  whose outer appearance includes the boxlike structure has, within that structure, a rectangular interior space S (strictly speaking, an interior space in a state where one side surface portion of the suction surface portion  31  where no side plate portion is formed is open) (see  FIG. 7  to  FIG. 9  and the like). 
     In the air duct portion  35  of the suction duct  3 , as shown in  FIG. 7 , a suction confluence opening  36  that collects the air that is sucked and allows the air to pass through is disposed in a position included in a region VA where the two suction openings  32  whose suction force is relatively the highest of the four suction openings  32  and in the suction surface portion  31  exist and which position is away from an inner surface  31   r  side of the suction surface portion  31 . Moreover, the air duct portion  35  is formed ( 35 A,  35 B) in a shape where an opening cross-sectional area M of that air duct becomes relatively narrower (Ma&gt;Mb) away from the suction confluence opening  36  in the rotating axial direction of the transport belts  2  (see  FIG. 7 ,  FIG. 8  and  FIG. 10 ). 
     Here, the region VA where the two suction openings  32  whose suction force is relatively the highest exist is a region of a scope that combines the regions occupied by the suction openings  32 , the region existing between the two suction openings  32  and the regions of the surrounding portions of the suction openings  32 . In other words, it suffices for the region VA to be within a scope where the suction air that is to pass through the suction confluence opening  36  efficiently reaches the two suction openings  32 . In this exemplary embodiment, the suction confluence opening  36  is disposed such that it is positioned in the center portion between the two suction openings  32  that are located toward the center. If there were one suction opening whose suction force was relatively the highest, then it would suffice for the region VA in which that suction opening existed to be within the region occupied by that suction opening or a region that also included the region of the surrounding portion of that suction opening. 
     In this exemplary embodiment, because of the relationship where the suction duct  3  is formed as the boxlike structure as mentioned previously, as shown in  FIG. 6  to  FIG. 10  and the like, one surface (the top surface) of the boxlike structure of the suction duct  3  is formed as the suction surface portion  31 , and the suction confluence opening  36  and the air duct portion  35  ( 35 A,  35 B) are formed by disposing two partition plates  41  and to partition the interior space S of that boxlike structure. Moreover, at least one part ( 73 ) of the connecting duct  7  that connects to (the air duct portion  35 A of) the suction duct  3  of the suction fan  6  is formed by the one partition plate  41 . The suction duct  3  has, speaking from a different point of view, a two-layer structure where the interior space S of that boxlike structure is divided in two in the vertical direction by the two partition plates  41  and  42 . 
     The two partition plates  41  and  42  includes, as shown in  FIG. 6 ,  FIG. 7  and the like, shapes having rectangular flat plate portions  41   a  and  42   a , and the two partition plates  41  and  42  are disposed in a state where one end portion  41   b  and one end portion  42   b  of each in the rotating axial direction of the transport belts  2  are distanced from one inner surface (a top surface  11   a  of the basal frame  11 ) that faces the inner surface  31   r  side of the suction surface portion  31  and in a state where the one end portion  41   b  and the one end portion  42   b  are a required interval k apart from each other in a position between the two suction openings  32 . Thus, the space of the square clearance existing between the end portions  41   b  and  42   b  of the two partition plates  41  and  42  is formed as the suction confluence opening  36 . 
     Further, the two partition plates  41  and  42  are, as shown in  FIG. 7 ,  FIG. 8 ,  FIG. 10  and the like, disposed in a state where they are slanted so as become closer to (the inner surface  31   r  of) the suction surface portion  31  away from the positions of the one end portion  41   b  and the one end portion  42   b  in the rotating axial direction of the transport belts  2 . Thus, the two spaces existing between the partition plates  41  and  42  and the suction surface portion  31  are formed as air duct portions  35 A and  35 B. At this time, end portions  41   c  and  42   c  of the two partition plates  41  and  42  on the opposite side that respectively oppose the one end portion  41   b  and the one end portion  42   b  are attached to, in a state they have been brought into contact with, (the inner surface  31   r  of) the suction surface portion  31 . Thus, each of the air duct portions  35 A and  35 B has a shape where the opening cross-sectional area M of that air duct becomes relatively narrower (Ma&gt;Mb) away from the suction confluence opening  36  in the rotating axial direction of the transport belts (see  FIG. 10 ). In this exemplary embodiment, the size of the opening cross-sectional area of the air duct portion  35  is set by giving the air duct portion  35  a dimension where its height is different because its length in the paper sheet transporting direction is substantially the same. 
     Moreover, the space existing between the one partition plate  41  of the two partition plates  41  and  42  and the inner surface  11   a  of the basal frame  11  of the suction duct  3  of the boxlike structure is formed as the at least one part ( 73 ) of the connecting duct  7 . The connecting duct  73  configured by this partition plate  41  and the inner surface  11   a  of the basal frame  11  is formed in a shape where the opening cross-sectional area M of that duct becomes wider (Md&lt;Me) closer to the suction fan (or the square connecting duct portion  71 ) from the suction confluence opening  36  (see  FIG. 10 ). In this exemplary embodiment, the size of the opening cross-sectional area of the connecting duct  73  is set by giving the connecting duct  73  a dimension where its height is different because its length in the paper sheet transporting direction is substantially the same. 
     Further, in this exemplary embodiment, as shown in  FIG. 6 ,  FIG. 9  and the like, as the two partition plates  41  and  42 , there are used side-plated members where the flat plate portions  41   a  and  42   a  are given shapes with a dimensional relationship in which their length in the paper sheet transporting direction is shorter than the length of the suction surface portion  31  and where cross-sectionally L-shaped side plates  43  and  44  that reach and contact the inner surface  11   a  of the basal frame  11  are respectively formed on side portions of those flat plate portions  41   a  and  42   a  on both sides in the rotating axial direction of the transport belts  2 . Additionally, these side-plated partition plates  41  and  42  are, as shown in  FIG. 9 , attached and disposed in a state where clearances with substantially the same breadth respectively exist between those two side plates  43  and  44  and inner surfaces of the side plate portions  31   c  and  31   d  of the suction surface portion  31  of the suction duct  3  on the upstream side and the downstream side in the paper sheet transporting direction, whereby the spaces of those two clearances are formed as parts (an upstream side duct portion  35 D and a downstream side duct portion  35 D) of the air duct portion  35 . The upstream side duct portion  35 C and the downstream side duct portion  35 D are spaces respectively connected to the suction confluence opening  36 , the air duct portions  35 A and  35 B, and the air duct portion that is the one part  73  of the connecting duct  7 . 
     The paper sheet transporting device  1  including the above configuration operates as follows. 
     First, the drive-use support roll  26  is driven to rotate, whereby the four transport belts  2  rotate in the direction indicated by the dotted line arrow ( FIG. 2 ). At substantially the same time as this, the suction fan  6  is driven, whereby the suction fan  6  sucks air through the suction duct  3  as indicated by the arrows in  FIG. 11 . 
     At this time, the air suction force of the suction fan  6  acts on the suction confluence opening  36  that is the initially open portion of the suction duct  3  through the connecting duct  7  ( 71 ,  73 ) as indicated by the fat white arrow in  FIG. 11 . 
     Next, the air suction force of the suction fan  6  reaches the air duct portions  35 A and  35 B that lead to the suction confluence opening  36  in the suction duct  3  and extend in mutually opposite directions along the rotating axial direction of the transport belts  2 , and, at this time, as indicated by the solid line arrows in  FIG. 11 , the suction force of the suction fan  6  acts relatively more strongly on the suction openings  32  in the suction surface portion  31  that are positioned in the portions close to the suction confluence opening  36  where the cross-sectional opening area Ma is relatively wide than on the suction openings  33 . In contrast, the air suction force of the suction fan  6  acts relatively more weakly on the suction openings  33  that are positioned in the portions away from the air confluence opening  36  where the cross-sectional opening area Mb is relatively narrow than on the suction openings  32  as indicated by the dotted line arrows in  FIG. 11 . Particularly the suction openings  33  are formed such that the opening area thereof is narrower than that of the suction openings  32 , so the degree to which the air suction force of the suction fan  6  reaches the suction openings  33  becomes weak. 
     As a result of this, in the suction duct  3 , the suction force becomes relatively high (strong) at the two suction openings  32  that are located toward the center of the suction surface portion  31  in the rotating axial direction of the transport belts  2  because more air is taken in from outside the duct, and, on the other hand, the suction force becomes relatively low (weak) at the two suction openings  33  that are located on the outer sides of the suction openings  32  because the amount of air that is taken in from outside the duct becomes less. Thus, as a result of the strong suction force of the suction openings also reaching the air holes  21  in the belts, the suction force at the outer peripheral surfaces of the two transport belts  2 B and  2 D that pass the suction openings  32  corresponding also to the paper sheet suction section TA and rotate becomes stronger than the suction force at the outer peripheral surfaces of the two transport belts  2 A and  2 E that pass the suction openings  33  and rotate. 
     In the paper sheet transporting device  1  that has this strong and weak suction force relationship, the recording paper sheet  9  to be transported is relatively strongly sucked and transported by the two transport belts  2 B and  2 D toward the center. For this reason, the recording paper sheet  9  that is regulated by center registration and transported is stably transported because its feed width center portion is always strongly sucked onto the outer peripheral surfaces of the transport belts  2 . When, for example, a recording paper sheet  9  with a relatively narrow feed width such as a postcard that is sucked and transported in a state where it straddles the two transport belts  2 B and  2 D is to be transported, the recording paper sheet  9  becomes reliably sucked onto those transport belts  2 B and  2 D, and stable transport becomes possible. 
     Further, when a recording paper sheet  9  with a relatively wide feed width that is transported in a state where it straddles the four transport belts  2  is to be transported, the recording paper sheet  9  becomes transported in a state where both end portions in the feed width thereof are relatively weakly sucked onto the two transport belts  2 A and  2 E whose suction force is weak. For this reason, the paper sheet  9  with that feed width is held such that both its right and left end portions in the transporting direction do not rise from the outer peripheral surfaces of the transport belts  2  to enable excellent transport. 
     Further, in this paper sheet transporting device  1 , the upstream side duct portion  35 C and the downstream side duct portion  35 D are formed as air duct portions in the suction duct  32  (see  FIG. 9 ), so some of the suction force of the suction fan  6  through the connecting ducts  71  and  73  also reaches and acts on the upstream side duct portion  35 C and the downstream side duct portion  35 D through the suction confluence opening  36 . At this time, the suction force becomes somewhat larger in the upstream side duct portion  35 C and the downstream side duct portion  35 D than in the air duct portions  35 A and  35 B because of the relationship where the cross-sectional opening height dimension of the upstream side duct portion  35 C and the downstream side duct portion  35 D is larger than that of the air duct portions  35 A and  35 B (see  FIG. 9 ). For this reason, at the end portions of the suction openings  32  and on the upstream side and the downstream side in the paper sheet transporting direction in the paper sheet suction section TA of the suction surface portion  31  of the suction duct  3 , a suction force that is slightly stronger than that of the region on the center portion side in the paper sheet transporting direction arises and also reaches the transport belts  2 , and, as a result of that, it becomes difficult for the feed direction leading end portion and trailing end portion of the recording paper sheet  9  to be transported to rise with respect to the outer peripheral surfaces of the transport belts  2 , and the recording paper sheet  9  is transported in a state where it is excellently sucked. 
     Moreover, in this paper sheet transporting device  1 , the one part  73  of the connecting duct  7  of the suction fan  6  is formed in a state where it is incorporated in part of the suction duct  3 , so there becomes less of a need to ensure a dedicated space for disposing the connecting duct  7 . Further, the connecting duct  73  is formed in a relationship (Md&lt;Me) where the cross-sectional opening area M thereof becomes relatively wider closer to the suction fan  6  from the suction confluence opening  36  side, so it becomes difficult for the suction force of the suction fan  6  to be lost, and the suction force of the suction fan  6  efficiently reaches the suction confluence opening  36 . For this reason also, the suction force in the transport belts  2  stably occurs, so stable paper sheet transport becomes possible. 
       FIG. 12  shows results of investigating suction amounts in the four transport belts  2 A,  2 B,  2 D and  2 E. The suction amounts at this time are obtained by measuring air inflow amounts in the suction openings  32  and  33  in the suction duct  3  when the suction fan  6  is driven. Further, for comparison, a paper sheet transporting device using a duct (comparative example) where, as shown in  FIG. 16 , the partition plates  41  and  42  are not disposed and the interior space S is not partitioned is manufactured, and the suction amounts thereof are similarly investigated. 
     Other Exemplary Embodiments 
     In the preceding exemplary embodiment, as shown in  FIG. 7  and  FIG. 10 , the paper sheet transporting device  1  has a structure where, in the suction duct  3 , a space  35 G exists between the partition plate  42  and the basal frame  11  and a clearance SA exists between the end portion  42   b  of that partition plate  42  and the basal frame  11 , but the paper sheet transporting device  1  may also be given a structure where that clearance SA is closed off by a plate material, for example. When the paper sheet transporting device  1  is given this closed-off structure, the suction force passing through the connecting duct  7  ( 71 ,  73 ) of the suction fan  6  efficiently concentrates in the suction confluence opening  36 , and the suction force becomes substantially evenly distributed with respect to the air duct portions  35 A and  35 B that extend antithetically in directions away from each other in the rotating axial direction of the transport belts  2  about the suction confluence opening  36 . 
     Further, in the preceding exemplary embodiment, a case has been described where partition plates with shapes having the side plates  43  and  44  are applied as the partition plates  41  and  42  configuring the air duct portion  35  in the suction duct  3 , but the air duct portion  35 —and therefore the suction duct  3 —can also be configured by using partition plates  41  and  42  without those side plates  43  and  44  and disposing them in a state where their end portions on the upstream side and the downstream side in the paper sheet transporting direction have been brought into contact with the side plate portions  31   c  and  31   d  of the suction surface portion  31 . In this case, the air duct portion includes only the air duct portions  35 A and  35 B that are formed between those partition plates  41  and  42  and the suction surface portion  31 , and the upstream side duct portion  35 C and the downstream side duct portion  35 D (see  FIG. 9 ) in the paper sheet transporting direction no longer exist. Even in the case of the suction duct  3  with this configuration, as mentioned previously, the suction force of the two transport belts  2 B and  2 D toward the center becomes relatively higher than that of the other transport belts  2 . 
     Moreover, in the preceding exemplary embodiment, a case has been described where the paper sheet transporting device  1  is configured such that the partition plates  41  and  42  with shapes having the side plates  43  and  44  are disposed in substantially the center portion in the paper sheet transporting direction in the interior space of the suction duct  3  such that the upstream side duct portion  35 C and the downstream side duct portion  35 D with substantially the same breadth are formed, but the paper sheet transporting device  1  can also be configured such that those partition plates  41  and  42  are disposed not in that center portion but in a state where they are further on the upstream side or the downstream side in the paper sheet transporting direction such that an upstream side duct portion  35 C and a downstream side duct portion  35 D with different opening cross-sectional areas are formed. In this case, the suction force strongly reaches the duct portion whose opening cross-sectional area is wider, and the suction force of the portions of the suction openings  32  and  33  corresponding to that duct portion can be adjusted to relatively different strengths. 
     Further, it is also possible to give the suction openings  32  and  33  in the suction surface portion  31  of the suction duct  3  the same opening area and shape. Further, the suction openings  33  can also be formed as independent open portions that exist independently on the upstream side and the downstream side in the paper sheet transporting direction, for example. 
     Further, the suction duct  3  may also, as shown in  FIG. 13 , be configured such that plural (in this example, two) suction confluence openings  36 A and  36 B are disposed as suction confluence openings. Even when the suction duct  3  is configured in this manner, the suction force at the two transport belts  2 B and  2 D toward the center becomes relatively the strongest. 
     In this case, the suction duct  3  may be configured such that a partition plate  45  that has been placed in a state where it is substantially parallel to the basal frame  11  is disposed between the plural suction confluence openings  36 A and  36 B and such that a space whose opening cross-sectional area is substantially the same between that partition plate  45  and the suction surface portion  31  is formed as a dedicated air duct portion  35 H within the region VA whose suction force is to be the highest. Additionally, the suction duct  3  may be configured such that the partition plates  41  and  42  located in directions on both end sides of the suction confluence openings  36 A and  36 B in the rotating axial direction of the transport belts  2  are disposed in a state where they are slanted so as to become closer to the suction surface portion  31  away from the suction confluence openings  36 A and  36 B so that the air duct portions  35 A and  35 B are formed. Further, in this case, the space portions between the partition plates  41  and  45  and the basal frame  11  are formed as parts  73 A and  73 B of the connecting duct  7 . However, it is good for the suction duct  3  to be given a structure where the clearance SA in the one end portion  42   b  of the partition plate  42  of the space portion  35 G between the partition plate  42  and the basal frame  11  to be closed off by a closure plate  46 . 
     Further, it is also possible, as shown in  FIG. 14 , to dispose a filter member  39  for dust collection within the air duct portions  35 A and  35 B of the suction duct  3 . In this case, it is good to set a filter member whose air permeability is high and through which it is difficult for a flow of flowing air to be hindered as the filter member  39 . When this filter member  39  is disposed, toner and dust floating within the image forming apparatus  100  can be trapped by the filter member  39  even when unfixed toner or the like held on the recording paper sheet  9  to be transported has been drawn into the suction duct  3 ; thus, toner and the like can be prevented from being released to the outside of the image forming apparatus  100  through the suction fan  6  from the suction duct  3 . Even when this filter member  39  is disposed, the suction force of the two transport belts  2 B and  2 D toward the center becomes relatively stronger than that of the other transport belts. 
     Moreover, it is also possible, as exemplified in  FIG. 15 , to configure the suction duct  3  and the connecting duct  7  as independent separate structures. In this case, the suction duct  3  becomes a structure configured by the suction surface portion  31  and the two plate members  41  and  42 . Further, the connecting duct  7  may be configured such that a duct portion  75  that connects to the suction confluence opening  36  in the suction duct  3  is disposed in a state where it passes through the interior space of the transport belts  2 A and  2 B and projects from a side portion thereof and such that the duct portion  75  is connected directly or via the other connecting duct portion  71  to the suction fan  6 . In this case, the space portion  35 G (see  FIG. 10 , etc.) that is not directly related to air passage like the suction duct  3  in the preceding exemplary embodiment no longer exists. Further, it is good for the connecting duct portion  75  disposed within the interior space of the transport belts  2  to be given the relationship (Md&lt;Me) where the cross-sectional opening area M thereof becomes wider closer to the suction fan  6  from the suction confluence opening  36 . Moreover, it is also possible to configure this connecting duct portion  75  such that part of the connecting duct portion  75  is formed by the plate member  41  of the suction duct  3 . 
     Further, in regard to the transport belts  2 , the paper sheet transporting device  1  is not limited to having plural transport belts and may also have one transport belt. In this case, the suction openings in the suction surface portion  31  of the suction duct  3  may be plurally formed at intervals in the rotating axial direction of the transport belt. Additionally, some of those plural suction openings may be selected as suction openings whose suction force is to be the highest. 
     Moreover, the paper sheet transporting device  1  and the image forming apparatus  100  can also be configured such that the control device  106  or the like performs control to adjust the air suction force of the suction fan  6  in accordance with the type or the like of the paper sheets  9  to be transported. For example, when the recording paper sheets  9  include thin paper, and particularly when transporting thin paper with a wide feed width, there is the fear that the suction force with respect to the center portion thereof will be too strong and that wrinkles will arise, but by adjusting the air suction force to weaken the air suction force overall by performing control such as lowering the rotational speed of the suction fan  6 , more stable paper sheet transport becomes possible. Conversely, when transporting thick paper or the like having a width where the paper is sucked onto and transported only by the transport belts  2  in the region where the suction force is high, it becomes possible to optimally cause the thick paper to be sucked onto and transported by the transport belts  2  by performing control such as raising the rotational speed of the suction fan  6 . 
     In addition, in the preceding exemplary embodiment, there has been exemplified the image forming apparatus  100  that employs an intermediate transfer system as the image creating units  120 , but the image creating units  120  may also be of a system that directly transfers the toner images formed on the photoconductors  121  in the image creating units  120  (Y, M, C, K) to the recording paper sheets  9  transported by a paper sheet transport belt or the like. Further, the image creating units  120  in the image forming apparatus  100  may be configured by a single image creating unit that does not employ an intermediate transfer format or may be configured by image creating units of a plural number other than four. Moreover, the image forming apparatus is not limited to an image forming apparatus having the image forming section  101  of a system that forms images configured by the toner (the developer) and may also be an image forming apparatus having an image forming section of another image formation system (e.g., inkjet system, printing system, etc.). 
     Further still, it is also possible for the paper sheet transporting device  1  to be used in an apparatus other than the image forming apparatus  100  having a section that performs paper sheet transport. As long as the paper sheets are capable of being sucked by suction onto the outer peripheral surface of a transport belt and transported, the material, shape and structure of the paper sheets are not particularly restricted. 
     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 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.