JP2000035725A - Sheet carrying device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet carrying device capable of flattening the curl of a sheet even when the curl direction of the sheet is different. SOLUTION: In this sheet carrying device 18; the sheets 3a and 3b after passing through a fixing device 15 are carried to a downstream side along a sheet carrying path 20, and a pair of curl flattening paths 25 and 26 curving the sheets 3a and 3b in a reverse direction to the curl direction of the sheets 3a and 3b is formed halfway through the path 20 corresponding to the curl on both sides of the sheets 3a and 3b, then two pairs of carrying rollers 22 and 23 are respectively arranged in a pair of paths 25 and 26. Therefore, the curled sheets 3a and 3b heated and pressured by the device 15 are curved in the reverse direction to the curl direction by any of the paths 25 and 26, and forcibly carried along the paths 25 and 26 by the pairs of carrying rollers 22 and 23, whereby they are made stiff in the reverse direction to the curl direction so that the curl is flattened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus for conveying a sheet after passing through a fixing device, and an image forming apparatus such as a copying machine, a printer, a facsimile, etc. provided with the sheet conveying apparatus. And an image forming apparatus.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional image forming apparatus 30 to which electrophotographic technology is applied. As shown in FIG. 3, the image forming apparatus 30 applies a photoconductor 3 to a sheet (paper as a transfer body) 32 sent out from a sheet supply unit 31.
3 is transferred by the transfer device 34, and then the sheet on which the toner is transferred is heated and fixed by the fixing device 35.
Pressure is applied to fix the toner on the sheet 32. Then, the fixed sheet 32a is conveyed to a sheet discharge tray (not shown), a double-sided printing unit, a sheet post-processing device, or the like by a sheet conveying device 36.

[0003]

However, the sheet 32 used in the image forming apparatus 30 to which the above-described electrophotographic technology is applied expands and contracts due to adsorption and desorption of moisture. Curls when pressed. When the sheet 32a is curled in this manner, the sheet 32a jams in the sheet transport path 37 or in a double-sided printing unit or a sheet post-processing device connected to the sheet transport path 37, and the curl portion 32b at the leading end of the sheet 32a is bent. Causes inconveniences such as Therefore, it is necessary to correct the sheet curl in order to improve the sheet transportability and prevent the leading end of the sheet 32a from bending.

The curl direction and amount of the sheet 32a vary depending on the material of the sheet, the difference in fiber orientation between the front and back of the sheet, environmental conditions such as relative humidity and temperature, and various conditions such as a moisture release surface.

Accordingly, an object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus which can correct a sheet curl even when the direction of the sheet curl is different.

[0006]

SUMMARY OF THE INVENTION The present invention is a sheet conveying apparatus for conveying a sheet after passing through a fixing device to a downstream side along a sheet conveying path, wherein the sheet is transported in a direction opposite to a curl direction of the sheet. A pair of curl correction paths to be bent are formed in the middle of the sheet conveyance path so as to correspond to curls on both sides of the sheet, and a pair of conveyance rollers are arranged on the pair of curl correction paths. I have.

According to the present invention having such a configuration, a sheet curled by being heated and pressed by a fixing device is curved in a direction opposite to the curl direction on a curl correcting path.
By being forcibly conveyed along the curl correction path by the pair of conveying rollers, a curl in the direction opposite to the curl direction is provided, and the curl is corrected. Here, since the curl correction path is formed as a pair so as to correspond to the curl on both the front and back sides of the sheet, even if the sheet curls in either direction, the curl of the sheet is curled by the curl correction path and the conveying roller pair. Be corrected.

Further, in the present invention, the pair of curl correcting paths are formed so as to be branched into two from the middle of the sheet conveying path and then to join on the downstream side.

With this configuration, a pair of curl correction paths can be formed at the same portion of the sheet transport path, and the length of the sheet transport path can be shortened. Can be achieved.
That is, when a pair of curl correction paths are separately arranged on the upstream side and the downstream side of the sheet conveyance path, the sheet conveyance path becomes long.

[0010] The present invention also provides the transport roller pair,
A transport roller disposed outside the curl correction path is formed of a soft material, and a transport roller disposed inside the curl correction path is formed of a hard material.

According to such a configuration, the transport roller made of a soft material comes into contact with the outer periphery of the transport roller made of a hard material in a deformed state, and both transport rollers come into contact with a sufficiently large area. Therefore, the sheet in the curl correction path is
The transfer roller made of a soft material is pressed with a sufficient area against the outer periphery of the transfer roller made of a hard material. Here, since the conveyance roller made of a hard material is arranged inside the curl correction path, the sheet is squeezed between the two conveyance rollers in the direction opposite to the curl direction, and the sheet has sufficient waist in the direction opposite to the curl direction. Will be attached to

Further, the image forming apparatus of the present invention comprises a transfer device for transferring a toner image on a photoreceptor to a sheet sent from a sheet supply means, and a fixing device for fixing toner to the sheet after passing the transfer device. , And the above-mentioned sheet conveying device.

The image forming apparatus having such a configuration can correct the curl of a sheet by the sheet conveying apparatus. It is possible to prevent occurrence of conveyance failure such as jam caused by curling,
Sheet conveyance performance is improved.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention. As shown in FIG. 1, the sheet 3 stacked on the sheet feed tray 2 is sent to the nip portion between the feed roller 5 and the reverse roller 6 by the pickup roller 4, and only one sheet is separated and the registration roller pair 7 is separated. Transported to The registration roller pair 7 feeds the sheet 3 between the photoconductor 8 and the transfer roller (transfer device) 10 so that the front end of the toner image on the photoconductor 8 and the front end of the sheet match. Then, the toner image on the photoconductor 8 is transferred to the sheet fed between the photoconductor 8 and the transfer roller 10. Here, the cleaning device 1 is provided around the photoconductor 8.
1, a charging device 12, a developing device 13, and an optical unit 14 are arranged.

The sheet on which the toner image has been transferred is formed by a heating roller 16 and a pressure roller 17 which constitute a fixing device 15.
And heated and pressed by the heating roller 16 and the pressing roller 17. Thereby, the toner image is fixed on the sheet.

Downstream side of the fixing device 15 (left side in FIG. 1)
Is connected to a sheet conveying device 18. As shown in detail in FIG. 2, the sheet conveying device 18 includes a sheet conveying path 20 for guiding the sheet 3 after passing through the fixing device 15 to a downstream side, and a conveying roller pair 21 disposed in the sheet conveying path 20. To 24.

The sheet conveying path 20 is formed with a pair of curl correcting paths 25 and 26 that are formed so as to branch into two branches in the middle and then join at the downstream side. The pair of curl correction paths 25 and 26 include a first curl correction path 25 protruding so as to curve upward in the figure and a second curl correction path 26 protruding so as to curve downward in the figure. ing.

As shown in FIG. 2, the first curl correcting path 25 smoothly guides the sheet 3a curled upward (sheet surface side) in the figure.
A first curl straightening path leading end 25 that gently slopes upward from the upstream side end 20a of the sheet conveying path 20 and branches off in the figure.
a, a top 25b connected to the first curl straightening path leading end 25a, and the top 25b and the downstream sheet conveying path 2
0b is formed with a first curl correction path rear end portion 25c that is connected to the first curl correction path at a gentle inclination.

As shown in FIG. 2, the second curl correction path 26 is provided so that the sheet 3b curling downward (in the back side of the sheet) can be smoothly guided. A second curl correction path leading end portion 26a that gently slopes downward from the upstream end portion 20a and branches off in the figure;
The top 2 connected to the second curl correction path tip 26a
6b, and a rear end 26c of a second curl straightening path that connects the top 26b and the downstream sheet conveying path 20b with a gentle inclination.

Then, the first curl straightening path 25 and the second
Conveying roller pairs 22 and 23 are disposed at the tops 25b and 26b of the curl correction path 26, respectively. Here, the transport roller pairs 22 and 23 are located outside the first curl correction path 25 (upper side in FIG. 2) and outside the second curl correction path 26 (lower side in FIG. 2). 23a is made of a soft material (for example, foamed resin such as sponge, foamed rubber,
First curl straightening path 2 made of ceramic sponge)
5 (lower in FIG. 2) and the inside of the second curl correction path 26 (upper in FIG. 2).
b is a hard material (for example, hard rubber, resin, metal such as iron)
It is formed with.

With this configuration, the outer transport rollers 22a, 23a and the inner transport rollers 22b, 2
By increasing the contact area of the sheet 3a and the sheet 3a, 3b with a large area against the outer periphery of the inner conveying rollers 22b, 23b, the sheets 3a, 3b are squeezed at the nip portion of the pair of conveying rollers 22, 23, Sheets 3a, 3
b is bent in the direction opposite to the curl direction, and the sheets 3a, 3
The waist in the direction opposite to the curl direction can be attached to b. As a result, the curl correction paths 25 and 26 and the conveying roller pair 2
Sheet curls can be corrected by means of 2 and 23.

As described above, the sheets 3a1 and 3b1 that have passed the curl correction paths 25 and 26 and have been curled are
Discharge roller pair 2 arranged in downstream sheet conveyance path 20b
4, the sheet is conveyed to the sheet discharge tray 27, a duplex printing unit (not shown), or a sheet post-processing device (not shown).

As described above, according to the present embodiment, even if the sheet 3 that has passed through the fixing device 15 is curled to either the front side or the back side, the curled sheets 3a and 3b are moved to the first side. The sheet 3a, 3b is guided by the first curl correction path 25 or the second curl correction path 26, and the sheets 3a, 3b are squeezed by the conveying roller pairs 22, 23 disposed on the tops 25b, 26b of the curl correction paths 25, 26. Can be curved in the direction opposite to the curl direction to correct the curl of the sheets 3a and 3b. Therefore, the uncurled sheets 3a1 and 3b1 are discharged to the sheet conveying path 20 (20b) downstream of the curl correcting paths 25 and 26. As a result, the sheets 3a1 and 3b1 on the downstream side of the curl correction paths 25 and 26 do not cause jam due to curl in the downstream sheet conveyance path 20b.

Further, according to the present embodiment, even when a duplex printing unit or a sheet post-processing device (not shown) is connected downstream of the curl correction paths 25 and 26, the inside of the duplex printing unit or the sheet post-processing device is not used. Does not cause jam due to curling.

As a result, the sheet conveying performance of the sheet conveying device 18 and the image forming apparatus 1 including the sheet conveying device 18 is improved, and the reliability of the sheet conveying device 18 and the image forming device 1 is improved.

In the present embodiment, the first curl correcting path 25 and the second curl correcting path 26 are formed by straight curl correcting path tips 25a, 26a, tops 25b, 26b,
Although it is formed at the rear end portions 25c and 26c of the curl correction path, it is not limited to this and may be formed in a curved shape. However,
Also in this case, the leading end of the first curl correction path 25 and the second curl so that the curled sheets 3a and 3b can be smoothly guided into the first curl correction path 25 or the second curl correction path 26. The front end of the correction path 26 is formed so as to branch from the upstream end 20a of the sheet conveying path 20 at a gentle angle.

In this embodiment, the first curl straightening path 25 and the second curl straightening path 26 are bifurcated. However, the present invention is not limited to this.
The fifth and second curl correcting paths 26 may be formed separately on the upstream side and the downstream side of the sheet conveying path 20. However,
According to the aspect of the above embodiment, the first curl correction path 2
5 and the second curl correcting path 26 are formed at the same position of the sheet conveying path 20, so that the length of the sheet conveying path 20 can be shortened, the size of the sheet conveying apparatus 18 can be reduced, and thus the sheet conveying can be performed. The size of the image forming apparatus 1 including the device 18 can be reduced.

[0029]

As described above, according to the present invention, a sheet curled by heating and pressurizing by a fixing device is curved in a direction opposite to the curl direction on a curl correcting path, and is carried along a curl correcting path by a pair of conveying rollers. By forcibly conveying the sheet, a stiffness in the direction opposite to the curl direction can be provided to the sheet, so that the sheet can be curled. here,
According to the present invention, since the curl correction path is formed as a pair so as to correspond to curls on both sides of the sheet, the curl of the sheet is performed by the curl correction path and the conveying roller pair even if the sheet is curled in either direction. Can be corrected.

Further, according to the present invention, since the pair of curl correction paths are formed so as to branch from the middle of the sheet transport path into two branches and then join downstream, the length of the sheet transport path is reduced. Therefore, the size of the sheet conveying device can be reduced.

Further, according to the present invention, of the transport roller pairs, the transport roller disposed outside the curl correction path is formed of a soft material, and the transport roller disposed inside the curl correction path is formed of a hard material. Therefore, the sheet is pressed against the outer peripheral surface of the hard material conveying roller by the deformed soft material conveying roller, so that the contact area between the sheet and the hard material conveying roller is increased, and the sheet is moved between the two conveying rollers. The sheet is squeezed in the direction opposite to the curl direction, so that the sheet has sufficient waist in the direction opposite to the curl direction. As a result, according to the present invention, the curl correcting function is further enhanced.

Further, since the image forming apparatus of the present invention is provided with the sheet conveying device having the sheet curl correcting function, it is possible to prevent the occurrence of a jam due to the curl of the sheet and to improve the sheet conveying performance. Can be improved.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a part of FIG. 1 (an enlarged view of a sheet conveying device).

FIG. 3 is a schematic configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Paper feed tray (sheet supply means), 3, 3a, 3b ... Sheet, 8 ... Photoconductor, 10
... Transfer roller (transfer device), 15 fixing device, 18 sheet transport device, 20 sheet transport path,
22, 23 ... Conveying roller pair, 22a, 22b, 23
a, 23b: conveyance roller, 25, 26: curl correction path

Claims (4)

[Claims] 1. A sheet conveying device that conveys a sheet that has passed through a fixing device to a downstream side along a sheet conveying path, wherein a curl correcting path for curving the sheet in a direction opposite to a curl direction of the sheet is provided. A sheet conveying apparatus, wherein a pair is formed in the middle of the sheet conveying path so as to correspond to curls on both front and rear sides, and a pair of conveying rollers are arranged on the pair of curl correcting paths. 2. The sheet conveying apparatus according to claim 1, wherein the pair of curl correcting paths are formed so as to branch off from the middle of the sheet conveying path into two branches and then join at a downstream side. 3. The conveying roller of the pair of conveying rollers, the conveying roller disposed outside the curl correction path is formed of a soft material, and the conveying roller disposed inside the curl correction path is formed of a hard material. The sheet conveying device according to claim 1, wherein: 4. A transfer device for transferring a toner image on a photoreceptor to a sheet sent from a sheet supply means,
An image forming apparatus comprising: a fixing device that fixes toner on a sheet after passing through the transfer device; and the sheet conveying device according to claim 1.