JP2006091705A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which suppresses the temperature rise of an inside thereof at the time of double-sided print by enhancing cooling efficiency for papers in a double-sided unit and is made high-density and compact. <P>SOLUTION: In an image forming apparatus 1, a pair of resist rollers 12, a transfer roller 13, and a fixing part 14 are disposed in a carrying unit 17. An opening 19a is provided above a double-sided unit 19, and an inverting tray 22 is exposed to the outside. A fan 30 for cooling a paper carried onto the inverting tray 22 is disposed so as to face the opening 18a of the double-sided unit 19. Thus the fan can sufficiently suck air to be blown to the paper to efficiently cool the paper heated by the fixing part 14, on the inverting tray 22. Since air is blown from above the paper, a stable carrying state is maintained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer provided with a duplex unit capable of duplex printing, and more particularly to a cooling mechanism for a sheet on which an image is formed on one side.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system such as a copying machine or a printer, after forming an image on one side of a sheet, the sheet is conveyed again to the image forming unit without being discharged, and also on the other side. A double-sided printing method for forming an image is widely used. In such a double-sided printing type image forming apparatus, as disclosed in Patent Document 1, a reversing unit that reverses a sheet on which an image is formed on one side, and a reconveying unit that reconveys the reversed sheet to the image forming unit. Equipped with a duplex unit with FIG. 7 shows a schematic configuration of an image forming apparatus equipped with a duplex unit.

  In FIG. 7, reference numeral 1 denotes an image forming apparatus. Here, a digital multi-function peripheral is shown as an example. In the image forming apparatus 1, when a copying operation is performed, in the image forming unit 2 in the multifunction machine main body, the photosensitive drum 4 that rotates in the direction A in the drawing is uniformly charged by the charging unit 3, and the image reading unit 5. An electrostatic latent image is formed on the photosensitive drum 4 by a laser beam from an exposure unit (laser scanning unit or the like) 8 based on the original image data read in step S1, and a developer (hereinafter referred to as developer) is formed on the electrostatic latent image by the developing unit 7. Toner) is attached to form a toner image. The toner is supplied to the developing unit 7 from the toner container 6.

  An image forming unit is configured such that a sheet is fed from the sheet feeding mechanism 9 to the photosensitive drum 4 on which the toner image is formed as described above via the sheet feeding roller 10, the sheet conveying path 11, and the registration roller pair (registration unit) 12. 2, the toner image formed on the surface of the photosensitive drum 4 by the transfer roller 13 (image transfer unit) in the image forming unit 2 is transferred onto a sheet. The sheet onto which the toner image has been transferred is separated from the photosensitive drum 4 and conveyed to a fixing unit 14 having a fixing roller pair 14a to fix the toner image. The toner (residual toner) remaining on the surface of the photosensitive drum 4 after the toner image is transferred to the sheet is removed by the cleaning device 21.

  The paper that has passed through the fixing unit 14 is distributed in the transport direction by a branching unit 15 that branches in a plurality of directions. When an image is formed on only one side of the sheet, it is discharged to the sheet discharge unit 16 as it is. The registration roller pair 12, the transfer roller 13, and the fixing unit 14 are disposed in the transport unit 17 in this order along the paper transport path 11.

  On the other hand, when images are formed on both sides of a sheet, the sheet that has passed through the fixing unit 14 is distributed to the sheet conveyance path 18 by the branching unit 15, reversed by the switchback roller 20 in the duplex unit 19, and It is re-conveyed to the image forming unit 2 with the surface not formed facing up. The re-conveyed paper forms the next image in the image forming unit 2, is conveyed to the fixing unit 14, fixes the toner image, and is then discharged from the paper discharge unit 16 to the outside of the apparatus.

  Although not shown, a static elimination device that removes residual charges on the surface of the photosensitive drum 4 is provided on the downstream side of the cleaning device 21. Further, the paper feed mechanism 9 is detachably attached to the image forming apparatus 1 and includes a plurality of paper feed cassettes 9a, 9b, 9c for storing paper, and a stack bypass (manual feed tray) 9d provided thereabove. These are connected to the image forming unit 2 including the photosensitive drum 4 and the developing unit 7 through the paper conveyance path 11.

  FIG. 8 is an enlarged view of the vicinity of the transport unit 17 and the duplex unit 19 in FIG. The operation of the duplex unit will be described in more detail with reference to FIG. When the user selects the duplex printing mode, the paper on which the toner image is formed on one side in the image forming unit 2 is transported to the fixing unit 14 and the toner image is fixed, and then to the paper transporting path 18 in the branching unit 15. Sorted and conveyed to the duplex unit 19. The conveyed paper is temporarily held on the reverse tray 22 by the switchback roller 20. At this time, the image surface is facing downward. The feed roller 20 and the reversing tray 22 constitute reversing means for reversing the orientation of the image surface by switching the paper transport direction.

  Next, the paper on the reverse tray 22 is conveyed to the lower part of the duplex unit 19 by rotating the switchback roller 20 in the reverse direction. Then, it passes through the re-conveying means comprising the driving roller 23, the conveying rollers 24a, 24b, 24c and the driven rollers 25a, 25b, 25c with the image surface facing upward, and the image surface faces downward from the registration roller pair 12. Re-conveyed to the image forming unit 2. A new toner image is formed on the upper surface on which no image is formed in the image forming unit 2, transported to the fixing unit 14 and fixed, and then distributed to the discharge roller 16 in the branching unit 15 to the outside of the apparatus. Discharged.

  Reference numeral 26 denotes a guide plate provided at a lower portion of the duplex unit 19 and is configured so that an upstream end portion thereof can be opened and closed with a rotation shaft 27 on the downstream side in the paper transport direction as a center. The guide plate 26 is provided with a driven roller 25a. When the guide plate 26 is opened to separate the driven roller 25a from the transport roller 24a, a jam such as a paper jam or a transport failure occurs in the duplex unit 19. In some cases, the jam processing can be easily performed. The duplex unit 19 is configured to be able to be taken in and out of the main body of the image forming apparatus 1 (see FIG. 7).

  In such an image forming apparatus, after the toner image on the first side is fixed by passing through the fixing unit 14, the sheet is transported again to the image forming unit 2 for image formation on the second side. The sheet is heated by the fixing unit 14. Therefore, when double-sided printing is continuously performed, the temperature of the image forming unit 2 increases due to the heat of the sheet, and the fluidity of the toner decreases. As a result, the toner adheres to the bearing portion or the like in the developing unit 7 and the circulation of the toner becomes insufficient, so that the toner supply to the photosensitive drum 4 becomes unstable and image degradation occurs. It was.

  In view of this, there has been proposed a method in which a sheet on which an image is formed on one side is once cooled and then transported again to the image forming unit to perform double-sided printing. A duplex unit having a cooling fan therein is disclosed.

  However, in the method of Patent Document 2, since the fan is provided inside the duplex unit, the space around the fan is not sufficient, and the air blown onto the paper cannot be sufficiently sucked. Further, since the warmed air inside the duplex unit is blown onto the paper, the cooling efficiency is also deteriorated.

Further, when air is blown from the lower side of the sheet, there is a problem that the sheet is lifted from the conveyance path and the conveyance state becomes unstable. Furthermore, since it is necessary to increase the height of the double-sided unit by the space for disposing the fan, it is not preferable from the viewpoint of downsizing the entire image forming apparatus.
JP 2001-88946 A JP 2002-304107 A

  In view of the above problems, the present invention improves the cooling efficiency of the paper in the duplex unit to suppress the temperature rise inside the apparatus during duplex printing, and at the same time realizes high density and compactness of the apparatus. The purpose is to provide.

  To achieve the above object, the present invention provides an image transfer means for transferring a toner image formed on an image carrier onto a sheet, and a toner image transferred on the sheet by the image transfer means is fixed on the sheet. A transfer unit having a fixing unit that controls the sheet transfer timing to the image transfer unit, a reversing tray for reversing a sheet on which an image is formed on one side, and a sheet reversed by the reversing tray And a double-sided unit positioned below the carrying unit, wherein the double-sided unit is open at the top of the reversing tray. In the transport unit, a fan for blowing air from above the paper transported on the reversing tray is provided.

  According to the present invention, in the image forming apparatus configured as described above, a duct that communicates the fan and the outside of the apparatus is provided in the transport unit.

  According to the present invention, in the image forming apparatus configured as described above, the fan is disposed upstream of the fixing unit and below the image transfer unit.

  According to the present invention, in the image forming apparatus configured as described above, the rotation of the fan is controlled in accordance with the conveyance of the sheet onto the reversing tray.

  According to the first configuration of the present invention, the upper part of the duplex unit is opened to expose the reversing tray, and the fan for cooling the paper on the reversing tray is provided in the transport unit, so that the air blown onto the paper is sufficiently supplied. Can be inhaled. Further, since air is blown from above the paper, the paper can be prevented from being lifted and can be stably conveyed.

  Further, according to the second configuration of the present invention, in the image forming apparatus having the first configuration, by providing the duct that communicates the fan and the outside of the apparatus in the transport unit, air outside the apparatus is always supplied It can be supplied to the fan, and the cooling effect of the paper by the fan becomes higher.

  According to the third configuration of the present invention, in the image forming apparatus having the first or second configuration, the fan is disposed on the upstream side of the fixing unit and on the lower side of the image transfer unit. The space in the unit is effectively used to realize a compact image forming apparatus.

  According to the fourth configuration of the present invention, in the image forming apparatus having any one of the first to third configurations, by controlling the rotation of the fan according to the conveyance of the sheet onto the reverse tray, The fan can be rotated only during double-sided printing that requires cooling, and the power consumption of the image forming apparatus can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front cross-sectional view illustrating the overall configuration of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the vicinity of a conveyance unit and a duplex unit in FIG. Portions common to FIGS. 7 and 8 of the conventional example are denoted by the same reference numerals and description thereof is omitted. As shown in FIGS. 1 and 2, an opening 19 a is provided in the upper part of the duplex unit 19, and the reversing tray 22 is exposed to the outside. Reference numeral 30 denotes a fan for cooling the sheet conveyed on the reverse tray 22 and is disposed above the duplex unit 19 so as to face the opening 19a.

  FIG. 3 is a perspective view showing configurations of the transport unit 17 and the duplex unit 19. Here, for convenience of explanation, the registration roller pair 12, the transfer roller 13, and the fixing unit 14 (all of which are shown in FIG. 2) in the transport unit 17 are omitted. The fan 30 is arrange | positioned at the bottom face 17a of the conveyance unit 17, and the ventilation surface (not shown) is opened downward. A duct 31 spatially communicates the fan 30 and the outside of the apparatus, and extends to the suction port 32 on the side surface of the transport unit 17 along the bottom surface 17a.

  4 is a partial cross-sectional view of the transport unit 17 and the duplex unit 19 as viewed from the direction of arrow A in FIG. As shown in FIG. 4, the suction port 32 opens near the ventilation port 34 provided in the front cover 33 of the image forming apparatus 1, and the duct 31 is connected to the outside of the apparatus via the ventilation port 34 and the suction port 32. The taken-in air can be supplied to the fan 30.

  The present invention is characterized in that a fan 30 for cooling the paper is provided in the transport unit 17 and air is blown from above onto the paper on the reversing tray 22 through the opening 19 a of the duplex unit 19. According to this configuration, a space is secured around the fan 30 as compared with the configuration in which the fan 30 is provided in the duplex unit 19, so that the air to be blown can be sufficiently sucked and the fixing unit 14 is heated. The sheet can be efficiently cooled when it is reversed on the reversing tray 22. Further, since air is blown from above the paper, the paper is not lifted from the transport path, and a stable transport state can be maintained.

  Further, the fan 30 is provided in a space on the upstream side of the fixing unit 14 in the transport unit 17 and below the transfer roller 13. The conveyance unit 17 includes a registration roller pair 12, a transfer roller 13, a fixing unit 14, and the like. Generally, as the processing speed of the image forming apparatus increases, the fixing unit 14 increases, but the transfer roller 13 increases. Does not change much. For this reason, in the high-speed machine, an empty space exists on the upstream side of the fixing unit 14 and below the transfer roller 13.

  Therefore, by disposing the fan 30 and the duct 31 in this space, it is not necessary to separately provide a space for disposing the fan 30 and the duct 31, and the height of the transport unit 17 and the duplex unit 19 is suppressed to the same level as in the past, and High density and compactness of the entire forming apparatus can be realized.

  Here, the duct 31 is provided to allow the fan 30 and the outside of the apparatus to communicate with each other. However, the duct 31 may be omitted. However, as described above, since the fan 30 is provided adjacent to the upstream side of the fixing unit 14, when the duct 31 is not provided, the air heated by the heat of the fixing unit 14 is blown onto the paper by the fan 30. As a result, the cooling efficiency of the paper decreases. Therefore, it is preferable to provide the duct 31 and always supply the cool air outside the apparatus to the fan 30.

  FIG. 5 is a plan view of the duplex unit 19. The flow of air on the duplex unit 19 will be described with reference to FIG. P is a sheet held on the reversing tray 22, and the opening 19a of the duplex unit 19 is provided in such a size that most of the sheet P is exposed when the sheet P is A4 size which is a general-purpose size. The fan 30 (see FIG. 3) is arranged at the approximate center (hatched portion in the drawing) of the opening 19a as viewed from above, and blows air from above the paper P. The blown air spreads along the surface of the paper P in the horizontal direction (arrow direction in the figure) and spreads over the entire surface of the paper, so that the whole paper can be efficiently air-cooled.

  Although the fan 30 can always be rotated, it is preferable to rotate the fan 30 only when double-sided printing is selected by the user and the sheet is conveyed onto the reversing tray 22 and to stop the rest. It is more preferable because the power consumption of the forming apparatus can be reduced. FIG. 6 is a flowchart illustrating an example of a fan drive control procedure associated with image formation. With reference to FIGS. 1 and 2, the sheet cooling operation in the duplex unit will be described in accordance with the steps in FIG.

  First, when image formation is started by a user operation (step S1), it is determined whether or not double-sided printing processing is selected by a control unit (not shown) such as a CPU provided in the image forming apparatus. (Step S2). When duplex printing is performed, the control unit transmits a control signal to rotate the fan 30 (step S3), and cools the sheet conveyed on the reverse tray 22. Next, it is determined whether or not double-sided printing processing is continued (step S4). If double-sided printing is continuously performed, the fan 30 is rotated as it is. If double-sided printing is not performed continuously, the control means transmits a control signal to stop the fan 30 (step S5).

  On the other hand, if the double-sided printing process is not selected in step S2, the control unit keeps the fan 30 stopped (step S5). Then, it is determined whether or not the image forming process is finished (step S6), and if the image forming is finished, the process is finished. On the other hand, when image formation is continuously performed, the process returns to step S2, and the same procedure is repeated thereafter (steps S2 to S6).

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the duct 31 is configured to extend toward the front side of the apparatus along the bottom surface 17a of the transport unit 17. However, the duct 31 may be extended toward the rear side of the apparatus. 32 and the vent hole 34 provided in the apparatus main body may be provided on the rear side. Although only a digital multi-function peripheral is shown here as a double-sided printing type image forming apparatus equipped with a double-sided unit, the present invention is an analog type copying machine, a tandem color image forming apparatus, a facsimile, a laser printer, etc. Of course, the present invention can be applied to other types of image forming apparatuses.

  The present invention relates to an image transfer unit that transfers a toner image formed on an image carrier onto a sheet, a fixing unit that fixes the toner image transferred onto the sheet by the image transfer unit, and an image transfer unit. A transfer unit having a registration unit for controlling the sheet transfer timing to the means, a reversing tray for reversing the sheet on which an image is formed on one side, and the sheet reversed by the reversing tray to the image transfer unit. An image forming apparatus including a re-conveying unit and a duplex unit positioned below the transport unit. The duplex unit has an upper part of the reversing tray open, and the reversing unit has a reversing unit on the reversing tray. It is assumed that a fan that blows air from above the sheet conveyed to the printer is provided.

  As a result, even when continuous duplex printing is performed, the temperature of the image forming unit does not increase due to the heat of the re-conveyed paper. There is no possibility that the toner supply onto the drum becomes unstable and image degradation occurs. Further, since air is blown from above the sheet, there is no possibility that the sheet will float from the conveyance path, and stable sheet conveyance is possible.

  Further, since the duct that communicates the fan and the outside of the apparatus is provided in the transport unit, the cold air outside the apparatus can always be supplied to the fan, and the air cooling effect of the paper by the fan is further enhanced.

  In addition, since the fan is arranged on the upstream side of the fixing unit and below the image transfer means, the empty space in the conveyance unit can be effectively used without providing a space for arranging the fan and the duct. The unit height is reduced to the same level as before, contributing to higher density and compactness of the entire image forming apparatus.

  In addition, since the rotation of the fan is controlled according to the conveyance of the paper onto the reversing tray, the fan is rotated during duplex printing that requires cooling of the paper, and the fan is stopped during standby or single-sided printing. By doing so, it is possible to reduce the power consumption of the image forming apparatus and contribute to a reduction in running cost and energy saving.

FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic enlarged view of the periphery of a transport unit and a duplex unit in FIG. 1. FIG. 3 is a perspective view showing configurations of a transport unit and a duplex unit. These are the fragmentary sectional views which show the structure of a conveyance unit and a double-sided unit. These are top views of a duplex unit. These are the flowcharts which show an example of the drive control procedure of the fan accompanying image formation. FIG. 1 is a schematic diagram showing an overall configuration of a conventional image forming apparatus equipped with a duplex unit. FIG. 8 is a schematic enlarged view of the periphery of the transport unit and the duplex unit in FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 3 Charging unit 4 Photosensitive drum 5 Image reading part 7 Developing unit 8 Exposure unit 12 Registration roller pair (registration unit)
13 Transfer roller (image transfer means)
14 Fixing Unit 17 Conveying Unit 19 Duplex Unit 22 Reversing Tray 24a, 24b, 24c Conveying Roller (Reconveying Unit)
25a, 25b, 25c driven roller (re-conveying means)
30 Fan 31 Duct 32 Suction port 33 Front cover 34 Ventilation port

Claims (4)

An image transfer means for transferring the toner image formed on the image carrier onto the paper; a fixing unit for fixing the toner image transferred onto the paper by the image transfer means; on the paper; A transport unit having a registration unit for controlling paper transport timing;
A double-sided tray having a reversing tray for reversing a sheet on which an image is formed on one side and a re-conveying unit for re-conveying the sheet reversed by the reversing tray to the image transfer unit; An image forming apparatus comprising: a unit;
2. The image forming apparatus according to claim 1, wherein an upper part of the reversing tray is opened in the duplex unit, and a fan that blows air from above the sheet conveyed on the reversing tray is provided in the conveying unit.   The image forming apparatus according to claim 1, wherein a duct that communicates the fan and the outside of the apparatus is provided in the transport unit.   The image forming apparatus according to claim 1, wherein the fan is disposed upstream of the fixing unit and below the image transfer unit.   The image forming apparatus according to claim 1, wherein the rotation of the fan is controlled in accordance with the conveyance of the sheet onto the reversing tray.

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