JPH0912201A - Image forming device - Google Patents

Abstract

PURPOSE: To send the sheet refed form an intermediate tray and the sheet supplied from paper feed deck to an image formation part in condition that they are not given upward curls. CONSTITUTION: A carry path 29, which carries the sheet fed from a paper feed deck 2, is joined to the middle of the carry path 22 of a carrier 31 which carries the sheet refed from on an intermediate tray 11 to an image formation part 9. One of the plural pairs of carry rollers 33-36, which carry the sheets passing a carry path 32, is arranged right downstream of the junction of this carry path 29. This carry roller 35 is arranged so that the line connecting the center of each roller and that of the next may be orthogonal to the line in the direction of the carriage. Therefore, the refed sheet being sent from upstream side of the carry path 32 gets in the nip of the pair 35 of carry rollers, changing the direction of its carriage, and an unused sheet being sent from the carry path 29 gets in the nip of the pair 35 of rollers, without changing the direction of its carriage.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile or the like, a sheet on which an image has been formed is temporarily transferred in order to feed a sheet for double-sided image formation or multiple image formation to an image forming section again. In some cases, a re-feeding stacking means (intermediate tray) for loading is provided in the image forming apparatus main body.

Some image forming apparatuses such as copiers, printers, and facsimiles are provided with a paper feed deck capable of accommodating a large number of sheets so that a large amount of sheets can be consumed.

FIG. 5 shows the overall construction of a conventional typical image forming apparatus (copying machine) provided with both a re-feeding stacking means and a paper feed deck.

In this image forming apparatus, two sheet feeding decks 2 and 3 and two sheet feeding cassettes 4 and 5 are provided in the image forming apparatus main body 1 as sheet feeding sections. In this image forming apparatus, when one of the paper feed units 2, 3, 4, 5 is selected, a sheet of a desired size is fed from the selected paper feed unit.

Sheets having a large consumption amount such as A4 size and letter size are stacked on the paper feed decks 2 and 3. Further, sheets of a small consumption amount such as A3 size are stacked in the sheet feeding cassettes 4 and 5. The paper feed cassettes 4 and 5 are universal cassettes on which sheets of various sizes can be stacked.

The paper feed decks 2 and 3 are arranged side by side in the horizontal direction in a substantially central portion of the main body 1 of the image forming apparatus, and the paper feed cassettes 4 and 5 are vertically arranged in the lower portion of the main body 1 of the image forming apparatus. They are arranged side by side.

An optical system 8 for reading information of a document (not shown) set at a predetermined position on the platen glass 7 by an automatic document feeder 6 is provided at the top of the image forming apparatus main body 1.
Is provided, and the image forming unit 9 and the fixing unit 10 are provided below the
Etc. are arranged, and the intermediate tray 11 etc. is arranged on the lower side thereof.

The information (image light) read by the optical system 8 is projected onto the photosensitive drum 12 rotating clockwise in the drawing. As a result, the photosensitive drum 12
An electrostatic latent image of information is formed on the upper surface, and the electrostatic latent image is visualized (toner image) by the toner supplied from the developing device 13, and the electrostatic latent image between the photosensitive drum 12 and the transfer charging device 14 is formed. It is transported to the transfer unit.

Sheets (not shown) stacked and housed in the paper feed cassette 5 are fed in order from the uppermost sheet by a paper feed roller 15 which rotates counterclockwise in the figure. Then, the fed-out sheet is separated into the uppermost sheet by the separation roller pair 16 and is sent to the registration roller pair 28 in the rotation stopped state by the conveyance roller pairs 23 to 27.

Sheets (not shown) stacked and stored in the paper feed cassette 4 are fed out in order from the uppermost sheet by a paper feed roller 17 which rotates counterclockwise in the figure. Then, the fed-out sheet is separated into the uppermost sheet by the separation roller pair 18 and is sent to the registration roller pair 28 in the rotation stopped state by the conveyance roller pairs 24-27.

The sheets (not shown) stacked on the sheet feeding deck 2 are sequentially fed out from the uppermost sheet by a sheet feeding roller 19 rotating counterclockwise in the figure. Then, the fed-out sheet is separated into the uppermost sheet by the separation roller pair 20, and is sent to the registration roller pair 28 in the rotation stopped state by the conveyance roller pairs 35, 36 and 26, 27.

In this case, the separated sheets enter the conveying path (second conveying path) 29 into the conveying path (first conveying path) 32, then enter the conveying path 32 into the conveying path 37, and It enters the conveyance path 38 from the conveyance path 37 and reaches the registration roller pair 28. The transport path 32
Is a path formed in the conveyance device 31 that conveys the sheet re-fed from the intermediate tray 11 to the image forming unit 9.

Sheets (not shown) stacked on the paper feed deck 3 are fed in order from the uppermost sheet by a paper feed roller 21 rotating counterclockwise in the figure. Then, the uppermost sheet of the fed-out sheet is separated into one sheet by the separation roller pair 22, and is conveyed to the registration roller pair 28 in the rotation stopped state by the conveyance roller pairs 26 and 27.

In this case, the separated sheet enters the conveyance path 38 from the conveyance path 30 and the pair of registration rollers 28.
To reach.

The sheet fed from any one of the sheet feeding portions and reaching the registration roller pair 28 stops moving when the leading edge of the sheet hits the nip of the registration roller pair 28 to form a predetermined amount of loop. The formation of this loop corrects the skewed state of the sheet.

The sheet of which the skewed state is corrected is rotated by the registration roller pair 28 which starts rotation at the timing of aligning the position of the toner image on the photosensitive drum 12 with the position of the leading edge of the sheet.
Is sent to the transfer section.

On the sheet surface of the sheet sent to the transfer section,
The toner images on the photosensitive drum 12 rotating in the clockwise direction are sequentially transferred by the transfer charger 14. Then, the sheet on which the toner image has been transferred is sent to the fixing unit 10 by the conveyor belt 39, and is heated and pressed while passing through the nip of the fixing roller pair 40 to fix the transferred toner image on the sheet surface.

In the normal mode, the sheet passing through the fixing roller pair 40 passes through the sheet discharging path 41 and the sheet discharging roller pair 42.
The sheet is discharged onto the sheet discharge tray 43 outside the machine. In this case, the flapper 44 opens the paper discharge path 41.

In the double-sided mode, the sheet passing through the fixing roller pair 40 passes through the double-sided path 45 and the discharging roller pair 46.
The sheet is discharged onto the intermediate tray 11 with the image forming surface facing downward. In this case, the flapper 44 opens the double-sided path 45.

The sheets stacked on the intermediate tray 11 are
In the figure, the sheet is fed in order from the lowest sheet by a half-moon-shaped sheet feeding roller 47 that rotates counterclockwise.
Then, the lowermost sheet of the fed-out sheets is separated into one sheet by the separating device 48, and is sent to the conveying path 32 of the conveying device 31 by the conveying roller pair 49.

The sheet sent to the carrying path 32 is sent to the carrying path 38 by the carrying roller pairs 33 to 36, and is sent to the registration roller pair 28 in the rotation stopped state by the carrying roller pairs 26 and 27.

The toner image is transferred onto the second surface of the sheet sent to the registration roller pair 28 while passing through the transfer portion in the same manner as described above, and the transfer toner image is fixed while passing through the fixing roller pair 40. After that, the sheet passes through the sheet discharge path 41 and is discharged onto the sheet discharge tray 43 outside the machine by the sheet discharge roller pair 42.

In this image forming apparatus, the intermediate tray 1
Since the image forming apparatus main body 1 is provided with 1 and the paper feed decks 2 and 3, it is considered that the image forming apparatus main body 1 does not become large in the height direction. For example, one of them is to arrange the two paper feed decks 2 and 3 in the horizontal direction so that the transport path 29 of one of the paper feed decks 2 merges with the transport path 32 of the transport device 31. One of them is to reduce the curvature of the curved portion (A, B, etc.) of the path.

Further, in this image forming apparatus, a curl straightening roller pair 50 using a metal roller and a sponge roller is provided in the double-sided path 45 so that the curled sheet is not fed to the intermediate tray 11. Curls are corrected with a nip of 50. Sheet is fixing roller pair 40
Since it is heated and pressurized while passing through, it is easy to be curled.

[0026]

However, in the image forming apparatus of the above-mentioned conventional example, the sheet re-fed from the intermediate tray 11 to the image forming section 9 is often curled, and thus the image forming is performed. Part 9 causes various problems. The sheet re-fed from the intermediate tray 11 is likely to be curled while passing through the curved portion B having a small curvature.

For example, as shown in FIG. 6, when a sheet S having an upward curl is sent to the image forming section 9, (1) it is electrostatically attracted to the photosensitive drum 12 by the separation charger 51. Even if an attempt is made to separate the existing sheet S, it becomes difficult to separate the sheet S. (2) The leading edge of the sheet hits the cleaner 52 and damages parts such as the photosensitive drum 12.
(3) The toner image cannot be satisfactorily transferred from the photosensitive drum 12 to the sheet S, and the image is disturbed. Such problems are likely to occur.

Further, in the image forming apparatus of the above-mentioned conventional example, the sheet fed from the paper feed deck 2 enters the nip of the conveying roller pair 35 at a predetermined angle, so that the curl is generated while passing through the conveying roller pair 35. Easy to attach.

Therefore, the present invention has been made in view of the above circumstances, and the sheet re-fed from the re-feeding stacking unit to the image forming unit is passing through a curved portion having a small curvature. An image forming apparatus capable of removing the curl attached to the image forming section and sending it to the image forming section, and sending an unused sheet fed from the sheet feeding section to the image forming section without curling The purpose is to provide.

[0030]

SUMMARY OF THE INVENTION According to the present invention, a sheet fed from a sheet feeding unit is conveyed in the middle of a first conveying path for conveying a sheet re-fed from a re-feeding stacking unit. The present invention relates to an image forming apparatus in which the second transport path is joined.

In the present invention, in order to achieve the above object, the sheet sent from the upstream side of the first conveying path is changed in the conveying direction upward and enters the nip, and is fed from the second conveying path. It is characterized in that a pair of conveying rollers, which is adapted to enter the nip without changing the conveying direction of the sheet to be received, is installed immediately downstream of the confluence point of the second conveying path.

[0032]

According to the image forming apparatus of the present invention having the above-mentioned structure, the re-feeding device is re-fed from the re-feeding stacking means.
The sheet moving on the conveyance path is bent upward while passing the conveyance roller pair. Therefore, the downward curl applied during the passage through the curved portion having a small curvature upstream of the first transport path is corrected.

Further, the sheet fed from the sheet feeding section and moving on the second transport path enters the nip of the pair of transport rollers without changing the transport direction. Therefore, the sheet fed from the sheet feeding unit is not curled while passing through the pair of conveying rollers.

[0034]

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

FIG. 1 shows the overall structure of an image forming apparatus (copier) to which the present invention is applied. FIG. 2 shows a detailed configuration of a carrying device which is an invention part in the image forming apparatus.

In describing the structure of the present image forming apparatus, the same members as those of the image forming apparatus of the above-mentioned conventional example (FIG. 5) are designated by the same reference numerals, and those which are structurally and functionally unchanged. Will not be described.

In this image forming apparatus, the image forming section 9
Make sure the sheet sent to is not curled upward as shown in Figure 6. Therefore, in the present image forming apparatus, a downward curl (in the image forming portion 9) attached until the sheet re-fed from the intermediate tray 11 is conveyed to the conveyance path 32 of the conveyance device 31. The upward curl) is corrected by utilizing the pair of transport rollers 35 in the transport path 32.

The conveying roller pair 35 is installed immediately downstream of the junction point X of the conveying path 29. This conveying roller pair 35
Is installed such that the line O1 connecting the centers of the rollers 35A and 35B is orthogonal (θ1) to the line O2 in the sheet transport direction of the transport path 29. In this case, the line O3 in the sheet transport direction of the transport path 32 and the line O2 in the sheet transport direction of the transport path 29 intersect at an angle θ2, and thus the line O3.
The angle formed by 1 and the line O3 is θ3. Here, θ3 is set to around 60 °.

When the conveying roller pair 35 is installed as described above, the sheet sent from the upstream side of the conveying path 32 enters the nip by changing the conveying direction upward. Therefore, the downward curl applied until the sheet re-fed from the intermediate tray 11 is sent to the transport path 32 is
The sheet is straightened while passing through the pair of transport rollers 35. The sheet sent from the transport path 29 enters the nip without changing the transport direction. Therefore, even if an unused sheet fed from the paper feed deck 2 passes through the pair of transport rollers 35, no curl is attached.

At the merging point X, as shown in FIG. 3, the sheet fed from the upstream of the transport path 32 is transported by the transport roller pair 35.
Sheet guide member 53 that guides to the nip of
A sheet guide member 54 that guides the sheet sent from the sheet to the nip of the pair of transport rollers 35 is installed. The sheet guide members 53 and 54 include polyethylene (PE
Synthetic resin sheets such as T) and polycarbonate (PC) are used. Further, the tip (free end) of the sheet guide member 53 is located slightly downstream of the tip (free end) of the sheet guide member 54.

FIG. 4 shows a state in which the sheet S sent from the upstream side of the conveying path 32 passes through the conveying roller pair 35 while being bent. In this case, the sheet guide member 53 that guides the sheet S helps the sheet S to flex smoothly while being flexibly deformed, and prevents the sheet S from being excessively bent and bent. Further, at this time, even if the sheet guide member 53 is flexibly deformed, the tip of the sheet guide member 54 does not project above the sheet guide member 53, and the sheet guide member 54 does not hinder the bending of S.

The function of helping the sheet S to bend smoothly can be performed only by the sheet guide member 53.

[0043]

As described above, in the image forming apparatus of the present invention, the sheet fed from the upstream of the first conveying path enters the nip by changing the conveying direction upward, and the sheet is conveyed to the second conveying path. Since the sheet fed from the sheet is installed in the nip without changing the conveying direction, it is installed immediately downstream of the confluence point of the second conveying path. The downward curl applied until the fed sheet is fed to the first transport path is corrected while passing through the pair of transport rollers. Further, the unused sheet fed from the sheet feeding unit passes through the pair of conveying rollers and is fed to the first conveying path without being curled. Therefore, it is possible to feed the sheet without the upward curl to the image forming unit.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional side view showing an overall configuration of an image forming apparatus (copier) to which the present invention is applied.

FIG. 2 is a vertical cross-sectional side view showing a detailed configuration of a conveyance device which is an invention portion of the image forming apparatus.

FIG. 3 is a vertical cross-sectional side view showing a configuration of a merging portion of the transport device.

FIG. 4 is a vertical cross-sectional side view illustrating the operation of the sheet guide member.

FIG. 5 is a vertical cross-sectional side view showing the overall configuration of a conventional image forming apparatus (copying machine).

FIG. 6 is a vertical cross-sectional side view illustrating a problem in the image forming unit.

[Explanation of symbols]

 2 paper feeding deck (paper feeding section) 11 intermediate tray (refeeding stacking means) 29 transportation path (second transportation path) 32 transportation path (first transportation path) 35 transportation roller pair 35A, 35B transportation roller pair Rollers 53, 54 Sheet guide member O1 Line connecting the centers of the rollers of the conveying roller pair O2 Line in the conveying direction of the second conveying path X Confluence point S Sheet

Claims (7)

[Claims] 1. A second transport path for transporting a sheet fed from a sheet feeding unit joins a first transport path for transporting a sheet re-fed from a re-feed stacking unit. In the image forming apparatus, the sheet sent from the upstream side of the first conveying path changes the conveying direction upward and enters the nip, and the sheet sent from the second conveying path changes the conveying direction. An image forming apparatus characterized in that a pair of conveying rollers adapted to enter the nip without any change is installed immediately downstream of a confluence point of the second conveying path. 2. The image according to claim 1, wherein the first transport path is a path for transporting the sheet substantially horizontally, and the second transport path is a path for transporting the sheet while inclining the sheet. Forming equipment. 3. The conveyance roller pair is installed such that a line connecting the centers of the rollers is substantially orthogonal to a line in the sheet conveyance direction of the second conveyance path. Image forming device. 4. The first sheet made of a synthetic resin sheet, which guides the sheet re-fed from the re-feeding stacking means to the nip of the pair of conveyance rollers, at the confluence of the second conveyance path. The image forming apparatus according to claim 1, wherein a guide member is installed. 5. A second sheet guide member made of a synthetic resin sheet for guiding the sheet fed from the sheet feeding section to a nip of the pair of conveying rollers is installed at a confluence point of the second conveying path. The image forming apparatus according to claim 4, wherein the image forming apparatus comprises: 6. The image forming apparatus according to claim 5, wherein the leading end of the first sheet guide member is located slightly downstream of the leading end of the second sheet guide member. 7. The image forming apparatus according to claim 1, wherein the paper feed unit is a paper feed deck on which a large number of sheets are stacked.