JP3813383B2 - Double-sided device of image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a double-sided image forming apparatus in which a sheet having an image formed on a first surface is re-fed by a conveying unit such as a conveying roller provided in a double-sided conveying path in order to form an image on a second surface. Relates to the device.
[0002]
[Prior art]
Conventionally, the paper on which the image is formed on the first surface in the image forming unit of the image forming apparatus is turned to the image forming system again with the front and back reversed in order to form an image on the second surface. There is a double-sided device that re-feeds paper (for example, see Japanese Patent Laid-Open No. 5-53393).
In such a double-sided apparatus, a sheet of paper that has been turned upside down is stopped at one end by a double-sided conveyance path that is provided with a plurality of conveyance means each composed of a pair of conveyance rollers and conveyance rollers at intervals in the sheet conveyance direction. After that, there is something that refeeds it.
[0003]
[Problems to be solved by the invention]
However, when the sheet is stopped while being sandwiched between a plurality of pairs of conveyance rollers and conveyance rollers in the double-sided conveyance path in this way, depending on the conveyance roller stop timing at that time, In some cases, the end is soiled by toner or the like adhering to the transport roller or transport roller in a minute amount.
[0004]
That is, as shown in FIG. 11, a conveyance roller 72, a conveyance roller 73, a conveyance roller 74, a conveyance roller 75, a conveyance roller 76, and a conveyance roller 77 that are paired with the double-side conveyance path 71 are provided. The sheet P on which the image is formed on the first surface (front surface) is sandwiched between the transport roller 72 and the transport roller 73 at the substantially intermediate portion, and the transport roller 74 and the transport roller 75 at the rear end portion Pr. When the paper is once stopped in the state, the rear end portion Pr of the paper P may be soiled.
[0005]
This occurs when the conveyance roller 74 continues to rotate even after the conveyance roller 72 has stopped. In this case, the conveyance of the entire sheet is stopped because the conveyance roller 72 has stopped rotating. However, since the transport roller 74 continues to rotate, the rear end portion Pr of the paper P is transported until it passes through the nip between the transport roller 74 and the transport roller 75 as shown in FIG.
[0006]
However, since the leading end side of the paper P is in a stopped state, the paper P is in a state where the portion located between the transport roller 72 and the transport roller 74 is bent as shown in the figure, and the rear end is the paper itself. Due to the strength of the waist, the rotating roller 74 remains in contact with the rotating nip between the conveying roller 74 and the conveying roller 75.
[0007]
Therefore, if a small amount of toner or the like adheres to the surface of the transport roller 74 or the transport roller 75, the stain is rubbed against the rear end portion Pr of the paper P, and the rear end portion Pr becomes dirty. That happened.
In addition, the stain at the rear end of the paper is likely to become dirty as the thickness of the paper increases.
[0008]
The present invention has been made in view of the above problems, and the rear end portion of a sheet that is re-fed to form an image on the second surface after the image is formed on the first surface is double-sided. An object is to prevent contamination by the conveying means provided in the conveying path.
[0009]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention receives a sheet having an image formed on the first surface in a duplex conveying path provided with a plurality of conveying units at intervals in the sheet conveying direction, and then accepts the sheet on the second side. in double-side unit of the image forming apparatus for refeeding by said conveying means to form an image on the surface, relative to the two conveying means of the plurality of conveying means, the paper received in the duplex conveyance path above Double-sided paper stop selectively controlled when stopping with both of the two conveying means held together and when stopping the rear end portion of the paper between the two conveying means Position control means is provided.
[0010]
Further, the double-sided device of the image forming apparatus includes a thick paper mode selection means for selecting a thick paper mode when using thick paper as the paper, and the double-sided paper stop position control means selects the thick paper mode by the thick paper mode selection means. In this case, it is preferable that the sheet received in the duplex conveyance path is a means for stopping the sheet so that the rear end portion is positioned between the two conveyance means.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a conveyance system and a double-side device of an image forming apparatus as a basis of the present invention together with a control system, and FIG. 2 is an overall configuration diagram showing an image forming apparatus equipped with the double-side device.
[0013]
The double-sided device 2 shown in FIG. 1 includes a conveyance roller 41, a conveyance roller 42, and a conveyance roller 41 that forms a plurality of pairs of sheets (transfer sheets) P having an image formed on a first surface (front surface) in the sheet conveyance direction. In order to form an image of the paper P on the second surface (back surface) after receiving the transport roller 43, the transport roller 44, the transport roller 45, and the transport roller 46 in the duplex transport path 15 provided at intervals. The sheet is fed again by the conveying roller 41 and the conveying roller 42, and is provided in the apparatus main body 1 of the image forming apparatus as shown in FIG.
[0014]
The image forming apparatus includes a latent image on a photosensitive member 6 in which an optical writing system 4 is provided in an image forming system 5 based on image data read by an optical reading system 3 provided in the apparatus main body 1. The developing device 7 of the image forming system 5 converts the latent image into a visible image with toner.
Note that when double-sided image formation described later (mode in which images are formed on both the front and back sides of the paper), image data read by the optical reading system 3 is stored in advance in a storage unit, and the image data is used as a basis. The optical writing system 4 sequentially forms latent images on the photosensitive member 6.
[0015]
On the other hand, the sheet P is fed from a sheet feeding system 8 provided at the lower part of the apparatus main body 1 and conveyed to the image forming system 5 through a conveying path 19 so that the visible image on the photosensitive member 6 is transferred onto the sheet P. Transfer to the correct position.
The paper P is conveyed to the fixing device 9 where the visible image (toner image) is fixed, and then guided to the paper discharge branch claw 33 at the swing position indicated by the phantom line in FIG. Then, the paper is discharged onto a paper discharge tray 11 outside the apparatus main body 1 by the paper discharge roller pair 20.
[0016]
Alternatively, in the case of performing reverse paper discharge in which the paper P is reversed after being reversed, or double-sided image formation in which an image is also formed on the back surface, the paper discharge branch claw 33 is in the swing position indicated by the solid line in FIG. Since it is swinging, the paper P is transported from the reverse transport path 12 toward the duplex device 2.
[0017]
That is, when paper P is reversely discharged, the paper P is sent to the reverse conveyance path 12 and once transported to the double-sided tray 13 of the double-sided device 2, the traveling direction is reversed, and the reverse feed path 1 is guided to the reverse paper discharge passage 14 by a double-sided branch claw 28 shown in phantom lines in FIG.
[0018]
Further, in the case of double-sided image formation, the paper P sent to the reverse conveyance path 12 is similarly once conveyed to the double-sided tray 13 and then the traveling direction is reversed, and this time double-sided branching shown by the solid line in FIG. Guided by the claw 28 and conveyed to the double-sided conveyance path 15. Then, the sheet P is sent again to the image forming system 5 shown in FIG. 2, and after an image is formed on the back surface, the sheet P is conveyed straight from the fixing device 9 and discharged onto the sheet discharge tray 11.
[0019]
Next, the double-sided device 2 will be described in detail.
As shown in FIG. 1, the double-sided device 2 has a leading end portion (in the drawing) between a conveying roller 10 in which a plurality of rollers 17 are attached in a skewer shape with a space on a roller support shaft 16 and a plurality of adjacent rollers 17. The reversing branch claw 18 that is urged to rotate so that the (right side) side enters, and is conveyed while being pressed against the roller 17 of the transport roller 10 by the reversing branch claw 18, passes through the reversing branch claw 18 and passes through the double-sided tray 13. There is provided a reverse conveying means comprising a reverse rotation driving roller 21 and a reverse rotation driven roller 22 for conveying the sheet P conveyed upward in the direction of arrow A opposite to the conveyance direction by the conveyance roller 10.
[0020]
The reverse driven roller 22 is moved by a solenoid (not shown) to a retracted position indicated by a solid line in FIG. 1 and a paper feeding position indicated by an imaginary line. The sheet P is retracted to the position, and when the sheet P is reversely conveyed (reversely fed), the sheet P is lowered to the position indicated by the phantom line.
[0021]
Further, in this double-sided device 2, when the trailing end of the paper P conveyed by the conveying roller 10 passes the tip of the reverse branching claw 18, the reverse branching claw 18 swings counterclockwise in FIG. Therefore, when the paper P is reversed and conveyed by the reverse drive roller 21 and the reverse driven roller 22 in the reverse direction, it is guided by the reverse branch claw 18 and conveyed to the reverse feed path 23. .
[0022]
The reverse feed path 23 is provided with a double-sided drive roller 31 that conveys the paper P fed to the left side in FIG. 1 and a double-sided driven roller 32 that is driven to rotate while being pressed against the double-sided drive roller 31. . Further, on the left side of the double-sided drive roller 31, a double-sided branch claw 28 that can swing between a position indicated by a solid line and a position indicated by a virtual line is provided.
[0023]
The double-sided device 2 is provided with a pair of position-regulating side fences 29 that can approach and separate from each other on the double-sided tray 13, whereby the positions of both side edges in the paper width direction perpendicular to the paper P transport direction. To regulate.
Further, the double-sided device 2 is provided with a detection sensor 26 for detecting the paper passing through the reversing branch claw 18 on the upstream side in the paper conveyance direction of the conveyance roller 10. As the detection sensor 26, for example, a reflection type photosensor is used.
[0024]
The conveyance rollers 41, 43, and 45 are driving-side rollers, and the driven-side conveyance rollers 42, 44, and 46 are in pressure contact with each other.
The conveying roller 41 is connected to a drive system via a clutch 55, and can be driven to rotate independently or stopped by turning the clutch 55 on and off. .
[0025]
Further, the transport rollers 43 and 45 are connected to each other, and one of the transport rollers 43 (may be on the transport roller 45 side) is connected to a drive system via a clutch 56. Accordingly, by turning the clutch 56 on and off, the conveying rollers 43 and 45 can be simultaneously driven to rotate or stopped.
[0026]
A detection sensor 61 is disposed between the conveyance rollers 41 and 43 in the double-sided conveyance path 15. A detection sensor 62 is also disposed between the transport rollers 43 and 45. Further, a detection sensor 63 is also arranged upstream of the pair of registration rollers 35 on the conveyance path 19 in the sheet conveyance direction.
The detection sensors 61, 62 and 63 are, for example, reflection type photosensors.
[0027]
Further, the double-sided device 2 serves as double-sided paper stop position control means for stopping the paper P received in the double-sided conveyance path 15 at a position where the trailing edge Pr does not contact any of the plurality of conveyance rollers 41, 43, 45. A functioning control device 50 is provided.
That is, the control device 50 determines that the paper P conveyed to the double-sided conveyance path 15 passes through the nip between the pair of conveyance rollers 43 and the conveyance rollers 44, as shown in FIG. The clutches 55 and 56 are controlled so as to stop at the position shown in FIG.
[0028]
The control device 50 includes a central processing unit (CPU) having various determination and processing functions, a ROM storing each processing program and fixed data, a RAM serving as a data memory storing processing data, and an input / output circuit (I / O) and a microcomputer 51 as shown in FIG. A timer 52 is also provided.
[0029]
The control device 50 receives signals output from the detection sensors 61 and 62 when they detect a sheet. Various sensor signals are also input from other sensors. The control device 50 outputs a signal for driving the clutch 55 for driving the transport roller 41 at a predetermined timing.
Further, a signal for driving the clutch 56 for driving the conveying roller 43 is output at a predetermined timing.
Furthermore, signals for driving them at a predetermined timing are also output to other drive systems.
[0030]
Next, double-sided image formation in this image forming apparatus will be described in detail with reference to specific examples with reference to FIGS.
In this image forming apparatus, when double-sided image formation is performed in which images are formed on both the first side and the second side of a plurality of sheets (in this example, six or more sheets will be described), FIG. 3, three sheets P1, P2, and P3 are continuously fed and a target image is formed on the first surface (front surface) by the image forming system 5, respectively.
The fourth sheet P4 is also fed, but once stopped, the leading end is positioned between the refeed lower guide plate 36 and the feed right guide plate 37 shown in FIG.
[0031]
The three sheets P1, P2, and P3 on which the image is formed on the first surface in the image forming system 5 are sequentially transported to the double-sided device 2, and are reversed and transported to the double-sided transport path 15. On the other hand, the first sheet P1 is fed again without being stopped in the duplex conveying path 15, and after the image is formed on the second surface (back surface) by the image forming system 5, the sheet discharge tray 11 is discharged straight. Discharged to the top.
Then, at the timing when the detection sensor 63 detects the trailing edge of the first sheet P1, the fourth sheet P4 waiting between the refeed lower guide plate 36 and the right sheet guide plate 37 is provided. Is resumed.
[0032]
On the other hand, when the leading edge of the second sheet P2 conveyed into the duplex conveying path 15 is detected by the detection sensor 61 as shown in FIG. (FIG. 3) stops when the rotational force to the transport roller 41 is cut off.
Further, when the leading edge of the third sheet P3 is detected by the detection sensor 62, the rotational force applied to the transport rollers 43 and 45 is applied by the clutch 56 (FIG. 3) after a predetermined time has passed since that time. Stops when blocked.
[0033]
When the detection sensor 63 detects the trailing edge of the fourth sheet P4 that forms an image on the first surface, the second sheet P2 that has been stopped on the duplex conveyance path 15 at that timing is fed. Is resumed. The third sheet P3 is fed again after the second sheet P2 is fed again. When the leading edge of the third sheet P3 is detected by the detection sensor 61, a predetermined time has passed. The clutch 55 stops when the rotational force to the conveying roller 41 is cut off (see FIG. 6).
[0034]
At this time, as with the fourth sheet P4 described above, the fifth sheet P5 is temporarily placed at a position where its leading edge is positioned between the refeed lower guide plate 36 and the right sheet feed guide plate 37. It is in a stopped state.
When the detection sensor 63 detects the trailing edge of the second sheet P2 that forms an image on the second surface, it waits between the re-feeding lower guide plate 36 and the feeding right guide plate 37 at that timing. The feeding of the fifth sheet P5 is resumed.
[0035]
When the detection sensor 63 detects the trailing edge of the fifth sheet P5, the feeding of the third sheet P3 that has been stopped on the duplex conveyance path 15 is resumed at that timing.
Next, the sixth sheet P6 is fed and temporarily stopped between the lower sheet refeeding guide plate 36 and the sheet feeding right guide plate 37, and the third sheet P3 forming an image on the second side. When the detection sensor 63 detects the trailing edge, the feeding of the sixth sheet P6 waiting between the lower sheet refeeding guide plate 36 and the sheet feeding right guide plate 37 at that timing is resumed.
[0036]
At this time, as shown in FIG. 7, the fourth sheet P4 has already entered the double-sided conveyance path 15, and after a predetermined time has passed since the leading edge of the sheet P4 is detected by the detection sensor 61, the clutch 55 supplies the conveyance roller 41 to the conveyance roller 41. When the rotational force is cut off, it stops at the predetermined position shown in the figure.
[0037]
After that, when the detection sensor 63 detects the trailing edge of the sixth sheet P6, the fourth sheet P4 on the duplex conveying path 15 is fed, and the seventh and subsequent sheets P7 are the same. The paper is fed into.
The second and subsequent sheets are all discharged straight onto the discharge tray 11 after the image is formed on the second side.
[0038]
As described above, in this image forming apparatus, when double-sided image formation is performed on a plurality of sheets, double-sided image formation is performed by the above-described operation. At that time, each sheet is formed as shown in FIG. FIG. 8 shows the order of passing through the photoreceptor 6 of the image system 5.
That is, when double-sided image formation is performed on a plurality of sheets with this image forming apparatus, the first to third sheets P1 to P3 are continuously conveyed to the photosensitive member 6 and the image on the first surface (front surface). Each of the images is formed, and then an image is formed on the second surface (back surface) of the first sheet P1.
[0039]
Thereafter, image formation on the first side (front side) of the fourth sheet P4 is performed, and then image formation on the second side (back side) of the second sheet P2 is performed.
Thereafter, image formation is performed in the following order. That is, the first side (front side) of the fifth sheet P5 → the second side (back side) of the third sheet P3 → the first side (front side) of the sixth sheet P6 → the fourth sheet P4. 2nd side (back side) → 7th sheet P7 first side (front side)...
[0040]
As described above, in this image forming apparatus, when double-sided image formation is performed, the second and subsequent sheets of paper P are temporarily stopped in the double-sided conveyance path 15, but at that time, the conveyance roller 41 is set to 2 After the detection sensor 61 detects the leading edge of the second and subsequent sheets, the sheet stops after a predetermined time has elapsed.
However, the transport rollers 43 and 45 located on the downstream side in the paper transport direction continue to rotate until a predetermined time elapses after the detection sensor 62 detects the leading edge of the next paper.
[0041]
Therefore, in the case of such a configuration, as described with reference to FIG. 12, when the conveyance is stopped while the rear end portion of the sheet is in contact with the rotating conveyance roller, the rotation is continued. When a small amount of toner or the like has adhered to the surface of the conveying roller, the stain is rubbed against the trailing edge of the paper, and the trailing edge is likely to become dirty.
[0042]
However, in the double-sided device 2, as described above, when the conveyance is stopped in a state where the paper P is held by the conveyance roller 41 and the conveyance roller 42 shown in FIG. Is stopped at a position where it does not come into contact with the transporting roller 43, so that the rear end portion Pr can be prevented from being stained.
[0043]
FIG. 9 is a block diagram similar to FIG. 3 showing an embodiment of the double-sided apparatus of the image forming apparatus according to the present invention, and portions corresponding to those in FIG.
The double-sided apparatus according to this embodiment is provided with a thick paper mode selection key 27 which is a thick paper mode selection means for selecting a thick paper mode when using thick paper as a paper, and functions as a double-sided paper stop position control means. ′ Indicates that the paper P received in the double-sided conveyance path 15 described with reference to FIG. 1 when the thick paper mode is selected by the thick paper mode selection key 27, the trailing edge Pr of which of the plurality of conveyance rollers 41, 43, 45 1 is different from the double-sided apparatus 2 described with reference to FIG.
[0044]
When the thick paper mode is not selected by the thick paper mode selection key 27, the control device 50 'transfers the paper P received in the double-sided conveyance path 15 to the conveyance roller 41, the conveyance roller 42, the conveyance roller 43, the conveyance roller 44 ( The operations of the clutches 55 and 56 are controlled so as to be stopped while being held by both of them (see FIG. 1).
[0045]
In this way, if the thick paper mode is selected when the trailing edge is thick paper that is easily soiled, the trailing edge of the sheet is stopped at a position where it does not come into contact with the transport roller 43, and the trailing edge becomes dirty. Can be prevented.
[0046]
In the case of relatively thin paper, if the thick paper mode is not selected, the paper is stopped while being held between the transport roller 41, the transport roller 42, the transport roller 43, and the transport roller 44. When the paper is held and stopped only by the transport roller 41 and the transport roller 42, if the clutch 55 is not cut well, the stop timing of the transport roller 41 is delayed, and the stop position of the paper is shifted to cause a transport failure. However, according to the double-sided apparatus according to this embodiment, the trailing edge Pr of the sheet is held and stopped by the conveying roller 43 and the conveying roller 44, so that the positional deviation of the sheet can be prevented. Therefore, conveyance failure can be avoided.
The cardboard mode selection key 27 is provided on, for example, an operation panel outside the apparatus.
[0047]
FIG. 10 is a block diagram similar to FIG. 3 showing another embodiment of the double-sided apparatus of the image forming apparatus according to the present invention, in which parts corresponding to those in FIG.
In the duplex device according to this embodiment, the transport roller 41, the transport roller 42, the transport roller 43, and the transport roller 44 are simultaneously brought into contact with a plurality of locations including the rear end portion Pr of the paper P received in the duplex transport path 15. Therefore, a control device 50 ″ for stopping the conveying rollers 41 and 43 simultaneously is provided.
That is, in this embodiment, the control device 50 ″ functions as a transport means simultaneous stop control means.
[0048]
According to this double-sided device, the paper P that is temporarily stopped in the double-sided conveyance path 15 is stopped in a state where it is in contact with the conveyance roller 41, the conveyance roller 42, the conveyance roller 43, and the conveyance roller 44. Since the clutches 55 and 56 are controlled so that the transport rollers 41 and 43 are stopped simultaneously, it is possible to prevent the transport roller 43 from being rubbed against the trailing edge Pr of the paper P.
[0049]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
According to the double-sided apparatus of the image forming apparatus of the first aspect, the sheet fed into the double-sided conveyance path can be stopped at a position where the rear end portion does not contact any of the plurality of conveying units. Can be prevented from being contaminated by toner or the like adhering to the conveying means.
[0050]
According to the double-sided apparatus of the image forming apparatus of the second aspect, when using thick paper as the paper, the thick paper mode is simply selected by the thick paper mode selection means, and the trailing edge of the thick paper fed into the double-sided conveyance path is displayed. since it is possible to stop so as to be positioned between the two conveying means, it is possible to prevent the rear end portion thereof becomes dirty.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a conveyance system and a duplex device of an image forming apparatus as a basis of the present invention together with a control system.
FIG. 2 is an overall configuration diagram showing an image forming apparatus equipped with the double-sided device.
3 is a block diagram showing the control system of FIG. 1 and its related configuration. FIG.
4 is a schematic diagram illustrating a state where a fourth sheet is fed when double-sided image formation is performed by the image forming apparatus of FIG.
FIG. 5 is a schematic diagram showing a state in which the first sheet is formed on the first side and then re-fed to the image forming unit to form an image on the second side in the image forming apparatus. is there.
FIG. 6 is a schematic view showing a state where up to the sixth sheet is similarly fed by the image forming apparatus.
FIG. 7 is a schematic view showing a state where up to the seventh sheet is similarly fed by the image forming apparatus.
FIG. 8 is an explanatory diagram showing the order in which each sheet passes through the photoconductor when the double-sided image formation is performed.
9 is a block diagram similar to FIG. 3, showing an embodiment of a double-sided device of an image forming apparatus according to the present invention.
FIG. 10 is a block diagram similar to FIG. 3 showing another embodiment of the double-sided device of the image forming apparatus according to the present invention.
FIG. 11 is a schematic diagram illustrating an example in which an intermediate portion and a rear end portion of a sheet are sandwiched and stopped by a conveyance roller and a conveyance roller in a duplex conveyance path, respectively.
12 is a diagram for explaining a state in which the rear end portion of a sheet is soiled when the conveyance roller holding the rear end portion of the sheet and the conveyance roller are rotated in the configuration shown in FIG. FIG.
[Explanation of symbols]
2: Double-sided device 15: Double-sided conveyance path 27: Thick paper mode selection key (thick paper mode selection means)
41, 43, 45: Conveying rollers (conveying means)
42, 44, 46: Conveying roller (conveying means)
50, 50 ', 50 ": control device P: paper

Claims (2)

In order to form the image on the second side of the paper after the paper having the image formed on the first side is received in a double-sided conveyance path provided with a plurality of intervals in the paper conveyance direction. In the double-side device of the image forming apparatus that re-feeds by
For two conveying means of the plurality of conveying means,
When the paper received in the double-sided conveyance path is stopped in a state where it is held by both of the two conveying means,
A double-sided apparatus for an image forming apparatus, comprising: a double-sided paper stop position control unit that selectively controls when the rear end of the sheet is positioned between the two conveying units. . The double-sided apparatus of the image forming apparatus according to claim 1, further comprising: a thick paper mode selection unit for selecting a thick paper mode when using a thick paper as the paper, wherein the double-sided paper stop position control unit is controlled by the thick paper mode selection unit. A double-sided apparatus for an image forming apparatus, characterized in that, when a mode is selected, the sheet is received by the double-sided conveyance path so as to stop a sheet so that a rear end portion is positioned between the two conveying units. .

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