JP2008094507A - Image forming device and curl correction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of correcting curl of paper, without generating wrinkles in the paper. <P>SOLUTION: A constitution of this curl correction device corrects the curl of the paper by being arranged on the downstream side in the paper carrying direction of a fixing device for fixing an image to the paper by using at least heat, and has a first curl correction roller 23 arranged in the direction orthogonal to the paper carrying direction, a second curl correction roller 24 softer than the first curl correction roller 23, and a deflection preventive member 29 preventing deflection generated in the first curl correction roller 23 when pressing the first curl correction roller 23 to the second curl correction roller 24. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a curl correction apparatus that corrects curling of a sheet and an image forming apparatus including the curl correction apparatus.

  In general, an electrophotographic image forming apparatus forms an image on a sheet by an image forming process including charging, exposure, development, transfer, and fixing. In the fixing process, the toner image transferred to the paper in the previous transfer process is fixed on the paper by heating and pressing. For this reason, the fixing device is provided with a pair of fixing rolls, one of which is a heating roll and the other is a pressure roll.

  In such an image forming apparatus including a heat fixing type fixing device that fixes an image (toner) on a sheet using heat, the image may be curled when the image is fixed on the sheet. The curl of the paper causes a paper jam (jam) and deterioration of the paper storage capacity in the discharge tray. For this reason, Patent Document 1 proposes an image forming apparatus including a curl correcting device that corrects curling of a sheet after image fixing. In the technique described in Patent Document 1, a curl correcting roll pair composed of a hard roll and a soft roll is provided on the downstream side of the fixing device in the sheet conveying direction, and the sheet after image fixing is placed between the curl correcting roll pair (contact portion). It is a mechanism to correct the curl of the paper by passing it through.

JP 2005-35731 A

  However, in order to correct the curl of the paper with the above-described curl correction roll pair, a hard roll having a smaller diameter than that of the soft roll is used in order to partially dent the peripheral surface of the soft roll by the biting of the hard roll. It is necessary to press strongly. For this reason, for example, as shown in FIG. 10, when the small-diameter hard roll 51 is pressed against the soft roll 52, the paper 53 may be wrinkled due to the bending of the hard roll 51.

  An object of the present invention is to provide an image forming apparatus capable of correcting paper curl without causing wrinkles on the paper.

According to a first aspect of the present invention, there is provided a fixing device that fixes an image on a sheet using at least heat, and a curl correction device that is provided downstream of the fixing device in a sheet conveying direction and corrects the curl of the sheet. The curl correction device includes a first curl correction member formed in a roll shape and provided in a direction orthogonal to the paper conveyance direction, and a second curl correction member softer than the first curl correction member. An image forming apparatus comprising: a bend preventing member for preventing bend generated in the first curl correcting member when the first curl correcting member is pressed against the second curl correcting member. .
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the second curl correcting member is a roll member.
According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the second curl correcting member is a belt member.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the bend preventing member also serves as a paper transport guide member.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first or fourth aspect, each of the first curl correction member and the second curl correction member is constituted by a through roll, and the warp prevention member. Is also a water vapor outflow prevention member.

  According to a sixth aspect of the present invention, there is provided a first curl correction member formed in a roll shape and disposed in a direction orthogonal to the paper transport direction, and a second curl correction softer than the first curl correction member. A curl correction device comprising: a member; and a deflection preventing member that prevents the first curl correction member from being bent when the first curl correction member is pressed against the second curl correction member. It is.

  According to the first to third aspects of the present invention, even when the paper curls in the fixing device, the curl correction device can correct the paper curl without generating wrinkles on the paper.

  According to the fourth aspect of the present invention, even when the first curl correcting member is constituted by a small-diameter roll, the bend preventing member is used between the first curl correcting member and the second curl correcting member. The paper can be surely guided to.

  According to the fifth aspect of the present invention, even when the first curl correcting member is constituted by a small-diameter roll, the outflow of water vapor can be effectively prevented by using the deflection preventing member.

  According to the sixth aspect of the present invention, it is possible to correct the curl of the paper without generating wrinkles on the paper.

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

  FIG. 1 is a schematic diagram showing a configuration example of an image forming apparatus to which the present invention is applied. The illustrated image forming apparatus 1 includes a receiving unit 5 connected to the image reading device 2 and an external device (such as a personal computer) 3 through a communication line 4, and an image writing unit based on image data received by the receiving unit 5. 6, an image recording control unit 7 that controls 6, a drum-shaped image carrier (photosensitive drum) 8 on which an electrostatic latent image is written by the image writing unit 6, and a circumferential direction of the image carrier 8. A charging device 9, a developing device 10, a cleaner 11, a roll-shaped transfer body (hereinafter referred to as “transfer roll”) 12 that transfers a toner image formed on the image holding body 8 to a paper, and a paper The fixing device 13 for fixing the transferred toner image, the curl correcting device 14 for correcting the curl of the paper while feeding the paper on which the toner image is fixed by the fixing device 13 to the downstream side in the transport direction, and the curl correcting device 1 The discharge roll pair 15 that discharges the sheet sent out by the apparatus, the discharge tray 16 that stores the sheet discharged by the discharge roll pair 15 in a stacked state, and the positions where the image carrier 8 and the transfer roll 12 are opposed to each other. The paper transport path 17 formed so that the paper passes through, the paper stacking tray 18 for storing paper used for image formation in a stacked state, and the paper stacked on the paper stacking tray 18 are supplied to the paper transport path 17. The paper supply unit 19 is provided. The image reading device 2 may exist as one functional unit of the image forming apparatus 1 or may exist as a functional unit separate from the image forming apparatus 1.

  The fixing device 13 is configured by using two rolls constituting a fixing roll pair, that is, a heating roll 21 and a pressure roll 22. The heating roll 21 and the pressure roll 22 are arranged in contact with each other at a predetermined pressure. The heating roll 21 and the pressure roll 22 are rotatably provided with one roll as a driving side and the other roll as a driven side. The heating roll 21 and the pressure roll 22 constituting the pair of fixing rolls feed the paper downstream in the transport direction by rotating with the paper sandwiched between the rolls.

  At that time, the heating roll 21 is disposed so as to contact the first surface of the paper, and the pressure roll 22 is disposed so as to contact the second surface of the paper. The first side and the second side of the paper are in a front-back relationship. The first surface of the paper is the surface of the paper on which the toner image is transferred when the paper passes between the image carrier 8 and the transfer roll 12 arranged on the upstream side of the fixing device 13 in the paper conveyance direction. (Image holding surface), and the opposite surface is the second surface (non-image holding surface) of the paper. The fixing of the toner image to the paper is performed by the heat applied to the paper by the heating roll 21 and the pressure applied to the paper by the pressure roll 22 when the paper passes between the heating roll 21 and the pressure roll 22 (contact portion). It is done using. For this reason, the contact portion between the heating roll 21 and the pressure roll 22 is a position where the fixing device 13 fixes the image on the paper.

  The curl correction device 14 is provided on the downstream side of the fixing device 13 in the sheet conveyance direction. In the paper transport direction, the fixing device 13 and the curl correction device 14 are arranged in a positional relationship adjacent to each other. For this reason, the paper on which the toner image is fixed by the fixing device 13 is immediately taken into the curl correction device 14 where the curl of the paper is corrected. Incidentally, in the paper transport method, various sizes of paper are used with one side (paper side edge) as a common reference in a direction (paper width direction) parallel to the paper transport surface and perpendicular to the paper transport direction. There are a side reference method for transporting and a center reference method for transporting paper of various sizes using the center of the paper as a common reference, but the present invention can be applied to an image forming apparatus employing any of the transport methods. However, in the embodiment of the present invention, it is assumed that the sheet is conveyed by the center reference method.

[First Embodiment]
2A and 2B show the configuration of the curl correction apparatus provided in the image forming apparatus according to the first embodiment of the present invention. FIG. 2A is a perspective view thereof, and FIG. 2B is a front view thereof. The curl correction device 14 is configured using a pair of curl correction rolls (hereinafter, also referred to as “curl correction roll pair”) 23 and 24 arranged in a direction orthogonal to the paper conveyance direction. The curl correcting roll pairs 23 and 24 rotate in the opposite directions while being in contact with each other with a predetermined force, thereby conveying the sheet 20 sandwiched between the two rolls to the downstream side in the conveying direction, while the sheet 20 20 curls are corrected.

  Of the two curl correction rolls (hereinafter simply referred to as “rolls”) 23 and 24 constituting the curl correction roll pair, one roll 23 is configured using, for example, a metal shaft having a circular cross section, and the other The roll 24 is configured using, for example, a rubber roll having a donut cross section. For this reason, if each roll 23 and 24 is distinguished by the difference in relative hardness, one roll 23 is constituted by a relatively hard roll and the other roll 24 is a relatively soft roll. It is configured. The roll 23 is disposed in contact with the first surface of the paper, and the roll 24 is disposed in contact with the second surface of the paper.

  The roll 24 is attached in a state in which the entire roll 24 is fitted to the shaft member 25 using a metal shaft having an outer diameter equivalent to that of the roll 23 as a shaft member 25. Thereby, the roll 24 and the shaft member 25 are configured to rotate integrally. The outer diameter of the roll 23 is set smaller than the outer diameter of the roll 24. Each of the rolls 23 and 24 is constituted by a through roll. The through roll is a roll roll having an outer diameter in the roll axial direction that is at least the minimum paper width handled by the image forming apparatus, preferably the maximum paper width W or more in the direction orthogonal to the paper conveyance direction (roll axis direction). It is a roll made constant (uniform).

  Further, both ends of the roll 23 are supported by bearing members 26 attached to the main body frame F1 of the image forming apparatus. Similarly, both ends of the shaft member 25 are supported by bearing members 27 attached to the main body frame F2 of the image forming apparatus. Thereby, the roll 23 is rotatably supported by the bearing member 26. The roll 24 and the shaft member 25 are rotatably supported by a bearing member 27.

  A gear 28 is attached to one end of the roll 23. The gear 28 rotates integrally with the roll 23 using a paper transport motor (not shown) as a drive source. The roll 23 is pressed against the roll 24 with a predetermined force. In the portion where the roll 23 is pressed (the contact portion between the rolls 23 and 24), the outer peripheral surface of the roll 24 is partially recessed due to the biting of the roll 23. For example, when the outer diameter of the roll 23 is “D1”, the outer diameter of the roll 24 is “D2”, and the distance between the rotation axes of the two rolls 23 and 24 is “L”, the pressing state between the two is L < It is obtained by setting the mounting positions of the bearing members 26 and 27 so as to satisfy the condition of (D1 / 2 + D2 / 2). The pressing force of the roll 23 against the roll 24 is set so that the roll 23 bites into the peripheral surface of the roll 24 by a predetermined amount so that a desired curl correction effect (curl correction force) is obtained.

  Further, the curl correcting device 14 is provided with a deflection preventing member 29. The deflection preventing member 29 is a block-shaped member having an arcuate recess corresponding to the outer peripheral shape of the roll 23, and is disposed at the center of the direction (roll axis direction) orthogonal to the paper transport direction. The deflection preventing member 29 is arranged in a state in contact with the roll 23 on the side opposite to the roll 24. For this reason, when viewed from the roll axial direction, the roll 23 is sandwiched between the deflection preventing member 29 and the roll 24 as shown in FIG. The deflection preventing member 29 is formed by pressing the roll 23 from one direction in the direction in which the roll 23 is pressed against the roll 24, thereby causing the roll 23 to be generated when the roll 23 is pressed against the roll 24 according to the setting of the distance L between the rotation axes described above. This prevents bending.

  A sliding portion 30 is provided at a contact portion (arc-shaped recess) of the deflection preventing member 29 with respect to the roll 23. The sliding portion 30 is formed integrally with the bending preventing member 29 by, for example, resin molding, and is configured by a resin (for example, fluororesin) having self-lubricating properties so that sliding resistance with the roll 23 is reduced. Has been. Further, the deflection preventing member 29 is configured to also serve as a paper transport guide member. Specifically, a paper guide surface 31 is formed integrally with the deflection preventing member 29 at the tip of the deflection preventing member 29 that contacts the roll 23. The paper guide surface 31 is formed in a state of being inclined obliquely toward the contact portion between the roll 23 and the roll 24 with respect to the paper transport path formed by the pair of paper transport path forming members 32A and 32B. When the leading edge of the paper transported along the pair of paper transport path forming members 32 </ b> A and 32 </ b> B contacts the paper guiding surface 31, the paper guiding surface 31 is moved to the contact portion between the roll 23 and the roll 24. It leads to.

  Next, the operation of the image forming apparatus having the above configuration will be described. First, the paper stored in the paper stacking tray 18 is supplied to the paper transport path 17 by the paper supply unit 19, and the paper is sent between the image carrier 8 and the transfer roll 12 (opposite position) through the paper transport path 17. As a result, the toner image formed on the image carrier 8 is transferred onto the paper by the transfer roll 12. Next, the image-transferred paper is sent to the fixing device 13. In the fixing device 13, the sheet is conveyed between the heating roll 21 and the pressure roll 22. Thereafter, the paper on which the image has been fixed is fed to the curl correction device 14 where the paper curl is corrected (removed), and then the paper is discharged to the discharge tray 16 through the discharge roll pair 15.

  At that time, in the curl correction device 14, the roll 23 is rotated by the driving force transmitted through the gear 28, and the roll 24 is also rotated in accordance with this rotation. In this state, as shown in FIG. 3, when the paper 20 passes between the rolls 23 and 24 (contact portion), the paper 20 is warped in the direction opposite to the curl caused by the fixing of the toner image. As a result, the curl correction device 14 removes the curl of the paper.

  Further, the roll 23 is prevented from being bent by pressing the roll 23 against the roll 24 side with the bending preventing member 29. For this reason, the whole roll 23 can be uniformly pressed against the roll 24 in the roll axis direction while keeping the roll 23 and the roll 24 in a parallel state. For this reason, wrinkles do not occur in the paper 20 passing between the rolls 23 and 24.

  Further, if each roll 23, 24 is constituted by a roll and the outer diameter of the roll 23 is reduced in order to obtain a predetermined amount of biting (curl correction effect), the pair of paper transport path forming members 43A, 32B alone is sufficient. It becomes difficult to guide the leading edge of the sheet between the rolls 23 and 24 (contact portion). In contrast, in the first embodiment of the present invention, the paper guide surface 30 is formed at the tip of the deflection preventing member 29, and the paper guide surface 30 is used to place the paper tip between the rolls 23 and 24 (contact). Part). Therefore, when viewed from the roll axis direction, a wedge shape is formed by the paper guide surface 31 of the deflection preventing member 29 and the outer peripheral surface of the roll 24 on the large diameter side, and the leading edge of the paper is used by utilizing this wedge shape. It can be reliably guided between the rolls 23 and 24.

  Further, since the resin sliding portion 30 is formed at the tip of the deflection preventing member 29 and this sliding portion 30 is brought into contact with the outer peripheral surface of the roll 23, the deflection preventing member 29 strongly presses the roll 23. However, the outer peripheral surface of the roll 23 is hardly damaged. Further, since the sheet is sent out with high heat in the fixing device 13, if the roll 23 is formed of a metal shaft, the surface temperature of the roll 23 becomes high due to the influence of heat transmitted from the sheet after fixing. For this reason, when the deflection preventing member 29 is brought into contact with the roll 23, the heat of the roll 23 is taken away and temperature unevenness occurs in the roll axis direction, which may adversely affect the image on the sheet. On the other hand, when the sliding portion 30 of the deflection preventing member 29 is made of resin, the heat transfer from the roll 23 to the deflection preventing member 29 is less than when the portion is made of metal or the like. . For this reason, the temperature nonuniformity of the roll 23 can be suppressed.

  In the first embodiment, a sliding portion 30 made of a self-lubricating resin is provided at the tip of the deflection preventing member 29, and the sliding portion 30 is brought into contact with the outer peripheral surface of the roll 23. In addition to this, as shown in FIG. 4, for example, a plurality of minute convex portions are provided on the concave surface of the sliding portion 30 along the outer peripheral surface of the roll 23. By making this convex part contact the outer peripheral surface of the roll 23, the contact area of the sliding part 30 with respect to the roll 23 can be reduced, and both sliding resistance can be lowered | hung.

  In addition, as shown in FIG. 5, an appropriate number of ball bearings 33 are incorporated at the tip of the deflection preventing member 29 in place of the sliding portion 30, and the ball bearing 33 is brought into contact with the outer peripheral surface of the roll 23, thereby 23 can be smoothly rotated.

  In the first embodiment, the roll 23 is held at the center portion in the roll axis direction by pressing the anti-bending member 29. However, other than this, for example, an equal distance is separated from the center portion in the roll axis direction. Two bend prevention members may be provided at the positions, and the roll 23 may be pressed by these two bend prevention members. Furthermore, the number of the deflection preventing members may be three or more.

[Second Embodiment]
6A and 6B show a configuration of a curl correction apparatus provided in an image forming apparatus according to the second embodiment of the present invention, in which FIG. 6A is a perspective view thereof and FIG. 6B is a front view thereof. The second embodiment is characterized in that, in particular, the deflection preventing member 29 also serves as a water vapor outflow preventing member, as compared with the first embodiment. Specifically, in the direction orthogonal to the sheet conveyance direction, the width of the deflection preventing member 29 is set to a dimension equal to or larger than the minimum sheet width handled by the image forming apparatus, more preferably to a dimension equal to or larger than the maximum sheet width W handled by the image forming apparatus. It is set.

  In the paper conveyance path from the fixing device 13 to the curl correction device 14, water vapor is generated by the conveyance of the paper. This is because water contained in the paper before the image is fixed is heated by the fixing device 13 to generate water vapor from the paper on which the image has been fixed. When the moisture generated in this way flows out downstream of the curl correction device 14 in the transport direction, it is necessary to take measures against condensation at a plurality of locations on the downstream side. In particular, when the outer diameter of the roll 23 is reduced, even if the two rolls 23 and 24 constituting the curl correction roll pair are both configured as a roll to prevent the outflow of water vapor, the steam passes over the small diameter roll 23 and the water vapor It tends to flow out downstream.

  On the other hand, since the deflection preventing member 29 serves as a barrier for stopping the flow of water vapor in the sheet conveyance direction, if the width of the deflection prevention member 29 is set as described above, the upstream side of the curl correction device 14 in the sheet conveyance direction. The flow of water vapor generated in step S3 can be blocked by the deflection preventing member 29 over the entire area of the minimum paper width handled by the image forming apparatus, more preferably over the entire area of the maximum paper width W. For this reason, it is possible to effectively prevent the water vapor from getting over the roll 23 and flowing out to the downstream side in the paper transport direction. As a result, dew condensation measures can be taken collectively on the upstream side of the curl correction device 14.

  Further, by arranging the bending prevention member 29 wide as described above, the paper guide surface 31 of the bending prevention member 29 is also arranged wide. For this reason, even when the sheet is conveyed with a slight inclination, the leading end of the sheet can be reliably guided between the rolls 23 and 24.

  Further, as shown in FIG. 7, a sliding portion 30 made of a self-lubricating resin is provided at the distal end portion of the deflection preventing member 29, and the sliding portion 30 is brought into contact with the outer peripheral surface of the roll 23. 23 can be rotated without any problem.

  Further, as shown in FIG. 8, a plurality of minute convex portions are provided on the concave surface of the sliding portion 30 along the outer peripheral surface of the roll 23, and these convex portions are brought into contact with the outer peripheral surface of the roll 23. It is possible to reduce the contact area of the sliding portion 30 with respect to the sliding resistance of the both.

  Further, as shown in FIG. 9, an appropriate number of ball bearings 33 are incorporated in the distal end portion of the deflection preventing member 29 in place of the sliding portion 30, and the ball bearing 33 is brought into contact with the outer peripheral surface of the roll 23, thereby 23 can be smoothly rotated.

  In the above embodiment, the curl correction device 14 having a configuration in which the hard roll 23 made of a metal shaft or the like is pressed against the soft roll 24 having a larger diameter than the roll 23 has been described as an example. However, the present invention is not limited to this. For example, although not shown, the small-diameter and hard roll 23 is wound around a roll having an outer diameter equal to or greater than that of the roll 23 as described above. The present invention can also be applied to a curl straightening device configured to be pressed against a soft belt member.

1 is a schematic diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied. 1 is a diagram illustrating a configuration of a curl correction device included in an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the 1st structural example of the KK arrow cross section of FIG. It is a figure which shows the 2nd structural example of the KK arrow cross section of FIG. It is a figure which shows the 3rd structural example of the KK arrow cross section of FIG. It is a figure which shows the structure of the curl correction apparatus with which the image forming apparatus which concerns on 2nd Embodiment of this invention is provided. It is a figure which shows the 1st structural example of the JJ arrow cross section of FIG. It is a figure which shows the 2nd structural example of the JJ arrow cross section of FIG. It is a figure which shows the 3rd structural example of the JJ arrow cross section of FIG. It is a figure explaining the main subjects of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 13 ... Fixing apparatus, 14 ... Curl correction apparatus, 20 ... Paper, 23, 24 ... Curl correction roll, 31 ... Paper guide surface

Claims (6)

A fixing device that fixes an image on paper using at least heat;
A curl correction device provided on the downstream side of the fixing device in the paper conveyance direction to correct the curl of the paper,
The curl correction device includes a first curl correction member formed in a roll shape and arranged in a direction orthogonal to a paper conveyance direction, a second curl correction member softer than the first curl correction member, An image forming apparatus, comprising: a deflection preventing member that prevents deflection of the first curl correcting member when the first curl correcting member is pressed against the second curl correcting member. The image forming apparatus according to claim 1, wherein the second curl correcting member is a roll member. The image forming apparatus according to claim 1, wherein the second curl correcting member is a belt member. The image forming apparatus according to claim 1, wherein the deflection preventing member also serves as a sheet conveyance guide member. The first curl correction member and the second curl correction member are both constituted by threading rolls,
The image forming apparatus according to claim 1, wherein the deflection preventing member also serves as a water vapor outflow preventing member. A first curl correction member formed in a roll shape and disposed in a direction orthogonal to the paper conveyance direction;
A second curl correction member that is softer than the first curl correction member;
A curl correction device, comprising: a deflection preventing member that prevents deflection generated in the first curl correction member when the first curl correction member is pressed against the second curl correction member.

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