JPH0859046A - Paper reversing/discharging device of image forming device - Google Patents

Abstract

PURPOSE: To enable normal conveyance even in such a condition that paper sheets pass by each other in the inside of a return passage, in an image forming device capable of forming a double side copy, when a reversing function is provided upstream of a discharge tray by utilizing the passage for conveying a single side copy to an intermediate tray. CONSTITUTION: A reversing/discharging part 30 is arranged downstream of the fixing device of an image forming device, and the device is provided with a passage for branching a paper sheet via a gate member 31 and for discharging it toward a discharge tray, a branch passage 42 for the double side copy leading to an intermediate tray through a return passage, or the like. In a return passage 35 a nip release roller device 52 capable of releasing a nip is arranged, and in a reversing passage 40 a reversing roller device 55 is arranged, so that normal and reverse driving can be given to the two roller devices 52, 55. When a following paper P2 enters the return passage in such a state that a preceding paper P1 is reversedly discharged, the nip of the nip release roller device 52 is released to permit the movement of the end part of the following paper toward the reversing passage.

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 such as an electrophotographic copying machine in which a sheet conveying path for guiding a single-sided copy sheet toward a double-sided copy function can be used as a sheet reversal discharge path. In particular, the present invention relates to a sheet reversing and ejecting apparatus of an image forming apparatus that enables easy control of the reversing and ejecting operation of a sheet when two sheets are positioned in the reversing and ejecting path.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, an image is formed only on one side of a sheet, and a copy made is ejected as it is toward an ejection tray or the like. In some cases, a device equipped with a copying function is configured. An electrophotographic copying machine provided with the automatic double-sided copying function is disclosed in, for example, Japanese Patent Laid-Open No. 5-3196.
In the image forming apparatus shown in the conventional example, a sheet conveying mechanism as shown in Japanese Patent No. 19 is constructed.
The structure is as shown in FIG. In the image forming apparatus 1 shown in FIG. 6, the paper feed trays 10 and 1
The sheet feeding devices 11 and 14 are arranged on the intermediate tray 13 and the sheet feeding device 2, respectively, and the sheet feeding path 15
It constitutes a mechanism for feeding the paper toward. In addition, the paper feed path 15 has a conveying roller device 16 at a predetermined interval.
17 and 17a are arranged so as to carry out a conveying action on the sheet. Further, a registration unit 18 is arranged at the end of the paper feed path 15 to position the leading end of the paper, and the paper feed timing is set for the toner image formed on the photosensitive drum 3. It constitutes a mechanism for sending out.

Further, as in the case of a general electrophotographic copying machine, the photosensitive drum 3 is provided with a toner image forming mechanism using an electrophotographic system, and an image of an original set on the platen 2 is written. A mechanism is provided for converting a toner image into a visible image and transferring it to a sheet. The electrophotographic copying machine is configured as an automatic double-sided copying machine, and a sheet on which a toner image is transferred from the photosensitive drum 3 is fixed by a fixing device 4 to prepare a single-sided copy, and then a single-sided copy is formed. Return path 23 through copy section 21
And a path for accommodating it in the intermediate tray 13 is provided. The branch portion 21 is disposed in the discharge path 20, and forms a branch portion between the fixing device 4 and the discharge roller 5 corresponding to the discharge tray 6 via the gate member 22.

A forward / reverse drive roller device 24 and an intermediate tray 13 are provided in a return path 23 arranged with respect to the branch portion 21.
A gate member 27 for guiding the sheet toward the sheet is disposed, a reversing path 25 is disposed under the gate member 27, and a reversing drive roller device 26 is provided in the reversing path 25. Then, in the electrophotographic copying machine, when the reverse discharge mode is set, the sheet made as a one-sided copy through the fixing device is introduced from the branching section 21 to the return path 23, and the sheet is returned. After completely entering the path, the roller device 24 is driven in the reverse direction and the gate member 22 is switched so that the sheet is ejected toward the ejection tray. On the other hand, when the double-sided copy mode is set, the sheet introduced into the return path 23 is guided to the reverse path 25 as it is, and the roller device 26 is driven in the reverse direction to move the lower part of the gate member 27. Through the discharge roller 2
Then, the sheet is discharged to the intermediate tray 13 by 8. Also, if the electrophotographic copying machine is set to the multiple copy mode,
The single-sided copy sheet is accommodated in the intermediate tray 13 from the return path 23 via the upper guide surface of the gate member 27.

In the sheet feeding path of the electrophotographic copying machine having the above-described structure, for example, in the conveying roller devices 16, 17 ... Arranged upstream of the registration section 18, it is assumed that the nip with respect to the sheet can be released. Further, a nip releasing mechanism can be provided for the forward / reverse drive roller device 24 arranged in the return path 23. For example, when the sheet introduced into the return path is reversed and discharged toward the discharge tray 6, the forward / reverse drive roller device 24 is used in a state where the leading end of the sheet to be reversed and discharged is nipped by the discharge roller 5. The nip is released so that extra stress is not applied to the discharged paper between the two roller devices, and the paper can be conveyed well. Further, in a device that performs a sheet conveying device at a high speed, as described above, while the sheet is being conveyed in the reverse direction in the reverse direction, the next sheet may be introduced into the return path. . Therefore, in the example shown in the conventional example, even if the next sheet comes into the return path while the sheet to be reversed and ejected is ejected from the return path toward the ejection tray, The paper can be continuously conveyed.

[0006]

In the reversal discharge section in the image forming apparatus as shown in the above-mentioned conventional example, after the trailing edge of the sheet inserted in the return path passes through the gate member, the sheet is returned. A conveyance mechanism is configured so that the nip release roller device provided in the path is reversely driven to guide the sheet toward the discharge roller through the discharge path. Then, in the return path arranged subsequent to the reverse discharge section, the trailing edge of the preceding sheet passes through the nip release roller device of the return path, and the succeeding sheet is detected when the timing for switching the nip release roller device to the forward direction is observed. When the sheet reaches the position of the nip release roller device, the sheet can be conveyed toward the reverse path by the normal rotation drive of the nip release roller device. However, if the size of the paper used to make a copy is large, the problem that subsequent paper may enter the return path is likely to occur during the operation of feeding the preceding paper from the return path. In particular, when the paper has a large size and when the conveyance roller device arranged in the paper conveyance path causes a slip, it is determined that two sheets pass each other at the nip release roller device arranged in the return path. May be.

As described above, when the timing of conveyance of the sheet guided to the return path is deviated, the succeeding sheet is fed by the nip release roller while the preceding sheet is being discharged by the reverse rotation of the nip release roller device. When the nip position of the apparatus is reached, a phenomenon occurs in which the leading edge of the succeeding sheet is stopped without being able to enter the nip position of the nip release roller apparatus. Then, the leading edge of the succeeding paper that tries to enter the nip position of the nip release roller device is subjected to the action of the reverse rotation of the nip release roller device and the feeding action of the roller device arranged in the upstream portion, so that the leading end of the paper is bent. Therefore, there is a concern that the subsequent paper transport operation may be affected. Therefore, in order to solve the problems described above,
For example, as shown in Japanese Unexamined Patent Publication No. 5-338892, the operation of releasing the nip of the nip release roller device arranged in the return path and the switching of the forward and reverse drive for the nip release roller device are correlated with each other. It has been proposed to perform the above operation so that the operation of reversing and ejecting the paper can be performed in a good state. And in the conventional example,
When the succeeding sheet is detected by the upstream sensor while the preceding sheet is being reversed and discharged by the reverse rotation of the nip release roller apparatus, the nip of the nip release roller apparatus is released at a predetermined timing from the detection signal. By operating the means, the operation of reversing and ejecting the paper can be easily performed.

However, in the case where the large size sheet is reversed and conveyed in the reverse discharge section as shown in the above-mentioned conventional example, the leading edge of the succeeding sheet is in the middle of the reverse discharge operation by the nip release roller device. May enter the nip position of the nip release roller device, and there remains a problem that it is not possible to prevent inconveniences such as bending the leading end of the paper. Therefore, for example, a torque limiter as shown in Japanese Utility Model Laid-Open No. 61-38169 is provided for the nip release roller device arranged in the return path, and the nip release roller device is being driven in reverse, When the succeeding paper tries to plunge into the nip position of the nip release roller device,
One solution is to allow the drive roller of the nip release roller device to rotate in the forward direction.

However, if a means for allowing the reverse rotation by following the moving direction of the succeeding sheet is provided for the nip release roller device arranged in the return path, the drive is performed against the slip of the torque limiter. In order to rotate the roller, it is necessary to configure the driving force of the motor to have a large value, which causes a problem that the configuration of the driving device becomes large. Further, even when the nip releasing mechanism is arranged for the nip release roller device, it is assumed that a state where two sheets of paper simultaneously enter the reversing roller device arranged in the reversing path at the downstream portion thereof. However, when such a state occurs, there is a problem in that the leading end portion of the succeeding paper is more likely to be damaged.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-described problem of the sheet reversing and discharging device of the conventional image forming apparatus. The nip release roller device is provided with a mechanism for releasing the nip, and the nip is released. An image that provides a mechanism for allowing the leading edge of the succeeding paper to easily enter the reversing roller device disposed downstream of the release roller device so that the paper conveying action in the reversing path can be performed in a good state. An object of the present invention is to provide a sheet reversing and discharging device of a forming apparatus.

[0011]

According to the present invention, a return path is disposed between a discharge roller of a fixing device and a discharge roller corresponding to a discharge tray via a gate member, and a reversing roller device is provided downstream of the return path. A reversing path is arranged through the sheet feeding path of the gate member, and a direct discharge path that directly connects the fixing discharge roller and the discharge roller, an introduction path that connects the fixing discharge roller and the return path, and a return path. Disposing discharge paths for connecting discharge rollers respectively, when the sheet is reversed and discharged, the sheet is guided to the return path and the reverse path through the introduction path, and then the roller device arranged in the return path is reversely driven. The present invention relates to a sheet reversing and ejecting device configured to guide a sheet toward an ejecting roller via an ejecting path. In the present invention, the roller device arranged in the return path is configured as a nip release roller device capable of forward / reverse driving and capable of releasing a nip, and a pinch roller of the nip release roller device is configured to be capable of being brought into and out of contact with a driving roller. In addition, the nip release roller device constitutes means for releasing the nip in accordance with the information of the sheet detecting means arranged at the predetermined positions of the introducing path and the reversing path, and is arranged corresponding to the reversing path. In the reversing roller device, the roller member on the side corresponding to the introduction path is a pinch roller, and the roller member on the side corresponding to the discharge path is a driving roller.

Further, in the present invention, in the reversing roller device arranged corresponding to the reversing path, the surface of the pinch roller on the side corresponding to the introducing path is made of a material having a small friction coefficient, and the paper is used as the driving roller. It is possible to configure means for exerting only the action of pressing toward. Further, in the present invention, in the reversing roller device arranged corresponding to the reversing path, the start / stop operation of the driving roller is performed according to the information of the sheet detecting means arranged at the predetermined positions of the introduction path and the reversing path. It is also possible to configure a means for controlling and controlling the driving of the nip release roller device and the operation of the nip release according to the information of the detection timing of the two detection means.

[0013]

In the sheet reversing and discharging device of the image forming apparatus of the present invention configured as described above, the return path is arranged between the discharging roller of the fixing device and the discharging roller corresponding to the discharging tray via the gate member. , A reversing path is disposed downstream of the return path via a reversing roller device, and, as in the case of a conventional sheet conveying device, single-sided copy paper is directed to an intermediate tray or the like via a double-sided branch path. The feeding action can be performed in the inverted state. Further, in the reversing discharge portion of the present invention, since the sheet conveying paths corresponding to the three sheet guide paths of the gate member are arranged, the fixing discharging roller and the discharging roller are directly connected, and the fixing discharging roller is fixed. An introduction path that connects the roller and the return path and a discharge path that connects the return path and the discharge roller are configured. Then, when the sheet is reversed and discharged, the sheet is guided to the return path and the reverse path through the introduction path, and then the roller device arranged in the return path is reversely driven, and the sheet is discharged to the discharge roller through the discharge path. Means for guiding toward can be configured.

In the present invention, the nip release roller device arranged in the return path is configured as a roller device capable of forward and reverse driving, and the pinch roller of the nip release roller device is configured to be capable of being brought into and out of contact with the drive roller. At the same time, it constitutes a means for performing the operation of releasing the nip in the nip release roller device according to the information of the sheet detecting means arranged at the predetermined positions of the introduction path and the reversing path. Further, in the reversing roller device arranged corresponding to the reversing path, the roller member on the side corresponding to the introducing path is a pinch roller, and the roller member on the side corresponding to the discharging path is a driving roller, which corresponds to the introducing path. The surface of the pinch roller on the feeding side is made of a material having a small friction coefficient, and constitutes a means for exerting only the action of pressing the paper toward the drive roller. Therefore, for example, even when the leading edge of the succeeding sheet is about to enter the nip position of the reversing roller device while the sheet is being fed from the reversing path to the returning path, the friction of the pinch roller on the leading edge of the succeeding sheet does not occur. It is possible to prevent the action from being greatly imparted.

Further, in the present invention, in the reversing roller device arranged corresponding to the reversing path, the driving roller is started / stopped according to the information of the sheet detecting means arranged at predetermined positions of the introduction path and the reversing path. It constitutes a means for controlling the operation of. A means for controlling the driving of the nip release roller device and the operation of the nip release may be configured by comparing and examining the conveying states of the preceding paper and the succeeding paper according to the information on the detection timings of the two detection means. It is possible. Further, in the reversing discharge portion of the present invention, the guide plate is curved toward the nip position of the nip release roller device to provide the guide portion, and a means for guiding the sheet to the nip release roller device is configured, By providing a means such as arranging a margin portion for forming a loop of the succeeding paper between the release roller device and the reversing roller device,
It is possible to configure a means that does not cause any inconvenience when the two sheets are conveyed in the reverse direction inside the return path.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sheet reversing and discharging device of an image forming apparatus according to the present invention will be described with reference to the illustrated example. The example shown in FIG. 1 is provided with a branch portion, a return path, and a roller device similarly to the image forming apparatus shown in FIG. 6, but the reference numerals for the constituent members are different from those in the conventional example. Explaining. Further, although the configuration of the roller device arranged on the return path and the reversal path is slightly different from the configuration of the guide plate and the like,
The operation of reversing and ejecting the sheet through the return path can be performed in substantially the same manner as in the case of the conventional example. In the example shown in FIG. 1, the discharge roller 50 of the fixing device 4 and the discharge roller 5 arranged on the upstream side of the paper feed tray.
1, a return path 35 is provided via the gate member 31, and a reversal discharge unit 30 that guides the sheet according to the three sheet guide paths provided in the gate member 31 is configured.

In the reverse discharge section 30, the return path 3
A nip release roller device 52 is arranged at a predetermined position of 5, and a double-sided branch passage 42 is branched to a downstream portion thereof via a gate member 41, and an inversion passage 40 is connected. A means for guiding a single-sided copy sheet such as an intermediate tray toward the back side copy is disposed from the double-sided branch path 42, and in the double-sided copy creation mode, the single-sided copy sheet is discharged to the intermediate tray in a reversed state. , When the back side is copied, the paper can be sent out from the intermediate tray. A sensor S1 is provided downstream of the fixing and discharging roller 50 and a discharging roller 51 is provided in the sheet conveying path of the reverse discharging section.
A sensor S2 is provided on the downstream side of the
Sensors S3 are respectively arranged in the downstream portion of 5, and the detection information of the leading end portion or the trailing end portion of the sheet obtained by the sensors as the sheet detecting means is input to a control device (not shown). The sheet conveying operation in the reversing and discharging unit can be controlled.

Three sheet guide paths are formed in the gate member 31 arranged in the reversal discharge section 30, and the fixing discharge roller 50 and the discharge roller 5 are formed in correspondence with the sheet guide paths.
1, a direct discharge path 32 connecting the fixing discharge roller 50 and the return path 35, and a return path 35.
A discharge path 34 that connects the discharge roller 51 with the discharge roller 51 is provided.
Further, in the nip release roller device 52 arranged in the return path 35, the pinch roller 54 is provided so as to be able to come into contact with and separate from the drive roller 53 arranged in the fixed position, and when the nip is released in the nip release roller device. In this case, the pinch roller 54 is separated from the drive roller 53 via a drive means such as a solenoid so that the sheet can freely pass between the two roller members. Return path 3
In the lower part of 5, an inversion path 40 is arranged in series,
A driving roller 56 and a pinch roller 57 are provided in the reversing path 40.
A reversing roller device 55 that is a combination of the above is provided.

When the sheet is reversed and discharged in the reverse discharge section 30 configured as described above, the sheet discharged from the fixing device 4 through the fixing discharge roller 50 is switched by switching the gate member 31 and the introduction path 33. I will guide you to. When guiding the paper toward the introduction path 33, the nip release roller device 52 is passed after a predetermined time has elapsed after the sensor S1 detected the leading end of the paper discharged from the fixing device 4.
Is driven in the normal rotation direction, and the paper guided from the introduction path 33 to the return path 35 is conveyed toward the reversal path 40. And
Return path 35 from fixing discharge roller 50 through introduction path 33
When the trailing edge of the sheet to be guided to the position is past the guide position by the gate member, the nip release roller device 52 is driven and switched in the reverse direction to guide the sheet along the discharge path 34 by the gate member 31. , So that it is delivered to the discharge roller 51 and discharged toward the discharge tray.

When only one sheet is conveyed in the return path 35, the sheet is reversed and discharged through the return path 35 as described above. If the succeeding sheet P2 is detected by the sensor S1 during the reverse discharging operation, the conveyance mode by the nip release roller device 52 is changed. For example, the nip release roller device 52 detects the succeeding sheet P2 according to the timing when the succeeding sheet P2 is detected by the sensor.
In the state where the sheet nip with the preceding sheet P1 at the nip position, it is necessary to release the nip in the nip release roller device 52. Therefore, in a state where the leading end of the preceding paper P1 is nipped by the discharge roller 51 and is conveyed in the discharge direction, the pinch roller 54 of the nip release roller device 52.
Is separated from the drive roller 53 so that the newly inserted succeeding paper P2 moves in the return path 35 in a passing state with respect to the preceding paper P1 conveyed in the discharge direction as shown in FIG. Therefore, even when the timing of transporting the preceding paper is delayed or slippage occurs in the roller device and the timing of transporting the paper is deviated, the transporting operation of the paper inside the return path is accurately performed. be able to.

The preceding sheet P1 being conveyed in the discharge direction while the sheet is being conveyed in the return path 35.
When the trailing edge of the sheet is detected by the sensor S3, it is assumed that the trailing edge of the sheet has passed the nip position of the nip release roller device after a predetermined time has elapsed since the detection signal was obtained. Then, the pinch roller 54 of the nip release roller device 52 is pressed toward the drive roller 53, and the nip release roller device is driven in the direction to convey the sheet downward, and the reversing roller device 55 is driven in the normal direction. Then, the succeeding sheet P2 is conveyed toward the reversing path 40, and the reversing operation of the next sheet is performed. Therefore, in the example shown in FIG. 1, even when the succeeding paper P2 is introduced into the return path while the preceding paper P1 is being discharged, the two papers reach the nip position of the nip release roller device 52. It will be acceptable to pass through in a passing state. When the trailing edge of the preceding sheet driven in the discharge direction has finished passing the nip position of the nip release roller device, the conveying action is performed on the succeeding sheet in the reverse conveying order, and the next sheet is conveyed. Even if the sheet passes through inside the return path, the two sheets can be moved in different directions with the nip of the nip release roller device released.

The example shown in FIG. 1 shows the case where two sheets intersect at the nip position of the nip release roller device, but the succeeding sheet P2 passes between the nip release roller device and the reversing roller device. In case of the state, as shown in FIG. 2, the nip release roller device 5
A loop may be formed on the succeeding sheet between the second sheet and the reversing roller device 55. Therefore, the return path 35
Of the two guide plates 36 and 39 that form the guide passage 3
An enlarged portion 38 is provided between the nip release roller device 52 and the reversing roller device 55 with respect to the inner guide plate 36 on the third side. Further, in the above embodiment, the succeeding paper P
When the leading end of the second sheet reaches the reversing roller device 55, the leading end of the succeeding sheet P2 enters the nip position of the reversing roller device because the reversing roller device is driven in the reverse direction with respect to the preceding sheet P1. However, the sheet is stopped in the state of forming a loop Pa on the sheet, and the sheet is made to stand by. Then, after the preceding paper P1 passes through the nip position of the reversing roller device 55, the reversing roller device 55 is driven in the normal rotation direction, and the leading end portion of the succeeding paper P2 is conveyed toward the reversing path 40 by the reversing roller device. To do the action.

In the embodiment shown in FIG. 2, the succeeding paper P2
When the loop Pa is formed on the sheet, if the loop of the sheet remains, there is a concern that the reverse conveyance of the sheet that is subsequently carried in subsequent sheets may be hindered. Therefore,
When the conveyance of the succeeding sheet is controlled, for example, the time when the leading edge of the succeeding sheet P2 passes the sensor S1 and is detected by the sensor S3 arranged downstream of the reversing roller device becomes a set value. On the other hand, when it is almost the same, it can be determined that the conveying action on the sheet is being performed accurately, so it is not necessary to perform an operation such as eliminating the sheet loop. On the other hand, the leading edge of the sheet has two sensors S1,
The time detected by S3 is longer than the set value T1.
In the case of 2, since it is estimated that a loop is formed on the succeeding sheet, it is necessary to control the driving of the reversing roller device so as to eliminate the loop generated on the succeeding sheet.

Therefore, in accordance with the difference (T2-T1) between the set value and the actual detection time, the time for driving the reversing roller device 55 in the forward direction is lengthened, and the timing of starting the reversing roller device is increased. By performing control such that there is a deviation, the reverse conveyance operation is performed in a state in which the loop of the succeeding sheet is eliminated. Further, in order to eliminate the loop, it is possible to deal with it by adjusting the driving timing with respect to the nip release roller device,
This can be dealt with by controlling the conveyance of the roller device based on information such as the size of the paper and the time difference from the set value.

In the above-described sheet conveying device, when two sheets are passing each other at the nip position of the nip release roller device, even if the nip of the nip release roller device is released, the leading end portion of the succeeding sheet is between the roller members. There are cases where you cannot pass through. Therefore, as shown in FIG. 3, of the two guide plates constituting the return path 35, the reduction portion 37 is arranged with respect to the inner guide plate 36 and the outer guide plate 39 is arranged along the reduction portion. Means can be provided to guide it closer to and through the nip position of the nip release roller device. The reduction portion 37 arranged on the inner guide plate 36 can be configured by bending the guide plate, and the reduction portion can be formed as a curved surface or can be processed by simply bending it. You can also Therefore, in order to pass the two sheets of paper through the roller members of the nip release roller device while passing them through each other, it is possible to easily deal with this by narrowing the width of the guide plate with respect to the return path. It is possible to prevent the leading end portion of the sheet from being caught at the nip position of the nip release roller device even if a state in which the succeeding sheet enters enters during the reverse conveyance.

Further, in the conveying roller device arranged in the reversing and discharging part of the present invention, particularly in order to insert the leading end of the sheet into the nip position of the reversing roller device, the surface of the pinch roller has a very small friction coefficient. Can be configured as. Pinch roller 57 of the reversing roller device 55
, The pinch roller 57 is arranged on the side of the introduction path into which the succeeding paper is inserted. For example, the roller member is made of a plastic material such as nylon and the roller is By making the surface of the member smooth, almost unevenness can be formed on the surface of the roller member.
Further, in the drive roller 56 arranged corresponding to the pinch roller 57, a rubber roller or the like is used to set a large friction coefficient with the sheet, similar to a roller member used in a general sheet conveying apparatus, and a sheet conveying operation is performed. Be able to do it in good condition. Therefore, as shown in FIG. 2, the preceding sheet P is driven while the reversing roller device 55 is driven in the reverse direction.
Even when the succeeding paper P2 reaches the nip position of the reversing roller device while 1 is being conveyed in the discharge direction, the leading end of the succeeding paper is still caught when the leading end of the succeeding paper is locked by the pinch roller. By strongly pressing the inner guide plate 36 as the pinch roller rotates, it is possible to prevent the paper from being folded.

A case where the preceding sheet and the succeeding sheet pass through the inside of the return path while passing each other in the reversing and discharging section of the present invention configured as described above will be described with reference to FIGS. First, when the preceding paper P1 is conveyed toward the introduction path 33 by the fixing discharge roller 50, the sensor S1
Is detected, the nip release roller device 52 is driven in the normal rotation direction (the direction in which the paper is conveyed toward the reverse path),
The drive of the nip release roller device is stopped at the timing when the trailing end of the sheet in the conveying direction reaches the inversion point N. Then, after that, the nip release roller device is driven in the reverse direction, and the sheet is conveyed along the discharge path 34 toward the discharge roller 51. In the image forming apparatus that constitutes the reversing and discharging section, the distance a between the front and rear sheets is set to perform the sheet conveying operation, but the trailing edge of the preceding sheet P1 reaches the inversion point N and the reversing direction is set. The subsequent paper P2
Passes through the invert point and reaches the nip position of the nip release roller device.

Therefore, the sheet conveying speed in the image forming apparatus is set to Vp, and the stop time for reversing the sheet is t.
5 is s, the distance between the inversion point N and the nip release roller device 52 is d, the distance between the nip release roller device and the reversing roller device is e, and the length of the paper is L.
In the above, the interval Y that can be set because the trailing edge of the preceding paper P1 and the leading edge of the following paper P2 pass and the paper passage time Ty can be obtained according to the following equations. Ty = {(a + d + e) / Vp}-[{(L-d-e)
/ Vp} + ts] (sec) Y = Ty × Vp (mm), and the larger the value of Y, the larger the margin for reverse conveyance.

In the example shown in FIG. 5, the distance e between the nip release roller device and the reversing roller device is e.
Is set to about 140 mm in accordance with the smallest size sheet, but in practice, the larger the interval e, the easier the reversing operation of the sheet. Furthermore, the longer the distance between the invert point N and the nip release roller device, the better, and the smaller the paper size, the more the reversal operation can be supported. In addition to the above conditions, in the reversing and discharging unit of the present invention, the shorter the stop time ts when reversing the paper is set, the less the paper is misaligned in the return path. However, it is unavoidable that the nip position of the nip release roller device is different. Then, in the case of a large size sheet such as A3 size, the sheet is stopped in a state of forming a loop on the succeeding sheet P2 between the nip release roller device 52 and the reversing roller device 55, and the preceding sheet is nipped by the reversing roller device. It is necessary to control the operation timing of the reversing roller device to eliminate the loop in the state of leaving the position.

Further, in the reversing and discharging section of the present invention, the sensors S1 and S2 arranged corresponding to the branching section and the sensor S arranged at a position close to the reversing roller device 55.
3 can be arranged at any position. Then, the interval between the position of the sensor and each roller device for reversing and ejecting the sheet, and the inversion point N
A program can be set in the control device so as to perform the nip release operation with respect to the nip release roller device according to the information such as the position. further,
According to the state of paper transport in the return path, the forward / reverse drive timing is set for the nip release roller device and the reverse roller device, and when the paper is transported in a slipping state, the papers interfere with each other. It is possible to perform processing that is unlikely to occur.

[0031]

Since the sheet reversal discharge device of the image forming apparatus of the present invention is configured as described above, a gate member is interposed between the discharge roller of the fixing device and the discharge roller corresponding to the discharge tray. By arranging the return path and arranging the reversal path via the reversing roller device in the downstream part of the return path, the single-sided copy paper can be intermediately transferred through the double-sided branch path as in the case of the conventional paper conveying apparatus. It is possible to perform the action of feeding in a state of being inverted toward the tray or the like. Then, when the sheet is reversed and discharged, the sheet is guided to the return path and the reverse path through the introduction path, and then the roller device arranged in the return path is reversely driven, and the sheet is discharged to the discharge roller through the discharge path. Means for guiding toward can be configured.
In the present invention, in the reversing roller device arranged corresponding to the reversing path, the roller member on the side corresponding to the introduction path is a pinch roller, and the roller member on the side corresponding to the discharge path is a driving roller. The surface of the pinch roller on the side corresponding to the introduction path is made of a material having a small friction coefficient, and constitutes means for exerting only the action of pressing the sheet toward the drive roller. Therefore, for example, while sending the paper from the reverse path to the return path,
Even when the leading edge of the succeeding sheet is about to enter the nip position of the reversing roller device, it is possible to prevent the frictional action of the pinch roller from being greatly applied to the leading edge of the succeeding sheet.

Further, in the present invention, in the reversing roller device arranged corresponding to the reversing path, the driving roller is started / stopped according to the information of the sheet detecting means arranged at predetermined positions of the introduction path and the reversing path. Means for controlling the operation of the nip release roller device and the nip release operation are comparatively examined according to the information of the detection timings of the two detection means and the conveyance states of the preceding sheet and the succeeding sheet are compared and examined. It is also possible to configure means for controlling the. Further, in the reversing discharge portion of the present invention, a guide portion in which the guide plate is curved toward the nip position of the nip release roller device is provided, and means for guiding the paper to the nip release roller device is configured, By providing a means for arranging a margin for forming a loop of the succeeding paper between the release roller device and the reversing roller device, a problem occurs when the two papers are conveyed in the reverse direction inside the return path. It is possible to carry out the action of transporting the paper without doing so.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a reversal discharge unit of the present invention.

FIG. 2 is an explanatory diagram of an example in which means for forming a sheet loop is provided between a nip release roller device and a reversing roller device.

FIG. 3 is an explanatory diagram of an example of processing a sheet conveyance path corresponding to a nip release roller device.

FIG. 4 is an explanatory diagram of a state before a sheet slips in a normal state in the return path.

FIG. 5 is an explanatory diagram of a state in which a succeeding paper sheet and a preceding paper sheet pass each other.

FIG. 6 is an explanatory diagram showing a configuration of a general image forming apparatus.

[Description of Reference Signs] 1 image forming apparatus, 3 photoconductor drum, 4
Fixing device, 10 paper feed tray, 13 intermediate tray, 22/31 gate member, 30 reverse discharge section, 32 direct discharge path, 33 introduction path, 34
Discharge path, 35 return path, 36 inner guide plate, 37 reduced section, 38 enlarged section, 40 reversal path, 50 fixing discharge roller, 51 discharge roller, 52 nip release roller device, 55 reversal roller device.

Claims (3)

[Claims] 1. A return path is arranged between a discharge roller of a fixing device and a discharge roller corresponding to a discharge tray via a gate member, and a reverse path is arranged downstream of the return path via a reverse roller device. According to the paper guide path of the gate member, a direct discharge path that directly connects the fixing discharge roller and the discharge roller, an introduction path that connects the fixing discharge roller and the return path, and a discharge path that connects the return path and the discharge roller are provided. When each sheet is reversed and ejected, the sheet is guided through the introduction path to the return path and the reversal path, and then the roller device placed in the return path is driven in reverse to eject the paper through the ejection path. In a sheet conveying device configured to guide means toward a roller, the roller device arranged in the return path is configured as a nip release roller device capable of forward and reverse driving and capable of releasing a nip,
The pinch roller of the nip release roller device is configured to be capable of coming into contact with and away from the drive roller, and the nip of the nip release roller device is adjusted according to the information of the sheet detecting means arranged at a predetermined position of the introduction path and the reversal path. In the reversing roller device, which constitutes means for performing the releasing operation, and is arranged corresponding to the reversing path,
The roller member on the side corresponding to the introduction path is a pinch roller,
A sheet reversing and discharging device of an image forming apparatus, wherein a roller member on a side corresponding to a discharging path is configured as a driving roller. 2. In the reversing roller device arranged corresponding to the reversing path, the surface of the pinch roller on the side corresponding to the introducing path is made of a material having a small friction coefficient, and presses the paper toward the driving roller. The sheet reversing and discharging device of the image forming apparatus according to claim 1, further comprising means for exhibiting only the action. 3. The reversing roller device arranged corresponding to the reversing path controls the start / stop operation of the driving roller according to the information of the sheet detecting means arranged at predetermined positions of the introducing path and the reversing path. The image forming apparatus according to claim 1, further comprising: a unit that controls the driving of the nip release roller device and the operation of the nip release according to the information on the detection timing of the two detection units. Paper reversal ejection device.