JP3294516B2 - Paper feeder for duplex image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeder for storing and feeding out a sheet on which a single-sided image has been formed in a double-sided image forming apparatus.

[0002]

2. Description of the Related Art It is well known that a double-sided copy is obtained by a copying method such as electrophotography. This involves forming an electrostatic latent image on a photoconductor, developing the toner image, transferring the toner image to a transfer sheet, fixing the image, storing the sheet on which the image has been formed on the first surface in an intermediate tray, and re-transferring the image onto the photoconductor. An image is formed on both surfaces of a sheet by forming an electrostatic latent image, developing the toner image, and transferring and fixing the toner image to the second surface.

In an automatic double-sided copying machine, when forming an image on both sides as described above, the required number of sheets on which an image has been formed on the first side are stored in an intermediate tray, and then the image on the second side is transferred to the intermediate tray. By forming on the photoreceptor, feeding the sheets of the intermediate tray one by one and transferring the image to the second surface,
2. Description of the Related Art A method for forming an image on each side of a large number of units is known. This is called a multi-copy method.

[0004] If necessary, only one image is formed on the first side, the image is stored in the intermediate tray, and then the sheet on which the image has been formed is immediately re-fed on one side, and the image is formed on the second side. Form. A method is also known in which this is repeated to obtain a large number of double-sided copies. This is called a sequential copying method.

In the automatic double-sided image forming apparatus using the multi-copying method, for example, as described in Japanese Patent Application Laid-Open No. 57-72537, a double-sided paper receiver 1
In this case , a large number of sheets are stored in the sheet 8 and the sheets are pressed and stored one by one from the upper surface of the storing surface so as to stably feed the sheets having curled sheets.

In Japanese Patent Application Laid-Open No. 61-140425, the curl at the rear end of the paper entering the tray of the double-sided copy tray device is controlled by the rear end, and the curl at the front end is curled at the front end. By alternately holding each sheet with a presser, the curl of each sheet is corrected, and the succeeding sheet collides with the sheet in the tray to prevent a paper jam.

However, in such a conventional technique, when a sheet is reversed and stored in an intermediate tray in order to copy an image on the second side of the sheet, the sheet reversing mechanism intersects with the transport direction of the sheet transfer section. Since the paper was conveyed in the direction in which the paper was moved, the size of the apparatus was increased.

More specifically, the sheet on which the copy has been made is subjected to a heating action or a pressure action by a fixing device (11) and a reversing section (101) provided at a downstream portion in the conveying direction, and the sheet tends to curl. When such a sheet is stored in the double-sided tray unit (12), the sheet curls or curls into a cylindrical shape due to the effect of the curl, causing a storage failure. It is a conventional example that it cannot be performed accurately.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and inverts a sheet to copy an image on the second side of the sheet by a small apparatus. The paper is stored in the intermediate tray.
The purpose is to make them fully aligned .

[0010]

According to the present invention, there are provided an intermediate tray, a paper feed path to the intermediate tray, a discharge path from the intermediate tray, and a feed path from the process section to the intermediate tray. and a conveying rollers, the entering-conveying path and the discharge conveyance path is arranged so as to intersect the one end of the intermediate tray, the straightening curled portion provided between the conveying roller and the processing unit, is carried To align the loaded paper
The paper feed end is moved by a predetermined length from the initial length in the paper conveyance direction in the paper re-feed direction by the rear end plate to regulate the paper at the time of paper input or paper re-feed. It is characterized by the following.

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

According to the paper feeder of the double-sided image forming apparatus of the present invention, the double-sided tray unit 12 is provided with the rear end plate 20 for aligning the loaded paper.
Before the paper is carried in, the rear end plate 20 is located away from the paper carrying direction, and after the paper is carried in, moves from the paper leading end regulating position to a position corresponding to the paper length in the carrying direction.
Thus, the stacking positions of the sheets stacked in the duplex tray unit 12 are aligned.

However, if the paper conveyed into the double-sided tray unit 12 is curled, when the paper is conveyed from the paper leading end regulating position to a position corresponding to the paper length in the conveying direction after the paper is conveyed as described above, the curl is substantially reduced. Specifically, the paper is shorter than the length of the paper in the transport direction, and the paper placement positions are not sufficiently aligned (see FIG. 7).

In order to solve this problem, a dimension in which the length in the transport direction is shortened due to paper curl is measured in advance, and
The rear end plate 20 is set so as to move from the position corresponding to the sheet length in the transport direction to the position shifted in the re-feeding direction by the shortened amount (see FIG. 8). This makes it possible to sufficiently align the placement positions of the sheets.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A paper feeder of a two-sided image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a two-sided copying machine according to an embodiment of the present invention.

As shown in FIG. 1, a first document is placed on a document table glass 1 and an electrostatic latent image corresponding to the first document is formed on a photosensitive drum 2. The electrostatic latent image is developed by the developing device 3 to form a toner image. On the other hand, the transfer paper 4 is transported from the paper tray 5 through the cassette
The transport direction is corrected by the rollers 8. Thereafter, conveyance is started, and the toner image contacts the toner image in synchronization with the rotation of the photosensitive drum 2. Next, the toner image is transferred to the transfer paper by the transfer charger 9, the paper is sucked and conveyed by the suction belt 10, sent to the fixing device 11, and the toner image is fixed.
The required number of transfer sheets 4 on which the formation of the one-sided image has been completed is deposited in the double-sided tray unit 12.

Each time the transfer sheet 4 is carried into the duplex tray unit 12, the rear end plate 20 moves in the transport direction. Immediately before the transfer paper 4 is carried into the double-sided tray unit 12, the rear end plate 20 is located at the middle position B in FIG. The plate 20 moves to the position A. As a result, the edges of the deposited transfer paper 4 are aligned.

Next, in order to form an image on the back surface, a second document is placed on a platen glass and a toner image is formed on a photosensitive drum in the same manner as described above.

The transfer paper for the second side is fed from the double-sided tray unit 12. The transfer paper 4 is pressed against the feed roller 23 in the double-sided tray unit by the sheet pressing plate 19, discharged one by one from the double-sided tray unit 12 by the feed roller 23, and passed through the re-feeding path 26.
The image formed on the surface of the photosensitive drum 2 is transferred again, passes through the fixing device 11, and is discharged to the discharge tray 6.

(Embodiment 1) A characteristic operation of the present invention will be described below with reference to FIG.

The sheet heated by the fixing rollers 11a and 11b is provided downstream of the fixing device 11 in the transport direction.
Decara rollers 16a and 16b which are curl removing rollers
(De-curler), the image-formed surface curls in a convex direction.

Therefore, the transport speed of the decolor rollers 16a and 16b is set to V0 (constant), and the paper 4A of the paper size A (length in the transport direction: L1) is transported to the decolor rollers 16a and 16b and the input / output roller device 17a of the duplex tray unit 12. ,
17c, the conveying speed of the input / output roller devices 17a and 17c of the double-sided tray unit is set to V1 <V0.
By transporting at a speed V1 which is
A curl in a direction opposite to the curl direction of the reversing portion 101 (image forming surface is concave) can be generated in the sheet bending portion 100 in the transport path between the sheet feeding rollers 6a and 16b and the paper input / output roller devices 17a and 17c ( (See FIG. 3).

The curl in the direction opposite to the curl direction of the reversing section 101 formed in the sheet bending section 100 is caused by the difference in speed between the rollers when the sheet is caught in the input / output roller devices 17a and 17c. As a result, the amount of deflection increases in proportion to the paper transport time (or length).
This deflection can be corrected by propagating to the rear end of the sheet as the sheet is transported. When the paper is fed into the intermediate tray, the degree of the curl in the concave direction in the intermediate tray is greatly reduced when the paper is fed into the intermediate tray, as compared with the case where the speed difference is not provided.

The paper size B (length in the transport direction: L
2 (however, L2 <L1) paper 4B
a and 16b and the paper feed and discharge roller devices 17a and 17c of the double-sided tray unit 12, the transfer speed of the paper input and output roller devices 17a and 17c of the double-sided tray unit 12 is set to V2> V1. By conveying the paper, the decoloring rollers 16a, 16b and the paper input / output roller devices 17a,
7c, the amount of curl in the opposite direction (the image-formed surface is concave) to the curl direction (the image-formed surface is convex) of the reversing portion 101 generated in the sheet bending portion 100 on the conveyance path between The same amount of curl can be generated even for paper size B (see FIG. 4).

[0031] FIG. 2 is a diagram showing a configuration around both sides tray unit. FIG. 3 is a diagram illustrating an operation on the transfer sheet 4A in the first embodiment. FIG. 4 is a diagram illustrating an operation on the transfer sheet 4B in the first embodiment.

For the curl correction by the speed difference, the paper heated by the fixing rollers 11a and 11b
When peeled from 1a and 11b, the image formed surface curls in a convex direction, and furthermore, the curl is further promoted by the inverted transport path on the way from the fixing device 11 to the intermediate tray unit 12. Is done.

For this reason, the fixing device 11 and the intermediate tray 12
In the reverse conveyance path between, two curl straightening means are arranged,
The curl is corrected in two stages. The first curl correcting unit disposed on the fixing device 11 side of the reverse conveyance path is a decurling roller pair 16. Decurling roller pair 16 is composed of a soft roller 16a forming a layer of relatively soft rubber material around a metal shaft, a rigid roller 16b forming a metal shaft on the roller. The hard roller 16b disposed on the convex side of the reversing transport path is pressed against the soft roller 16a disposed on the opposite side of the transport path, and deflects the sheet to be curled to the convex side to the opposite side. Is formed. The second curl correcting means includes a pair of decurling rollers 16 and a sheet bending portion 10.
0, a pair of paper input rollers 17.

The second curl correcting means will be described in detail below.

The second curl correcting means lowers the sheet conveying speed V1 of the pair of input rollers 17 from the sheet conveying speed V0 of the pair of decurling rollers 16 so as to convey the sheet between the pair of decurling rollers 16 and the pair of input rollers 17. Paper flexure 100 provided on road
To correct the curl by bending the sheet to the opposite side of the image forming surface.

Decal roller pair 16 and paper input roller pair 17
Of the paper, the length between the decurling roller pair 16 and the paper input roller pair 17 is
The length of the conveyance path between the paper feed roller pair 17 and the paper feed roller pair 17 gradually becomes longer from the point in time when the leading edge of the paper enters the paper feed roller pair 17. As a result, the sheet is bent in the sheet bending portion 100. This deflection increases in proportion to the time during which the sheet is conveyed.

When the conveying speed of the decurling roller pair 16 is V0,
The conveying speed of the pair of input rollers 17 is V1, the length of the conveying path between the pair of decurling rollers 16 and the pair of input rollers 17 is L0, and the length L0 is subtracted from the length of the sheet between the pair of decurling rollers 16 and the pair of input rollers 17. The length of the paper is ΔL, and the leading edge of the paper is
7 when the trailing edge of the sheet is decal roller pair 1
Assuming that the time until the paper is fed out from No. 7 is tC and the length of the sheet itself in the transport direction is LP, ΔL = (V0−V1) tC tC = (LP−L0) / V0

From these two equations, V1 / V0 = (LP-L0-ΔL) / (LP-L0).

For example, when the maximum size of the bending formed in the paper bending portion 100 is to be height ΔH = 20 mm and width ΔB = 15 mm in the transport direction, if the size of this bending is ΔL = about 12 mm I just need. Now, V0 =
133 mm / s, L0 = 60 mm, A4 size (2
10mm x 297mm) paper and B5 size (1
82 mm x 257 mm)
V0 = 122.4mm /
s, V0 = 112mm in case of B5 size paper
/ S. This is the case where the maximum amount of deflection is the same, but may be changed as appropriate according to the paper size, the size of the paper (the degree of curl varies depending on the direction of the eye), the thickness of the paper, and the like.

FIGS. 5 and 6 are diagrams for explaining the curl correction by the speed difference.

[0041] (Embodiment 2) FIG. 7 is a diagram showing the operation of the rear end plate 20.

[0042] Figure 8 is a diagram showing the operation of the rear end plate 20 in a real施例2. This will be described below with reference to FIG.

The dimension in which the length in the transport direction is shortened due to the sheet curl is measured in advance, and the rear end plate 20 is moved from a position corresponding to the sheet length in the transport direction to a position shifted in the re-feeding direction by the shortened length. Set to move. This makes it possible to sufficiently align the placement positions of the sheets.

In FIG. 8, the rear end plate 20 is shifted from the position 20b of the rear end plate 20 before the improvement in the re-feeding direction.
The edges of the transfer paper 4 are aligned at the position of.

In addition, the present invention is not limited to the embodiment described above and shown in the drawings, and it is needless to say that the present invention can be appropriately modified and implemented without departing from the scope of the invention.

[0046]

According to the paper feeding device of the double-sided image forming apparatus according to claim 1, wherein, according to the present invention, produces an effect as follows.

[0047]

[0048]

[0049]

[0050]

According to the present invention , even if the length in the transport direction is substantially shortened by the paper curl, the rear end plate 20 is moved from a position corresponding to the paper length in the transport direction to a position shifted in the direction of the paper leading end regulating position. By setting to move
It is possible to sufficiently align the paper placement positions.

[0052]

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of a duplex copying machine according to the present invention.

FIG. 2 is a diagram illustrating a configuration around a double-sided tray unit according to the present invention.

FIG. 3 is a diagram showing an operation on transfer paper 4A in the first embodiment.

FIG. 4 is a diagram showing an operation on transfer paper 4B in the first embodiment.

FIG. 5 is a diagram for explaining curl correction in the first embodiment.

FIG. 6 is a diagram for explaining curl correction in the first embodiment.

FIG. 7 is a diagram showing the operation of the rear end plate 20 under the operation of the second embodiment .

8 is a diagram showing the operation of the rear plate 20 in the form 2 operation and implementation of the second embodiment.

[Explanation of symbols]

 1: platen glass 2: photoreceptor drum 3: developing device 4: transfer paper 5: paper tray 6: discharge tray 7: merge transport path 8: PS roller 9: transfer charger 10: suction belt 11: fixing device 11- a: upper fixing roller 11-b: lower fixing roller 12: double-sided tray unit (intermediate tray unit) 13: reversing gate 16-a, b: decoloring roller (curl removing roller) 17: paper input / output roller device 17-a: paper input / output Roller 17-b: driven roller 17-c: paper input roller 19: paper holding plate 20: rear end plate 23: paper feed PG 26: re-feed path 29: transport roller 100: paper bending portion 101: reversing portion

──────────────────────────────────────────────────続 き Continued on the front page (72) Daigo Nishioka, Inventor 8-22-6, Makuyamadai, Fukuyama City, Hiroshima Prefecture (72) Keigo Hashimoto, 374-3 Motomachi, Fuchu City, Hiroshima Prefecture (72) Inventor Hitoshi Nishida, Shenzhen-gun, Hiroshima Prefecture 3122-4 Kawana, Kannabe-cho (72) Nobuhiko Sakamoto, Inventor 5552-39, Mukojima-cho, Goncho-gun, Hiroshima (72) Inventor Tatsuya Senoo 518-6, Ekemachichoji, Fukuyama-shi, Hiroshima (72) Inventor, Johei Ochi Hiroshima 780-1 Kawaminami, Kanbe-cho, Shenzhen-gun, Japan (56) References JP-A-3-232662 (JP, A) JP-A-4-338059 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G03G 15/00 G03G 15/20 G03G 21/00 G03G 21/14 B65H 5/06 B65H 9/00-9/02 B65H 29/20 B65H 29/70 B65H 83/00-85/00

Claims (1)

(57) [Claims] An image is formed on one side of a sheet by a processing unit, the sheet on which the image is formed on one side is stored in an intermediate tray, and the sheet is transported from the intermediate tray to the processing unit again. An intermediate sheet feeder for two-sided image forming adapted to a two-sided image forming apparatus for forming an image on the other side of a sheet, comprising: an intermediate tray; a sheet input conveyance path to the intermediate tray; and a discharge conveyance path from the intermediate tray. And a transport roller provided on a transport path from the process unit to the intermediate tray, wherein the paper input transport path and the discharge transport path are arranged so as to intersect one end of the intermediate tray. A straightening curl section is provided between the printer and the process section, and the rear end plate is used to align the loading position of the loaded paper.
The paper feeding position is regulated by moving the regulating position when the paper is inserted in the paper re-feeding direction by a predetermined length from the initial length in the paper transport direction to regulate the paper at the time of paper input or paper re-feeding. Paper feeder for double-sided image formation.