JP4354124B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus having an intermediate transfer member.
[0002]
[Prior art]
The structure of the image forming apparatus having the intermediate transfer member will be described with reference to FIGS. This image forming apparatus has four image forming units 101 for forming images of different colors (yellow, magenta, cyan, black), and images transferred by these image forming units 101 are transferred. The image is formed by the intermediate transfer member 102 on which the image is formed, the sheet transfer unit 103 that transfers the image formed on the intermediate transfer member 102 to the sheet, the fixing unit 104 that fixes the image transferred on the sheet, and the fixing unit 104. A paper discharge unit 105 for discharging the printed paper, a paper storage unit 106 for stacking and holding the paper, and the like are provided.
[0003]
Image formation in such an image forming apparatus is performed according to the procedure described below. First, the registration sensor 108 indicates that the sheets separated and fed one by one from the sheet storage unit 106 are conveyed toward the sheet transfer unit 103 and the leading end of the sheet is conveyed to the vicinity of the registration roller 107. The sheet is detected and temporarily stopped in a state where the leading end is in contact with the registration roller 107.
[0004]
After the sheet is detected by the registration sensor 108, an image forming operation in each image forming unit 101 is started, and an image formed by each image forming unit 101 is transferred onto the intermediate transfer member 102, and then on the intermediate transfer member 102. Image formation is performed. The registration roller 107 is driven at the timing when the leading edge of the image formed on the intermediate transfer member 102 reaches a predetermined position as the intermediate transfer member 102 rotates, and the leading edge is brought into contact with the registration roller 107. Then, the stopped paper is conveyed toward the paper transfer means 103, and the image formed on the intermediate transfer body 102 is transferred to the paper at the paper transfer means 103.
[0005]
The image transferred onto the sheet is fixed by the fixing unit 104, and the sheet after the fixing process is discharged to the sheet discharge unit 105.
[0006]
This image forming operation will be described in detail with reference to FIG. In each image forming unit 101, a toner image formed at a point where the predetermined dimension “LD” has progressed from the point at which image formation is started is transferred onto the intermediate transfer member 102, and image formation on the intermediate transfer member 102 is performed. Done. The image formed on the intermediate transfer member 102 advances by a predetermined distance “LT” along the rotation direction (arrow a direction) of the intermediate transfer member 102, and is then transferred to the sheet by the sheet transfer unit 103.
[0007]
Here, when the sheet is detected by the registration sensor 108 (substantially the same as when the sheet reaches the registration roller 107), and the image forming unit 101 starts image formation immediately thereafter, the sheet transfer unit from the registration roller 107 is started. When the distance to 103 is “LR” and the rotation speed of the intermediate transfer member 102, the conveyance speed of the sheet, and the like are constant, the image is “ The conveyance of the paper that has stopped at the position of the registration roller 107 after the progress of “LD + LT−LR” is resumed. Therefore, in order to perform stable paper conveyance so that the front and back sheets do not overlap during continuous image formation, it is necessary to maintain the paper interval to be equal to or greater than “LD + LT−LR”, and continuous image formation is performed. In this case, the productivity of the image forming operation is significantly reduced.
[0008]
Therefore, in order to increase the productivity of the image forming operation at the time of continuous image formation, it is conceivable to start forming an image to be formed on the paper before the paper is detected by the registration sensor 108.
[0009]
However, in this case, when a paper end (paper out state in the paper storage unit 106) occurs, the image formed on the intermediate transfer member 102 has no paper to be transferred, and therefore the image is removed from the cleaning device (not shown). ), The toner is wasted and cleaning time is wasted. At this time, a large amount of toner adhering to the intermediate transfer member 102 directly touches the sheet transfer unit 103. In the worst case, the sheet transfer unit 103 is soiled, and the next and subsequent image formations are performed. This causes the paper to become dirty.
[0010]
[Problems to be solved by the invention]
Therefore, the presence or absence of paper in the paper storage unit 106 is detected by the paper end detection unit, and control is performed so that the image forming operation in the image forming unit 101 is not started when there is no paper in the paper storage unit 106. Can be considered.
[0011]
However, as shown in FIG. 10, when the distance from the sheet storage unit 106 to the sheet transfer unit 103 is shortened by downsizing the image forming apparatus, the image A formed on the preceding sheet a is transferred to the sheet. The paper end cannot be detected by the paper end detection means 109 without approaching the position of the means 103 and after the paper a has approached the position of the paper transfer means 103.
[0012]
In the state shown in FIG. 10, when the paper end detection unit 109 detects that there is a next sheet (subsequent sheet) b, the intermediate transfer member 102 to be transferred to the preceding sheet a is used. The rear end of the image A advances from the position of the image forming means 101 to the position “LS”. That is, in the image forming apparatus shown in FIG. 10, when the paper end detection unit 109 detects that there is a succeeding sheet b, the image forming to be formed on the sheet b is started. The interval between the images formed on the upper side is increased by “LD + LS”, and accordingly, the interval between the sheets a and b before and after being conveyed must be increased by “LD + LS”. The productivity of forming operations cannot be increased so much.
[0013]
SUMMARY OF THE INVENTION An object of the present invention is to improve the productivity of image forming work during continuous image formation in an image forming apparatus having an intermediate transfer member, and to prevent unnecessary image formation on the intermediate transfer member at the paper end. That is.
[0014]
Another object of the present invention is to shorten the idle operation time and extend the life of the image forming apparatus in an image forming apparatus using electrophotographic image forming means.
[0015]
Another object of the present invention is to increase the productivity of image forming work in an image forming apparatus using digital electrophotographic image forming means equipped with digital writing means without increasing the number of rotations of the polygon mirror. is there.
[0016]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an image forming apparatus comprising: an intermediate transfer member; one or a plurality of image forming units that perform image formation on the intermediate transfer member; and an image formed on the intermediate transfer member on a sheet. A paper transfer means for transferring; a paper storage section for stacking and holding paper; a separation paper supply means for separating and feeding paper one by one from the paper storage section; and a paper for detecting the presence or absence of paper in the paper storage section An end detection unit, a sheet conveyance path from the sheet storage unit to the sheet transfer unit, an inversion path connected to the middle of the sheet conveyance path and into which the sheet conveyed through the sheet conveyance path is sent, A reversing path paper conveyance driving roller arranged in the middle of the reversing path, and a movably provided position that is in contact with and away from the driving roller. A driven roller that moves, and a moving mechanism that moves the driven roller to a position that contacts and separates from the drive roller; The paper fed into the reverse path is switched back and sent out to the paper transport path. Therefore, the sheet is held by the driving roller and the driven roller. The delivery state, When feeding subsequent paper into the reverse path Allow at least a part of the preceding sheet fed from the reversing path and the succeeding sheet fed to the reversing path to overlap. Therefore, the driving roller and the driven roller are separated from each other. A sheet reversing unit that can be switched to an open state; and an image forming operation interrupting unit that interrupts the image forming operation by the image forming unit by detecting the paper end by the paper end detecting unit.
[0017]
Therefore, the sheets stacked and held in the sheet storage unit are separated and fed one by one by the separation sheet feeding unit and conveyed through the sheet conveyance path, and the sheet is sent to the reverse path during the conveyance and switched back. The sheet thus conveyed is conveyed again through the sheet conveyance path to the position of the sheet transfer means, and the image formed on the intermediate transfer member is transferred to the sheet by the sheet transfer means.
[0018]
When the paper fed into the reversing path is switched back, it is switched back 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. Thus, the interval between the sheets conveyed to the sheet transfer means can be reduced. In other words, even when there is a variation in the timing of feeding from the paper storage unit or a variation in the conveyance speed during conveyance up to the reversing path, the conveyance of the sheet to the sheet transfer unit is accurately maintained at a small interval. Therefore, the productivity of the image forming operation at the time of continuous image formation in the image forming apparatus provided with the intermediate transfer member can be improved.
[0019]
Further, in this image forming apparatus, by providing the reversing path, it is possible to lengthen the total length of the path through which the sheet is transported between the sheet storage unit and the sheet transfer unit, and the preceding sheet is in the sheet transport path or the reversing direction. It is possible to detect the paper end of the succeeding paper before it reaches the paper transfer means while being transported on the path. Thus, even if it is detected that there is a sheet in the sheet storage unit and image formation on the sheet is started, the interval between the images before and after being formed on the intermediate transfer member can be reduced. It is possible to improve the productivity of image forming work at the time of continuous image formation. Further, when the paper end is detected by the paper end detecting means, the image forming operation is interrupted by the image forming operation interrupting means, so that wasteful image formation is performed on the intermediate transfer member at the paper end. Can not be.
[0020]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a paper near-end detection unit that detects that the remaining amount of paper in the paper storage unit has decreased, and the paper near-end detection unit. If the printer detects that the remaining amount of paper is low Image forming interval expanding means for expanding the image forming interval at the time of continuous image formation.
[0021]
Therefore, when the paper near-end detection unit detects that the remaining amount of paper in the paper storage unit has decreased, the image formation interval during continuous image formation is expanded by the image formation interval expansion unit. As a result, in an image forming apparatus using a large intermediate transfer body, it is possible to perform continuous image formation while forming a plurality of images on the intermediate transfer body until the near end of the paper is detected. It is possible to improve the productivity of the image forming operation until the near end is detected.
[0022]
After the near end of the paper is detected, the image formation interval becomes large. Therefore, it is possible to start image formation on the paper after detecting that there is paper in the paper storage section, It is possible to prevent unnecessary image formation on the transfer body.
[0023]
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a conveyance speed when the sheet is fed into the reversing path is higher than a conveyance speed of the sheet at the position of the sheet transfer unit.
[0024]
Note that the conveyance speed of the paper fed into the reversing path is preferably 10% or more higher than the conveyance speed of the paper at the location of the paper transfer means.
[0025]
Therefore, even if there is a variation in the feeding timing from the paper storage unit or a variation in the conveyance speed during conveyance to the reverse path, the trailing edge side of the preceding sheet and the trailing edge side of the succeeding sheet that has been fed (The leading end side during feeding) can be reliably overlapped in the reversing path, and the succeeding sheet is reversed at a timing when an appropriate small interval is generated between the preceding sheet and the succeeding sheet. Therefore, it is possible to surely improve the productivity of the image forming operation in the image forming apparatus including the intermediate transfer member.
[0026]
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the image forming means is an electrophotographic image forming means.
[0027]
Therefore, in the image forming apparatus provided with the electrophotographic image forming means, the same operations and effects as the invention of the image forming apparatus according to any one of claims 1 to 3 are exhibited. Further, since the sheet interval in the case of performing continuous image formation becomes narrow, the idle operation time can be shortened and the life of the image forming apparatus can be prolonged.
[0028]
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the image forming means is a digital electrophotographic image forming means provided with a digital writing means.
[0029]
Therefore, in the image forming apparatus using the digital electrophotographic image forming means provided with the digital writing means, the same operations and effects as the invention of the image forming apparatus according to any one of claims 1 to 3 are exhibited. Furthermore, the productivity of image forming work when performing continuous image formation can be increased without increasing the rotational speed of the polygon mirror used in the digital writing means.
[0030]
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, two or more image forming units that form images of different colors are juxtaposed as the image forming unit.
[0031]
Therefore, in the tandem type color image forming apparatus in which a plurality of image forming means are juxtaposed, the same operations and effects as the invention of the image forming apparatus according to any one of claims 1 to 5 are exhibited.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the structure of an image forming apparatus provided with an intermediate transfer member, FIG. 2 is a block diagram showing the electrical connection of a control system of the image forming apparatus, and FIG. 3 explains the operating state of the sheet reversing means. FIG. 4 and FIG. 5 are explanatory diagrams for explaining a sheet conveyance state during continuous image formation, and FIG. 6 is a diagram showing a sheet conveyance operation during continuous image formation.
[0033]
As shown in FIG. 1, the image forming apparatus includes four image forming units 1 for forming images of different colors (yellow, magenta, cyan, black), and images formed by these image forming units 1 are displayed. An intermediate transfer body 2 on which an image is formed by being transferred, a sheet transfer means 3 for transferring an image formed on the intermediate transfer body 2 to a sheet, a fixing means 4 for fixing an image transferred on the sheet, fixing A paper discharge section 5 for discharging the paper fixed by the means 4 and a paper storage section 6 for stacking and holding the paper are provided. Each of the four image forming means 1 is a digital electrophotographic image forming means provided with a digital writing means 1a.
[0034]
The paper storage unit 6 is provided with a separation paper feeding means 9 having a pickup roller 7 for picking up the stacked and held paper and an FRR type separation paper feeding roller 8 for separating and feeding the picked up paper one by one. It has been. Further, the paper storage unit 6 is provided with paper end detection means 10 for detecting the presence or absence of paper in the paper storage unit 6. Examples of the paper end detection means 10 include a light transmission type sensor and a sensor for detecting the paper height.
[0035]
Between the paper storage unit 6 and the paper transfer means 3, a paper transport path 11 is provided for transporting the paper separated and fed from the paper storage unit 6. A first conveyance roller 12, a second conveyance roller 13, a registration sensor 14, a registration roller 15 and the like are arranged. Further, a reversing path 16 through which a sheet conveyed through the sheet conveying path 11 is sent is connected between the first conveying roller 12 and the second conveying roller 13 in the sheet conveying path 11.
[0036]
On the reversing path 16, the paper fed into the reversing path 16 is switched back and sent out to the paper transport path 11, the preceding paper fed out from the reversing path 16 and the succeeding paper fed into the reversing path 16. Paper reversing means 17 that can be switched to an open state that allows at least a part of the paper to overlap, a paper edge detection sensor that detects an edge of the paper fed into or sent out of the reversing path 16 18 is provided.
[0037]
As shown in FIG. 3, the sheet reversing means 17 includes a driving roller 19 that is rotationally driven, a driven roller 20 that is movably provided at a position that is in contact with and away from the driving roller 19, and that is rotated at the time of contact. The moving mechanism is configured to move the roller 20 to a position in contact with or away from the driving roller 19. The moving mechanism for moving the driven roller 20 is connected to the link 22 having one end connected to the driven roller 20 and the other end rotatably supported by a fulcrum 21, and the driven roller 20 being driven by being connected to a substantially central portion of the link 22. A spring 23 that urges the roller 19 to be in contact with the roller 19, a solenoid 24 that is connected to the link 22 and urges the driven roller 20 to move away from the driving roller 19, and the like.
[0038]
In FIG. 3B, the driven roller 20 is brought into contact with the driving roller 19 by the urging force of the spring 23, and the driving roller 19 is rotationally driven in the direction of the arrow so that the driving roller 19 and the driven roller 20 are sandwiched. In this state, the sheet being fed is sent out from the reversing path 16.
[0039]
FIG. 3A shows an open state in which the driven roller 20 is rotated downward by driving the solenoid 24 and a gap is generated between the drive roller 19 and the driven roller 20. In this open state, the paper is fed into the reversing path 16.
[0040]
FIG. 2 is a block diagram showing electrical connection of the control system of the image forming apparatus. This control system is an image composed of the image forming means 1, the intermediate transfer body 2, the paper transfer means 3, the fixing means 4 and the like with respect to the control section 25 having a microcomputer configuration for intensively controlling the entire image forming apparatus. A motor driver 28 that drives a motor 27 that is connected to the forming unit 26, the separation paper feed roller 8, a motor driver 30 that drives a motor 29 that is connected to the first transport roller 12, and a motor that is connected to the second transport roller 13. Motor driver 32 for driving 31, motor driver 34 for driving motor 33 connected to registration roller 15, motor driver 36 for driving motor 35 connected to driving roller 19 of paper reversing means 17, and paper reversing means 17 Solenoid driver 37 for driving solenoid 24, paper end detection means 10, registration sensor 14, paper edge detection Capacitors 18, other actuators and sensors are connected.
[0041]
In such a configuration, when the start key is pressed after the continuous image forming mode is set, sheets are successively fed from the sheet storage unit 6 one after another. These sheets are conveyed along the sheet conveyance path 11 toward the sheet transfer means 3, and are sent to the reversing path 16 in the middle, switched back in the reversing path 16, and sent out to the sheet conveying path 11 again. Note that when the paper is separated and fed, after the paper end detection unit 10 detects that there is a sheet in the sheet storage unit 6, the image forming unit 1 starts image formation. FIG. 4 shows a state in which the first sheet (preceding sheet) a is about to be fed into the reverse path 16, and at this time, a part of the image A to be formed on the sheet a is the intermediate transfer member 2. And proceeding toward the sheet transfer means 3.
[0042]
In FIG. 5, the first sheet (preceding sheet) a is switched back by the reversing path 16 and sent out from the reversing path 16, and the second sheet (following sheet) b is fed into the reversing path 16. It is a state that is going. The leading paper a advances to a position where the leading edge of the preceding paper a contacts the registration roller 15, and the leading edge of the image A (image formed on the intermediate transfer body 2) A formed on the leading paper a It progresses to the vicinity of the transfer means 3. Further, a part of the image B formed on the succeeding paper b is formed on the intermediate transfer body 2 and proceeds toward the paper transfer means 3.
[0043]
Here, when the paper fed into the reversing path 16 is switched back, the paper feeding speed to the reversing path 16, the paper feeding speed from the reversing path 16, the paper feeding timing from the reversing path 16, and the like are controlled. By doing so, the interval between the sheets that are switched back and sent to the position of the sheet transfer means 3 can be reduced, thereby improving the productivity of the image forming operation at the time of continuous image formation. For example, as shown in the diagram of FIG. 6, the sheet is conveyed from the sheet storage unit 6 to the reversal stop position in the reversing path 16 at a high conveyance speed Va, and is sent out from the reversal stop position at a low conveyance speed Vb. Thus, the sheet interval at the position of the sheet transfer means 3 can be reduced.
[0044]
Further, in this image forming apparatus, by providing the reversing path 16, the total length of the path along which the sheet is conveyed between the sheet storage unit 6 and the sheet transfer unit 3 can be lengthened, and the preceding sheets a, b Can be detected in the paper end of the subsequent paper c before it reaches the paper transfer means 3 while it is being transported through the paper transport path 11 or the reverse path 16. As a result, even if it is detected that there is a sheet in the sheet storage unit 6 and image formation on the sheet is started, the interval between the images before and after being formed on the intermediate transfer body 2 is reduced. Therefore, the productivity of the image forming operation at the time of continuous image formation can be improved. Further, when the paper end is detected by the paper end detecting means 10, the image forming operation in the image forming means 1 can be interrupted by the image forming operation interrupting means. The image forming operation interrupting means is a function of the control unit 25 that interrupts the image forming operation in the image forming means 1 when the paper end detecting means 10 detects that the paper is not in the paper storage unit 6. . By executing the image forming operation interruption means, it is possible to prevent a wasteful image formation on the intermediate transfer body 2 at the paper end, and a wasteful image is formed on the intermediate transfer body 2. Various inconveniences such as waste of toner, waste of time for cleaning the image, and paper transfer that occurs when the image (toner image) on the intermediate transfer body 2 directly touches the paper transfer means 3 The contamination of the means 3 can be prevented.
[0045]
Next, a second embodiment of the present invention will be described with reference to FIG. The basic structure of this embodiment is the same as that of the first embodiment, and the same parts as those described in the first embodiment are denoted by the same reference numerals, and description thereof is also omitted. The difference between the present embodiment and the first embodiment is that the remaining amount of paper in the paper storage unit 6 has decreased in the paper storage unit 6, for example, 1/10 from the full state. A paper near-end detecting means 38 for detecting this is provided, and when the paper near-end detecting means 38 detects a paper near-end state, the image forming interval is enlarged to increase the image forming interval at the time of continuous image formation. Means is provided as a function of the control unit 25. Examples of the paper near-end detection means 38 include a potentiometer that detects the total thickness of the paper.
[0046]
In such a configuration, according to the image forming apparatus, when the paper near-end state is not detected by the paper near-end detection unit 38, that is, when there is a large amount of paper in the paper storage unit 6, it is formed on the intermediate transfer body 2. By reducing the interval between images to be formed, reducing the paper feed interval, and starting the image forming operation for images to be formed before detecting the presence or absence of paper, images during continuous image formation The productivity of the forming operation can be improved. In particular, by using a large intermediate transfer body 2 or the like, it is possible to effectively improve the productivity of image forming work in an image forming apparatus having a long “LT” dimension.
[0047]
When the paper near-end detection unit 38 detects that the remaining amount of paper in the paper storage unit 6 has decreased, the image formation interval during continuous image formation is expanded by the image formation interval expansion unit. As a result, as in the case described in the first embodiment, the paper end detection unit 10 detects the paper end, detects that there is a sheet in the sheet storage unit 6, and then forms the sheet on the sheet. Thus, it is possible to prevent the formation of a useless image on the intermediate transfer body 2 by starting the image formation. Accordingly, various inconveniences caused by forming a useless image on the intermediate transfer body 2, for example, waste of toner, waste of time for cleaning the image, contamination of the sheet transfer means 3, and the like can be prevented.
[0048]
【The invention's effect】
According to the image forming apparatus of the first aspect of the present invention, the paper that is separated and fed from the paper storage unit and conveyed to the paper transfer unit is transported to the paper transfer unit by switching back on the reverse path during the conveyance. Therefore, it is possible to maintain the sheet to be accurately maintained at a small interval, thereby improving the productivity of the image forming operation at the time of continuous image formation in the image forming apparatus provided with the intermediate transfer member. Furthermore, by providing the reversing path, the total length of the path through which the sheet is conveyed between the sheet storage unit and the sheet transfer unit can be increased, and the preceding sheet is conveyed through the sheet conveying path or the reversing path. Since the paper end of the succeeding paper can be detected before reaching the paper transfer means in the middle, it is possible to form an image to be formed on the paper after detecting the presence of the paper in the paper storage unit. Even when the operation is started, the interval between the images before and after being formed on the intermediate transfer member can be narrowed, and the productivity of the image forming operation at the time of continuous image formation can be improved. Moreover, when the paper end is detected by the paper end detecting means, the image forming operation is interrupted by the image forming operation interrupting means, so that no wasteful image formation is performed on the intermediate transfer member at the paper end. Various inconveniences caused by forming a useless image on the intermediate transfer member, for example, waste of toner, waste of time for cleaning the image, contamination of paper transfer means by toner, etc. Can be prevented.
[0049]
According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, the paper near-end detecting means for detecting that the remaining amount of paper in the paper storage portion has decreased, and the detection result of the paper near-end detecting means Accordingly, the image forming interval enlargement means for enlarging the image forming interval at the time of continuous image formation is provided. Therefore, until the near end of the paper in the paper storage unit is detected, image formation is performed prior to paper detection and intermediate By reducing the interval between the images formed on the transfer body, it is possible to further improve the productivity of image forming work during continuous image formation. After the paper near-end detection means detects the paper near-end, the image By increasing the formation interval and detecting that there is paper in the paper storage unit, starting image formation on the paper, It is possible not to perform unnecessary image formed on the intermediate transfer member during Paendo.
[0050]
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the conveyance speed when the paper is fed into the reverse path is higher than the conveyance speed of the paper at the position of the paper transfer means. Even if there is a variation in the timing of feeding from the storage section or a variation in the conveyance speed during conveyance up to the reversing path, the trailing edge of the preceding paper and the trailing edge of the succeeding paper (when The leading edge side of the sheet) can be reliably superimposed in the reversing path, and the succeeding sheet is sent out from the reversing path at a timing when an appropriate small interval is generated between the preceding sheet and the succeeding sheet. Thus, the productivity of the image forming operation in the image forming apparatus including the intermediate transfer member can be reliably achieved.
[0051]
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, since the image forming means is an electrophotographic image forming means, the image is provided with the electrophotographic image forming means. In the forming apparatus, the same operations and effects as the invention of the image forming apparatus according to any one of claims 1 to 3 are provided.
[0052]
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the image forming means is a digital electrophotographic image forming means having a digital writing means. The image forming apparatus using the digital electrophotographic image forming means provided has the same operations and effects as the invention of the image forming apparatus according to any one of claims 1 to 3.
[0053]
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, since two or more image forming units for forming images of different colors are juxtaposed as the image forming unit, In the tandem type color image forming apparatus in which the image forming means are juxtaposed, the same operations and effects as the invention of the image forming apparatus according to any one of claims 1 to 5 are exhibited.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the structure of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing electrical connection of a control system of the image forming apparatus.
FIGS. 3A and 3B are explanatory diagrams for explaining an operation state of the sheet reversing unit, in which FIG. 3A is an open state, and FIG.
FIG. 4 is an explanatory diagram illustrating a paper conveyance state during continuous image formation.
FIG. 5 is an explanatory diagram illustrating a paper conveyance state during continuous image formation.
FIG. 6 is a diagram showing a sheet conveying operation during continuous image formation.
FIG. 7 is a schematic diagram illustrating a structure of an image forming apparatus according to a second embodiment of the present invention.
FIG. 8 is a schematic view showing the structure of a conventional example of an image forming apparatus having an intermediate transfer member.
FIG. 9 is an enlarged view of a part thereof.
FIG. 10 is an enlarged view of a part thereof.
[Explanation of symbols]
1 Image creation means
1a Digital writing means
2 Intermediate transfer member
3 Paper transfer means
6 Paper storage
9 Separation paper feeding means
10 Paper end detection means
11 Paper transport path
16 Reverse road
17 Paper reversing means
38 Paper near-end detection means

Claims (6)

An intermediate transfer member;
One or more image forming means for forming an image on the intermediate transfer member;
Paper transfer means for transferring an image formed on the intermediate transfer member to paper;
A paper storage unit in which paper is stacked and held;
A separation sheet feeding means for separating and feeding sheets one by one from the sheet storage unit;
Paper end detection means for detecting the presence or absence of paper in the paper storage section;
A paper transport path from the paper storage unit to the paper transfer means;
A reversing path that is connected in the middle of the sheet conveying path and into which the sheet conveyed through the sheet conveying path is sent;
A driving roller for conveying the reverse path paper disposed in the middle of the reverse path;
A driven roller that is movably provided at a position that is in contact with and away from the drive roller, and that grips the paper with the drive roller at the time of contact;
A moving mechanism that moves the driven roller to a position that is in contact with and away from the driving roller;
When the paper fed to the reversing path is switched back and sent to the paper transporting path, the paper is held by the drive roller and the driven roller, and when the subsequent paper is fed to the reversing path Switching to an open state in which the driving roller and the driven roller are separated to allow at least a part of the preceding sheet fed from the reversing path and the succeeding sheet fed to the reversing path to overlap each other. Flexible paper reversing means,
An image forming operation interrupting unit configured to interrupt the image forming operation of the image forming unit by detecting the paper end by the paper end detecting unit; Paper near-end detection means for detecting that the remaining amount of paper in the paper storage section has decreased, and when the paper near-end detection means detects that the remaining amount of paper has decreased, The image forming apparatus according to claim 1, further comprising an image forming interval expanding unit that expands the image forming interval.   The image forming apparatus according to claim 1, wherein a conveyance speed when the sheet is fed into the reversing path is higher than a conveyance speed of the sheet at the position of the sheet transfer unit.   4. The image forming apparatus according to claim 1, wherein the image forming unit is an electrophotographic image forming unit.   The image forming apparatus according to claim 1, wherein the image forming unit is a digital electrophotographic image forming unit including a digital writing unit.   6. The image forming apparatus according to claim 1, wherein two or more image forming units that form images of different colors are juxtaposed as the image forming unit.

Images