JP2002205860A - Image forming apparatus, printer, copier and facsimile machine - Google Patents

Abstract

(57) [Problem] To reduce the noise generated when a sheet is fed by the sheet reversing means when the interval between sheets continuously fed to the image forming unit is reduced by using a reversing path and a sheet reversing means. This prevents the paper from entering and exiting the reversing path smoothly. A sheet reversing means (22) includes a reversing roller (20) intermittently driven to rotate and a driven roller (21) abutted on the outer peripheral surface of the reversing roller (20) and rotated.
A low friction portion 20a is formed in which the frictional resistance against the paper passing between the outer peripheral portion of the reversing roller 20 and the driven roller 21 is smaller than the other portions. Since the paper is fed from the reversing path 7 by rotating the reversing roller 20 and holding the paper between the driven roller 21 and the portion other than the low friction portion 20a of the reversing roller 20, no noise is generated. When the reversing roller 20 is stopped with the low-friction portion 20a facing the driven roller 21, the paper can smoothly enter and exit between the low-friction portion 20a and the driven roller 21.

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 and a printer, a copying machine, and a facsimile machine using the image forming apparatus.

[0002]

2. Description of the Related Art A sheet feeding structure in a conventional image forming apparatus includes a sheet feeding unit for separating and feeding sheets stacked and held in a sheet storage unit one by one, and a sheet feeding unit for separating and feeding sheets. And a registration roller located immediately before the image forming unit on the paper conveyance path.

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 a sheet is sent out by a registration roller and the trailing edge of the sheet overlaps the leading edge of the succeeding sheet, the sheet is fed to the image forming section in a connected state. (1) One image is formed over two sheets of paper, making it impossible to form a correct image on the paper.

Therefore, in the case where image formation is continuously performed, two sheets are not overlapped even if the next sheet is fed while the preceding sheet is stopped at the position of the registration roller. In addition, it is necessary to widen the interval between the front and rear sheets and feed the sheets separately.

Further, in the paper feeding structure of the conventional image forming apparatus, slippage during separation paper feeding by the separation paper feeding means, aging of the paper conveyance speed and environmental change, and variation in stop time for registration are taken into account. In the case where image formation is performed continuously, the paper is fed with an interval of several tens mm between the front and rear sheets. For this reason, it is difficult to improve the productivity of image formation.

Further, the image forming section of the electrophotographic system is not operated even when paper is not conveyed to the image forming section, and runs idle without operation because of its structure. The large spacing between sheets of paper increases the idle operation time, and the life of the apparatus is reduced to less than the original usable number of prints.

[0008] Accordingly, the applicant of the present application has
As an image forming apparatus capable of improving the workability of image formation by narrowing the interval between sheets fed to the image forming unit in the case where image formation is continuously performed, the image forming apparatus is provided in the middle of a sheet conveyance path. Image forming apparatuses provided with a reversing path and sheet reversing means are proposed in Japanese Patent Application Nos. 11-239672 and 2000-230153.

According to the image forming apparatus provided with the reversing path and the sheet reversing means, the sheet separated and fed from the sheet storage unit and conveyed through the sheet conveying path is sent to the reversing path, and the sheet is fed to the reversing path. , And is switched back and sent to the image forming unit. Further, while the paper fed to the reversing path is switched back and sent out to the image forming section, the subsequent paper is fed to the reversing path, and the feeding of the preceding paper to the image forming section is performed at a predetermined position. , The next sheet feeding from the reversing path to the image forming unit is started. Thus, the interval between sheets continuously fed to the image forming unit can be reduced, and the workability of image formation can be improved. In addition, since the time during which the image forming unit is idly operated without forming an image is shortened, it is possible to prevent the life of the apparatus from being shortened due to the idling operation.

[0010]

However, the structure of the sheet reversing means for feeding the succeeding sheet to the reversing path while feeding the sheet from the reversing path is described below. There is a demand for a structure that can reliably send out paper.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce noise caused by feeding of a sheet from the reversing path when the interval between sheets continuously fed to the image forming section is reduced by using the reversing path and the sheet reversing means. It is to be.

Another object of the present invention is to provide a reversing path and a sheet reversing means for reducing the interval between sheets continuously fed to the image forming section so that the sheet enters and exits the reversing path smoothly. Is to do it.

Another object of the present invention is to provide a simple structure of the sheet reversing means when the interval between sheets continuously fed to the image forming section is reduced by using the reversing path and the sheet reversing means. It is.

Another object of the present invention is to reliably feed the paper from the reversing path when the interval between the sheets continuously fed to the image forming section is reduced by using the reversing path and the sheet reversing means. Is to do.

[0015]

According to an aspect of the present invention, there is provided an image forming apparatus comprising: a sheet storage unit for stacking and holding sheets; and a separation sheet feeding unit for separating and feeding sheets one by one from the sheet storage unit. An image forming unit that forms an image on a fed sheet, a sheet conveying path from the sheet storing unit to the image forming unit, and a sheet that is connected and fed separately in the middle of the sheet conveying path. A reversing path to be fed, and a sheet that allows the sheet fed to the reversing path to be switched back and sent out to the downstream side of the sheet conveying path, and that the following sheet is allowed to be fed to the reversing path during the feeding. A reversing means, wherein the paper reversing means comprises a reversing roller which is intermittently driven to rotate, and a driven roller which is brought into contact with the outer peripheral surface of the reversing roller and is rotated. This inversion Frictional resistance to the paper passing between the over La and the driven roller is smaller low-friction portion from the other portions are formed.

Therefore, the sheets stacked and held in the sheet storage section are separately fed one by one by the separate sheet feeding means, and are conveyed through the sheet conveying path. The sheet conveyed along the sheet conveying path is sent to the reversing path, temporarily stopped in the reversing path, and then switched back by the sheet reversing unit to the image forming unit located on the downstream side of the sheet conveying path from the reversing path. An image is formed on the sheet that has been sent and sent to the image forming unit.

Here, the sheet can be fed to the reversing path while the preceding sheet is being fed out of the reversing path. Therefore, when the preceding sheet is fed to a predetermined position on the image forming unit side, the sheet is reversed. It is possible to start feeding the subsequent sheet from the road to the image forming unit, and it is possible to reduce the interval between sheets continuously fed to the image forming unit,
Workability of image formation is improved.

When the sheet is sent out from the reversing path, the sheet is nipped by a portion other than the low friction portion of the reversing roller and the driven roller, and the reversing roller is driven to rotate. It can send out smoothly by applying force. In addition, when the sheet is sent out from the reversing path, the reversing roller is merely driven to rotate, thereby preventing the reversing roller and the driven roller from violently colliding with each other and generating noise.

When it is no longer necessary to apply a further conveying force from the reversing roller to the sheet by feeding the sheet to a predetermined position, the reversing roller is positioned at a position where the low friction portion of the reversing roller faces the driven roller. Stop the rotation of. Between the low friction portion of the reversing roller and the driven roller,
Since the frictional resistance against the paper passing between the reversing roller and the driven roller is small, even if the rear end side of the paper sent out from the conveyance path in the feeding direction is sandwiched between the low friction portion and the driven roller, Progresses smoothly. Further, the following sheet can be smoothly fed between the low friction portion of the reversing roller and the driven roller.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the sheet is switched back and sent from the reversing path to the downstream side of the sheet transport path, and the reversing path is fed during the feeding. The sheet is conveyed so as to at least partially overlap the subsequent sheet sent to the sheet.

Therefore, while the preceding sheet is being sent out from the reversing path, the succeeding sheet can be kept in a state where it can be sent out from the reversing path. When the sheet is fed from the printer, the interval between the preceding sheet and the preceding sheet can be reliably maintained at a minimum necessary interval, and the interval between the sheets continuously fed to the image forming unit can be sufficiently reduced.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the reversing roller has a cutout as a low friction portion in a part of an outer peripheral portion.

Therefore, a gap is formed between the reversing roller and the driven roller by making the notch face the driven roller, and the rear end side of the sheet fed from the conveyance path in the feeding direction is set between the reversing roller and the driven roller. Even when the sheet is located at the position, no frictional resistance is given to the sheet, and the sheet is smoothly fed. Further, the following sheet can be allowed to enter between the cutout portion and the driven roller, and the following sheet can be sent to the reversing path while the preceding sheet is being sent from the transport path.

[0024] 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, a driving unit is connected to one end of the roller shaft of the reversing roller, and a rotation position detecting unit is provided at the other end of the roller shaft.

Therefore, the reversing roller can be rotationally driven by the driving section, and its rotational position can be detected by the rotational position detecting means, so that the control of the rotational driving and the stop of the reversing roller can be accurately performed.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the driving section is a stepping motor.

Therefore, the rotation stop position of the reversing roller can be more accurately controlled, and the reversing roller can be reliably stopped at a position where the notch faces the driven roller.

[0028] The invention according to claim 6 is the invention according to claims 1 to 5.
In the image forming apparatus according to any one of the above, the reversing roller has a plurality of roller units arranged along a width direction orthogonal to a conveying direction of a sheet to be conveyed.

Therefore, when the sheet is fed from the reversing path, a uniform force can be applied to the sheet in the width direction, and the skew of the fed sheet can be prevented.

The invention according to claim 7 is the first to fifth aspects.
In the image forming apparatus according to any one of the above, the reversing roller has one wide roller portion at a central portion in a horizontal width direction orthogonal to a conveying direction of the sheet to be conveyed.

Therefore, the structure of the reversing roller is simplified.

[0032] The invention of claim 8 provides the invention according to claims 1 to 7.
In the image forming apparatus according to any one of the above, at least one of the reversing roller and the driven roller is a rubber roller.

Therefore, it is possible to prevent the occurrence of a slip when the sheet is sent out from the reversing path, and the sheet can be sent out from the reversing path with high accuracy.

According to the ninth aspect of the present invention, there are provided the first to eighth aspects.
In the image forming apparatus according to any one of the above, both end portions of the roller shaft of the reversing roller and the roller shaft of the driven roller are respectively held by bearings, and the bearings are orthogonal to a sheet conveying direction in the reversing path. It is fixed to side plates located on both sides in the width direction.

Accordingly, the structure for holding the reversing roller and the driven roller is simplified.

According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the reversing roller is held at a fixed position, and the driven roller moves in a direction of coming into contact with or separating from the reversing roller. It is movably held and urged by urging means in a direction in which it comes into contact with the reversing roller.

Therefore, even when the sheet thickness is different, the sheet can be reliably held by the reversing roller and the driven roller, and the sheet can be reliably sent out. Further, a driving unit or the like is not connected to the driven roller, and even if the driven roller is movably held in a direction of coming and going with respect to the reversing roller, the holding structure has a simple structure.

According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, an outer peripheral portion on an upper end side of the driven roller slightly protrudes from a paper guide surface of the reversing path. .

Therefore, the sheet fed from the reversing path can be reliably held between the reversing roller and the driven roller.
Further, it is possible to prevent the paper sent out from the transport path from being rubbed against the paper guide surface and causing skew.

According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects, a detection sensor for detecting a sheet fed to the reversing path and a detection result of the detection sensor are provided. And a driving means for driving the reverse roller to reverse after a predetermined time has elapsed.

Therefore, the detection result of the detection sensor can be used as a trigger of the driving means, and the timing control for inverting the reversing roller can be accurately performed.

According to a thirteenth aspect of the present invention, in the image forming apparatus of the twelfth aspect, the detection sensor is provided at at least one of before and after a branch point between the sheet transport path and the reversing path.

Therefore, the detection sensor is located near the reversing path, and the timing control for reversing the reversing roller, which performs the detection result from the detection sensor as a trigger of the driving means, can be performed with higher accuracy.

According to a fourteenth aspect of the present invention, in the image forming apparatus of the twelfth or thirteenth aspect, the detection sensor detects a trailing edge of the sheet.

Therefore, the time from when the detection sensor detects the sheet to when the reversing roller is driven to be reversed can be shortened. More accurate.

According to a fifteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fourteenth aspects, the image forming section is an electrophotographic image forming section.

Therefore, an image forming apparatus having an electrophotographic image forming section has the same functions and effects as the invention according to any one of the first to fourteenth aspects.

According to a sixteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fourteenth aspects, the image forming section is a digital electrophotographic type image forming section having digital writing means.

Therefore, in an image forming apparatus having a digital electrophotographic image forming section provided with digital writing means, the same operation and effect as the invention according to any one of claims 1 to 14 can be obtained.

According to a seventeenth aspect of the present invention, in the image forming apparatus according to any one of the first to fourteenth aspects, the image forming section is a non-electrophotographic image forming section.

Therefore, an image forming apparatus having a non-electrophotographic image forming section has the same functions and effects as the invention according to any one of the first to fourteenth aspects.

According to an eighteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fourteenth aspects, the paper is a card.

Therefore, in an image forming apparatus for forming an image on a card, the operation and effect according to any one of claims 1 to 14 can be obtained.

According to a nineteenth aspect of the present invention, there is provided a printer according to any one of the first to eighteenth aspects, an input terminal for receiving input of image data, and controlling the image forming apparatus to generate the image data. And a control unit for causing an image to be formed on a sheet based on the printer.

Therefore, this printer can also provide the same functions and effects as those of the present invention.

According to a twentieth aspect of the present invention, there is provided a copying machine for reading an image of a document, an image forming apparatus according to any one of the first to eighteenth aspects, and the image reading apparatus and the image forming apparatus. A control unit for controlling the image forming apparatus to form an image on a sheet based on image data of the document read by the image reading apparatus.

Therefore, in this copying machine, the same operation as the invention according to any one of claims 1 to 18,
The effect can be achieved.

A facsimile apparatus according to a twenty-first aspect of the present invention provides an image reading apparatus for reading an image of a document, an image forming apparatus according to any one of the first to eighteenth aspects, and an external device via a network. A transmission / reception device for transmitting / receiving data, and controlling the image reading device, the image forming device, and the transmission / reception device to transmit image data of a document read by the image reading device to the outside via a network by the transmission / reception device A control unit that causes the transmitting / receiving device to form an image on a sheet by the image forming device based on image data received from the outside via a network.

Therefore, this facsimile apparatus can also provide the same functions and effects as those of the first to eighteenth aspects.

[0060]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. This embodiment is applied to a digital electrophotographic image forming apparatus having a digital writing unit.

FIG. 1 is a front view schematically showing the structure of the image forming apparatus according to the first embodiment. The image forming apparatus includes an image forming unit 2 for forming an image on a sheet by an electrophotographic method from a sheet feeding tray 1 as a sheet storing unit for holding and stacking sheets, and a fixing unit 3 for fixing the formed image on the sheet. A transport path 5 is formed through which the sheet after image formation is discharged to a discharge stacker unit 4 through which the sheet is discharged. In the transport path 5, from the paper feed tray 1 to the image forming unit 2, the paper transport path 6
It has been.

In the middle of the paper transport path 6, there is provided a branch point 8 at which the reversal path 7 whose innermost portion has reached a dead end branches. A transport roller 10 that is driven by a motor (see FIG. 6) 9 to transport the paper is provided upstream of the branch point 8 in the paper transport path 6. At the branch point 8,
An inlet roller 12 driven by a motor (see FIG. 6) 11 to feed the sheet to the reversing path 7, an inlet sensor 13 located upstream of the inlet roller 12 in the sheet conveying path 6 and detecting the leading edge of the sheet passing therethrough, And a branch claw 14 for switching the path of the sheet fed into the reversing path 7 and the path of the sheet fed from the reversing path 7. The entrance sensor 13 of the present embodiment is a reflection type optical sensor including a light emitting element (not shown) that emits light and a light receiving element (not shown) that receives light emitted by the light emitting element. When the paper is conveyed, the light emitted by the light emitting element is reflected by the paper,
The sheet is detected by receiving the reflected light with the light receiving element.

Downstream from the branch point 8 in the paper transport path 6, a transport roller 16 driven by a motor (see FIG. 6) 15 to feed the paper switched back in the reverse path 7 to the image forming section 2. And a registration roller 18 for performing a registration operation for synchronizing a conveyance timing for conveying a sheet detected by a registration sensor 17 to be described later to the image forming section 2 with the image forming operation. The registration sensor 17 is the same reflection type sensor as the entrance sensor 13 described above.

The reversing path 7 has a stepping motor (FIG. 6).
The reversing roller 20 which is intermittently driven by 19 and has a cutout portion 20a as a low friction portion cut off in a part of the outer peripheral portion.
And a driven roller 21 which is disposed at a position facing the reversing roller 20 with the reversing path 7 interposed therebetween, and which comes into contact with a portion other than the cutout portion 20a when the reversing roller 20 rotates, and is rotated by the contact. Further, a sheet reversing device 22 as a sheet reversing means is provided. The sheet fed to the reversing path 7 is switched back by the sheet reversing device 22 and sent out from the reversing path 7. The sheet reversing device 22 sends out the switched back sheet from the reversing path 7 to the sheet conveying path 6 and allows the subsequent sheet to be fed into the reversing path 7 during the sending out. The fed sheet and the subsequent sheet fed into the reversing path 7 during the feeding are conveyed so that at least a part thereof overlaps. A reversing sensor 23 for detecting the leading end of the fed sheet is provided downstream of the entrance roller 12 of the sheet fed to the reversing path 7 in the transport direction. The reversing sensor 23 is the same reflection type sensor as the entrance sensor 13 described above.

On the downstream side of the paper feed tray 1 in the paper transport direction, there is provided a pickup roller 24 for taking out the stacked and held sheets, and a separation roller 25 for separating the taken out sheets one by one. Paper feeder 2 as
6 are provided.

The image forming section 2 includes a photosensitive member 27 on which an image is formed on the surface and a charger 2 for uniformly charging the photosensitive member 27.
8, a digital optical writing device 29 as digital writing means for optically writing an electrostatic latent image on the photoconductor 27,
A developing unit 30 that forms a toner image by attaching toner to the electrostatic latent image on the photoconductor 27; a transfer unit 31 that transfers the developed toner image onto paper; A cleaning device 32 that removes toner, and forms an image on paper by a digital electrophotographic process.

The fixing section 3 is provided with a pressure roller 33 and a heating roller 34 for fixing the toner image transferred on the sheet to the sheet. On the downstream side of the fixing unit 3 in the sheet conveying direction, a paper discharge roller 35 for discharging the paper on which the toner image is fixed to the paper discharge stacker unit 4 is provided.

The branch claw 14 arranged at the branch point 8
First guide surface 1 facing the sheet fed to reversing path 7
4a and a second sheet facing the sheet fed from the reversing path 7.
It is formed in a substantially triangular shape having a guide surface 14b and an acute-angled branch claw tip 14c facing the reversing path 7 sandwiched between the first guide surface 14a and the second guide surface 14b. The branch claw 14 is rotatably held around the axis of the support shaft 36, and is pressed by a spring (not shown) in a direction in which the first guide surface 14 a is pressed against the sheet fed to the outer peripheral surface of the reversing path 7. Being energized. The paper conveyed from the paper feed tray 1 enters between the outer peripheral surface of the entrance roller 12 and the first guide surface 14a of the branch claw 14, and pushes up the branch claw 14 by its own stiffness, and the first guide surface The paper is fed into the reversing path 7 through a space between the roller 14a and the outer peripheral surface of the inlet roller 12.

FIGS. 3 to 5 illustrate details of the sheet reversing device 22. FIG. Reversing roller 2
As shown in FIG. 3, 0 is formed by fixing two roller portions 20c to the roller shaft 20b, and the above-described cutout portion 20a is formed in the roller portion 20c. The two roller portions 20c are positioned so as to be symmetrical in the width direction orthogonal to the conveying direction of the sheet to be conveyed, and are positioned so as to be within the range of the sheet width even for the sheet having the smallest sheet width. . The reversing roller 20 is a rubber roller in which the roller portion 20c is formed of urethane rubber, styrene / butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, ethylene / propylene rubber, or the like.

A stepping motor 19 as a driving unit is connected to one end of the roller shaft 20b, and an encoder 37 as rotation position detecting means is provided at the other end of the roller shaft 20b. The encoder 37 includes a disk 38 with a slit fixed to the roller shaft 20b, and a light emitting unit 39 and a light receiving unit (not shown) arranged at positions sandwiching the disk 38 with the slit. In addition, the driven roller 21
The roller portion 21c is formed of a rubber roller formed of urethane rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, ethylene-propylene rubber, or the like, or a roller formed of polyurethane foam, aluminum stainless steel, or the like. Metal roller.

As shown in FIG. 3, the driven roller 21 is formed by fixing two roller portions 21c to a roller shaft 21b, and the two roller portions 21c are vertically connected to the roller portion 20c of the reversing roller 20. It is arranged at the position facing in the direction.

FIG. 4 is a front view schematically showing the sheet reversing device 22. As shown in FIG.
When the notch 20a faces the driven roller 21, a gap is formed between the reversing roller 20 and the driven roller 21, and the feeding of the sheet to the reversing path 7 is allowed.
As shown in FIG. 4B, when the outer peripheral surface of the reversing roller 20 and the outer peripheral surface of the driven roller 21 are in contact with each other, the driven roller 21 is rotated by being driven to rotate.
Is rotated, and the sheet nipped by the reversing roller 20 and the driven roller 21 is sent out from the reversing path 7 to the image forming unit 2. The outer peripheral portion on the upper end side of the driven roller 21 slightly protrudes from the paper guide surface 7 a of the reversing path 7. The protrusion dimension "h" is about 1 mm.

FIG. 5 shows a reversing roller 20 and a driven roller 21.
2 shows a holding structure of the roller shafts 20b and 21b. Bearings 4 are provided at both ends of these roller shafts 20b and 21b.
1 are fixed by E-rings 42, and these bearings 41 are fixed to side plates 43 located on both sides in the width direction orthogonal to the sheet conveyance direction in the reversing path 7.

FIG. 6 is a block diagram showing the electrical connection of a control system related to the sheet conveyance among the units provided in the image forming apparatus. The control system related to the paper transport includes a microcomputer 44 that controls the entire system intensively. Although not specifically shown,
The microcomputer 44 is a CPU that centrally drives and controls each unit.
To store fixed data such as programs in advance
It has a structure in which M and a RAM for storing variable data such as time measured by a timer in a rewritable manner are connected. The microcomputer 44 includes a motor driver 45 that drives the motor 9 that rotates the transport roller 10,
Motor driver 4 that drives motor 11 that rotates 2
6. A motor driver 47 for driving the motor 15 for rotating the transport roller 16, a motor driver 48 for driving the stepping motor 19 for rotating the reversing roller 20, the entrance sensor 13, the reversing sensor 23 and the like are connected.

In such a configuration, the sheets stacked and held on the sheet feeding tray 1 are separated and fed one by one by the separating sheet feeding device 26, and the separated and fed sheets are transported by the transport roller 10.
The paper is continuously transported in the paper transport path 6.

When the leading end of the sheet conveyed along the sheet conveying path 6 reaches the branch point 8, the leading end of the sheet strikes the first guide surface 14 a of the branch claw 14. Then, the branch claw 14 is pushed up by the strength of the stiffness of the sheet, and the sheet is sent to the reversing path 7 through between the first guide surface 14 a and the outer peripheral surface of the entrance roller 12. When the paper passes between the first guide surface 14a and the outer peripheral surface of the entrance roller 12, the branch pawl 14 is pressed against the paper by the urging force of the spring, so that the paper is pressed against the outer peripheral surface of the entrance roller 12. A conveying force is applied from the entrance roller 12 to the sheet.

When the paper is sent to the reversing path 7,
The reversing roller 20 and the driven roller 21 are stopped at positions separated from each other as shown in FIG. Therefore, the feeding of the sheet to the reversing path 7 (the feeding of the sheet between the reversing roller 20 and the driven roller 21) can be performed smoothly.

The feeding of the sheet from the reversing path 7 is based on the detection result of the leading edge of the sheet by the entrance sensor 13 or the reversing sensor 23.
According to the detection result of the leading edge of the sheet, after a lapse of a predetermined time after the detection, the reversing roller 20 is rotated once by a driving unit, which is one of the functions of the microcomputer 44. As the reversing roller 20 rotates, the sheet is nipped between the reversing roller 20 and the driven roller 21 to apply a conveying force, and is sent out from the reversing path 7 toward the image forming unit 2. Note that the feeding timing can secure a width dimension such that the leading end of the fed sheet and the trailing end of the previously fed sheet do not overlap at the position of the registration roller 18, and the width is allowed. It is set to be the minimum within the range.

The position of the transport roller 16 is set so that the leading end of the sheet in the transport direction is pinched by the transport roller 16 when the reversing roller 20 makes one rotation to feed the sheet. For this reason, even if the reversing roller 20 that has sent out the sheet makes one rotation and stops at the position shown in FIG. 4A, the sheet is continuously conveyed by applying a conveying force from the conveying roller 16.

Then, the reversing roller 20 makes one rotation, and FIG.
(A), when the trailing end of the sheet fed from the reversing path 7 is traveling between the reversing roller 20 and the driven roller 21, the subsequent sheet is moved to the reversing path 7 as described above. Can be sent to

By providing the entrance sensor 13 and the reversing sensor 23 before and after the entrance roller 12, these two sensors 13 and 23 can be used as a jam detection sensor at the entrance roller 12. That is, when the entrance sensor 13 detects the sheet but the reversing sensor 23 does not detect the sheet, the occurrence of the jam at the entrance roller 12 can be detected.

The entrance sensor 13 may have a structure for detecting the trailing edge of the sheet. By detecting the trailing edge of the sheet, the time from the detection to the driving of the reversing roller 20 is shortened, and the control of the driving timing of the reversing roller 20 that uses the detection result from the entrance sensor 13 as a trigger of the driving unit is improved. It will be possible to perform with higher accuracy.

Here, when feeding the sheet from the reversing path 7, the reversing roller 20 is driven to rotate and the reversing roller 20 is rotated.
Since the paper is nipped and fed by the portion other than the notch 20a and the driven roller 21, no noise is generated at the time of feeding.

FIGS. 7 and 8 are explanatory views for explaining the flow of sheets when the sheets are continuously conveyed. The preceding sheet a is sent out from the reversing path 7 to the sheet conveying path 6, and at the same time, the succeeding sheet b is conveyed toward the reversing path 7. Preceding paper a
First, a conveying force is applied by the reversing roller 20, and after the reversing roller 20 stops at the position shown in FIG. 4A, a conveying force is applied by the conveying roller 16 to be conveyed. On the other hand, the subsequent sheet b is provided with a conveying force by the conveying roller 10 and the entrance roller 12 and is sent to the reversing path 7. Since the reversing roller 20 is stopped at the position shown in FIG. 4A, even if the trailing end of the preceding sheet a sent out from the reversing path 7 is located in the reversing path 7, the following sheet b Is smoothly fed into the reversing path 7. As a result, two sheets having opposite conveyance directions can be overlapped in the reversing path 7, and the interval between the preceding sheet a and the succeeding sheet b can be reduced.

The sheet sent out from the reversing path 7 is conveyed by the conveying rollers 16 and temporarily stops after a predetermined time from the detection of the leading end of the sheet by the registration sensor 17. As shown in FIG. 7, the leading end of the sheet has a slight deflection due to the elasticity of the sheet itself, and the leading end thereof is
Contacted.

Then, the registration roller 18 is rotated in synchronization with the start of image formation in the image forming section 2, and the sheet is conveyed in synchronization with the image formation.

FIG. 9 is a diagram showing a sheet conveying operation. From the paper feed tray 1 to the reversal stop position in the reversing path 7, the paper is conveyed by the conveying roller 10 and the entrance roller 12 at the speed Va. The sheet is conveyed from the reversal stop position to the image forming section 2 by the reversing roller 20 and the conveying roller 16 at a speed Vb equal to the image forming speed. The speed Va is set to a paper transport speed that transports the paper faster than the speed Vb. Since the paper conveyed to the image forming unit 2 must be synchronized with the image forming speed, it is essential to set the paper conveying speed to the speed Vb on the downstream side of the registration roller 18 in the paper conveying direction. The paper transport speed Va is set faster than Vb from the paper feed tray 1 to the reversal stop position in order to increase the productivity of image formation.

In this embodiment, the reversing roller 20
Although the case where the notch portion 20a is formed as the low friction portion has been described as an example, a part of the reversing roller 20 is formed of a material having a small friction coefficient, or a part of the reversing roller 20 is formed of a material having a small friction coefficient. The material may be coated to form a low friction portion having the same radial dimension as other portions.

In the present embodiment, the reversing roller 20
Has been described as an example in which the sheet reversing device 22 is disposed so that the driven roller 21 is positioned on the lower side and the driven roller 21 is positioned on the lower side. Contrary to this arrangement, the reversing roller 20 is positioned on the lower side. Thus, the driven roller 21 may be positioned on the upper side. In the case where an image is formed on the other side of a sheet on which an image is formed on one side, if the reversing roller 20 is located on the lower side, the side of the sheet on which an image is already formed (reverse side) The surface facing upward in the path 7) is in contact with the driven roller 21. For this reason, it can be prevented that the surface of the sheet on which the image is already formed is strongly rubbed by the reversing roller 20 which is rotationally driven, and the image is not damaged.

Further, in the present embodiment, an image forming apparatus having a digital electrophotographic image forming section 2 having digital writing means has been described as an example. A photographic image forming unit can be used.

Next, a second embodiment of the present invention will be described with reference to FIG.
Description will be made based on 0. The same portions as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments).

In the present embodiment, the structure of the sheet reversing device 49 as the sheet reversing means is changed. The sheet reversing device 49 includes a reversing roller 50 that is intermittently driven to rotate and the driven roller 21.

The reversing roller 50 is formed by fixing one wide roller portion 50c, which is located at the center in the width direction orthogonal to the transport direction of the paper to be transported, to the roller shaft 50b. A cutout portion 50a as a low friction portion is cut out on the outer peripheral portion of the roller portion 50c. Roller part 5
0c is a urethane rubber as in the first embodiment,
It is made of styrene / butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, ethylene / propylene rubber, or the like.

The driven roller 21 has the same structure as that of the first embodiment, and is formed by fixing two roller portions 21c to a roller shaft 21b.

In such a configuration, the reversing roller 50
Has only one roller portion 50c, so that the positioning work when fixing the roller portion 50c to the roller shaft 50b is simpler than when there are a plurality of roller portions 20c as in the first embodiment. And an inexpensive structure.

Next, a third embodiment of the present invention will be described with reference to FIG.
1 will be described. This embodiment is different from the first and second embodiments in that the roller shaft 21 of the driven roller 21
The holding structure of b is changed. Bearings 41 are fixed to both ends of the roller shaft 21b of the driven roller 21 by E-rings 42. The bearings 41 are formed on side plates 43 formed on both sides of the reversing path 7 on both sides in the width direction orthogonal to the sheet conveying direction. It is fitted in the hole 51, and is movable in the direction in which it comes into contact with and separates from the reversing roller 20 in the elongated hole 51. Further, a spring 52 as urging means for urging the driven roller 21 in a direction in which the driven roller 21 abuts on the reversing roller 20 is mounted in the elongated hole 51.

Bearings 41 are fixed at both ends of the roller shaft 20b of the reversing roller 20 by E-rings 42.
Is fixed to the side plate 43 as in the first embodiment.

In such a configuration, the reversing roller 20
When the outer peripheral surface of the roller comes into contact with the outer peripheral surface of the driven roller 21,
The driven roller 21 is pressed against the reversing roller 20 by the urging force of the spring 52. Therefore, even when the sheet pressure of the sheet is low, the sheet can be reliably pinched by the reversing roller 20 and the driven roller 21, and the sheet can be smoothly fed out from the reversing path 7. Even when the paper pressure is thick, the reversing roller 20 and the driven roller 2
1 can reliably hold the sheet, and the sheet can be smoothly sent out from the reversing path 7.

Further, the stepping motor 19 and the like are not connected to the driven roller 21. Even if the driven roller 21 is movably held in the direction of coming and going with respect to the reversing roller 20, the holding structure has a simple structure. Can be.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
2 will be described. The image forming apparatus of the present embodiment conveys a card such as a train or bus ticket, a prepaid card, and forms an image on the card.

In this image forming apparatus, a card after image formation is transferred from a card tray 53 serving as a card storage section for stacking and holding cards via an image forming section (not shown) for forming an image on the paper. A transport path to a discharge stacker unit (not shown) for discharging the paper is formed. The sheet transport path 54 extends from the card tray 53 to the image forming section in the transport path.

In the middle of the paper transport path 54, the reversing path 7 whose innermost portion has a dead end is branched. At the branch point, a card fed from the card tray 53 by the paper feed roller 55 is fed. A claw 5 for switching the card conveying direction between a direction of feeding the card into the reversing path 7 and a direction of moving the card fed from the reversing path 7 by the sheet reversing device 22 toward the image forming unit.
6 and an inlet roller 57 that is driven to rotate in a direction to feed the card into the reversing path 7.

The preceding card a sent to the reversing path 7
Is started by the sheet reversing device 22, the subsequent card b is fed into the reversing path 7. This allows
At the timing when the preceding card a is conveyed to a predetermined position, the following card b can be sent out to the image forming unit, and the supply of the card to the image forming unit can be performed with a narrow interval between the cards. The workability in forming an image on a sheet is improved.

Then, the sheet reversing device 22 of the present embodiment
In the embodiment, by applying each of the above-described embodiments, the operations and effects described in each of the embodiments can be achieved.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
3 will be described. FIG. 13 is a block diagram illustrating a schematic structure of a printer 101 according to the present embodiment. The printer 101 includes an image forming apparatus 102 described in any one of the first to fourth embodiments, an input terminal 103 for receiving input of image data from an external device such as a personal computer, and an image forming apparatus. Apparatus 1
And a control unit 104 for controlling the image forming unit 02 to form an image based on the image data on a sheet.

Therefore, according to the printer 101, the same functions and effects as those described in the first to fourth embodiments can be obtained.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
4 will be described. FIG. 14 is a block diagram illustrating a schematic configuration of a copying machine 111 according to the present embodiment. The copying machine 111 includes an image reading device 1 that reads an image of a document.
12, the image forming apparatus 102 described in any one of the first to fourth embodiments, and the image reading apparatus 1
12 and the image forming apparatus 102 to control the image reading apparatus 1
And a control unit 113 for causing the image forming apparatus 102 to perform image formation based on the image data of the document read at 12 on paper.

Therefore, according to the copying machine 111,
The same operation and effect as those described in the first to fourth embodiments can be obtained.

Next, a seventh embodiment of the present invention will be described with reference to FIG.
5 will be described. FIG. 15 is a block diagram illustrating a schematic configuration of the facsimile apparatus 121 according to the present embodiment. The facsimile device 121 includes an image reading device 122 that reads an image of a document and the above-described first to fourth devices.
Image forming apparatus 10 described in any one of the embodiments.
2, a transmission / reception device 123 for transmitting / receiving image data to / from the outside via a network, and an image reading device 12
2. By controlling the image forming apparatus 102 and the transmission / reception apparatus 123, the image data of the original read by the image reading apparatus 122 is transmitted to the outside via the transmission / reception apparatus 123, or the transmission / reception apparatus 123 transmits the image data from the outside via the network. A control unit 124 for causing the image forming apparatus 102 to perform image formation based on the received image data on paper.

Therefore, the facsimile apparatus 121
According to the embodiment, the same operation and effect as those described in the above-described first to fourth embodiments can be achieved at the time of image formation based on the received image data.

[0111]

According to the image forming apparatus of the first aspect of the invention, when the sheet is sent out from the reversing path, the sheet is nipped by a portion of the reversing roller other than the low friction portion and the driven roller, and the reversing roller is rotated. Is performed by rotationally driving the paper, so that a sufficient conveying force can be applied to the paper to smoothly feed the paper, and when the paper is fed from the reversing path, only the reversing roller is driven to rotate.
It is possible to prevent the reversing roller and the driven roller from violently colliding with each other and generating noise. In addition, by stopping the reversing roller at a position where the low friction portion is opposed to the driven roller, the frictional resistance of the paper entering and exiting between the reversing roller and the driven roller is reduced. The paper can be smoothly moved in and out between the roller and the driven roller.

According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, the sheet which is switched back and is sent from the reversing path to the downstream side of the sheet conveying path and the sheet is reversed during the feeding. Since it is conveyed so that at least a part of it overlaps with the subsequent sheet sent to the road,
While the preceding sheet is being sent from the reversing path, it is possible to keep the subsequent sheet in a state where it can be sent out from the reversing path, and when the subsequent sheet is switched back and sent out from the reversing path, It is possible to reliably maintain the interval between the preceding sheet and the minimum necessary interval, and it is possible to sufficiently reduce the interval between sheets continuously fed to the image forming unit.

According to the third aspect of the present invention, in the image forming apparatus according to the first or second aspect, since the notch as the low friction portion is formed in a part of the outer peripheral portion, the notch is formed. When the reversing roller is stopped at a position where the portion faces the driven roller, a gap is formed between the reversing roller and the driven roller, so that paper can smoothly enter and exit between the reversing roller and the driven roller. Can be done.

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 driving unit is connected to one end of the roller shaft of the reversing roller, and the other end of the roller shaft is connected. Is provided with a rotational position detecting means,
The rotation position of the reversing roller can be accurately detected by the rotation position detecting means, and the rotation drive and stop of the reversing roller can be accurately controlled.

According to the fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, since the driving unit is a stepping motor, the control of the rotation driving and the stop of the reversing roller can be performed with higher accuracy. The reversing roller can be reliably stopped at a position where the notch faces the driven roller.

According to the sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the reversing rollers are arranged along a width direction orthogonal to a conveying direction of the sheet to be conveyed. Since a plurality of rollers are provided, a uniform force can be applied to the sheet in the width direction when the sheet is fed from the reversing path, and skew of the fed sheet can be prevented.

According to the seventh aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the reversing roller has a wide central portion in the width direction orthogonal to the conveying direction of the sheet to be conveyed. Since there is only one roller portion, the structure of the reversing roller can be simplified, and an inexpensive sheet reversing means can be obtained.

According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, at least one of the reversing roller and the driven roller is a rubber roller. Can be prevented from occurring when the sheet is fed, and the sheet can be fed from the reversing path with high accuracy.

According to the ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, both ends of the roller shaft of the reversing roller and the roller shaft of the driven roller are held by bearings. Since these bearings are fixed to the side plates located on both sides in the width direction orthogonal to the sheet conveyance direction in the reversing path, the structure for holding the reversing roller and the driven roller is simplified, and an inexpensive sheet reversing means is obtained. be able to.

According to the tenth aspect, the first aspect is provided.
9. The image forming apparatus according to claim 1, wherein the reversing roller is held in a fixed position, and the driven roller is movably held in a direction of coming into contact with and separating from the reversing roller, and biasing means is provided in a direction in which the reversing roller contacts the reversing roller. Even when the paper thickness is different, the paper can be reliably sent out by reliably nipping the paper by the reversing roller and the driven roller, and the driven roller is driven by the driven roller. Since the parts and the like are not connected, even if the driven roller is movably held, the holding structure can be simplified.

According to the eleventh aspect, according to the first aspect,
The image forming apparatus according to any one of claims 1 to 10,
Since the outer peripheral portion on the upper end side of the driven roller slightly protrudes from the paper guide surface of the reversing path, the paper fed from the reversing path can be reliably sandwiched between the reversing roller and the driven roller to be smoothly fed out. Skew can be prevented from occurring due to the paper fed from the transport path being strongly rubbed against the paper guide surface.

According to the twelfth aspect, according to the first aspect,
The image forming apparatus according to any one of claims 1 to 11,
Since a detection sensor for detecting the sheet fed to the reversing path and a driving unit for reversing the reversing roller after a predetermined time has elapsed according to the detection result of the detection sensor are provided,
The detection result of the detection sensor can be used as a trigger of the driving means, and the timing control for inverting the inversion roller can be accurately performed.

According to the thirteenth aspect, according to the first aspect,
In the image forming apparatus described in Item 2, since the detection sensor is provided at least before or after the branch point between the sheet conveyance path and the reversing path, the detection sensor is located near the reversing path. The timing control for reversing the reversing roller, which performs the detection result from the sensor as a trigger of the driving unit, can be performed with higher accuracy.

According to the fourteenth aspect, the first aspect is provided.
In the image forming apparatus according to the invention described in 2 or 13, since the detection sensor detects the trailing edge of the sheet, the time from when the detection sensor detects the sheet to when the reversing roller is driven to reverse is shortened. Thus, the control of the drive timing of the reversing roller, in which the detection result from the detection sensor is used as a trigger of the drive unit, can be performed with higher accuracy.

According to the fifteenth aspect, the first aspect is provided.
15. The image forming apparatus according to any one of
Since the image forming unit is an electrophotographic image forming unit,
In an image forming apparatus having an electrophotographic image forming unit, the same operation and effect as the invention according to any one of claims 1 to 14 can be obtained.

According to the sixteenth aspect of the present invention, the first aspect is provided.
15. The image forming apparatus according to any one of
Since the image forming unit is a digital electrophotographic image forming unit having digital writing means, the image forming apparatus has a digital electrophotographic image forming unit having digital writing means. Functions and effects similar to those of the invention described in any one of the aspects can be obtained.

According to the seventeenth aspect, according to the first aspect,
15. The image forming apparatus according to any one of
Since the image forming unit is a non-electrophotographic image forming unit, in an image forming apparatus having a non-electrophotographic image forming unit, the same operation and effect as the invention according to any one of claims 1 to 14 Can be played.

According to the eighteenth aspect, according to the first aspect,
15. The image forming apparatus according to any one of
Since the paper used is a card, the operation and effect according to any one of claims 1 to 14 can be achieved in an image forming apparatus that conveys the card and forms an image on the card.

According to the printer of the nineteenth aspect, the image forming apparatus according to any one of the first to eighteenth aspects, an input terminal for receiving input of image data, and controlling the image forming apparatus to control the image data. And a controller for causing an image to be formed on a sheet based on the printer. Therefore, this printer can also provide the same functions and effects as the invention according to any one of claims 1 to 18.

According to the copying machine of the twentieth aspect,
An image reading device for reading an image of a document, the image forming device according to any one of claims 1 to 18, and image data of the document read by the image reading device by controlling the image reading device and the image forming device. And a control unit for causing the image forming apparatus to form an image on a sheet by the image forming apparatus, so that the same operation and effect as those of the invention according to any one of claims 1 to 18 can be obtained in this copying machine. .

According to the facsimile apparatus of the twenty-first aspect, an image reading apparatus for reading an image of an original, the image forming apparatus of any one of the first to eighteenth aspects, and an external device via a network. A transmission / reception device that transmits and receives image data, and controls an image reading device, an image forming device, and a transmission / reception device to transmit image data of a document read by the image reading device to an external device via a network using the transmission / reception device. 19. A facsimile apparatus according to claim 1, further comprising a control unit for causing the image forming apparatus to perform image formation based on image data received from the outside via a network in the apparatus. The same operation and effect as the invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing a structure of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged front view showing a main part thereof.

FIG. 3 is a perspective view showing a sheet reversing device.

FIG. 4 is a front view illustrating an operation state of the sheet reversing device.

FIG. 5 is a vertical sectional side view showing a holding structure of the sheet reversing device.

FIG. 6 is a block diagram illustrating an electrical connection of a control system related to sheet conveyance in the image forming apparatus.

FIG. 7 is an explanatory diagram illustrating a flow of a sheet when the sheet is continuously conveyed.

FIG. 8 is an explanatory diagram illustrating a flow of a sheet when the sheet is continuously conveyed.

FIG. 9 is a diagram illustrating a sheet conveying operation.

FIG. 10 is a perspective view illustrating a sheet reversing device in an image forming apparatus according to a second embodiment of the present invention.

FIG. 11 is a vertical sectional side view showing a holding structure of a sheet reversing device in an image forming apparatus according to a third embodiment of the present invention.

FIG. 12 is a front view schematically showing a structure of an image forming apparatus which conveys a card and forms an image on the card according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram illustrating a printer according to a fifth embodiment of the present invention.

FIG. 14 is a block diagram of a copying machine according to a sixth embodiment of the present invention.

FIG. 15 is a block diagram of a facsimile apparatus according to a seventh embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper storage part 2 Image formation part 6 Paper conveyance path 7 Reversing path 7a Paper guide surface 13, 23 Detection sensor 19 Drive part, stepping motor 20, 50 Reversing roller 20a, 50a Low friction part, notch part 20b, 50b Roller shaft 20c , 50c roller unit 21 driven roller 22, 49 sheet reversing means 26 separation paper feeder 37 rotational position detecting means 52 urging means 102 image forming device 103 input terminal 104 control unit 112 image reading device 113 control unit 122 image reading device 123 transmission / reception Device 124 control unit

Continued on the front page (72) Inventor Takashi Seto 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 3F053 BA03 BA14 LA02 LA05 LA07 LB03 5C062 AA02 AA05 AB17 AB22 AB32 AC15 BA04

Claims (21)

[Claims] 1. A sheet storage unit for stacking and holding sheets, a separation sheet feeding unit for separating and feeding sheets one by one from the sheet storage unit, and an image forming unit for forming an image on the fed sheet. A paper transport path from the paper storage unit to the image forming unit, a reversing path connected in the middle of the paper transport path to which separated and fed paper is fed, and a switch for feeding the paper fed to the reversing path. Paper reversing means for allowing the sheet to be fed back to the downstream side of the paper transport path and allowing subsequent paper to be fed to the reversing path during the paper feeding, and wherein the paper reversing means is intermittently provided. A rotating roller that is driven in rotation and a driven roller that rotates while being in contact with the outer peripheral surface of the reversing roller. versus Frictional resistance image forming apparatus small low-friction portion from the other portions are formed that. 2. A sheet that is switched back and sent from the reversing path to the downstream side of the sheet transport path and a subsequent sheet that is fed into the reversing path during the feeding is overlapped at least partially. The image forming apparatus according to claim 1, wherein the image forming apparatus is transported. 3. The image forming apparatus according to claim 1, wherein the reversing roller has a cutout portion as a low friction portion in a part of an outer peripheral portion. 4. The image according to claim 1, wherein a driving unit is connected to one end of a roller shaft of the reversing roller, and a rotation position detecting unit is provided at the other end of the roller shaft. Forming equipment. 5. The image forming apparatus according to claim 4, wherein the driving unit is a stepping motor. 6. The image forming apparatus according to claim 1, wherein the reversing roller includes a plurality of roller units arranged along a width direction orthogonal to a conveying direction of a sheet to be conveyed. 7. The image forming apparatus according to claim 1, wherein the reversing roller has one wide roller portion at a central portion in a width direction orthogonal to a conveying direction of a sheet to be conveyed. 8. The image forming apparatus according to claim 1, wherein at least one of said reversing roller and said driven roller is a rubber roller. 9. Both ends of the roller shaft of the reversing roller and the roller shaft of the driven roller are respectively held by bearings, and the bearings are located on both sides of the reversing path in the width direction orthogonal to the sheet conveying direction in the reversing path. 9. The image forming apparatus according to claim 1, wherein the image forming apparatus is fixed to a side plate. 10. The reversing roller is held at a fixed position, and the driven roller is movably held in a direction to come into contact with and separate from the reversing roller, and is urged by urging means in a direction to contact the reversing roller. The image forming apparatus according to claim 1, wherein: 11. The image forming apparatus according to claim 1, wherein an outer peripheral portion on an upper end side of the driven roller slightly protrudes from a sheet guide surface of the reversing path. 12. A device according to claim 1, further comprising: a detection sensor for detecting a sheet fed into the reversing path; and a driving unit for reversing the reversing roller after a predetermined time has elapsed according to a detection result of the detection sensor. 12. The image forming apparatus according to any one of claims 11 to 11. 13. The image forming apparatus according to claim 12, wherein the detection sensor is provided at at least one of before and after a branch point between the paper conveyance path and the reversing path. 14. The image forming apparatus according to claim 12, wherein the detection sensor detects a trailing edge of the sheet. 15. The image forming apparatus according to claim 1, wherein the image forming unit is an electrophotographic image forming unit. 16. 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. 17. The image forming apparatus according to claim 1, wherein the image forming unit is a non-electrophotographic image forming unit. 18. The image forming apparatus according to claim 1, wherein the sheet is a card. 19. An image forming apparatus according to claim 1, an input terminal for receiving input of image data, and controlling the image forming apparatus to form an image based on the image data on a sheet. And a control unit for causing the printer to perform the operation. 20. An image reading device for reading an image of a document, the image forming device according to claim 1, and controlling the image reading device and the image forming device to read the image by the image reading device. And a control unit for causing the image forming apparatus to form an image based on image data of the original document on a sheet. 21. An image reading device for reading an image of a document, an image forming device according to claim 1, a transmitting / receiving device for transmitting / receiving image data to / from an external device via a network, The image reading device, the image forming device, and the transmitting / receiving device are controlled, and the image data of the document read by the image reading device is transmitted to the outside via a network by the transmitting / receiving device. A control unit for causing the image forming apparatus to perform image formation based on image data received from the outside on a sheet.