JP2009107821A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent paper from being caught in switching back by preventing hanging of a paper trailing end. <P>SOLUTION: The image forming apparatus comprises discharging conveying passages 12A, 12B, 12C having discharging rollers 16, 17 near a terminal portion 14, forming paper P0 on which an image is formed in a bent state and leading it to the discharging rollers to discharge it; a returning conveying passage 12D connecting an inlet side end to a first position which is on the upstream of the discharging roller of the discharging conveying passage 12C and on the downstream of a fixing portion 11 and an outlet side end to a second position which is on the upstream of a transfer portion 10 of the discharging conveying passage 12A, changing the bent paper supported by the discharging roller to be in a stretched state, returning the paper from the inlet side end to the discharging conveying passage 12A through the outlet side end by reverse rotations of the discharging roller, and having a posture changing passage 12D-1 changing a posture of the paper from the bent state to the stretched state at a part of the inlet side end; and a flexible member 21 provided in the posture changing passage 12D-1, permitting the paper to get in the bent state, and having stiffness for pushing up the trailing end of the paper. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus capable of forming an image on both sides of a sheet.

  In the image forming apparatus described above, after image formation is performed on one side of a sheet, image formation is performed on both sides by performing image formation on the other side. In such image formation, when image formation is performed on one side of a sheet, the other side switches back the sheet before image formation and reverses the front and back surfaces to return to the image forming unit.

Specifically, as shown in FIG. 5, the paper P0 stored in the paper feed cassette 101 is sent to the transfer unit 102 through the discharge conveyance path 100A to form an image, and then is discharged through the discharge conveyance path 100B. The image is sent to the fixing unit 103 to fix the image, and then sent to the discharge unit 104 having the discharge rollers 104a and 104b through the discharge conveyance path 100C. Here, a part of the front side of the paper P0 protrudes outward, and the paper P0 The rear end is pulled out from the branch lever 105, and then returned to the return conveyance path 100D. The rear end up to that point is returned to the front end, and then sent back to the discharge conveyance path 100A. Are reversed, and discharged from the discharge unit 104 to the outside through the transfer unit 102 and the fixing unit 103 (see, for example, Patent Document 1).
JP 2006-62855 A

  By the way, the switchback is performed by rotating the discharge rollers 104a and 104b in reverse. Since there is no support for the paper P0 from the discharge rollers 104a and 104b to the rear end of the paper P0, the rear end of the paper P0 hangs down and does not go to the transport path 100D. When the discharge rollers 104a and 104b are reversely rotated and switched back as described above, there is a problem in that the paper is caught by returning to the discharge conveyance path 100B instead of the return conveyance path 100D.

  The present invention has been made to solve the above-described problems of the prior art, and provides an image forming apparatus capable of preventing the trailing edge of the sheet from sagging and preventing the sheet from being caught during switchback. With the goal.

  The image forming apparatus according to claim 1 of the present invention selects one of the one side and both sides of the paper, forms the image on the selected one side or both sides through the transfer portion and the fixing portion in this order, and then from the discharge roller. An image forming apparatus for discharging a sheet to the outside, having the discharge roller in the vicinity of a terminal position while passing through the transfer unit and the fixing unit, and bending the sheet on which the image is formed to the discharge roller. And a discharge conveyance path for discharging the paper from the discharge roller to the outside in a substantially horizontal direction, and a first position upstream of the discharge roller of the discharge conveyance path and downstream of the fixing unit. The discharge end roller is connected to the second position upstream of the transfer portion of the discharge conveyance path, and the bent end sheet supported by the discharge roller is changed to the extended state. By reverse rotation The sheet is returned from the entry-side end to the discharge conveyance path via the exit-side end, and the attitude change path for changing the attitude of the sheet from the bent state to the extended state at the entry-side end portion. The return conveyance path that is shared with the discharge conveyance path, and the posture changing path are provided so as to contact the lower surface of the sheet, permitting the sheet to be bent, and pushing up the rear end of the sheet to form the sheet A flexible member having a waist that can be held in the stretched state, and when forming an image on one side, the sheet is discharged to the outside through a discharge conveyance path, and an image is formed on both sides. Is characterized in that after being guided to the discharge roller through the discharge conveyance path, the discharge roller is reversely rotated to switch back to the return conveyance path and then discharged to the outside from the discharge conveyance path.

  An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the waisted flexible member is made of a resin film.

  An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first or second aspect, wherein a rear end of the sheet conveyed on the discharge conveying path enters the posture changing path. It is characterized by comprising a rear end detecting means for detecting and temporarily stopping the rotation of the discharge roller based on the detection.

  According to the present invention, when images are formed on both sides of a sheet, when the trailing edge of the sheet enters the posture change path and stops, the bent sheet changes to an expanded state, but the trailing edge of the sheet is supported. Even if it is easy to sag, the flexible member with a waist contacts the lower surface of the paper and pushes up the rear end of the paper to hold it in an extended state, thereby preventing the rear end of the paper from sagging. This makes it possible to reliably return the paper to the transport path during switchback, and prevent the paper from being caught. In addition, when forming an image on one side of the paper, when the paper is supplied to the discharge roller via the discharge conveyance path, a flexible member having a waist crosses the conveyance area of the paper, Since the flexible member is bent by the sheet conveyed through the discharge conveyance path, the sheet conveyance is allowed and is not disturbed.

  In the case of the invention of claim 2, since the flexible member having a waist is formed with a commercially available resin film, an inexpensive configuration can be obtained.

  According to the third aspect of the present invention, since the trailing edge detecting means is provided, the sheet is changed from the bent state to the extended state and stopped regardless of the size of the sheet. Therefore, it is possible to reliably return the paper to the transport path regardless of the paper size.

  The present invention will be specifically described below. In the present embodiment, the case where the image forming apparatus is a copying machine will be described. However, the present invention is not limited to this, and may be a printer, a facsimile, or the like.

  FIG. 1 is a schematic front view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus 1 is arranged on the upper part of the image forming apparatus 1 and forms an image on a sheet P0 based on a reading unit 2 for reading a document image and image data obtained by the reading unit 2 according to the document image. An image forming unit 3 that performs sheet feeding, a sheet feeding unit 4 that feeds the sheet P0 to the image forming unit 3, a sheet feeding unit 5 that transports the sheet P0 from the sheet feeding unit 4 through the image forming unit 3 to the outside of the apparatus, And a control unit 6 for controlling the operations of the above-described units 2, 3, 4, and 5 of the image forming apparatus 1.

  The image forming unit 3 is disposed at the center in the vertical direction of the image forming apparatus 1. The image forming unit 3 includes a laser beam generator 7 for obtaining a predetermined beam light corresponding to the image data from the reading unit 2 and a photosensitive drum 8, and forms a latent image corresponding to the predetermined beam light on the laser beam generator 7. Then, the image forming unit 9 that visualizes the latent image into a toner image, the transfer unit 10 that transfers the toner image onto the paper P0 as a transfer material, and the fixing unit that heats and fixes the transferred toner image onto the paper P0. 11.

  The sheet conveyance unit 5 is disposed along one side of the image forming apparatus 1, and includes a discharge conveyance path 12A, a discharge conveyance path 12B, a discharge conveyance path 12C, a return conveyance path 12D, and a branch conveyance path 12E. And have. The discharge conveyance path 12A, the discharge conveyance path 12B, the discharge conveyance path 12C, the return conveyance path 12D, and the branch conveyance path 12E are connected to each other to form a loop shape as a whole. In the discharge transport path 12A, the discharge transport path 12B, the discharge transport path 12C, the return transport path 12D, and the branch transport path 12E, the paper P0 is guided along a guide member (not shown) and rotates. (Not shown). In FIG. 1, the conveyance paths 12 </ b> A to 12 </ b> E are illustrated by arrows indicating the conveyance directions of the conveyance paths 12 </ b> A to 12 </ b> E.

  The paper P0 is transported from the paper supply unit 4 to the image forming unit 3 along a discharge transport path 12A (also referred to as an upstream transport path 12A), and is transported along the discharge transport path 12B in the image forming unit 3. Then, the paper is discharged from the image forming unit 3 toward the discharge tray 13 as the outside of the apparatus from the discharge transport path 12C (also referred to as the downstream transport path 12C) in a substantially horizontal direction. The discharge tray 13 is disposed between the image forming unit 3 and the reading unit 2 so as to face the end portion (end position) 14 of the downstream side conveyance path 12C, and is opened outside the apparatus.

  First and second discharge rollers 16 and 17 are disposed at the end portion 14 of the downstream conveyance path 12C. The first and second discharge rollers 16 and 17 rotate forward so that the sheet P0 conveyed on the downstream conveyance path 12C and having the image formed thereon is directed toward the discharge tray 13 outside the apparatus. Send out and discharge.

  The return conveyance path 12D has an entry end at a first position upstream of the end portion 14 of the downstream conveyance path 12C and downstream of the fixing unit 11, and is upstream of the transfer unit 10 of the upstream conveyance path 12A. Each of the outlet ends is connected to the merging portion 15 and is provided to convey the paper P0 from the inlet end to the merging portion 15. A posture changing path 12D-1 (described later) is provided at the entrance end of the return transport path 12D so as to be shared with the end portion 14 of the downstream transport path 12C.

  This return conveyance path 12D switches back the paper P0 conveyed toward the discharge tray 13 along the downstream conveyance path 12C and reverses the front and back of the paper P0 when images are formed on both sides of the paper P0. It is provided to make it. That is, when the first and second discharge rollers 16 and 17 are rotated forward, the paper P0 is transported through the downstream transport path 12C. When the trailing end of the transported paper P0 in the transport direction F1 of the downstream transport path 12C reaches the position of the first and second discharge rollers 16, 17, the first and second discharge rollers 16, 17 Is temporarily stopped from rotating. As a result, the rear end portion of the paper P0 is left in the apparatus, and the portion of the paper P0 other than the rear end portion is discharged to the discharge tray 13. The first and second discharge rollers 16 and 17 are rotated in the reverse direction, and are conveyed in the return conveyance path 12D with the trailing edge of the paper P0 set as the leading side.

  The branch conveyance path 12E is provided for conveying the sheet P0 from the branching portion 18 of the downstream conveyance path 12C to the predetermined portion 19 of the return conveyance path 12D. A branch lever 20 serving as a branch member for switching the transport direction of the paper P0 is provided at the branch portion 18 of the downstream transport path 12C. The branch lever 20 switches the transport direction of the paper P0 sent out from the fixing unit 11 to one of the direction along the downstream transport path 12C and the direction along the branch transport path 12E.

  Although not shown, the control unit 6 includes a microcomputer as a control center and an operation unit connected to the control unit and operated by a user. In accordance with an input signal from the operation unit, the microcomputer controls each unit 2, 3, 4, 5 based on a program stored in advance.

  The image forming apparatus 1 according to the present embodiment has a double-sided image forming function for forming images on both sides of the paper P0. As a configuration for this function, double-sided image formation control means for automatically performing these operations sequentially while controlling the operations of the return conveyance path 12D of the sheet conveyance unit 5 and the sheet conveyance unit 5 and the image forming unit 3. As a control unit 6.

  At the time of double-sided image formation, the control unit 6 performs control according to the following procedure. First, the paper P0 is transported along the discharge transport paths 12A, 12B, and 12C, and an image is formed on the surface P4 of the paper P0 by the image forming unit 3 during that time. The paper P0 on which the image is formed on the front surface P4 is switched back at the end portion 14 of the discharge conveyance path 12C and returned to the return conveyance path 12D. The sheet P0 is transported along the discharge transport paths 12A, 12B, and 12C via the return transport path 12D. The sheet P0 that has been switched back and returned to the upstream position from the transfer section 10 of the discharge transport path 12A through the return transport path 12D is opposite to that when the image is formed on the front surface P4. An image is formed on the back surface P5 of the paper P0 by the image forming unit 3. The paper P0 on which images are formed on both sides is discharged to the discharge tray 13.

  2 is a front view showing the vicinity of the discharge roller, FIG. 3 is a view of the vicinity of the front side of the discharge roller from the oblique left, and FIG. 4 is an oblique view of the lower partition member forming the return conveyance path. It is the figure seen from the right side. In FIG. 2 and FIG. 3, reference numeral 23 denotes a static elimination brush. Similarly, reference numeral 24 in FIGS. 2 and 3 denotes a transport roller for easily transporting the paper P0 in the discharge transport path 12C, and is omitted in FIG.

  The discharge conveyance path 12C having the discharge rollers 16 and 17 is guided to the discharge rollers 16 and 17 in a state where the paper P0 is bent. Further, the posture changing path 12D-1 provided at the entrance side end portion of the return conveyance path 12D is provided in a state shared with the terminal end portion 14 of the downstream conveyance path 12C, and is provided to the discharge rollers 16 and 17. The guided paper P0 can be changed in posture from a bent state to an extended state in which the paper P0 extends almost straight.

  A rear end detection that optically detects that the rear end of the sheet P0 has entered the posture change path 12D-1 on the opposite side of the discharge conveyance path 12C in the posture change path 12D-1 from the branch lever 20. A sensor 22 is provided. The trailing edge detection sensor 22 is, for example, a reflection type sensor, and when the trailing edge of the paper P0 passes, the reflected light from the paper P0 is not captured, thereby detecting the trailing edge of the paper P0. This detection signal is given to the control unit 6, and the control unit 6 temporarily stops the rotation of the discharge rollers 16 and 17 based on the signal input. At this time, the sheet P0 is set to stop in a state in which the rear end thereof is inside the posture changing path 12D-1.

  Between the discharge rollers 16 and 17 and the branch lever 20 in the discharge conveyance path 12C, a pair of flexible members 21 having waists are provided on the left and right. These flexible members 21 are made of resin, for example, PET, formed in a strip shape, and a lower end portion 21a is attached to a lower partition member 12C-1 that constitutes the discharge conveyance path 12C. Further, these flexible members 21 are arranged so that the upper portion 21b crosses the discharge conveyance path 12C, and is provided so as to come into contact with the lower surfaces of both ends of the paper P0 in the width direction of the discharge conveyance path 12C. ing. Further, the hardness of the flexible member 21 is such that the flexible member 21 is bent by the sheet P0 conveyed in a bent state on the discharge conveyance path 12C, and the rear end side of the sheet P0 that enters the posture changing path 12D-1. Is set so that the sheet P0 can be held in an extended state by pushing it upward.

  Therefore, in the case of the image forming apparatus 1 according to the present embodiment configured as described above, when an image is formed on both sides of the paper P0, the rear end of the paper P0 enters the posture changing path 12D-1 and stops. Then, although the bent sheet P0 changes to an extended state, even if the trailing edge of the sheet P0 is not supported and is easy to sag, the waisted flexible member 21 comes into contact with the lower surface of the sheet P0 and the sheet The rear end of P0 is pushed up and held in an extended state to prevent the rear end of the paper P0 from dripping. This makes it possible to reliably return the paper P0 to the return conveyance path 12D at the time of switchback and prevent the paper P0 from being caught. When an image is formed on one side of the paper P0, when the paper P0 is supplied to the discharge rollers 16 and 17 via the discharge transport paths 12A to 12C, the transport area (discharge transport path 12C) of the paper P0 is supplied. ) Is crossed by the flexible member 21 having a waist, but the flexible member 21 is indicated by a broken line from the extended state indicated by the solid line in FIG. 2 by the paper P0 conveyed on the discharge conveying path 12C. Therefore, paper conveyance is allowed and is not disturbed. Further, the flexible member 21 can be made inexpensive by cutting and using a commercially available PET sheet.

  In the above-described embodiment, a pair of the flexible members 21 are arranged on both sides in the width direction of the discharge conveyance path 12C. However, the present invention is not limited to this, and is made to correspond to a place where the trailing edge of the sheet hangs down. You may arrange | position by 1 or 3 or more.

  In the above-described embodiment, a reflective optical sensor is used as the rear end detection sensor 22, but the present invention is not limited to this. For example, a transmissive optical sensor or a sensor that detects whether the contact that contacts the paper with a weak force has contacted or separated from the paper by detecting the change in the angle of the contact may be used.

1 is a schematic front view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a front view showing a vicinity of a discharge roller in the image forming apparatus of FIG. 1. FIG. 2 is a diagram of a portion near the front side of a discharge roller in the image forming apparatus of FIG. 1 as viewed obliquely from the left. It is the figure which looked at the lower division member which forms a return conveyance path from diagonally right. It is a figure for demonstrating the problem in the case of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Transfer part 11 Fixing part 12A, 12B, 12C Ejection conveyance path 12D Return conveyance path 12D-1 Posture change path 16, 17 Ejection roller 21 Flexible member with waist 22 Rear end detection sensor (rear end) Detection means)
P0 paper

Claims (3)

An image forming apparatus that selects one side or both sides of a sheet, forms a image on a selected side or both sides through a transfer unit and a fixing unit in this order, and then discharges the sheet from a discharge roller to the outside.
Passing through the transfer section and the fixing section and having the discharge roller in the vicinity of the end position, the sheet on which the image is formed is bent and guided to the discharge roller, and the sheet is substantially horizontally directed from the discharge roller to the outside. A discharge conveying path for discharging toward the
The entrance end is at a first position upstream of the discharge roller of the discharge transport path and downstream of the fixing section, and the exit end is at a second position upstream of the transfer section of the discharge transport path. Are connected to each other, and the bent paper supported by the discharge roller is changed to an extended state, and the reverse rotation of the discharge roller causes the paper to pass from the input side end to the discharge conveyance path through the output side end. A return conveyance path having a posture change path that changes the posture of the sheet from the bent state to the extended state in a state of sharing the discharge conveyance path with the entry side end portion;
A flexible member that is provided on the posture changing path so as to be in contact with the lower surface of the sheet and that allows the sheet to be bent and holds the sheet in the extended state by pushing up the rear end of the sheet. And
When an image is formed on one side, the paper is discharged to the outside through the discharge conveyance path. When an image is formed on both sides, the paper is guided to the discharge roller via the discharge conveyance path and then the discharge roller is rotated in reverse. Then, the image forming apparatus is configured to switch back to the return conveyance path and then discharge the sheet from the discharge conveyance path to the outside. The image forming apparatus according to claim 1,
The waist-forming flexible member is made of a resin film. The image forming apparatus according to claim 1, wherein
And a rear end detecting means for detecting that the rear end of the sheet transported through the discharge transport path has entered the posture changing path and temporarily stopping the rotation of the discharge roller based on the detection. An image forming apparatus.

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