JP2002211789A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily switch the carrying direction of sheets even when the sheets are carried in such a state that the rear end of a preceding sheet is overlapped by a specified amount with the top end of a following sheet. SOLUTION: This image forming device comprises a sheet rear end restricting means 4 disposed in a sheet carrying route 3 between a sheet feed means 1 and an image forming means 2 and a carrying direction switching means 51 disposed in a branch part 5 for branching the sheet carrying route 3 into a first sheet carrying route 56 and a second sheet carrying route 57 on the downstream side of the image forming means and switching the carrying direction of the sheets passed through the image forming means. When the sheets are carried continuously, the sheet rear end restricting means 4 restricts the rear end position of the preceding sheet to either of the sheet carrying routes 3 to determine the positional relation thereof with the top end of the following sheet. Based on the positional relation of the sheets determined by the sheet rear end restricting means 4, the carrying direction switching means 51 switches the sheet carrying direction so as to load the sheets into either of the first and second sheet carrying routes 56 and 57.

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 and a printer.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, an image is formed on both sides of a sheet.
Some sheets are provided with a sheet reversing unit, a double-sided pass, and the like for reversing the image surface of a sheet on which an image is formed by the image forming unit and sending the sheet to the image forming unit again. And in this case,
For example, at a subsequent stage of the image forming section, a first path for discharging a sheet and a branch path branched into a second path connected to the double-sided conveyance path are provided, and the sheet is placed on the branch path. A transport direction switching means such as a flapper for guiding the user to the path is arranged.

In the image forming apparatus having such a configuration, when an image is formed on both sides of a continuous sheet in order to increase the throughput, the sheet sent from a sheet storage means such as a paper feed cassette and the sheet are re-passed through a double-sided path. There is an image forming apparatus that employs a so-called alternate sheet feeding method in which sheets to be fed are alternately sent to an image forming unit. In the image forming apparatus of this type, since a plurality of continuously conveyed sheets need to be alternately sorted and conveyed into a first pass and a second pass, a predetermined interval between sheets (a preceding sheet and a succeeding sheet) is required. A gap between the sheets is opened, and at the time of arrival between the sheets, the position of a conveying direction switching means such as a flapper is switched to perform the sorting and conveying of the sheets.

FIG. 7 shows a configuration of a main part at a subsequent stage of an image forming section of such a conventional image forming apparatus. In FIG.
Reference numeral 110 denotes a fixing unit which is a component of the image forming unit; 111, a conveying roller provided at a stage subsequent to the fixing unit 110; 101, a rotatable flapper serving as a conveying direction switching unit;
Is a discharge roller for discharging sheets to the tray 113,
102 is a reversing path for reversing the image plane of the sheet,
A double-sided conveyance path 104 is connected to the reversing path 102, and feeds the sheet with the image side reversed to the image forming unit again.
Reference numeral 112 denotes a pair of reversing rollers provided in the reversing path 102 and capable of normal and reverse rotation.

In the conventional image forming apparatus, as shown in FIG. 7, when a preceding sheet P1 and a succeeding sheet P2 are continuously conveyed, the flapper 101 rotates when the sheet P1 and the sheet P2 arrive between the sheets. By moving
, And the conveyance direction of both sheets is switched. In the example of FIG. 7, the preceding sheet P1 is
2, the subsequent sheet P2 is guided toward the discharge roller 103 by the turned flapper 101.

[0006]

However, in such a conventional structure, the distance between the sheets is at least as long as the length at which the flapper 101 can be inserted, in other words, when the flapper 101 is rotated, the leading distance is obtained. The length between the sheets must be such that the rear end of the sheet P1 and the front end of the succeeding sheet P2 do not interfere with the rotating flapper 101, respectively. On the other hand, from the viewpoint of the number of sheets printed per unit time (productivity of sheet output: throughput), the longer the interval between sheets, the smaller the number of sheets printed per unit time. In addition, there is a study to make a so-called minus between the sheets, that is, to overlap the trailing edge of the preceding sheet and the leading edge of the succeeding sheet by a predetermined amount.

SUMMARY OF THE INVENTION It is an object of the present invention to convey between a sheet having no gap between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet, or to overlap the preceding sheet and the succeeding sheet by a predetermined amount. An object of the present invention is to provide an image forming apparatus capable of satisfactorily switching the conveying direction of each sheet even when the sheets are conveyed.

[0008]

The main components of an image forming apparatus according to the present invention include a sheet conveying path for guiding a sheet to image forming means for forming an image on the sheet, and a trailing end of the sheet passing through the sheet conveying path. A sheet trailing end regulating unit for regulating the position to one side of the sheet conveying path, and a branching unit that branches to a first sheet conveying path and a second sheet conveying path downstream of the image forming unit, Transport direction switching means for switching the transport direction of the sheet that has passed through the image forming means between the first sheet transport path and the second sheet transport path. The position of the trailing edge of the preceding sheet is restricted to one side of the sheet transport path to determine the positional relationship with the leading edge of the succeeding sheet, and the transport direction switching means is determined by the sheet trailing edge regulating means. Position of each sheet Based on, to direct each sheet to either the first sheet conveying path and the second sheet conveying path, it switches the conveying direction of the sheet.

[0009]

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

First, an overall configuration of an image forming apparatus to which the present invention is applied will be described with reference to FIG. FIG.
1 is a main cross-sectional view of a copying machine that is an embodiment of an image forming apparatus according to the present invention.

As shown in FIG. 1, a copying machine according to an embodiment includes a sheet feeding unit 1 serving as a sheet feeding unit for stacking and storing sheets and feeding the sheets one by one. An image forming unit 2 serving as an image forming unit for forming an image on a fed sheet; a sheet conveying path 3 connecting the sheet feeding unit 1 and the image forming unit 2; and a downstream side of the image forming unit 2 A branching section 5 whose details will be described later, and a sheet discharge tray 8 and a sheet reversing section 9 arranged at a stage subsequent to the branching section 5.
And a two-sided pass 10 disposed after the sheet reversing section 9
And a sheet rear end regulating section 4 arranged in the sheet conveying path 3 and described in detail later. In this embodiment, as shown in FIG. 1, a sheet trailing edge regulating unit 4 as a sheet trailing edge regulating unit is disposed downstream of a junction 11 between the two-sided path 10 and the sheet conveying path 3.

Although not shown, in the copying machine according to the embodiment, a document reading section for reading a document image is arranged at the top of the apparatus, and a document image read by the document reading section is provided below the document reading section. And a laser scanner for outputting a laser beam based on the laser beam.

In the embodiment, a double-sided mode in which an image is formed on both sides of a sheet in the image forming unit 2, a single-sided printing is performed in the image forming unit 2, and the printing surface is turned upward on the sheet discharge tray 8. A face-up stacking mode for face-up discharge and stacking, and a face-down stacking mode for performing single-sided printing with the image forming unit 2 and face-down discharging and stacking the print surface downward on the sheet discharge tray 8 can be selected. It has become. The operation of each unit in each of these modes will be described later.

The sheet feeding section 1 includes a tray 1a for stacking and storing sheets, a pickup roller 1b for contacting the uppermost sheet stacked and stored on the tray 1a, and an intermediate plate (not shown) for pushing up the sheets in the tray 1a. And a feed roller 1c and a retard roller 1d for separating the sheet picked up by the pickup roller 1b into one sheet and sending the sheet to the sheet conveying path 3.

In this embodiment, the sheet separating mechanism includes a feed roller 1c and a retard roller 1c.
Although the roller separation method by d is used, a claw separation method or a friction piece method may be used.

The image forming section 2 has an electrophotographic image forming means in this embodiment. Specifically, a photosensitive drum 2a as an image carrier to which the laser beam of the laser scanner is irradiated, A registration roller 2b disposed in front of the photosensitive drum 2a and rotating in synchronization with the rotation of the photosensitive drum 2a; a developing device 2c for developing an electrostatic latent image formed on the photosensitive drum 2a by irradiation of laser light A fixing unit 2d disposed downstream of the photosensitive drum 2a; and a transport belt 2e for transporting the sheet passing through the photosensitive drum 2a to the fixing unit 2d. The image forming unit of the image forming unit 2 may have another configuration such as an inkjet system.

In the middle of a sheet conveying path 3 connecting the sheet storing section and the sheet feeding section 1 to the image forming section 2, the rear end position of the sheet passing through the sheet conveying path 3 is set to one of the sheet conveying paths 3. A sheet rear end regulating portion 4 for regulating to the side is disposed. Further, on the downstream side of the image forming unit 2, a branching unit 5 is disposed, and by a flapper 51 as a conveying direction switching unit disposed at the center of the branching unit 5, the downstream side of the image forming unit 2 and the conveying roller 6 is provided. The first conveyance path 56 is connected to the discharge roller 7 and the sheet discharge tray 8, and the second conveyance path 57 is connected to the sheet reversing unit 9 and the duplex path 10.
The third transport path 58 is connected to both downstream sides of the first transport path 56 and the second transport path 57.
Is formed.

Here, the configuration around the branching section 5 and the sheet reversing section 9 will be described with reference to FIG. As shown in FIG. 5, the flapper 51 of the branch portion 5 has a substantially triangular cross section, and the guide member 5 has a pivot shaft 51a as a center.
It is rotatably supported within 0. This flapper 51
Is rotated by driving means such as a solenoid (not shown),
It is set to one of two positions, a position α and a position β described later. At the lower end of the flapper 51 in FIG. 5, a backflow prevention member 52 made of a flexible sheet material for preventing backflow of a sheet in a face-down stacking mode described later is provided.

The sheet reversing section 9 includes a reversing path 90 as sheet reversing means for reversing the image surface of the sheet, and a pair of reversing rollers 91 provided on the reversing path 90 and capable of normal and reverse rotation.
And a sheet trailing edge detection unit 95 provided on the reversing path 90 at the preceding stage of the pair of reversing rollers 91 to detect the trailing edge of the sheet passing through the second conveying path 57 and the reversing path 90. .

One end of the reversing path 90 of the sheet reversing section 9 is connected to the second conveyance path 57, and is connected to the upstream side of the two-sided path 10 at a position between the urging member 94 and the pair of reversing rollers 91. . At the confluence of the reversing path 90 and the two-sided path 10, a backflow prevention member 92 made of a flexible sheet material for preventing a backflow of the sheet in the both-side mode described later.
Is provided.

The sheet trailing edge detector 95 has a sensor (not shown), a guide member 94 for contacting the sheet and switching the sensor on and off, and a spring 93 connected to the guide member 94. The guide member 94 can swing around a shaft portion 94a at one end, and a spring 93 is connected to the other end.

A double-sided path 10 as a sheet re-conveying path connected to the reversing path 90 is for re-conveying the sheet reversed by the pair of reversing rollers 91 to the image forming section 2 and is shown in FIG. As described above, a plurality of double-sided conveying rollers 10 a as sheet re-conveying means are provided, and the downstream side is connected to the sheet conveying path 3 in the preceding stage of the sheet rear end regulating section 4.

Next, with reference to FIG. 2, a description will be given of the sheet trailing edge regulating section 4 which is a sheet trailing edge regulating means. As shown in FIG. 2, the sheet rear end regulating portion 4 has a pair of regulating members 41a and 41b for regulating the position of the sheet. Each of the restricting members 41a and 41b is configured to be rotatable about each roller shaft of the pair of conveying rollers 41 arranged in the sheet conveying path 3 as a center of rotation.

Each of the restricting members 41a and 41b is adapted to rotate in conjunction with the driving force of a driving means (not shown), and to rotate in a first position shown in FIG.
It is set to one of the second two positions shown in FIG. Here, in the first position, the right regulating member 41a in FIG. 2 urges and presses the sheet toward the right guide member 31 forming the sheet conveying path 3, and in the second position, the regulating member 41a in FIG. Left regulating member 41
The state b is such that the sheet is urged and pressed against the left guide member 32 forming the sheet conveying path 3. As described above, the sheet rear end regulating portion 4 is provided with the regulating members 41a and 41b.
Then, the position of the sheet is regulated by urging the first sheet to one side of the sheet conveying path 3.

In this embodiment, as shown in FIG.
The sheet P1 is transported by the transport roller 35 in the sheet transport path 3, and the leading end of the sheet P1 is
b, so that the rear end of the sheet P1 is located on the leading end side of each of the regulating members 41a, 41b when the sheet P1 is sandwiched between the rollers 2b, 35, 41, and each of the regulating members 41a, 41b. 41b is arranged along the sheet conveying path 3.

Then, the sheet P1 is moved to the registration roller 2b.
Each of the regulating members 41 is
2A is rotated clockwise from the second position in FIG. 2B, for example, and is switched to the first position in FIG. 2A, so that the regulating member 41a moves the sheet conveying path. With the operation of invading the path of the third sheet, the sheet P
The rear end of the sheet 1 is pressed and urged by the regulating member 41a to be pressed against the right side (the guide member 31 side) in the sheet conveying path 3. At this time, as shown in FIG. 2A, the leading end of the succeeding sheet P2 that has entered the sheet conveying path 3 is
1a, the preceding sheet P1
Is placed on the left side of.

On the other hand, each of the regulating members 41a and 41b is
In the state where the sheet P1 is set to the second position shown in (b), the rear end of the preceding sheet P1 is urged to the left by the regulating member 41b, contrary to the case of the first position,
The leading end of the succeeding sheet P2 is superimposed on the right side of the preceding sheet P1.

In each position shown in FIG. 2, it is assumed that the overlapping amount of the preceding sheet and the succeeding sheet is about 5 mm. The amount of overlap between the preceding sheet and the succeeding sheet is not particularly limited, but is set to be at least smaller than the image missing amount in the image forming unit 2.

FIGS. 3A to 3F are views for explaining the operation of the flapper 51 as the transport direction switching means in the branching section 5 at the subsequent stage of the image forming section 2. FIG. As described above, the flapper 51 can be rotated by driving means such as a solenoid (not shown), and is set to one of two positions α and β. Here, the state in which the upstream end of the flapper 51 is located below the immediately preceding (the transport roller 6 side) transport path (the state shown in FIGS. 3B, 3C, and 3D) is defined as a position α. The state in which the upstream end of the flapper 51 is located above the immediately preceding conveyance path (FIG. 3)
(A), (e) and (f) are defined as position β.

In this embodiment, the flapper 51 switches the conveying direction of each sheet based on the positional relationship of each sheet determined by the sheet rear end regulating unit 4 as the sheet rear end regulating means. ing. In particular,
The flapper 51 switches from the position α to the position β for the sheets P1 and P2 that have passed while the sheet rear end regulating portion 4 is set at the first position in FIG. The sheet P1 is transferred to the first conveying path 56.
Next, the sheet P2 is guided to the second transport path 57 (FIGS. 3D to 3F). The flapper 51 switches from the position β to the position α for the sheets P1 and P2 that have passed while the sheet rear end regulating portion 4 is set at the second position in FIG. 2B. Then, the sheet P1 is guided to the second transport path 57, and the sheet P2 is guided to the first transport path 56 (FIGS. 3A to 3C).

The details of the operation of the sheet trailing edge regulating portion 4 and the flapper 51 in each of the duplex mode, the face-up stacking mode, and the face-down stacking mode will be described below.

(Duplex Mode) In the copying machine of the present embodiment, in a duplex mode in which images are formed on both sides of a sheet, a so-called stack without a duplex (intermediate) tray for stacking and storing sheets in the middle of a duplex conveying path is provided. A sheet on which image formation on the first side is performed by a less-type double-sided conveyance method,
The so-called alternate sheet feeding, in which an unprinted sheet on which the image formation on the first side is not performed, is alternately fed to the image forming unit 2 is performed as a basic operation. That is, at the time of this alternate sheet feeding, the unprinted sheet fed from the sheet feeding unit 1 and the image forming of the first side are performed by the image forming unit 2, and the sheet is turned from the sheet duplex path 10 through the sheet reversing unit 9. The conveyed sheets are merged one by one alternately at the merging section 11, and the sheet sent from the sheet feeding section 1 and the sheet sent from the double-sided path 10 are sent to the sheet conveying path 3 downstream of the merging section 11. The incoming sheets are alternately conveyed to the image forming unit 2.

In this embodiment, the unprinted sheet sent from the sheet feeding unit 1 and the sheet printed on the first side sent from the two-sided path 10 are joined. When merging at the section 11, each roller 1 is moved so that the trailing edge of the preceding sheet and the leading edge of the succeeding sheet overlap by a predetermined amount.
The rotational speeds of b, 1c, and 10a are set, and the positional relationship between the trailing edge of the preceding sheet and the trailing edge of the succeeding sheet is determined by switching the position of the trailing edge regulating section 4. ing.

That is, at the time of this alternate sheet feeding, the position of the sheet trailing end regulating section 4 is switched for each sheet, so that each sheet fed to the image forming section 2 is as shown in FIG. As shown, the unprinted sheets (P1, P3, P5...) Are on the lower side, and the printed sheets (P2, P4, P6...) On the first surface are on the upper side.

The position of the flapper 51 corresponding to the positional relationship between the sheets determined by the sheet rear end regulating section 4 is switched, so that the flapper 51 is switched.
The single-sided printing sheet that has passed through the image forming unit 2 is guided to the second conveyance path 57 on the side of the double-sided path 10, and
Are guided to the first transport path 56 on the sheet discharge tray 8 side.

Here, with respect to the sheets merged at the merging section 11, a case is considered in which the preceding sheet P1 is unprinted and the succeeding sheet P2 is printed on the first surface.
As shown in FIG. 2B, when the sheet trailing edge regulating portion 4 is set to the second position, the leading edge of the sheet P2 on which the first surface is printed is the leading edge of the unprinted sheet P1. On the right side of Since the sheet P3 subsequent to the sheet P2 is in an unprinted state, the sheet rear end regulating unit 4 is switched to the first position before the rear end of the sheet P2 passes (FIG. 2 ( a)).

The preceding unprinted sheet P1 is
When the image forming unit 2 performs printing on the first surface and enters the branching unit 5, as shown in FIG.
When 1 is set at the position β, the sheet is sent to the double-sided path 10 through the second conveyance path 57 and the sheet reversing section 9.

Thereafter, the succeeding sheet P2 is transferred to the image forming section 2
When the printing is performed on the second surface and enters the branching section 5 as shown in FIG. 3B, the flapper 51 is moved to the position α while the preceding sheet P1 is passing through the branching section 5 as shown in FIG. Can be switched. By switching to the position α, the upstream end of the flapper 51 is positioned below the immediately preceding sheet path, and the front end of the succeeding sheet P2 is positioned above the rear end of the preceding sheet P1 currently passing. , The sheet P2 on which printing on both sides has been completed has a flapper 51 despite the state where there is no space between sheets (minus).
The switching of the sheet conveyance direction is performed satisfactorily, and FIG.
As shown in (c), the sheet can advance to the first conveyance path 56 on the sheet discharge tray 8 side.

(Face Up Stacking Mode) Next, one-sided printing is performed by the image forming unit 2 and the sheet discharge tray 8
The face-up stacking mode in which the printing surface is face-up discharged upward and stacked above will be described. In the face-up stacking mode, the sheet printed on the upper surface by the image forming unit 2 is transferred to the first conveying roller 6 and the first
The sheet discharge tray 8 passes through the conveyance path 56 and the conveyance roller 7
Will be discharged and loaded.

FIG. 4A shows a state in which the leading edge of the succeeding sheet is superimposed below the trailing edge of the preceding sheet. In this state, the preceding sheet may be pushed out by the succeeding sheet and fall from the sheet discharge tray 8.

Therefore, during the face-up stacking mode, as shown in FIG.
Is fixed in the second position and set
The leading edge of the following sheet always overlaps the right side of the preceding sheet. The flapper 51 is fixedly set at the position α.

As shown in FIG. 6B, each sheet fed to the image forming section 2 overlaps the rear end of the preceding sheet so that the leading end of the succeeding sheet is always on top. In the sheet discharge section,
As shown in FIG. 4B, a similar state is obtained, and each sheet can be reliably stacked on the sheet discharge tray 8 even when there is no sheet interval (minus).

(When double-sided printing is performed during the face-up stacking mode) In the copying machine of this embodiment, when a sheet is continuously fed from the sheet feeding unit 1 and discharged face-up, a predetermined sheet is discharged. It is also possible to selectively perform double-sided printing. Hereinafter, an operation when performing double-sided printing on a predetermined sheet P2 in the face-up stacking mode will be described.

In this case, the sheet trailing edge regulating section 4 is normally set to the second position and the flapper 51 is set to the position α as described above. Rear end regulating part 4 when passing
Is switched to the first position, and the flapper 51 is switched to the position β as follows.

That is, as shown in FIG. 2A, when the sheet P1 passes through the sheet P1, the sheet rear end regulating portion 4 moves the sheet P1 and the sheet P2 sent from the sheet feeding section 1 from the second position to the first position. , The leading edge of the succeeding sheet P2 causes the leading end of the preceding sheet P1.
Is placed on the left side of the rear end. After the preceding sheet P1 and the succeeding sheet P2 have passed through the image forming unit 2 in this state, as shown in FIG. And is sent to the sheet discharge tray 8. At this time, specifically, as shown in FIG. 3E, the flapper 51 is positioned before the following sheet P2 enters the branch portion 5 and while the preceding sheet P1 passes through the branch portion 5. Position β from α
Can be switched to

At this time, as shown in FIG. 3E, the upstream end portion 51b of the flapper 51 is located above the immediately preceding path, and the leading end of the succeeding sheet P2 is ahead of the currently passing sheet. Since the following sheet P2 is stacked below the sheet P1, the conveyance direction of the succeeding sheet P2 is favorably switched by the flapper 51 regardless of the distance from the preceding sheet P1, that is, the state where there is no gap between the sheets (minus). , FIG.
As shown in (f), it is possible to proceed to the second transport path 57 connected to the reverse path 90 and the two-sided path 10. The sheet P
For the succeeding sheet of No. 2, in order to discharge the face-up like the sheet P1, at the time of passing the sheet P2,
Move the sheet trailing edge regulating portion 4 to the second position,
1 may be switched back to the position α.

(Face Down Stacking Mode) Next, one-sided printing is performed by the image forming section 2 and the sheet discharge tray 8
The face-down stacking mode in which the print surface is face-down ejected downward and stacked above will be described. In the face-up stacking mode, the sheet printed on the upper surface by the image forming unit 2 is transferred to the second conveying roller 6 and the second
After passing through the conveying path 57, the reversing path 90, and the reversing roller pair 91, the reversing roller pair 91 is reversed and discharged onto the sheet discharge tray 8 through the third conveying path 58 to be stacked.

In the face-down stacking mode, contrary to the face-up stacking mode described above, as shown in FIG. 2A, the sheet rear end regulating portion 4 is fixed and set at the first position. The leading edge of the following sheet always overlaps the left side of the preceding sheet. The flapper 51 is fixedly set at the position β.

As shown in FIG. 6C, each sheet fed to the image forming section 2 overlaps the rear end of the preceding sheet so that the leading end of the succeeding sheet is always lower. State. Further, in the branching section 5 at the subsequent stage of the image forming section 2, as shown in FIG.
Is guided to the second conveyance path 57 by the flapper 51 set at the position β, and the leading end of the sheet P1 sequentially passes through the backflow prevention member 52, the guide member 94, and the backflow prevention member 92, and It is drawn into the reversing roller pair 91.

Here, when the sheet P1 passes through the guide member 94, the guide member 94 moves to the right side in FIG. The sensor in the detection unit 95 is switched from, for example, off to on, and at the timing when the rear end of the sheet P1 passes through the reversing sheet 52, the sensor is switched, for example, from on to off. In this embodiment, at the timing when the rear end of the sheet P1 passes through the reversing sheet 52 and the output of the sensor is switched, the reversing roller pair 91 is reversely driven in the direction opposite to the arrow direction (forward rotation) in FIG. Then, the sheet P1 is sent to the sheet discharge tray 8 through the third transfer path 58 and the discharge rollers 7 with the rear end up to that point as the front end in the transfer direction.

As described above, according to the copying machine of the embodiment, even in the face-down stacking mode, the switching of the sheet conveying direction by the flapper 51 can be performed satisfactorily even though there is no sheet (minus). In this way, each sheet can be turned over without causing interference between the preceding sheet and the succeeding sheet, and each sheet can be discharged face-down onto the sheet discharge tray 8.

In the above-described embodiment, the first transport path 56 connected to the sheet discharge tray 8 is formed in the branching section 5 in a substantially horizontal direction, and the second transport path 57 connected to the two-sided path 10 and the reverse path 90. Is formed in the lower left direction in the branch portion 5, but the present invention is not limited to this, and may be in any direction.

In the above-described embodiment, the case where the trailing edge of the preceding sheet and the leading edge of the succeeding sheet are conveyed in an overlapping manner has been described. However, the present invention is not limited to this. Even when the sheet is conveyed with the distance between the sheets being zero or the sheet being minutely provided, the flapper 51
, The switching of the sheet conveyance direction is performed satisfactorily.

[0054]

As described above, according to the present invention,
It is possible to provide an image forming apparatus capable of favorably switching the conveyance direction between the preceding sheet and the succeeding sheet.
Therefore, even if the interval between sheets is narrowed in order to increase the throughput of image processing, or if a preceding sheet and a succeeding sheet are conveyed while being overlapped by a predetermined amount, reliable and stable conveyance can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining an overall configuration of a copying machine according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a positional relationship between a position of a sheet rear end regulating portion and a front end rear end of each sheet. FIG. 2A illustrates a state where the sheet rear end regulating portion is at a first position, and FIG. The state in the position is shown in FIG.

FIGS. 3A to 3C are diagrams illustrating a flapper switching operation and a sheet conveying operation, and FIGS. 3A to 3C illustrate a case where the flapper is switched from a position β to a position α; FIGS.
The case where the flapper is switched from the position α to the position β is shown in (d) to (f).

4A and 4B are diagrams for explaining a state of stacking sheets on a sheet discharge tray in a face-up stacking mode, in which a leading end of a succeeding sheet is located below a trailing end of a preceding sheet (a). (B) shows the positional relationship of each sheet in the present embodiment.

FIG. 5 is a cross-sectional view illustrating a configuration of a branch portion and its surroundings, and a movement of each sheet and a positional relationship between a leading end and a trailing end in a face-down stacking mode.

6A and 6B are diagrams illustrating the positional relationship between the leading edge and the trailing edge of each sheet in each mode of the copying machine according to the embodiment, wherein FIG. 6A illustrates a case where alternate sheet feeding in a duplex printing mode is performed, and FIG.
Shows the case of the face-up loading mode, and FIG. 3C shows the case of the face-down loading mode.

FIG. 7 is a diagram illustrating a configuration of a subsequent stage of an image forming unit in a conventional image forming apparatus, and illustrating a case where a conveyance direction of a preceding sheet and a succeeding sheet is switched.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sheet feeding part (sheet feeding means) 1a Tray 1b Pickup roller 1c Feed roller 1d Retard roller 2 Image forming part (image forming means) 2a Photoconductor drum 2b Registration roller 2c Developing device 2d Fixing device 2e Transport belt portion 3 Sheet Conveying paths 31, 32 Guide member 35 Conveying roller 4 Sheet trailing edge regulating section (sheet trailing edge regulating means) 5 Branching section 6 Transport roller 7 Discharge roller (sheet discharging means) 8 Sheet discharging tray 9 Sheet reversing section 10 Double-sided path (sheet) Re-conveying path, sheet re-conveying means) 10a Double-sided conveying roller (sheet re-conveying means) 11 Merging portion 2b Registration roller 41 Conveying roller pair 41a, 41b Restriction member 50 Guide member 51 Flapper (conveying direction switching means) 51a Rotating shaft 51b Upstream end 52, 92 Backflow prevention member 56 1st conveyance path (first sheet conveyance path) 57 2nd conveyance path (2nd sheet conveyance path) 58 3rd conveyance path (3rd sheet conveyance path) 90 inversion path 91 inversion roller pair (sheet inversion) Means) 94 guide member 95 sheet trailing edge detection unit

Claims (7)

[Claims] 1. A sheet conveying path for guiding a sheet to image forming means for forming an image on the sheet, and a sheet for regulating a rear end position of the sheet passing through the sheet conveying path to one side of the sheet conveying path. A rear end regulating unit, a first sheet conveying path downstream of the image forming unit, and a second sheet conveying path.
A conveyance direction switching unit that is disposed at a branch portion that branches to the sheet conveyance path, and switches a conveyance direction of the sheet that has passed through the image forming unit to the first sheet conveyance path and the second sheet conveyance path; When the sheet is continuously conveyed, the sheet trailing edge regulating means regulates the trailing edge position of the preceding sheet to one side of the sheet transport path, and the positional relationship with the leading edge of the succeeding sheet. The conveyance direction switching means, based on the positional relationship of each sheet determined by the sheet rear end regulating means,
An image forming apparatus, wherein a sheet conveyance direction is switched so that each sheet is guided to one of the first sheet conveyance path and the second sheet conveyance path. 2. The sheet trailing edge regulation when each sheet on which an image has been formed by the image forming unit is conveyed by the conveyance direction switching unit to the first conveyance path and the second conveyance path. Means for transporting the trailing edge position of the preceding sheet so that the leading edge position of the sheet to be transported to the first transport path overlaps the trailing edge of the preceding sheet on the first transport path side. The sheet is regulated to one side of the path, and the leading end position of the sheet to be conveyed to the second conveying path is overlapped with the trailing end of the preceding sheet on the second conveying path side. 2. An end position is restricted to one side of the sheet conveying path.
The image forming apparatus as described in the above. And a sheet reversing means for reversing an image surface of the sheet, wherein the first sheet conveying path comprises a sheet discharging means for discharging the sheet and the sheet discharging means. Means, and the second sheet conveying path is
3. The image forming apparatus according to claim 2, wherein the image forming unit and the sheet reversing unit are connected. 4. A sheet feeding means for storing sheets on which an image is formed by the image forming means and feeding the sheets one by one to the sheet conveying path, and a sheet inverted by the sheet reversing means to the image forming means again. A sheet re-conveying means having a sheet re-conveying path for returning, wherein the sheet re-conveying path has a downstream side connected to the sheet conveying path between the sheet rear end regulating means and the sheet feeding means. The image forming apparatus according to claim 3, wherein: 5. A single-sided printed sheet on which a first side is image-formed by the image forming unit and conveyed through the sheet reversing unit and a double-sided conveying path, and an unprinted sheet fed by the sheet feeding unit. However, when images are alternately formed by the image forming unit, the conveyance direction switching unit guides the sheet that has passed through the image forming unit to the second conveyance path for the single-sided printing sheet, and performs double-sided printing. 5. The image forming apparatus according to claim 4, wherein a conveyance direction of each sheet is switched so as to guide the sheet to the first conveyance path. 6. The sheet trailing edge regulating means, wherein each sheet on which one side of the image is formed by the image forming means is continuously discharged by the sheet discharging means via the first sheet conveying path. The trailing edge position of the preceding sheet is regulated to one side of the sheet conveying path so that the leading edge position of the succeeding sheet is overlapped with the trailing edge of the preceding sheet at the time of ejection by the sheet ejection means. The image forming apparatus according to claim 3, wherein: 7. A sheet conveying path for connecting the sheet reversing means and the sheet discharging means, wherein the second sheet conveying path is provided for each sheet on which one side of the image is formed by the image forming means. When the image is reversed by the sheet reversing means and continuously discharged by the sheet discharging means via the third sheet conveying path, the sheet trailing edge regulating means is provided from the sheet reversing means. The leading end of the preceding sheet discharged by the sheet discharging means via the third sheet conveying path in the advancing direction of the preceding sheet and the following sheet traveling toward the sheet reversing means via the second sheet conveying path. The image forming apparatus according to any one of claims 3 to 5, wherein a rear end position of the preceding sheet is regulated to one side of the sheet conveying path so that the leading end does not interfere.