JPH0449179A - Sheet conveyer - Google Patents

Abstract

PURPOSE:To improve performance of refeed of a sheet in long and short various sizes and work efficiency by providing a plurality of refuge conveying paths and conveying path switching means between a sheet conveying means and a carryout means, and switching a plurality of the conveying path switching means in accordance with the size of the sheet. CONSTITUTION:A sheet is carried in by a sheet carry-in means 30, conveyed by a predetermined amount in normal/reverse directions by sheet conveying means 32a, 32b, 34a, 34b and loaded displaced by each predetermined amount to form a bundle of the sheet, and then the bundle is conveyed to sheet carry-out means 36a, 36b by the sheet conveying means 32a, 32b, 34a, 34b. Here, in the point of time of not arrival of the second sheet but arrival of a point end of the leading sheet at any of conveying path switching means 40 and 42, the bundle of the other sheet except the leading sheet takes refuge in a refuge conveying path 39 or 41 by the conveying path switching means 40 or 42 in accordance with a size of the sheet by a command of a control means 46, and the leading sheet is carried out by the sheet carry-out means 36a, 36b.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a sheet conveying device (more specifically, to a sheet refeeding mechanism from an intermediate tray in an image forming apparatus that forms images on both sides and multiple times).

(b) Prior Art FIG. 14 shows an example of a conventional double-sided multiple image forming apparatus. In the figure, 1 is the main body of the image forming apparatus, 2 is a document table on which a document is placed, 3 is a photosensitive drum that carries an image of the document, 4, 5
, 6.7 is a mirror for forming an electrostatic latent image by forming an image of the original on the photosensitive drum 3. 8 is an imaging lens.

Further, reference numeral 9 denotes a transfer electrode that transfers the toner image formed on the photosensitive drum 3 onto the sheet P.

The sheet P stored in the cassette 10 is fed to the paper feed roller 11
is taken out by the registration roller 12 at a predetermined timing synchronized with the image on the photosensitive drum 3,
After a toner image is formed on the first surface by the transfer electrode 9, the toner image is fixed by the fixing device 13. When overlapping and forming an image again on the same side of the sheet P on which the image has been formed on the first side, the sheet P is moved to the conveyance path 1 by the switching guide 14.
5 and stored in the intermediate tray 16. In addition, when forming an image on the second side opposite to the first side, the switching guide 14
guides the sheet P to the conveyance path 17, and guides the sheet P to the conveyance path 17.
After the sheet P is discharged halfway, the discharge roller 18 is reversed and the rear end of the sheet is moved to the conveyance path 20 by the switching guide 19.
and stored in the intermediate tray 16. Intermediate tray 16
Each time one sheet of paper is placed in the intermediate tray 16, the entire bundle of sheets P placed on the intermediate tray 16 is conveyed little by little by the pair of conveying rollers 21, and the sheets P are stacked one by one in a stair-like manner with a slight shift. do.

After the image forming operation on the first side is completed, the sheets stacked in a stepwise manner are conveyed all together in the direction of the roller pair 22, and the lowest sheet P leaves the roller pair 21 at the same time. By stopping, only the first sheet P held in the pair of rollers 22 at this time is conveyed by the pair of rollers 22, and the operation for the second side is performed. According to this conventional example, it is possible to improve the performance of preventing double feeding during paper refeeding.

Note that, in order to form images on both sides, a technique of stacking sheets P with an image formed on one side in a stepwise manner and refeeding them is disclosed in Japanese Patent Application Laid-open No. 58-178373 and Japanese Patent Publication No. 63-1874.
It is described in Publication No. 4, etc.

However, in the above conventional example, the first sheet P to be re-fed
is held between the roller pair 22, and the roller pair 2
It is necessary to create a state in which the other bundles of sheets P are separated from the roller pair 21 and held only by the pair of rollers 21. For this purpose, it is necessary to set the distance between the roller pair 21 and 22 to be slightly shorter than the length of the sheet P.

That is, as shown in FIG. 15(a), the roller pair 21 and 2
2 is set slightly shorter than the length of the sheet P. Therefore, the rear end of the first sheet P□ is the roller pair 21.
A little further away, the tip is held between a pair of rollers 22. Sheets P other than the first sheet P1 are moved by roller pair 21
However, since it is not held between the pair of rollers 22, the first sheet P1 is carried out by the pair of rollers 22 without rubbing against the other sheets P and therefore without being soiled.

However, as shown in FIG. 15(b), the roller pair 21.
The intervals 22 are the same as in FIG. 15(a).

When conveying a sheet P that is sufficiently longer than the case shown in FIG. 15(a) by the pair of rollers 21 and 22, if the state in which the sheet P is held by the pair of rollers 21 is the same as that shown in FIG. 13(a), The roller pair 22 in FIG. 13(b) holds not only the first sheet P1 but also the second sheet P2, etc.
When the sheets are carried out by the pair of rollers 22, the first sheet P rubs against the second sheet P2 (since it is held and stopped by the pair of rollers 21). That is, by using a pair of rollers having such a fixed interval when handling various sheets of different sizes, only the first sheet P1 can be handled without the first sheet P□ and the second sheet P2 rubbing against each other. I can't even move it out.

In addition, the state where the seat surface becomes dirty is as shown in Fig. 16.
That is, during multiple copying, the sheet P in the shaded area in the figure
The toner from the bottom surface of the nip part (a) of the second sheet P2 adheres to the top surface of the second sheet P2 and becomes dirty.
Toner (image) fades or disappears from the nip (a).

During double-sided copying, as shown in FIG. 17, toner adheres to the lower surface of the nip portion (a) of the second silt P2 and becomes dirty, and toner on the upper surface of the first sheet P1 in the diagonally shaded area (image) peels off, becomes thinner, or disappears.

For example, as shown in FIG. 18, in the case of multiple copying, when the first sheet P1 is carried out, and the second sheet 22 or more is fed backwards, the diagonal line of the first sheet P may be The top surface of the indicated area is stained with toner, and the second sheet P
The toner (image) in a wide area indicated by diagonal lines in 2 has peeled off,
Problems arise where it becomes thinner or disappears.

Therefore, in order to prevent the sheet from getting dirty or the toner from peeling off as described above, an evacuation conveyance path is provided on the sheet conveyance path, and by activating the conveyance path switching means, the paper can be held between the conveyance means, that is, the refeeding roller. A proposal as shown in FIG. 19 has been made in which the number of sheets to be processed is one or less.

In FIG. 19, there are two pairs of rollers 21 and 23, which are sheet conveying means, for conveying various sheets P of different lengths, and 22 is a pair of sheet delivery rollers. A retract conveyance path 25 is provided obliquely upward between the roller pair 23 and 22, and a conveyance path switching means 24 is pivotally supported at the lower end thereof. Then, at a predetermined timing, it moves from the position shown by the dotted line to the position shown by the solid line, and moves to the second seat 522.
The above-mentioned sheet bundle is guided to the evacuation conveyance path 25, and only the first sheet P1 is conveyed out by the pair of sheet conveyance rollers 22 without rubbing.

(c) Problems to be solved by the invention However, as shown in FIG.
If the sheets are re-fed, the length of the sheet bundle from the second sheet 522 guided to the evacuation conveyance path 25 is too long, and it interferes with the re-feed conveyance path 26 etc. that re-feeds the sheets to the pair of registration rollers 12. Therefore, the sheet P is easily bent or bent, which is a major cause of poor conveyance.

Furthermore, if the evacuation conveyance path 25 and the conveyance switching means 24 are relocated to the more upstream side to accommodate longer size sheets P, the conveyance path for loading will be shortened. There is a problem in that the number of sheets that can be stacked including short size sheets P is limited.

Therefore, the present invention provides a plurality of retreat conveyance paths and conveyance path switching means between the sheet conveyance means and the sheet discharge means,
The purpose of the present invention is to provide a sheet conveyance device that improves the performance of refeeding sheets of various sizes, long and short, and improves work efficiency by selecting one of a plurality of conveyance path switching means according to the size of the sheet. That is.

(d) Means for solving the problem The present invention has been made in view of the above circumstances, and includes:
For example, referring to FIGS. 2 and 6, sheet (P)
and a sheet carrying means (30) for carrying in the sheet (P), which transports the carried sheet (P) by a required amount in forward and reverse directions, and carries it by a predetermined amount (I2
) sheet conveyance means (32a, 32b, 34a,
34b), and sheet conveyance means (36a, 36b) for conveying out the first sheet (P) of the bundle of sheets (P) conveyed.
), the sheet carrying means (36a, 36b), and the sheet conveying means (32a, 32b).

34a, 34b) and the sheet (
A plurality of evacuation conveyance paths (39, 41) and conveyance path switching means (40, 42) for retracting the bundle of sheets (P) according to the length thereof; ,) until the second sheet (P2) arrives, the conveyance path switching means (
40, 42) to evacuate the bundle of sheets (P) other than the first sheet (Po), and the plurality of conveyance path switching means (
40, 42).

(E) Based on the above structure, the sheet (P) is transported by the sheet carrying means (
30), the carried sheet (P) is transported by a predetermined amount in the forward and reverse directions by the sheet transport means (32a, 32b, 34a, 34b), and stacked by shifting it by a predetermined amount (ρ), and the sheet jP) After forming a bundle of sheets (P), the bundle of sheets (P) is transferred to sheet conveying means (32a, 32b, 34a, 34b).
) to convey the sheet to the sheet conveyance means (36a, 36b). At this time, according to instructions from the control means (46), the leading edge of the first sheet (P,) arrives at either conveyance switching means (40 or 42) depending on the size of the sheet (P) being conveyed. However, when the second sheet (P2) does not arrive, the conveyance path switching means (40 or 42) evacuates the bundle of sheets (P) other than the first sheet (PI) of the bundle of sheets (P). The sheet is evacuated to the conveyance path (39 or 41), and the first sheet (PL) is conveyed out by the sheet conveyance means (36a, 36b).

Note that the reference numerals in parentheses are for illustrative purposes only, and do not limit equivalent configurations.

(f) Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an image forming apparatus to which the present invention is applied, and is a copying apparatus that performs duplex and multiple copying in various colors.

In FIG. 1, the configuration is common to the conventional example shown in FIG.
The same reference numerals are given to the members that act, and the description thereof will be omitted.

Therefore, the portion from the conveyance path 27 where the conveyance paths 15 and 20 merge to the registration roller 12 will be described with reference to FIGS. 1 and 2.

A sensor 29 for detecting the leading edge of the sheet P is provided at the downstream end of the transport path 27, and a pair of transport rollers 30 is provided slightly upstream of this sensor 29. Further, an upper guide 27a of the conveyance path 27 extends diagonally downward, and a substantially horizontal guide 31 is provided below this upper guide 27a to face it, and a nip is provided on substantially the same plane as the upper surface of this guide 31. A driving roller 32a made of rubber and having a small friction coefficient is provided, and a driven roller 32b made of resin with a small coefficient of friction
It is provided facing above 2a so as to be movable up and down, and is biased downward by a leaf spring 32c.

Also, a vertical guide 27 is provided on the right side of the roller pair 32a, 32b.
An upper guide 33a and a lower guide 33b similar to those shown in FIG. The roller 34a is supported by a fixed shaft, and the driven roller 34b is biased downwardly by a leaf spring 34C so as to be able to move up and down, and is brought into pressure contact with the roller 34a. And this roller pair 34a,
Upper and lower guides 35a and 35b similar to guides 33a and 33b are provided on the right side of guide 34b, and both guides 35a and 3
A driving roller 36a and a driven roller 36b are provided on the right side of the roller 5b in the same way as the roller pairs 32a, 32b, 34a, and 34b, and are biased downward by the driven roller 36b or a leaf spring 36c. Further, on the right side of the pair of rollers 36a and 36b, there is a vertical guide 37a curved upward from a flat surface.

37b is provided similarly to guides 33a, 33b, 35a, 35b.

Also, a pair of rollers 34a of the upper guide 33a.

A branch guide 39 is provided diagonally upward on the side closer to 34b, and a flapper 40 is pivotally supported on a shaft 40a at the base end of this branch guide 39. and.

Similarly, a branch guide 41 is provided diagonally upward on the side of the upper guide 35a closer to the roller pair 36a, 36b, and a flapper 42 is pivotally supported at the base end of the branch guide 41 by a shaft 42a.

Further, a sensor 43 for detecting the sheet P is attached to the upstream side of the upper guide 33a, and a similar sensor 45 is attached to the upstream side of the upper guide 35a.

The driving roller of the roller pair 3o is a roller 32a.
, 34a, 36a are stepping motors 30rn,
It is connected to 32m, 34m, and 36m via a gear train, etc., and these motors are 30m long.

32m, 34m, and 36m signal circuits are connected to the control unit 46, and a keyboard 47 for instructing the control unit 46 to specify the number of copies, duplex mode, multiple mode, copy start, etc.;
A sheet size detection device 49 is connected respectively.

In addition, the flapper 40.42 is a solenoid 40s, 42s.
The signal circuit of the solenoids 4°s and 42s is connected to the control unit 46.

Further, the rollers 30a, 32a, 34a, and 36a are made of rubber or the like having a large coefficient of friction, and the rollers 30b, 32b, and
4b and 36b are made of resin or the like having a small coefficient of friction.

Next, the operation of this embodiment will be explained.

First, the operation of storing a bundle of sheets P in the lower guides 31, 33b (sheet refeeding path) will be described with reference to the flowchart in FIG.

When the duplex or multiple copy mode is set using the keyboard 47 and a copy start is instructed, the sheet P is taken out from the cassette 10 as described above, and the photosensitive drum 3
The sheet P on which an image is formed on one side is processed in step S1.
It is sent to the roller 30, which has started rotating. After the leading edge of the sheet P is detected by the sensor 29 in step S2 in Figure 3, until the leading edge of the sheet P reaches the nip between the rollers 32a and 32b to form a loop (see Figure 4), and until the leading edges are aligned. After a predetermined time t□ (step S
3), start the motor 32m ('step S4
) Then, in order to pull out the rear end of the first sheet P1 from the roller pair 30 and the guide 27, the sheet P
The required distance β after being held between 2a and 32b is roughly set. Necessary predetermined time t2 for conveying (see Figure 5)
The motor 32m is rotated for a predetermined time t, -Δt, which is shorter than ti, and then the motor 32m is stopped (steps S7 and 8). ) motor 32
The sheet Pt is conveyed in the opposite direction by the roller pair 32a and 32b due to the reversal of the roller m, and the leading edge of the sheet P is conveyed in the opposite direction by the roller pair 32a and 32b.
A predetermined distance from the nip of 0a and 3ob! The rear end of the sheet Pl, which is located on the downstream side (see Fig. 6), is connected to the guide 31.
It is guided along the upper part and enters the lower side of the roller pair 30.

Note that the rotation of the roller pair can also be controlled by the number of pulses sent from the control section 46 to the motor 32m, and forward and reverse rotation can also be controlled by the control section 46. That is, after the leading edge of the sheet P reaches the nip between the pair of rollers 32a and 32b, the sheet P
The pair of rollers 32a and 32b can be controlled by sending a number of pulses corresponding to the rotation angle of the motor 32m necessary to convey the required distance.

Next, in step S9, it is determined whether or not the set number of sheets has been loaded, and if not, the process returns to step S2. Then, the next sheet P8 is conveyed, and the roller pair 32
When the rollers 32a and 32b reach the first sheet P2, they perform the same operation as before while holding the first sheet Pt, and push the leading edge of the second sheet P2 by a distance β from the nip between the rollers 32a and 32b. Position it on the downstream side. At this time, the first sheet P is conveyed together with the second sheet P2, and the leading edge of the first sheet P1 is located further downstream by ρ from the leading edge of the second sheet P2.

As a result, the two sheets P, , P2 are stacked with a distance β shifted from each other. By performing this operation on a set number of sheets P, the sheets can be stacked one after another with a distance as shown in FIG. 7. Then, the motor 30m stops (step 510).

In these processes, when the sheet P hits the pair of rollers 32a and 32b, the leading edge of the sheet P smoothly moves because it is the resin roller 3゜b with good sliding properties that protrudes into the conveyance path. It is possible to enter the nip between the roller pair 32a, 32b.

In the case of refeeding paper for second copying using the keyboard 47, the operation in the case of a relatively short sheet P will be described based on the flowchart shown in FIG.

When a start instruction is given from the keyboard 47, it is first determined whether the size of the sheet P is small or not. In this embodiment, the determination is made based on whether the length of the sheet P in the feeding direction is 300+u+ or more, that is, whether it is smaller than B4 size (step 511). The sheet size is detected by a sheet size detection device 49 shown in FIG. The sheet size detection device 49 may be of a type that detects the size from a known cassette, for example, or may be of a type that detects the size from the time the sheet passes through a sensor.

Here, if it is determined that the size is large, the process proceeds to [F] in FIG. 8 and an operation for large size is performed, which will be described later. If it is determined that the size is small, the motor 32m
, 34m, and 36m are started, and the bundle of stacked sheets P is sent to the roller pair 36a, 36b (steps 512, 13°14). After the rotation of the motor 32m is started, the first sheet P1 is After a predetermined time t3 necessary for the tip of the flapper 42 to reach the tip of the flapper 42 shown by the solid line in FIG. 2 has elapsed, the flapper 42 moves from the position shown by the dotted line to the position shown by the solid line. Then, the second sheet P2 is scooped up and separated from the first sheet (see FIG. 9). As shown in FIG. 10, when the time t4 necessary for leaving the roller pair 34a, 34b has elapsed, the motors 32m, 34m are reversed (step 51).
8.19). The first sea) Ps is the roller pair 36 a,
36 b, and the second sheet P2
And the upper bundle of sheets P is moved by roller pairs 32a, 32b, 3
4a and 34b and return to the original position after ts time, motors 32m and 34m stop, and flapper 4
2 returns to the position indicated by the dotted line (step S18゜19.2
0,21.22).

Furthermore, after the predetermined time t6 has elapsed, the motor 36m is stopped, and the first sheet P1 is conveyed to the registration rollers 12,
Next image formation occurs (step 323.24).

Then, it is determined whether or not refeeding of the set number of sheets has been completed (step 525), and if it has not been completed, (
Return to step 512).

In this configuration, sheets P of different sizes can be stacked in a stepwise manner, separated and re-fed without changing the interval between the roller pairs according to the length of the sheets P, and the sheets P can be separated and re-fed. There is no possibility of rubbing between p2. That is, when stacking the sheets P in a stepwise manner, the time t2 in the flowchart of FIG. , sheet P0') rear end is connected to roller pair 30 and guide 2.
In order to remove the sheet from 7, the length of the long sheet P should be increased by lengthening t2. Similarly, if t2-Δt is also set according to the length of the sheet P, sheets P of different sizes can be stacked while being shifted by the length ρ. t4, f in the flowchart of FIG.
, a depending on the length of the sheet P. Since t4 is the time required for the rear end of the first sheet P1 to come out of the roller pair 34a, 34b, the longer sheet P is set to be longer.

Time t.

is the time required to return the sheets P other than the first sheet P1, and the longer sheet P becomes longer.

The size of the sheet P is detected by the sheet size detection device 49, and the size is 1°j 2 , j 2− according to the detected size.
△t, j4. js time is calculated by the control unit 46.

Furthermore, if the size detection device 49 determines that the size of the sheet P is long, that is, the branch guide 41 and the flapper 4
If it is determined that a problem will occur if the sheets are evacuated by step 2, the second sheet 22 or more sheets are evacuated by the flapper 40 to perform paper refeeding. Its operation will be explained based on the flowchart shown in FIG.

When a start instruction is given from the keyboard 47, the rotation of the motors 32m, 34m, and 36m is started, and the bundle of sheets P is sent to the roller pairs 34a and 34b (step 31).
, 32.33).

The first sheet P after the rotation of the motor 32m has started,
is detected by the sensor 43, and the time required for it to be at the position shown in FIG. After the above period, the flapper 40 is operated (steps 34, 35 and 36). Then, as shown in FIG.
A bundle of sheets P including the second sheet 22 and above is handled by a flapper 40.
The first sheet P1 is moved by the roller pair 32a, 3.
When the time t8 required to pass through 2b has elapsed (step 37, see FIG. 12), the motor 32m reverses (
Step 38). At this time, the first sheet P1 is not rubbed by the second sheet P2.

After time t9 has elapsed, sheets P except the earliest sheet P
When the bundle returns to its original position, the motor 32m stops and the flapper 406 returns to its original position (steps 39 and 4).
0.41).

When the first sheet P1 reaches the pair of registration rollers 12 after the time tlo has elapsed, the motor 34m is activated.

36'm stops (step 42.43). When the work for the set number of sheets P is completed (step S44), the copying work ends (step 544).

In the above, the time j 8 + 91 j 1° changes depending on the length of the sheet P.

In the above embodiment, the sheets Px were stacked on the intermediate trays 31 and 33 so that the first sheet Px was stacked on the bottom, but as shown in FIG.
1. The flapper 52 and the branch guide 53 are arranged on the opposite side from the flapper 40, the branch guide 39, the flapper 42, and the branch guide 41 of the above embodiment, so that β shown in FIG. 6 is -β, that is, the roller pair 32a, 32b. This can be easily carried out even when the sheets P are stacked in a stairway so that the first sheet P is located at the top by setting the leading edge of the first sheet P1 at a position ρ away from the left side of the sheet P1. can. However, in order to position the first sheet P1 at one β, roller pair -32a is required.
, 32b, it is necessary to additionally install a pair of rollers 55 on the left guide 31.

(G) As described in detail, according to the present invention, a plurality of evacuation conveyance paths and conveyance path switching means are provided for retracting the sheet bundle according to the length thereof, and a plurality of evacuation conveyance paths and conveyance path switching means are provided for retracting the sheet bundle according to the length of the sheet bundle. Since the conveyance path switching means is selected by the control means, when refeeding the first sheet, it is possible to easily create an evacuation space for the bundle of remaining sheets, and stable conveyance performance can be obtained. can.

Further, since the distance over which the sheet bundle is conveyed in the forward and reverse directions can be shortened in accordance with the length of the sheets, copying work time can be saved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional front view of a copying machine implementing the sheet conveying device of the present invention, FIG. 2 is a cross-sectional front view of the sheet conveying device,
Figure 3 is a flowchart when loading sheets, Figure 4,
Figures 5, 6, and 7 are cross-sectional front views showing the intermediate stage, Figure 8 is a flowchart showing short sheet refeeding, and Figures 9 and 10 are the intermediate stages. Fig. 11 is a flowchart showing the refeeding operation of a long sheet, and Fig. 12 is a flowchart showing the sheet refeeding operation for a long sheet. 13 is a sectional front view showing another embodiment, FIG. 14 is a sectional front view showing a conventional copying machine, and FIG. 15(a) is a conveyance roller for sheets. Fig. 15 is a front view showing the correct arrangement of the sheet, and Fig. 15 is a front view showing a state in which a longer sheet is being conveyed to the conveying rollers in that arrangement. Fig. 16, Fig. 17, and Fig. 18 are A front view showing a state in which the first sheet and the second sheet rub against each other, FIG. 19 is a cross-sectional front view showing an example of a conventional proposal regarding the evacuation conveyance path, and FIG. 20 is a cross-sectional front view showing an inconvenient state thereof. is. eye sheet

Claims (1)

[Claims] 1. A sheet carrying means for carrying in sheets, a sheet carrying means for carrying the carried sheets by a required amount in forward and reverse directions, shifting them by a predetermined amount and stacking them, and conveying a bundle of stacked sheets; a sheet carry-out means for carrying out the foremost sheet of the bundle of sheets; and a sheet carry-out means located between the sheet carry-out means and the sheet conveyance means to evacuate the bundle of sheets to be conveyed according to the length thereof. a plurality of evacuation conveyance paths and a conveyance path switching means, and a plurality of conveyance paths from when the leading edge of the first sheet of the bundle of sheets reaches the leading edge of the conveyance path switching means until the second sheet arrives; 1. A sheet conveying device comprising: control means for causing a switching means to retreat a bundle of sheets other than the first sheet, and for controlling one of a plurality of conveyance path switching means to be selected.