JP5066503B2 - Duplex printing unit and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a duplex printing unit capable of printing a toner image on both sides of a sheet (copy paper, OHP plastic film, etc.), and an electrophotographic copying machine, printer, and facsimile equipped with the duplex printing unit. And the like.

  In an electrophotographic image forming apparatus having a duplex printing unit, a toner image is transferred to one side (first side) of a sheet in an image forming unit, and then the sheet is heated and pressurized by a fixing device to fix the toner image. The printed sheet is guided to the double-sided printing unit, and the double-sided printing unit is used to reverse the front and back of the sheet. A toner image is printed.

  In an image forming apparatus including such a duplex printing unit, a sheet heated by a fixing device is sent to an image forming unit, and the image forming unit is heated by heat stored in the sheet. As a result, the toner in the developing device constituting the image forming unit aggregates, causing unevenness and spots on the toner image formed on the photosensitive drum, resulting in a decrease in image quality, and a stirring paddle in the developing device. Problems such as increasing the sliding resistance of the rotating parts occur.

In order to solve such a problem, as shown in FIG. 7, after the heat of the sheet 101 sent from the fixing device 100 is transferred to the conveying roller pair 102, the conveying roller pair 102 is transferred to the fixing device 100. It is conceivable that the heat of the sheet 101 is effectively radiated by cooling with the fan 103 disposed on the downstream side of the sheet (see Patent Document 1).
Japanese Patent Laid-Open No. 7-18176

  However, according to the technique shown in FIG. 7, when the air flow 104 generated by the fan 103 hits the conveyance roller pair 102 and the sheet 101, the leading end of the sheet 101 cannot smoothly enter the nip 105 of the conveyance roller pair 102, There is a case where the sheet 101 is deformed so as to wave and enters the nip 105 of the pair of conveying rollers 102, and there is a possibility that the sheet 101 may be bent or wrinkled, or the sheet 101 may not be conveyed smoothly.

  SUMMARY An advantage of some aspects of the invention is that it provides a double-sided printing unit that can effectively dissipate heat from a sheet and does not cause deterioration in image quality or sheet conveyance, and an image forming apparatus including the same. .

  According to a first aspect of the present invention, in a double-sided printing unit that feeds a sheet on which a toner image is fixed to an image forming unit having a developing device by turning the sheet upside down, after receiving the sheet from the leading end side, the sheet is thereafter A double-sided printing tray that can be fed out from the end side; and a pair of conveying rollers that feeds the sheet into the double-sided printing tray and feeds the sheet out of the double-sided printing tray. . Then, one conveyance roller of the conveyance roller pair moves to a retreat position away from the other conveyance roller of the conveyance roller pair except during the conveyance of the sheet, and is cooled by a cooling unit at the retraction position. It is like that. Here, the cooling means includes a metal roller that is in rolling contact with the one transport roller that has moved to the retracted position, and a fan that blows air onto the metal roller. Further, the fan generates an air flow in a direction substantially parallel to the sheet on the duplex printing tray.

  According to a second aspect of the present invention, in the double-sided printing unit that reverses the front and back of the sheet on which the toner image is fixed and sends the sheet to an image forming unit equipped with a developing device, the sheet is received from the leading end side, and then the sheet is A double-sided printing tray that can be fed out from the end side; and a pair of conveying rollers that feeds the sheet into the double-sided printing tray and feeds the sheet out of the double-sided printing tray. . Then, one conveyance roller of the conveyance roller pair moves to a retreat position away from the other conveyance roller of the conveyance roller pair except during the conveyance of the sheet, and is cooled by a cooling unit at the retraction position. It is like that. Here, the cooling means is a fan that blows air to the one conveyance roller at the retracted position and takes heat away from the one conveyance roller. The fan generates an air flow in a direction substantially parallel to the sheet on the duplex printing tray.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, an air flow generated between the fan and the sheet on the double-sided printing tray is changed between the fan and the sheet on the double-sided printing tray. The air guide means for guiding in a substantially parallel direction is arranged.

  According to a fourth aspect of the present invention, there is provided a duplex printing unit according to any one of the first to third aspects, an image forming unit that forms a toner image on a sheet fed from the duplex printing unit, and a toner formed by the image forming unit. The present invention relates to an image forming apparatus comprising: a fixing device that heats and pressurizes a sheet on which an image is formed.

  According to the present invention, the heat of the sheet after the toner image is fixed is transferred to the pair of conveying rollers that convey the sheet. As a result, the temperature of the sheet printed on both sides is lowered, the developing device is hardly heated by the sheet during double-sided printing, and toner aggregation is less likely to occur. In addition, since toner aggregation is less likely to occur in the developing device, toner image unevenness and spots can be prevented, and image quality can be improved.

  Further, according to the present invention, one of the conveyance roller pairs is cooled at the retracted position, and the fan air flow as the cooling means is substantially parallel to the sheet on the duplex printing tray. The air flow is not blown onto the sheet, and sheet conveyance failure (such as sheet bending or wrinkles, oblique sheet feeding) due to the air flow of the fan being blown onto the sheet can be prevented.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
(Structure of image forming apparatus)
1 and 2 are schematic structural views of an electrophotographic image forming apparatus 1 according to the present embodiment. FIG. 1 is a schematic structural diagram of the entire image forming apparatus 1. FIG. 2 is a schematic structural diagram showing, on an enlarged scale, a portion A (a part of the duplex printing unit 2 and its vicinity) in FIG.

  As shown in these drawings, the image forming apparatus 1 includes a scanner unit 4 that reads an image of a document or the like and converts it into digital data on the upper part of the image forming apparatus main body 3. The scanner unit 4 reads an image of the document G that has been poured into the document reading position R by the automatic document feeder 5 or a document (not shown) or a reading object (book, magazine, painting, etc.) placed on the platen glass 6. ) Is converted into digital data and sent to a controller (CPU) 7 of the image forming apparatus 1. In addition to the image data sent from the scanner unit 4 to the controller 7, the image forming apparatus 1 according to the present embodiment has an external device (personal computer, other image forming apparatus, facsimile, mobile phone, A printing operation is executed on the basis of data transmitted from the scanner, digital camera, video camera, etc.) to the controller 7 and inputted.

  The image forming apparatus 1 includes a plurality of paper feeding devices 8 a to 8 d in the image forming apparatus main body 2. These sheet feeding devices 8a to 8d are each composed of a sheet feeding cassette 10a to 10d on which a plurality of sheets (not shown) (copy sheets, plastic films, etc.) can be stacked, and the uppermost sheet stored in the sheet feeding cassette 10a to 10d. A pickup roller that sequentially feeds the sheet to the sheet conveyance path 11 and a sheet feeding roller pair 13. Then, the sheets sent out from the sheet feeding devices 8 a to 8 d are conveyed by a plurality of conveyance roller pairs toward the image forming unit 14 in the sheet conveyance path 11. A registration roller pair 15 is disposed at a position immediately before the image forming unit 14 in the sheet conveyance path 11. The registration roller pair 15 corrects the skew of the sheet and sends the sheet to the transfer position P of the image forming unit 14. In addition, the image forming apparatus 1 manually feeds sheets or printing members (envelopes, label sheets, etc.) having a different size from the sheets accommodated in the plurality of sheet feeding apparatuses 8 a to 8 d toward the image forming unit 14. A paper device 8e is provided.

  The image forming unit 14 includes a cleaning device 17, a charge removal device 18, a charging device 20, a developing device 21, and a transfer device (transfer belt) 22 around the photosensitive drum 16. Are arranged in order along the rotation direction). The image forming unit 14 scrapes off the toner remaining on the surface of the photoconductive drum 16 with the cleaning device 17, and then neutralizes the surface of the photoconductive drum 16 with the charge eliminating device 18, and then the surface of the photoconductive drum 16 is removed. After being uniformly charged by the charging device 20, an electrostatic latent image is formed on the surface of the photosensitive drum 16 by the exposure device 23, and the developing device 21 is formed on the surface of the photosensitive drum 16 on which the electrostatic latent image is formed. After the toner is supplied from the photosensitive drum 16 and the electrostatic latent image on the photosensitive drum 16 is made visible as a toner image, the surface of the sheet (first surface) sent to the transfer position P between the photosensitive drum 16 and the transfer belt 22 is obtained. The toner image is transferred to the surface. The sheet on which the toner image is transferred is sent to the fixing device 24 by the transfer belt 22.

  The fixing device 24 includes a heating roller 25 and a pressure roller 26, and heats and presses the sheet at a nip portion between the heating roller 25 and the pressure roller 26, and transfers it to the surface (first surface) of the sheet. Fix the toner image. Here, the heating roller 25 is heated to a temperature (for example, 200 ° C.) at which the toner can be melted. As a result, the sheet fed from the fixing device 24 is in a heated state, and is heated to a high temperature.

  The sheet sent out from the fixing device 24 is guided to the discharge roller pair 28 by the flapper 27 when double-sided printing is not performed (only single-sided printing), and the discharge roller pair 28 externally (for example, punches holes). Or a post-processing apparatus (not shown) for performing stapling processing or a paper discharge tray 30).

  When performing double-sided printing, the sheet sent out from the fixing device 24 is guided to the double-sided printing guide path 31 by the flapper 27 and sent to the double-sided printing unit 2 by the conveying roller pair 32 arranged in the double-sided printing guide path 31. .

  The duplex printing unit 2 reverses the front and back sides of the sheet fed via the duplex printing guide path 31, feeds the sheet to the image forming unit 14, and prints the toner image on the unprinted surface (second surface) of the sheet. It is something that can be done. The duplex printing unit 2 connects a duplex printing tray 33 that receives and supports the sheet conveyed along the duplex printing guide path 31 from its leading end side, and the duplex printing tray 33 and the sheet conveyance path 11. The sheet return path 34 to be carried out, a transport roller pair 35 disposed at the end of the double-sided printing tray 33 on the double-sided printing guide path 31 side, and one of the transport roller pair 35 (upper side in FIG. 2). And a cooling means 38 that cools the (driven roller) 36 at a retracted position (a position indicated by a two-dot chain line in FIG. 2 that is sufficiently separated from the driving roller 37 that is the other conveying roller). Note that the driven roller 36 and the drive roller 37 are formed of rubber (for example, EPDM) at least on the surface side. In addition, a plurality of sheet conveyance rollers 40 to 43 are arranged in the sheet reflux path 34, and the sheet conveyance rollers 40 to 43 convey the sheet fed from the duplex printing tray 33 along the sheet reflux path 34. It conveys to the path 11.

  The conveyance roller pair 35 includes a driven roller 36 that is one conveyance roller located on the front surface side (upper side) of the sheet and a drive roller 37 that is the other conveyance roller located on the back surface side (lower side) of the sheet. Have. The driven roller 36 is supported by an arm 44 so as to be able to swing on the support frame 45, and the arm 44 is rotated by a motor 46 so that the sheet can be sandwiched between the driven roller 36 and the driving roller 37. It is possible to move between (the position indicated by the solid line in FIG. 2) and the retracted position sufficiently separated from the sheet (the position indicated by the two-dot chain line in FIG. 2: the position substantially parallel to the sheet stacking surface 33a of the duplex printing tray 33). It has become. Here, the driven roller 36 is separated from the driving roller 37 and moved to the retracted position except during sheet conveyance. The driven roller 36 rolls with the driving roller 37 or is rotated by a sheet conveyed by the driving roller 37 during sheet conveyance. On the other hand, the drive roller 37 is supported so as to be able to rotate to a predetermined position (position where it can come into contact with the back side of the sheet on the duplex printing tray 33), and is connected to a motor (M) 46 via a clutch (CL1) 47. The motor 46 can be rotated in both forward and reverse directions.

  Such a pair of conveying rollers 35 feeds the sheet conveyed through the double-sided printing guide path 31 from the leading end side onto the double-sided printing tray 33, and then sends the sheet fed onto the double-sided printing tray 33 thereafter. With the end side as the front end side (switched back), the sheet is fed from the duplex printing tray 33 to the sheet reflux path 34. Thereby, the front and back of the sheet are reversed. Since the support frame 45 is fixed to the image forming apparatus main body 3, the arm 44 is rotatably supported by the image forming apparatus main body 3 via the support frame 45.

  As shown in FIGS. 2 and 3, a pair of arms 44 are arranged apart from each other in the sheet width direction (direction perpendicular to the sheet conveying direction), and their base end portions 44 a rotate to the support frame 45. It is fixed to the pivot shaft 48 supported so as to be able to rotate integrally with the pivot shaft 48. A roller support shaft 50 is stretched around the tip 44b side of the pair of arms 44, and the driven roller 36 can freely rotate at the center in the direction in which the axis of the roller support shaft 50 extends. It is attached.

  The rotation shaft 48 of the arm 44 is connected to the motor 46 via a power transmission mechanism such as a gear train (not shown), a torque limiter (TL) 51, and a clutch (CL2) 52. A spring 53 that urges the driven roller 36 toward the drive roller 37 via the arm 44 is attached to the rotation shaft 48 of the arm 44. When the clutch 52 is disengaged, the rotation shaft 48 of the arm 44 holds the driven roller 36 at the transport position by the spring 53 and presses the driven roller 36 toward the driving roller 37 so that the driven roller 36 and the driving roller are pressed. A nip is formed between the two.

  As shown in FIGS. 2 and 4, the cooling unit 38 includes a metal roller 54 that contacts the driven roller 36 that has moved to the retracted position, and a fan 55 that blows air onto the metal roller 54. Among these, the metal roller 54 is formed on a support frame 45 in which at least an outer surface is formed of a metal having good heat conductivity (for example, aluminum, copper, iron, etc.), and a roller shaft 56 is fixed to the image forming apparatus main body 3. It is supported so that it can rotate. The metal roller 54 has a roller shaft 56 connected to the motor 46 via a power transmission mechanism such as a gear train (not shown), is rotated by the motor 46, and rotates to the driven roller 36 that has moved to the retracted position. While touching (rolling). At this time, if the driven roller 36 is hotter than the metal roller 54, the heat of the driven roller 36 is transferred to the metal roller 54 side. The fan 55 is an axial fan attached to the opening 57 of the support frame 5 fixed to the image forming apparatus main body 3, and the sheet (sheet stacking) in which the air stream 58 is stacked on the duplex tray 33. It is configured to be directed in a direction substantially parallel to the surface 33a), so that air can be directly blown onto the metal roller 54. Here, an air guide plate 60 is disposed immediately below the metal roller 54 and the fan 55 so as to divide the support frame 45 into two parts. The air guide plate 60 is attached to the support frame 45 and has a window 61 that allows the metal roller 54 and the driven roller 36 to contact each other, but there is no opening other than the window 61, The air flow 58 generated by the fan 55 is guided in a direction substantially parallel to the sheet stacking surface 33a of the duplex printing tray 33 (functions as an air guide means). Further, as shown in FIG. 4, the support frame 45 has an inverted U-shaped planar shape, and opens to the right in FIG. 2 and opens upward in FIG. 2. As a result, as shown in FIG. 2, the air flow 58 from the fan 55 does not flow out to the right of the support frame 45 and is not directly blown onto the sheet on the duplex printing tray 33.

  The cooling means 38 configured as described above can radiate the heat conducted from the driven roller 36 to the metal roller 54 to the atmosphere. Here, “the air flow 58 is directed in a direction substantially parallel to the sheets stacked on the duplex printing tray 33” means that the air flow 58 is directly blown onto the sheets on the duplex printing tray 33. As long as it is not, it means that the axis of the fan 55 is allowed to be arranged at a predetermined angle with respect to the sheets stacked on the duplex printing tray 33 (not arranged in parallel). The air inflow side (opening 57) of the fan 55 communicates with the outside of the image forming apparatus main body 3 through a duct (not shown), and the air flow 58 (from the metal roller 54) that has taken heat away from the metal roller 54. It is preferable that the air flow 58) to which the heat transfer is performed is discharged together with the ventilation air flow directed from the front side to the back side of the image forming apparatus main body 3 (in a direction orthogonal to the paper surface of FIG. 1). By doing so, the metal roller 54 can be efficiently cooled by outside air having a temperature lower than that in the image forming apparatus main body 3, and the temperature rise in the image forming apparatus main body 3 can be suppressed. The heat can be efficiently radiated.

  A sheet discharge path 62 that branches from the sheet reflux path 34 is disposed on the downstream side of the sheet transport roller 40 in the sheet transport direction. When the sheet discharge path 62 is connected to the sheet reflux path 34 by the flapper 63, the sheet that is turned upside down from the double-sided printing tray 33 and fed to the sheet reflux path 34 is fed into the sheet discharge path 28. To guide you to. Then, the sheets discharged out of the image forming apparatus main body 3 through the sheet discharge path 62 are stacked on the discharge tray 30 in a down face. In other words, the sheet discharge path 62 is used when a sheet printed on one side is discharged onto the sheet discharge tray 30 with the down face (first side down). The double-sided printed sheet is fed out from the fixing device 24 and then guided as it is to the discharge roller pair 28 by the flapper 27. The discharge roller pair 28 sets the sheet onto the discharge tray 30 with a down face (lower the first side). Discharged).

  In the present embodiment, the driven roller 36, the drive roller 37, and the metal roller 54 are formed with substantially the same outer diameter and substantially the same axial length.

(Operating state of duplex printing unit and cooling means)
Next, operating states of the duplex printing unit 2 and the cooling unit 38 will be described with reference to FIGS.

  First, when a predetermined time (t1) elapses after the carry-in side sheet detection sensor 64 disposed on the downstream side of the conveyance roller pair 32 of the double-sided printing guide path 31 detects the leading edge of the sheet, the controller 7 sends the motor 46 to the motor 46. When the operation start signal is output and the motor 46 rotates, the drive roller 37 rotates in the clockwise direction in FIG. 2, and the control signal is output from the controller 7 to the clutch 52, the clutch 52 is disengaged, and the arm 44. 2 is rotated in the clockwise direction in FIG. 2 by the urging force of the spring 53, and the driven roller (one transport roller) attached to the distal end portion 44b side of the arm 44 moves from the retracted position to the transport position, and duplex printing is performed. The sheet fed from the guide path 31 onto the duplex printing tray 33 is sandwiched between the driven roller 36 and the driving roller 37, and these driven rollers 6 and the driving roller 37 further feeds the sheet to the right in the duplex printing tray 33 of FIG. When the driven roller 36 is in contact with the sheet, the fixing heat accumulated on the sheet is conducted to the driven roller 36 side, and the temperature of the sheet is lowered. The predetermined time (t1) is the time (ta) from when the carry-in sheet detection sensor 64 detects the leading edge of the sheet until the trailing edge of the sheet is separated from the conveying roller pair 32 of the duplex printing guide path 31. ) (T1 <ta).

  When the sheet enters a predetermined dimension (slightly smaller than the minimum sheet length) into the duplex printing tray 33, the leading edge of the sheet is detected by the in-tray sheet detection sensor 65, and the detection signal is detected by the in-tray sheet detection sensor. 65 to the controller 7. When the in-tray sheet detection sensor 65 detects the leading edge of the sheet (in the case of a minimum size sheet), or when a predetermined time (t2) elapses after the in-tray sheet detection sensor 65 detects the leading edge of the sheet (minimum size). The clutch 47 is disengaged by the controller 7, the power transmission from the motor 46 to the drive roller 37 is cut off, the rotation of the drive roller 37 is stopped, and the drive roller 37 is driven. With the trailing edge of the sheet held between the rollers 36, the operation of carrying the sheet onto the duplex printing tray 33 is completed.

  Next, the clutch 52 is connected by the controller 7, the motor 46 is rotated in the reverse direction by the controller 7, and the rotation of the motor 46 is transmitted to the rotating shaft 48. As a result, the arm 44 is rotated by the motor 46 from the transport position to the retracted position (counterclockwise direction in FIG. 2) against the urging force of the spring 53 and is attached to the distal end portion 44 b side of the arm 44. The roller 36 is separated from the transport position, the nip between the driven roller 36 and the driving roller 37 is opened, the driven roller 36 moves to the retracted position, and the driven roller 36 contacts the metal roller 54. The driven roller 36 is pressed against the metal roller 54 rotated by the motor 46, and the driven roller 36 is driven by the metal roller 54 to rotate. When the rotational torque acting on the rotation shaft 48 exceeds a predetermined value, the torque limiter 51 slips and the driven roller 36 is held at the retracted position. While the driven roller 36 is held at the retracted position, the width adjustment guide (see FIG. 5) performs positioning and fine adjustment in the width direction of the sheet on the duplex printing tray 33 (direction orthogonal to the sheet conveying direction). (Not shown). Further, while the driven roller 36 is held at the retracted position, the heat of the driven roller 36 is conducted to the metal roller 54 that is cooled by the fan 55, and the temperature of the driven roller 36 decreases.

  When positioning in the width direction of the sheet is completed, the clutch 52 is disengaged by the controller 7, the power transmission from the motor 46 to the rotating shaft 48 is interrupted, and the arm 44 is urged by the spring 53 to rotate clockwise in FIG. The driven roller 36 is moved from the retracted position to the conveying position, the driven roller 36 is pressed toward the driving roller 37 by the elastic force of the spring 53, and the sheet is interposed between the driven roller 36 and the driving roller 37. It is pinched again.

  Next, the clutch 47 is connected by the controller 7, the motor 46 is rotated in the reverse direction by the controller 7, and the drive roller 37 is rotated in the reverse direction (counterclockwise direction in FIG. 2) by the motor 46. As a result, the sheet sandwiched between the driving roller 37 and the driven roller 36 is sent out by the driving roller 37 and the driven roller 36 toward the sheet reflux path 34 with the rear end side as the leading end side (switched back). During the sheet conveyance by the driving roller 37 and the driven roller 36, the heat of the sheet is conducted to the driven roller 36 side, and the temperature of the sheet further decreases.

  After a predetermined time (t3) has elapsed after the motor 46 is rotated in the reverse direction by the controller 7, when the leading end of the sheet is securely held between the sheet conveying rollers 40 and 41 of the sheet reflux path 34, the controller 7 The clutch 52 is connected, power is transmitted from the motor 46 to the rotating shaft 48, and the arm 44 rotates from the conveying position toward the retracted position against the biasing force of the spring 53, and the driven roller 36 and the driving roller 37 The nip between is opened. The driven roller 36 moves to the retracted position, the driven roller 36 is pressed against the metal roller 54 rotated by the motor 46, and the driven roller 36 rotates following the metal roller 54. When the rotational torque acting on the rotation shaft 48 exceeds a predetermined value, the torque limiter 51 slips and the driven roller 36 is held at the retracted position. While the driven roller 36 is held at the retracted position, the heat of the driven roller 36 is conducted to the metal roller 54 that is cooled by the fan 55, and the temperature of the driven roller 36 decreases.

  After the nip between the driven roller 36 and the driving roller 37 is released, the clutch 47 is disconnected by the controller 7, the power transmission from the motor 46 to the driving roller 37 is cut off, and the rotation of the driving roller 37 is stopped. . Thereafter, the sheet is conveyed through the sheet reflux path 34 by the sheet conveyance rollers 40 to 43 and the like, and is fed into the sheet conveyance path 11.

  The sheet conveyed into the duplex printing unit 2 is radiated to the image forming apparatus main body 3 side through the driving roller 37 in addition to being radiated through the driven roller 36, and the duplex printing tray 33 is disposed. Then, heat is radiated to the image forming apparatus main body 3 side and the temperature drops. Further, the sheet sent from the duplex printing tray 33 to the sheet reflux path 34 is in contact with the sheet conveyance rollers 40 to 43 and the like in the process of being conveyed through the sheet reflux path 34 and is cooled by air. The temperature drops.

(Effect of this embodiment)
According to the present embodiment configured as described above, the heat of the sheet printed on one side is transferred to the driven roller 36 that carries the sheet into and out of the double-sided printing tray 33, and the driven roller 36 has one sheet. Since the sheet is moved to the retracted position and cooled by the cooling means 38 every time the sheet loading / unloading operation is completed, the heat of each sheet fed to the duplex printing tray 33 can be reliably taken away by the driven roller 36, The temperature of each sheet fed onto the printing tray 33 can be reliably reduced.

  Therefore, according to the present embodiment, the developing device 21 is not overheated by the sheet supplied from the double-sided printing unit 2 to the image forming unit 14 side, and toner aggregation due to the heating of the developing device 21 is caused in advance. Therefore, it is possible to prevent deterioration in print image quality (occurrence of image unevenness and spots) due to toner aggregation, and high-quality printing can be performed.

  Further, according to the present embodiment, the driven roller (one transport roller) 36 of the transport roller pair 35 is cooled at the retracted position, and the air flow 58 of the fan 55 serving as the cooling means 38 is the double-sided printing tray 33. Since the air flow 58 of the fan 55 is not blown onto the sheet because the air flow 58 of the fan 55 is blown onto the sheet, the conveyance of the sheet is poor due to the air flow 58 of the fan 55 being blown onto the sheet. Occurrence, oblique feed, etc.).

  In this embodiment, even if the space between the double-sided printing tray 33 and the metal roller 54 can be sufficiently secured, even if the air flow 58 from the fan 55 collides with the metal roller 54 and the flow direction changes. The air guide plate 60 may be omitted as long as the air flow 58 is not sprayed on the sheet on the duplex printing tray 33.

  Further, according to the present embodiment, the air flow 58 generated by the fan 55 is directed in the direction (right direction in FIG. 2) in which the sheet is fed onto the duplex printing tray 33 from the duplex printing guide path 31 side. Therefore, the sheet is smoothly carried in from the guide path 31 for double-sided printing onto the tray 33 for double-sided printing.

  In addition, the numerical values, materials, and the like exemplified in the present embodiment are examples for easy understanding of the description, and are not limited thereto.

[Second Embodiment]
6 to 7 show a duplex printing unit 2 and an image forming apparatus 1 having the duplex printing unit 2 according to a second embodiment of the present invention. In addition, in the double-sided printing unit 2 and the image forming apparatus 1 including the same according to FIGS. 6 to 7, the components corresponding to the double-sided printing unit 2 of the first embodiment and the image forming apparatus 1 including the same are the same. A reference numeral is attached, and a duplicate description is omitted.

  As shown in FIGS. 6 and 7, in this embodiment, the metal roller 54 in the first embodiment is omitted, and a stopper 70 is disposed instead of the air guide plate 60 in the first embodiment. The stopper 70 is positioned so that the arm 44 is positioned at the retracted position when the arm 44 is abutted, and the driven roller 36 is positioned in front of the fan 55. Further, the stopper 70 guides the air flow 58 in the vicinity of the fan 55 so that the air flow 58 generated by the fan 55 is directed in a direction substantially parallel to the sheet stacking surface 33a of the duplex printing tray 33 (air guide). It also functions as a means). Then, the fan 55 as the cooling means 38 blows air (air flow 58) to the driven roller 36 held at the retracted position, and takes heat of the driven roller 36 by heat transfer from the driven roller 36 to the air flow 58. Then, the driven roller 36 is cooled.

  According to this embodiment, the same effects as those of the first embodiment can be obtained, the structure can be simplified, and the duplex printing unit 2 and the image forming apparatus 1 including the duplex printing unit 2 can be made inexpensive. Can do.

  In this embodiment, it is assumed that the distance between the driven roller 36 at the retracted position and the duplex printing tray 33 can be sufficiently secured, and the air flow 58 from the fan 55 collides with the driven roller 36 and the flow direction is changed. However, the stopper 70 is omitted as long as the air flow 58 is not blown onto the sheet on the duplex tray 33 and a stopper (not shown) for restricting the rotation of the arm 44 or the rotation shaft 48 can be installed. May be.

1 is a schematic structural diagram of an entire image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic structural diagram showing an enlarged view of part A (part of a double-sided printing unit and its vicinity) in FIG. It is sectional drawing which cut | disconnects and shows a support frame along the X1-X1 line | wire of FIG. FIG. 3 is a plan view showing the support frame shown in FIG. 2 as viewed from above in FIG. 2. FIG. 4 is a schematic structural diagram showing a part of a duplex printing unit according to a second embodiment of the present invention and the vicinity thereof in an enlarged manner, corresponding to FIG. 2. FIG. 6 is a plan view showing the support frame shown in FIG. 5 as viewed from above in FIG. 5. It is a figure which shows the cooling structure of the conventional fixed sheet | seat.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Duplex printing unit, 14 ... Image forming part, 21 ... Developing device, 24 ... Fixing device, 33 ... Duplex printing tray, 35 ... Conveying roller pair, 36 ... ... driven roller (one transport roller), 37 ... drive roller (other transport roller), 38 ... cooling means, 54 ... metal roller, 55 ... fan, 58 ... air flow, 60 ... air Guide plate (air guide means), 70 ...... Stopper (air guide means)

Claims (4)

In the double-sided printing unit that reverses the front and back of the sheet on which the toner image is fixed and sends it to the image forming unit equipped with the developing device
A double-sided printing tray adapted to be able to feed out the sheet from its rear end side after receiving the sheet from its front end side;
A feeding roller pair for feeding the sheet to the duplex printing tray and feeding the sheet from the duplex printing tray;
One conveying roller of the pair of conveying rollers moves to a retracted position away from the other conveying roller of the conveying roller pair except when the sheet is being conveyed, and is cooled by a cooling unit at the retracted position. And
The cooling means includes a metal roller that is in rolling contact with the one transport roller moved to the retracted position, and a fan that blows air onto the metal roller,
The fan generates an air flow in a direction substantially parallel to a sheet on the duplex printing tray;
A duplex printing unit characterized by that. In the double-sided printing unit that reverses the front and back of the sheet on which the toner image is fixed and sends it to the image forming unit equipped with the developing device
A double-sided printing tray adapted to be able to feed out the sheet from its rear end side after receiving the sheet from its front end side;
A feeding roller pair for feeding the sheet to the duplex printing tray and feeding the sheet from the duplex printing tray;
One conveying roller of the pair of conveying rollers moves to a retracted position away from the other conveying roller of the conveying roller pair except when the sheet is being conveyed, and is cooled by a cooling unit at the retracted position. And
The cooling means is a fan that blows air to the one conveyance roller at the retracted position and takes heat away from the one conveyance roller,
The fan generates an air flow in a direction substantially parallel to a sheet on the duplex printing tray;
A duplex printing unit characterized by that. Between the fan and the sheet on the duplex printing tray, air guide means for guiding the air flow generated by the fan in a direction substantially parallel to the sheet on the duplex printing tray is disposed,
The double-sided printing unit according to claim 1 or 2, wherein   A duplex printing unit according to any one of claims 1 to 3, an image forming unit that forms a toner image on a sheet fed from the duplex printing unit, and a sheet on which a toner image is formed by the image forming unit. An image forming apparatus comprising: a fixing device that heats and pressurizes.

Images