JP2001249597A - System and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming system and an image forming method by which post-processing is restarted without aborting paper housed in an inter mediate tray even in the case that the post-processing is interrupted. SOLUTION: In the case that paper jamming is caused before the paper P08 is carried to the intermediate tray (timing T14), image forming processing and the post-processing are interrupted. Then, information with respect to the progress state of the post-processing at the point of time of the interruption of the post-processing such as an ejection count value (m) and a stack count value (n) are obtained based on both output signals from a carrying detection sensor and an ejection detection sensor. When adequate switch and button or the like are operated after an operator removes only jammed paper P08 and eliminates an error, the image I03 formed on the paper P08 by receiving it is formed on the paper P08 as a first image after restart and is carried to a finisher 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming system including an image forming apparatus for forming an image on a sheet and a sheet post-processing apparatus for performing post-processing, and an image forming method in the system. . In this specification, after temporarily storing sheets on which an image is formed by an image forming apparatus in an intermediate tray, a sheet bundle including a plurality of sheets stored in the intermediate tray is collectively discharged to a main tray. The processing to be performed is referred to as “post-processing”.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus, an image is formed on a sheet and the sheet is discharged to a standard discharge tray provided in the apparatus. For handling, it has been conventionally proposed to connect a sheet post-processing apparatus to the discharge side of the image forming apparatus or to incorporate the sheet post-processing apparatus in the image forming apparatus.

This paper post-processing apparatus temporarily stores paper discharged from an image forming apparatus in an intermediate tray and then collectively discharges a bundle of paper stored in the intermediate tray to a main tray. . For example, in the case of printing five copies of five A4 size papers, a series of processes in which each image is conveyed to an intermediate tray and temporarily stored while an image is continuously formed on the A4 size paper by the image forming apparatus. By repeating the operation five times, one set of five sheets is temporarily stored in the intermediate tray. Then, when the last sheet, that is, the fifth sheet is conveyed to the intermediate tray, a sheet bundle of five sheets is discharged from the intermediate tray to the main tray. Thus, the processing for the first copy is completed. Subsequently, the second to fifth copies are sequentially discharged to the main tray via the intermediate tray in the same manner as the first copy.

When staple processing is performed on a bundle of sheets constituting each unit, when the last sheet (fifth sheet) is stored in the intermediate tray, the stapling process is performed near the intermediate tray. The stapling process performed by the stapler disposed in the middle is performed on the sheet bundle on the intermediate tray, and then the sheet bundle is discharged from the intermediate tray to the main tray.

[0005]

Incidentally, if a paper jam occurs during the execution of the post-processing, it is necessary to interrupt the image forming processing and the post-processing. In particular, if a paper jam occurs in the paper post-processing device, the paper that failed to be conveyed is removed from the paper post-processing device to eliminate the paper jam, and the paper stored in the intermediate tray is also removed. Then, the paper removed from the intermediate tray was printed again from the beginning. For this reason, even the image-formed sheets already formed in the intermediate tray and having been subjected to image formation are discarded, and the sheets are wasted. Further, since the image formation is performed again from the beginning, the running cost is increased, and the throughput is greatly reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an image forming system capable of resuming post-processing without discarding sheets stored in an intermediate tray even when post-processing is interrupted. And an image forming method.

[0007]

An image forming system according to the present invention comprises: an image forming apparatus for forming an image on a sheet;
After temporarily storing the sheet on which the image is formed by the image forming apparatus in the intermediate tray, a post-processing is performed in which a bundle of sheets including a plurality of sheets stored in the intermediate tray is collectively discharged to the main tray. An image forming system including a sheet post-processing device, wherein the sheet post-processing device includes: a conveyance detection sensor that detects a sheet conveyed to the intermediate tray; And a discharge detection sensor for detecting a bundle of sheets discharged to the main tray. Then, when the post-processing is interrupted by the sheet post-processing apparatus or the image forming apparatus, the progress of the post-processing at the time of post-processing interruption based on both output signals output from the conveyance detection sensor and the discharge detection sensor. On the other hand, in the image forming apparatus, when post-processing is restarted,
Based on the information, the image formation is restarted from the image following the image formed on the sheet lastly stored in the intermediate tray.

In such a configuration, when the post-processing is interrupted, information on the progress of the post-processing at the time when the post-processing is interrupted is obtained based on both output signals from the transport detection sensor and the discharge detection sensor. Then, based on the information, an image subsequent to the image formed on the sheet finally stored in the intermediate tray is determined, and when the post-processing is restarted, the image formation is restarted from this image. Therefore, the image forming process is performed on the next sheet in the form following the sheet stored in the intermediate tray, and the sheet on which the image is formed is conveyed and stored in the intermediate tray.

Here, the "information on the progress of post-processing at the time of post-processing interruption" includes, for example, the following two modes.

First, in a first mode, when post-processing is interrupted in the course of forming a plurality of N (N ≧ 2) sheets, the discharge detection sensor detects the post-processing until the interruption of the processing. Assuming that the count value is m (m ≧ 0) and the count value detected by the conveyance detection sensor after the m-th sheet bundle is n (n ≧ 0), these count values are equal to the above information. Function as Therefore, when the post-processing is restarted, the image forming apparatus ((N
If the image to be formed on the (m) + n + 1) th sheet is formed first, the post-processing can be restarted without discarding the sheet stored in the intermediate tray. In addition,
When a conveyance error occurs in the intermediate tray and the post-processing is interrupted, the sheets in the intermediate tray must be removed. In such a case, when the post-processing is restarted, the image to be formed on the ((N × m) +1) -th sheet may be formed first.

In a second mode, the count value detected by the discharge detection sensor up to the time of post-processing interruption is set to m (m ≧ 0), and the conveyance detection is performed after the m-th discharged sheet bundle. Let the count value detected by the sensor be n
When (n ≧ 0), these count values function as the information. Therefore, when the post-processing is restarted, the image forming apparatus stores the image to be formed on the (n + 1) -th sheet among the sheets constituting the (m + 1) -th sheet bundle first, and stores the image in the intermediate tray. The post-processing can be restarted without discarding the paper sheet. When a post-processing is interrupted due to a conveyance error in the intermediate tray, the sheets in the intermediate tray must be removed. In such a case, when the post-processing is restarted, the image to be formed on the first sheet constituting the (m + 1) -th sheet bundle may be formed first.

Further, the image forming apparatus is provided with an image memory for temporarily storing image data corresponding to an image to be formed on a sheet. In the conventional image forming system, the image data in the image memory is cleared when the sheet is discharged from the image forming apparatus. For this reason, in the image forming system including the sheet post-processing device, when a sheet jam occurs in the sheet post-processing device and the image formation on the sheet is required again, it is necessary to store the image data in the image memory again. This causes a problem that the throughput is reduced. On the other hand, in the present invention, after an image is formed on a sheet based on the image data, the image data is cleared from the image memory at a predetermined timing after the sheet is discharged from the image forming apparatus to the sheet post-processing apparatus. . Therefore,
Even if a paper jam occurs in the paper post-processing device, the image data formed on the paper remains in the image memory in the image memory, so that the image can be formed again quickly and the throughput is reduced. Prevention. The clear timing may be, for example, a point in time when the conveyance detection sensor confirms that the sheet has been conveyed to the intermediate tray or a point in time when the discharge detection sensor has confirmed that the sheet bundle has been discharged to the main tray. it can.

[0013]

FIG. 1 is a diagram showing an example of an image forming system according to the present invention. The image forming system includes an image forming apparatus 1, a finisher 2 disposed adjacent to the image forming apparatus 1, a multi-bin unit 3 disposed above the image forming apparatus 1, and a lower part of the image forming apparatus 1. Optional paper feed cassette 4 placed in position
It is composed of

The image forming apparatus 1 has yellow (Y),
Printing a full-color image on paper by superimposing four color toners of cyan (C), magenta (M), and black (K), or printing a monochrome image on paper using only black (K) toner It is. In the image forming apparatus 1, as shown in FIG. 1, an image carrier unit 12, an exposure unit 13, a transfer unit 14, a fixing unit 15, and a paper supply / discharge unit 16 are provided inside a case 11.

The image carrier unit 12 includes a photosensitive member 121 rotatable in a counterclockwise direction in FIG. 1 and a charging roller as charging means around the photosensitive member 121 along the rotating direction. 122, developing devices 123Y, 123C, 123M, 123K as developing means,
And a cleaning unit 124 are provided. Then, the exposure unit 13 irradiates the outer peripheral surface of the photoconductor 121 charged by the charging roller 122 with a laser beam to form an electrostatic latent image.

The electrostatic latent image thus formed is developed by a developing unit with toner. That is, in this embodiment, as the developing units, a yellow developing unit 123Y, a cyan developing unit 123C, a magenta developing unit 123M, and a black developing unit 123K are arranged in this order.
Are arranged along. These developing devices 123Y, 1
23C, 123M, and 123K are photosensitive members 121, respectively.
The four developing devices 1 are configured so as to be freely movable toward and away from the developing device 1 in accordance with a command from a sub-controller described later in detail.
One of the developing units 23Y, 123M, 123C, and 123B selectively comes into contact with the photoconductor 121 to make the electrostatic latent image on the photoconductor 121 visible.

The toner image developed by the developing unit is transferred to the intermediate transfer belt 1 of the transfer unit 14 in a primary transfer area located between the black developing unit 123K and the cleaning unit 124.
The primary transfer is performed on the reference numeral 41.

The transfer unit 14 includes a plurality of rollers and an intermediate transfer belt 141 stretched over these rollers.
And a secondary transfer roller 142 for secondary-transferring the intermediate toner image transferred to the intermediate transfer belt 141 onto paper. In this embodiment, the intermediate transfer belt 14
It is configured to be able to transfer a toner image of a maximum size of A3 on 1 sheet, 2 sheets of A4 size, or 4 sheets of postcard size.
The sheets can be transferred simultaneously.

When a color image is to be transferred to a sheet, a color image is formed by superimposing toner images of respective colors formed on the photoreceptor 121 on the intermediate transfer belt 141, and the paper supply / discharge unit 16 The paper is taken out from the cassette 162, the manual feed tray 163 or the optional paper feed cassette 4 by the paper feed unit 161, and is conveyed to the secondary transfer area. Then, a color image is secondarily transferred to this sheet to obtain a full-color image. When a monochrome image is to be transferred to a sheet, only a black toner image is formed on the photoreceptor 121 on the intermediate transfer belt 141, and the sheet conveyed to the secondary transfer area in the same manner as in the case of a color image. To obtain a monochrome image.

The paper on which the toner image has been transferred by the transfer unit 14 is supplied to a paper supply unit 16 of a paper supply / discharge unit 16.
1, the toner image is conveyed to a fixing unit 15 disposed downstream of the secondary transfer area along a predetermined paper feed path (two-dot chain line), and the toner image on the conveyed paper is fixed on the paper. Then, the paper is further conveyed to the paper discharge unit 164 along the paper supply path.

This paper discharge section 164 has two paper discharge paths 164.
a, 164b, one discharge path 164a extends from the fixing unit 15 to the standard discharge tray, and the other discharge path 164b is substantially parallel to the discharge path 164a. It extends between the bin unit 3. Three pairs of rollers are provided along these paper discharge paths 164a and 164b, and the fixed paper is discharged toward the standard discharge tray, finisher 2 or multi-bin unit 3, or the other side. The sheet is also conveyed to the re-feed section 165 to form an image.

As shown in FIG. 1, the re-feed section 165 feeds the sheet reversely conveyed from the discharge section 164 as described above along the re-feed path (two-dot chain line). , And is constituted by three pairs of re-feed rollers arranged along the re-feed path. As described above, the sheet conveyed from the sheet discharging unit 164 is returned to the gate roller pair 166 along the re-feeding path, so that the non-image forming surface of the sheet faces the intermediate transfer belt 141 in the sheet feeding unit 161. The image can be secondarily transferred to the surface.

FIG. 2 is a view showing a finisher constituting the image forming system of FIG. This finisher 2
Functions as the "sheet post-processing apparatus" of the present invention, and is configured as follows.

As shown in FIG. 2, the finisher 2 includes an intermediate tray 21 capable of storing a plurality of sheets, and temporarily transports the sheets carried into the finisher 2 from the image forming apparatus 1 by the intermediate tray 21. After that, the paper stored in the intermediate tray 21 is discharged to the main tray 22. Hereafter, Finisher 2
The configuration of each section will be described in more detail with reference to FIG.

On the side surface of the finisher 2, a paper feed port 201 for receiving the paper discharged from the image forming apparatus 1 is provided. In addition, a punch portion 23 for punching a punch hole in a sheet is provided in the vicinity of the sheet feeding port 201, and a carry-in detection sensor S21 for detecting the carry-in of the sheet to the finisher 2 is supplied as described later. It is located immediately downstream of the paper slot 201. Here, as the carry-in detection sensor S21, for example, a reflection type optical sensor can be used. When a sheet is carried into the finisher 2 through the paper feed port 201, the light from the carry-in detection sensor S21 is transmitted by the sheet. Is reflected, and by detecting this, a paper detection signal indicating that the paper is loaded is output from the carry-in detection sensor S21. For example, by detecting a change in the output level of the sheet detection signal, it is possible to detect the leading edge and the trailing edge of the sheet.

The paper conveyed to the finisher 2 is conveyed to the branch claw 202 along the path P1. This branch claw 2
Numeral 02 is swingable, and the paper conveyed along the path P1 is conveyed to the non-sorting tray 24 by being located at the broken line position in the figure, while being positioned at the solid line position in the figure. It is transported to the transport mechanism 25 side.

In the transport mechanism 25, a pair of rollers 251 for further feeding the sheet passing through the branch claw 202 toward the intermediate tray 21 is disposed immediately downstream of the branch claw 202. Further, in the transport mechanism 25, the paper is transferred to the intermediate tray 21.
Two paths are provided in parallel to each other as paths to be guided to the side, that is, a main path Pm and a sub path Ps,
By swinging the branch claw 252 between the two positions, the transport path to the intermediate tray 21 can be selectively switched. That is, the branch claw 252
When the sheet is positioned at the solid line position in FIG. 2, the sheet is conveyed to the intermediate tray 21 via the main path Pm, while when the sheet is positioned at the broken line position in FIG. 2, the sheet is conveyed to the intermediate tray 21 via the sub path Ps. .

The transport mechanism 25 includes four sets of branch rollers 253 (253a, 253a, 253a,
253b, 253c, 253d) and three branch claws 25
4 (254a, 254b, 254c) are arranged. Each of the branch claws 254 swings according to the sheet size, and conveys the sheet to the intermediate tray 21 from any one of the arrows Da, Db, Dc, and Dd. The swing position of each branch claw 254 is set in accordance with the length of the sheet in the transport direction at the time of mode standby immediately after the start of the operation. For example, the direction of arrow Dd for A4 paper and the arrow Da for A3 paper It is carried into the intermediate tray 21 from the direction.

The four branch rollers 253 (253a, 25
3b, 253c and 253d), the driving force of the main motor is directly transmitted to the two branch rollers 253c and 253d on the downstream side, and the rollers are constantly rotated. On the contrary,
The remaining branch rollers 253a and 253b are connected via a clutch that opens and closes in response to a control command from a finisher controller 29, which will be described later. , The sheet that has been waiting on the main path Pm can be conveyed to the intermediate tray 21 together with the sheet conveyed along the sub path Ps.

The intermediate tray 21 is composed of a pair of tray members separated in a direction (width direction X) perpendicular to the paper surface of FIG. 2, and the front side of the pair of tray members (right side in FIG. 2). ) Supports and stores the entire paper surface.
The lower end of the sheet is supported by sheet receivers 261 and 261 of the stapler 26 described below.

The stapler 26 is arranged below the intermediate tray 21 and performs a stapling process on the sheets stored in the intermediate tray 21 as necessary.
As shown in FIG. 3, the stapler 26 includes two paper receivers 261 and 261. The lower end of the paper P conveyed toward the intermediate tray 21 by the conveyance mechanism 25 is locked, and the paper P is It prevents sliding down from the intermediate tray 21. In this embodiment, the stapler body 262 of the stapler 26 is fixedly arranged. And
The intermediate tray 21 is moved by the position adjusting mechanism 27 described below.
After the staple position is determined by shifting the paper P stored in the intermediate tray 21 in the width direction X, the stapler body 262 collectively staples the paper P stored in the intermediate tray 21. Of course, stapler body 2
62 is configured to be movable in the width direction X of the intermediate tray 21,
The stapler body 262 may be configured to collectively stap the sheets P stored in the intermediate tray 21 at a desired position.

Further, a position adjusting mechanism 27 is provided on both sides of the intermediate tray 21. This position adjusting mechanism 27
Is for aligning or shifting the sheets P stored in the intermediate tray 21 in the width direction X, and a pair of joggers 271 and 272 arranged movably in the width direction X on the front side of the intermediate tray 21. And the jogger 271 in the width direction X
First jogger drive control section (see reference numeral 27 in FIG. 5)
3) and a second jogger drive control unit (reference numeral 274 in FIG. 5) that drives the jogger 272 in the width direction X. Therefore, by controlling the amount of movement of the joggers 271 and 272, the sheets P can be aligned in the intermediate tray 21,
The sheet P can be shifted in the width direction X at a time. In addition, since the sheet alignment and the sheet shift in the intermediate tray 21 are known per se in the related art, a detailed description thereof will be omitted.

Further, the finisher 2 is provided with a discharge mechanism 28 for discharging the paper P stored in the intermediate tray 21 to the main tray 22. In the discharge mechanism 28, an endless belt 281 is stretched between the tray members, that is, along a separation portion of the intermediate tray 21 extending in the discharge direction Y. The endless belt 281 is a belt roller 28
2, 282, which run in the discharge direction Y and are fixed to the surface of the endless belt 281.
Move 3 As shown in FIG. 3, the paper receiver 283 is configured to store the paper
61, and moves in the discharge direction Y to replace the sheet trays 261 and 261.
After supporting the lower end portion of the paper P stored in the main tray 22, the paper P is further moved from the intermediate tray 21 to the main tray 22 side. A discharge roller pair 284 is provided on the main tray side (upper side in FIG. 2) of the intermediate tray 21 to reliably discharge the sheet P carried out from the intermediate tray 21 to the main tray 22.

In the finisher 2 configured as described above, in addition to the carry-in detection sensor S21 for detecting the sheet P, a conveyance detection sensor S22 for detecting sheet conveyance to the intermediate tray 21, and an intermediate tray 21 A storage detection sensor S23 for detecting the paper stored in the inside and a discharge detection sensor S24 for detecting the discharge of the bundle of paper stored in the intermediate tray 21 to the main tray 22 are provided.

Here, as the transport detection sensor S22, for example, a combination of a rotating member that rotates in conjunction with the transported paper and a photo interrupter can be used. If a plurality of through-holes are provided in the rotating member at equal angular intervals, the rotating member rotates in conjunction with sheet conveyance, and the number of through-holes corresponding to the rotation amount passes through the photo interrupter. As a result, a pulse-like signal is output from the photo-interrupter, whereby the intermediate tray 2
1 can be detected. Moreover, if the pulse number is out of the predetermined range, the intermediate tray 2
It can also be confirmed that the paper is conveyed to the intermediate tray 21 in an incomplete form and that a paper jam has occurred in the intermediate tray 21.

FIG. 4 is a diagram showing an electrical configuration of the image forming system of FIG. In this image forming system, a main controller 17 and a sub-controller 18 are provided in the image forming apparatus 1 as shown in FIG. The main controller 17 includes a CPU, an image memory, a communication interface, and the like, and receives an image formation command (a signal indicating the content of a print request) from the host computer 5 to send an operation instruction to each unit of the image forming apparatus 1. Converts to job data (print information) in a suitable format,
This is given to the sub-controller 18. The sub-controller 18 receiving the information includes a CPU, a ROM, a RAM, a communication interface, and the like, and controls each unit of the image forming apparatus 1 according to the job data (print information). The configuration of the main controller 17 and the sub-controller 18 will be described later in detail.

In response to this, the sub-controller 18 gives a control signal such as a discharge request to be described later to the finisher controller 29 through serial communication,
By providing various control signals to the multi-bin unit controller 31 and various control signals to the optional paper cassette controller 41, the finisher 2, the multi-bin unit 3 and the optional paper cassette 4 are controlled. The printing process corresponding to the image forming command is executed.

FIG. 5 is a diagram showing an electrical configuration of a finisher controller provided in the finisher main body for controlling the finisher shown in FIG. The finisher controller 29 is configured such that various information is provided to the CPU 290 from the sub-controller 18 of the image forming apparatus 1 via the communication interface 294 together with detection signals from the sensor groups S21 to S24 provided in the finisher 2. I have. The CPU 290 controls each part of the finisher according to a program stored in advance in the ROM 292 based on these signals and information.

The following control units are electrically connected to the CPU 290 to control each unit of the finisher 2.

(A) Punch drive control section 231: punch section 2
3 is driven to form a punch hole in the sheet.

(B) Main-sub path switching control section 256:
The branch pawl 252 is driven to swing to switch the paper transport path between the main path Pm and the sub path Ps.

(C) Conveyance path switching control section 257: branch roller 253 (253a, 253b, 25
3c, 253d) and branch claws 254 (254a, 25
4b, 254c) to drive the paper to the arrows Da, D
The sheet is conveyed to the intermediate tray 21 from one of the directions b, Dc, and Dd.

(D) First jogger drive control section 273: The jogger 271 is driven in the width direction X.

(E) Second jogger drive control section 274: drives the jogger 272 in the width direction X.

(F) Stapler drive controller 263: Moves and positions the stapler body 262 in the width direction X, and staples the sheets P stored in the intermediate tray 21 at a desired position.

(G) Main motor drive control section 291: Drive control of a main motor (not shown) which is a drive source of each section of the finisher 2.

(H) Main tray drive controller 221: The main tray 22, which is movable in the vertical direction, is moved up and down in accordance with the amount of discharged paper.

Further, the AC power supplied through the AC input unit 296 is changed to a DC voltage of a predetermined voltage by the power supply unit 295, and the finisher controller 29 is supplied to the finisher controller 29.
Power source within. In particular, in this embodiment, the power supply unit 29 is controlled based on a relay control signal from the image forming apparatus 1.
The power supply from the AC input unit 296 can be remotely controlled by the image forming apparatus 1 by controlling the conduction / non-conduction of the AC relay 295a provided in the image forming apparatus 5.

Reference numeral 293 in the figure denotes control data for controlling each part of the finisher 2 and the CPU 2.
90 for temporarily storing the operation result and the like at 90
AM.

FIG. 6 is a block diagram showing an electrical configuration of the main controller and the sub-controller. In the main controller 17, the communication interface 1
The CPU 172 is capable of communicating with the host computer 5 via the hard disk controller 173 and the image forming command (signal indicating the content of the print request) given from the host computer 5 via the hard disk controller 173.
74 is written. In this embodiment, the hard disk 174 has a memory capacity for storing five image data, for example, as described later.

The CPU 172 is connected to the image developing section 17.
2a, expands data (vector data or raster data) included in the image formation command given from the host computer 5 or the image formation command read from the hard disk 174 into image data, and outputs the image data via the memory controller 175. Writing to a memory, for example, a semiconductor memory 176. In this embodiment,
The image memory 176 has a memory capacity for storing, for example, three pieces of image data as described later.

The CPU 172 also functions as a job data creation unit 172b, converts an image formation command into job data (print information) in a format suitable for an operation instruction of each unit of the image forming apparatus 1, and provides the job data to the sub-controller 18. .

Further, the CPU 172 obtains the data clear timing based on the information (information relating to the progress of the post-processing) given from the sub-controller 18 as described later, and gives a clear command to the hard disk controller 173 as necessary. The image forming command written in 174 is cleared, or the instruction is given to the memory controller 175 to clear the image data stored in the image memory 176.

On the other hand, the CPU 181 provided in the sub controller 18 controls each part of the image forming apparatus 1 according to the job data (print information) given from the main controller 17 as described above. CPU1
81 is capable of communicating with the finisher controller 29 via the communication interface 182, and outputs from the finisher controller 29 an intermediate tray conveyance signal detected by the conveyance detection sensor S22 and a discharge detection sensor S
The main tray discharge signal detected by 24 and the detection result by other sensors are received. The CPU 181 determines the post-processing status based on these signals. That is, the CPU 181 controls the post-processing status determination unit 1
It functions as 81a, obtains the following information, and gives it to the CPU 172 of the main controller 17.

(I) From intermediate tray 21 to main tray 22
(M: discharge count value) of paper bundles discharged to (ii)
The number of sheets conveyed to the intermediate tray 21 and stacked (n: stack count value); (iii) the finisher 2
And (iv) a signal indicating a position where a paper jam has occurred.

When the post-processing is restarted based on the information (i) and (ii), that is, the information on the progress of the post-processing at the time of the post-processing interruption, the CPU 181 stores the information in the intermediate tray based on the information. Image formation is restarted from the image following the image formed on the last sheet stored.

Next, the operation of the image forming system configured as described above will be described in detail with reference to two specific examples.

FIG. 7 is a schematic diagram showing a first specific example of the image forming system according to the present invention. In the first specific example, an image forming instruction to form two copies of N (N = 5) sheets is given from the host computer 5. When no paper jam occurs in the finisher 2 (no error: FIG. 8), and when a paper jam occurs before the image-formed paper is conveyed to the intermediate tray 21 (error type 1: 9) and the intermediate tray 2
1 will be described separately when a paper jam occurs (error type 2: FIG. 10).

<No Error: FIG. 8> FIG. 8 is a schematic diagram for explaining the operation of the image forming system when no paper jam occurs in the finisher. FIG. (And later FIGS. 9, 10, 12 to 14)
In the column of “hard disk (for 5 sheets)”, an image forming command stored in the hard disk 174 is shown. The column of “image memory (for three images)” shows image data stored in the image memory (semiconductor memory) 176. The symbol "X" attached to these columns means that the stored data has been cleared.

The “paper” column shows the paper that is conveyed to the finisher 2 after an image is formed by the image forming apparatus 1, and each paper is conveyed and stored in the intermediate tray 21 of the finisher 2. Each time the stack count value is incremented by one, the discharge count value is incremented by one each time the sheet bundle stored in the intermediate tray 21 is discharged to the main tray 22.

In the first specific example, when an image forming command to form two copies of N (N = 5) sheets is given from the host computer 5, the image forming processing and post-processing are performed as follows. Execute. First, the main controller 1
7 sequentially writes the first to fifth image forming commands C01 to C05 on the hard disk 174 and sequentially develops the first to third image forming commands into image data I01 to I03,
The respective image data I01 to I03 are stored in the image memory 176.

At an appropriate timing, the first image data I01 is read from the image memory 176, and job data for forming the first image on paper is created, and the job data is supplied to the sub-controller 18. . Upon receiving the job data, the sub-controller 18 controls each unit of the apparatus to form an image I01 on the sheet P01, and
To be discharged. At this stage, the number of sheets stored in the intermediate tray 21 is zero, the stack count value is zero, the number of sheets in the main tray 22 is also zero, and the discharge count value is zero.

When the sheet P01 conveyed to the finisher 2 is conveyed to the intermediate tray 21, the sheet P01 is detected by the conveyance detection sensor S22 and a detection signal is output. Then, based on this detection signal, the stack count value changes from "0" to "1" (timing T11). At the same time, the CPU 172 of the main controller 17 clears the image data I01 stored in the image memory 176, develops the fourth image data I04, and stores it in the image memory.

When the same processing as the first sheet is repeated and the second to fifth sheets P02 to P05 are conveyed to the intermediate tray 21, the sheet bundle B1 stored in the intermediate tray 21
(P01 to P05) are stapled as required, and then discharged to the main tray 22. At this time, the discharge detection sensor S24 detects the discharge of the sheet bundle B1, and outputs a detection signal. The discharge count value changes from "0" to "1" based on this detection signal (at timing T1).
2). Here, the stack count value is once cleared to zero with the discharge of the sheet bundle B1, but the sheet P06 on which the image I01 is formed is conveyed to the intermediate tray 21 and the stack count value becomes "1".

After the first sheet bundle B1 is discharged to the main tray 22 in this manner, the sheet P
06 to P10 are sequentially conveyed and stored in the intermediate tray 21,
After the sheet P10 is conveyed to the intermediate tray 21, the sheet bundle B2 (P06 to P10) stored in the intermediate tray 21 is subjected to staple processing as necessary, and is discharged to the main tray 22. At this time, the discharge detection sensor S24 detects the discharge of the sheet bundle B2 and outputs a detection signal. Then, based on this detection signal, the discharge count value changes from "1" to "2", and the stack count value is cleared to zero (timing T13). In addition, since the image forming command from the host computer 5 is completed, in this embodiment, the hard disk 174 is provided at the same timing T13.
Are cleared.

<In case of error type 1: FIG. 9> FIG.
FIG. 9 is a schematic diagram for explaining the operation of the image forming system when a paper jam occurs before a sheet on which an image is formed is conveyed to an intermediate tray. Here, the description will be made on the assumption that the third sheet of the second copy (the eighth sheet from the start of processing) P08 has caused a conveyance error and a sheet jam has occurred. The operation of the second copy up to the second copy is the same as that of the no error (FIG. 8), and thus the description is omitted here.

If a paper jam occurs before the paper P08 is conveyed to the intermediate tray (timing T14), the paper jam is detected and the image forming system interrupts the image forming process and the post-processing. In this embodiment, when the post-processing is interrupted, information on the progress of the post-processing at the time when the post-processing is interrupted is obtained based on both output signals from the transport detection sensor S22 and the discharge detection sensor S24. Here, the discharge count value (m) and the stack count value (n) are used as the information. That is, the number of sheets discharged to the main tray 22 is obtained from the discharge count value m, and the number of sheets currently stored in the intermediate tray 21 is obtained from the stack count value n. (N × m) + n = (5 × 1) + 2 = It has been confirmed that the post-processing has been executed for up to the seventh sheet.

When the operator removes only the jammed paper P08 and eliminates the error and operates an appropriate switch or button, the image forming system receives the request and resumes the image forming process and the post-process (timing). T1
Five). In this embodiment, the image I03 to be formed on the (N × m) + n + 1 = (5 × 1) + 2 + 1 = 8th sheet is read out from the image memory 176 at the beginning of resumption, and this image I03 is formed on the sheet P08 and the finisher 2 Transported to In this way, the image forming process is performed on the next sheet P08 following the last sheet P07 stored in the intermediate tray 21 at the time of post-processing interruption, and the sheet is conveyed and stored in the intermediate tray 21 continuously. Image formation processing and post-processing can be continuously performed.
As a result, even if the post-processing is interrupted,
Without discarding the sheets P06 and P07 stored in
Post-processing can be restarted, and waste of paper, an increase in running cost, and a decrease in throughput can be prevented.

After the image forming processing and the post-processing are restarted, the processing is executed in the same manner as in the case of no error (FIG. 8), and therefore the description thereof is omitted here.

<In the case of error type 2: FIG. 10>
FIG. 9 is a schematic diagram for explaining the operation of the image forming system when a paper jam occurs in the intermediate tray.
Here, a description will be given on the assumption that a paper jam has occurred in the intermediate tray 21 when the third sheet P08 of the second copy (the eighth sheet from the start of processing) is conveyed to the intermediate tray 21. The operation of the second copy up to the second copy is the same as that of the no error (FIG. 8), and thus the description is omitted here.

When a paper jam occurs in the intermediate tray 21 as described above, the paper jam is detected, and the image forming system interrupts the image forming processing and the post-processing (timing T16). In this embodiment, when the post-processing is interrupted, information on the progress of the post-processing at the time when the post-processing is interrupted is obtained based on both output signals from the transport detection sensor S22 and the discharge detection sensor S24. Here, the discharge count value (m) and the stack count value (n) are used as the information. That is, the number of sheet bundles discharged to the main tray 22 is obtained from the discharge count value m. That is, in this specific example, it is confirmed that the post-processing has been executed for the (N × m) = (5 × 1) = up to the fifth sheet.

After the operator eliminates all the sheets P06 to P08 in the intermediate tray 21 and eliminates the error,
When an appropriate switch or button is operated, the image forming system receives the operation and restarts the image forming process and the post-process (timing T17). In this embodiment, the image I01 to be formed on the (N × m) + 1 = 5 × 1 + 1 = 6th sheet at the beginning of resumption is formed on the sheet P06 and is conveyed to the finisher 2. More specifically, first, after the image data in the image memory 176 is once cleared, the image forming command C01 stored in the hard disk 174 is cleared.
.. C05 are sequentially read out, the image is expanded, and the
To memorize. Then, the image data I01 is stored in the image memory 1
76, job data for forming the sixth image I01 on the sheet is created, and the job data is given to the sub-controller 18 to form the image I01 on the sheet P06 and discharged to the finisher 2. In this way, the image forming process is performed on the next sheet bundle B2 following the sheet bundle B1, and the image forming process and the post-processing can be performed continuously and continuously after the sheet bundle B1.

FIG. 11 is a schematic diagram showing a second specific example of the image forming system according to the present invention. In the second specific example, two image forming commands are linked to a job, and an image forming command for three sheets as one set and an image forming command for two sheets as one set are successively performed. It is provided from the host computer 5. When no paper jam has occurred in the finisher 2 (no error: FIG. 12), the paper on which the image has been formed is transferred to the intermediate tray 2.
The case where the paper jam occurs before the sheet is conveyed to the intermediate tray 1 (error type 1: FIG. 13) and the case where the paper jam occurs in the intermediate tray 21 (error type 2: FIG. 14) will be described separately.

<No Error: FIG. 12> FIG.
FIG. 7 is a schematic diagram for explaining the operation of the image forming system when no paper jam occurs in the finisher. In the second specific example, the host computer 5 continuously gives an image forming command to set one sheet of three sheets (sheet bundle B1) and one sheet of two sheets (sheet bundle B2). Then, the image forming process and the post-process are executed as follows. First, the main controller 17 sequentially writes image forming commands C11 to C13 for forming the first sheet bundle B1 and image forming commands C21 and C22 for forming the next sheet bundle B2 on the hard disk 174, and outputs the first to third sheets. The image data I11 to I13 are stored in the image memory 176 while sequentially developing the image formation command of the above into image data I11 to I13.

At an appropriate timing, the first image data I11 is read out from the image memory 176 to create job data for forming the first image on paper, and then the job data is given to the sub controller 18. . Upon receiving this job data, the sub-controller 18 controls each unit of the apparatus to form an image I11 on the sheet P11,
To be discharged. At this stage, the number of sheets stored in the intermediate tray 21 is zero, the stack count value is zero, the number of sheets in the main tray 22 is also zero, and the discharge count value is zero.

When the sheet P11 conveyed to the finisher 2 is conveyed to the intermediate tray 21, the sheet P11 is detected by the conveyance detection sensor S22 and a detection signal is output. Then, based on this detection signal, the stack count value changes from "0" to "1" (timing T21). At the same time, the CPU 172 of the main controller 17 clears the image data I01 stored in the image memory 176, develops the first image data I21 constituting the next sheet bundle B2, and stores it in the image memory 176.

When the same processing as that for the first sheet is repeated and the second and third sheets P12 and P13 are conveyed to the intermediate tray 21, the sheet bundle B1 stored in the intermediate tray 21
(P11 to P13) are stapled as required, and then discharged to the main tray 22. At this time, the discharge detection sensor S24 detects the discharge of the sheet bundle B1, and outputs a detection signal. Then, based on this detection signal, the discharge count value changes from "0" to "1" (timing T2
2). Here, the stack count value is once cleared to zero with the discharge of the sheet bundle B1, but the sheet P21 on which the image I21 is formed is conveyed to the intermediate tray 21 and the stack count value becomes "1". Also, the host computer 5
In this embodiment, the image forming commands C11 to C13 for the sheet bundle B1 stored in the hard disk 174 are cleared at the same timing T22.

When the image forming command for the first sheet bundle B1 is completed, the sheets P21 and P22 are processed in the same manner as described above.
Are sequentially conveyed and stored in the intermediate tray 21, and the paper P10
Is transported to the intermediate tray 21 and then the intermediate tray 21
The sheet bundle B2 (P21 and P22) stored in the main tray 2 is stapled as necessary.
Discharge to 2. At this time, the discharge detection sensor S24 detects the discharge of the sheet bundle B2 and outputs a detection signal. Then, based on this detection signal, the discharge count value changes from "1" to "2", and the stack count value is cleared to zero (timing T23). Further, since the image forming command for the sheet bundle B2 from the host computer 5 is completed, in this embodiment, the image forming commands C21 and C22 for the sheet bundle B2 stored in the hard disk 174 are cleared at the same timing T23.

<In the case of error type 1: FIG. 13>
FIG. 5 is a schematic diagram for explaining the operation of the image forming system when a paper jam occurs before a sheet on which an image is formed is conveyed to an intermediate tray. Here, the description will be made assuming that the second sheet P22 constituting the second sheet bundle B2 has caused a conveyance error and a sheet jam has occurred. In addition,
The operation up to the first sheet of the sheet bundle B2 has no error (FIG. 1).
Since it is the same as 2), the description is omitted here.

If a paper jam occurs before the paper P22 is conveyed to the intermediate tray 21 (timing T24), the paper jam is detected, and the image forming system interrupts the image forming processing and the post-processing. In this embodiment, when the post-processing is interrupted, information on the progress of the post-processing at the time when the post-processing is interrupted is obtained based on both output signals from the transport detection sensor S22 and the discharge detection sensor S24.
Here, the discharge count value (m) and the stack count value (n) are used as the information. That is, the number of sheets discharged to the main tray 22 is obtained from the discharge count value m, and the number of sheets currently stored in the intermediate tray 21 is obtained from the stack count value n. Second sheet bundle B2
It has been confirmed that the post-processing has been performed for the first sheet of paper.

When the operator removes only the jammed paper P22 and eliminates the error and operates an appropriate switch or button, the image forming system receives the request and resumes the image forming process and the post-process (timing). T2
Five). In this embodiment, the second sheet bundle B2
Further, the image I22 to be formed on the second sheet is read from the image memory 176, and the image I22 is formed on the sheet P22 and is conveyed to the finisher 2. By doing this,
At the time of post-processing interruption, the image forming process is performed on the next sheet P22 following the last sheet P21 stored in the intermediate tray 21, and is conveyed and stored in the intermediate tray 21. Processing and post-processing can be performed. As a result, if post-processing is interrupted,
Post-processing can be restarted without discarding the sheet P21 stored in the intermediate tray 21, and waste of the sheet, increase in running cost, and decrease in throughput can be prevented.

After the image forming processing and the post-processing are restarted, the processing is executed in the same manner as in the case of no error (FIG. 12), and the description thereof is omitted here.

<In case of error type 2: FIG. 14> FIG.
FIG. 9 is a schematic diagram for explaining the operation of the image forming system when a paper jam occurs in the intermediate tray.
Here, when the second sheet P22 constituting the second sheet bundle B2 is conveyed to the intermediate tray 21,
In the following description, it is assumed that a paper jam has occurred. In addition,
The operation up to the first sheet of the sheet bundle B2 has no error (FIG. 1).
Since it is the same as 2), the description is omitted here.

When a paper jam occurs in the intermediate tray 21 as described above, the paper jam is detected, and the image forming system interrupts the image forming processing and the post-processing (timing T26). In this embodiment, when the post-processing is interrupted, information on the progress of the post-processing at the time when the post-processing is interrupted is obtained based on both output signals from the transport detection sensor S22 and the discharge detection sensor S24. Here, the discharge count value (m) and the stack count value (n) are used as the information. That is, the number of sheet bundles discharged to the main tray 22 is obtained from the discharge count value m. Here, since m = 1, it is confirmed that the post-processing is executed for the sheet bundle B1.

After the operator eliminates all the sheets P21 and P22 in the intermediate tray 21 and eliminates the error,
When an appropriate switch or button is operated, the image forming system receives the operation and restarts the image forming process and the post-process (timing T27). In this embodiment, an image I21 to be formed on the first sheet of the second sheet bundle B2 at the beginning of the restart
Is formed on a sheet P21 and is conveyed to the finisher 2.
In this way, the image forming process is performed on the next sheet bundle B2 following the sheet bundle B1, and the image forming process and the post-processing can be performed continuously and continuously after the sheet bundle B1.

As described above, according to this embodiment, when the post-processing is interrupted, the discharge count value (m) and the stack count value (n) are used as information on the progress of the post-processing at the time when the post-processing is interrupted. Based on these information, the image following the image formed on the sheet lastly stored in the intermediate tray 21 is determined. Then, when the post-processing is resumed, since the image formation is resumed from this image, the image forming process is performed on the next sheet in the form following the sheet stored in the intermediate tray, and the image-formed sheet Is conveyed and stored in the intermediate tray. Therefore, even when the post-processing is interrupted, the post-processing can be restarted without discarding the sheets stored in the intermediate tray 21, thereby preventing waste of sheets, increase in running cost, and decrease in throughput. be able to.

In this embodiment, after an image is formed on a sheet based on the image data, the sheet is discharged from the image forming apparatus 1 to the finisher (sheet post-processing apparatus) 2, and The image data is cleared from the image memory at the time of being conveyed. Therefore, the following operation and effect can be obtained. That is, in the conventional image forming system, the image data in the image memory is cleared when the sheet is discharged from the image forming apparatus.
If a paper jam occurs in the finisher and image formation on the paper is required again, it is necessary to store the image data in the image memory again, which causes a problem that the throughput is reduced. On the other hand, in this embodiment, since the image data is cleared at the time when the image data is conveyed to the intermediate tray 21, even if a paper jam occurs in the finisher 2, the image data remaining in the image memory 176 is used. Thus, image formation can be quickly performed again. As a result, a decrease in throughput can be effectively prevented.

In this embodiment, the intermediate tray 21
Although the image data formed on the sheet is cleared on condition that the sheet is conveyed and stored in the finisher, the clear timing is not limited to this. The image data may be cleared at an appropriate position, for example, when the image data is located on the main tray 22.

The present invention is not limited to the above-described embodiment, and various changes other than those described above can be made without departing from the gist of the present invention. For example, in the above embodiment, the case where the paper jam occurs in the finisher 2 is described. However, the paper jam occurs in the image forming apparatus 1 and the finisher 2
When the post-processing is interrupted, the same configuration as described above enables the post-processing to be resumed without discarding the sheets stored in the intermediate tray even when the post-processing is interrupted.

In the above-described embodiment, the paper jam is described as an example of the post-processing interruption. However, the case where the post-processing is interrupted for other reasons is the same as the case of the paper jam.

In the above embodiment, the capacities of the hard disk 174 and the image memory 176 are each “5”.
Although “the number of sheets” and “three sheets” are used, each capacity is not limited to this, and can be appropriately changed according to the operation specifications of the image forming apparatus.

In the above embodiment, the image forming apparatus 1
-Side discharge count value (m) and stack count value (n)
May be obtained by the controller 29 of the finisher (sheet post-processing device) 2 and transmitted to the image forming apparatus 1 by serial communication.

In the above embodiment, the finisher 2
Has two transport paths (main path Pm and sub path Ps), but the present invention can be applied to a finisher having only one transport path.

In the above embodiment, the image forming apparatus 1
Although the image forming system in which the image forming apparatus 1 is connected to the finisher 2 has been described, the present invention can also be applied to an image forming system in which the finisher is incorporated in the image forming apparatus 1, and the same as the above embodiment by applying the present invention. The operation and effect of the invention can be obtained. In this image forming system,
The image forming system may be configured to be controlled by a sub-controller without providing a finisher controller.

In the above embodiment, the toner image on the photosensitive member 121 is transferred to the intermediate transfer belt 141.
The present invention is also applied to an image forming apparatus that transfers a toner image to a transfer medium other than the intermediate transfer belt (transfer drum, transfer belt, transfer sheet, intermediate transfer drum, intermediate transfer sheet, reflective recording sheet, transparent storage sheet, etc.). Can be applied. In addition, the present invention can be applied to an image forming apparatus employing a so-called tandem method as an image forming method. Although the image forming apparatus 1 is a printer, the image forming apparatus includes all image forming apparatuses such as a copying machine and a facsimile machine. Further, the present invention can be applied to an image forming apparatus that forms an image by an image forming method other than the electrophotographic method, for example, an ink jet method or a thermal transfer method.

[0096]

As described above, according to the present invention, when the post-processing is interrupted, the information on the progress of the post-processing at the time when the post-processing is interrupted is output to both output signals from the transport detection sensor and the discharge detection sensor. Based on the information, an image subsequent to the image formed on the last sheet stored in the intermediate tray is determined, and when post-processing is restarted, image formation is restarted from this image. Therefore, the image forming process can be performed on the next sheet in the form following the sheet stored in the intermediate tray, and the sheet on which the image has been formed can be transported and stored in the intermediate tray. As a result, even when the post-processing is interrupted, the post-processing can be restarted without discarding the sheets stored in the intermediate tray, thereby preventing waste of sheets, increase in running cost, and decrease in throughput. be able to.

According to the invention, after an image is formed on a sheet based on the image data, the image data is cleared from the image memory at a predetermined timing after the sheet is discharged from the image forming apparatus to the sheet post-processing apparatus. Therefore, even if a paper jam occurs in the paper post-processing apparatus, the image data formed on the paper remains in the image memory in the image memory, and the image can be formed again quickly.
A decrease in throughput can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an image forming system according to the present invention.

FIG. 2 is a diagram illustrating a finisher included in the image forming system of FIG. 1;

FIG. 3 is a perspective view showing a position adjusting mechanism and a stapler provided in the finisher of FIG. 2;

FIG. 4 is a diagram illustrating an electrical configuration of the image forming system of FIG. 1;

FIG. 5 is a diagram showing an electrical configuration of a finisher controller.

FIG. 6 is a block diagram showing an electrical configuration of a main controller and a sub-controller.

FIG. 7 is a schematic diagram showing a first specific example of the image forming system according to the present invention.

FIG. 8 is a schematic diagram for explaining the operation of the image forming system when no paper jam occurs in the finisher.

FIG. 9 is a schematic diagram for explaining the operation of the image forming system when a paper jam occurs before the paper on which an image is formed is conveyed to an intermediate tray.

FIG. 10 is a schematic diagram illustrating the operation of the image forming system when a paper jam occurs in an intermediate tray.

FIG. 11 is a schematic diagram showing a second specific example of the image forming system according to the present invention.

FIG. 12 is a schematic diagram for explaining the operation of the image forming system when no paper jam occurs in the finisher.

FIG. 13 is a schematic diagram illustrating the operation of the image forming system when a sheet jam occurs before the sheet on which an image is formed is conveyed to an intermediate tray.

FIG. 14 is a schematic diagram for explaining the operation of the image forming system when a paper jam occurs in the intermediate tray.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Finisher (paper post-processing apparatus) 5 ... Host computer 17 ... Main controller 18 ... Sub-controller 21 ... Intermediate tray 22 ... Main tray 29 ... Finisher controller 172, 181, 290 ... CPU 172a ... Image development part 172b ... Job data creation unit 173 ... Hard disk controller 174 ... Hard disk 175 ... Memory controller 176 ... Image memory (semiconductor memory) 181a ... Post-processing status judgment unit B1, B2 ... Paper bundle C01-C05, C11-C13, C21, C22 ... Image forming command I01-I05, I11-I13, I21, I22 ... Image data (image) P01-P10, P11-P13, P21, P22 ... Paper S22 ... Transportation detection sensor S24 ... Ejection detection sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/00 534 G03G 21/00 372 9A001 F term (Reference) 2C061 AP03 AP04 AQ06 AR01 HJ04 HK17 HV09 HV56 2H027 DA31 DA41 DC07 DC14 ED16 ED29 EF09 EK01 EK04 EK17 FD08 ZA07 2H072 AA01 AA17 AA22 AB17 BB08 FB06 GA08 3F048 AA01 AB01 BA02 BA05 BB04 BB05 BD07 CB03 CC01 CC17 DA09 EA15 EB40 3F054 AA01 AB01 AC01

Claims (10)

[Claims] An image forming apparatus for forming an image on a sheet,
After temporarily storing the sheet on which the image is formed by the image forming apparatus in the intermediate tray, a post-processing is performed in which a bundle of sheets including a plurality of sheets stored in the intermediate tray is collectively discharged to the main tray. An image forming system including a sheet post-processing device, a sheet detection device configured to detect a sheet conveyed to the intermediate tray, and a sheet bundle discharged from the intermediate tray to the main tray. The sheet post-processing apparatus or the image forming apparatus further includes a discharge detection sensor that detects when the post-processing is interrupted, based on both output signals output from the conveyance detection sensor and the discharge detection sensor. While the information regarding the progress of the post-processing at the time of the interruption of the processing is obtained, the image forming apparatus, based on the information, when the post-processing is restarted. Image forming system, characterized in that to resume the image formation from comes the intermediate tray to the subsequent image formed on the sheet was last stored image. 2. When post-processing is interrupted in the course of forming a plurality of N (N ≧ 2) sheets, the count value detected by the discharge detection sensor is set to m ( m ≧ 0), and when the count value detected by the conveyance detection sensor after the m-th sheet bundle is set to n (n ≧ 0), the post-processing of the image forming apparatus is restarted. When ((N
2. The image forming system according to claim 1, wherein an image to be formed on the (m) + n + 1) th sheet is formed first. 3. When the post-processing is interrupted due to a conveyance error occurring in the intermediate tray, the image forming apparatus forms on the ((N × m) +1) th sheet when the post-processing is restarted. 3. The image forming system according to claim 2, wherein the image is formed first when the image is restarted. 4. A count value detected by the discharge detection sensor up to the time point when the post-processing is interrupted is set to m (m ≧ 0);
When the count value detected by the conveyance detection sensor after the m-th sheet bundle is set to n (n ≧ 0), the image forming apparatus sets (m +
2. The image forming system according to claim 1, wherein an image to be formed on the (n + 1) th sheet of the sheets forming the (1) th sheet bundle is formed first. 5. When the post-processing is interrupted due to a conveyance error occurring in the intermediate tray, the image forming apparatus sets the (m + 1) -th sheet bundle to the first sheet when the post-processing is restarted. 5. The image forming system according to claim 4, wherein an image to be formed is formed first when the image is restarted. 6. The image forming apparatus has an image memory for temporarily storing image data corresponding to an image to be formed on a sheet, and after forming an image on a sheet based on the image data, the sheet is 6. The image forming system according to claim 1, wherein said image data is cleared from said image memory at a predetermined timing after being discharged from said image forming apparatus to said sheet post-processing apparatus. 7. The image forming apparatus clears image data corresponding to an image formed on the sheet from the image memory after the conveyance detection sensor confirms that the sheet has been conveyed to the intermediate tray. The image forming system according to claim 6. 8. The image forming apparatus and the sheet post-processing apparatus are individually configured, and an image-formed sheet discharged from the image forming apparatus is carried into the sheet post-processing apparatus. The image forming system according to claim 1, wherein the image forming apparatus and the sheet post-processing apparatus are connected to each other. 9. The image forming system according to claim 1, wherein said sheet post-processing apparatus is integrated into said image forming apparatus. 10. An image forming step of forming an image on paper, and after temporarily storing the image-formed paper in an intermediate tray, collectively stacking a plurality of paper sheets stored in the intermediate tray. A post-processing step of discharging the sheet to a main tray, and when the post-processing step is interrupted, a conveyance detection sensor for detecting a sheet conveyed to the intermediate tray; The image forming process further includes a step of obtaining information on the progress of post-processing at the time of post-processing interruption based on both output signals output from a discharge detection sensor that detects a sheet bundle discharged to a tray. Restarts the image formation from the image following the image formed on the last sheet stored in the intermediate tray based on the information when Image forming method.