JP2005035731A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for surely correcting curl of a recording medium in forming an image on its second side. <P>SOLUTION: An inverting unit 24 includes a pair of curl correcting rolls 32 each constituted of a shaft 44 and a soft nip roll 46. The soft nip roll 46 is constituted of a shaft member and a soft member through which the shaft member is inserted. The soft member 72 locally dents at a contact part 32T of the soft material 72 and the shaft 44 to correct the curl of a sheet S of a recording paper. Since the inverting unit 24 includes a pair of the curl correcting rolls 30, the correction of the curl is performed to a direction advantageous for peeling the sheet S from a second intermediate transfer roll 38 and a final transfer roll 42 after the transfer of the image on the second side of the sheet S. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of forming an image on a second surface by inverting the recording medium after forming an image on a first surface of the recording medium.

  In an image forming apparatus that forms a toner image on a recording medium by a so-called electrostatic recording method, the recording medium may be curled when the toner image is fixed on the recording medium. When a curled recording medium is conveyed in the image forming apparatus, a paper jam (so-called “jam”) may occur. In particular, in the case of an image forming apparatus of a type (double-sided printing) in which an image is formed on the first side after being formed on the first side of the recording medium, the image is formed on the second side. Due to curling, a paper jam may occur when the recording medium after reversal is conveyed.

  In Patent Document 1, in order to correct such a curl, as shown in FIG. 6, fixing rollers 202A and 202B are used as a first conveying roller, and a second conveying roller is provided immediately after the first conveying rollers 202A and 202B. A curl straightening device that includes 204A and 204B to correct curl is described.

However, in the configuration shown in FIG. 6, since the second conveyance rollers 204A and 204B for curl correction are provided immediately after the first conveyance rollers 202A and 202B, that is, before the path for reversing the recording medium, Even when the image formation is not performed on the second surface of the recording medium on which the image is formed on the first surface, the curl is corrected in the same manner as when the image formation is performed on the second surface. In other words, considering only the case where an image is formed on the second surface, accurate curl correction may not be possible.
JP 63-218462 A

  In view of the above facts, an object of the present invention is to obtain an image forming apparatus that can reliably correct curl of a recording medium when an image is formed on a second surface.

  According to the first aspect of the present invention, an image is formed on the first surface by a conveying unit that conveys the recording medium, an image forming unit that forms an image on the recording medium conveyed by the conveying unit, and the image forming unit. The reversing means for reversing the recording medium and sending it to the image forming means so that an image is formed on the second surface; And a curl correcting means for correcting the curl of the recording medium.

  The recording medium is imaged on the first surface by the image forming means while being conveyed by the conveying means. When the image is not formed on the second surface, the recording medium is discharged as it is, but when the image is formed on the second surface, the reversing unit reverses the recording medium and sends it to the image forming unit.

  Here, a curl correction unit is provided in the conveyance path from when the recording medium is reversed by the reversing unit until an image is formed on the second surface, and the curl of the recording medium is corrected. That is, this curl correcting means works only when an image is formed on the second surface, and can reliably correct the curl of the recording medium in consideration of the image formation on the second surface.

  According to a second aspect of the present invention, in the first aspect of the invention, the curl correction means is pressed against the high-rigidity roll disposed in a direction perpendicular to the conveyance direction of the recording medium, and the high-rigidity roll. A nip roll that is locally recessed and nips a recording medium with a high-rigidity roll, and a drive unit that rotationally drives the nip roll, are characterized by being configured.

  Therefore, the recording medium is conveyed while being nipped (nip) between the high-rigidity roll and the nip roll, and the curl is corrected by the local dent of the nip roll. Since the nip roll is rotationally driven by the driving means, the curl of the recording medium can be corrected without being affected by other members or the like as compared with the configuration in which the high-rigidity roll is rotationally driven.

  The “high-rigidity roll” referred to here only needs to have a higher rigidity than the nip roll and can dent the nip roll locally. For example, it can be made of metal or hard resin.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the reversing unit is provided, and the reversing unit is detachable from the apparatus main body. It is provided in the reversing unit.

  Since the reversing unit is provided in the reversing unit, an image can be formed on the second surface of the recording medium simply by mounting the reversing unit on the apparatus main body. Since the reversing unit is also provided with a curl correcting means, the reversing unit is mounted on the apparatus main body, so that it is possible to correct the curl of the recording medium when an image is formed on the second surface.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the curl correcting means is disposed in an upstream end in the recording medium conveying direction in the reversing unit.

  In this way, by arranging the curl correcting means upstream in the reversing unit, the curl can be corrected at a short timing after the reversal of the recording medium.

  According to a fifth aspect of the invention, in the third or fourth aspect of the invention, at least a part of the reversing unit can be opened and closed in the reversing unit, and the recording medium can be removed outside in the open state. The curl correcting means is disposed at a position where the medium removing cover is visible from the outside with the medium removing cover open.

  Therefore, the medium removal cover can be opened to visually check the curl correcting means, and inspection can be performed. It is also possible to remove the recording medium from the reversing unit.

  According to a sixth aspect of the present invention, in the fifth aspect of the invention, there is provided an interlocking mechanism that releases the nip between the high-rigidity roll and the nip roll in conjunction with the movement of the medium removal cover to the open position. It is characterized by that.

  Thus, the nip between the high-rigidity roll and the nip roll is released simply by moving the medium removal cover to the open position, so that the recording medium can be easily removed.

  According to a seventh aspect of the invention, in the fifth aspect of the invention, there is provided stopper means for preventing the movement of the medium removal cover to the closed position when the medium removal cover is in the open position. .

  That is, the medium removal cover is not moved carelessly to the closed position by the stopper means in the open position, and the workability such as removal of the recording medium is improved. If the movement prevention by the stoper is released, the medium removal cover can be moved to the closed position.

  Since the present invention has the above-described configuration, the curl of the recording medium can be reliably corrected when an image is formed on the second surface.

  FIG. 1 shows an image forming apparatus 10 according to the first embodiment of the present invention. The image forming apparatus 10 according to the present embodiment forms a toner image on a sheet (recording medium) by a so-called electrostatic recording method to obtain a desired image. Here, a tandem type full-color image corresponding to four colors is used. A forming device is mentioned.

  The image forming apparatus 10 is roughly divided into an image forming unit 12, a transfer unit 14, a fixing unit 16, a paper feeding unit 18, and a paper discharging unit 20, which are arranged in a housing 22. ing.

  The image forming unit 12 includes an exposure device 26 that emits laser beams R (Y) to (K) of colors of yellow (Y), magenta (M), cyan (C), and black (K). is doing. Although not shown, a laser beam R corresponding to each color is emitted to each of the four photosensitive drums 28 uniformly charged by the charger, and an electrostatic latent image is written. Thereafter, toner is supplied from a developing device (not shown), and a toner image is formed on the photosensitive drum 28.

  The transfer unit 14 includes first intermediate transfer rolls 36 </ b> A and 36 </ b> B, a second intermediate transfer roll 38, and a final transfer roll 42.

  The first intermediate transfer rolls 36A and 36B primarily transfer the toner image from the photosensitive drum 28 while rotating counterclockwise. The second intermediate transfer roll 38 secondarily transfers the toner image from the first intermediate transfer rolls 36A and 36B. The final transfer roll 42 can be conveyed while sandwiching the recording paper S between the second intermediate transfer roll 38 and transfers the toner image carried on the second intermediate transfer roll 38 to the recording paper S. .

  The paper feed unit 18 is formed along the transport path W of the recording paper S from the paper feed tray 50 to the discharge tray 52. A plurality of recording sheets S are accommodated in the paper feed tray 50. From the paper feed tray 50 to the downstream side in the transport direction of the transport path W, a roll pair of a pick-up roll 54A and a retard roll 54B, and a transport roll in order. A pair 55 and a resist roll pair 56 are provided. The recording sheet S is sandwiched between the respective roll pairs and conveyed downstream in the conveyance direction of the conveyance path W.

  The fixing unit 16 is located downstream of the final transfer roll 42 in the transport direction of the transport path W, and includes a heating roll 62, a pressure roll 64, and a transport roll pair 66.

  The paper discharge unit 20 includes discharge roll pairs 57 and 58, and the recording paper S sandwiched and conveyed by these roll pairs is discharged onto the discharge tray 52.

  The discharge roll pairs 57 and 58 can be reversed. When the rear end of the recording paper S is positioned between the transport roll pair 66 and the discharge roll pair 57, the recording paper S is reversed. Can be transported.

  A reversing unit 24 is detachably attached to the side surface of the housing 22. The recording sheet S conveyed in the reverse direction by the reversal of the discharge roll pairs 57 and 58 enters the upper part of the reversing unit 24.

  In the reversing unit 24, a transport roll pair 30, a curl correction roll pair 32, and a transport roll pair 34 are arranged in this order from the top (that is, upstream in the transport direction of the recording paper S in the reversing unit 24).

  As shown in FIG. 2, the curl correction roll pair 32 includes a shaft 44 and a soft nip roll 46. The shaft 44 is made of metal, is disposed in a direction orthogonal to the conveyance direction of the recording paper S, and is rotatably supported by a bearing (not shown).

  The soft nip roll 46 includes a shaft member 70 and a plurality of soft members 72 arranged at predetermined intervals in the longitudinal direction of the shaft member 70 (in this embodiment, the recording sheet S is a so-called “center”. The three soft members 72 are arranged on the object with reference to the center in consideration of being conveyed at the “register”. As can be seen from FIG. 2A, the soft member 72 of the soft nip roll 46 is pressed against the metal shaft 44, whereby the soft member 72 is locally recessed at the contact portion 32T. The recording paper S is conveyed while being pinched by the recessed contact portion 32T, and the curling of the recording paper S is corrected. In particular, the curl of the recording paper S can be more effectively corrected by applying a pinching force that is higher than the pinching force of another pair of transport rolls. In consideration of the fact that the shaft 44 bites and dents in this way, the soft member 72 has a larger diameter than the rolls constituting the other pair of conveyance rolls, so that the conveyance speed does not vary. Has been.

  The shaft member 70 is rotatably supported by a bearing (not shown) and is rotated by receiving a driving force from the motor 60.

  As can be seen from FIG. 2A, when the soft member 72 is pushed into the shaft 44, the center of the shaft 44 is slightly curved in a direction away from the soft nip roll 46. Accordingly, when considering the radius of the soft member 72 at the portion where the soft member 72 is in contact with the shaft 44, the sandwiching portion radius R1 (see FIG. 2B) at the central soft member 72 is the softness at both ends. It is longer than the clamping portion radius R2 (see FIG. 2C) of the member 72. As a result, the transport speed of the recording paper S at the center in the width direction H becomes faster than the transport speed of both ends, and the force indicated by the arrow F in FIG.

  As shown in FIG. 1, the reversing unit 24 is provided with a medium removal cover 74. The medium removal cover 74 is rotated by a hinge (not shown), and moves between a closed position indicated by a solid line in FIG. 1 and an open position indicated by a two-dot chain line. In the open position, the curl correction roll pair 32 can be visually recognized from the outside. In the closed position, it is locked by a lock member (not shown) and does not move to the open position carelessly.

  The reversing unit 24 is provided with a release lever 76. The release lever 76 is rotatable about the vicinity of the upper end (fixed end), and is urged to rotate so that the lower end (rotating end) side protrudes from the reversing unit 24 by a compression coil spring 78 provided in the reversing unit 24. ing. As shown by the solid line in FIG. 1, when the medium removal cover 74 is locked in the closed position, the release lever 76 is pushed by the medium removal cover 74 and receives the urging force of the compression coil spring 78. Inadvertently, the lower end does not protrude from the reversing unit 24. On the other hand, as shown by the two-dot chain line, when the medium removal cover 74 is in the open position, the release lever 76 is rotated by the urging force of the compression coil spring 78 and its lower end protrudes from the reversing unit 24. Even if the medium removal cover 74 is moved in the closing direction in this state, it cannot be moved by the release lever 76. If the user rotates the release lever 76 and moves it to a position (a position indicated by a solid line) where the release lever 76 does not hit, the medium removal cover 74 can be moved to the closed position.

  In the housing 22, there are provided a pair of conveyance rolls 48 for conveying the recording paper S that has entered again from the reversing unit 24 and the recording paper S that has entered from an external tray (so-called “manual feed tray” or the like). .

  In the image forming apparatus 10 of the present embodiment having such a configuration, the toner image formed on the photosensitive drum 28 by the image forming unit 12 is transferred to the first surface of the recording paper S by the transfer unit 14, and Fixing is performed by the fixing unit 16. When an image is not formed on the second surface, the discharge roll pairs 57 and 58 of the paper discharge unit 20 rotate forward, and the recording paper S is discharged to the discharge tray 52.

  When an image is also recorded on the second surface of the recording paper S, when the trailing edge of the recording paper S is positioned between the transport roll pair 66 and the discharge roll pair 57, the discharge roll pairs 57 and 58 are reversed. Then, the recording paper S is conveyed in the reverse direction. Here, the leading edge of the recording sheet S when it is conveyed in the reverse direction is lifted by the elasticity (so-called “koshi”) of the recording sheet S and enters the reversing unit 24.

  In the reversing unit 24, the recording paper S is transported by the transport roll pair 30 and is transported by the rotation of the soft nip roll 46 while being sandwiched between the shaft 44 and the soft nip roll 46 constituting the curl correction roll pair 32. At this time, the recording paper S is curled and corrected by the contact portion 32T between the shaft 44 and the soft nip roll 46. The direction of curl correction is an advantageous direction for peeling from the second intermediate transfer roll 38 and the final transfer roll 42 after image transfer to the second surface. In particular, the pinching force between the shaft 44 and the soft nip roll 46 is higher than the pinching force of the other conveyance roll pairs, and the curling of the recording paper S can be corrected more effectively.

  Further, as can be seen from FIGS. 2B and 2C, since the sandwiching portion radius R1 at the central soft member 72 is longer than the sandwiching portion radius R2 at the soft members 72 at both ends, the width of the recording sheet S is increased. The transport speed at the center in the direction becomes faster than the transport speed at both ends, and the force indicated by the arrow F in FIG. That is, since the recording sheet S is conveyed while being slightly pulled in the sheet width direction (arrow H direction), the recording sheet S is prevented from being wrinkled or loosened.

  The recording paper S corrected in curl in this way is further transported by the transport roll pair 34 and enters the housing 22 again. Thereafter, the toner image is transferred to the second surface of the recording paper S by the transfer unit 14 in the same manner as the image formation on the first surface by the transport rollers 48 and 55. In the reversing unit 24, the recording paper S has been curled in a direction advantageous for peeling from the second intermediate transfer roll 38 and the final transfer roll 42 after image transfer to the second surface, so that the recording paper S is reliably peeled off. . Then, the toner image on the second surface is fixed by the fixing unit 16, and the discharge tray 52 is discharged by normal rotation of the discharge roll pairs 57 and 58 of the paper discharge unit 20.

  When a paper jam occurs in the reversing unit 24, the jammed recording paper S can be easily removed by moving the medium removal cover 74 to the open position as shown by a two-dot chain line in FIG. When the medium removal cover 74 is in the open position, even if the medium removal cover 74 is to be moved in the closing direction, it contacts the lower end of the release lever 76 rotated by the biasing force of the compression coil spring 78 and moves in the closing direction. I can't. As a result, it is possible to prevent an operation error in which image formation is performed with the medium removal cover 74 opened. When the user turns the release lever 76 to move it to a position where the medium removal cover 74 does not hit, and moves the medium removal cover 74 to the closed position, the release lever 76 is locked by a lock member (not shown). Image formation is possible.

  Thus, in this embodiment, since the curl correction roll pair 30 is provided in the reversing unit 24, the second intermediate transfer roll 38 and the final transfer roll 42 after the image transfer onto the second surface of the recording paper S in particular. The curl can be corrected in a direction advantageous for peeling.

  FIG. 4 shows an image forming apparatus 120 according to the second embodiment of the present invention. In this image forming apparatus 120, the shaft 44 constituting the curl correction roll pair 32 is slightly movable in a direction away from the soft nip roll 46 (the shaft 44 at the moved position is shown by a two-dot chain line in FIG. The reversing unit 24 is provided with a swing link 124 above the curl correction roll pair 32 instead of the release lever 76. The overall configuration other than these is the same as that of the image forming apparatus 10 of the first embodiment.

  The swing link 124 is pivotally supported substantially at the center, and is urged to rotate in the direction in which the lower end side is separated from the shaft 44 (the direction toward the posture shown by the solid line in FIG. 4) by the compression coil spring 122. On the other hand, when the medium removal cover 74 is in the closed position, the upper portion is pushed by the pressing protrusion 126 provided on the medium removal cover 74, so that the compression coil spring 122 resists the urging force and moves to the position indicated by the solid line. Is rotated. As a result, the lower portion of the swing link 124 presses the shaft 44 in a direction approaching the soft nip roll 46, and therefore, as in the first embodiment, the contact portion 32T between the shaft 44 and the soft member 72 (FIG. 2 ( In (A), the recording paper S can be conveyed while curling.

  When the medium removal cover 74 is moved to the open position, the pressing projection 126 moves away from the swing link 124, so that the swing link 124 receives the urging force of the compression coil spring 122 and moves to the position indicated by the two-dot chain line in FIG. And the shaft 44 moves away from the soft nip roll 46. Therefore, for example, the recording sheet S in which the shaft 44 is sandwiched between the soft nip roll 46 can be easily removed.

  FIG. 5 shows an image forming apparatus 130 according to the third embodiment of the present invention. In the third embodiment, the shaft 44 is not separated from the soft nip roll 46, but the soft nip roll 46 is movable in a direction away from the shaft 44, and the approach direction (in FIG. (Right direction). Moreover, it replaces with the rocking | fluctuation link 124 of 2nd Embodiment, and the link mechanism 134 comprised by two links (1st link 134A and 2nd link 134B) is provided. Other than this, the configuration is the same as that of the second embodiment.

  The first link 134A constituting the link mechanism 134 is pivotally supported around one end, and one end of the second link 134B is pivotally supported on the other end (rotating end) side. The other end of the link 134B is pivotally supported by the medium removal cover 74. When the medium removal cover 74 is in the closed position, the first link 134A is separated from the shaft member 70, so the soft nip roll 46 is pushed by the spring 132 and approaches the shaft 44, and the contact portion between the shaft 44 and the soft member 72 At 32T (see FIG. 2A), the recording sheet S can be conveyed while curling.

  When the medium removal cover is moved to the open position, the first link 134A rotates together with the second link 134B, and the first link 134A presses the shaft member 70 to separate the soft nip roll 46 from the shaft 44. Therefore, for example, the recording sheet S in which the shaft 44 is sandwiched between the soft nip roll 46 can be easily removed.

  As described above, in the second and third embodiments, the nipping of the recording sheet S by the shaft 44 and the soft nip roll 46 is released in conjunction with the operation of moving the medium removal cover 74 to the open position. ing. That is, the recording paper S can be easily removed by simply opening the medium removal cover 74.

  In each of the above-described embodiments, the curl correction roll pair 32 is disposed in the reversing unit 24 approximately in the middle of the conveyance path of the recording paper S. However, the position of the curl correction roll pair 32 is the reversing unit 24. If it is in, it will not specifically limit, The position of another member etc. can also be considered and it can arrange | position in the optimal position. In particular, it is preferable to arrange the reversing unit 24 on the upstream side in the transport direction because the curling of the recording paper S can be corrected at an earlier stage and the possibility of subsequent paper jams can be reduced.

  In the above description, the image forming apparatus of the present invention is a full-color image forming apparatus. However, an image forming apparatus that forms an image using a single color toner may be used.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. The curl correction roll pair of 1st Embodiment of this invention is shown, (A) is a plane nest, (B) is the II sectional view taken on the line of (A), (C) is the II-II sectional view of (A). FIG. It is a front view which shows the curl correction roll pair of 1st Embodiment of this invention from the soft nip roll side. It is sectional drawing which shows schematic structure of the image forming apparatus of 2nd Embodiment of this invention. It is sectional drawing which shows schematic structure of the image forming apparatus of 3rd Embodiment of this invention. It is a side view which shows the curl correction apparatus of the conventional sheet material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming part 14 Transfer part (Image forming means)
16 Fixing unit 18 Paper feeding unit (conveying means)
20 Paper discharge unit (conveyance means)
24 reversing unit 30 conveyance roll pair 32 curl correction roll pair (curl correction means)
32T Contact part 34 Conveying roll pair 44 Shaft (High rigidity roll)
46 Soft nip roll (nip roll)
60 motor (drive means)
70 Shaft member 72 Soft member 74 Medium removal cover 76 Release lever (stopper means)
78 Compression coil spring 120 Image forming apparatus 122 Compression coil spring 124 Swing link (interlocking mechanism)
126 Pressing projection 130 Image forming apparatus 132 Spring 134 Link mechanism (interlocking mechanism)
R Laser beam S Recording paper W Transport path

Claims (7)

Conveying means for conveying the recording medium;
Image forming means for forming an image on a recording medium conveyed by the conveying means;
Reversing means for reversing the recording medium on which the image is formed on the first surface by the image forming means and sending it to the image forming means so as to form an image on the second surface;
A curl correcting unit that is provided in a conveyance path from when the recording medium is reversed by the reversing unit to when an image is formed on the second surface of the recording medium;
An image forming apparatus comprising: The curl correcting means is a high-rigidity roll arranged in a direction orthogonal to the recording medium conveyance direction;
A nip roll that is pressed against the high-rigidity roll to locally dent and nip a recording medium with the high-rigidity roll;
Drive means for rotationally driving the nip roll;
The image forming apparatus according to claim 1, further comprising: A reversing unit provided with the reversing means and detachable from the apparatus main body;
The image forming apparatus according to claim 1, wherein the curl correcting unit is provided in the reversing unit.   The image forming apparatus according to claim 3, wherein the curl correcting unit is disposed at an upstream end in the recording medium conveyance direction in the reversing unit. The reversing unit is provided with a medium removal cover that can open and close at least a part of the reversing unit, and that can remove the recording medium to the outside in the open state.
5. The image forming apparatus according to claim 3, wherein the curl correcting unit is disposed at a position that is visible from the outside with the medium removal cover open.   The image forming apparatus according to claim 5, further comprising an interlocking mechanism that releases a nip between the high-rigidity roll and the nip roll in conjunction with the movement of the medium removal cover to the open position. Stopper means for preventing movement of the medium removal cover to the closed position when the medium removal cover is in the open position;
The image forming apparatus according to claim 5, further comprising:

Images