Patent Publication Number: US-9405273-B2

Title: Image forming apparatus

Description:
INCORPORATION BY REFERENCE 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2014-191084, filed on Sep. 19, 2014. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The present disclosure relates to an image forming apparatus including a fixing device. 
     A fixing device included in an electrographic image forming apparatus generally fixes a toner image to paper by melting the toner through application of heat and pressure to the paper. To do so, the fixing device includes a heat source such as a heater. When a conveyance path and a paper ejection section around the fixing device reach a high temperature due to radiant heat from the fixing device, toner fusing may be adversely affected. 
     In a situation in which paper is moist, vapor is generated from the paper heated by the fixing device and condenses in the conveyance path located downstream of the fixing device in a paper conveyance direction. As a result, succeeding paper may become wet due to the condensation and may become wrinkled as a result. In duplex printing, toner may not be transferred to a wet part of the paper re-conveyed to a transfer section, resulting in creation of an image void. 
     In view of the foregoing, a certain image forming apparatus includes a fan above the paper conveyance path that extends from the fixing section to the paper ejection section. Further, a duct is also provided that allows air to flow from the fixing section to the fan via the paper conveyance path and air to flow from a paper exit port to the fan via the paper conveyance path. In the above configuration, water vapor generated in fixing can be removed, thereby preventing paper from being wet by water drops condensed around the paper conveyance path. 
     Meanwhile, if paper having a high moisture content is heated by the fixing device, vapor may be generated as steam. When the steam is released outside the image forming apparatus, a user may mistake the steam for smoke. In view of the foregoing, a certain image forming apparatus has a configuration in which cool air is blown at a side of paper ejected from the paper ejecting section to cool the obverse and reverse surfaces of the paper. Thus, a situation in which steam is generated from ejected paper can be avoided. 
     SUMMARY 
     An image forming apparatus according to the present disclosure includes an image forming section, a fixing device, a sheet conveyance path, a conveyance unit, a first cooling fan, a second cooling fan, and a conveyance guide member. The image forming section is configured to form a toner image on a sheet. The fixing device is disposed downstream of the image forming section in a sheet conveyance direction and configured to apply heat and pressure to the sheet to fix the toner image as unfixed yet to the sheet. The sheet conveyance path has first and second conveyance surface portions and guides the sheet to a sheet exit port after the sheet passes through the fixing device. The conveyance unit constitutes the first sheet conveyance surface portion and has an air introducing hole in communication with the sheet conveyance path. The first cooling fan is disposed within the conveyance unit and configured to suck air through the air introducing hole. The second cooling fan is disposed on an opposite side of the sheet conveyance path to the conveyance unit and configured to blow at the sheet passing air sucked from the sheet conveyance path. The conveyance guide member is fitted to the conveyance unit and configured to switch a conveyance direction of the sheet passing through the sheet conveyance path. The first cooling fan blows at the conveyance guide member air sucked from the air introducing hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cross sectional view illustrating an internal configuration of an image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 2  is an outer perspective view of the image forming apparatus as viewed from the back according to an embodiment of the present disclosure. 
         FIG. 3  is a partial cross sectional view illustrating a section around a rear cover unit in the image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 4  is a side cross sectional view illustrating a state in which the rear cover unit is open in the image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 5  is an outer perspective view illustrating a state in which the rear cover unit is removed in the image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 6  is a partially enlarged view illustrating a section around an exhaustion port in the image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 7  is a perspective view of the rear cover unit of the image forming apparatus as viewed from inside according to an embodiment of the present disclosure. 
         FIG. 8  is a perspective view illustrating a state in which a conveyance guide is removed from the rear cover unit of the image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 9  is a perspective view illustrating a first cooling fan disposed within the rear cover unit of the image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 10  is a side cross sectional view illustrating a section in the vicinity of the rear cover unit of image forming apparatus during simplex printing according to an embodiment of the present disclosure. 
         FIG. 11  is a side cross sectional view illustrating a section in the vicinity of the rear cover unit of the image forming apparatus during duplex printing according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present disclosure will be described with reference to the accompanying drawings. 
     As illustrated in  FIGS. 1-4 , an image forming apparatus (e.g., a monochrome printer)  100  includes in the interior thereof, an image forming section P and a fixing device  15 . The image forming section P forms a monochrome image through processes including charging, exposure, development, and transfer. A photosensitive drum  5  is disposed in the image forming section P. A charging unit  4 , an exposure unit (e.g., a laser scanning unit)  7 , a developing unit  8 , a transfer roller  14 , a cleaning device  19 , and a static eliminator (not illustrated) are disposed around the photosensitive drum  5  in a rotation direction (counterclockwise direction in  FIG. 1 ). 
     In image formation, the charging unit  4  uniformly charges the photosensitive drum  5  as the photosensitive drum  5  rotates counterclockwise. The exposure unit  7  irradiates the photosensitive drum  5  with a laser beam based on image data to form an electrostatic latent image on the photosensitive drum  5 . The developing unit  8  attaches toner to the electrostatic latent image to form a toner image. The toner is an example of a developer. 
     The toner container  9  supplies toner to the developing unit  8 . Note that the image data may be transmitted from a personal computer (not illustrated), for example. The static eliminator (not illustrated) for removing residual charge on the surface of the photosensitive drum  5  is located downstream of the cleaning device  19 . 
     Paper (a sheet of paper) is conveyed from a paper feed cassette  10  or a manual paper feeder  11  toward the photosensitive drum  5  on which the toner image is formed via a paper conveyance path  12  and a registration roller pair  13 . The transfer roller  14  (an image transfer section) transfers the toner image formed on the surface of the photosensitive drum  5  to the paper. In this manner, the image forming section P forms the toner image on the paper. The paper to which the toner image is transferred is separated from the photosensitive drum  5  and conveyed to the fixing device  15 . 
     The fixing device  15  is located downstream of the image forming section P in a paper conveyance direction (a sheet conveyance direction). The fixing device  15  applies heat and pressure to the paper to fix the toner image as unfixed yet on the paper. 
     A diverging guide  22  (a conveyance guide member) is disposed at a curved portion  20  of a paper conveyance path  16  (sheet conveyance path). The diverging guide  22  guides the paper to the paper conveyance path  16  once the paper has passed through the fixing device  15 . A second paper ejection port  31  in communication with the curved portion  20  is located in a rear surface (a right surface in  FIG. 1 ) of the image forming apparatus  100 . The diverging guide  22  determines an ejection destination of the paper to which the toner image is fixed by the fixing device  15  as either a first paper ejection port (a sheet exit port)  30  or the second paper ejection port (a sheet exit port)  31 . In short, the diverging guide  22  switches the conveyance direction of the paper passing through the paper conveyance path  16 . The diverging guide  22  further guides paper to a reverse conveyance path  21  when the paper is conveyed in the reverse direction through the paper conveyance path  16  during duplex printing. 
     Once the paper has passed through the fixing device  15  and a conveyance roller pair  23 , the paper is conveyed onto the top of the image forming apparatus  100  through the paper conveyance path  16 . In image formation on a single side of the paper (simplex printing), the paper is ejected onto an exit tray  18  from the first paper ejection port  30  via a conveyance roller pair  24  and a first ejection roller pair  17   a . Alternatively, the paper is ejected from the second paper ejection port  31  via a second ejection roller pair  17   b.    
     By contrast, in image formation on both sides of the paper (duplex printing), the conveyance roller pair  24  and the first ejection roller pair  17   a  are rotated in the reverse direction to reverse the paper conveyance direction after a tailing edge of the paper passes through the curved portion  20  of the paper conveyance path  16 . As a result, the paper is distributed to a reverse conveyance path  21  diverging from the curved portion  20  and re-conveyed to the registration roller pair  13  in a state in which a side of the paper that has received the image is reversed. A toner image formed next on the photosensitive drum  5  is transferred by the transfer roller  14  to a side of the paper on which no image is formed. The paper to which the toner images are transferred is conveyed to the fixing device  15 , subjected to fixing of the toner images, and then ejected onto the exit tray  18  from the first paper ejection port  30  via the conveyance roller pair  24  and the first ejection roller pair  17   a . Alternatively, the paper is ejected from the second paper ejection port  31  via the second ejection roller pair  17   b . That is, the paper conveyance path  16  guides the paper to the first or second paper ejection port  30  or  31  once the paper has passed through the fixing device  15 . Note that the paper is reversed from the first side to the second side in the reverse conveyance path  21  and conveyed to the image forming section P, as described above. The second side of the paper is opposite to the first side thereof. 
     The image forming apparatus  100  includes a rear cover unit  40  (a conveyance unit). The rear cover unit  40  pivots about a pivot fulcrum  40   a  at the lower end part of the rear cover unit  40  and is openable and closable relative to the main body of the image forming apparatus  100 . That is, the rear cover unit  40  is supported in an openable and closable manner on the rear surface of the main body of the image forming apparatus  100 . The diverging guide  22 , one roller  24   a  of the conveyance roller pair  24 , one roller  25   a  of a conveyance roller pair  25 , and the second ejection roller pair  17   b  are supported on the rear cover unit  40 . The rear cover unit  40  constitutes a paper conveyance surface portion  16   a  (a sheet conveyance surface portion, a first sheet conveyance surface portion) at one side (outer side) of the paper conveyance path  16 . 
     As illustrated in  FIGS. 4 and 5 , when the rear cover unit  40  is opened, the paper conveyance path  16  is disassembled. Disassembly of the paper conveyance path  16  can enable removal of a jam (paper jam) in the paper conveyance path  16 . Further, first cooling fans  50   a  and  50   b  are disposed within the rear cover unit  40 . In addition, a second cooling fan  51  is disposed on the opposite side of the paper conveyance path  16  to the rear cover unit  40 . 
     Moreover, a control section  90  is disposed in the interior of the image forming apparatus  100  to control respective operations of various elements including the image forming section P, the fixing device  15 , the first cooling fans  50   a  and  50   b , and the second cooling fan  51 . The control section  90  may include a central processing unit (CPU), for example. 
     As illustrated in  FIGS. 5 and 6 , one roller  24   b  of the conveyance roller pair  24  and one roller  25   b  of the conveyance roller pair  25  are supported on another paper conveyance surface portion (a sheet conveyance surface portion, a second sheet conveyance surface portion) of the paper conveyance path  16 . An exhaust port  45  is located in the paper conveyance surface portion  16   b . The second cooling fan  51  (see  FIG. 1 ) that blows air from the exhaust port  45  is disposed inside the paper conveyance surface portion  16   b.    
     As illustrated in  FIG. 7 , the roller  24   a  of the conveyance roller pair  24  is supported at the upper end part of the paper conveyance surface portion  16   a  constituted by the rear cover unit  40 . A conveyance guide  41  is fitted over a central part to a lower end part of the paper conveyance surface portion  16   a . The diverging guide  22  is swingably supported so as to overlap with an upper end part of the conveyance guide  41 . 
     The roller  25   a  of the conveyance roller pair  25  is supported on the conveyance guide  41 . Slit-like air introducing holes  41   a  are located in the conveyance guide  41  at each of two locations in a width direction (right and left directions in  FIG. 7 ) perpendicular to the paper conveyance direction. The air introducing holes  41   a  are in communication with the paper conveyance path  16 . 
     As illustrated in  FIG. 8 , the first cooling fans  50   a  and  50   b  are disposed inside the conveyance guide  41  so as to be opposite to the left and right air introducing holes  41   a , respectively. 
     As illustrated in  FIG. 9 , the first cooling fan  50   a  is a sirocco fan. Specifically, the first cooling fan  50   a  rotates a plurality of blades (not illustrated) extending in a radial direction of the first cooling fan  50   a  to suck air from a sucking port  52  at a central part of the first cooling fan  50   a  and blow the air sucked from a blowing port  53  at an outer circumferential part of the first cooling fan  50   a.    
     The first cooling fan  50   b  is a sirocco fan having the same configuration as the first cooling fan  50   a . As illustrated in  FIGS. 3 and 8 , the first cooling fans  50   a  and  50   b  are disposed so as to blow air through the respective blowing ports  53  in a direction in which the paper conveyance path  16  extends. Note that the paper conveyance path  16  extends upward (e.g., vertically upward) from a portion downstream of the fixing device  15  in the paper conveyance direction. 
     For example, the first cooling fans  50   a  and  50   b  are disposed asymmetrically in the rear cover unit  40  such that the respective blowing ports  53  face obliquely upward (in directions indicated by hatched arrows in  FIG. 8 ). Specifically, the first cooling fans  50   a  and  50   b  are disposed such that air flowing from the blowing port  53  of the first cooling fan  50   a  intersects with air flowing from the blowing port  53  of the first cooling fan  50   b  at a central part CP of the paper conveyance path  16  in a paper width direction WD. In the above configuration, when the blades of the first cooling fans  50   a  and  50   b  rotate, the air sucked from the air introducing holes  41   a  of the conveyance guide  41  is blown toward the reverse surface of the diverging guide  22 . That is, the first cooling fans  50   a  and  50   b  blow air sucked through the air introducing holes  41   a  at the diverging guide  22 . 
     Note that the configurations of the first cooling fan  50   b  and the second cooling fan  51  are the same as that of the first cooling fan  50   a  illustrated in  FIG. 9 . Therefore, description thereof is omitted. The paper width direction WD is perpendicular to the paper conveyance direction. 
     As illustrated in  FIG. 10 , paper S to which a toner image is fixed in the fixing device  15  is conveyed upward to the paper conveyance path  16  via the curved portion  20 . The paper S is heated when passing through a fixing roller pair of the fixing device  15 . In a situation in which the paper S is moist, vapor may be accordingly generated from the heated paper S. 
     In the present embodiment, the first cooling fans  50   a  and  50   b  suck hot air and vapor released from the paper S through the air introducing holes  41   a  in the conveyance guide  41 . The heat and vapor are then exhausted toward the reverse surface of the diverging guide  22 . On the other hand, the second cooling fan  51  (see  FIG. 3 ) blows air through the exhaust port  45  (see  FIG. 6 ) in the paper conveyance surface portion  16   b  at the paper S passing through the paper conveyance path  16 . In the above configuration, vapor released from the paper S is sucked by the first cooling fans  50   a  and  50   b  and dispersed by the second cooling fan  51 . As a result, a situation in which the vapor is steamed and a user mistakes the steam for smoke can be avoided. 
     The first cooling fans  50   a  and  50   b  suck air heated by the paper S and discharge the hot air toward the reverse surface of the diverging guide  22 . The diverging guide  22  is accordingly heated. As a result, a situation in which the vapor condenses into water drops on the diverging guide  22  and the paper conveyance path  16  to generate water drops can be avoided. 
     Moreover, air suction by the first cooling fans  50   a  and  50   b  through the air introducing holes  41   a  of the conveyance guide  41  allows conveyance of the paper S in a state in which the paper S is drawn toward the side of the conveyance guide  41  of the rear cover unit  40  (a side of the paper conveyance surface portion  16   a ). In the above configuration, the paper S can be conveyed stably in a state in which an opposite side (a second side) of the paper S to a print side S 1  (a first side) of the paper S is close to the paper conveyance surface portion  16   a . In other words, the paper conveyance surface portion  16   a  guides the opposite side to the print side S 1  of the paper S. The print side S 1  is a side of the paper S that is subjected to printing in simplex printing or that is subjected to printing first in duplex printing. The print side S 1  of the paper S can be prevented from being abraded on the paper conveyance surface portion  16   b  constituting a part on the inner side (left side in  FIG. 10 ) of the paper conveyance path  16 . Accordingly, the print side S 1  can be protected. Also, toner can be prevented from being attached to an inner corner surface  20   a  of the curved portion  20  that faces the rear cover unit  40 . The inner corner surface  20   a  constitutes the paper conveyance surface portion  16   b  located at an inner corner of the curved portion  20  of the paper conveyance path  16 . Note that the air introducing holes  41   a  are located opposite to the inner corner surface  20   a.    
     As illustrated in  FIG. 11 , the conveyance roller pair  24  and the first ejection roller pair  17   a  are rotated in the reverse direction to reverse the paper conveyance direction after a tailing edge of the paper S passes through the curved portion  20  of the paper conveyance path  16 . As a result, the paper S is distributed to a reverse conveyance path  21  diverging from the curved portion  20 . 
     At that time, in the same way as in simplex printing, the first cooling fans  50   a  and  50   b  suck air from the air introducing holes  41   a  in the conveyance guide  41  and the second cooling fan  51  (see  FIG. 3 ) blows exhaust air. In the above configuration, the paper S is conveyed while being drawn toward the conveyance guide  41  (the paper conveyance surface portion  16   a ) of the rear cover unit  40 . Accordingly, the paper S can be conveyed stably along the paper conveyance surface portion  16   a  constituting a part on the outer side (right side in  FIG. 10 ) of the reverse conveyance path  21 . Further, the print side S 1  (the first side) of the paper S can be prevented from being abraded on a reverse surface  21   b  of the reverse conveyance path  21  that constitutes an inner part (a left part in  FIG. 10 ) of the paper conveyance path  16 . Thus, the print side S 1  can be protected. Also, toner can be prevented from being attached to a reverse surface  21   a  of the reverse conveyance path  21 . 
     Here, in a situation in which the image forming apparatus  100  is used in a low temperature environment, for example, when the first cooling fans  50   a  and  50   b  or the second cooling fan  51  are/is operated in a state in which the inside of the image forming apparatus  100  is warmed insufficiently immediately after power-up or return from an energy saving (sleep) mode of the image forming apparatus  100 , cool air is blown into the paper conveyance path  16  and at the diverging guide  22 , which may induce condensation. 
     In view of the foregoing, after power-up or return from the energy saving mode of the image forming apparatus  100 , the control section  90  (see  FIG. 1 ) preferably suspends operations of the first cooling fans  50   a  and  50   b  and the second cooling fan  51  until paper that is printed first after the power-up or the return from the energy saving mode of the image forming apparatus  100  is ejected. In other words, the control section  90  preferably suspends the operations of the first cooling fans  50   a  and  50   b  and the second cooling fan  51  until paper printed first after power-up or return from the energy saving mode of the image forming apparatus  100  is ejected after the power-up or the return from the energy saving mode of the image forming apparatus  100 . Accordingly, a situation in which the first cooling fans  50   a  and  50   b  and the second cooling fan  51  are operated in a state in which the inside of the image forming apparatus  100  is not sufficiently heated can be avoided. As a result, condensation caused by blowing of cool air at the paper conveyance path  16  and the diverging guide  22  can be prevented. Note that although air suction by the first cooling fans  50   a  and  50   b  and air blowing by the second cooling fan  51  are not performed for paper to be first subjected to printing, the amount of vapor released from a single sheet of paper is not so much to invite user mistake for smoke. 
     Note that the control section  90  may suspend the operations of at least one of the first cooling fans  50   a  and  50   b  and the second cooling fan  51  until paper printed first after power-up or return from the energy saving mode of the image forming apparatus  100  is ejected after the power-up or the return from the energy saving mode of the image forming apparatus  100 . 
     As has been described so far, in the image forming apparatus  100  according to the present embodiment, condensation of vapor generated from paper around the fixing device  15  through fixing and release of the vapor outside the image forming apparatus  100  can be reduced effectively. 
     The present disclosure is not limited to the above embodiment. Various alterations can be made without departing from the gist of the present disclosure. For example, the first cooling fans  50   a  and  50   b  and the second cooling fan  51  are sirocco fans in the above embodiment. However, a propeller fan that sucks air in the rear cover unit  40  may be used instead of any of the sirocco fans. The same advantages as in the above embodiment can be obtained in this configuration. The respective locations and the respective numbers of first cooling fans  50   a  and  50   b  and second cooling fans  51  are not limited as above. Two or more second cooling fans  51  may be provided. One or three or more first cooling fans (the first cooling fans  50   a  and  50   b ) may be provided.