JP4485704B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus in which conveyance of a front and rear sheet in an image forming unit is performed in a state where a sheet interval is eliminated or a part of the sheet is overlapped.
[0002]
[Prior art]
Conventionally, from the viewpoint of improving productivity of image forming work, an image forming apparatus that transports the front and rear sheets in the image forming unit in a state where the sheet interval is eliminated or in a state where a part of the sheets is overlapped is proposed. For example, it is disclosed in Japanese Patent Laid-Open No. 2000-7192, Japanese Patent Laid-Open No. 2000-15881, and the like.
[0003]
In the invention of Japanese Patent Laid-Open No. 2000-7192, when a sheet is conveyed through an image forming unit, the sheet is conveyed with no gap between the front and rear sheets. In the invention of Japanese Patent Laid-Open No. 2000-15881, a succeeding sheet is superimposed on a non-recording area of a preceding sheet.
[0004]
In addition, the applicant of the present application provides an inversion path in the middle of the sheet conveyance path from the sheet tray to the image forming section as an image forming apparatus capable of increasing the productivity of image forming work when performing image formation continuously. And paper reversing means, and the paper fed from the paper tray and transported to the image forming unit is switched back in the reversing path, so that the interval of the paper fed into the image forming unit is kept constant and small. Japanese Patent Application No. 11-239672, Japanese Patent Application 2000-230153, and the like have proposed such image forming apparatuses.
[0005]
[Problems to be solved by the invention]
In the invention disclosed in Japanese Patent Laid-Open No. 2000-1588, there is no specific means of how to overlap the front and back sheets.
[0006]
In the invention disclosed in Japanese Patent Laid-Open No. 2000-7192, the interval between the front and rear sheets is simply eliminated in the image forming unit, and the image is not formed by conveying the front and rear sheets in a superimposed manner.
[0007]
In addition, when feeding the front and back sheets to the image forming unit in a superimposed manner, it is difficult to detect the front and rear end positions of the sheets unless the vertical relationship between the front and rear sheets is kept constant. Image formation in a desired state cannot be performed. In the invention described in the above-mentioned publication, there is no mention of the control of the vertical relationship between the front and rear sheets when the front and rear sheets are overlapped.
[0008]
In addition, when the image forming apparatus is an electrophotographic image forming apparatus, if image formation is performed with the front and back sheets superimposed, the lower sheet of the superimposed sheets will The transfer performance of the toner image onto the paper at the edge is degraded, and the image is lost.
[0009]
An object of the present invention is to improve the productivity of image forming work by eliminating the interval between the front and rear sheets conveyed through the image forming unit or by overlapping a part of the front and rear sheets.
[0010]
Another object of the present invention is to perform control so that the vertical positional relationship between the front and rear sheets conveyed in a state where there is no sheet interval, or the front and rear sheets conveyed in a partially overlapped state, is constant. It is.
[0011]
Another object of the present invention is to prevent image loss at the edge of the overlapped portion of the front and back sheets.
[0012]
[Means for Solving the Problems]
  According to the first aspect of the present invention, an image forming apparatus that separates and feeds the sheets stacked and held in the sheet storage unit one by one by the separation sheet feeding unit and forms an image on the fed sheet by the image forming unit. And a reversing path that is connected in the middle of the paper transport path from the paper storage section to the image forming section and that feeds the paper transported through the paper transport path, and switches back the paper that has been fed to the reversing path. Can be switched between a delivery state for sending out to the paper transport path and an open state for allowing at least a part of the preceding paper sent from the reversing path and the succeeding paper sent to the reversing path to overlap. Sheet reversing means and the sheet before and after being fed into the image forming unit.Superimpose partPaper interval control means;Vertical position control means for controlling the vertical positional relationship of the paper before and after a part of which is superimposed;HaveThe vertical position control means includes two pairs of conveying rollers provided between the image forming unit and the reversing path on the sheet conveying path, and the two pairs of conveying rollers are provided for each conveying roller. In the state before and after the control of the vertical positional relationship of the paper before and after the part of the tangent at the position in contact with the conveying rollers facing each other through the paper in the cross section perpendicular to the rotation axis Are arranged so that they are substantially on the same plane, and the control of the vertical positional relationship of the front and back sheets is performed by moving the respective sheets in opposite directions perpendicular to the superimposed surfaces. In the state in which the end portions can be interchanged with each other, and the overlapping portion is positioned between the conveying roller pair provided on the upstream side in the sheet conveying direction and the conveying roller pair on the downstream side. The provided transport roller pair By reciprocating in the order from the top to the bottom in the direction connecting the opposite rotation axis cores in the cross section perpendicular to the rotation axis, the following paper is reciprocated in the order from the bottom to the top, and the following paper is reciprocated in the order from the bottom to the top. Control down.
[0017]
Accordingly, the sheets and the like separated and fed one by one by the separation feeding unit in the sheet storage unit are conveyed through the sheet conveying path, and the sheet conveyed through the sheet conveying path is sent to the reversing path and once in the reversing path. After stopping, the sheet is reversed by the sheet reversing unit and sent out from the reversing path toward the image forming unit.
[0018]
Further, the sheet that is switched back and sent out from the reversing path is superimposed on a part of the front and back sheets by the sheet interval control means, and sent to the image forming unit. As a result, the sheet fed to the image forming unit is transported in a state in which a part of the front and rear sheets are superimposed and image formation is performed, so that the productivity of the image forming operation is increased.
[0019]
When the paper fed into the reversing path is switched back, the paper feeding speed to the reversing path, the paper feeding speed from the reversing path, the timing of feeding the paper from the reversing path, etc. are controlled. The interval between the backed sheets can be reduced. Then, by providing such a reversing path and paper reversing means to reduce the distance between the front and rear sheets in advance, it is possible to accurately perform control for superimposing a part of the front and rear sheets by the paper spacing control means.
[0020]
  And it has a vertical position control means that can control the vertical positional relationship of the superimposed papers so that the subsequent papers can be controlled above and below the preceding papers. As a result, the vertical positional relationship of the paper before and after the overlap of a part of the paper can be maintained in the intended positional relationship, and the paper fed into the image forming unit in a state where the paper is partially overlapped can be maintained. And stable image formation can be performed.
[0024]
  Claim2The described invention is claimed.1In the image forming apparatus described above, the sheet interval control unit varies the sheet feeding start timing.TheControl to superimpose a part of the front and rear sheets is performed.
[0025]
  Therefore, by changing the feed start timing, PaintingThe interval between the front and back sheets can be controlled so that a part of the front and back sheets fed to the image forming unit is overlapped.
[0026]
  Claim3The described invention is claimed.1In the image forming apparatus described above, the sheet interval control unit is configured to change a sheet conveyance speed.TheControl to superimpose a part of the front and rear sheets is performed.
[0027]
  Therefore, by changing the paper transport speed, PaintingThe interval between the front and back sheets can be controlled so that a part of the front and back sheets fed to the image forming unit is overlapped.
[0030]
  Claim4The invention described in claim 1 to claim 13In the image forming apparatus according to any one of,in frontIt has a sheet end detecting means for detecting the leading end and the trailing end of the sheet conveyed in a state where a part of the subsequent sheet is overlapped.
[0031]
  Therefore,in frontEven if the paper is transported in a state where a part of the subsequent paper is superimposed, the leading edge and the trailing edge of the paper can be detected, and various controls can be performed at the timing based on the detection result.
[0032]
  Claim5The described invention is claimed.4In the image forming apparatus described above, a detection path is provided such that a step is generated in a cross-sectional direction of the transport path between the front end side and the rear end side of the transported sheet, and the sheet detection unit is configured to detect the sheet in the detection path. It is a detection sensor provided in the direction in which the level | step difference is made.
[0033]
  Therefore,in frontWhen the paper with a part of the subsequent paper superimposed is transported through the detection path, a difference in level occurs between the leading edge and the trailing edge of the paper. The front end and the rear end can be detected by a detection sensor.
[0034]
  Claim6The described invention is claimed.1Or5In the image forming apparatus according to any one of the above, the image forming apparatus includes a unit that overlaps and forms an image in the vicinity of the overlapped portion of the sheet that is conveyed in an overlapping manner on the preceding and following sheets.
[0035]
Accordingly, an image is likely to be lost in the vicinity of the overlapped portion of the paper, but an image is lost in the vicinity of the overlapped portion of the paper by forming the image in the vicinity of the overlapped portion on the front and back sheets. However, when a single image is formed by joining sheets of paper on which images have been formed in a partially overlapped state, there is an image loss due to the overlapping of the images formed on the front and back sheets. Continuous images can be obtained.
[0036]
  Claim7The described invention is claimed.1Or6In the image forming apparatus according to any one of the above, there is provided means for forming an image showing an area of a superimposed portion of the sheet conveyed in a superimposed manner.
[0037]
Therefore, by looking at the image showing the area of the overlapped portion of the paper that is conveyed in a superimposed manner, it is possible to easily confirm the overlapped portion of the paper that is conveyed in a superimposed manner.
[0038]
  Claim8The described invention is claimed.6In the described image forming apparatus, the image forming apparatus includes a unit that forms an image indicating an area of the image formed on the front and back sheets.
[0039]
Therefore, when an image in the vicinity of the overlapping portion is formed on two overlapping sheets, the images indicating the overlapping image areas are viewed, and the sheets are joined to form one sheet. When forming an image, it is possible to easily check the joining position, and to easily and accurately perform the operation of joining two sheets of paper.
[0040]
  Claim9The invention described in claim 1 to claim 1Any one of 8The image forming apparatus described above includes a sheet interval securing unit that secures an interval between sheets ejected from the image forming unit.
[0041]
  Therefore,in frontEven when the subsequent paper is transported in the image forming unit with a part of it overlapped, the interval between the papers can be secured when the paper is discharged from the image forming unit, It is possible to improve workability when stacking or post-processing sheets discharged from the image forming unit.
  According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the sheet reversing means has a notch portion formed in a part of the outer peripheral portion in parallel with the axis, Is disposed at a position facing the notch driving roller across the sheet fed into the reversing path, and the notched driving roller is rotated when the notched driving roller is rotated. The notched driving roller is driven to rotate in the direction of feeding out the paper, and is in contact with and held by the cylindrical surface portion of the notched driving roller and the driven roller. In which the cutout portion of the notched drive roller is opposed to the driven roller, and a gap is formed between the cutout portion of the notched drive roller and the driven roller. Can be switched It is.
  Therefore, at least a part of the feeding state in which the sheet fed to the reversing path is switched back and sent to the sheet conveying path overlaps with the preceding sheet fed from the reversing path and the succeeding sheet fed to the reversing path. The open state allowing this can be switched only by the rotation of the notched drive roller.
  According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, the reversing path is provided with a jogger that performs skew correction of the fed paper.
  Therefore, skew correction of the paper sent to the paper conveyance path can be performed on the reversing path, so that stable image formation can be performed and space saving of the image forming apparatus can be contributed.
[0042]
DETAILED DESCRIPTION OF THE INVENTION
  Prior to describing the embodiment of the present invention, first,The first of the present inventionreferenceThe embodiment will be described with reference to FIGS. FIG. 1 is a schematic diagram showing an overall structure of an image forming apparatus having a digital electrophotographic image forming unit, and FIG. 2 is a schematic diagram showing an enlarged structure of a sheet reversing unit for switching back a conveyed sheet. 3 is an explanatory diagram for explaining a conveyance state of a sheet switched back by a sheet reversing unit, and FIG.
[0043]
As shown in FIG. 1, in this image forming apparatus, image formation is performed on a sheet tray 1 which is a sheet storage unit in which sheets are stacked and held, a sheet fed from the sheet tray 1, or one side, and then fed again. An image forming unit 2 that forms an image on the other side of the paper that has been formed, a paper discharge tray 3 that discharges the paper on which the image has been formed, and the like are provided.
[0044]
In addition, the image forming apparatus is provided with a paper path from the paper fed from the paper tray 1 to the paper discharge tray 3 via the image forming unit 2. A portion from the image forming unit 2 to the image forming unit 2 is a sheet conveyance path 4.
[0045]
The paper tray 1 is provided with a pick-up roller 5 that feeds the stacked and held paper, a paper feeding roller 6 that separates the paper fed by the pickup roller 5 one by one, and a separation paper feeding means 8 that includes a reverse roller 7. It has been.
[0046]
The image forming unit 2 includes a photosensitive drum 9 on which an image is formed, a charger (not shown) for uniformly charging the surface of the photosensitive drum 9, and an electrostatic latent image on the photosensitive drum 9. Digital writing means (not shown) for writing, a developing device (not shown) for forming a toner image by attaching toner to the electrostatic latent image on the photosensitive drum 9, and transferring the developed toner image onto a sheet There are provided a transfer belt 10 for fixing, a fixing device 11 for fixing the toner image transferred on the paper, and the like.
[0047]
On the sheet conveyance path 4, a sensor 12, a gripper roller 13, a sensor 14, an entrance roller 15, a reverse branch claw 16, a sensor 17, a registration roller 18, a sensor 19, a sync roller 20, and the like are arranged. Sensors 12, 14, 17, and 19 are for detecting the conveyed paper. The registration roller 18 corrects the skew of the conveyed paper, and the sync roller 20 controls the paper feed timing to the image forming unit 2 at the leading edge of the paper.
[0048]
A reversing path 21 that is fed in order to reverse the sheet transported on the paper transporting path 4 is connected to a position in the middle of the paper transporting path 4 where the entrance roller 15 and the reversing branch claw 16 are disposed. ing.
[0049]
On the reversing path 21, the paper fed into the reversing path 21 is switched back and sent out to the paper transport path 4, the preceding paper sent out from the reversing path 21 and the succeeding paper fed into the reversing path 21. A paper reversing means 22 that can be switched to an open state that allows at least a part of the paper to overlap, and a jogger 23 that corrects the skew of the paper fed to the reversing path 21 are provided.
[0050]
As shown in FIG. 2, the sheet reversing means 22 includes a notched drive roller 26 in which a notch portion 24 is formed in a part of the outer peripheral portion in parallel with the axis and the other portion of the outer peripheral portion is a cylindrical surface portion 25. A driven roller that is disposed at a position facing the notched drive roller 26 across the sheet fed into the reversing path 21 and is in contact with the cylindrical surface portion 25 when the notched drive roller 26 is rotated. 27. A motor (not shown) that rotates the notched drive roller 26 is connected to the notched drive roller 26.
[0051]
In FIG. 2B, the driven roller 27 abuts on the cylindrical surface portion 25 of the notched drive roller 26 and the notched drive roller 26 is rotationally driven in the direction of the arrow, and is sandwiched between the notched drive roller 26 and the driven roller 27. In this state, the sheet being fed is fed from the reversing path 21.
[0052]
FIG. 2A shows an open state in which the notch 24 of the notched drive roller 26 faces the driven roller 27 and a gap is generated between the notched drive roller 26 and the driven roller 27. In this open state, the paper is fed into the reversing path 21.
[0053]
Further, the image forming apparatus includes an image forming operation in the image forming unit 2, a separation paper feeding unit 8, a gripper roller 13, an entrance roller 15, a registration roller 18, a sync roller 20, a jogger 23, a paper reversing unit 22, and the like. A control unit (not shown) is provided for controlling according to the detection results of the sensors 12, 14, 17, 19 and other sensors. The image forming apparatus is provided with a sheet interval control unit that eliminates the interval between the sheets before and after being sent to the image forming unit 2 as one of the processes executed by the control unit.
[0054]
In such a configuration, when the start key is pressed after the continuous image forming mode is set, sheets are fed one after another from the sheet tray 1. These sheets are conveyed along the sheet conveying path 4 toward the image forming unit 2, and are sent to the reversing path 21 along the way, switched back by the sheet reversing means 22, and sent out from the reversing path 21. The paper sent out from the reversing path 21 is sent to the image forming unit 2 through the paper transport path 4 and image formation is performed on the paper.
[0055]
When the sheet fed into the reversing path 21 is switched back, the sheet feeding speed to the reversing path 21, the sheet feeding speed from the reversing path 21, the sheet feeding timing from the reversing path 21, and the like are controlled. As a result, the interval between sheets that are switched back and sent to the image forming unit 2 can be reduced.
[0056]
FIG. 3 shows a state in which a certain preceding sheet a is sent out from the reversing path 21 and the leading end of the sheet is sandwiched between the registration rollers 18. At this time, the sheet reversing means 22 is in an open state as shown in FIG. 2A at a timing immediately after the leading end of the sheet is sandwiched between the registration rollers 18. Further, at this time, the succeeding paper b is conveyed to a position where the leading edge reaches the paper reversing means 22. For this reason, the preceding paper “a” sent out from the reversing path 21 and the following paper “b” sent into the reversing path 21 travel in the opposite directions while overlapping a part thereof in the reversing path 21.
[0057]
Next, control for eliminating the interval between the front and rear sheets in the image forming unit 2 by the sheet interval control means will be described with reference to the diagram of FIG. In this diagram, the vertical axis represents the path from the paper feed roller 6 to the photosensitive drum 9, and the horizontal axis represents time.
[0058]
According to this sheet interval control means, the leading end of the preceding sheet (for example, the second sheet) passes at the same time as the trailing end of the preceding sheet (for example, the first sheet) passes through the synchronizing roller 20. It is controlled to reach 20. This control is realized by controlling the paper conveyance speed of the sync roller 20 and the paper conveyance speed of the registration roller 18.
[0059]
Furthermore, since the reversing path 21 and the sheet reversing means 22 are provided, the timing at which each sheet switched back on the reversing path 21 reaches the registration roller 18 can be controlled systematically. It is possible to accurately control the trailing edge of the preceding sheet and the leading edge of the succeeding sheet at a position so that there is no gap.
[0060]
  BookreferenceIn this embodiment, the characteristic part is the waiting time “td” in which the first sheet waits at the position of the registration roller 18, and the waiting time in which the second sheet waits at the position of the registration roller 18. It is not always necessary to coincide with “td ′”, and time adjustment necessary for the leading edge of the second sheet to reach the synchronizing roller 20 at the same time as the trailing edge of the first sheet passes the synchronizing roller 20 is performed. That is.
[0061]
Further, a standby time “tf” in which the first sheet waits at the position of the synchro roller 20 and a standby time “tf ′” in which the second and subsequent sheets wait at the position of the synchro roller 20 are set. The relationship is “tf> tf ′ = 0”.
[0062]
  Next, the second of the present inventionreferenceThe embodiment will be described with reference to FIG. In addition, books such as appearance structurereferenceThe basic structure of the form is the firstreferenceThe basic structure of the image forming apparatus will be described with reference to FIGS. 1 to 3. BookreferenceThe first formreferenceThe part different from the form ofreferenceIn the image forming apparatus of the form, the firstreferenceAs in the above embodiment, as one of the processes executed by the control unit, there is provided a sheet interval control means for eliminating the interval between the sheets before and after being sent to the image forming unit 2, but the control method is different. Is a point.
[0063]
In such a configuration, according to this sheet interval control means, the trailing edge of the preceding sheet (for example, the first sheet) passes through the portion of the photosensitive drum 9 and at the same time the subsequent sheet (for example, two sheets). Control is performed so that the leading edge of the sheet of paper reaches the photosensitive drum 9.
[0064]
In this control, the rotation speed of the sync roller 20 is changed as necessary, and the conveyance from the time when the leading edge of the first sheet reaches the sync roller 20 until the trailing edge of the sheet passes through the photosensitive drum 9 is performed. When the speed is “V4” and the transport speed from when the leading edge of the second and subsequent sheets reaches the synchro roller 20 until the leading edge of the sheet reaches the photosensitive drum 9 is “V5”, “V4” This is done by setting <V5 ”.
[0065]
  Next, the third of the present inventionreferenceThe embodiment will be described with reference to FIG. In addition, books such as appearance structurereferenceThe basic structure of the form is the first and secondreferenceThe basic structure of the image forming apparatus will be described with reference to FIGS. 1 to 3. BookreferenceThe form of the first and secondreferenceThe part different from the form ofreferenceIn the image forming apparatus of the form, the first and secondreferenceAs in the above embodiment, as one of the processes executed by the control unit, there is provided a sheet interval control means for eliminating the interval between the sheets before and after being sent to the image forming unit 2, but the control method is different. Is a point.
[0066]
In such a configuration, according to this sheet interval control means, the trailing edge of the preceding sheet (for example, the first sheet) passes through the sync roller 20 and at the same time, the subsequent sheet (for example, the second sheet). ) Is controlled so as to reach the registration roller 18.
[0067]
In this control, the rotation speed of the registration roller 18 is varied as necessary, and the conveyance speed from when the leading edge of the first sheet passes through the sensor 19 to the sync roller 20 is set to “V3”. When the conveying speed from the leading edge of the first sheet after passing through the sensor 19 to the sync roller 20 is “V3 ′”, “V3> V3 ′” and the first sheet is The relationship between the standby time “tf” waiting at the position of the synchro roller 20 and the standby time “tf ′” where the second and subsequent sheets are waiting at the position of the synchro roller 20 is expressed as “tf> tf ′. = 0 ".
[0068]
  It is also possible to change the sheet conveyance speed “V2” by the sheet reversing means 22 between the first sheet and the second and subsequent sheets (by increasing the conveyance speed of the second and subsequent sheets).referenceCan be controlled.
[0069]
  Next, the first of the present invention1The embodiment will be described with reference to FIG. The basic structure of the present embodiment, such as the external structure, is the first to third.referenceThe basic structure of the image forming apparatus will be described with reference to FIGS. 1 to 3. This embodiment is the first to thirdreferenceIn the image forming apparatus according to the present embodiment, a part different from the above form is superimposed (superimposed) on a part of the sheet before and after being sent to the image forming unit 2 as one of the processes executed by the control unit. A sheet interval control means is provided.
[0070]
In such a configuration, according to the sheet interval control means, the succeeding sheet (for example, the second sheet) is passed before the trailing edge of the preceding sheet (for example, the first sheet) passes through the photosensitive drum 9. The leading edge of the sheet is controlled so as to reach the photosensitive drum 9.
[0071]
This control allows the leading edge of the succeeding sheet (for example, the second sheet) to reach the synchronizing roller 20 before the trailing edge of the preceding sheet (for example, the first sheet) passes through the synchronizing roller 20. As described above, the control is performed by controlling the paper conveyance speed of the synchro roller 20 and the paper conveyance speed of the registration roller 18.
[0072]
Note that the waiting time in which the first sheet is waiting at the position of the sync roller 20 is “tf”, and the waiting time in which the second and subsequent sheets are waiting at the position of the sync roller 20 is “tf ′”. In this case, the amount of overlap of the front and rear sheets can be varied by adjusting the waiting time.
[0073]
  Next, the first of the present invention2The embodiment will be described with reference to FIG. This embodiment is the first1As in the embodiment described above, as one of the processes executed by the control unit, a sheet interval control unit that superimposes (superimposes) a part of the sheet before and after being sent to the image forming unit 2 is provided. However, this embodiment is the first1The difference from the embodiment is that the control direction is different. The basic structure such as the external structure of the image forming apparatus is the same as that described above.Reference form and firstThe basic structure of the image forming apparatus is the same as that of the embodiment, and will be described with reference to FIGS.
[0074]
In such a configuration, according to the sheet interval control means, the succeeding sheet (for example, the second sheet) is passed before the trailing edge of the preceding sheet (for example, the first sheet) passes through the photosensitive drum 9. The leading edge of the sheet is controlled so as to reach the photosensitive drum 9.
[0075]
In this control, the rotation speed of the sync roller 20 is varied as necessary, and the transport speed from when the leading edge of the first sheet passes through the sync roller 20 until the trailing edge of the sheet passes through the photosensitive drum 9. Is “V4”, and the conveying speed from the end of the second and subsequent sheets passing through the synchro roller 20 to the end of the sheet reaching the photosensitive drum 9 is “V6”, “V4 < This is done by setting V6 ″.
[0076]
Note that the amount of superimposition can be adjusted as necessary by varying the difference between the conveyance speeds “V4, V6”.
[0077]
  In addition, the 1st-1st mentioned above3 reference forms, and first and secondIn this embodiment, either the sheet interval control unit that eliminates the interval between the sheets before and after being sent to the image forming unit 2 or the sheet interval control unit that overlaps a part of the sheets before and after being sent to the image forming unit 2. The image forming apparatus having one of them has been described. However, one image forming apparatus may have these two sheet interval control units, and may be controlled by one of the sheet interval control units as necessary. Good.
[0078]
  Next, the first of the present invention3The embodiment will be described with reference to FIGS. 9 and 10. FIG. The basic structure such as the appearance of the image forming apparatus according to the present embodiment has been described above.Each reference form, andIt is the same as each embodiment, the same part is shown with the same code | symbol, and description is also abbreviate | omitted (the same also in the following embodiment).
[0079]
  Two pairs of transport rollers 28 and 29 for transporting the paper are disposed on the paper transport path 4 on which the paper is transported toward the image forming unit 2 and downstream of the reversing path 21. These transport rollers 28 and 29 are provided with a firstreference1 (refer to FIG. 1) can be made to correspond to the registration roller 18 and the synchro roller 20 (however, it is necessary to make the sheet conveyance path between the registration roller 18 and the synchro roller 20 straight), or Further, it may be provided between the registration roller 18 and the entrance roller 15.
[0080]
These conveyance rollers 28 and 29 are each driven to rotate in the direction indicated by the arrow. Further, as shown by the arrows in FIGS. 9B and 9C, the conveyance roller 28 on the upstream side conveys paper. A moving mechanism that moves in a direction perpendicular to the direction is coupled. In this image forming apparatus, as one of the processes executed by the control unit that controls the image forming operation in the image forming unit 2 and the operation of each driving unit, a part of the sheet sent to the image forming unit 2 is received. Vertical position control means is provided for controlling the vertical positional relationship of the paper when it is superimposed.
[0081]
  In such a configuration, the image forming apparatus according to the present embodiment has the above-described first configuration.1Or the second2The sheet is conveyed in the same manner as in the above embodiment, and the two sheets of the front and rear sheets are fed into the image forming unit 2 with a part of them superimposed, and image formation is performed.
[0082]
Here, in order to perform stable image formation on each of the two sheets when the front and rear sheets are fed into the image forming unit 2 in a state of being superimposed, the two sheets are used. It is necessary to maintain the vertical positional relationship of the constant.
[0083]
FIG. 9A shows a state in which the preceding paper a is nipped and transported by the transport rollers 28 and 29, and the leading end of the subsequent paper b is close to the upstream transport roller 28. The leading edge of the sheet b is positioned below the trailing edge of the preceding sheet a.
[0084]
In FIG. 9B, after the trailing edge of the preceding paper a passes through the conveyance roller 28 and the leading edge of the subsequent paper b is sandwiched between the conveyance rollers 28, the conveyance roller 28 is moved to the upper position indicated by the arrow. It has been moved. As a result, the leading edge of the succeeding sheet b moves so as to jump up above the trailing edge of the preceding sheet a.
[0085]
FIG. 9C shows a state in which the conveyance of the sheets a and b is continued while the conveyance roller 28 is moved to the upper position, and the leading end of the subsequent sheet b is in contact with the outer peripheral surface of the conveyance roller 29.
[0086]
FIG. 9D shows a state in which the transport roller 28 is returned to the original lower position as indicated by an arrow. The leading edge of the succeeding sheet b is nipped by the conveying roller 29, and the sheets a and b that have passed through the conveying roller 29 are arranged so that the preceding sheet a is on the lower side and the succeeding sheet b is on the upper and lower sides when superimposed. The positional relationship is controlled.
[0087]
FIG. 10 shows a case where the leading edge of the succeeding paper b is close to the transport roller 28 and the leading edge of the paper b is located above the trailing edge of the preceding paper a.
[0088]
Also in this case, after the trailing edge of the preceding sheet a passes through the conveying roller 28 and the leading edge of the succeeding sheet b is sandwiched between the conveying rollers 28, the conveying roller 28 is moved to the upper position indicated by the arrow. (FIG. 10 (b)), then, by returning the conveying roller 28 to the original lower position (FIG. 10 (d)), the sheets a and b that have passed the conveying roller 29 have the preceding sheet a on the lower side. The vertical positional relationship at the time of superposition is controlled so that the succeeding paper b is on the upper side.
[0089]
  Next, the first of the present invention4The embodiment will be described with reference to FIGS. 11 and 12. FIG. The basic structure of this embodiment is the above-mentioned first structure.3This is the same as the embodiment. The difference is that the control of the positional relationship between the front and rear sheets a and b is performed so that the preceding sheet a is on the upper side and the succeeding sheet b is on the lower side.
[0090]
FIG. 11A shows a state in which the preceding paper a is nipped and transported by the transport rollers 28 and 29, and the leading end of the subsequent paper b is close to the upstream transport roller 28. The leading edge of the sheet b is positioned above the trailing edge of the preceding sheet a.
[0091]
In FIG. 11B, after the trailing edge of the preceding paper a passes through the conveyance roller 28 and the leading edge of the succeeding paper b is sandwiched between the conveyance rollers 28, the conveyance roller 28 is moved to a lower position indicated by an arrow. It has been moved. As a result, the leading edge of the succeeding sheet b moves below the trailing edge of the preceding sheet a.
[0092]
FIG. 11C shows a state in which the conveyance of the sheets a and b is continued while the conveyance roller 28 is moved to the lower position, and the leading end portion of the subsequent sheet b is in contact with the outer peripheral surface of the conveyance roller 29.
[0093]
FIG. 11D shows a state in which the transport roller 28 is returned to the original upper position as indicated by an arrow. The leading edge of the succeeding sheet b is nipped by the conveying roller 29, and the sheets a and b that have passed through the conveying roller 29 are arranged so that the preceding sheet a is on the upper side and the succeeding sheet b is on the lower side. The positional relationship is controlled.
[0094]
FIG. 12 shows a case where the leading edge of the succeeding paper b is close to the transport roller 28 and the leading edge of the paper b is located below the trailing edge of the preceding paper a.
[0095]
Also in this case, after the trailing edge of the preceding paper a passes through the conveyance roller 28 and the leading edge of the subsequent paper b is sandwiched between the conveyance rollers 28, the conveyance roller 28 is moved to a lower position indicated by an arrow. (FIG. 12 (b)), and then returning the transport roller 28 to the original upper position (FIG. 12 (d)), the sheets a and b that have passed the transport roller 29 are the preceding sheet a on the upper side and the succeeding sheet a. The vertical positional relationship at the time of superimposition is controlled so that the paper b is on the lower side.
[0096]
  Next, the first of the present invention5The embodiment will be described with reference to FIGS. 13 and 14. FIG. In the present embodiment, an outer guide plate 30 and an inner guide plate 31 that are curved in an arc are disposed on the sheet conveyance path 4 between the registration roller 18 and the sync roller 20 so as to face each other. A portion where the outer guide plate 30 and the inner guide plate 31 which are a part of the sheet conveyance path 4 are opposed to each other is a detection path 32 for detecting the leading edge and the trailing edge of the sheet. The detection path 32 is formed in such a shape that a step is generated in the transport path cross-sectional direction between the front end side and the rear end side of the transported paper.
[0097]
At a position outside the outer guide plate 30 and in the vicinity of the sync roller 20, a leading edge detection sensor 33, which is a sheet edge detection means, is disposed. Further, a rear end detection sensor 34 serving as a sheet end detection unit is disposed outside the inner guide plate 31 and in the vicinity of the sync roller 20.
[0098]
The front end detection sensor 33 and the rear end detection sensor 34 are sensors having characteristics shown in the drawings, and correspond to, for example, a reflective photosensor.
[0099]
In such a configuration, (1) is a state in which the leading edge of the preceding paper has reached between the registration roller 18 and the sync roller 20. In this state, the sheet tries to return straight due to its own restoring force, and the leading edge of the sheet advances along the inner peripheral surface of the outer guide plate 30 and passes through the detection range of the leading edge detection sensor 33. Tip detection is performed.
[0100]
(2) is a state in which the paper has progressed from the state of (1) described above, and the leading edge of the paper has advanced to a position just before the synchro roller 20. At this time, the paper advances along the outer guide plate 30, but the distance from the leading edge detection sensor 33 is slightly longer than in the state of (1). Therefore, when the output of the tip detection sensor 33 is an analog value, the output level is lowered.
[0101]
(3) is a state in which the leading end side of the sheet is sandwiched by the sync roller 20, and the conveying force for the sheet is given by the sync roller 20 and the registration roller 18. At this time, by temporarily increasing the rotation speed of the registration roller 18, the sheet between the registration roller 18 and the sync roller 20 is moved toward the inner guide plate 31. As a result, the sheet enters the detection range of the trailing edge detection sensor 34, and the output of the trailing edge detection sensor 34 increases. On the other hand, the sheet falls outside the detection range of the leading edge detection sensor 33, and the output becomes zero.
[0102]
(4) is a state in which the rear end of the paper passes through the registration roller 18 and becomes free, the rear end advances while sliding on the inner peripheral surface of the outer guide plate 30, and returns straight due to its own restoring force. is there. The sheet is located within the detection range of the trailing edge detection sensor 34, and the output level of the trailing edge detection sensor 34 is maintained at a high level.
[0103]
(5) is the state immediately before the trailing edge of the sheet passes the trailing edge detection sensor 34. At the same time as the trailing edge of the sheet passes the position of the trailing edge detection sensor 34, the output level of the trailing edge detection sensor 34 becomes zero.
[0104]
FIG. 9 is a timing chart showing output levels of the leading edge detection sensor 33 and the trailing edge detection sensor 34 when three sheets are conveyed while overlapping a part of the front and rear sheets.
[0105]
According to the present embodiment, the front end detection sensor 33 provided in the direction in which the level difference of the paper is generated in the path in which the level of the transported paper has a step in the cross section direction of the transport path between the front end side and the rear end side, and the rear. By providing the edge detection sensor 34, even if the paper is transported in a state of being partially overlapped, the paper superimposed at the position of the leading edge detection sensor 33 and the trailing edge detection sensor 34 is vertically moved. They can be separated, and the leading edge and the trailing edge of each sheet can be detected.
[0106]
In this embodiment, the case where one leading edge detection sensor 33 and one trailing edge detection sensor 34 are provided has been described as an example. However, such sensors 33 and 34 are provided along the sheet conveyance direction. Thus, by calculating from the outputs from the sensors 33 and 34, it is possible to detect the occurrence of slipping of the conveyed paper and to detect the occurrence of jamming.
[0107]
  Next, the first of the present invention6The embodiment will be described with reference to FIGS. 15 and 16. FIG. 15 is an explanatory diagram for explaining the premise of the present invention. As shown in FIG. 15A, when two sheets of paper are conveyed while being partially overlapped and image formation is performed, the image is transferred from the photosensitive drum 9 to the paper at the edge of the overlapping area of the paper. A part of the toner image to be transferred becomes defective in transfer and an image missing portion is likely to occur. This is because the lower sheet, which is the edge of the overlapping portion of the sheets, is not sufficiently brought into contact with the photosensitive drum 9.
[0108]
When such an image missing portion is generated, when one sheet is formed by joining sheets that have been transported in a superimposed state and subjected to image formation, an image that is difficult to see due to the presence of the image missing portion is obtained.
[0109]
On the other hand, in the present embodiment, as one of the processes executed by the control unit that controls the image forming operation or the like in the image forming unit 2, an image in the vicinity of the superimposed portion of the paper that is conveyed in a superimposed manner is displayed. Means are provided for overlapping the front and rear sheets.
[0110]
In such a configuration, when image formation is performed on the front and rear sheets that are transported with a part thereof being superimposed, as shown in FIGS. 16A and 16B, the front and rear sheets (preceding sheets and succeeding sheets) are used. ), An image in the vicinity of the superimposition area (superimposition area image) is formed in an overlapping manner.
[0111]
Thus, when the sheets conveyed in the superimposed state are joined after the image formation to form one image, as shown in FIG. It is possible to obtain a continuous image without image loss.
[0112]
  Next, the first of the present invention7The embodiment will be described with reference to FIG. In the present embodiment, as one of the processes executed by the control unit that controls the image forming operation or the like in the image forming unit 2, an image (overlapping image region) that shows an area of an image that is overlapped on the preceding and following sheets. A means for forming a boundary mark is provided.
[0113]
In such a configuration, when overlapping image areas are formed on two overlapping sheets, overlapping image area boundary marks are formed on those sheets. As a result, when the sheets are joined to form a single image, the joining position can be easily confirmed, and the work of joining the two sheets can be performed easily and accurately. Can do.
[0114]
In the present embodiment, the case where a superimposed area image is formed on two superimposed sheets has been described as an example. However, when such a superimposed area image is not formed, the sheet is simply superimposed. Forming means for forming an image (mark) indicating a region may be provided. This means is also one of the processes executed by the control unit that controls the image forming operation and the like in the image forming unit 2.
[0115]
  Next, the first of the present invention8The embodiment will be described with reference to FIG. In the present embodiment, a sheet interval securing unit for securing the interval between sheets ejected from the image forming unit 2 is provided. This sheet interval securing means is one of the processes executed by the control unit that controls the image forming operation and the like in the image forming unit 2.
[0116]
In such a configuration, with respect to the sheet conveyance speed “V4” in the image forming unit 2, the sheet conveyance speed “V5” after the trailing edge of the sheet passes through the fixing device 11 is set to “V4 <V5”. As a result, the interval between the sheets discharged from the image forming unit 2 can be secured.
[0117]
Even when the front and rear sheets are transported through the image forming unit 2 with no gap between them, or when the front and rear sheets are transported through the image forming unit 2 with a part of them superimposed, By securing the interval between the sheets when the sheets are discharged from the image forming unit 2, the post-processing performance can be improved when the discharged sheets are post-processed by a finisher or the like. The sheets to be printed can be accurately stacked in the order in which they are discharged.
[0118]
【The invention's effect】
  According to the image forming apparatus of the first aspect of the present invention, the sheet that is switched back and sent out from the reversing path is fed to the front and rear sheets by the sheet interval control means.Some overlapIs sent to the image forming unit.Part of it was superimposedImage formation is performed in the state, and productivity of image forming work can be increased. When the paper fed into the reversing path is switched back, the switch is controlled by controlling the paper feeding speed to the reversing path, the paper feeding speed from the reversing path, the paper feeding timing from the reversing path, etc. The interval between the backed sheets can be reduced, and by providing such a reversing path and sheet reversing means to reduce the distance between the front and back sheets in advance, the sheet spacing control means can reduce the distance between the front and back sheets.Superimpose a partControl can be performed with high accuracy.And since it has a vertical position control means that can control the vertical position relationship of the superimposed paper both on the upper side and the lower side of the preceding paper, the vertical position of the paper before and after overlapping a part of the paper The relationship can be maintained in the intended positional relationship, and stable image formation can be performed on the paper fed into the image forming unit in a state where a part of the paper is superimposed.
[0121]
  Claim2According to the described invention, the claims1In the image forming apparatus described above, by changing the paper feed start timing, PaintingThe interval between the front and back sheets can be controlled so that a part of the front and back sheets fed to the image forming unit is overlapped.
[0122]
  Claim3According to the described invention, the claims1In the image forming apparatus described above, by varying the paper conveyance speed, PaintingThe interval between the front and back sheets can be controlled so that a part of the front and back sheets fed to the image forming unit is overlapped.
[0124]
  Claim4According to the described invention, claims 1 to3In the image forming apparatus according to any one of,in frontSince it has a paper edge detecting means for detecting the leading edge and the trailing edge of the paper conveyed in a state where a part of the subsequent paper is overlapped,,in frontEven if the paper is transported in a state where a part of the subsequent paper is superimposed, the leading edge and the trailing edge of the paper can be detected, and various controls can be performed at the timing based on the detection result.
[0125]
  Claim5According to the described invention, the claims4In the image forming apparatus described above, a detection path is provided such that a step is generated in a cross-sectional direction of the transport path between the front end side and the rear end side of the transported sheet, and the sheet detection unit is configured to detect the sheet in the detection path. Because it is a detection sensor provided in the direction that can be stepped,in frontWhen the paper with a part of the subsequent paper superimposed is transported through the detection path, a difference in level occurs between the leading edge and the trailing edge of the paper. The front end and the rear end can be detected by a detection sensor.
[0126]
  Claim6According to the described invention, the claims1Or5In the image forming apparatus according to any one of the above, since there is means for overlappingly forming an image in the vicinity of the overlapping portion of the sheet to be conveyed in an overlapping manner on the preceding and succeeding sheets, an image is missing in the vicinity of the overlapping portion of the sheet Even when the image is formed, the images formed by overlapping the images formed on the front and rear sheets are overlapped when the sheets on which the images have been formed are joined together to form one image. It is possible to obtain a continuous image with no missing portions.
[0127]
  Claim7According to the described invention, the claims1Or6In the image forming apparatus according to any one of the above, since the image forming apparatus includes an image forming unit that forms an image that indicates an overlapped area of the sheet that is conveyed in an overlapping manner, Thus, it is possible to easily check the overlapped portion of the conveyed paper.
[0128]
  Claim8According to the described invention, the claims6In the image forming apparatus described above, there is means for forming an image showing an area of an image formed on the preceding and succeeding sheets, so that an image in the vicinity of the overlapping portion is formed on two overlapping sheets. By looking at the image showing the overlapping image area, it is possible to easily check the position where the sheets are joined when the sheets are joined to form one image. The operation of joining sheets can be performed easily and accurately.
[0129]
  Claim9According to the described invention, claims 1 toAny one of 8The image forming apparatus described above includes a sheet interval securing unit that secures an interval between sheets ejected from the image forming unit.,in frontEven when the subsequent paper is transported in the image forming unit with a part of it overlapped, the interval between the papers can be secured when the paper is discharged from the image forming unit, It is possible to improve workability when stacking or post-processing sheets discharged from the image forming unit.
  According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the paper fed into the reversing path is switched back and sent out to the paper conveying path, and from the reversing path. An open state in which at least a part of the preceding sheet being fed and the succeeding sheet fed to the reversing path is allowed to overlap can be switched only by the rotation of the notch driving roller.
  According to the eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, skew correction of the paper that is switched back by the paper reversing means and sent to the paper conveyance path is performed in the reversing path. Therefore, stable image formation can be performed, and the space for the image forming apparatus can be saved.
[Brief description of the drawings]
FIG. 1 shows the first of the present invention.referenceFIG. 2 is a schematic diagram showing the overall structure of the image forming apparatus in the embodiment.
FIGS. 2A and 2B are enlarged schematic views showing a sheet reversing unit, in which FIG. 2A shows an open state and FIG. 2B shows a sheet feeding state;
FIG. 3 is an explanatory diagram illustrating a sheet conveyance state by a sheet reversing unit.
FIG. 4 is a diagram illustrating a sheet conveyance state.
FIG. 5 shows the second of the present invention.reference6 is a diagram showing a sheet conveyance state in the form of.
FIG. 6 shows a third embodiment of the present invention.reference6 is a diagram showing a sheet conveyance state in the form of.
FIG. 7 shows the first of the present invention.16 is a diagram illustrating a sheet conveyance state in the embodiment.
FIG. 8 shows the first of the present invention.26 is a diagram showing a sheet conveyance state in the embodiment.
FIG. 9 shows the first of the present invention.3It is explanatory drawing explaining the control method of the vertical position relationship of the front and back paper in the embodiment.
FIG. 10 is also an explanatory diagram for explaining a control method of a vertical positional relationship between front and rear sheets.
FIG. 11 shows the first of the present invention.4It is explanatory drawing explaining the control method of the vertical position relationship of the front and back paper in the embodiment.
FIG. 12 is also an explanatory diagram for explaining a control method of the vertical position relationship between the front and rear sheets.
FIG. 13 shows the first of the present invention.5It is the schematic which shows embodiment of this.
FIG. 14 is a timing chart illustrating an output state of a sensor that detects a leading edge and a trailing edge of a sheet.
FIG. 15 shows the first of the present invention.6FIG. 9 is a diagram illustrating a premise of the embodiment, and is an explanatory diagram for explaining that an image missing portion is generated when an image is formed on a partially overlapped sheet.
FIG. 16 shows the first of the present invention.6FIG. 6 is an explanatory diagram illustrating a state in which an image in the vicinity of a sheet overlap portion is formed on the preceding and succeeding sheets in the embodiment.
FIG. 17 shows the first of the present invention.7It is a perspective view which shows this embodiment.
FIG. 18 shows the first of the present invention.86 is a diagram illustrating a sheet conveyance state in the embodiment.
[Explanation of symbols]
  1 Paper storage
  2 Image forming unit
  4 Paper transport path
  8 Separation paper feeding means
  21 Inversion road
  22 Paper reversing means
  32 Detection path
  33, 34 Paper detection means, detection sensor

Claims (11)

In an image forming apparatus in which sheets stacked and held in a sheet storage unit are separated and fed one by one by a separation feeding unit, and image formation is performed on the fed sheets by an image forming unit.
A reversing path that is connected in the middle of the sheet conveying path from the sheet storing section to the image forming section and into which the sheet conveyed through the sheet conveying path is sent;
At least a part of the feeding state in which the sheet sent to the reversing path is switched back and sent to the sheet conveying path, and the preceding sheet fed from the reversing path and the succeeding sheet fed to the reversing path are A paper reversing means switchable to an open state allowing the superposition;
A sheet interval control means for superimposing a part of the sheet before and after being fed into the image forming unit;
Vertical position control means for controlling the vertical positional relationship of the paper before and after a part of which is superimposed;
HaveAnd
The vertical position control means is
Comprising two pairs of transport rollers provided between the image forming unit on the paper transport path and the reversing path;
The two pairs of transport rollers have a cross section perpendicular to the rotation axis of each transport roller. Before and after controlling the positional relationship, they are arranged so as to be substantially on the same plane,
The control of the vertical position relationship between the front and rear papers is the state in which the papers are moved in opposite directions perpendicular to the superimposed surface so that any paper can be deformed and the edges can be replaced with each other. The conveying roller pair provided on the upstream side is in a cross section perpendicular to the rotation axis between the conveying roller pair provided on the upstream side and the overlapped portion between the downstream conveying roller pair. The following paper is controlled by reciprocating in the order from the top to the bottom in the direction connecting the opposite rotating shaft cores, and the following paper is controlled by reciprocating in the order from the bottom to the top.Image forming apparatus. The sheet interval control means, Ri by the varying the sheet feed start timing, the image forming apparatus according to claim 1, characterized in that for controlling of superimposing a portion of the front and rear sheets. The sheet interval control means, Ri by the varying the transport speed of the sheet, the image forming apparatus according to claim 1, characterized in that for controlling of superimposing a portion of the front and rear sheets. Before After the paper tip and an image forming apparatus according to any one of claims 1 to 3, characterized in that it has a paper edge detecting means for detecting the trailing edge to be conveyed in a state overlapped with the portion of the sheet . A detection path is provided such that a step is generated in the cross-sectional direction of the conveyance path between the leading edge side and the trailing edge side of the conveyed sheet, and the sheet detection means is provided in a direction in which the level difference of the sheet is formed in the detection path. The image forming apparatus according to claim 4 , wherein the image forming apparatus is a detected sensor. The image forming apparatus as claimed in claims 1, characterized in that it comprises means for forming overlapping before and after the sheet image in the vicinity of the superimposed portions of the sheet transported superimposed to 5. The image forming apparatus as claimed in claims 1, characterized in that it comprises means for forming an image showing a region of the overlapping portion of the sheet conveyed superimposed to 6. 7. The image forming apparatus according to claim 6, further comprising means for forming an image indicating an area of the image formed on the front and back sheets. The image forming apparatus as claimed in claims 1, characterized in that it has a sheet spacing means to ensure the interval of sheets discharged from the image forming unit 8. The paper reversing means
A notched drive roller in which a notch is formed in a part of the outer periphery parallel to the axis and the other part of the outer periphery is a cylindrical surface;
A driven roller that is disposed at a position facing the notched drive roller across the sheet fed into the reversing path, and is in contact with the cylindrical surface portion when the notched drive roller rotates, and is driven to rotate; Prepared,
A state in which the notched driving roller is rotationally driven in the direction of feeding out the paper, abuts against the cylindrical surface portion of the notched driving roller and the driven roller, and the nipped paper is sent out from the reverse path;
The notched portion of the notched drive roller faces the driven roller, and can be switched between an open state in which a gap is formed between the notched portion of the notched drive roller and the driven roller. Item 10. The image forming apparatus according to any one of Items 1 to 9. 11. The image forming apparatus according to claim 1, wherein the reversing path is provided with a jogger that performs skew correction of the fed paper.

Images