JPH0725508A - Sheet carrying device and image forming device - Google Patents

Abstract

PURPOSE:To provide a sheet carrying device and an image forming device in which the curl of a sheet is corrected without damaging the sheet to surely carry the sheet by setting at least one of a plurality of first rollers to have a different diameter from the other, and setting each of a plurality of second rollers to have a diameter making contact with each of the first rollers. CONSTITUTION:A carrying lower driving roller 25b is formed with an outer diameter larger than that of a carrying lower driven roller 24b. The outer diameters of carrying upper rollers 24a, 25a are determined in such a manner that these rollers can be pressed onto the corresponding carrying lower rollers 24b, 25b, respectively. A sheet P fed into a carrying part is carried by the carrying force by the roller pair 25a, 25b, and the driven roller pair 24a, 24b are rotated according to the carrying of the sheet. The sheet is carried in the state where the whole sheet is curved to the carrying direction of the sheet, and never damaged even in case of sheet form. Therefore, the curl of the top end causing a jam when the sheet is housed in a middle tray is prevented, and the sheet is surely carried.

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 used in an image forming apparatus such as a copying machine and a laser beam printer, and an image forming apparatus therefor.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus, when performing multiplex copying or double-sided copying, a sheet once copied is held in an intermediate tray in the apparatus and is re-fed to obtain the same sheet surface or back surface. It is designed to form images on multiple copies or double-sided copies.

That is, as shown in FIG. 6, in the image forming apparatus, cassette containers 102 and 103 containing a plurality of sheets of different sizes are detachably mounted in a sheet feeding section 101. 1 out of 102, 103
Sheets are fed from the bottom. Then, the toner image is transferred from the photosensitive drum 105 to the sheet at the transfer unit 104, and the toner image is fixed at the fixing unit 106.
In the case of copying on one side only, the flapper 107 rotates in the direction of arrow a in the figure, and the sheet is carried out of the apparatus. However, in the case of multiple copying and double-sided copying, the flapper 107 is at the position shown in the figure. The sheet is conveyed downward.

In the case of multiple copy, the second flapper 108 rotates in the direction of arrow B in the figure, the sheet is conveyed onto the intermediate tray 110 via the conveying path 109, and the leading end of the sheet is re-fed roller 111. And is held in contact with the separation roller 112. On the other hand, in the case of double-sided copying, the second flapper 108 is at the position shown in the figure, and the sheet is in the transport path 1.
13 is conveyed back to the pair of rollers 114, is conveyed back to the intermediate tray 110 via the conveyance path 109, and is similarly held.

Further, the sheets on the intermediate tray 110 are re-fed one by one by the re-feeding roller 111 and the separating roller 112, transferred and fixed in the same manner as described above, and carried out of the apparatus to perform multiplex copying or double-sided copying. It is supposed to be completed.

When the sheets are stacked on the intermediate tray 110, the flapper 120 is switched according to the size of the sheets to change the position of the entrance of the intermediate tray 110.

By the way, since the sheet sent to the conveying path 109 is subjected to heat and pressure by the fixing unit 106,
Often curled. And the sheet curl is
It causes various obstacles in sheet conveyance. In particular, when a sheet with its leading edge curled upward is stored in the intermediate tray 110, a storage failure occurs as shown in FIG.

In order to prevent this, the pair of transport rollers 121, 1
22 and 123 are configured as shown in FIG. 5 (note that since the transport roller pairs 121, 122, 123 have the same shape, the transport roller pair 121 is shown here as a representative, and the transport roller pair 121 is shown as a representative. Explained.).

That is, the roller 130 of the lower conveyance roller 121b has a brim-shaped portion 130 having a large diameter at both ends thereof.
The roller 131 of the upper conveying roller 121a is arranged so as to hold the sheet a and press the sheet P against the flange portion 130a.

With this structure, the sheet P has ridges and valleys formed in the same direction as the conveying direction, so that the sheet P can be stored in the intermediate tray 110 while curling the leading edge of the sheet.

[0011]

However, in the above-mentioned conventional example, since the sheet is locally deflected between the rollers 130 and 131, the sheet may be damaged.

In particular, this is remarkable for thin and fragile sheets. The diameter of the brim portion 130a of the lower conveyance roller 121b (122b, 123b) is reduced so that the deflection is suitable for such a sheet, and the upper conveyance roller 1 is used.
If the pressing force of 21a (122a, 123a) is reduced, it is impossible to prevent the usual curling on the leading edge of the sheet.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a sheet conveying device and a sheet conveying device for correcting the curl and certainly conveying the sheet without damaging the sheet. Another object is to provide an image forming apparatus.

[0014]

In order to achieve the above object, the present invention provides at least one sheet conveying roller pair for conveying an image-formed sheet in the sheet conveying direction. Is composed of a first sheet conveying roller and a second sheet conveying roller which are arranged to face each other in contact with each other, and the first sheet conveying roller has the same rotation center in a direction orthogonal to the sheet conveying direction. The plurality of first rollers are arranged, and the second sheet conveying roller is arranged so as to face the plurality of first rollers at the same rotation center in a direction orthogonal to the sheet conveying direction. A plurality of second rollers that are
In the sheet conveying device, at least one of the plurality of first rollers has a different diameter from the other, and each of the plurality of second rollers has a diameter of being in contact with each of the plurality of first rollers. It is characterized by being.

It is preferable that the plurality of first rollers include a first driving roller and a first driven roller, and the plurality of second rollers include a second driven roller.

Further, a sheet guide member is provided on the downstream side of the pair of sheet conveying rollers, and the height of the guide member in the direction orthogonal to the sheet conveying direction is the same as that of the plurality of first rollers and the plurality of second rollers. It is desirable to set in correspondence with the height of each contact position.

Further, it is characterized by comprising the sheet conveying device and an image forming means for forming an image and feeding the sheet to the sheet conveying device.

[0018]

In the present invention having the above structure, at least one of the plurality of first rollers has a diameter different from the other diameters, and each of the plurality of second rollers is attached to each of the plurality of first rollers. By making the diameter in contact with each other, unlike the conventional case in which the sheet is locally deflected by one first roller and one second roller that faces the first roller, the plurality of first rollers face each other. Since it is bent as a whole by the plurality of second rollers, even in the case of a thin sheet, the curl can be corrected and the sheet can be reliably conveyed without being damaged.

When the plurality of first rollers are composed of the first driving roller and the first driven roller, and the plurality of second rollers are composed of the second driven roller, all the second rollers are composed of the driven rollers. Even if at least one of the first rollers has a diameter different from that of the other rollers, the difference in rotation speed due to the difference in diameter is accommodated by the driven second roller, so that no inconvenience occurs.

Further, a sheet guide member is provided on the downstream side of the pair of sheet conveying rollers, and the height of the guide member in the direction orthogonal to the sheet conveying direction is set so that the plurality of first rollers and the plurality of second rollers contact each other. By setting in correspondence with the height of the position, the sheet curved by the pair of sheet conveying rollers is guided by the guide member in the curved state.

[0021]

An embodiment of the present invention will be described below with reference to the drawings.

First, before describing the sheet conveying apparatus which is a characteristic part of the present invention, an outline of an image forming apparatus to which the sheet conveying apparatus is applied will be described with reference to FIG.

In the image forming apparatus, cassettes 2 and 3 containing a plurality of sheets of different size sheets are detachably mounted in a sheet feeding section 1. Of these cassettes 2 and 3, one is Paper is fed from one side. And
The toner image is transferred from the photosensitive drum 5 to the sheet at the transfer unit 4, and the toner image is fixed at the fixing unit 6. In the case of copying on one side only, the flapper 7 rotates in the direction of arrow A in the figure, and the paper is carried out of the apparatus. However, in the case of multiple copying and double-sided copying, this flapper 7 is at the position shown in the figure. The paper is conveyed downward.

In the case of multiple copy, the second flapper 8 rotates in the direction of arrow B in the figure, and the sheet is conveyed in the conveying path 9.
After that, the sheet is conveyed onto the intermediate tray 10 and the leading end thereof is held in contact with the re-feeding roller 11 and the separation roller 12.
On the other hand, in the case of double-sided copying, the second flapper 8 is at the position shown in the figure, the sheet is conveyed to the conveyance path 13 and is fed back by the pair of rollers 14, and the intermediate tray 10 is conveyed via the conveyance path 9.
It is transported to the top and held in the same manner.

Further, the sheets on the intermediate tray 10 are re-fed one by one by the re-feed roller 11 and the separation roller 12, transferred and fixed in the same manner as described above, and carried out of the apparatus.
Multiple copy or double-sided copy is completed.

When stacking sheets on the intermediate tray 10,
The flapper 20a, 20b is switched according to the size of the sheet to change the position of the entrance of the intermediate tray 10.

FIG. 1 is a schematic view of a sheet conveying apparatus according to this embodiment. The conveyance lower drive roller 25b as the first drive roller rotates integrally with the drive shaft 26. A pulley 31 is provided at one end of the drive shaft 26, and this pulley is connected to a pulley 34 via a belt 32. The pulley 34 rotates integrally with the drive shaft 37, and
Since the pulley 35 also rotates integrally, the drive shaft 26,
37 and 38 rotate at the same speed in the same rotation direction.

Since the transport lower driven roller 24b as the first driven roller is configured to be rotatable with respect to the drive shaft 26 at a sliding portion (hatched portion in the drawing), the rotational direction and the rotational speed of the drive shaft 26 can be controlled. Can rotate independently. The conveyance lower drive roller 25b has a larger outer diameter than the conveyance lower driven roller 24b.

The upper conveying rollers 24a and 25a as the second driven rollers (second rollers) are freely rotatable in a sliding portion (hatched portion in the figure) with respect to a shaft 27 fixed to a frame (not shown). It is possible. The outer diameters of the upper conveying rollers 24a and 25a are determined so that they can be pressed against the lower conveying rollers 24b and 25b which face each other.

By adopting such a roller structure, the paper P sent to the transport section is transported by the transport force of the roller pair 25a, 25b, and the driven roller pair 24a, 24b.
Rotates following the conveyance of the paper. At that time, as shown in FIG. 2, the sheet is conveyed in a state where the entire sheet is curved with respect to the sheet conveying direction. Therefore, when the paper is stored in the intermediate tray 10, curling of the leading end that causes a paper jam is prevented.

At this time, the sheet conveying speed is 25 for the roller pair.
a, 25b, the driven lower roller 24 under conveyance
Since b is rotatable with respect to the drive shaft 26, no inconvenience occurs.

The height of the flappers 29, 30 that are cut according to the size of the paper in the direction orthogonal to the sheet conveying direction is determined by the plurality of rollers 24b, 25b and the roller 24.
It is set corresponding to the height of each contact position with a and 25a.

Therefore, even when the advancing direction of the sheet is switched by the flappers 129 and 130, it is possible to store the sheet in the intermediate tray 10 while keeping the curved state of the sheet.

Here, the transport lower drive roller 25b and the transport lower driven roller 24b constitute the first roller 15, and the first roller 15 and the drive shaft 26 constitute the first sheet transport roller 21b (or 22b, 23b). Is configured,
The upper transport rollers 24a and 25a and the shaft 27 constitute a second sheet transport roller 21a (or 22a and 23a).

Further, the shaft 28 and the flapper 29 constitute a guide member 20a (or 20b).

The invention is not limited to the embodiments described above. The embodiment is an example relating to a so-called center reference in which the conveyance standard of the sheet is the center of the sheet, but the same effect can be obtained when this is used as a so-called one-side reference with one side of the sheet as the reference. An example in that case is shown in FIG. In the figure, the diameter of the lower conveyance driving roller 40b as the first driving roller, which is closer to the reference side of the conveyance, is configured to be larger than that of the lower transportation driven roller 41b as the first driven roller, so that the entire sheet is curved. ing.

In addition to this, it is also possible to make the conveyance lower drive roller smaller than the diameter of the conveyance lower driven roller, and the arrangement position and arrangement order in the axial direction can be freely configured.

The transport lower drive roller 40b and the transport lower driven roller 41b constitute the first roller 15, and the first roller 15 and the drive shaft 26 constitute the first sheet transport roller 21b (or 22b, 23b). The upper sheet conveying rollers 40a, 41a and the shaft 27 constitute a second sheet conveying roller 21a (or 22a, 23a).

[0039]

As described above, according to the present invention,
At least one of the plurality of first rollers has a different diameter from the other, and each of the plurality of second rollers has a diameter that abuts on each of the plurality of first rollers, so that the first roller has The sheet is locally deflected by two first rollers and one second roller opposite to the first roller, and the sheet is entirely deflected by the plurality of first rollers and the plurality of second rollers facing each other. Therefore, even in the case of a thin sheet, the curl can be corrected and reliably conveyed without damaging the sheet.

When the plurality of first rollers are composed of the first driving roller and the first driven roller and the plurality of second rollers are composed of the second driven roller, the plurality of second rollers are composed of the driven rollers. Even if at least one of the first rollers has a diameter different from that of the other rollers, the difference in rotation speed due to the difference in diameter is accommodated by the driven second roller, so that no inconvenience occurs.

Further, a sheet guide member is provided on the downstream side of the pair of sheet conveying rollers, and the height of the guide member in the direction orthogonal to the sheet conveying direction is set so that the plurality of first rollers and the plurality of second rollers contact each other. By setting in correspondence with the height of the position, the sheet curved by the pair of sheet conveying rollers is guided by the guide member in the curved state.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a sheet conveying device according to an embodiment of the present invention.

FIG. 2 is a front view of the main part of the apparatus.

FIG. 3 is a front view of a main portion of a sheet conveying device according to another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 5 is a plan view of a main part of a conventional sheet conveying device.

FIG. 6 is a schematic configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

21b, 22b, 23b 1st sheet conveying roller 21a, 22a, 23a 2nd sheet conveying roller 15 1st roller 25b, 40b Lower conveying driving roller (first driving roller) 24b, 41b Lower conveying driven roller (first driven roller) 24a, 25a, 40a, 41a Transport upper roller (second driven roller (second roller)) 20a, 20b Guide member

Claims (4)

[Claims] 1. A sheet conveying roller pair for conveying an image-formed sheet is provided at least in the sheet conveying direction, and the sheet conveying roller pair and a first sheet conveying roller are arranged so as to face each other. The first sheet transport roller comprises a second sheet transport roller, and the first sheet transport roller is provided with a plurality of first sheet transport rollers arranged at the same rotation center in a direction orthogonal to the sheet transport direction.
The second sheet conveying roller comprises a plurality of second rollers arranged to face the plurality of first rollers with the same center of rotation in a direction orthogonal to the sheet conveying direction. A sheet transporting device, comprising: at least one of the plurality of first rollers having a different diameter from the other, and each of the plurality of second rollers, each of the plurality of first rollers. A sheet conveying device having a diameter that abuts against a sheet. 2. The sheet conveying apparatus according to claim 1, wherein the plurality of first rollers include a first driving roller and a first driven roller, and the plurality of second rollers include a second driven roller. 3. A sheet guide member is provided on the downstream side of the pair of sheet conveying rollers, and the height of the guide member in the direction orthogonal to the sheet conveying direction is set to be the same as that of the plurality of first rollers and the plurality of second rollers. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is set corresponding to the height of each contact position. 4. An image forming apparatus, comprising: the sheet conveying apparatus according to claim 1; and an image forming unit that forms an image and feeds the sheet to the sheet conveying apparatus.