Patent Publication Number: US-10775721-B2

Title: Image forming apparatus

Description:
The entire disclosure of Japanese Patent Application No. 2018-081380, filed on Apr. 20, 2018, is incorporated herein by reference in its entirety. 
     BACKGROUND 
     Technological Field 
     The present invention relates to an image forming apparatus such as a copier, a laser beam printer, a facsimile machine, and a multi-functional peripheral thereof. 
     Description of the Related Art 
     An image forming apparatus applies heat to a toner image using a fixing device in order to fix the toner image onto a sheet of paper. A fixing roller provided inside the fixing device has a region over which a sheet of paper passes and to which heat is transferred, so that the temperature of this region lowers. This requires continuous application of heat while a sheet of paper is fed. As a result, the temperature tends to rise at each end of the fixing roller over which no sheet of paper passes. 
     Also, further acceleration of the speed of conveying a sheet of paper reveals problems that the stability for sheets of paper in a discharge unit of a secondary transfer roller is not kept, the heat in the fixing device rises to thereby increase the discharge amount of ultrafine particles (UFP), and the temperature inside the image forming apparatus rises. 
     Japanese Laid-Open Patent Publication No. 2006-349826 and Japanese Laid-Open Patent Publication No. 2016-51000 each disclose a technique for reducing the discharge amount of UFP by causing air to flow toward a fixing roller. Japanese Laid-Open Patent Publication No. 2013-190627 discloses a technique for configuring a fixing device to include a cooling fan for cooling a pressurizing roller. 
     SUMMARY 
     The above-described problems can be solved by providing an image forming apparatus with a fan for stabilizing the paper conveyance performance, a fan for cooling each end of a fixing roller, and a fan for collecting UFP. However, additional installments of fans lead to new problems that the image forming apparatus is increased in cost and size. 
     The present invention aims to solve the above-described problems and to provide an image forming apparatus configured such that air discharged from a fan for stabilizing the paper conveyance performance is used to cool each end of a fixing roller and then discharged through a filter, to thereby implement excellent paper conveyance performance, an appropriate interior temperature, cooling of each end of the fixing roller, and collection of UFP while suppressing increase in cost and size of the image forming apparatus. 
     To achieve at least one of the above-mentioned objects, according to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention comprises: a secondary transfer roller configured to transfer a toner image onto a sheet of paper; a fixing device provided downstream in a direction in which the sheet of paper is conveyed, the fixing device including a fixing roller that is configured to fix the toner image transferred onto the sheet of paper; a paper suction fan unit configured to suction air such that air flows over the secondary transfer roller; a guide member provided in the paper suction fan unit and configured to guide air discharged from the paper suction fan unit to be discharged toward the fixing roller; and a filter device through which air discharged from the guide member passes to be discharged. The guide member is configured to guide air in a direction crossing a rotation axis of the fixing roller at least toward each of ends of the fixing roller in a direction of the rotation axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention. 
         FIG. 1  is a schematic diagram showing the entire configuration of an image forming apparatus according to an embodiment. 
         FIG. 2  is a partial enlarged view of a region including a secondary transfer section according to an embodiment. 
         FIG. 3  is a perspective view showing the schematic configuration of a paper suction fan unit according to an embodiment. 
         FIG. 4  is a view seen from the direction indicated by an arrow line IV in  FIG. 2 . 
         FIG. 5  is a diagram showing the configuration of the paper suction fan unit and a filter device according to an embodiment. 
         FIG. 6  is a schematic diagram showing an opening adjustment mechanism according to an embodiment. 
         FIG. 7  is a diagram showing the first state of the opening adjustment mechanism according to an embodiment. 
         FIG. 8  is a diagram showing the second state of the opening adjustment mechanism according to an embodiment. 
         FIG. 9  is a diagram showing the third state of the opening adjustment mechanism according to an embodiment. 
         FIG. 10  is a diagram showing the first state of a path displacing device according to an embodiment. 
         FIG. 11  is a diagram showing the second state of the path displacing device according to an embodiment. 
         FIG. 12  is a perspective view showing the external appearance of an outside air intake port according to an embodiment. 
         FIG. 13  is a longitudinal cross-sectional view showing the configuration of the outside air intake port according to an embodiment. 
         FIG. 14  is a diagram showing the relation between an opening area of a filter duct of the filter device and an opening area of the outside air intake port on the filter duct side, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. 
     In the following, an image forming apparatus according to the present embodiment will be described with reference to the accompanying drawings. In the embodiments described below, when the number, the quantity and the like are mentioned, the scope of the present invention is not necessarily limited thereto unless otherwise specified. The same or corresponding components are designated by the same reference characters, and the description thereof may not be repeated. The drawings are not shown in accordance with the actual dimensional ratio, and there are some parts shown in different dimensional ratios for clearly illustrating the structure in order to allow easy understanding of the structure. 
     (Image Forming Apparatus  100 ) 
     Referring to  FIGS. 1 to 5 , the schematic configuration of an image forming apparatus  100  in the present embodiment will be described.  FIG. 1  is a schematic diagram showing the inner configuration of image forming apparatus  100 .  FIG. 2  is a partial enlarged view of a region including a secondary transfer section  30 .  FIG. 3  is a perspective view showing the schematic configuration of a paper suction fan unit  10 .  FIG. 4  is a diagram seen from the direction indicated by an arrow line IV in  FIG. 2 .  FIG. 5  is a diagram showing the configuration of paper suction fan unit  10  and a filter device  50 . 
     Referring to  FIG. 1 , image forming apparatus  100  mainly includes an apparatus main body  2  and a paper tray unit  9 . Apparatus main body  2  includes: an image forming unit  2 A serving to form an image on a sheet of paper S as a recording medium; and a paper feed unit  2 B serving to feed sheet of paper S to image forming unit  2 A. Paper tray unit  9  serves to store sheets of paper S to be fed to image forming unit  2 A and is removably provided in paper feed unit  2 B. 
     A plurality of rollers  3  are disposed inside image forming apparatus  100 , so that a conveyance path  4  along which sheet of paper S is conveyed in a prescribed direction is formed across image forming unit  2 A and paper feed unit  2 B mentioned above. As shown in  FIG. 1 , apparatus main body  2  may be provided separately with a manual feed tray  9   a  for feeding sheet of paper S to image forming unit  2 A. 
     Image forming unit  2 A mainly includes: an imaging unit  5  capable of forming a toner image of each of colors including, for example, yellow (Y), magenta (M), cyan (C), and black (K); an intermediate transfer belt  7   a  tensioned over each imaging unit  5 ; a secondary transfer section  30  provided on conveyance path  4  and on a path of intermediate transfer belt  7   a ; and a fixing device  20  provided on conveyance path  4  downstream from secondary transfer section  30  including secondary transfer roller  30   r.    
     Imaging unit  5  forms a toner image on the surface of a photoreceptor and transfers the formed toner image onto intermediate transfer belt  7   a  (that is, primary transfer). Thereby, a toner image as a color toner image or a monochrome toner image is formed on intermediate transfer belt  7   a.    
     Intermediate transfer belt  7   a  conveys the toner image formed on its surface to secondary transfer section  30 . Then, in secondary transfer section  30 , intermediate transfer belt  7   a  is pressed into contact with sheet of paper S conveyed from paper feed unit  2 B to secondary transfer section  30 . Thereby, the toner image formed on the surface of intermediate transfer belt  7   a  is transferred onto sheet of paper S (the so-called secondary transfer). 
     The toner image transferred onto sheet of paper S is fixed by a heating device  20   h  and a fixing roller  20   r  in fixing device  20 . Thereby, an image is formed on sheet of paper S. Then, sheet of paper S is discharged from apparatus main body  2 . 
     Image forming apparatus  100  further includes a detector  12  and a controller  13 . Detector  12  detects the size of sheet of paper S conveyed along conveyance path  4  from paper tray unit  9 . 
     Image forming apparatus  100  includes a conveyance guide  150 . Conveyance guide  150  is equipped with secondary transfer roller  30   r  rotatably about a rotation axis  30   a  (see  FIG. 4 ). Furthermore, conveyance guide  150  is equipped with paper suction fan unit  10 . 
     Referring to  FIGS. 2 to 4 , paper suction fan unit  10  includes two cross flow fans  11 . Cross flow fan  11  is disposed on each of both sides in a view seen in the axis direction of a rotation axis  20   a  of fixing roller  20   r  (see  FIG. 4 ). Cross flow fan  11  is located upstream from fixing device  20 . This cross flow fan  11  serves to suction air through an air suction port  150 W provided in conveyance guide  150  immediately downstream from secondary transfer roller  30   r  in order to separate sheet of paper S from secondary transfer roller  30   r  and to achieve the effect of stabilizing the posture of sheet of paper S. 
     Referring to  FIG. 4 , air suction port  150 W provided in conveyance guide  150  may be provided on the downstream side of secondary transfer roller  30   r . Furthermore, air suction port  150 W may be provided with an opening so as to include the center region of secondary transfer roller  30   r.    
     Furthermore, assuming that the distance between rotation axis  20   a  of fixing roller  20   r  and rotation axis  30   a  of secondary transfer roller  30   r  is defined as D 1 , the opening height (D 2 ) of air suction port  150 W may establish the relation of [D 1 / 2 ]&gt;D 2  (D 3 &gt;D 2 ). 
     Thereby, the separability of sheet of paper S from secondary transfer roller  30   r  can be assisted while the stability of conveyance performance of sheet of paper S can be improved. In the present embodiment, air suction port  150 W is formed in a horizontally-long rectangular shape as one hole, but a plurality of holes may be provided as air suction port  150 W. 
     Cross flow fan  11  suctions air from the center portion and blows air toward fixing roller  20   r  of fixing device  20 . Cross flow fan  11  includes a guide member  12 A. Guide member  12 A includes: a duct  12   d  configured to guide air toward fixing roller  20   r , and a plurality of fins  12   r  provided continuous to this duct  12   d  and configured to adjust the flow of air blown through duct  12   d  toward fixing roller  20   r.    
     The air discharged from cross flow fan  11  flows through duct  12   d  and fins  12   r , and then, is blown toward both ends of fixing roller  20   r  in the direction crossing the direction along rotation axis  20   a  of fixing roller  20   r  (upward in the figure). 
     Referring to  FIG. 5 , filter device  50  is provided above two cross flow fans  11  (on the downstream side in the air flow). Filter device  50  includes one filter duct  51  for covering fins  12   r  on both sides to gather air discharged from each cross flow fan  11  at one place. 
     Suction fans  52  for suctioning air upward (on the downstream side in the air flow) are provided at two positions inside filter duct  51 . Furthermore, a filter member  53  is provided above suction fans  52  (on the downstream side in the air flow). In the present embodiment, it is preferable that filter member  53  is provided with a filter for collecting UFP. 
     As described above, by employing filter duct  51  that gathers air discharged from each cross flow fan  11  at one place, it is sufficient to prepare only one filter member  53  irrespective of the number of cross flow fans  11 . 
     Suction fan  52  is configured to suction air discharged from cross flow fan  11  for paper suction so as to prevent the air from being discharged together with sheet of paper S to the paper discharge port after passing through fixing device  20 . 
     In this way, in image forming apparatus  100  according to the present embodiment, cross flow fan  11  attached to conveyance guide  150  provided with secondary transfer roller  30   r  is used to suction air through air suction port  150 W provided in conveyance guide  150  upstream from fixing device  20 , to discharge the air toward both axial ends of fixing roller  20   r  in the direction crossing the direction along rotation axis  20   a  of fixing roller  20   r , and then, further discharge the air through filter device  50 . 
     Thus, the air discharged from cross flow fan  11  for stabilizing the paper conveyance performance is used to cool each end of fixing roller  20   r , and then, discharged through filter device  50 , to thereby allow excellent paper conveyance performance, an appropriate interior temperature, cooling of each end of fixing roller  20   r , and collection of UFP while suppressing increase in cost and size of the image forming apparatus. 
     Although two cross flow fans  11  are provided in the above-described embodiment, one cross flow fan  11  may be used to cause air to blow toward both ends of fixing roller  20   r.    
     (Opening Adjustment Mechanism  40 ) 
     In the following, preferable embodiments will be described. Referring to  FIGS. 6 to 9 , an example of opening adjustment mechanism  40  at the air outlet port to fixing roller  20   r  will be described.  FIG. 6  is a schematic diagram showing opening adjustment mechanism  40 .  FIGS. 7 to 9  each are diagrams showing the first to third states of opening adjustment mechanism  40 . Opening adjustment mechanism  40  is controlled by controller  13  based on the size of sheet of paper S detected by detector  12 . 
     Referring to  FIG. 6 , opening adjustment mechanism  40  includes a stepping motor  44  having a pinion gear. Stepping motor  44  is provided with a pair of racks  43  to be screwed into the pinion gear. Each of racks  43  is provided with an opening and closing plate  43   a  so as to be capable of protruding toward the inside of duct  12   d . A pivot plate  41  is provided inside duct  12   d  so as to be pivotable upon contact with opening and closing plate  43   a . Pivot plate  41  has a shaft  41   d  and is biased by a pivot spring  45  so as to be kept standing upright. Since the opening adjustment mechanism  40  has the same configuration on its right and left sides, the configuration of opening adjustment mechanism  40  on the left side in the figure will be described below. 
     In the state shown in  FIG. 7 , opening and closing plate  43   a  is waiting at the position receding from the inside of duct  12   d , so that the inside of duct  12   d  is opened. As a result, the air discharged from cross flow fan  11  is entirely fed toward both ends of fixing roller  20   r . This state is employed when the size of sheet of paper S (the size of fixing roller  20   r  in the direction of rotation axis  20   a ) is relatively small, that is, when the area of each end of fixing roller  20   r  over which sheet of paper S does not pass is relatively large. 
     The state shown in  FIG. 8  shows the state where rotation of stepping motor  44  is controlled to cause opening and closing plate  43   a  to protrude to the position where opening and closing plate  43   a  comes into contact with pivot plate  41 . In this state, the inside area of duct  12   d  is closed by opening and closing plate  43   a , so that the air discharge from cross flow fan  11  is guided toward outside. This state is employed when the size of sheet of paper S is not largest but is greater than the size of sheet of paper S in the state shown in  FIG. 6 . 
       FIG. 9  shows the state where rotation of stepping motor  44  is controlled to cause opening and closing plate  43   a  to come into contact with pivot plate  41  and to cause opening and closing plate  43   a  to protrude to the position where opening and closing plate  43   a  presses pivot plate  41  so as to be inclined downward against the biasing force of pivot spring  45 . In this state, the inside area of duct  12   d  is closed by opening and closing plate  43   a  and pivot plate  41 , so that the air discharged from cross flow fan  11  is not fed to the fixing roller  20   r  side. This state is employed when the size of sheet of paper S is largest. 
     In this way, control can be performed: so as to increase the area of duct  12   d  through which air flows since the area of fixing roller  20   r  not in contact with the fed sheet of paper S is relatively large when sheet of paper S is relatively small; and so as to decrease the area of duct  12   d  through which air flows since the area of fixing roller  20   r  not in contact with the fed sheet of paper S is relatively small when sheet of paper S is relatively large. 
     (Path Displacing Device  120 ) 
     When the size of sheet of paper S is relatively large, the area of fixing roller  20   r  not in contact with the sheet of paper is relatively small. Thus, it is conceivable that the air discharged from cross flow fan  11  does not have to be fed into fixing roller  20   r . In such a case, path displacing device  120  may be provided above cross flow fan  11  as shown in  FIG. 2 . 
       FIGS. 10 and 11  each show the schematic configuration of path displacing device  120 .  FIGS. 10 and 11  are diagrams showing the first state and the second state of path displacing device  120 . Path displacing device  120  is provided upstream from fixing roller  20   r  and includes a path displacing plate  121  and a stepping motor  122 . By a rack and pinion mechanism provided between path displacing plate  121  and stepping motor  122 , path displacing plate  121  is allowed to protrude so as to be located above cross flow fan  11 . 
     In the state shown in  FIG. 10 , path displacing plate  121  is located at the receded position. Thus, all air discharged from cross flow fan  11  flows through a path A 11  leading to fixing roller  20   r . In the state shown in  FIG. 11 , stepping motor  122  controls the position of path displacing plate  121  such that path displacing plate  121  is moved so as to protrude toward cross flow fan  11 . The air discharged from cross flow fan  11  is blocked by path displacing plate  121  and moved away from fixing roller  20   r , so that the air is to flow through a path A 12  displaced from fixing roller  20   r.    
     In this way, the flow path of the air discharged from cross flow fan  11  is displaced by path displacing device  120  in accordance with the size of sheet of paper S. Thus, when the size of sheet of paper S is relatively large, cooling of fixing roller  20   r  leads to wasteful consumption of electric power. Accordingly, air is caused to flow in a protruding manner along path A 12  through which air is not brought into contact with fixing roller  20   r.    
     When the size of sheet of paper S is relatively small, air is caused to flow in a protruding manner through path A 11  in the direction crossing fixing roller  20   r  in order to cool each end of fixing roller  20   r . Furthermore, the smaller the size of sheet of paper S is, the more the area of duct  12   d  through which air flows may be increased, thereby increasing the range in which each end of fixing roller  20   r  is cooled, as described above. 
     (Outside Air Intake Duct  80 ) 
     Referring to  FIGS. 1, 2, 12, and 14 , an outside air intake duct  80  will be hereinafter described.  FIG. 12  is a perspective view showing the external appearance of outside air intake duct  80 .  FIG. 13  is a longitudinal cross-sectional view showing the configuration of outside air intake duct  80 .  FIG. 14  is a diagram showing the relation between an opening area A 1  of filter duct  51  in filter device  50  and an opening area A 2  of outside air intake duct  80  on the filter duct  51  side. 
     Image forming apparatus  100  has a housing  101  provided with outside air intake duct  80 . Outside air intake duct  80  includes: an inner duct  81  in communication with filter duct  51  of filter device  50 ; and a plurality of louvers  80   r  extending in the width direction of image forming apparatus  100 . Louvers  80   r  serve to adjust the wind direction and prevent mixture of foreign substances from outside. 
     Inner duct  81  is provided so as to extend from outside air intake duct  80  to filter duct  51 . The air taken in from the outside through outside air intake duct  80  is fed through inner duct  81  into filter duct  51 . It is preferable that inner duct  81  is coupled to filter duct  51  at the position upstream from suction fan  52 . 
     Inner duct  81  is formed to have an upper wall and a lower wall such that the distance between the upper wall and the lower wall narrows from outside toward inside. By employing the above-mentioned gradually narrowing shape, the effect of gradually accelerating the flow velocity of the air taken in from outside can be achieved. 
     Referring to  FIG. 13 , a center line CL 1  of outside air intake duct  80  that is formed by connecting the midpoints between the upper wall and the lower wall of outside air intake duct  80  may cross, at an acute angle (β 1 ), a line VL along which filter duct  51  extends. This configuration can prevent air containing UFP existing inside filter duct  51  from being discharged to the outside. 
     Referring to  FIG. 14 , opening area A 1  of filter duct  51  of filter device  50  (W 11 ×W 12 ) and opening area A 2  of outside air intake duct  80  on the filter duct  51  side (W 21 ×W 22 ) may establish the relation of A 1 &gt;A 2 . By establishing this area relation, the inside of filter duct  51  is more negative in pressure than the inside of inner duct  81 . Thus, the air containing UFP existing inside filter duct  51  can be further prevented from being discharged to the outside. 
     Furthermore, the air volume of each of cross flow fan  11  and suction fan  52  (which will be hereinafter collectively referred to as a fan) can be adjusted in accordance with the paper type (basis weight) of sheet of paper S. The air volume of the fan may be controlled to be smaller for thinner sheet of paper S than for thicker sheet of paper S. The fan is not only rotated when sheet of paper S is fed, but also may be started to be rotated while no sheet of paper S is fed in a time period between the previous sheet of paper S and the subsequent sheet of paper S during continuous printing, or may be started to be rotated at the time when heat is started to be applied to fixing device  20 . 
     The discharge amount of UFP can be suppressed by rotating the fan also when no sheet of paper S is fed. 
     An image forming apparatus includes: a secondary transfer roller configured to transfer a toner image onto a sheet of paper; a fixing device provided downstream in a direction in which the sheet of paper is conveyed, the fixing device including a fixing roller that is configured to fix the toner image transferred onto the sheet of paper; a paper suction fan unit configured to suction air such that air flows over the secondary transfer roller; a guide member provided in the paper suction fan unit and configured to guide air discharged from the paper suction fan unit to be discharged toward the fixing roller; and a filter device through which air discharged from the guide member passes to be discharged. The guide member is configured to guide air in a direction crossing a rotation axis of the fixing roller at least toward each of ends of the fixing roller in a direction of the rotation axis. 
     In another embodiment, a path displacing device is further included that is provided upstream from the fixing roller, the path displacing device being configured to displace a path of air discharged from the paper suction fan unit in accordance with a size of the sheet of paper. 
     In another embodiment, when the size of the sheet of paper is relatively large, an air path on an upstream side of the fixing device is displaced by the path displacing device from a position of the fixing roller. 
     In another embodiment, the filter device includes: a filter duct configured to gather air discharged from the guide member at one place; and a filter member through which air gathered by the filter duct passes. 
     In another embodiment, the filter member serves as a filter configured to collect UFP. 
     In another embodiment, the filter duct is in communication with an outside air intake duct through which outside air is taken in. 
     In another embodiment, a center line of the outside air intake duct crosses, at an acute angle, a line along which the filter duct extends. 
     In another embodiment, the outside air intake duct is formed to narrow toward the filter duct. 
     In another embodiment, a conveyance guide provided with the secondary transfer roller is included. The conveyance guide is provided with an air suction port through which air is caused to flow toward the secondary transfer roller. The air suction port is provided downstream from the secondary transfer roller. 
     In another embodiment, the air suction port is provided so as to include a center region of the secondary transfer roller. 
     In another embodiment, the paper suction fan unit includes a fan and is configured to change an air volume of the fan in accordance with a type of the sheet of paper. 
     In another embodiment, the fan is rotated even when the sheet of paper is not fed. 
     According to the above-described image forming apparatus, it becomes possible to provide an image forming apparatus configured such that air discharged from a fan for stabilizing the paper conveyance performance is used to cool each end of a fixing roller and then discharged through a filter, to thereby implement excellent paper conveyance performance, an appropriate interior temperature, cooling of each end of the fixing roller, and collection of UFP while suppressing increase in cost and size of the image forming apparatus. 
     Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.