JPH11199142A - Sheet transfer device and picture image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce jamming of a sheet and to prevent conformity failure at the time of discharging the sheet by constituting an upstream rotor and a downstream rotor free to make content with and separate from a sheet transfer rotor interlocked with transfer passage change-over motion of a transfer passage change-over means. SOLUTION: A flapper 12 revolves, blocks a discharge passage and opens a carrier passage at the time of carrier motion of a first surface part of a sheet. At this time, a cam 32 revolves and separates an upstream roller 10 and a downstream roller 11 from a discharge roller 9. Consequently, the sheet simply passes a curl removal rotor A and stiffening is not carried out. Accordingly, it is possible to deliver the sheet to an intermediate tray without increasing a protruded curl on the sheet on the first surface of which picture image formation is carried out. The upstream roller 10 and the downstream roller 11 abut to the discharge roller 9 and are brought into pressure contact with each other by revolution of the cam 32 at the time of leading the sheet to the discharge passage. Thereafter, stiffening of the sheet passing through the curl removal rotor A is carried out and a curl is removed, the sheet is discharged to the discharge passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device provided in an image forming apparatus such as a copying machine, a facsimile machine, and a printer.

[0002]

2. Description of the Related Art Recently, the operation of an image forming apparatus such as a copying machine has been automated by systematization, and an apparatus having an automatic duplex copying mechanism and an automatic multiplex copying mechanism has been developed. In configuring the automatic double-sided copying mechanism or the automatic multiplex copying mechanism, a stock device generally called an intermediate tray is used, and a predetermined number of sheets having an image formed on the first surface of the sheet are temporarily stored in the intermediate tray. A method is used in which the image is formed again on the second surface (back surface) or on the same surface (first surface) of the sheet on which the image is formed on the first surface after being stocked and fed again to the image forming unit. Therefore, such a method is extremely effective especially when a large number of double-sided or multiple-copied sheets are prepared.

Conventionally, in order to enable double-sided copying or multiple copying, a sheet having an image formed on the first side is stored in an intermediate tray with the image side of the sheet facing upward during double-sided copying.
At the time of multiplex copying, a method of forming a double-sided image or a multiplex image by storing the sheet in an intermediate tray with the image side of the sheet facing downward and re-feeding the sheet from the intermediate tray is common.

In general, an image formed on a sheet is permanently fixed by passing through an image fixing device, but the sheet is easily curled by the heat of the image fixing device. It depends on the configuration of the fixing device, the image fixing temperature, and the like.

As shown in FIG. 9A, a sheet S having a toner image t ₁ formed on the first surface is a sheet having an A3, A4R size or the like which is long in the sheet conveying direction experimentally. The toner image t _{1 in} the transport direction a of S
As shown in FIG. 9B, the curl having a convex surface on the surface side and the curl having a convex surface on the toner image t ₁ surface in a direction (width direction) orthogonal to the conveying direction a of the sheet S tend to occur. is there.

When the sheet S on which an image is formed on the first surface and thus curled is discharged onto the intermediate tray and is to be stacked, a jam occurs when the sheet S is discharged onto the intermediate tray, When re-feeding from the intermediate tray to the image forming unit, there is a possibility that a feeding failure may occur.

Further, when the sheet size is experimentally A3, A4
For sheets that are long in the sheet conveyance direction, such as R size,
As shown in (a), after re-feeding from the intermediate tray, the second
In the sheet S on which the toner image t ₂ is formed on the surface (back surface), the curl of which the toner image t ₂ surface side is downwardly convex in the conveying direction a of the sheet S, or as shown in FIG. The toner image t _{2 in} a direction (width direction) orthogonal to the transport direction a
There is a tendency that the surface side is liable to be curled downwardly.

When the sheet S on which an image is formed on the second surface and thus curled is discharged onto each discharge tray (bin) via the sheet sorting device, the width of the sheet S in the sheet alignment is increased. When a curl having a downward convex shape is generated, the sheet S is not moved to a predetermined alignment position due to crushing of the sheet S, and there is a possibility that alignment failure may occur on each discharge tray (bin).

When a curl that is convex downward in the conveying direction a or the width direction of the sheet S is generated, the leading end of the curl is caught on the back surface of each of the discharge trays (bins) other than the lowermost one. There is a possibility that the sheet will not be moved to the predetermined alignment position, and alignment failure on each discharge tray (bin) will occur.

In order to prevent the defects caused by the influence of the curl as described above, a method of correcting the curl particularly when a curl having a downward convex in the conveying direction a or the width direction of the sheet S occurs. A plurality of pairs of curl removing rollers, in which two driven rollers urged and driven by a predetermined pressure on the outer peripheral surface of the rollers on the upstream side and the downstream side of the driving roller in the sheet conveying direction, are provided on the sheet conveying path, are provided. A method of correcting the curl by stiffening the sheet by passing the sheet through the sheet has been proposed.

Further, flanges are provided at both ends of the driven roller to correct the curl by stiffening the sheet by the flanges, and a drive of a pair of upper and lower rollers for conveyance provided immediately after the image fixing device. A flange portion is provided at both ends of the roller, a plurality of curl removing roller pairs in which a driven roller is brought into contact with a predetermined pressure are arranged, and the sheet is passed between the rollers to curl the sheet and curl the sheet. There is also proposed a method of correcting the above.

[0012]

However, although the above-described curl removing roller pair of the prior art is effective for one-way curl (curl having a downward convexity), as shown in FIG. In the state in which the toner image t ₁ is formed on the first surface of the sheet S, the sheet S has a curl with the toner image t ₁ surface convex upward, and after re-feeding from the intermediate tray, as shown in FIG. In a state where the toner image t ₂ is formed on the second surface (back surface) of the sheet S, the curl of the toner image t ₂ surface side is convex downward, and therefore, the curl in the opposite direction (curl upward convex). Then, it acts in a direction to amplify the curl.

That is, for a sheet having a sheet size such as A3 or A4R which is long in the sheet conveying direction, the first
Surface toner image is formed is accommodated in the intermediate toilet, refeeding Okunochi from the intermediate tray, as shown in FIG. 10, downwardly convex toner image t ₂ is formed on the second surface (back surface) Regarding the curled sheet S, the above-described curl removing roller pair of the conventional example acts in a direction for removing the curl formed on the sheet S, and discharges the sheet S onto a discharge tray via a sheet sorting device. In such a case, the above-described poor alignment can be prevented.

However, as shown in FIG. 9, for the sheet S on which the toner image t ₁ is formed on the first surface of the sheet S and the curl of which is convex upward, the above-described curl removing roller pair of the conventional example is used. Acts in a direction to amplify the curl formed on the sheet S, and there is a possibility that the occurrence of jams will increase during stacking on the intermediate tray or re-feeding from the intermediate tray.

The present invention has been made to solve the above problems, and
The purpose is to allow the sheet having the image formed on the first surface to be properly accommodated in the intermediate tray without promoting the upward curl, and the image to be formed on the second surface. And an image forming apparatus provided with the same, which can prevent a poor alignment when the sheet is discharged to a discharge tray via a sheet sorting device by removing a downwardly convex curl formed on the sheet. It is something you want to do.

[0016]

A typical configuration according to the present invention for achieving the above object is a first configuration for conveying a sheet.
A sheet conveyance path, a second sheet conveyance path for conveying the sheet, and conveyance path switching means for selectively switching the sheet conveyance path between the first sheet conveyance path and the second sheet conveyance path; A sheet conveying rotating body provided near a branch point between the first sheet conveying path and the second sheet conveying path and upstream of the conveying path switching unit in the sheet conveying direction; An upstream rotator provided upstream of the body in the sheet conveyance direction and pressed against the sheet conveyance rotator; and an upstream rotator provided downstream of the sheet conveyance rotator in the sheet conveyance direction. A downstream rotating body that is pressed against and is opposed to the sheet transport rotating body. The upstream rotating body and the downstream rotating body can be separated from and contacted with the sheet transport rotating body in conjunction with a transport path switching operation of the transport path switching unit. Configured A sheet conveying apparatus characterized by a.

Since the present invention is configured as described above, the upstream rotating body and the downstream rotating body can be separated from and brought into contact with the sheet transport rotating body in conjunction with the transport path switching operation of the transport path switching means. When the conveyance path is switched by the conveyance path switching means when the sheet on which the image is formed on the first surface is guided to the intermediate tray in the double-sided image formation mode or the multiple image formation mode, the upstream rotating body and the downstream rotating body are rotated by the sheet transport. The sheet can be satisfactorily conveyed and stored in the intermediate tray without promoting curling upwards formed on the sheet having the image formed on the first surface away from the body, and the sheet is re-fed from the intermediate tray. It is possible to reduce the jam that occurs when the operation is performed.

Further, when the conveyance path is switched by the conveyance path switching means when the sheet re-fed from the intermediate tray and having the image formed on the second surface is discharged out of the apparatus, an upstream rotating body and a downstream rotating body are used. Is brought into contact with a sheet conveying rotating body, and a sheet on which an image is formed on the second surface is stiffened, and the downwardly convex curl formed on the sheet is removed. It is possible to prevent poor alignment when discharging to the discharge tray.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment in which the present invention is applied to a copying machine as an example of a sheet conveying apparatus according to the present invention and an image forming apparatus having the same will be specifically described. FIG.
FIG. 2 is a schematic cross-sectional view showing the configuration of a first embodiment of an image forming apparatus provided with a sheet conveying device according to the present invention. FIG. 2 is a pair of curl removing rotary members serving as curl removing means of the first embodiment and a dedicated rotary member for transport. FIG. 3 is a schematic configuration diagram illustrating a configuration of a sheet conveying unit provided with a pair. FIG. 3 illustrates an upstream rotating body and a downstream rotating body with respect to a sheet conveying rotating body in conjunction with a transport path switching operation of a transport path switching unit in the first embodiment. FIG. 4 and FIG. 5 are perspective views showing the structure of a mechanism for separating and contacting the upper and lower rotating members in the first embodiment. It is a figure which shows a mode that it comes and goes.

First, the configuration of an image forming apparatus provided with a sheet conveying device according to the present invention will be described with reference to FIG.
The image forming apparatus 1 shown in FIG. 1 conveys a sheet S fed in a direction indicated by an arrow b in FIG. Then, the skew is removed by the registration roller pair 3 and the electrophotographic photosensitive drum 4 serving as an image forming means is removed.
The sheet S is conveyed between the photosensitive drum 4 and the transfer charger 5 facing the photosensitive drum 4 in synchronization with the rotation of.

On the other hand, a uniformly charged surface of the photosensitive drum 4 is irradiated with a laser beam corresponding to image information to form an electrostatic latent image, and toner is supplied to the electrostatic latent image by a developing sleeve 6. Then, the toner image is visualized.

The sheet S conveyed by the pair of registration rollers 3 is conveyed to an image forming section between the photosensitive drum 4 and the transfer charger 5, and is formed on the surface of the photosensitive drum 4 by the action of the transfer charger 5. The transferred toner image is transferred to the sheet S.

The sheet S on which the toner image is formed is conveyed by a conveying belt 7 to an image fixing device 8 serving as fixing means.
The toner image is permanently fixed by being heated and pressed by a heating roller 8a and a pressure roller 8b provided in the image fixing device 8.

The sheet S discharged from the image fixing device 8 has a discharge roller 9 serving as a sheet conveying rotating body which is a feature of the present invention.
After being appropriately decurled by a curl removing rotary member pair A, which is a curl removing device including an upstream roller 10 serving as an upstream rotating member and a downstream roller 11 serving as a downstream rotating member, a flapper 12 serving as a transport path switching unit. And a discharge path 13 serving as a first sheet conveying path for discharging the sheet S to the outside of the apparatus when the single-sided image forming mode or when all the image formation on the sheet S is completed, and a double-sided image forming mode or a multiple image forming mode At this time, the sheet S is appropriately selected and conveyed to a conveyance path 15 serving as a second sheet conveyance path for guiding the sheet S to the intermediate tray 14.

The curl removing rotary member pair A is located near the branch point between the discharge path 13 and the transport path 15 and upstream of the flapper 12 in the sheet transport direction (the direction of arrow a in the figure) (hereinafter simply referred to as “upstream side”). The discharge roller 9, the upstream roller 10, and the downstream roller 11 are formed of an elastic body such as a rubber material on the surface, and the upstream roller 10 is disposed on the discharge roller 9 on the upstream side of the discharge roller 9. The downstream roller 11 is elastically pressed against the discharge roller 9 so that the downstream roller 11 can be elastically pressed against the discharge roller 9 downstream of the discharge roller 9 in the sheet conveyance direction (hereinafter, simply referred to as “downstream side”). Has become.

A sheet sorting device 16 is provided further downstream of the discharge path 13. The sheet S is discharged by the action of the flapper 12 in the single-sided image forming mode or when all the images have been formed on the sheet S. The sheet S discharged from the discharge path 13 by the discharge roller pair 25 from the discharge path 13 is sorted by a sheet sorter 16 and selectively placed on a plurality of discharge trays (bins) 17 provided in the sheet sorter 16. Is discharged.

The sheet S discharged to the outside of the apparatus from the discharge roller pair 25 through the discharge path 13 is guided to the sheet sorting device 16,
The sheet S is conveyed by conveying rollers 26 and 27 provided in the sheet sorting device 16, and is sorted and discharged onto each discharge tray 17 by a discharge roller pair 28. The discharged sheet S is moved to a predetermined position by an alignment bar (not shown) and aligned on the discharge tray 17.

The sheet S on which image formation on the first side has been completed in the double-sided image forming mode or the multiple image forming mode is guided to the conveying path 15 by the action of the flapper 12, and in the double-sided image forming mode, the sheet S is turned by the U-turn unit 18. The sheet is inverted and stored in the intermediate tray 14 with the first surface facing upward, and is selectively discharged from the discharge units 20a and 20b according to the size of the sheet S by the action of the flappers 19a and 19b in the multiple image forming mode. It is stored in the intermediate tray 14 with the surface facing down.

The sheet S accommodated in the intermediate tray 14 is re-fed by the re-feed roller 21, conveyed by the conveying roller pair 2, and registered again by the registration roller pair 3, and the same as described above. After the desired double-sided image formation or multiplex image formation is performed, the sheet is discharged from a discharge path 13 onto a discharge tray (bin) 17 via a sheet sorting device 16.

Discharge roller 9 of the curl removing rotary member pair A
Is a drive-side roller that is driven to rotate by a motor (not shown), and the upstream roller 10 and the downstream roller 11
And a driven roller that rotates in accordance with the rotation of the discharge roller 9 when pressed against the roller.

As shown in FIG. 2, the curl-removing rotary member pair A is in the widthwise direction (width 210 mm) of an A4R size sheet S.
A pair (two) is provided corresponding to the position where both side edges of the sheet S pass, and the curl removing rotary member A carries the sheet S that has passed through the image fixing device 8 and removes the curl by crimping. ing.

A4 is provided on the rotating shaft 22 of the discharge roller 9.
A drive-side roller 23 serving as a pair of rollers dedicated to conveyance is provided at a position other than both ends in the short direction (width 210 mm) of the R-size sheet S.
And a plurality of driven-side rollers 24 that are pressed against the driving-side rollers 23 and driven to rotate.

FIG. 3 shows a flapper serving as a conveyance path switching means.
A link for moving the upstream roller 10 serving as the upstream rotating body and the downstream roller 11 serving as the downstream rotating body in contact with the discharge roller 9 serving as the sheet conveying rotating body in conjunction with the switching operation between the discharge path 13 and the conveying path 15 of FIG. FIG. 3 is a perspective view illustrating a configuration of a mechanism.

As shown in FIG. 3, the upstream roller 10 and the downstream roller 11
The bracket 29 is rotatably supported about a shaft 31a with respect to a bracket 31 fixed at one end to a leaf spring 30 fixed to an apparatus frame (not shown). With the above configuration, the upstream roller 10 and the downstream roller 11 can be uniformly pressed against the discharge roller 9 by the urging force of the leaf spring 30.

The other end of the bracket 31 fixed to the leaf spring 30 is engaged with a cam 32 that rotates around a rotation shaft 32a, and is connected to a drive shaft 33a of a solenoid 33.
The rotation of the rotation shaft 32a through the rotation of the cam 32
Is rotated, and the cam 32 is rotated about an axis of rotation 32a by an arrow c in FIG.
The upstream roller 10 and the downstream roller 11 are separated from the discharge roller 9 by rotating in the direction to abut and engage the bracket 31 and push up the bracket 31 against the urging force of the leaf spring 30.
Similarly, the cam 32 is rotated about the rotation shaft 32a by an arrow d in FIG.
By rotating in the direction, the upstream roller 10 and the downstream roller 11 are pressed against the discharge roller 9 by the urging force of the leaf spring 30.

On the other hand, a rotating shaft 12a to which the flapper 12 is fixed is fixed to the link 34, and a driving shaft of the solenoid 33 is fixed.
The pivot shaft 12a is rotated via the link 34 by the pushing / pulling-out operation of the 33a to rotate the flapper 12.

Accordingly, when the sheet S is guided to the transport path 15 to accommodate the sheet S in the intermediate tray 14 during the transport operation of the first surface of the sheet S in the multiple image forming mode or the duplex image forming mode, The solenoid 33 turns ON, and the link 34
The drive shaft 33a of the solenoid 33 is retracted in the direction of the arrow h in FIG. 3 against the tensile force of the tension coil spring 37 engaged with a part of the flapper 12, and the flapper 12 fixed to the rotary shaft 12a rotates. 3 is rotated in the direction of arrow i in FIG.
13 is closed and the transport path 15 is opened.

At this time, the link 35 is pulled back in the direction of the arrow j in FIG. 3, and the cam 32 rotates about the rotation shaft 32a in the direction of the arrow c in FIG. 3 via the link 36 and the rotation shaft 32a. The upstream roller 10 and the downstream roller 11 are connected to the discharge roller 9 as shown in FIG.
The sheet S is separated from the sheet and simply passes through the pair of curl removing rotary members A and is not crimped. After being guided to the transport path 15, the sheet S is stored in the intermediate tray 14.

As a result, in the case of a sheet S of a size such as A3 or A4R, which is long in the conveying direction of the sheet S, as described above with reference to FIG. The sheet S can be sent to the intermediate tray 14 without promoting the curl that tends to curl upward, so that the sheet S is stored and stacked in the intermediate tray 14, and the image is formed by the re-feed roller 21 from the intermediate tray 14. It is possible to prevent a jam that occurs when the sheet is fed again to the forming section.

Further, when all the images have been formed on the sheet S in the single-sided image forming mode or the multiple image forming mode, or when the sheet S in the double-sided image forming mode
When the sheet S is guided to the discharge path 13 in order to discharge the sheet S to the outside of the machine during the conveyance operation of the surface, the solenoid 33 is turned off.
The drive shaft 33a of the solenoid 33 is pushed out in the direction of arrow e in FIG. 3 by the pulling force of the pulling coil spring 37 engaged with a part of the link 34, and the flapper 12 fixed to the rotating shaft 12a is rotated. By rotating around the moving shaft 12a in the direction of arrow f in FIG. 3, the transport path 15 is closed and the discharge path 13 is opened.

At this time, the link 35 is pushed out in the direction of arrow g in FIG. 3, and the cam 32 rotates in the direction of arrow d in FIG. 3 around the rotation shaft 32a via the link 36 and the rotation shaft 32a. As shown in FIG. 5, the upstream roller 10 and the downstream roller 11
After the sheet S passing through the curl removing rotary member pair A and being pressed against the sheet A to remove the curl, the sheet S
Discharge to 13.

In the present embodiment, the curl removing rotary member pair A is arranged near the downstream side of the image fixing device 8, so that the sheet S heated after passing through the image fixing device 8 is still hot. And the curl can be effectively corrected.

Therefore, in the sheet S having a long size in the conveyance direction of the sheet S such as A3 or A4R in the double-sided image forming mode by the above-described operation, the image is experimentally formed on the second surface as shown in FIG. The curl of the sheet S having a tendency to curl convexly below the formed sheet S can be corrected by curling the sheet S by the curl removing rotating body pair A, and the sheet S is discharged from the discharge path 13 to the outside of the machine, and is corrected. When the sheet S is discharged onto the discharge tray 17 via the sorting device 16, it is possible to prevent an alignment failure when aligning the sheet S with an alignment rod (not shown).

Normally, in the image forming apparatus 1 equipped with a plurality of feed cassettes, a plurality of types of fixed-size sheets S, which are widely spread in the market, are stored and selectively fed as the sheets S to be fed. Often used. Therefore, by arranging one set of the curl removing rotary member A for correcting the downward convex curl formed on the sheet S about the width of the A4R size sheet S as described above, it is possible to experimentally obtain various sizes. It has been found that the downward curl of the sheet S can be effectively corrected and has an advantageous arrangement.

As another configuration, a flange (flange) may be provided at the ends of the upstream roller 10 and the downstream roller 11 so as to promote curl correction.

Next, a second embodiment of the sheet conveying apparatus according to the present invention and an image forming apparatus having the same will be described with reference to FIGS. FIGS. 6 and 7 show the second embodiment of the sheet conveying apparatus according to the present invention, in which the upstream rotating body, the downstream rotating body, and the intermediate rotating body move with respect to the sheet conveying rotating body in conjunction with the conveying path switching operation of the conveying path switching means. FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The curl removing rotary member pair B of the present embodiment is arranged in the sheet conveying direction with the upstream roller 10 of the first embodiment.
Intermediate roller 41 serving as an intermediate rotating body between the roller and the downstream roller 11
Are rotatably supported by a bracket 29, and as shown in FIGS. 6 and 7, the upstream roller 10, the downstream roller 11, and the intermediate roller
41 is configured to be integrally detachable from the discharge roller 9.

The surface of the intermediate roller 41 is also made of an elastic material such as rubber, and the intermediate roller 41 is elastically opposed to the discharge roller 9 downstream of the upstream roller 10 and upstream of the downstream roller 11. Can be pressed against.

According to the above configuration, even when the sheet S is used or used frequently, such as old paper or recycled paper (recycled paper), which tends to have a large amount of curl having a downward convexity experimentally, the sheet S is removed by the curl removing rotary body pair B. The curl of the sheet S can be more effectively corrected by strengthening the stiffness of the sheet S.

Further, similarly to the first embodiment, flanges (flanges) may be provided at the ends of the upstream roller 10, the downstream roller 11, and the intermediate roller 41 to promote curl correction. . Other configurations are the same as those of the first embodiment, and similar effects can be obtained.

Next, a third embodiment of the sheet conveying apparatus according to the present invention and an image forming apparatus having the same will be described with reference to FIG. FIG. 8 is a schematic configuration diagram showing a configuration of a sheet transporting unit provided with a curl removing rotary body pair and a transport-only rotary body pair according to a third embodiment of the sheet transport apparatus according to the present invention.

In the present embodiment, the position corresponds to the position where both ends in the short direction (297 mm width) of the A3-size sheet pass through the curl removing rotary members A and B and the cam 32 of the first and second embodiments. It is provided. Other configurations are the first,
The configuration is the same as that of the second embodiment, and similar effects can be obtained.

In the present embodiment, when the sheet S of the A3 size is used as a sheet S by the above-described configuration, and the sheet S is used frequently, the curl removing rotary members A and B for correcting the curl having a downward convexity are A3.
By arranging one set about the width of the sheet S of the size, it is possible to effectively correct the downward convex curl in the sheet S of the A3 size.

[0054]

Since the present invention has the above-described configuration and operation, the upstream rotating body and the downstream rotating body are separated from and connected to the sheet transport rotating body in conjunction with the transport path switching operation of the transport path switching means. With this configuration, when the conveyance path is switched by the conveyance path switching unit when the sheet on which the image is formed on the first surface is guided to the intermediate tray in the double-sided image forming mode or the multiple image forming mode, the upstream rotating body and The downstream rotating body is separated from the sheet conveying rotating body, and the sheet can be satisfactorily conveyed and accommodated in the intermediate tray without promoting the upward curl formed on the sheet having the image formed on the first surface. Can be reduced when the paper is re-fed.

When the conveyance path is switched by the conveyance path switching means when the sheet re-fed from the intermediate tray and having the image formed on the second surface is discharged out of the apparatus, the upstream rotating body and the downstream rotating body are switched. Is brought into contact with the sheet conveying rotating body to stiffen the sheet on which the image is formed on the second surface, and the curl having a downward convexity formed on the sheet is removed to thereby discharge the sheet via the sheet sorting apparatus. Misalignment of the sheet when the sheet is discharged to the printer.

In the case where an intermediate rotating body is arranged between the upstream rotating body and the downstream rotating body in the sheet conveying direction,
Even when sheets such as used paper and recycled paper are used regularly or frequently, it is preferable because the curl having a downward convexity can be more effectively corrected by stiffening the sheet.

Further, by arranging one set of the curl removing rotating body pair including the sheet conveying rotating body, the upstream rotating body, the downstream rotating body, and the intermediate rotating body around the width of the A4R size sheet, various sizes of sheets are provided. The curl of the downwardly convex curl can be effectively corrected, which is advantageous.

Further, by arranging one pair of the above-described curl removing rotary members about the width of an A3-size sheet, it is possible to effectively correct a downwardly convex curl in an A3-size sheet.
This is advantageous when the A3 size sheet S is used regularly or frequently.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a configuration of a first embodiment of an image forming apparatus including a sheet conveying device according to the present invention.

FIG. 2 is a schematic configuration diagram illustrating a configuration of a sheet conveying unit provided with a curl removing rotary body pair serving as a curl removing unit and a transport dedicated rotary body pair according to the first embodiment.

FIG. 3 is a perspective view illustrating a configuration of a mechanism that moves an upstream rotating body and a downstream rotating body toward and away from a sheet conveying rotating body in conjunction with a conveying path switching operation of a conveying path switching unit in the first embodiment.

FIG. 4 is a diagram illustrating a state in which an upstream rotating body and a downstream rotating body are separated from and brought into contact with a sheet conveying rotating body in conjunction with a conveying path switching operation of a conveying path switching unit in the first embodiment.

FIG. 5 is a diagram illustrating a state in which an upstream rotating body and a downstream rotating body are separated from and brought into contact with a sheet conveying rotating body in conjunction with a conveying path switching operation of a conveying path switching unit in the first embodiment.

FIG. 6 is a perspective view of a sheet conveying apparatus according to a second embodiment of the present invention, in which an upstream rotating body, a downstream rotating body, and an intermediate rotating body are separated from a sheet conveying rotating body in conjunction with a conveying path switching operation of a conveying path switching unit; It is a figure which shows a mode that it contacts.

FIG. 7 is a perspective view of a sheet conveying apparatus according to a second embodiment of the present invention, in which an upstream rotating body, a downstream rotating body, and an intermediate rotating body are separated from a sheet conveying rotating body in conjunction with a conveying path switching operation of a conveying path switching unit; It is a figure which shows a mode that it contacts.

FIG. 8 is a schematic configuration diagram showing a configuration of a sheet transporting unit provided with a curl removing rotary member pair and a transport-specific rotary member pair of a third embodiment of the sheet transport device according to the present invention.

FIG. 9 is a diagram illustrating a conventional example.

FIG. 10 is a diagram illustrating a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Convey roller pair, 3 ... Register roller pair, 4 ... Photoreceptor drum, 5 ... Transfer charger, 6 ... Developing sleeve, 7 ... Convey belt, 8 ... Image fixing device, 8a ... Heating roller , 8b: pressure roller, 9: discharge roller, 10: upstream roller, 11: downstream roller, 12: flapper, 12a: rotating shaft, 13: discharge path, 14: intermediate tray, 15: transport path, 16: sheet Sorting device, 17: discharge tray, 18: U-turn section, 19
a, 19b: flapper, 20a, 20b: discharge section, 21: re-feed roller, 22: rotating shaft, 23: drive side roller, 24: driven side roller, 25: discharge roller pair, 26, 27: transport roller, 28: discharge roller pair, 29: bracket, 30: leaf spring, 31: bracket, 31a: shaft, 32: cam, 32a: rotary shaft, 33: solenoid, 33a: drive shaft, 34, 35, 36: link, 37: tension coil spring, 41: intermediate roller, A, B: curl removing rotary body pair, S: sheet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 21/14 G03G 21/00 372

Claims (10)

[Claims] 1. A sheet conveying device provided in an image forming apparatus capable of forming an image on both sides of a sheet, the sheet conveying device having a curl removing unit provided downstream of a fixing unit for fixing an image in a sheet conveying direction. 5. The sheet conveying apparatus according to claim 1, wherein the curl removing unit is not operated in the conveying operation of the first surface of the sheet, and the curl removing unit is operated in the conveying operation of the second surface of the sheet. apparatus. 2. The sheet conveying apparatus according to claim 1, wherein the curl removing unit is disposed on the sheet conveying path between a conveying path switching unit that switches a sheet conveying path and the fixing unit. . 3. A first sheet conveying path for conveying a sheet, a second sheet conveying path for conveying a sheet, and a sheet conveying path including the first sheet conveying path and the second sheet conveying path. A conveying path switching unit for selectively switching the sheet conveying path between the first sheet conveying path and the second sheet conveying path, and provided upstream of the conveying path switching unit in the sheet conveying direction. A sheet conveying rotator, an upstream rotator provided upstream of the sheet conveying rotator in the sheet conveying direction and pressed against the sheet conveying rotator, and a sheet conveying direction higher than the sheet conveying rotator. A downstream rotating body provided on the downstream side and pressed against the sheet transporting rotating body, wherein the upstream rotating body and the downstream rotating body are interlocked with a transport path switching operation of the transport path switching means. Before Sheet conveying apparatus characterized by the disjunction can configured with respect to the sheet conveying rotating body. 4. A sheet conveyance direction switching means which is disposed between the upstream rotation body and the downstream rotation body in the sheet conveyance direction and is pressed against the sheet conveyance rotation body so as to interlock with a conveyance path switching operation of the conveyance path switching means. 4. The sheet conveying apparatus according to claim 3, further comprising an intermediate rotator configured to be able to contact and separate from the sheet conveying rotator. 5. The upstream rotating body and the downstream rotating body, or the upstream rotating body, the downstream rotating body, and the intermediate rotating body are rotatably supported by a bracket, and are used for a transport path switching operation of the transport path switching means. An interlocking cam can be brought into contact with the bracket to separate the upstream rotating body and the downstream rotating body, or the upstream rotating body, the downstream rotating body, and the intermediate rotating body from the sheet conveying rotating body. The sheet conveying device according to claim 3, wherein the sheet conveying device is configured as follows. 6. A curl removing rotating body pair comprising the upstream rotating body and the downstream rotating body, or the upstream rotating body, the downstream rotating body, the intermediate rotating body, and the sheet transporting rotating body, the A4 size sheet. 6. The device according to claim 3, wherein the side end portions in the lateral direction are provided at positions corresponding to the passing portions.
The sheet conveying device according to any one of the above. 7. A curl removing rotating body pair comprising the upstream rotating body and the downstream rotating body, or the upstream rotating body, the downstream rotating body, the intermediate rotating body, and the sheet transporting rotating body, is used for an A3-size sheet. 6. The device according to claim 3, wherein the side end portions in the lateral direction are provided at positions corresponding to the passing portions.
The sheet conveying device according to any one of the above. 8. An image forming apparatus provided with the sheet conveying device according to claim 1 in a sheet discharge section, wherein an image on a first side of the sheet in a double-sided image forming mode and a multiple image forming mode is provided. An image forming apparatus comprising: an intermediate tray that temporarily stores the sheet after the forming operation is completed; and a sheet sorting device provided downstream of the sheet conveying device in a sheet conveying direction. 9. An image forming apparatus provided with the sheet conveying device according to claim 3 in a sheet discharge unit, wherein said upstream rotating body and said downstream rotating body, or said upstream rotating body and said upstream rotating body are provided. The downstream rotator and the intermediate rotator are separated from the sheet transport rotator in the transport operation of the first surface of the sheet in the duplex image forming mode, and come into contact with the sheet transport rotator in the transport operation of the second surface of the sheet. An image forming apparatus comprising: 10. An image forming apparatus provided with the sheet conveying device according to claim 3 in a sheet discharge section, wherein said upstream rotating body and said downstream rotating body, or said upstream rotating body and said upstream rotating body are provided. An image forming apparatus, wherein the downstream rotating body and the intermediate rotating body come into contact with the sheet conveying rotating body in a sheet conveying operation in a one-sided image forming mode.