JPH1135209A - Image forming device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To continuously form an image on a succeeding sheet and discharge the sheet even when a sheet jam occurs. SOLUTION: A receiving section 51 for receiving a sheet discharged after image formation, a first discharge path 93a for discharging the sheet after image formation toward the receiving section, and a first discharge path are provided. A second paper discharge path 93b for discharging independently,
Switching means 510 for guiding a sheet to one of the first and second discharge paths, and the trailing end of the sheet guided to the first or second discharge path has passed through the entrance of the discharge path. An entrance detecting means 81 for detecting that the paper is jammed, a jam detecting means 82b for detecting that the paper is jammed in the paper ejection path, and the like;
Control means 80 is provided for switching the switching means 510 to the other paper discharge path when the paper jam is detected by the paper jam detecting means and the passage of the trailing edge of the paper is detected by the entrance detecting means 81.

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 for forming and discharging an image on a sheet (a sheet-shaped recording medium (including an envelope)), and forming an image on the sheet mainly using an electrophotographic technique. The present invention relates to an image forming apparatus such as a printer, a facsimile, a copying machine, and the like for discharging. In particular, it relates to the paper discharge path.

[0002]

2. Description of the Related Art Generally, an image forming apparatus includes an image forming unit, a paper supply unit such as a paper supply cassette and a paper supply tray for supplying paper to the image formation unit, and an image forming unit. It has a paper discharge path for discharging the discharged paper, and a receiving unit such as a paper discharge tray for receiving the paper discharged from the paper discharge path.

A transport path (including the above-described paper discharge path) from the paper supply unit to the receiving unit via the image forming unit is formed in the apparatus. In this paper transport path, paper jams occur. May occur.

[0004] Even if a paper jam occurs, if the succeeding paper is still conveyed, there is a possibility that the paper jam may become severe and the apparatus may be damaged. When a paper jam is detected by the detecting means, the operation of the apparatus is stopped and a message to the effect (a warning sound or an operation panel) is sent to the user. Is displayed on a display unit, and the apparatus is operated again after the jammed paper is removed by the user.

On the other hand, in an apparatus capable of forming an image at a high speed, mainly an image forming apparatus using electrophotography, when a paper jam occurs, some succeeding papers are already in the conveyance path. May exist. In such a case, it is not desirable to allow the user to remove a sheet that does not cause a paper jam, since this forces the user to remove the sheet.

To solve such a problem, Japanese Unexamined Patent Publication No. Hei 6-1394 discloses a transport system provided that the paper causing the paper jam is removed and the copy start button is operated. 2. Description of the Related Art There has been proposed a copying machine in which a driving mechanism is operated to discharge a succeeding sheet to a tray.

[0007]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 6-1
The copying machine described in Japanese Patent Publication No. 394 is simply configured to discharge a subsequent sheet to a tray after a sheet causing a paper jam is removed.

That is, this copier, as in the case of a conventional general image forming apparatus, still stops the image forming operation once a paper jam occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which solves the above-mentioned problem and can continuously form an image on a succeeding sheet and discharge the sheet even when a sheet jam occurs.

[0010]

According to another aspect of the present invention, there is provided an image forming apparatus, comprising: a receiving portion for receiving a sheet discharged after an image is formed; A first paper discharge path for discharging the paper after image formation toward the receiving portion, and a second paper discharge path for discharging the paper independently of the first paper discharge path; A switching unit that guides the sheet after image formation to one of the first and second discharge paths; and a trailing end of the sheet guided to the first or second discharge path. Entrance detection means for detecting that the paper has passed through the entrance, jam detection means for detecting that the paper after image formation is jammed in the paper discharge path, paper jam by the jam detection means is detected, and the entrance When the detection means detects the passage of the trailing edge of the paper In, characterized in that and a control means for switching the switching means to the other discharge path side.

[0011]

According to the image forming apparatus of the first aspect, the first paper discharge path for discharging the paper after the image formation is directed to the receiving portion for receiving the paper discharged after the image formation, Independently of the first paper discharge path, a second paper discharge path for discharging the paper after image formation is independent of the first paper discharge path. When the sheet is jammed in the first or second paper discharge path, the paper is guided to the other paper discharge path by the switching means, so that the image forming operation is performed. Can be discharged toward the receiving portion without interrupting the image formation.

The image forming apparatus includes an entrance detecting means for detecting that the trailing end of the sheet guided to the first or second discharge path has passed through the entrance of the discharge path, and an image forming apparatus. Jam detection means for detecting that a succeeding sheet is jammed in the paper discharge path; anda sheet jam detected by the jam detection means, and a passage of the rear end of the sheet detected by the entrance detection means. And control means for switching the switching means to the other paper discharge path side. Therefore, when the paper guided to the first or second paper discharge path is jammed, this is detected by the paper jam detection means, and When the entrance detecting means detects that the trailing edge of the sheet has passed through the entrance of the discharge path, the control means automatically switches the switching means, and the succeeding sheet is switched to the other discharge path. Since guided and is discharged by the can reliably discharge the sheet after subsequent image formation.

Here, suppose that the entrance detecting means is not provided, and therefore, even though the rear end of the sheet has not passed through the entrance of the paper discharge path, the switching means is moved to the other paper discharge path side. If it is possible to switch, the trailing edge of the sheet exists at the entrance of each of the discharge paths (the vicinity of the other discharge path) which is the branch point of the first and second discharge paths. Since the trailing edge may interfere with the leading edge of the succeeding sheet, the succeeding sheet may not always be reliably guided to the other discharge path.

On the other hand, according to the image forming apparatus of the first aspect, when a sheet guided to the first or second sheet discharge path is jammed, the trailing end of the sheet is discharged. When it is detected (or detected) that the paper is passing through the entrance of the paper path, the switching means is switched, so that interference between the trailing edge of the jammed paper and the succeeding paper is prevented. Then, the sheet after the subsequent image formation is surely guided to the other sheet discharge path and discharged.

As described above, according to the image forming apparatus of the first aspect, when a paper jam occurs in the first or second paper discharge path, the switching means is automatically switched. Since the succeeding paper is surely guided to the other paper discharge path and discharged, even if a paper jam occurs, an image can be continuously formed on the subsequent paper and discharged.

[0016]

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

FIG. 1 is an internal structural view showing an embodiment of the image forming apparatus according to the present invention.

The image forming apparatus according to this embodiment is a laser printer capable of forming a full-color image using a developing device using four color toners of yellow, cyan, magenta, and black.

In FIG. 1, reference numeral 50 denotes a case of the apparatus main body.
A, 70B, 70C), the exposure unit 60, the photoconductor unit 100, the developing unit 200, and the intermediate transfer unit 3.
A fixing unit 400, a control unit 80 for controlling the entire apparatus, and the like are provided. A receiving portion 51 that receives a sheet discharged after image formation is formed on the upper surface of the case 50.

The paper supply unit in this image forming apparatus is constituted by the paper feeding device 70 (A, B, C), and the image forming unit is constituted by the exposure unit 60, the photosensitive unit 100, the developing unit 200, and The case 50 includes a sheet transfer path 90 extending from a sheet supply unit to a receiving unit 51 via an image forming unit.

The sheet feeding device 70 (A, B, C) comes into contact with a cassette 71 in which a plurality of sheets S are stored in a stacked state, and the uppermost sheet among the sheets S stored in the cassette 71. The pickup roller 72 feeds the paper, and a pair of separation rollers 74 that surely separates the paper fed by the pickup roller 72 one by one.

The sheet fed by the sheet feeding device 70 is conveyed toward a pair of gate rollers 91b by a pair of conveying rollers 91a of a feeding path 91, which will be described later, of the sheet conveying path 90. Is supplied between the intermediate transfer belt 360 and the secondary transfer roller 380, which will be described later, in the image forming section.

The paper transport path 90 includes three paper feeders 70
A supply path 91 for supplying a sheet from any one of (A, B, C) to the image forming unit, and a movable path for conveying the sheet on which an image has been formed in the image forming unit to the fixing unit 400 92, a discharge path 93 for discharging the sheet on which the image is fixed by the fixing unit 400 toward the receiving unit 51, and a return path 94 for double-sided printing described later.

In the supply path 91, a pair of conveying rollers 91a for conveying the sheet and a pair of gate rollers 91b for regulating the timing of conveying the sheet to the image forming section are arranged.

In the movable path 92, a transport belt 92a for guiding the paper in contact with the lower surface of the paper and applying a transport force to the paper is disposed. This conveyor belt 92a
The length of the sheet to be conveyed in the conveying direction (the length in the left-right direction in FIG. 1) is determined by the nip portion between the backup roller 350 and the secondary transfer roller 380 (described later) of the intermediate transfer unit 300 and the fixing unit 400 When the distance is longer than the distance between the nip portion between the heat roller and the first pressure roller, which will be described later, the paper (for example, plain paper of B5 size or more) is curved at a substantially horizontal position as shown by a solid line. To form a curved path 92b to be conveyed in a state where
As shown by the imaginary line, the sheet (for example, an envelope in a horizontal position) is placed at an inclined position toward the nip portion between the heat roller and the first pressure roller, and
A straight path 92c is formed to convey the sheet linearly toward the nip with the pressure roller.

The paper discharge path 93 is composed of the first and second paper discharge paths 9.
3a and 93b, and at the entrances (lower ends in the figure) of these first and second paper discharge paths 93a and 93b,
A first transport roller unit 95 including two drive rollers 95a and two driven rollers 95b and 95c pressed against and driven on both sides of the drive roller 95a is disposed. Above it, there is arranged a second transport roller section 96 composed of one drive roller 96a and two driven rollers 96b and 96c which are pressed against and driven on both sides thereof, and further above it. A third transport roller unit 97 including one drive roller 97a and two driven rollers 97b and 97c that are pressed against and driven on both sides of the drive roller 97a is disposed. Further, one drive roller 98a and two driven rollers 98b, 9 which are pressed against and driven on both sides of the drive roller 98a are provided at the outlets (upper ends in the drawing) of the first and second discharge paths 93a, 93b.
8c is disposed.

A central guide 9 for separating the first paper discharge path 93a and the second paper discharge path 93b completely from each other to form an independent paper discharge path is provided between the rollers 95 to 97.
9,99,99 are arranged.

The first transport roller section 95 is always driven to rotate in the reverse direction (the direction of the arrow in FIG. 1). However, the second and third transport roller sections 96 and 97 and the discharge roller section 98 are provided. Are configured to be capable of normal rotation and reverse rotation, respectively. The second and third transport roller units 96 and 97 and the driven rollers 96b, 96c and 9 of the discharge roller unit 98
7b, 97c, 98b, 98c are provided with, for example, a separation mechanism for the drive roller, and are configured to be able to release the follow-up to the drive roller.

A switching device 500 is disposed between the first transport roller section 95 and the second transport roller section 96.

The switching device 500 includes, as shown in FIG.
A first switching guide 510 and a second switching guide 520 are provided.

The first switching guide 510 serves as switching means for guiding the sheet after image formation to one of the first and second paper discharge paths 93a and 93b. It is fixed to a shaft 511 disposed between the paper path 93a and the second paper discharge path 93b. An arm 512 is fixed to one end of the shaft 511, and a pin 514 of a solenoid 513 is connected to a tip of the arm 512. Therefore, when the pin 514 is at the position where the pin 514 is moved upward, the first switching guide 510 is at the position shown by the solid line in FIGS. I have. Note that the first switching guide 510 includes a first discharge path 93a and a second discharge path 93.
and b also serves as a guide means for completely separating the sheet b from an independent sheet discharge path.

The second switching guide 520 is fixed to a shaft 521 disposed outside a guide plate 93b1 for guiding one surface of the second paper discharge path 93b. An arm 522 is fixed to one end of the shaft 521, and a pin 524 of a solenoid 523 is connected to a tip of the arm 522. Therefore, when the pin 524 is in the up position, the second switching guide 520 is in the position shown by the solid line in FIGS. 1 and 2, and when the pin 524 is moved down, it rotates clockwise. .

The second switching guide 52 is provided on the guide plate 93b1.
0, a notch 93b2 is provided, and when the second switching guide 520 rotates clockwise, the leading end portion 520a enters the notch 93b2, and the drive roller 95a and the driven roller 95c It is directed to the nip 95n1 (see the phantom line in FIG. 1).

When the first switching guide 510 rotates counterclockwise, its tip 510a enters the notch 93b2 (see the phantom line in FIG. 1).

At the entrances of the first and second paper discharge paths 93a and 93b, entrance detection means 81 for detecting that the trailing end of the sheet guided to these paths has passed through the entrance of the paper discharge path is arranged. Have been. This detecting means 81 is constituted by a photo sensor, and when there is a sheet
N, and if not, it is OFF.

The first and second paper discharge paths 93a, 93
A plurality of photosensors 82a, 83a, 82b, 83b serving as jam detection means for detecting that a sheet has jammed in the paper ejection path are arranged at an appropriate position of b.
In this embodiment, the photo sensor 81 constituting the entrance detecting means also constitutes a part of the clogging detecting means as described later.

These photo sensors 81 and 82
a, 83a, 82b, 83b are connected to a control unit 80 as control means.

The control unit 80 operates the solenoid 513 to activate the first switching guide 510 when the paper jam is detected by the paper jam detecting means and the passage of the trailing edge of the paper is detected by the entrance detecting means 81. In addition to switching to the other sheet discharge path, control of the forward / reverse rotation of the second and third transport roller sections 96 and 97 and the sheet discharge roller section 98 is performed. During double-sided printing, which will be described later, when the passage of the trailing edge of the sheet is detected by the entrance detecting means 81, the solenoid 5
13 and 523 are operated to control the switching between the first switching guide 510 and the second switching guide 520 as described later, and the second and third transport roller sections 96 and 97 are controlled.
In addition, control of forward / reverse rotation drive of the discharge roller unit 98 and the like are performed. The control unit 80 according to the present embodiment has a storage unit that can store at least image data corresponding to 16 pages of A4 size (or Letter size) in a single color.

The return path 94 includes a first discharge path 93a.
And the supply path 91, and a transport roller pair 94a for transporting the paper is disposed. The role of the return path 94 will be described later.

The photoconductor unit 100 includes a photoconductor 110
A charging roller 120 serving as a charging unit for uniformly charging the outer peripheral surface by contacting the outer peripheral surface of the photoconductor 110; and a cleaning unit 130.

The developing unit 200 includes:
Developing unit 210Y for yellow, developing unit 210 for cyan
C, a developing device 210M for magenta and a developing device 210K for black. Each of these developing devices 210Y, 21
0C, 210M, and 210K have yellow, cyan, magenta, and black toners built therein, respectively. Further, the developing rollers 211Y, 211C, 2
11M and 211K, so that only the developing roller of any one of the developing units can contact the photoconductor 110.

The intermediate transfer unit 300 includes the driving roller 3
10, primary transfer roller 320, and wrinkle removing roller 330
, Tension roller 340 and backup roller 3
50, an endless intermediate transfer belt 360 stretched around these rollers, and a cleaning unit 3 that can be brought into contact with and separated from the intermediate transfer belt 360 by the operation of the cam 371.
70.

A secondary transfer roller 380 is arranged opposite to the backup roller 350. The secondary transfer roller 380 is rotatably supported by an arm 382 that is swingably supported by a support shaft 381.
By swinging by the operation of the cam 383, the cam 383 comes into contact with and separates from the intermediate transfer belt 360.

The drive roller 310 has a gear (not shown) fixed to the end thereof. The gear meshes with a gear (not shown) provided at the end of the photosensitive unit 100 so that the drive roller 310 and the photosensitive member 110 are in contact with each other. The intermediate transfer belt 360 is driven to rotate at substantially the same peripheral speed.
It is designed to be driven in circulation at substantially the same peripheral speed as 10.

The peripheral length of the intermediate transfer belt 360 in this embodiment is formed to be longer than the length of the A3 size (or Ledger size) sheet in the vertically placed state. Therefore, A is required for one rotation of the intermediate transfer belt 360.
It is possible to form an image on paper of three sizes (or Ledger size). Therefore, also A4
With respect to a sheet of a size (or a letter size), it is possible to form an image on two sheets of paper by one rotation of the intermediate transfer belt 360.

While the intermediate transfer belt 360 is being driven to circulate, the toner image on the photosensitive member 110 is transferred between the primary transfer roller 320 and the photosensitive member 110 by the intermediate transfer belt 36.
The toner image transferred onto the intermediate transfer belt 360 is transferred to the sheet S supplied between the secondary transfer roller 380 and the toner image.

The sheet S to which the toner image has been transferred is transferred to the fixing unit 400 via the variable path 92.

The fixing unit 400 has a heat roller 410 having a heat source, first and second pressure rollers 420 and 430 pressed against the heat roller 410, and a peeling claw 440.

The sheet S to which the toner image has been transferred is first supplied to a pressure contact portion between the heat roller 410 and the first pressure roller 420, and guided to be wound around the heat roller 410 by a guide (not shown), and is then guided to the second position. Pressure roller 430
The toner on the sheet is fixed on the sheet in the process. After that, the sheet is released
The sheet is separated from the heat roller 410 by 0, and is transported toward the paper discharge path 93.

The operation of the entire image forming apparatus of this embodiment will be described below. The image forming apparatus of this embodiment can form an image on only one side of a sheet (print one side), Since an image can be formed on both sides of a sheet (double-sided printing), first, the case of single-sided printing will be described, and then the case of double-sided printing will be described. In any case, first, the operation when paper jam does not occur (normal time) will be described, and then the operation when paper jam occurs (paper jam) will be described.

<In the case of single-sided printing> (Normal) (i) When a print command signal (image forming signal) from a host computer (personal computer or the like) (not shown) is input to the control unit 80, the photosensitive member 110 is developed. The developing roller of the unit 200 and the intermediate transfer belt 3
60 is driven to rotate.

(Ii) The outer peripheral surface of the photoconductor 110 is uniformly charged by the charging roller 120.

(Iii) The exposure unit 60 selectively exposes the outer peripheral surface of the uniformly charged photoreceptor 110 in accordance with the image information of the first color (for example, yellow). An image is formed.

(Iv) The developing roller 211 of the developing device 210Y for the first color (for example, yellow) is provided on the photosensitive member 110.
Only the Y contacts, the electrostatic latent image is developed, and the toner image of the first color (for example, yellow) is
10 is formed.

(V) The toner image formed on the photoconductor 110 is transferred onto the intermediate transfer belt 360 at the primary transfer section, that is, between the photoconductor 110 and the primary transfer roller 320. At this time, the cleaning unit 370 and the secondary transfer roller 380 are separated from the intermediate transfer belt 360.

(Vi) After the toner remaining on the photosensitive member 110 is removed by the cleaning means 130,
The photosensitive member 110 is activated by static elimination light from static elimination means (not shown).
Is neutralized.

(Vii) The above operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, the fourth color,
Are repeated on the intermediate transfer belt 360 to form a toner image corresponding to the content of the print command signal on the intermediate transfer belt 360.

(Viii) The sheet S is fed from the sheet feeding device 70 (any of 70A, 70B, 70C) at a predetermined timing.
Is supplied via the supply path 91 and the gate roller pair 91b, and immediately before or after the leading end of the sheet S reaches the second transfer portion (that is, the toner image on the intermediate transfer belt 360 is located at a desired position on the sheet S). The secondary transfer roller 380 is pressed against the intermediate transfer belt 360 (at the timing when the image is transferred), and the toner image (basically a full-color image) on the intermediate transfer belt 360 is transferred onto the sheet S. Further, the cleaning unit 370 contacts the intermediate transfer belt 360, and the toner remaining on the intermediate transfer belt 360 after the secondary transfer is removed.

(Ix) The sheet S to which the toner image has been transferred passes through the fixing unit 400 via the variable path 92, so that the toner image is fixed on the sheet S. Is discharged onto the receiving portion 51.

At this time, the first switching guide 510 is at the position shown by the solid line in FIGS. 1 and 2, and the sheet S is discharged through the second discharge path 93b.

The operations (vii) and (viii) are continuously performed as necessary, and the paper after image formation is continuously discharged.

(At the time of paper jam) In the process in which the paper on which the image is formed as described above is continuously discharged through the second paper discharge path 93b, the paper is put into the second paper discharge path 93b. May be clogged.

This paper jam is detected by the photo sensors 81 and 82b and 83b.

As described above, these photo sensors are:
Turns on when there is paper in the opposite part, and turns off when there is no paper
Since it is F, it turns on when the leading edge of the sheet passes through the facing portion, and turns off when the trailing edge passes.

Therefore, when the paper is normally discharged without a paper jam, each of these sensors is turned on and then turned off after a lapse of a predetermined time (the rear end of the paper passes). In the case where the sensor is clogged, at least one of the sensors keeps ON even though the certain time has elapsed.

As a result, the control unit 80 determines that a paper jam has occurred.

When a paper jam occurs, the control unit 80 detects that the photo sensor 81 serving as the entrance detecting means
It is detected whether or not the FF has been performed. If the FF has been turned off, it is determined that the rear end of the sheet has already passed through the entrance of the second discharge path 93b (in this case, the first transport roller unit 95). Then, by operating the solenoid 513, the first switching guide 510 is switched to the other paper discharge path, that is, the first paper discharge path 93a, as shown by the phantom line in FIG. 1, and the separation mechanism is operated. The second and third transport roller portions 9
6, 97 and the driven roller 9 in the discharge roller section 98
The driven rollers 6b, 97b, 98b are released from being driven, and the driven rollers are rotated in reverse.

As a result, the succeeding sheet on which an image has been formed and has passed through the fixing unit 400 is transferred to the first discharge path 93.
a, and is discharged onto the receiving portion 51 via the paper discharge path 93a. At this time, the driven roller 96
Since the driven rollers b, 97b, and 98b are released from being driven, the jammed paper is not fed back.

On the other hand, if the photo sensor 81 is ON when the paper jam occurs, the trailing end of the paper does not pass through the entrance of the second paper discharge path 93b, but exists at the entrance. In this case, the control unit 80 stops the operation of the apparatus, at least the paper transport operation thereof, without switching the first switching guide 510, and the paper is jammed to the user. A message to the effect (alarm or display on the display of the operation panel, etc.) is transmitted, and after the jammed paper is removed by the user, the apparatus is operated again.

<In case of double-sided printing> (Normal operation) The operations (i) to (vii) described above are the same as those in the case of single-sided printing, and therefore the operation after (viii) will be described. Further, as an example, a case where different images are formed on the front and back of three sheets will be described.

(Viii) At a predetermined timing, the first sheet S1 is fed from the sheet feeding device 70 (any of 70A, 70B, 70C) to the supply path 91 and the gate roller pair 91.
b, and the toner image on the intermediate transfer belt 360 is transferred onto the sheet S1 in the same manner as in the case of single-sided printing.

(Ix) Subsequently, at a predetermined timing, the second sheet SS is supplied from the sheet feeding device 70 via the supply path 91 and the gate roller pair 91b, and the toner image on the intermediate transfer belt 360 is supplied to the second sheet SS. Is transferred onto the sheet S2.

At this time, the first switching guide 510 rotates counterclockwise as shown in FIG.
Is on the driven roller 95b side.

Therefore, the first sheet S1 is
To the paper discharge path 93a.

FIG. 3 shows the rear end S1b of the first sheet S1.
Has just passed through the entrance detecting means 81. When the sheet is long, its leading end is moved from the sheet discharging roller 98 to the receiving section 5 as indicated by a virtual line S1'a in FIG.
Protrude above 1.

At this time, the leading end S2a of the second sheet S2 has not yet reached the first transport roller unit 95.

(X) When the entrance detecting means 81 detects the passage of the rear end S1b of the first sheet S1, the first sheet S1
The switching guide 510 is switched to the driven roller 95c side as shown by the imaginary line in FIG. 3 and the solid line in FIG. 4, and the second and third transport roller portions 96, 9 as shown in FIG.
7, and the paper discharge roller 98 rotates in the reverse direction.

Accordingly, the first sheet S1 is the first sheet S1,
The drive rollers 95a, 96a, 97a, 98a of the second and third transport roller units 95, 96, 97 and the discharge roller unit 98 (only when the paper is long; the same applies hereinafter) and the follower of the first discharge path 93a. Rollers 95c, 96c, 97c, 98c
And the second sheet S2 is transported to the return path 94, and the first, second, and third transport roller units 95, 9
6, 97, and the drive roller 95 of the discharge roller unit 98
a, 96a, 97a, 98a and driven rollers 95b, 96b, 97b, 98b on the side of the second paper discharge path 93b carry the paper into the second paper discharge path 93b.

At this time, the third sheet S
3 is fed from the sheet feeding device 70 at a predetermined timing, and its leading end S3a passes through a gate roller pair 91b.

(Xi) Rear end S2b of the second sheet S2
Is detected by the entrance detecting means 81, the second switching guide 520 is switched to the first driven roller 95c side as shown by the imaginary line in FIG.
Third transport roller units 96 and 97 and paper discharge roller unit 98
Rotates forward (rotates in the direction opposite to the direction of the arrow in FIG. 4).

Therefore, the second sheet S2 is the first sheet S2.
Drive rollers 95a, 96a, 97a, 9 of the second and third transport roller units 95, 96, 97 and the discharge roller unit 98.
8a and driven rollers 95b and 96 on the side of the second paper discharge path 93b.
b, 97b and 98b are carried out toward the return route 94.

During this time, since the second switching guide 520 is switched to the first driven roller 95c side as shown by the imaginary line in FIG. 4, the third sheet S3 is moved to the second sheet discharging path. Thus, the sheet feeding timing of the third sheet S3 is delayed. In other words, the interval between the start of feeding the first sheet S1 and the start of feeding the second sheet S2 is compared with the interval between the start of feeding the second sheet S2 and the third sheet. The interval from the start of feeding the sheet S3 is set to be larger.

(Xii) As shown in FIG. 5, when the entrance detecting means 81 detects that the leading end S2a of the second sheet S2 has passed in the return direction, the second switching guide 520
Retreats from the second paper discharge path 93b as shown by the solid line in FIG. 5, and the first switching guide 510 rotates counterclockwise as shown by the phantom line, and switches to the second driven roller 95b side. . In addition, the second and third transport roller units 96 and 9
7, and the paper discharge roller section 98 rotates forward (rotates in the direction of the arrow in FIG. 5).

At this time, the third sheet S3 is in a state where an image is transferred to one side thereof, and the leading end S1a of the first sheet S1 is immediately before the gate roller pair 91b. .

(Xiii) Thereafter, as the respective rollers continue to rotate, the third sheet S3 is carried into the first sheet discharging path 93a as shown in FIG.

At this time, the first sheet S1 is in a state where the image is transferred to the other side, and the second sheet S1
In No. 2, the leading end S2a passes through the gate roller pair 91b.

(XiV) Trailing end S3 of the third sheet S3
When the passage b is detected by the entrance detecting means 81,
As shown by the imaginary line in FIG.
, And the second and third transport rollers 96 and 97 and the paper discharge roller 98 rotate in the reverse direction (rotate in the direction opposite to the direction of the arrow in FIG. 6).

Therefore, the third sheet S3 is the first sheet S3.
Drive rollers 95a, 96a, 97a, 9 of the second and third transport roller units 95, 96, 97 and the discharge roller unit 98.
8a and driven rollers 95c and 96 on the first paper discharge path 93a side
c, 97c, and 98c, and is carried out toward the return path 94, and the first sheet S1 is transferred to the first switching guide 51.
0, it is guided to the second paper discharge path 93b, and the first, second, and third paper
Conveyance roller units 95, 96, 97 and paper discharge roller unit 9
8 drive rollers 95a, 96a, 97a, 98a and the second
Followed rollers 95b, 96b, 97 on the side of the paper discharge path 93b
b and 98b are conveyed through the second paper discharge path 93b and discharged onto the receiving portion 51 of the case 50.

Subsequently, the second sheet S2 and the third sheet S3 are conveyed through the sheet discharging path 93b and discharged onto the receiving portion 51 of the case 50. In the process, The fourth sheet is fed from the sheet feeding device 70 at a predetermined timing, and the above operation is repeated as necessary.

(At the time of paper jam) In the process in which the paper on which the images are formed on both sides as described above is continuously discharged through the second paper discharge path 93b, the paper in the second paper discharge path 93b (For example, the paper S1) may be jammed.

In this case, as in the case of the single-sided printing described above, the control unit 80 detects whether or not the photo sensor 81 serving as the entrance detecting means is off, and turns off the photo sensor 81.
If the rear end of the sheet has already been
And switches the first switching guide 510 to the other discharge path, that is, the first discharge path 93a, as shown by the solid line in FIG. Activate the second and third transport roller units 9
6, 97 and the driven roller 9 in the discharge roller section 98
6b, 97b, and 98b are released from being driven by the driving rollers, and the driving rollers are rotated in the reverse direction (rotated in the direction of the arrow in FIG. 6).

As a result, an image is formed on both sides, and the following paper (for example, paper S
2, S3) is guided to the first paper discharge path 93a, and is discharged onto the receiving portion 51 via this paper discharge path 93a.

In other cases, the control unit 80
Without switching the first switching guide 510, the operation of the apparatus, at least the paper transport operation thereof, is stopped, and a message indicating that the paper is jammed (a warning sound, a display on a display unit of an operation panel, etc.) is issued to the user. Inform, wait for the jammed paper to be removed by the user, and then activate the device again.

According to the above-described image forming apparatus, the image forming apparatus is directed to the receiving section 51 for receiving the sheet discharged after the image formation.
First paper discharge path 93 for discharging paper after image formation
a and a second paper discharge path 93b for discharging the paper after image formation independently of the first paper discharge path 93a.
And the first and second discharge paths 93 after the image formation.
a and 93b, the switching means 510 for guiding the sheet to one of the first and second paper discharge paths. By guiding the sheet, the sheet after the image formation can be discharged to the receiving unit without interrupting the image forming operation.

The image forming apparatus includes an entrance detecting means 81 for detecting that the trailing end of the sheet guided to the first or second discharge path 93a, 93b has passed through the entrance of the discharge path. A paper jam detected by the paper jam detection means 82b for detecting that the paper after image formation is jammed in the paper discharge path, and the like.
And control means 80 for switching the switching means 510 to the other paper discharge path when the entrance detecting means 81 detects the passage of the trailing edge of the paper. When the guided paper is jammed, the jam is detected by the jam detecting means 82b or the like, and when the entrance detecting means 81 detects that the rear end of the paper is passing through the entrance of the paper discharge path. The switching means 510 is automatically switched by the control means 80, and the succeeding sheet is guided to the other sheet ejection path and ejected, so that the sheet after the subsequent image formation is reliably ejected. Can be.

Here, supposing that the entrance detecting means 81 is not provided, the switching means 51 is provided even though the rear end of the sheet does not pass through the entrance of the paper discharge path.
Assuming that 0 may be switched to the other paper discharge path side, it is possible to change the position at the entrance of each paper discharge path which is a branch point of the first and second paper discharge paths (in the vicinity of the other paper discharge path). Since the trailing edge of the sheet exists and the trailing edge may interfere with the leading edge of the succeeding sheet, the succeeding sheet may not always be reliably guided to the other discharge path.

On the other hand, according to the image forming apparatus of this embodiment, when the paper guided to the first or second paper discharge path is jammed, the trailing end of the paper is moved to the paper discharge path. The switching means 510 is switched when it is detected (or when it is detected) that the paper is passing through the entrance of the paper, so that the interference between the trailing edge of the jammed paper and the succeeding paper is prevented. Thus, the sheet after the subsequent image formation is surely guided to the other sheet discharge path and discharged.

As described above, according to the image forming apparatus of this embodiment, when a paper jam occurs in the first or second paper discharge path, the switching means 510 is automatically switched. Since the succeeding paper is surely guided to the other paper discharge path and discharged, even if a paper jam occurs, an image can be continuously formed on the subsequent paper and discharged.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be appropriately modified within the scope of the present invention.

For example, in the above-described embodiment, the discharge path for discharging the sheet at the time of normal one-side printing is the second discharge path 93b. At this time, a succeeding sheet may be guided to the second sheet discharge path 93b.

The entrance detecting means for detecting that the rear end of the sheet has passed through the entrance of the paper discharge path 93 can be constituted by an appropriate means. For example, it may be configured by a photo sensor 82a or 82b serving as a clogging detection unit. That is, if the size of the sheet is known, the passage of the trailing edge of the sheet can be detected based on the elapsed time after the leading edge of the sheet is detected by these photosensors.

It is not always necessary to provide a separation mechanism for separating the driven roller in the paper discharge path from the driving roller. If the jammed paper slips when the drive roller is reversed, no problem occurs.

[0103]

According to the image forming apparatus of the first aspect,
Even when a paper jam occurs, an image can be continuously formed on the succeeding paper and discharged.

[0104]

[Brief description of the drawings]

FIG. 1 is an internal structural diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view mainly showing switching means.

FIG. 3 is an operation explanatory view.

FIG. 4 is an operation explanatory view.

FIG. 5 is an operation explanatory view.

FIG. 6 is an operation explanatory view.

[Explanation of symbols]

 S paper 50 case 51 receiving unit 70 paper feeder 80 control unit 93 paper discharge path 93a first paper discharge path 93b second paper discharge path 99 central guide (guide means) 100 photoconductor unit 110 photoconductor 200 developing unit 300 Intermediate transfer unit 400 Fixing unit 500 Switching device 510 First switching guide (switching means)

Claims (1)

[Claims] A receiving section for receiving a sheet discharged after image formation; a first discharge path for discharging the sheet after image formation toward the receiving section; and a receiving section for receiving the sheet after image formation. One of the first and second paper discharge paths for discharging the paper after image formation toward the copy unit independently of the first paper discharge path and the paper after image formation. Switching means for guiding the paper to the first or second paper discharge path, entrance detecting means for detecting that the rear end of the paper guided to the first or second paper discharge path has passed through the entrance of the paper discharge path, Jam detection means for detecting jamming in the paper ejection path; and when the paper jam is detected by the jam detection means and the passage of the trailing edge of the paper is detected by the entrance detection means, the switching means is switched to the other one. Control means for switching to a paper discharge path side. An image forming apparatus characterized in that: