JP2002308501A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the productivity of an image forming operation by narrowing the paper interval when performing continuous image formation, and to stably maintain the paper interval in an image forming unit constant. An image is formed. A feeding state in which a reversing path for feeding a sheet is connected in the middle of a sheet conveying path from a sheet storage unit to an image forming unit, and the sheet fed to the reversing path is switched back and sent to the sheet conveying path. A sheet reversing means 21 is provided on the reversing path, which can be switched to an open state in which at least a part of a preceding sheet fed from the reversing path and a succeeding sheet fed to the reversing path are allowed to overlap. The paper feeding variation time of the paper fed from the paper storage unit 1 and sent to the reversing path is absorbed by varying the stop time of the sheet in the reversing path, and the feeding variation of the sheet fed to the reversing path is reduced. Even if it occurs, the paper fed to the image forming unit is stably maintained at a small interval.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for improving the productivity of an image forming operation when forming a continuous image.

[0002]

2. Description of the Related Art A sheet feeding structure in a conventional image forming apparatus includes a separating sheet feeding means for separating and feeding sheets stacked and held on a sheet tray one by one, and a sheet fed and separated to an image forming section. In general, the paper feed path is configured to include a paper transport path conveyed toward the paper, a transport roller disposed on the paper transport path, a registration roller disposed immediately before the image forming unit on the paper transport path, and the like.

The paper separated and fed by the separation paper feeding means is conveyed through a paper conveyance path, temporarily stopped at a position where it comes into contact with a registration roller, and is image-formed at a timing when an image is formed at an appropriate position on the paper. It is sent to the forming unit.

When two sheets are fed to the image forming section in an overlapping state, one image is formed over two sheets, or the sheet size detecting sensor detects that the sheet size is abnormal. And the image forming operation is interrupted.

Therefore, when image formation is performed continuously, it is necessary to widen the interval between the front and rear sheets in order to prevent the sheets fed to the image forming section from overlapping, and to separate and feed the sheets. . Specifically, in the conventional image forming apparatus, image forming is performed in consideration of slippage during separation paper feeding by the separation paper feeding unit, aging of the paper conveyance speed and environmental change, and variation in stoppage time for registration. Is continuously set between 40 mm and 200 mm.
Paper is fed with a gap of mm. For this reason, when image formation is performed continuously, the time during which image formation is not actually performed is lengthened, and the productivity of image formation work is reduced.

Further, an intermediate transfer member 101 as shown in FIG.
In the image forming apparatus provided with, the paper separated and fed from the paper tray 102 is conveyed toward the image forming unit 103,
The image formed by each image forming unit 104 in the image forming unit 103 is transferred onto the intermediate transfer body 101, and the intermediate transfer body 10
The image on 1 is transferred to a sheet by the transfer unit 105. The sheet on which the image has been transferred is subjected to a fixing process in a fixing unit 106, and is discharged to a discharge tray 107.

[0007] The image formed by each image forming unit 104 is formed by a sheet separated and fed from the sheet tray 102.
It starts after it is detected at 08. The paper is
Immediately after the detection by the registration sensor 108, the sheet is brought into contact with the registration roller 109 and stopped.

In the image forming apparatus provided with such an intermediate transfer member 101, the image formed by each image forming section 104 is transferred onto the intermediate transfer member 101 after a predetermined distance "LD" has progressed. The registration roller 109 is driven at the timing when the image on the intermediate transfer body 101 has advanced to a predetermined position along the rotation direction (the direction of the arrow a) of the intermediate transfer body 101, and the conveyance of the sheet is restarted. As a result, the image on the intermediate transfer body 101 is transferred to a sheet.

Here, assuming that the distance from the registration roller 109 to the transfer unit 105 is “LR”, the paper stopped at a position where the leading end thereof is in contact with the registration roller 109 is conveyed toward the paper transfer unit 105. Is a time required for the image to travel the distance of “LD + LT−LR” after the image formation in the image forming unit 104 is started. Then, it is necessary to wait at the position where the sheet abuts on the registration roller 109 for each time for each sheet, so that the interval between the sheets passing through the transfer unit 105 increases, and the productivity of the image forming operation decreases.

As one method for improving the productivity of the image forming operation in the image forming apparatus having such an intermediate transfer member 101, an image is formed by the image forming section 104 before the sheet reaches the position of the registration sensor 108. It is conceivable that the stop time of the sheet at the position of the registration roller 109 is shortened in advance. However, in this case, the paper tray 10
The paper conveyed separately from the paper tray 2 tends to have a variation in the paper feed timing, and the paper conveyed on the long path from the paper tray 102 to the registration roller 109 is not transferred to the registration roller 109 due to the aging of the conveyance speed and environmental fluctuation. Due to the large variation in the time required for the sheet to arrive, the sheet is not transferred to the registration roller 1 by the set timing.
09, and the image transfer position to the sheet is likely to be shifted or jammed. For this reason, when this method is adopted, the safety factor for the delay of the timing at which the sheet arrives at the registration roller 109 must be taken into consideration, and the sheet interval before and after passing through the transfer unit 105 is made too small. Can not do. That is, this method cannot significantly improve the productivity of the image forming operation.

In an image forming apparatus using the intermediate transfer body 101 or another image forming apparatus not using such an intermediate transfer body, another method for improving the productivity of the image forming operation is as follows. It is conceivable to increase the transport speed of the paper when passing through the location. However, in an image forming apparatus employing a digital electrophotographic image forming unit, since the rotation speed of the polygon mirror of the digital writing means has an upper limit, the rotation speed of the polygon mirror is increased to increase the productivity of the image forming operation. That has its limits. That is, this method cannot significantly improve the productivity of the image forming operation.

In an image forming apparatus using an electrophotographic image forming section, if the interval between sheets before and after being conveyed for continuous image formation is large, the image forming section is located at the position of the sheet interval. The idle operation time becomes longer. Even during such an idling operation, the deterioration of the image forming unit proceeds. Therefore, if the interval between the sheets is increased and the idling operation time is extended, the life of the image forming apparatus is reduced to the original number of usable prints or less.

SUMMARY OF THE INVENTION It is an object of the present invention to increase the productivity of an image forming operation by narrowing the paper interval when continuous image formation is performed, and to maintain a constant image interval in the image forming section to obtain a stable image. Is to perform the formation.

[0014]

According to the first aspect of the present invention,
In the image forming apparatus, the sheets stacked and held in the sheet storage unit are separated and fed one by one by a separation feeding unit, and an image is formed on the fed sheet by the image forming unit. A reversing path, which is connected in the middle of the paper transport path to the image forming section and into which the paper conveyed through the paper transport path is fed, and a feed-out in which the paper fed to the reverse path is switched back and sent out to the paper transport path. State, and a sheet reversing means that can be switched to an open state that allows at least a part of a preceding sheet fed from the reversing path and a subsequent sheet fed to the reversing path to overlap with each other, The feeding variation time of the paper fed from the paper storage unit to the reversing path is absorbed by changing the stop time of the sheet in the reversing path.

In the present invention and other inventions, the paper feed variation time is a value obtained by dividing a paper feed variation amount of a sheet fed so as to be fed into a reversing path by a paper feed linear speed of the sheet. .

Therefore, in the paper storage section, the paper separated and fed one by one by the separation paper feeding means is transported in the paper transport path, and the paper transported in the paper transport path is sent to the reversing path, where Is temporarily stopped by the sheet reversing means, sent out from the reversing path to the image forming section, and the image is formed on the sheet sent to the image forming section.

When the sheet fed into the reversing path is switched back, by controlling the speed of feeding the sheet to the reversing path, the speed of feeding the sheet from the reversing path, the timing of feeding the sheet from the reversing path, and the like, The interval between sheets that are switched back and sent to the image forming unit can be reduced.

When the sheet fed into the reversing path is switched back and sent to the image forming section, the sheet feeding variation time of the sheet fed from the sheet storage section to the reversing path is determined by stopping the sheet feeding in the reversing path. By absorbing the ink by changing the time, the paper fed to the image forming unit can be stably maintained at a small interval.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the sheet is arranged at a connection point between the sheet transport path and the reversing path, and allows the sheet to be sent to the reversing path. A switching claw for switching the sheet sent from the reversing path to allow the sheet to be conveyed to the image forming section toward the image forming section; and a conveying force for nipping the sheet sent from the reversing path. And a pre-registration roller for applying a mark, T is the sheet interval time between the front and rear sheets, L is the sheet length, D is the distance from the switching claw to the sheet reversing means, and D is the sheet feeding fed to the reversing path. The linear velocity is V1, the distance from the leading edge of the sheet stopped in the reversing path to the pre-registration roller is E, the reversing linear velocity of the sheet sent out from the reversing path is V2, and the sheet fed into the reversing path. When the paper feed variation time t, the stop time of the sheet in the reversing path and the A, t <A = T-
(LD) / V1−E / V2, the positions of the switching claw, the sheet reversing means and the pre-registration roller,
The paper feed linear speed and reverse linear speed were set.

Therefore, it is possible to clarify various conditions required for absorbing the paper feed variation time “t” with the stop time “A”.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a sheet interval time between the first sheet and the second sheet fed to the reversing path during continuous image formation is set. The time interval between the second and subsequent sheets and the subsequent sheet is set to be shorter than the sheet interval time.

Therefore, the stop time "A" of the second and subsequent sheets can be made longer, and even if the paper feed variation time "t" becomes longer, the paper feed variation time "t" is absorbed. The paper fed to the image forming unit can be stably maintained at a small interval.

The invention according to claim 4 is the invention according to claims 1 to 3
In the image forming apparatus according to any one of the above, the separation sheet feeding unit is controlled such that the leading end of a subsequent sheet reaches the sheet reversing unit immediately after the sheet reversing unit is opened.

Therefore, the stop time "A" of each sheet can be made longer, and even if the paper feed variation time "t" becomes longer, the paper feed variation time "t" can be absorbed. .

[0025] The fifth aspect of the present invention provides the first to fourth aspects.
In the image forming apparatus according to any one of the above, the image forming unit is an electrophotographic image forming unit.

Therefore, in the image forming apparatus using the electrophotographic image forming section, the idle operation time can be shortened and the life of the image forming apparatus can be extended.

The invention according to claim 6 is the invention according to claims 1 to 4
In the image forming apparatus according to any one of the above, the image forming unit is a digital electrophotographic image forming unit including a digital writing unit.

Therefore, in an image forming apparatus using a digital electrophotographic image forming section provided with digital writing means, the productivity of the image forming operation can be increased without increasing the rotation speed of the polygon mirror.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One 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 an explanatory diagram illustrating a part of the image forming apparatus in a state in which a sheet is conveyed, and FIG. FIG. 4 is a diagram showing a sheet conveyance state during continuous image formation.

As shown in FIG. 1, the image forming apparatus includes:
A paper tray 1 serving as a paper storage unit in which paper is stacked and held;
A digital electrophotographic image forming unit 2 for forming an image on the fed paper, a paper discharge tray 3 for discharging the paper on which the image has been formed, and the like are provided. Further, the image forming apparatus is provided with a paper path through which the paper fed from the paper tray 1 reaches the paper output tray 3 via the image forming unit 2. A portion from the image forming section 2 to the image forming section 2 is a sheet transport path 4.

The paper tray 1 is provided with a pickup roller 5 for feeding out the stacked and held papers, and a FRR type separation paper feed roller 6 for separating the papers sent out by the pickup roller 5 one by one. Paper feeding means 7 is provided.

The image forming section 2 has four image forming sections 8 for forming images of different colors (yellow, magenta, cyan, and black), and the images formed by these image forming sections 8 are transferred. An intermediate transfer body 9 on which image formation is performed, a transfer unit 10 for transferring an image formed on the intermediate transfer body 9 to a sheet, a fixing unit 11 for fixing an image transferred on the sheet, and the like are provided. I have. Each of the four image forming units 8 includes a digital writing unit 8a.

On the paper transport path 4, a transport roller 12, an entrance sensor 13, a pre-registration roller 14, a pre-registration sensor 15, a registration sensor 16, a registration roller 17 and the like are arranged. Further, a reversing path 18 into which the sheet conveyed through the sheet conveyance path 4 is fed is connected to a portion between the conveyance roller 12 and the pre-registration roller 14 in the sheet conveyance path 4. At the connection point between the paper transport path 4 and the reversing path 18, an inlet roller 19 that is driven to rotate in a direction to feed the paper into the reversing path 18, and a spring (not shown)
And a switching claw 20 urged in a direction to be pressed against the outer peripheral surface of the entrance roller 19. The paper fed from the paper tray 1 is supplied to the entrance roller 19 and the switching claw 20.
And is sent to the reversing path 18.

A paper reversing means 21 is provided on the reversing path 18. The sheet reversing means 21 switches back the sheet fed to the reversing path 18 to switch the sheet
And the open state in which the preceding sheet fed from the reversing path 18 and the subsequent sheet fed into the reversing path 18 are allowed to overlap each other.

As shown in FIG. 3, the sheet reversing means 21 is provided movably at a position where the driving roller 22 is driven to rotate by a motor (not shown). And a driven roller 23 that is rotated during contact. One end of the driven roller 23 is connected to the other end of the link 25 supported by the fulcrum 24, and the link 25 pivots around the fulcrum 24 to move toward and away from the drive roller 22. A spring 26 and a solenoid 27 are connected to a substantially central portion of the link 25. The spring 26 urges the link 25 in a direction in which the driven roller 23 comes into contact with the drive roller 22, and the solenoid 27 urges the link 25 in a direction in which the driven roller 23 is separated from the drive roller 22.

FIG. 3B shows that the sheet held between the driven roller 22 and the driven roller 23 is inverted by the driven roller 23 contacting the driving roller 22 and the driving roller 22 being driven to rotate in the direction of the arrow. This is the state of sending out from the road 18.

FIG. 3A shows an open state in which the driven roller 23 is rotated downward by the driving of the solenoid 27 and a gap is formed between the driving roller 22 and the driven roller 23. In the open state, the paper is fed into the reversing path 18.

The image forming apparatus includes an image forming operation in the image forming section 2, a separation sheet feeding unit 7, a conveying roller 12, a pre-registration roller 14, a registration roller 17, a sheet reversing unit 21, and the like. , A control unit (not shown) for controlling according to the detection results of the pre-registration sensor 15, the registration sensor 16, other sensors, and the like.

Here, the sheets before and after the sheet is separately fed from the sheet tray 1 and sent to the reversing path 18 or the reversing path 1
8, the sheet interval time of the sheet before and after the sheet is sent out from the sheet feeding unit 8, the sheet length is L, the distance from the switching claw 20 to the sheet reversing means 21 is D, and the linear velocity of the sheet fed to the reversing path 18 is V.
1. The distance from the leading edge of the sheet stopped in the reversing path to the pre-registration roller is E, the reversing linear velocity of the sheet sent out from the reversing path 18 is V2, and the paper feeding variation of the sheet fed into the reversing path 18 Assuming that the time is t and the stop time of the sheet in the reversing path 18 is A, t <A = T− (LD) /
The position of the switching claw 20, the sheet reversing means 21, and the pre-registration roller 14, and the sheet feed linear velocity V are set so that V1-E / V2.
1. Inversion linear velocity V2 is set. The paper feed variation time t is a value obtained by dividing the paper feed variation amount of the paper fed to the reversing path 18 by the paper feed linear velocity V1.

The sheet interval time T1 between the first sheet and the second sheet fed to the reversing path 18 during continuous image formation is determined by the sheet interval between the second sheet and the subsequent sheet. It is set smaller than the time T.

Further, the separating and feeding means 7 is controlled so that the leading end of the succeeding sheet reaches the sheet turning means 21 immediately after the sheet turning means 21 is opened.

In such a configuration, when the start key is pressed after the continuous image forming mode is set, the paper is fed from the paper tray 1 one after another. These sheets are fed to the reversing path 18 after being conveyed through the sheet conveying path 4, switched back in the reversing path 18, sent out again to the sheet conveying path 4, and conveyed to the image forming unit 2.

FIG. 2 shows a state in which a certain preceding sheet is sent out from the reversing path 18, and the leading end of the sheet is nipped by the pre-registration roller 14. At this time, immediately after the leading end of the sheet is nipped by the pre-registration roller 14, the sheet reversing means 21 is opened as shown in FIG. 3A. Further, at this time, the succeeding sheet is transported to a position where the leading end of the sheet reaches the sheet reversing means 21. For this reason, the preceding sheet sent out from the reversing path 18 and the succeeding sheet fed into the reversing path 18 travel in the reverse direction while partly overlapping in the reversing path 18.

Here, as described above, at the timing immediately after the leading end of the sheet sent out from the reversing path 18 is nipped by the pre-registration roller 14, the leading end of the succeeding sheet reaches the sheet reversing means 21. This state will be described in detail with reference to the diagram of FIG. The sheet interval time T before and after the sheet is fed into the reversing path 18 can be expressed as T = A + B + C. A is
The stop time of the sheet fed into the reversing path 18 in the reversing path 18, B is the time during which the leading edge of the sheet fed into the reversing path 18 advances from the position of the sheet reversing means 21 to the reversal stop position (= (LD) / V1), C indicates that the leading edge of the sheet fed from the reversing path 18 is
Is the time (= E / V2) until it is clamped.

By making the paper feed variation time t of the paper fed into the reversing path 18 smaller than the stop time A, the paper supply variation time can be absorbed by the stop time A, and the paper is fed into the reversal path 18. Even if the sheets to be printed vary, the feeding of the sheets from the reversing path 18 to the image forming section 2 can be stably maintained at a small interval.

Thus, even if the image forming apparatus is provided with the intermediate transfer member 9 which starts the image forming before the sheet reaches the position of the registration roller 17, the sheet is fed to the image forming section 2. It can be performed at a stable paper interval,
Stable image formation can be continuously performed.

The interval between the first sheet and the second sheet fed to the reversing path 18 during the continuous image formation is defined as T1, and the interval between the second sheet and the succeeding sheet is determined. By setting it smaller than the interval time T,
The stop time A of the second and subsequent sheets can be made longer, and even when the paper feed variation time t increases, the paper feed variation time t can be absorbed. Paper can be stably maintained at a small interval.

Note that the leading end of the sheet stopped in the reversing path 18 may have variations. In such a case, as shown in the diagram of FIG. 5, by stopping the pre-registration roller 14 at the timing when the sheet is detected by the pre-registration sensor 15, the variation can be absorbed.

In the present embodiment, the driving roller 22
The sheet reversing means 21 provided with a mechanism for bringing the driven roller 23 into contact with the driven roller 23 has been described as an example. Instead of such a sheet reversing means 21, a sheet reversing means 28 as shown in FIG. Is also good. This sheet reversing means is fed into a reversing path 18 with a notched drive roller 31 in which a notch 29 is formed in a part of the outer peripheral part in parallel with the axis and the other part of the outer peripheral part is a cylindrical surface part 30. Drive roller 3 with notch across cut paper
The notched drive roller 3 is disposed at a position facing
And a driven roller 32 that is driven to rotate while being in contact with the portion of the cylindrical surface portion 30 during the rotation of 1. Note that a motor (not shown) that drives the notch drive roller 31 to rotate is connected to the notch drive roller 31.

According to the sheet reversing means 21, FIG.
4B, the driven roller 32 abuts against the cylindrical surface portion 30 of the notched drive roller 31, the drive roller 22 is driven to rotate in the direction of the arrow, and the paper sandwiched between the notched drive roller 31 and the driven roller 32 is removed. This is a sending state in which the sheet is sent from the reversing path 18.

FIG. 6A shows an open state in which the notch 29 of the notched drive roller 31 faces the driven roller 32 and a gap is formed between the notched drive roller 31 and the driven roller 32. In the open state, the paper is fed into the reversing path 18.

[0052]

According to the image forming apparatus of the first aspect of the present invention, the paper separated and fed from the paper storage unit and transported through the paper transport path is sent to the reverse path, and is switched back in the reverse path. When feeding the paper toward the image forming unit, the paper is switched back to the image forming unit by controlling the speed of feeding the paper to the reversing path, the speed of feeding the paper from the reversing path, the timing of feeding the paper from the reversing path, and the like. It is possible to reduce the interval between the papers to be fed, and furthermore, when the paper fed into the reversing path is switched back and fed to the image forming section, the paper feeding variation time of the paper fed from the paper storage section to the reversing path is reduced. By making the stoppage time of the sheet in the reversing path variable and absorbing it, even if the sheet fed to the reversing path has a variation in sheet feeding, the image forming unit Ri paper stably to a small spacing can be maintained to be written, the image formation on the paper narrowed sheet interval can be stably performed.

According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming apparatus is disposed at a connection point between the sheet conveying path and the reversing path, and allows the sheet to be sent to the reversing path. A switching claw for switching the sheet sent from the reversing path so as to allow the sheet to be conveyed to the image forming section toward the image forming section; and a resist for nipping the sheet sent from the reversing path to apply a conveying force. A front roller is provided, T is the interval between the preceding and following sheets, L is the length of the sheet, D is the distance from the switching claw to the sheet reversing means, V1 is the linear velocity of the sheet fed to the reversing path, E is the distance from the leading edge of the paper stopped in the path to the pre-registration roller, and V is the reversal linear velocity of the paper sent out from the reverse path
2. Assuming that the feeding time of the paper fed to the reversing path is t and the stopping time of the sheet in the reversing path is A, t <
By setting the positions of the switching claw, the sheet reversing means and the pre-registration roller, the sheet feeding linear speed, and the reversing linear speed so that A = T- (LD) / V1-E / V2, the sheet feeding is performed. Conditions necessary for absorbing the variation time “t” with the stop time “A” can be clarified.

According to the third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a sheet interval time between the first sheet and the second sheet fed to the reversing path during continuous image formation. Is set to be shorter than the sheet interval time between the second and subsequent sheets and the subsequent sheet, so that the stop time “A” of the second and subsequent sheets can be made longer, and the sheet feeding variation Even when the time “t” becomes longer, the paper feed variation time “t” can be absorbed, and the paper fed to the image forming section can be stably maintained at a small interval.

According to the fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, immediately after the sheet reversing means is opened, the leading end of a subsequent sheet is supplied to the sheet reversing means. The separation sheet feeding means is controlled so as to reach, so that the stop time "A" of each sheet can be made longer, and even if the sheet feeding variation time "t" becomes longer, the sheet feeding time becomes longer. The variation time “t” can be absorbed.

According to the fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, since the image forming section is an electrophotographic image forming section, the idle operation time can be reduced. As a result, the life of the image forming apparatus can be extended.

According to the sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the image forming section is a digital electrophotographic type image forming section having digital writing means. Thus, the productivity of the image forming operation can be increased without increasing the rotation speed of the polygon mirror.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a structure of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory view illustrating a sheet conveyance state by enlarging a part thereof.

FIGS. 3A and 3B are enlarged schematic views of the structure of the sheet reversing means, wherein FIG. 3A shows an open state and FIG.

FIG. 4 is a diagram illustrating a sheet conveyance state during continuous image formation.

FIG. 5 is a diagram showing a paper transport state in the modified example.

FIGS. 6A and 6B are schematic diagrams showing another embodiment of the sheet reversing means, wherein FIG. 6A shows an open state, and FIG. 6B shows a sheet sending state.

FIG. 7 is a schematic diagram showing the structure of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper storage part 2 Image formation part 4 Paper conveyance path 7 Separation paper supply means 8a Digital writing means 14 Pre-registration roller 18 Reversing path 20 Switching claw 21 Paper reversing means 28 Paper reversing means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H072 AB04 AB09 CA01 CB01 CB09 JA02 JA04 3F049 DA12 EA10 EA17 EA23 LA01 LB03 3F053 EA01 EB04 EC02 EC06 ED29 LA01 LB03 3F102 AA01 AB01 BA06 BA07 BA11 BB17 FA03 EB03 FA03

Claims (6)

[Claims] 1. An image forming apparatus, wherein sheets stacked and held in a sheet storage unit are separated and fed one by one by a separation feeding unit, and an image is formed on the fed sheet by an image forming unit. A reversing path, which is connected in the middle of a sheet conveying path from a sheet storing section to the image forming section, and into which a sheet conveyed through the sheet conveying path is fed; A sheet reversal switchable between a sending state for sending out to a conveyance path and an open state allowing at least a part of a preceding sheet sent out from the reversing path and a succeeding sheet sent to the reversing path to overlap. Means are provided, and the paper feed variation time of the paper fed from the paper storage unit to the reversing path is absorbed by changing the stop time of the sheet in the reversing path. An image forming apparatus comprising: 2. A sheet disposed at a connection point between the sheet transport path and the reversing path to allow a sheet to be fed into the reversing path, and a sheet sent out from the reversing path passes through the sheet transport path through the image path. A switching claw that is switched to allow the sheet to be conveyed toward the forming unit; and a pre-registration roller that applies a conveying force by nipping the sheet sent from the reversing path. The time is T, the paper length is L, the distance from the switching claw to the paper reversing means is D, the paper feed linear velocity of the paper fed into the reversing path is V1, and the paper stopped in the reversing path is V1. E is the distance from the leading edge to the pre-registration roller, V2 is the reversal linear velocity of the sheet sent out from the reversing path, t is the sheet feeding variation time of the sheet fed to the reversing path, and the stop of the sheet in the reversing path. Time Is A, the position of the switching claw, the sheet reversing means and the pre-registration roller, the sheet feeding linear velocity, and the sheet feeding speed are set so that t <A = T− (LD) / V1−E / V2. 2. The image forming apparatus according to claim 1, wherein the reverse linear velocity is set. 3. A time interval between a first sheet and a second sheet fed to the reversing path during continuous image formation,
3. The image forming apparatus according to claim 1, wherein the interval between the second and subsequent sheets is set to be shorter than the interval between the next sheet and a subsequent sheet. 4. The apparatus according to claim 1, wherein the separating and feeding unit is controlled such that the leading end of a succeeding sheet reaches the sheet turning unit immediately after the sheet turning unit is opened. 4. The image forming apparatus according to any one of claims 1 to 3. 5. The image forming apparatus according to claim 1, wherein the image forming unit is an electrophotographic image forming unit. 6. 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.