JP2009214975A - Curl correction device, image forming device, copying machine, and printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curl correction device where a curl correcting force is varied according to the thickness of paper sheet and a conveying force of the paper can be easily secured. <P>SOLUTION: When receiving the conveying force of the paper, a driven roller 23 is turned to a direction away from a decurler inlet roller 21 with a support shaft 26 of a decurler outlet roller 22 as a center together with an oscillating bracket 24 withstanding an energizing force of a spring 29. Therefore, even if the driven roller 23 is moved by receiving the stiffness strength of paper 3, the force for furthering a curl can be reduced by turning the oscillating bracket 24. The nip of the driven roller 23 and the decurler outlet roller 22 can be maintained by a pressure force of a driven compression spring 27. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a curl correction apparatus that corrects curl of paper, and in particular, is applied to an image forming unit such as a copying machine or a printer equipped with a curl correction apparatus.

  In a conventional electrophotographic image forming apparatus, when a toner image transferred onto a sheet by a heating and pressing type fixing apparatus composed of a fixing roller and a pressure roller is fused and fixed on the sheet, the nip shape of the fixing roller or the fixing roller The paper curls due to the temperature difference between the pressure roller and the pressure roller. Such curled paper may be jammed, resulting in a stack failure or paper misalignment in the post-processing device.

  FIG. 5 is a schematic configuration diagram of an example of a conventional image forming apparatus. The image forming apparatus conveys a sheet 3 loaded on a sheet feeding tray 2 in the apparatus main body 1 by a sheet feeding roller 4 to register rollers. The image 5 and the paper are aligned by the pair 5, and the toner image formed on the photoreceptor 6 is transferred to one side of the paper 3 by the transfer belt 7. After the transfer, the toner image on the surface of the sheet 3 is pressurized and heated by the fixing unit 8 including a pair of rollers 8 a and 8 b, and the toner image is melted and fixed on the sheet 3. Thereafter, when an image is not formed on the other surface of the paper 3, the paper 3 is sent to the paper discharge roller pair 11 through the decurler roller pair 10 by the branching claw 9 and discharged to the paper discharge tray 12.

  The decurler roller pair 10 corrects the curl attached to the paper 3. Various measures have been made to effectively perform the curl correction (Patent Document 1).

  Further, as shown in FIG. 6, in the curl correction unit, the curling upward of the paper 3 is lowered by the pressing force of the decurler driven roller 13 and the paper bending (paper turn) shape of the decurler inlet roller 14 and the decurler outlet roller 15. There is a configuration to bend the side.

Japanese Patent Application Laid-Open No. 2004-228561 describes a configuration in which the setting of the nip position relationship between the pair of conveying rollers and the pair of movable rollers constituting the curl correction unit is changed according to the degree of curl correction for the paper.
Japanese Patent Laid-Open No. 11-305508 JP 2007-137552 A

  As described above, the size and direction of the curl of the paper vary depending on the paper quality, thickness, temperature and humidity of the paper, and the like. It is desirable that various curl correction devices have been proposed and implemented.

  In the curl correction apparatus described in FIG. 6 or Patent Document 2, a plurality of curling correction driving rollers and driven rollers are used to cope with various paper curling states. In the configuration shown in FIG. This curls the sheet 3 in which the curl direction is on the lower side. In particular, in the case of thick paper, the curl shape is often in the same direction as the turn shape of the paper conveyance path, and curling is promoted by the decurler.

  Further, when the thick paper is conveyed, the driven roller 13 loses the stiffness of the paper and escapes, so that a nip cannot be formed and the conveying force may be reduced. For this reason, if the pressure applied by the spring, etc., to the driven roller is increased so that the driven roller does not escape, the paper may be wrinkled when transporting thin paper. Even if the pressure is not large, the paper should be transported satisfactorily. A mechanism that can be used is required.

  Further, in the configuration described in Patent Document 2, the positional relationship between the conveying roller pair and the movable roller pair constituting the curl correction unit can be changed according to the degree of curl correction with respect to the paper. A complicated operation such as changing the amount of rotation of the supporting plate to be supported and fixing the supporting plate with screws is necessary.

  Therefore, the present invention solves the above-described problems of the prior art, and the curl correction force varies according to the thickness of the paper, and the curl correction device and image forming apparatus can easily secure the paper conveyance force. And a copying machine and a printer.

  In order to achieve the above object, the invention according to claim 1 is provided with two driving rollers for conveying a sheet and one driven roller in contact with the driving roller, and curling the conveyed sheet. In the curl correction device for correcting the driving roller and the driven roller according to the pressing force and the turn shape, the driving roller is capable of contacting and separating with respect to one of the driving rollers by receiving a sheet conveying force. The other roller is supported so as to be able to swing, and this structure allows the driven roller to swing by receiving the paper transport force, making it suitable for the drive roller even during thick paper transport. A proper nip can be formed to achieve an appropriate conveyance state, and a reduction in conveyance force can be prevented.

  According to a second aspect of the present invention, in the curl straightening device according to the first aspect, the driven roller is supported so as to be swingable about the rotation axis of the other driving roller, and the driven roller, the driving roller, While the positional relationship is maintained, the driven roller can be easily and reliably swung.

  According to a third aspect of the present invention, in the curl straightening device according to the first or second aspect, an elastic member that presses the driven roller against the other driving roller is provided. It is possible to reduce the conveyance force and prevent the nip from changing.

  According to a fourth aspect of the present invention, in the curl straightening device according to any one of the first to third aspects, an elastic member that presses the driven roller against one of the driving rollers is provided. Thus, it is possible to prevent the driven roller from escaping in response to the conveyance force of the sheet and generating a conveyance path shape that promotes curling.

  According to a fifth aspect of the present invention, in the curl straightening device according to any one of the first to fourth aspects, the other driving roller is disposed downstream of the one driving roller in the sheet conveying direction. With this configuration, it is possible to prevent the driven roller from escaping due to the conveyance force of the sheet and to generate a sheet turn shape that promotes curling, and to secure an appropriate nip. .

  According to a sixth aspect of the present invention, in the curl straightening device according to any one of the first to fifth aspects, the pressure contact force of the driven roller with respect to the other drive roller is larger than the pressure contact force with respect to the one drive roller. Characteristically, this configuration can prevent the driven roller from escaping upon receiving the paper conveying force to generate a paper turn shape that promotes curling, and ensures an appropriate nip.

  According to a seventh aspect of the present invention, in the image forming apparatus including an image forming unit that forms an image on a sheet and a conveying unit that conveys the sheet in a predetermined direction, the conveying unit includes any one of the first to sixth aspects. The curl correcting apparatus according to claim 1 is installed.

  The invention according to claim 8 is characterized in that the image forming apparatus according to claim 7 is mounted in a copying machine.

  The invention according to claim 9 is characterized in that the image forming apparatus according to claim 7 is mounted in a printer.

  According to the curl correcting device of the present invention, the driven roller is supported by the other driving roller so as to be able to contact with and separate from the one driving roller by receiving the sheet conveying force, and to swing the other driving roller. The driven roller swings in response to the transport force and forms an appropriate nip with the drive roller. Therefore, even when transporting thick paper, it can be transported without forming a paper turn shape that promotes curling. Good curl correction can be realized while maintaining the paper transportability, such as prevention of force reduction.

  According to the image forming apparatus, the copying machine, and the printer according to the present invention, since the curl correction is performed while maintaining the paper transportability in the paper transport path, it is possible to always stably output a high-quality image. .

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an electrophotographic image forming apparatus for explaining an embodiment of the present invention, and members corresponding to those described in FIGS. Description is omitted.

  In FIG. 1, a sheet 3 stacked on a sheet feed tray 2 in the apparatus main body 1 is fed to a registration roller pair 5 by a sheet feeding roller 4, and the sheet 3 corresponding to an image on a photoconductor 6 by a registration roller pair 5. Then, the toner image formed on the photoconductor 6 is transferred to one surface of the paper 3 at the nip between the photoconductor 6 and the transfer belt 7. After the transfer, the toner image on the paper 3 is pressed and heated by the fixing unit 8 including the rollers 8 a and 8 b to melt and fix the toner image on the paper 3.

  In the fixing unit 8, the left side in FIG. 1 is a roller 8a made of an elastic body, the right side is a metal roller 8b, and the roller 8a made of an elastic body is concave so that it is crushed by the metal roller 8b. It has become elastic. For this reason, the sheet 3 that has passed through the fixing unit 8 is deformed into a convex shape in the direction of the concave roller 8a. Therefore, in FIG. Is done.

  When the image 3 is not formed on the other side of the sheet 3, the sheet 3 that has undergone the fixing process is conveyed by the branching claw 9 through the curl correction unit 20 and discharged to the sheet discharge tray 12 by the sheet discharge roller pair 11.

  FIG. 2 is an enlarged configuration diagram of the curl correction unit. The curl correction unit 20 is a decurler entrance roller that is two drive rollers that are driven to rotate by a driving means (not shown) to convey the paper 3. 21 and a decurler outlet roller 22, and a driven roller 23 contacts between the rollers 21 and 22 to form a nip. With this configuration, as described above, the curl correction is performed by applying a roller force that has a convex shape on the upper side to the paper 3 that has a convex curl on the lower side.

  The driven roller 23 is pivotally supported on the support shaft 25 at a substantially central portion of the swing bracket 24. The upper part of the swing bracket 24 is pivotally supported by a support shaft 26 of a decurler outlet roller 22 installed on the downstream side in the sheet conveying direction a, and the driven roller 23 can contact and separate from the decurler inlet roller 21. It is supposed to be.

  In FIG. 2, 27 is a driven compression spring that applies a biasing force to the nip portion between the driven roller 23 and the decurler outlet roller 22 via the swing bracket 24, 28 is a bearing of the support shaft 25, and 29 is the driven roller 23. It is a spring that urges the decurler inlet roller 21 so as to be in contact therewith.

  Here, in the conventional curl correction apparatus shown in FIG. 6, the decurler driven roller 13 escapes in the direction of the arrow b under the force of the stiffness of the paper 3 when transporting thick paper, and the curl by the decurler driven roller 13 is promoted. Although the shape is not formed and curling is not promoted, the decurler outlet roller 15 and the decurler driven roller 13 do not form a nip, so the conveying force is reduced.

  On the other hand, in the present embodiment, when the sheet conveying force is received, the driven roller 23 together with the swing bracket 24 against the urging force of the spring 29 is shown in FIG. 3 centering on the support shaft 26 of the decurler outlet roller 22. As described above, since it rotates in a direction away from the decurler entrance roller 21, even when the driven roller 23 moves (escapes) due to the stiffness of the paper 3, the swing bracket 24 rotates, The force that promotes curling can be reduced, and the nip between the driven roller 23 and the decurler outlet roller 22 can be maintained by the pressure of the driven compression spring 27.

  In the configuration example shown in FIG. 4, by adjusting the pressing force of the driven compression spring 27 and the spring 29, the pressing force applied to the decurler outlet roller 22 by the driven roller 23 is larger than the pressing force of the decurler inlet roller 21. The driven roller 23 is separated by receiving the force of the paper 3 and the nip with the decurler inlet roller 21 is not formed, while the nip between the driven roller 23 and the decurler outlet roller 22 is formed. Thus, by preventing the generation of a paper turn shape that promotes curling, curling promotion during transport of thick paper can be reduced.

  By mounting the curl correction unit having the configuration of the above embodiment on an electrophotographic image forming apparatus mounted on a copying machine, a printer, or the like, high-quality image output can be stably performed.

  The present invention is effective when applied to a high-performance image forming apparatus that requires that curl correction be reliably performed according to the thickness of the paper.

1 is a schematic configuration diagram of an electrophotographic image forming apparatus for explaining an embodiment of the present invention. The block diagram which shows the curl correction part in this embodiment The block diagram which shows the state at the time of operation | movement of the curl correction part in this embodiment. The block diagram of the other example of the curl correction part in this embodiment Schematic configuration diagram of a conventional electrophotographic image forming apparatus Configuration diagram showing a curl correction unit in a conventional example

Explanation of symbols

3 Paper 4 Paper feed roller 8 Fixing unit 20 Curl correction unit 21 Decurler entrance roller 22 Decaler exit roller 23 Driven roller 24 Swing bracket 27 Driven compression spring 28 Bearing 29 Spring a Paper transport direction

Claims (9)

Two drive rollers for conveying the paper and one driven roller in contact with the drive roller are provided, and the curl of the conveyed paper is caused by the pressing force and turn shape of the drive roller and the driven roller. In the curl correction device to correct,
An anti-curl correcting apparatus characterized in that the driven roller is supported so as to be able to contact and separate with respect to one of the drive rollers by receiving a sheet conveying force and to be swingable with respect to the other of the drive rollers.   2. The curl correcting device according to claim 1, wherein the driven roller is supported so as to be swingable about a rotation shaft of the other driving roller.   3. The curl correction apparatus according to claim 1, further comprising an elastic member that presses the driven roller against the other driving roller.   The curl correction apparatus according to claim 1, further comprising an elastic member that presses the driven roller against the one driving roller.   The curl correction apparatus according to any one of claims 1 to 4, wherein the other drive roller is disposed on the downstream side in the paper conveyance direction with respect to the one drive roller.   6. The curl correction apparatus according to claim 1, wherein a pressure contact force of the driven roller with respect to the other drive roller is larger than a pressure contact force with respect to the one drive roller.   The curl correction apparatus according to claim 1, wherein the image forming apparatus includes an image forming unit that forms an image on a sheet and a conveyance unit that conveys the sheet in a predetermined direction. An image forming apparatus characterized by being installed.   A copier, comprising the image forming apparatus according to claim 7.   A printer comprising the image forming apparatus according to claim 7.

Images