JP2006219239A - Double-side unit and image forming device having it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-side unit capable of preventing occurrence of a switch back failure and a jam by smoothly carrying paper; and to provide an image forming device having it. <P>SOLUTION: A brush roller 31 with multiple hairy bodies 30 planted on its circumferential surface is arranged in a branch part of double-side recording paths 18a and 18b. The brush roller 31 is rotatably driven in a paper carrying direction (the arrow B direction in this case) by a motor 33 by using a spindle 32 as a rotation center, and assists the conveyance of the paper passing the branch part along with a branch guide 28. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a duplex unit that switches a sheet conveyance direction and reverses the front and back, and an image forming apparatus such as a copying machine and a printer including the unit, and more particularly, to a sheet conveyance mechanism that forms an image 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. 5 shows a schematic configuration of an image forming apparatus equipped with a duplex unit.

  In FIG. 5, 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 performing a copy operation, the photosensitive drum 4 that rotates clockwise (in the direction of the arrow in the figure) is uniformly charged by the charging unit 3 in the image forming unit 2 in the main body of the multifunction peripheral. 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 document image data read by the image reading unit 5, and an electrostatic latent image is formed by the developing unit 7. A developer (hereinafter referred to as toner) is attached to form a toner image. The toner is supplied to the developing unit 7 from the toner container 6.

  A sheet is conveyed from the sheet feeding mechanism 9 to the image forming unit 2 via the sheet feeding roller 10, the sheet conveying path 11, and the resist roller pair 12 toward the photosensitive drum 4 on which the toner image is formed as described above. In this image forming unit 2, the toner image formed on the surface of the photosensitive drum 4 by the transfer roller 13 is transferred to the paper. 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 the paper, the paper that has passed through the fixing unit 14 is distributed to the double-sided recording path 18 by the branching unit 15, and is reversed by the switchback roller pair 20 in the double-sided unit 19. Are re-conveyed to the image forming unit 2 with the surface on which the film is 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. 6 is an enlarged view of the vicinity of the transport unit 17 and the duplex unit 19 in FIG. When the user selects the double-sided printing mode, the paper on which the toner image is formed on one side in the image forming unit 2 is conveyed to the fixing unit 14 and the toner image is fixed, and then to the double-sided recording path 18 in the branching unit 15. They are sorted and conveyed to the duplex unit 19 via the conveying roller 24a and the driven roller 25a. The conveyed sheet is temporarily held on the reverse tray 22 by a switchback roller pair 20 including switchback rollers 20a and 20b. At this time, the image surface is facing downward. The switchback roller pair 20 and the reversing tray 22 constitute reversing means for reversing the orientation of the image surface by switching the paper transport direction.

  Subsequently, the switchback rollers 20a and 20b are rotated in the reverse direction to convey the paper on the reverse tray 22 to the lower part of the duplex unit 19. Then, it passes through the re-conveying means composed of the driving roller 23, the conveying rollers 24b, 24c, 24d and the driven rollers 25b, 25c, 25d 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 25b from the transport roller 24b, 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. 5).

  FIG. 7 is an enlarged view showing the structure around the switchback roller in FIG. The switchback operation of the duplex unit 19 will be described in more detail with reference to FIG. The conveyance roller 24a rotates counterclockwise (in the direction of arrow A) and the driven roller 25a rotates in the clockwise direction (in the direction of arrow B), whereby the sheet P is fed along the branch guide 28 to the duplex recording path 18a (first conveyance path). ) In the direction of arrow C, and reaches the nip portion of the switchback rollers 20a, 20b provided in the duplex unit 19.

  Then, the switchback roller 20a rotates counterclockwise (arrow A direction) and 20b rotates clockwise (arrow B direction), and the paper P is conveyed in the arrow D direction and guided onto the reverse tray 22. The sheet P held on the reversing tray 22 is rotated by rotating the switchback roller 20a clockwise (arrow B direction) and 20b counterclockwise (arrow A direction). The road) is conveyed in the direction of arrow D '.

  In such a duplex unit, when the paper P is carried from the branch guide 28 onto the reversing tray 22, the distance from the transport roller 24a and the driven roller 25a to the tip of the branch guide 28 is long. Therefore, as shown in FIG. The rear end of P may remain on the branch guide 28. When the switchback rollers 20a and 20b are rotated in reverse in this state, the paper P sent out from the reverse tray 22 to the double-sided recording path 18b enters the double-sided recording path 18a again, causing a jam, and the image plane is switched. There was a problem that it could not be performed smoothly.

  Therefore, a method for preventing the jammed paper by preventing the switched-back paper P from entering the double-sided recording path 18a has been proposed. When the paper is transported to the switchback position, the elastic member is pushed by the leading edge of the paper and bent to allow the paper to pass. After passing through the paper, the elastic member returns to its original shape, and after the switchback, A double-sided recording apparatus configured to prevent the paper from entering the double-sided recording path is disclosed.

However, in the method of Patent Document 2, if the paper to be conveyed is weak, the elastic member cannot be sufficiently bent, and a jam may occur when the paper is brought into the switchback position. Even when the paper is strong, for example, when the trailing edge of the paper (the leading edge after the switchback) is wound, the elastic member is pushed up after the switchback to enter the double-sided recording path. Is also possible.
JP 2001-88946 A JP 2003-312915 A

  SUMMARY An advantage of some aspects of the invention is that it provides a double-sided unit that smoothly conveys a sheet to prevent defective switchback and jamming, and an image forming apparatus including the double-sided unit.

  In order to achieve the above object, the present invention provides a reversing tray, a first transport path for transporting paper on the reverse tray, a second transport path for re-transporting paper reversed by the reverse tray, And a bifurcating guide provided at a branching portion of the first and second transport paths, and arranged at the branching unit in a duplex unit that reverses the front and back of the paper by switching the paper transporting direction on the reversing tray. The rear end of the paper transported from the first transport path is pushed and guided onto the reverse tray, and the front end of the paper fed from the reverse tray is pressed to the second transport path. And a driving means for rotationally driving the guide roller in the sheet conveying direction.

  According to the present invention, in the double-sided unit configured as described above, the circumferential speed of the guide roller is set to be substantially the same as the paper conveyance speed.

  According to the present invention, in the double-sided unit configured as described above, the guide roller is a brush roller in which a large number of hairs are radially arranged on an outer peripheral surface of a cylindrical roller body.

  According to the present invention, in the double-sided unit configured as described above, the guide roller is a finned roller in which a plurality of fins are radially provided on an outer peripheral surface of a cylindrical roller body.

  The present invention is also an image forming apparatus on which the duplex unit having the above-described configuration is mounted.

  According to the first configuration of the present invention, the guide roller for assisting the switchback of the paper is arranged at the branch portion of the duplex unit, and rotated in the paper transport direction using the driving means, whereby the strength and winding of the paper are reduced. Regardless of the presence or absence of defects, it is possible to effectively prevent conveyance failure and jamming during switchback.

  According to the second configuration of the present invention, in the duplex unit of the first configuration, the circumferential speed of the guide roller is substantially the same as the paper conveyance speed, so that the rotation of the guide roller is the paper conveyance speed. The switchback operation becomes more stable.

  According to the third configuration of the present invention, in the double-sided unit having the first or second configuration, a large number of hairs are radially arranged on the outer peripheral surface of the cylindrical roller body as the guide roller. By using the brush roller, the rear end of the paper and the press of the front end of the paper are reliably performed, and the switchback can be performed more smoothly.

  According to the fourth configuration of the present invention, in the double-sided unit having the above-described first or second configuration, a fin in which a plurality of fins are erected radially on the outer peripheral surface of a cylindrical roller body as a guide roller. By using the attached roller, the switchback can be performed more smoothly as in the case of the brush roller.

  Further, according to the fifth configuration of the present invention, the double-sided unit having any one of the first to fourth configurations is mounted on the image forming apparatus, thereby reducing the occurrence of paper conveyance failure or jamming during double-sided printing. Thus, stable image formation becomes possible.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view showing a structure around a switchback roller of a duplex unit according to the first embodiment of the present invention. Portions common to FIG. 7 of the conventional example are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 1, a brush roller 31 in which a large number of hairs 30 are implanted on the outer peripheral surface is disposed at a branch portion of the double-sided recording paths 18a and 18b. The brush roller 31 is rotationally driven by the motor 33 around the support shaft 32 in the sheet conveyance direction (in the direction of arrow B in this case), and assists conveyance of the sheet passing through the branch portion together with the branch guide 28.

  FIG. 2 is an enlarged view showing the structure around the brush roller 31 in FIG. With reference to FIG. 1, a paper switchback mechanism using the branch guide 28 and the brush roller 31 will be described with reference to FIG. The sheet conveyed in the double-sided recording path 18a by the conveying roller 24a and the driven roller 25a advances along the branch guide 28 in the direction of arrow C. The brush roller 31 is disposed so that the tip of the hair 30 protrudes a predetermined amount into the double-sided recording paths 18a and 18b in order to reliably assist the conveyance of the paper.

  When the trailing edge of the paper P passes through the brush roller 31, the trailing edge of the paper P (broken line) is pushed in the arrow C direction by the hair 30 of the brush roller 31 rotating in the arrow B direction. Therefore, even if the rear end of the paper P remains on the branch guide 28 as shown in FIG. 7 after the rear end of the paper P is separated from the transport roller 24a and the driven roller 25a, the front end of the paper P is surely switched back. It reaches the rollers 20a and 20b and is held on the reverse tray 22.

  On the other hand, the leading edge of the paper P that has been switched back from the reverse tray 22 in the direction of the arrow D ′ is pressed downward by the hair 30 of the brush roller 31 that rotates in the direction of the arrow B and guided to the double-sided recording path 18 b. The As a result, even when the paper P (solid line) with a leading edge is switched back, the paper after the switch back does not enter the duplex recording path 18a.

  Therefore, by adopting the configuration of the present embodiment in which the brush roller 31 is provided at the branch portion of the double-sided recording paths 18a and 18b, when the paper is carried from the double-sided recording path 18a to the reverse tray 22 and from the reverse tray 22 to the double-sided recording path 18b. It is possible to effectively prevent paper conveyance failure and jamming when the paper is sent to the printer.

  If the peripheral speed of the brush roller 31 is too fast or too slow with respect to the sheet conveyance speed, the sheet conveyance is affected and the switchback operation becomes unstable. Therefore, it is preferable to set the peripheral speed of the brush roller 31 to a speed that is substantially the same as the conveyance speed. Further, the material of the hair-like body 30 implanted in the brush roller 31 is not particularly limited. However, if the hair-like body 30 is too hard, there is a risk of damaging the paper to be transported. Can not assist the transport of Therefore, it is preferable to use a synthetic resin or the like that has appropriate flexibility and resilience and is excellent in durability.

  FIG. 3 is a partial cross-sectional view showing the structure around the switchback roller of the double-sided unit according to the second embodiment of the present invention. Portions common to FIG. 1 are denoted by the same reference numerals and description thereof is omitted. In this embodiment, instead of the brush roller 31 of the first embodiment, a finned roller 35 in which a plurality of fins 34 are arranged radially is arranged on the outer peripheral surface. Other configurations are the same as those of the first embodiment.

  The finned roller 35 of the present embodiment exhibits the same function as the brush roller 31 shown in FIG. 2 by rotating in the arrow B direction. That is, the trailing edge of the paper carried into the reverse tray 22 from the double-sided recording path 18a is boosted by the fins 34, and the leading edge of the paper sent from the reverse tray 22 to the double-sided recording path 18b is pressed downward. As a result, similarly to the first embodiment, it is possible to effectively prevent paper conveyance failure and jamming during switchback.

  Although the number of fins 34 can be arbitrarily set, it is necessary to provide as many fins 34 as possible in order to reliably guide the paper. Here, finned rollers provided with eight fins 34 are provided. 35 is used. The peripheral speed of the finned roller 35 is preferably set to substantially the same speed as the conveying speed in the same way as the brush roller 31 of the first embodiment, and the material of the fin 34 is also a synthetic resin as in the hair 31. Etc. are preferably used.

  As described above, the duplex unit of the first and second embodiments including the brush roller 31 or the finned roller 35 is mounted on the image forming apparatus as shown in FIG. An image forming apparatus capable of reducing the occurrence of conveyance failure and jam with a simple configuration and performing stable double-sided printing can be realized at low cost.

  The brush roller 31 or the finned roller 35 can be always rotated. However, the brush roller 31 or the finned roller 35 is rotated only when the duplex printing is selected by the user and the sheet is conveyed onto the reverse tray 22, and the rest is stopped. It is more preferable that the power consumption of the image forming apparatus is reduced. FIG. 4 is a flowchart illustrating a drive control procedure of the brush roller 31 associated with image formation in the image forming apparatus including the duplex unit according to the first embodiment. With reference to FIG. 1, the drive control of the brush roller 31 will be described according to the steps of 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 means transmits a control signal to the motor 33 to rotate the brush roller 31 (step S3). Next, it is determined whether or not double-sided printing processing is continued (step S4). If double-sided printing is continued, the brush roller 31 is rotated as it is. If double-sided printing has been completed, the control means transmits a control signal to the motor 33 to stop the brush roller 31 (step S5).

  On the other hand, if the duplex printing process is not selected in step S2, the control means does not transmit a control signal to the motor 33, and the brush roller 31 does not rotate. 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 S5). Here, the double-sided unit of the first embodiment provided with the brush roller 31 has been described as an example, but the double-sided unit of the second embodiment provided with the finned roller 35 can also be controlled in the same procedure. .

  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 motor 33 that drives the brush roller 31 or the finned roller 35 may be a dedicated motor, or may be combined with a motor that drives other members such as the transport roller 24a. 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 a reversing tray, a first transporting path for transporting paper on the reversing tray, a second transporting path for re-transporting paper reversed by the reversing tray, and the first and second transporting paths. And a bifurcating guide disposed on the reversing tray, which is disposed on the bifurcating unit and is conveyed from the first conveying path. The rear end of the incoming paper is pushed and guided onto the reverse tray, and the guide roller that guides the second transport path by pressing the front end of the paper fed from the reverse tray, and the guide roller in the paper transport direction Driving means for rotationally driving is provided.

  As a result, a duplex unit that can effectively prevent a paper conveyance failure or jam at the time of switchback and can perform a stable switchback operation regardless of the strength of the paper and the presence or absence of winding. Can be provided at a cost. Further, if the circumferential speed of the guide roller is substantially the same as the paper transport speed, the paper transport is not affected by the rotation of the guide roller, and the switchback operation becomes more stable.

  Further, since the brush roller or the finned roller is used as the guide roller, the rear end of the paper and the front end of the paper are reliably pressed, and a smoother switchback operation is possible.

  Also, by installing the duplex unit of the present invention, it is possible to realize an image forming apparatus that can stably perform duplex printing at low cost by reducing the occurrence of paper conveyance failure and jamming during duplex printing with a simple configuration. It becomes.

These are the fragmentary sectional views which show the structure around the switchback roller of the duplex unit according to the first embodiment of the present invention. FIG. 2 is an enlarged view showing a structure around a brush roller in FIG. 1. These are the fragmentary sectional views which show the structure around the switchback roller of the duplex unit according to the second embodiment of the present invention. These are flowcharts which show an example of the drive control procedure of the brush roller accompanying image formation in the image forming apparatus provided with the duplex unit of the first embodiment. FIG. 1 is a schematic diagram showing an overall configuration of a conventional image forming apparatus equipped with a duplex unit. FIG. 6 is a schematic enlarged view of the periphery of the transport unit and the duplex unit in FIG. 5. These are the fragmentary sectional views which show the structure of the switchback roller periphery in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 5 Image reading part 18a Double-sided recording path (1st conveyance path)
18b Double-sided recording path (second transport path)
DESCRIPTION OF SYMBOLS 19 Duplex unit 20 Switchback roller pair 20a, 20b Switchback roller 22 Reverse tray 24a-24d Conveyance roller 25a-25d Follower roller 28 Branch guide 30 Hair body 31 Brush roller (Guide roller)
32 Support shaft 33 Motor (drive means)
34 Fin 35 Roller with fin (guide roller)

Claims (5)

A reversing tray, a first transporting path for transporting paper onto the reversing tray, a second transporting path for re-transporting paper reversed by the reversing tray, and a branch between the first and second transporting paths A double-sided unit that reverses the front and back of the paper by switching the paper transport direction on the reversing tray,
The rear end of the paper that is disposed in the branching section and is conveyed from the first transport path is pushed and guided onto the reverse tray, and the front end of the paper fed from the reverse tray is pressed to A double-sided unit comprising a guide roller for guiding to a second transport path, and a driving means for driving the guide roller to rotate in the paper transport direction.   The duplex unit according to claim 1, wherein a circumferential speed of the guide roller is set to be substantially the same as a sheet conveyance speed.   The double-sided unit according to claim 1 or 2, wherein the guide roller is a brush roller in which a large number of hairs are planted on an outer peripheral surface of a cylindrical roller body.   3. The duplex unit according to claim 1, wherein the guide roller is a finned roller in which a plurality of fins are radially provided on an outer peripheral surface of a cylindrical roller body. 4.   An image forming apparatus on which the duplex unit according to claim 1 is mounted.

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