Patent Publication Number: US-2011069115-A1

Title: Image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2009-217377 filed Sep. 18, 2009. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to an image forming apparatus. 
     2. Summary 
     An image forming apparatus of an aspect of the present invention includes: a transport body that rotates while retaining a recording medium on an outer surface thereof; a liquid droplet ejection head that ejects liquid droplets onto the recording medium retained on the transport body; a collection unit, provided at a downstream side in a rotation direction of the transport body with respect to the liquid droplet ejection head and provided with a suction inlet through which a mist of the liquid droplets is sucked, that collects the mist sucked in from the suction inlet; and a guide member, provided between the suction inlet and the liquid droplet ejection head, that guides the mist toward the suction inlet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiment of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is an enlarged cross-section showing a collection device and a guide member employed in an image forming apparatus according to an exemplary embodiment of the present invention; 
         FIG. 2  is a cross-section showing a collection device and a guide member employed in an image forming apparatus according to an exemplary embodiment of the present invention; 
         FIG. 3  is a perspective view showing a collection device and a guide member employed in an image forming apparatus according to an exemplary embodiment of the present invention; 
         FIG. 4  is an enlarged perspective view showing a collection device and a guide member employed in an image forming apparatus according to an exemplary embodiment of the present invention; 
         FIG. 5  is a diagram showing simulation results of air flow in the vicinity of a collection device and a guide member employed in an image forming apparatus according to an exemplary embodiment of the present invention; 
         FIG. 6  is a schematic configuration diagram showing an image forming apparatus according to an exemplary embodiment of the present invention; and 
         FIG. 7  is a perspective view showing a support frame, on which liquid droplet ejection heads employed in an image forming apparatus according to an exemplary embodiment of the present invention are supported. 
     
    
    
     DETAILED DESCRIPTION 
     Explanation will now be given of an example of an image forming apparatus according to an exemplary embodiment of the present invention, with reference to  FIG. 1  to  FIG. 7 . 
     Overall Configuration 
     As shown in  FIG. 6 , an inkjet recording apparatus  10 , serving as an image forming apparatus, includes: a paper feed unit  12  in which a sheet member P is accommodated as a recording medium prior to recording with an image; an image recording unit  14  that records an image on the sheet member P fed from the paper feed unit  12 ; a transfer unit  16  that transfers the sheet member P to the image recording unit  14 ; and a paper discharge unit  18  that accommodates the sheet member P that is recorded with an image by the image recording unit  14  and transferred by the transfer unit  16 . 
     Transfer Unit 
     The transfer unit  16  includes: a cylindrical take-up drum  24  that, while rotating, takes out the sheet member P accommodated in the paper feed unit  12  one sheet at a time, and retains the sheet member P on its outer surface; a cylindrical transport drum  26 , serving as an example of a transport body, receives the sheet member P from the take-up drum  24  while rotating, and transports the received sheet member P, while retaining the sheet member P on its outer surface, to a position facing the image recording unit  14 ; and a feed-out drum  28  that, while rotating, receives the sheet member P recorded with an image by the image recording unit  14  from the transport drum  26 , and, while retaining the sheet member P on its outer surface, feeds the received sheet member P to the paper discharge unit  18 . 
     More precisely, the outer surfaces of the take-up drum  24 , the transport drum  26 , and the feed-out drum  28  are configured so as to retain the sheet member P using an electrostatic attraction device, or a non-electrostatic attraction device, such as one using suction, tackiness, or the like. 
     In each of the outer surfaces of the take-up drum  24 , the transport drum  26 , and the feed-out drum  28 , two concave shaped recess portions  24 A, two concave shaped recess portions  26 A, two concave shaped recess portions  28 A are formed respectively. The two recess portions  24 A,  26 A,  28 A are provided on two respective sides of each rotation shaft  32  for the drums  24 ,  26 ,  28 , and the recess portions  24 A,  26 A,  28 A extend along the axial direction of the rotation shafts  32 . Rotation shafts  34  are provided within the recess portions  24 A,  26 A,  28 A, parallel to the rotation shafts  32  of each of the drums  24 ,  26 ,  28 . 
     There are also plural retaining fittings  30  disposed in the respective recess portions  24 A,  26 A,  28 A and disposed at specific intervals along the axial direction of the rotation shafts  34 . The retaining fittings  30  are provided, at their leading ends, with retaining portions  30 A that protrude out from the outer surface of each of the drums  24 ,  26 ,  28 , nipping and retaining the leading end of the sheet member P between the outer surface of the drum. The base end portions of these retaining fittings (the end portion at the opposite side to that of the retainer  30 A) are fixed to the respective rotation shafts  34 . 
     The rotation shafts  34  are rotated in both forward and reverse directions by non-illustrated actuators, and the retaining fittings  30  rotate in both forward and reverse directions along the circumferential direction of the respective drums  24 ,  26 ,  28 . The retaining portions  30 A of the retaining fittings  30  retain the sheet member P, or remove the sheet member P, by rotation of the retaining fittings  30  in the forward or reverse directions. 
     In other words, by projecting the retaining portions  30 A, provided at the retaining fittings  30 , out from the outer surfaces of the respective drums  24 ,  26 ,  28  and by rotationally moving the retaining portions  30 A, the sheet member P can be handed over from the retaining fittings  30  of the take-up drum  24  to the retaining fittings  30  of the transport drum  26 , at a hand-over position  36  where the outer surface of the take-up drum  24  faces the outer surface of the transport drum  26 , and further, the sheet member P can also be handed over from the retaining fittings  30  of the transport drum  26  to the retaining fittings  30  of the feed-out drum  28  at a hand-over position  38  where the outer surface of the transport drum  26  faces the outer surface of the feed-out drum  28 . 
     Image Recording Unit 
     The image recording unit  14  is disposed facing the transport drum  26 . Liquid droplet ejection heads  20 Y,  20 M,  20 C, and  20 K, that form images on the sheet member P by ejecting liquid droplets, of each of the colors Y (yellow), M (magenta), C (cyan), and K (black), onto the sheet member P retained on the outer surface of the transport drum  26 , are disposed along the rotation direction of the transport drum  26 , in this sequence from the downstream side. 
     Note that in the explanation that follows, the capital letter corresponding to each of the colors will be added when the different colors are differentiated, however these capital letters corresponding to the colors will be omitted when there is no particular differentiation made. 
     Each liquid droplet ejection head  20  is equipped with nozzle a face  22  formed with nozzles (not shown in the drawings) that eject liquid droplets. A support stand  40 , as shown in  FIG. 7 , is provided facing the transport drum  26 , such that the nozzle faces  22  of the liquid droplet ejection heads  20  are supported facing the outer surface of the transport drum  26 . 
     The support stand  40  is provided with a substantially rectangular frame  42 , and four pairs of raising and lowering guides  44 ,  46 . The raising and lowering guides  44 ,  46  are fixed to the frame  42  and are provided in substantially radial manner with respect to the axial line of the transport drum  26 , with the two side edge portions of each of the liquid droplet ejection heads  20  fitting into the raising and lowering guides  44 ,  46 . 
     Furthermore, as shown in  FIG. 6 , a collection device  50  is provided downstream side of the liquid droplet ejection head  20 Y in the transport drum  26  rotation direction. The collection device  50  serves as one example of a collection unit that collects mist of liquid droplets ejected from the liquid droplet ejection heads  20  (liquid droplets ejected from the nozzles that rise up in a mist form). 
     Configuration of Main Portion 
     Explanation will now be given of the collection device  50  that collects mist of liquid droplets ejected from the liquid droplet ejection heads  20 , and the like. 
     As shown in  FIG. 1  and  FIG. 2 , the collection device  50  is provided with a box shape casing  50 A that extends along the axial direction of the rotation shaft  32  of the transport drum  26  (the direction into and out of the paper in the diagrams, referred to below simply as “axial direction”), facing the outer surface of the transport drum  26  across the entire axial direction length thereof. A substantially L-shaped fixing member  56  that extends along the axial direction is fixed to the top face of the collection device  50  (the face that faces upwards in  FIG. 2 ) by a non-illustrated fastener. A frame member  58  that extends in the axial direction and is fixed to the apparatus body is also provided, with the fixing member  56  being fixed to the frame member  58  with a non-illustrated fastener. 
     An airflow path  60  is formed inside the casing  50 A of the collection device  50 , through which the collected mist flows. A portion of a wall plate forming the airflow path  60  is open such that a suction inlet  54  is provided extending along the axial direction to suck in mist of liquid droplets. Note that the position of the suction inlet  54  is determined such that the length from the suction inlet  54  to the liquid droplet ejection head  20 Y (shown as dimension E in  FIG. 6 ) is longer than the circumferential direction length of the opening of the recess portion  26 A (shown as dimension F in  FIG. 6 ). 
     In addition, eight suction fans  62  (see  FIG. 3 ) are provided in a row along the axial direction within the casing  50 A of the collection device  50  and serve as an example of suctioning members that impart suction force sucking mist in toward the suction inlet  54 . Plural circular discharge outlets  68  (see  FIG. 4 ) are provided at the rear (the left side in  FIG. 2 ) of the suction fans  62 . The discharge outlets  68  discharge air that has been sucked into the casing  50 A by the suction fans  62  externally (to the outside). 
     Further, there is a filter  64  provided so as to partition between the suction fan  62  installation space and the airflow path  60 . The filter  64  captures mist sucked in from the suction inlet  54  and passed through the airflow path  60 . 
     The shape of the airflow path  60  is determined such that mist sucked in from the suction inlet  54  by the suction force of the suction fans  62  spreads out in the airflow path  60 . 
     A plate-shaped guide member  52  is provided between the suction inlet  54  and the liquid droplet ejection head  20 Y to guide the mist of liquid droplets ejected from the liquid droplet ejection heads  20  towards the suction inlet  54 . The guide member  52  is fixed to the casing  50 A by non-illustrated fastener. 
     More precisely, the mist flows toward the downstream side in the rotation direction of the transport drum  26 , along the outer surface of the transport drum  26  rotating in the direction of arrow D. The guide member  52  is configured such that mist flowing toward the downstream side in the transport drum  26  rotation direction is guided into the suction inlet  54 . 
     In order to suppress leakage of mist outside the guide member  52  from between the liquid droplet ejection head  20 Y and the guide member  52 , a one end portion of the guide member  52  which is at the liquid droplet ejection head  20 Y side extends out to a position that is as close as possible to the liquid droplet ejection head  20 Y, while considering the movable range when attaching and detaching the liquid droplet ejection head  20 Y to and from the support stand  40 . 
     Furthermore, the guide member  52  is disposed such that the space between the guide member  52  and the outer surface of the transport drum  26  gets narrower when approaching the suction inlet  54 , and the other end portion of the guide member  52  contacts an opening edge  54 A at the upstream side of the suction inlet  54  in the transport drum  26  rotation direction. 
     More precisely, when viewed along the axial direction, if the closest point on the outer surface of the transport drum  26  to an opening edge  54 B which is at the downstream side of the suction inlet  54  in the transport drum  26  rotation direction is point A, then the guide member  52  is disposed such that a tangent B, contacting the outer surface of the transport drum  26  at the point A, and the guide member  52  are parallel. In the other wards, the distance (the closest (the shortest) distance) between the point A and the opening edge  54 B is narrower than the closest (the shortest) distance between the transport drum  26  and the opening edge  54 A. 
     At a portion of the casing  50 A configured by the opening edge  54 B which is at the downstream side of the suction inlet  54  in the transport drum  26  rotation direction, a projecting plate  66  is provided projecting out toward the rotation shaft  32  of the transport drum  26 , along the axial direction. The base end of the projecting plate  66  is fixed to the casing  50 A. 
     Furthermore, as shown in  FIG. 3  and  FIG. 4 , the both axial direction end portions of the projecting plate  66  and the both axial direction end portions of the guide member  52  are preferably bent around toward the transport drum  26 , so as to suppress mist from leaking toward the axial direction outsides from the projecting plate  66  and the guide member  52 . 
     Operation 
     First, explanation will be given regarding the flow of air occurring at the downstream side of the liquid droplet ejection head  20  in the transport drum  26  rotation direction.  FIG. 5  shows simulation results of air flow occurring between the liquid droplet ejection head  20 , the transport drum  26  and the collection device  50 , with the arrow direction representing the direction of flow of air, and the number of arrows representing the air flow rate. In other words, as the arrows become denser, the flow of air is greater with a faster airflow speed, in comparison to where the arrows are sparse (non-dense). 
     It can be seen from this simulation result that flow speed of the air flowing between the guide member  52  and the transport drum  26  gets faster further approaching the suction inlet  54 , since the space between the guide member  52  and the transport drum  26  gets narrower nearer to the suction inlet  54 . 
     Furthermore, it can be seen that air flowing between the guide member  52  and the transport drum  26  hits the projecting plate  66 , and is sucked into the suction inlet  54 . It can also be seen that the air which is at the transport drum  26  rotation direction downstream side of the projecting plate  66  passes through between the projecting plate  66  and the transport drum  26  by suction force generated at the suction inlet  54 , and is sucked into the suction inlet  54 . 
     Consequently, as shown in  FIG. 1 , the mist of liquid droplets ejected from the liquid droplet ejection heads  20  toward the sheet member P flows along the outer surface of the transport drum  26  rotating in the direction of arrow D, toward the transport drum  26  rotation direction downstream side. 
     The mist that has flowed to the transport drum  26  rotation direction downstream side is guided toward the suction inlet  54  by the guide member  52 . When this occurs, since the space between the guide member  52  and the transport drum  26  gets narrower closer to the suction inlet  54 , the flow speed of the mist gets faster closer to the suction inlet  54 . Since the flow speed of the mist gets faster closer to the suction inlet  54 , the mist more readily separates from the layer of air covering the outer surface of the transport drum  26 , in comparison to a case where the flow speed of the mist does not change. 
     A suction force is generated at the suction inlet  54  by driving the suction fans  62 . Due to the suction force generated at the suction inlet  54 , the mist guided by the guide member  52  and/or hitting the projecting plate  66  is sucked into the airflow path  60  from the suction inlet  54 . 
     As described above, the shape of the airflow path  60  is determined such that the mist sucked in from the suction inlet  54 , by the suction force of the suction fans  62 , spreads out in the airflow path  60 . Therefore, unevenness in the suction force of the suction inlet  54  extending along the axial direction is suppressed from occurring. Furthermore, by suppressing unevenness of suction force (air speed distribution) generated at the suction inlet  54  extending along the axial direction from occurring, unevenness of air flow rate passing through the filter  64  extending along the axial direction is also suppressed from occurring. 
     The mist sucked in toward the airflow path  60  is collected by the filter  64 , and air, from which the mist has been collected, passes through the suction fans  62  and is discharged from the discharge outlets  68 . 
     By providing the guide member  52  which guides the mist toward the suction inlet  54  in this manner, the mist of liquid droplets ejected from the liquid droplet ejection heads  20  and flowing toward the transport drum  26  downstream side, is collected. 
     Furthermore, by collecting the mist of liquid droplets flowing toward the transport drum  26  rotation direction downstream side, this suppress mist from floating around in the device and adhering to other components, or adhering to the sheet member P. 
     Furthermore, as stated above, the space between the guide member  52  and the transport drum  26  is narrower nearer to the suction inlet  54 . Therefore, the flow speed of the mist gets faster closer to the suction inlet  54 , and the mist is easily separated from the layer of air covering the outer surface of the transport drum  26 . 
     Furthermore, the projecting plate  66  is provided at the opening edge  54 B which is at the transport drum  26  rotation direction downstream side of the suction inlet  54 , the projecting plate  66  projects toward the rotation shaft  32  of the transport drum  26 . Consequently, mist flowing toward the transport drum  26  rotation direction downstream side hits the projecting plate  66 , and is sucked into the suction inlet  54 . 
     Furthermore, as can be seen from the simulation results, due to the suction force occurring at the suction inlet  54 , the air at the downstream side in the transport drum  26  with respect to the projecting plate  66  is sucked, passing through between the projecting plate  66  and the transport drum  26 , into the suction inlet  54 . Consequently, mist guided by the guide member  52  and flowing toward the transport drum  26  rotation direction downstream side is suppressed from leaking out to the transport drum  26  rotation direction downstream side from between the projecting plate  66  and the transport drum  26 . 
     The shape of the airflow path  60  is determined such that the mist sucked in from the suction inlet  54  by the suction force of the suction fans  62  spreads out in the airflow path  60 . Consequently, unevenness in suction force of the suction inlet  54  extending along the axial direction is suppressed from occurring. 
     Furthermore, by suppressing the occurrence of unevenness in the suction force of the suction inlet  54  extending along the axial direction, mist is sucked in from the suction inlet  54  uniformly across the axial direction. 
     Furthermore, by suppressing the occurrence of unevenness in the suction force of the axial direction extending suction inlet  54 , unevenness in the flow rate of air passing through the axial direction extending filter  64  is also suppressed from occurring. 
     Furthermore, by suppressing the occurrence of unevenness in air flow rate passing through the axial direction extending filter  64 , mist is adhered across the entire filter  64 , therefore prolonging the lifespan of the filter  64 . 
     The length from the suction inlet  54  to the liquid droplet ejection head  20 Y (dimension E shown in  FIG. 6 ) is longer than the opening length of the recess portion  24 A (dimension F shown in  FIG. 6 ). Consequently, mist floating inside the recess portion  26 A is suppressed from leaking out to the transport drum  26  rotation direction downstream side with respect to the projecting plate  66 . 
     Note that while a detailed explanation has been given of the present invention by way of exemplary embodiment, the present invention is not limited to the exemplary embodiment, and a person of ordinary skill in the art will be aware that various other embodiments are possible within the scope of the present invention. For example, in the exemplary embodiment above, the casing  50 A, the guide member  52 , and the projecting plate  66  are provided as separate members, however at least one of the guide member and the projecting plate may be integrated with the casing. That is, for example, the guide member  52  may be integrated with the casing  50 A such that the end portion of the guide member  52  at the downstream side in the rotation direction of the transport drum  26  configures the opening edge  54 A of the suction inlet  54  at the upstream side in the rotation direction of the transport drum  26 . 
     Furthermore, in the above exemplary embodiment, the surface of the guide member  52  is formed as a flat surface such that the space between the outer surface of the transport drum  26  and the guide member gets narrower closer to the suction inlet  54 , however, for example, the surface of the guide member may be a curved or stepped shape such that the space between the outer surface of the transport drum and the guide member gets narrower closer to the suction inlet.