JP2011126017A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can obtain a stable image quality while saving resources. <P>SOLUTION: The image forming apparatus which can automatically discharge papers supplied and left in the apparatus, when paper jamming occurs, to the outside of the apparatus has a patch image reading part which reads a patch image for image quality correction formed on the paper, and a controlling part which controls at least an image forming part and the patch image reading part. The controlling part controls the image forming part to form the patch image for image quality correction to the paper located on the upstream side in a paper conveyance direction from the image forming part when paper jamming occurs, and controls the patch image reading part to read the patch image formed on the paper. The image forming apparatus updates an image formation condition in the image forming part on the basis of data on the patch image read by the patch image reading part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that automatically discharges paper that has already been fed and remains in the apparatus when a paper jam occurs.

  When a paper jam occurs in the image forming apparatus, paper that has already been fed may remain in the apparatus in addition to the paper in which the paper jam has occurred. In particular, in a configuration in which a post-processing device is provided on the downstream side of the image forming apparatus main body, when a paper jam (hereinafter referred to as jam) occurs in the post-processing apparatus, a large number of not only the post-processing apparatus but also the image forming apparatus main body. Paper in the middle of the process exists as residual paper. Since the image forming apparatus cannot continue the operation unless the residual paper is removed, various proposals have been made for processing the residual paper. Among them, there is one that automatically discharges residual paper using a bypass conveyance path in the post-processing apparatus or the image forming apparatus main body (see, for example, Patent Document 1).

  In addition, it is widely known that image forming apparatuses automatically perform self-diagnosis periodically. Particularly in the image quality correction of the printing process of the image forming apparatus, various electrophotographic process parameters are corrected with the goal of stabilizing the image quality.

JP-A-9-244482

  In the automatic paper discharge process of the residual paper in the image forming apparatus as described in Patent Document 1, if the paper is discharged to the outside of the system using the bypass conveyance path, the discharged paper may not be reused. Many.

  Also, as an image quality correction for the printing process, an actual printing operation is performed, an image quality adjustment patch is printed on the printing paper, read as image quality data by a sensor, and used for image quality correction. This is undesirable in terms of resource saving. Furthermore, since the image forming apparatus performs a printing operation when correcting the image quality of the printing process, unnecessary energy consumption increases.

  In view of the above problems, the present invention performs image correction using residual paper that is automatically discharged when a jam occurs in the image forming apparatus, and saves resources while obtaining stable image quality. It is an object to obtain an image forming apparatus.

  In the image forming apparatus having an image forming unit for forming an image and capable of automatically discharging the paper that has already been fed and remains in the apparatus when a paper jam occurs, A patch image reading unit that reads a patch image for image quality correction formed on the image forming unit, and a control unit that controls at least the image forming unit and the patch image reading unit, and the control unit has a paper jam. Sometimes, the patch is configured to control the image forming unit so as to form a patch image for image quality correction on a sheet located upstream of the image forming unit with respect to the sheet conveying direction and to read the patch image formed on the sheet. This is achieved by an image forming apparatus that controls an image reading unit and updates image forming conditions in the image forming unit based on the patch image data read by the patch image reading unit.

  According to the present invention, it is possible to obtain an image forming apparatus capable of obtaining stable image quality while saving resources.

1 is an overall configuration diagram of an image forming system according to the present invention. 1 is a block diagram illustrating a control configuration of an image forming system according to the present invention. It is a flowchart figure which shows the outline of operation | movement in the image forming system which concerns on the form of this invention. It is a flowchart figure which shows the implementation conditions of the image quality correction operation | movement which concerns on this Embodiment. It is a flowchart figure which shows the outline of the image quality correction | amendment operation | movement which concerns on this Embodiment. It is a flowchart figure of the patch image printing which concerns on this Embodiment. It is a flowchart figure of the patch image reading which concerns on this Embodiment. It is a flowchart figure of the image quality formation condition change which concerns on this Embodiment.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.

  An overall configuration of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an image forming apparatus having an image forming apparatus main body A, a large-capacity sheet feeding apparatus LT, and post-processing apparatuses FS1, FS2, and FS3. Note that the image forming apparatus according to the present invention is not limited to the configuration including the post-processing device as in the configuration shown in FIG. 1, but includes a configuration including only the image forming apparatus main body.

  In FIG. 1, the large-capacity paper feeder LT has three stages of paper feeders L1, L2, and L3, and the uppermost paper of each paper feeder is fed one by one to the transport path of the image forming apparatus main body A. A paper feed member is provided.

  The image forming apparatus main body A includes an automatic document feeder ADF and an image reading unit SC on the upper side, and an image forming unit IF and a paper feeding unit 1 on the lower side. An operation panel OP is provided on the upper surface of the image reading unit SC. The operation panel OP has a structure in which a touch panel is superimposed on an LCD display screen, and various settings and operations can be performed by pressing the touch panel while viewing the display screen. Can be entered.

  The paper feeding unit 1 includes a plurality of paper feeding units 1a, 1b, and 1c. The paper is supplied from the paper feeding units 1a, 1b, and 1c or the paper feeding units L1, L2, and L3 of the large-capacity paper feeding device LT. The formed toner image is transferred. The transferred image is fixed by the fixing device 3 and discharged from the paper discharge port by the paper discharge roller 4. In the case of double-sided copying, the paper is transported downward before the paper discharge roller 4, is returned to the transfer position again via the double-sided transport path 5 that reverses the paper, and an image is formed on the back surface.

  In this example, the image forming apparatus main body A is an image forming apparatus that forms a monochrome image, but may be an image forming apparatus that forms a color image.

  Next, the configuration of the post-processing devices FS1, FS2, and FS3 will be briefly described. Since the post-processing mechanism itself is publicly known, the portions related to the present application will be described.

  The first post-processing device FS1 is a post-processing machine that performs folding processing, and has two insertion paper trays 10 and 11 for inserting cover sheets and insert paper at the top, and discharges paper when folding processing is performed. A sub discharge tray ST1 is provided. At the bottom, punch processing unit 12 for punching punch holes in the paper, and various folding processing units such as center fold, Z fold, outer tri-fold, inner tri-fold, inner four fold (also called Kannon fold), double parallel fold, etc. 13.

  In order to perform these processes, the post-processing device FS1 includes a plurality of paper transport paths and a transport path switching member, and the paper designated for post-processing branches downward from the downstream of the inlet section 14. It goes to the punch processing unit 12 and the folding processing unit 13 through the conveyance path r10. Further, the conveyance path r11 from the insertion paper trays 10 and 11 joins the conveyance path between the entrance portion 14 and the branch point of the conveyance path r10, and the insertion sheet is inserted between the front and back of the image-formed sheet. Can be inserted. This insertion sheet can also be sent to the transport path r10 for post-processing.

  The conveyance path r12 extending horizontally from the inlet portion 14 guides the sheet to the second post-processing device FS2, or discharges the sheet to the sub discharge tray ST1 through the conveyance path r13 that branches upward before the outlet portion. Used when Further, before the branch point of the transport path r13, the transport path of the paper post-processed by the punch processing unit 12 and the folding processing unit 13 is joined. The folded sheet is discharged to the sub discharge tray ST1 through the conveyance path r13.

  The second post-processing device FS2 is a post-processing machine that performs saddle stitching, and the sheet from the entrance 20 is branched and conveyed to either a downward conveying path r20 or an upward conveying path r21. The The sheet conveyed along the downward conveying path r <b> 20 is overlapped with a sheet fed later to form a plurality of sheet bundles, and the sheet folding unit 25 folds the sheet bundles.

  The folded sheet bundle is conveyed leftward in the drawing by the belt member 24, and the sheet binding unit 26 performs saddle stitching on a plurality of sheet bundles. The saddle stitched sheet bundle is cut at the fore edge by the fore edge cutting processing unit 27 and then discharged to the discharge tray 28. The discharge tray 28 is configured to be pulled out to the front, and the saddle-stitched sheet bundle can be taken out from the front side of the apparatus.

  On the other hand, the sheet conveyed on the conveyance path r21 extending from the downstream side to the upstream side of the inlet 20 is branched to the conveyance path r22 and discharged to the sub discharge tray ST2, or the subsequent post-processing is performed through the conveyance path r23. Sent to the device FS3.

  The third post-processing device FS3 is a post-processing machine that performs side binding on a bundle of sheets. On the downstream side of the inlet 30 of the post-processing device FS3, the conveyance path is branched into a conveyance path r30 directed to the left and a conveyance path r31 directed upward. The conveyance path r31 further includes a conveyance path r32 directed to the sub discharge tray ST3 Branches to a conveyance path r33 toward the main discharge tray 31. The sub carry-out tray ST3 discharges a small amount of paper when the post-processing device FS3 does not perform post-processing. On the other hand, the main discharge tray 31 discharges paper when post-processing is performed and when the number of sheets is large without performing post-processing by all post-processing devices, so that a large amount of paper can be collected. It can be moved up and down.

  A sheet stacker 32 and a stapling mechanism 33 for performing side stitching are disposed downstream of the conveyance path r30. A plurality of sheets traveling on the conveyance path r30 are stacked on the sheet stacker 32, and a predetermined number of sheets are stacked. Then, the staple mechanism 33 performs side binding. The stapled sheets are fed upward with the trailing edge held by a conveying claw provided on a belt 34 constituting a part of the sheet stacker 32, and discharged to the main discharge tray 31.

The relationship between the post-processing that can be performed by the above image forming apparatus and the conveyance path is summarized as follows.
In the case of punch processing and folding processing: entrance 14 → conveying path r10 → punch processing section 12 → folding processing section 13 → conveying path r13 → sub discharge tray ST1
In the case of saddle stitching processing: entrance 14 → conveying path r12 → entrance 20 → conveying path r20 → saddle folding processing unit 25 → saddle stitching processing unit 26 → small edge trimming processing unit 27 → discharge tray 28
In the case of flat binding processing: entrance unit 14 → conveying path r12 → inlet unit 20 → conveying path r21 → conveying path r23 → inlet unit 30 → conveying path r30 → flat binding processing unit 32, 33 → main tray 31
When no post-processing is performed: entrance 14 → conveyance path r12 → inlet section 20 → conveyance path r21 → conveyance path r23 → inlet section 30 → conveyance path r31 → conveyance path r33 → main tray 31
Each conveyance path shown in the present embodiment is configured to be driven independently.

  FIG. 2 is a block diagram showing a control configuration of the image forming apparatus according to the present invention. The image forming apparatus main body A and the post-processing apparatuses FS1, FS2, and FS3 communicate with each other through serial communication units to perform control. Note that the control configuration of the post-processing devices FS2 and FS3 is substantially the same as that of the post-processing device FS1, and is therefore simplified.

  As shown in FIG. 2, the image forming apparatus main body A has an image forming apparatus control unit 100 (hereinafter abbreviated as the control unit 100), which is based on input information from the operation panel OP. The paper feeding unit 1 that feeds the paper is controlled, and the paper is conveyed by using the signal input of the paper sensor in the conveyance unit. Further, the image reading unit SC is controlled to read the original image, and the image forming unit IF is controlled to form the toner image on the conveyed paper. Further, control information is exchanged via the serial communication unit 102, the post-processing content instruction and the state of the post-processing device FS1 are monitored, and the instructed post-processing is completed.

  Note that a print instruction from a computer connected to the network is received from the LAN interface 101 (hereinafter abbreviated as “LAN IF 101”), and similarly, paper conveyance, image formation, and post-processing can be performed.

  The post-processing device FS1 has a post-processing device control unit 110 (hereinafter abbreviated as the control unit 110). The control unit 110 obtains control information from the control unit 100 via the serial communication unit 111, and performs post-processing. When the processing is instructed, the paper is switched to the conveyance path r10 for guiding the paper to the post-processing unit, and the paper is post-processed by controlling the conveyance unit, the post-processing unit, and the insertion paper tray. Further, the control unit 100 is notified of the state of the post-processing apparatus as control information via the serial communication unit 111. When the post-processing is not instructed, the sheet is switched to the conveyance path r12 that leads the paper to the subsequent post-processing devices FS2 and FS3, and the control information is passed to the subsequent post-processing device via the serial communication unit 112. The same applies to the post-processing device control units 120 and 130 of the post-processing devices FS2 and FS3.

  In this embodiment, at least one of the control unit 100 and the post-processing device control units 110, 120, and 130 corresponds to the “control unit” in the claims.

  The control unit 100 of the image forming apparatus main body A receives detection signals from a plurality of paper sensors 103 arranged on the conveyance path in the image forming apparatus main body A, and conveys paper based on the detection signals. Perform printing as instructed. Similarly, a plurality of paper sensors 113 are also provided in the post-processing device FS1, and the control unit 110 processes the paper as instructed by the detection signals from these sensors in the same manner as the image forming apparatus main body A.

  The jam generated in the post-processing device FS1 is notified from the control unit 110 to the control unit 100 via the serial communication units 111 and 102, and the control unit 100 and the control unit 110 check the state of the sheet and also the image forming system. The automatic paper discharge process is started to the sub discharge tray ST1 of the post-processing device FS1 without stopping the paper transport. The same applies to the paper sensors and the control units 120 and 130 of the post-processing devices FS2 and FS3.

  A plurality of paper sensors are schematically indicated by triangular marks (▲) in the conveyance paths of the image forming apparatus main body A and the post-processing apparatuses FS1, FS2, and FS3 in FIG. Of course, this triangular mark is shown schematically and is not an accurate position. The paper sensor detects the leading edge and trailing edge of the paper traveling on the conveyance path and sends a signal to the control units 100, 110, 120, and 130. That is, each control unit can grasp the positions of the plurality of sheets in the image forming apparatus main body A and the post-processing apparatuses FS1, FS2, and FS3 with the paper sensors in the conveyance path.

  In this embodiment, an example of an image forming apparatus in which FS1, FS2, and FS3 and three types of post-processing devices are connected in series as post-processing devices to the image forming apparatus main body A has been described. It is of course possible to connect to the image forming apparatus main body A and use it as an image forming apparatus.

  Hereinafter, an outline of the operation of the image forming apparatus according to the present invention will be described with reference to FIG. When an image forming job including post-processing instructed by the image forming apparatus is being executed (step S1), if no jam occurs in the post-processing apparatus (step S2: No), the designated job is completed. An image forming job including post-processing is executed [step S3: No]. When the designated job is completed (step S3: Yes), if there is a next job (step S4: Yes), the next job is executed similarly (step S1).

  Normally, this flow is continued. However, when a jam occurs in the post-processing device FS1 (step S2: Yes), if the image forming apparatus main body A has the image quality correction operation execution condition (step S5: Yes), An image quality correction operation for printing a patch image for image quality correction on a sheet and reading the patch image and updating various parameters used for image quality stabilization in the image forming unit IF is performed (step S6). Simultaneously with the occurrence of the jam, the post-processing device FS1 switches the paper conveyance path to the sub discharge tray ST1, and continues until the automatic discharge processing of the remaining paper is completed (step S7). Even if a jam occurs in the post-processing device FS1, if the image quality correction operation execution conditions are not ready (step S5: No), the process jumps to step S7 and continues until the automatic discharge process of the remaining paper is completed (step S7). .

  Although not shown in the figure, when no jam has occurred, it is preferable that a steady image quality correction operation is automatically performed at predetermined intervals for each predetermined number of sheets.

  FIG. 4 shows in more detail the contents of the image quality correction operation execution condition in step S5 when a jam occurs in step S2 shown in FIG. In addition, although FS1 is described as a post-processing device, the same applies to FS2 and FS3.

  As shown in FIG. 4, first, when a jam occurs in the post-processing device FS1 during normal operation of the image forming apparatus including post-processing (step S2: Yes), the control unit 110 of the post-processing device FS1 performs serial processing. The control unit 100 of the image forming apparatus main body A is notified through the communication units 111 and 102 (step S101).

  If the user inputs a cancel of the image quality correction operation to be performed from the operation panel OP or has been set in the control unit 100 in advance, the instruction is given priority and the image quality correction operation is canceled (step (S102: Yes), the process jumps to step S7 (see FIG. 3). If there is no cancel instruction and the image quality correction operation is not canceled (step S102: No), the following image quality correction operation determination is performed.

  First, the control unit 100 refers to the registered next job information described in the storage unit 104 and confirms whether or not the printing paper is the same as the current paper (step S103). If the print paper is different from the current paper (step S103: No), the image quality correction operation is not performed and the process jumps to step S7 (see FIG. 3). If the printing paper is the same as the current paper (step S103: Yes), for example, it is determined whether the environmental condition of the current temperature and humidity has changed by more than a specified value from when the previous image quality correction operation was performed (step S104). ), If changed (step S104: Yes), the process proceeds to step S106. If it has not changed (step S104: No), the print number counter stored in the storage unit 104 is referred to and it is determined whether or not the print number has reached a predetermined number (step S105). ). When the print number counter has reached the specified number of image quality correction operation execution (step S105: Yes), the process proceeds to step 106, and the print number counter has not reached the specified image quality correction operation execution number. (Step S105: No), the image quality correction operation is not performed, and the process jumps to Step S7 (see FIG. 3).

  Next, in the image forming unit IF, it is determined whether or not there is a fed sheet before forming a toner image on the photoconductor 2 by an electrophotographic process (step S106). If there is a fed sheet (step S106: Yes) ) Proceeds to step S6 (see FIG. 3). If there is no paper that has already been fed in the image forming unit IF (step S106: No), a new paper is fed from the paper feeding unit 1 or the large-capacity paper feeder LT (step S107), and step S6 ( (See FIG. 3).

  In other words, when a jam occurs, the paper size of the next job is the same and the environmental condition changes more than the specified value. If the number of image quality correction operations has been reached, the image quality correction operation in step S6 (see FIG. 3) is performed in order to maintain the quality of the output image quality.

  If there is no paper already fed for patch image printing (step S106: No), the process jumps to step S7 (see FIG. 3) so that the image quality correction operation in step S6 (see FIG. 3) is not performed. It may be configured.

  FIG. 5 is a flowchart showing an outline of the image quality correction operation in step S6 shown in FIG.

  As shown in FIG. 5, in the image quality correction operation, first, a patch image for image quality correction is printed by the image forming unit IF (step S10), and the patch image is read by the patch image reading unit (step S11). . Next, based on the read patch image, the image forming conditions, which are parameter correction of the electrophotographic process, are updated (step S12).

  The detailed procedure for printing the patch image for image quality correction (FIG. 5, step S10) will be described below with reference to the patch image printing flowchart of FIG.

  A detailed procedure for reading the patch image for image quality correction (FIG. 5, step S11) will be described with reference to the patch image reading flowchart of FIG.

  A detailed procedure for updating the image forming condition (FIG. 5, step S12) will be described with reference to the image forming condition updating flowchart of FIG.

  First, the procedure for printing a patch image will be described with reference to FIG. When a jam occurs in the post-processing device FS1, toner image formation in the middle of creation is stopped (step S201). This process may be performed in units of pages or in the middle of a page.

  In place of the toner image to be created on the subsequent paper, the patch image for image quality correction is determined based on the change in the environmental condition of the temperature and humidity described above, and if there is a change defined in the environmental condition (step S202: Yes), When patch image 1 is selected (step S203) and there is no prescribed change (step S202: No), patch image 2 is selected (step S204). In order to effectively perform image correction, a patch image that can easily discriminate changes in various parameters of the image forming unit IF to be corrected is required, and the patch image is selected according to image correction conditions. For example, when the temperature and humidity change described above is greater than or equal to a specified value, the patch image selection for image quality correction described above mainly creates an electrostatic latent image in the electrophotographic process in the image forming unit IF, When the patch image 1 related to the parameter change at the time of transfer is selected, and the temperature and humidity change is within the specified value and the number of printed sheets reaches the specified range, the electrostatic latent image creation mainly in the electrophotographic process, The patch image 2 related to the development parameter change is selected.

  The selected patch image is set in the print memory (step S205).

  In the image forming unit IF, the data of the selected patch image in the print memory is formed as a toner image on the photosensitive member 2 in accordance with the toner image creation timing, and is printed (step S206).

  Next, patch image reading will be described with reference to the flowchart of FIG. The patch image reading unit 114 may be installed in the image forming apparatus main body A or in the post-processing apparatus FS1, but in this embodiment, it is installed in the post-processing apparatus FS1. Explain that it is.

  First, when the control unit 110 detects a jam, the control unit 110 notifies the control unit 100 of the occurrence of a jam through the serial communication units 111 and 102 (step S301). At the same time, the control unit 110 switches the paper transport path from the image forming apparatus main body A to paper discharge to the sub paper discharge tray ST1 (step S302). Along with the switching of the sheet transport path, all subsequent sheets in the post-processing apparatus FS1 and residual sheets in the image forming apparatus main body A are discharged to the sub discharge tray ST1 (step S303).

  Reading the patch image for image quality correction created by the image forming unit IF of the image forming apparatus main body A requires information on which paper the patch image is printed on. Is synchronized with the paper discharge roller 4 (see FIG. 1) of the image forming apparatus main body A, the control unit 100 transfers to the control unit 110 via the serial communication units 102 and 111. Notice. With this signal, patch image print information is added to the paper discharged to the post-processing device FS1, and the control unit 110 determines the paper on which the patch image is printed by the patch image reading unit 114 provided in the transport path. (Step S304: Yes), the patch image printed on the paper is read (Step S305).

  In addition, the method of reading a patch image printed on a specific sheet without fail is described as follows. The patch image recognition unit 114 performs patch image recognition for each sheet to be transported, or immediately before the patch image. Alternatively, a dedicated mark that can be recognized by the patch image reading unit 114 may be printed at the same time as the patch, and the patch image reading unit 114 may recognize the mark.

  The read image quality correction patch image data is transferred to the control unit 100 through the serial communication units 111 and 102.

  Next, the image forming condition update will be described with reference to FIG. First, the control unit 100 obtains the patch image data read in step S305 (see FIG. 7) from the control unit 110 (step S401). Thereafter, the patch image read data is converted into image correction data, which is a parameter usable in the image forming unit IF (step S402).

  The control unit 100 compares the obtained new image correction data with the image quality correction data stored in the storage unit 104 (see FIG. 2) at the time of previous image quality correction, and when there is a change (step S403: Yes) is updated and stored in the storage unit 104 (step S404). If there is no change (step S403: No), the image quality correction data in the storage unit 104 is not updated.

  The image quality correction data updated in the storage unit 104 of the control unit 100 is used for the control unit 100 to determine the respective parameter values of the image forming unit IF from the next job. Needless to say, the details of the updated image formation data are applicable to all already widely known electrophotographic processes.

  As described above, when a jam occurs in the post-processing apparatus, the image quality correction operation is performed using the supplied paper upstream from the image forming unit IF, and the image forming conditions are updated. An image forming apparatus capable of obtaining stable image quality while achieving resource recycling can be obtained.

  Further, by determining whether to update the image forming condition in the image forming unit IF based on the registered next job information, the environmental condition at the time of the previous image forming condition update, and the number of printed sheets. The image quality correction operation can be performed only when necessary without performing the image quality correction operation of the present invention whenever an accidental post-processing device jam occurs.

  Further, although the patch image reading unit has been described as being installed in the post-processing apparatus in the present embodiment, it is not limited to this. When the residual paper has a bypass conveyance path and a sub-discharge tray that can automatically eject the sheet outside the image forming apparatus main body, a patch image reading unit may be installed in the bypass conveyance path in the image forming apparatus main body. A configuration may be adopted in which a patch reading unit is installed in the main body of the forming apparatus, and after the reading, the sheet is discharged to a sub discharge tray of the post-processing apparatus.

DESCRIPTION OF SYMBOLS 1 Paper feed part 2 Photoconductor 3 Fixing device 4 Paper discharge roller 14, 20, 30 Entrance part 100 Image forming apparatus control part 101 LAN IF
102, 111, 112 Serial communication unit 103, 113 Paper sensor 104 Storage unit 110, 120, 130 Post-processing device control unit 114 Patch image reading unit A Image forming apparatus main body FS1, FS2, FS3 Post-processing device IF Image forming unit OP operation Panel r10, r11, r12, r13 Transport path ST1, ST2, ST3 Sub discharge tray

Claims (5)

An image forming unit for forming an image;
In an image forming apparatus capable of automatically ejecting paper that has already been fed and remains in the apparatus when a paper jam has occurred,
A patch image reading unit that reads a patch image for image quality correction formed on a sheet;
A control unit that controls at least the image forming unit and the patch image reading unit;
The controller is
Controlling the image forming unit to form a patch image for image quality correction on a sheet located upstream of the image forming unit in the paper transport direction when a paper jam occurs,
Controlling the patch image reading unit to read the patch image formed on the paper;
An image forming apparatus that updates image forming conditions in the image forming unit based on the patch image data read by the patch image reading unit.   The image forming apparatus according to claim 1, wherein the control unit determines whether to update an image forming condition in the image forming unit.   The control unit determines whether or not to update the image forming condition in the image forming unit based on the registered next job information, the environmental condition at the time of the previous image forming condition update, and the number of images formed. The image forming apparatus according to claim 2. The image forming apparatus includes an image forming apparatus main body having the image forming unit, and a post-processing apparatus that performs post-processing on a sheet on which an image is formed by the image forming apparatus main body.
The image forming apparatus according to any one of claims 1 to 3, wherein the patch image reading unit is installed in a sheet conveyance path in the post-processing apparatus.   The image forming apparatus according to claim 4, wherein the patch image reading unit is installed in a sheet conveyance path in the main body of the image forming apparatus.

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