JP2022110335A - Image forming system and image forming method - Google Patents

Abstract

To provide an image forming system that, when an abnormality occurs in a sheet state of sheets to be conveyed, does not execute inappropriate feedback correction.SOLUTION: On the basis of an amount of positional deviation of images that an image forming unit 30 continuously forms on a plurality of sheets Sh with respect to a reference image, an image forming system 1 performs feedback correction for correcting the positions of the images formed on the sheets Sh, and the image forming system comprises: a media sensor or a conveyance state detection sensor that detects a sheet state of the sheets Sh conveyed on a conveyance path; and a control unit 50 that, when determining that the sheet state does not satisfy a preset condition, does not perform the feedback correction for the amount of positional deviation.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming system and an image forming method.

2. Description of the Related Art Conventionally, image inspection has been performed to detect abnormal portions of an image printed on paper by analyzing a read image of the image printed on paper. In this image inspection, for example, image abnormalities such as stains and color shifts occurring in the actually printed image, and position shifts with respect to the reference position are detected.

While the image forming apparatus is continuously printing on a large amount of paper, misalignment of images printed on some paper may occur. A misalignment means that an image is printed at a position different from the position where it should be printed. If the amount of misalignment is within a preset threshold range, feedback correction is performed to correct the position of the image printed on the paper by the image forming apparatus. If the positional deviation of the image exceeds the allowable range, the paper on which this image is printed is discarded as waste paper. Therefore, in order to prevent image misalignment during continuous printing, image formation that can control paper orientation and transport timing, such as paper skew correction by registration rollers installed in the transport path and skew correction by roller swing. Devices have been provided in the past.

During printing, heat and pressure are applied to the paper, and the state of the paper changes. For this reason, the image forming apparatus cannot meet the accuracy requirement for image misalignment simply by controlling the orientation of the paper being conveyed. Therefore, a technique disclosed in Japanese Patent Application Laid-Open No. 2002-100000 has been proposed, which corrects the misalignment of an image based on a read image of a printed sheet.

In Patent Document 1, when it is determined that the amount of print misalignment is equal to or less than a predetermined threshold, image data read by a reading unit is corrected to image data that can be compared with print data in order to determine whether there is an abnormality. There is a technique for detecting an abnormality in an image printed on a sheet without correcting the image data for inspection when the print misalignment amount of the image data printed on the sheet is larger than a predetermined threshold. disclosed. In other words, in the technique disclosed in Japanese Patent Application Laid-Open No. 2002-200010, whether or not to perform image feedback correction is determined using the result of reading the print misalignment amount after print output.

Japanese Unexamined Patent Application Publication No. 2011-123106

In the technique disclosed in the above-mentioned Patent Document 1, image feedback correction is performed if the amount of misalignment of the printed image with respect to the reference image is equal to or less than a predetermined threshold. Therefore, even if the paper condition is abnormal before the print output is completed, if the misalignment amount of the image read after the print output is within a range that does not exceed the set threshold value, the misalignment amount can be corrected by feedback. Be eligible. Here, as an abnormality of the paper status, for example, the paper is conveyed skewed, the paper contains excessive moisture, or the paper type different from the paper type set for the job is mixed. It is assumed that

For example, while the image forming apparatus is continuously printing on a plurality of sheets of paper, some of the sheets of paper may suddenly be conveyed skewed. Using the technique disclosed in Patent Document 1, feedback correction is performed when the amount of positional deviation of an image printed on a sheet conveyed obliquely does not exceed a threshold value. For this reason, inappropriate feedback correction may be performed based on the amount of misalignment of the printed image even for paper in an abnormal paper state.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to prevent inappropriate feedback correction.

In order to achieve the above-described object, an image is formed on a plurality of recording materials based on the amount of positional deviation of images successively formed by an image forming unit on a plurality of recording materials from a reference image, which reflects one aspect of the present invention. An image forming system that performs feedback correction for correcting the position of an image includes a recording material state detection unit that detects the state of a recording material conveyed on a conveying path, and a recording material state detection unit that detects the state of the recording material when the state of the recording material satisfies a preset condition. and a control unit that does not subject the amount of positional deviation to feedback correction when the determination is made.

In the present invention, the amount of positional deviation is not subject to feedback correction unless the state of the recording material satisfies a preset condition, so that inappropriate feedback correction is not performed.
Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is a schematic configuration diagram showing a configuration example of an image forming system according to an embodiment of the present invention; FIG. 1 is a block diagram showing a configuration example of a control system of an image forming apparatus according to an embodiment of the invention; FIG. 4 is a graph showing an image position shift and an object of feedback correction according to an embodiment of the present invention; 5 is a list defining conditions for determining whether or not to subject each of the paper transport state and the paper physical property value to the feedback correction according to the embodiment of the present invention. 4 is a flow chart showing an example of processing of the image forming system according to one embodiment of the present invention; It is a list showing the difference between the conventional technology and the technology according to the present embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same function or configuration are denoted by the same reference numerals, thereby omitting redundant description.

[One embodiment]
<Configuration of Image Forming System>
First, a configuration example of an image forming system according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a schematic configuration diagram showing a configuration example of an image forming system 1 according to one embodiment of the present invention. It should be noted that FIG. 1 describes the elements considered necessary for explaining the present invention or related elements, and the image forming system of the present invention is not limited to the example shown in FIG.

An image forming system 1 includes an image forming device 2 and an inspection device 3 . The image forming apparatus 2 is an example of an image forming apparatus that forms an image on a sheet by an electrophotographic method that forms an image using static electricity. The image forming apparatus 2 forms a color image on a sheet in a tandem format in which toner images of four colors, yellow (Y), magenta (M), cyan (C), and black (K) are superimposed. A PC 70 or the like operated by an operator is connected to the image forming apparatus 2 via a LAN (Local Area Network) (not shown). A job is input from the PC 70 to the image forming apparatus 2 via the LAN. The image forming apparatus 2 performs various types of processing such as image forming processing according to a job input from the PC 70 .

The image forming apparatus 2 includes an image input unit 11 having an automatic document feeder (ADF) 12, an operation display unit 13, and a printer unit 10 having a paper feed tray 20 and an image forming unit 30. .

The image input unit 11 optically reads an image from a document on the platen of the ADF 12 and A/D converts the read image to generate image data (scan data). The image input unit 11 can also read an image formed on a document on the platen glass.

The operation display unit 13 includes a display unit such as a liquid crystal panel and an operation unit such as a touch sensor. The display unit and the operation unit are integrally formed as a touch panel, for example. The operation display unit 13 generates an operation signal representing the content of the operation input by the operator to the operation unit, and supplies the operation signal to the control unit 50 (see FIG. 2 described later). Based on the display signal supplied from the control unit 50, the operation display unit 13 also displays the details of operations performed by the operator, setting information, and the like on the display unit. It should be noted that it is also possible to configure the operation unit with a mouse, tablet, or the like, and to configure it separately from the display unit.

The paper feed tray 20 (an example of a paper supply unit) is a container that accommodates paper Sh (an example of a recording material) on which image formation is performed in the image forming unit 30 . In this embodiment, an example in which two paper feed trays 20 are provided is given, but the number of paper feed trays 20 may be one, or three or more. Each paper feed tray 20 accommodates paper Sh having different paper types, basis weights, and the like. The image forming apparatus 2 can also form an image on a resin sheet, which is an example of a recording material.

The image forming apparatus 2 is provided with a transport path 21 for transporting the paper Sh fed from the paper feed tray 20 to the inspection device 3 . The transport path 21 is provided with a plurality of transport rollers for transporting the sheet Sh. Among the transport paths 21, the transport path from the paper feed tray 20 that supplies the paper Sh to the image forming section 30 is used as an example of the first transport path. Further, the transport path 21 from the fixing section 36 that fixes the image formed on the sheet Sh to the discharge of the sheet Sh is used as an example of the second transport path.

On the downstream side of the fixing section 36 , the transport path 21 extends and is connected to the transport path 41 of the inspection device 3 . Also, a reverse transport path 22 (an example of a third transport path) that branches downstream of the fixing section 36 and merges with the transport path 21 on the upstream side of the printer section 10 is connected to the transport path 21 . After an image is formed on the front surface (an example of the first surface) of the sheet Sh by the image forming unit 30 in this way, the conveying path until an image is formed on the back surface (an example of the second surface) of the sheet Sh is the second transport path. It is used as an example of three transport paths. The reverse transport path 21 is also provided with a plurality of transport rollers for transporting the reversed sheet Sh. The reversing transport path 22 is provided with a reversing section 23 for reversing the sheet Sh. The sheet Sh reversed by the reversing section 23 is returned to the upstream side of the transport path 21 through the reverse transport path 22 . Also, the sheet Sh reversed by switching the path may be transported to the inspection device 3 after being returned to the transport path 21 on the downstream side of the fixing section 36 .

The image forming section 30 includes four image forming units 31Y, 31M, 31C, and 31K for forming toner images of Y, M, C, and K colors. to form The image forming units 31Y, 31M, 31C and 31K respectively include a charging section, an exposure section (none of which is shown), photosensitive drums 32Y, 32M, 32C and 32K as image carriers, and developing sections 33Y, 33M and 33C. , 33K.

The developing units 33Y, 33M, 33C, and 33K irradiate the surfaces (peripheries) of the photosensitive drums 32Y, 32M, 32C, and 32K with light according to the image, thereby electrostatically forming the circumferences of the photosensitive drums. form a latent image. The developing units 33Y, 33M, 33C and 33K form toner images on the photosensitive drums 32Y, 32M, 32C and 32K by attaching toner to the electrostatic latent images.

The image forming section 30 also includes an intermediate transfer belt 34 , a secondary transfer section 35 and a fixing section 36 . The intermediate transfer belt 34 is a belt onto which the images formed on the photosensitive drums 32Y, 32M, 32C, and 32K are primarily transferred. The secondary transfer unit 35 is a roller that secondarily transfers the toner image of each color that has been primarily transferred onto the intermediate transfer belt 34 onto the paper Sh transported along the transport path 21 .

The fixing unit 36 is arranged downstream of the secondary transfer unit 35 in the sheet conveying direction, and performs a fixing process on the sheet Sh supplied from the image forming unit 30 and having the color toner image formed thereon. The fixing section 36 fixes the image transferred by the image forming section 30 to the surface side of the sheet Sh by performing a fixing process of heating and pressing the sheet Sh on which the image is formed. The paper Sh on which the image is fixed by the fixing unit 36 is conveyed to the inspection device 3 through the conveying path 21, or after being reversed by the reversing unit 23 through the reversing conveying path 22, is conveyed upstream of the printer unit 10. Returned to road 21. The printer unit 10 forms an image on the back surface of the sheet Sh whose front and back sides are reversed. After that, the sheet Sh subjected to the fixing process by the fixing section 36 is conveyed to the inspection device 3 . Note that processing from the image forming unit 30 of the image forming apparatus 2 forming an image on the sheet Sh to fixing the image onto the sheet Sh by the fixing unit 36 is called “printing”. Further, conveying the sheet Sh from the fixing section 36 to the downstream side of the conveying path 21 is also called "print output".

The inspection device 3 inspects whether the image printed on the sheet Sh transported from the image forming device 2 is normal or abnormal. The paper Sh transported to the inspection device 3 is a printed matter on which images are formed on both sides or one side. The inspection device 3 reads the images formed on both sides or one side of the sheet Sh by the image forming device 2 and performs a predetermined inspection.

The inspection device 3 transmits to the control unit 50 of the image forming apparatus 2 the read images obtained by reading the front and back surfaces of the sheet Sh by the reading unit 45 . The control unit 50 calculates the amount of positional deviation from the reference position based on the read image received from the inspection device 3 . Then, the control unit 50 performs feedback correction for correcting the position of the image formed on the sheet Sh based on the positional deviation amount of the image formed on the plurality of sheets Sh by the image forming unit 30 in succession from the reference image. . The image forming section 30 forms the image feedback-corrected by the control section 50 on the sheet Sh to be conveyed from the conveying path 21 from the next time onward. Note that a control unit (not shown) of the inspection device 3 performs a process of calculating the amount of positional deviation, and the control unit 50 of the image forming device 2 receives the amount of positional deviation from the inspection device 3 and determines whether or not feedback correction is possible. good too.

Further, the inspection device 3 can compare the read image and the reference image to inspect whether the image formed on the sheet Sh has stains, streaks, or the like. If the image formed on the sheet Sh is free of stains, streaks, etc., the inspection device 3 determines that the image is normal. Conversely, if the image formed on the sheet Sh has stains, streaks, or the like, the inspection device 3 determines that this image is abnormal. The inspection device 3 then transmits the inspection result of the read image to the control unit 50 of the image forming device 2 . The image forming apparatus 2 can display the inspection result and the read image on the operation display section 13 . The operator of the image forming apparatus 2 can confirm the inspection results and the contents of the read image based on the contents displayed on the operation display section 13 .

The inspection device 3 transports the sheet Sh transported from the image forming apparatus 2 on the transport paths 41, 42, and 43, the switching unit 44, the reading units 45a and 45b, the colorimeters 46a and 46b, and the transport path 41. It has paper discharge trays 47 and 48 for discharging the paper Sh that has been collected.

The transport path 41 is connected to the transport path 21 of the image forming apparatus 2 . The transport path 41 transports the sheet Sh received from the transport path 21 inside the inspection device 3 . The transport path 41 until the paper Sh is discharged is used as an example of the fourth transport path. Downstream of the transport path 41, the transport paths 42 and 43 are branched.

The reading units 45a and 45b are examples of image input devices such as image sensors. The reading units 45a and 45b, for example, project light onto the surface of the paper Sh and take in reflected light from the paper Sh as image data. Such reading of the image data of the sheet Sh by the reading units 45a and 45b is called "reading". Also, the image data of the sheet Sh is called a "read image". The reading unit 45 a reads the sheet Sh conveyed along the conveying path 41 from below the conveying path 41 , and the reading unit 45 b reads the sheet Sh conveyed along the conveying path 41 from above the conveying path 41 . In the following description, since the reading units 45a and 45b are not distinguished from each other, they are collectively referred to as "reading unit 45". The reading unit 45 outputs the read image of the paper Sh to the control unit 50 of the image forming apparatus 2 . The control unit 50 stores the read image input from the reading unit 45 in the RAM 503 .

The colorimeters 46a and 46b read the images formed on the upper and lower surfaces of the sheet Sh transported on the transport path 41, and measure the color density (reflection density) of the image based on the image information obtained by reading. It is an example of a color density measuring device for measurement. The colorimeter 46 a reads the sheet Sh conveyed along the conveying path 41 from below the conveying path 41 , and the colorimeter 46 b reads the sheet Sh conveyed along the conveying path 41 from above the conveying path 41 . In the following description, since the colorimeters 46a and 46b are not distinguished from each other, they are collectively referred to as the "colorimeter 46". The colorimeter 46 outputs information on the measured color density to the control section 50 of the image forming apparatus 2 . Note that the color density information output from the colorimeter 46 to the inspection device 3 may be included in the read image.

The inspection device 3 includes transport paths 42 and 43 connected to the transport path 41 . The transport paths 41 to 43 are provided with a plurality of transport rollers for transporting the sheet Sh.

The transport path 42 is a path that branches from the middle of the transport path 41, and discharges the sheet Sh inspected by the inspection device 3 to a sheet discharge tray 47 (an example of a sheet discharge unit). Sheets Sh whose images have been determined to be normal by the inspection device 3 (also referred to as “normal sheets”) are discharged to the sheet discharge tray 47 .

The transport path 43 is also a path that branches from the middle of the transport path 41, and ejects the sheet Sh inspected by the inspection device 3 to a sheet ejection tray 48 (an example of a sheet ejection section). Sheets Sh whose images have been determined to be abnormal by the inspection device 3 (also referred to as “abnormal sheets”) are discharged to the sheet discharge tray 48 .

The switching unit 44 switches the conveying direction of the sheet Sh so that the sheet Sh is conveyed to one of the conveying paths 42 and 43 . If the inspection device 3 has only one discharge tray 47, normal sheets and abnormal sheets are discharged together. In this case, the normal paper and the abnormal paper are ejected with a slight shift in the direction orthogonal to the paper ejection direction.

In this embodiment, the image forming apparatus 2 can form images on both sides of the sheet Sh, so the inspection apparatus 3 inspects both sides of the sheet Sh. However, the inspection device 3 may be configured to inspect only one side of the sheet Sh conveyed from an image forming apparatus capable of forming an image on only one side of the sheet Sh.

In the present embodiment, shaded areas in the drawing are represented as installation positions P1 to P4 of the transport path where the paper state detection unit can be installed. The paper state detection unit has a function of detecting the paper state of the paper Sh transported on the transport path. A paper state detection unit (an example of a recording material state detection unit) for detecting the paper state (an example of the recording material state) of the paper Sh is installed at one of the installation positions P1 to P4. One or a plurality of paper state detection units are provided in the transport paths of the image forming device 2 and the inspection device 3 . As the paper state detection unit, for example, there is a media sensor 61 that measures physical property values of the paper Sh, or a transport state detection sensor 62 that detects the transport state of the paper Sh.

The installation position P1 is on the transport path 21 and is a position (upstream from the image forming section 30) before the image forming section 30 forms an image on the sheet Sh. At least one of the one or more paper state detection units installed on the transport path is installed at the installation position P<b>1 on the upstream side of the image forming unit 30 .

The installation position P2 is a position on the transport path 21 and immediately after the image formation on the sheet Sh by the image forming section 30 and the image fixing by the fixing section 36 is performed.
The installation position P3 is on the reversing transport path 22 before joining the transport path 21 .
The installation position P4 is on the transport path 41 of the inspection device 3 .

The media sensor 61 is an example of a physical property value sensor that detects a physical property value of the sheet Sh, and is located upstream of the image forming section 30, and is a conveying path from the paper feed tray 20 that supplies the sheet Sh to the image forming section 30. is installed in The media sensor 61 is arranged in a section (for example, installation position P1) from when the paper Sh is fed until an image is formed on the front side or the back side of the paper Sh, and the physical property value of the paper Sh (“paper physical property value ) is detected. For example, the physical property sensor detects at least one of the stiffness, air permeability, smoothness, thickness, moisture content, and resistance of the sheet Sh as the state of the sheet.

The transport state detection sensor 62 is provided in at least one of the first transport path, the second transport path, the third transport path, and the fourth transport path, and detects the transport state of the sheet Sh. For example, the transport state detection sensor 62 is installed in at least one of installation positions P1 to P4. The conveying state detection sensor 62 detects at least one sheet conveying state as the sheet state among the bending, skewing, conveying time in a predetermined section, and curl amount of the sheet Sh to be conveyed. In this manner, the image forming system 1 may be provided with a plurality of transport state detection sensors 62 . A media sensor 61 and a transport state detection sensor 62 are both provided at the installation position P1.

[Configuration of Control System of Image Forming Apparatus]
Next, a configuration example of the control system of the image forming apparatus 2 will be described with reference to FIG.
FIG. 2 is a block diagram showing a configuration example of a control system of the image forming apparatus 2. As shown in FIG.
The image forming apparatus 2 includes a communication I/F section 51 , a sheet conveying section 24 , an image input section 11 , an image forming section 30 , a control section 50 , a storage section 52 , a fixing section 36 and an operation display section 13 .

The communication I/F unit 51 is an interface that transmits and receives data to and from the PC 70, which is a terminal operated by an operator, via a network or a dedicated line. A NIC (Network Interface Card), for example, is used as the communication I/F unit 51 .

The sheet conveying unit 24 drives the conveying rollers (not shown) provided on the conveying path 21 and the reversing conveying path 22 shown in FIG. In the present embodiment, the paper transport section 24 may control the driving of the transport rollers and the branch section 44 provided in the transport paths 41 to 43 of the inspection device 3 . Then, the sheet conveying section 24 outputs the driving state of each conveying path, the conveying speed of the sheet Sh, and the like to the control section 50 .

The control unit 50 includes a CPU (Central Processing Unit) 501 , a ROM (Read Only Memory) 502 , a RAM (Random Access Memory) 503 and an input image processing unit 504 .
The ROM 502 stores programs executed by the CPU 501 of the control unit 50 or data used when the programs are executed. The CPU 501 controls each unit that configures the image forming apparatus 2 by reading programs stored in the ROM 502 .
The RAM 503 is temporarily written with variables, parameters, and the like generated during the arithmetic processing of the CPU 501 .

The input image processing unit 504 performs predetermined image processing on the input image included in the job input from the PC 70 via the communication I/F unit 51, and creates image data for printing. The input image processing unit 504 also performs image processing on the image data acquired from the document read by the image input unit 11 with the ADF 12 or the image data acquired from the outside, and creates image data for printing. This print image data is sent to the image forming section 30 .

The control unit 50 controls the sheet conveying unit 24 to drive the conveying rollers and convey the sheet Sh on the conveying path 21 . The control unit 50 also outputs the image data for printing created by the input image processing unit 504 to the image forming unit 30 . Further, the control section 50 controls the image forming section 30 to form an image on the paper Sh. Further, the control section 50 controls the fixing section 36 to fix the image on the paper Sh.

The control unit 50 uses the result of determining the positional deviation between the read image of the printed sheet Sh and the reference image to enable feedback correction for correcting the positional deviation of the image formed on the sheet Sh from the next time onwards. and Note that the next time represents the timing at which the sheet Sh is conveyed to the image forming section 30 and an image is formed on the sheet Sh after the control section 50 calculates the positional deviation amount and after the timing at which the feedback correction of the image is completed in time. . Therefore, the control unit 50 determines whether feedback correction is possible after calculating the amount of positional deviation based on the read image of the image formed on the sheet Sh.

However, the control unit 50 receives the measurement result of the physical property value measured by the media sensor 61 and the measurement result of the sheet conveying state detected by the conveying state detection sensor 62, and determines whether feedback correction can be performed. If the control unit 50 determines that the paper state does not satisfy the preset conditions, the control unit 50 does not subject the positional deviation amount to feedback correction. Note that the condition defines whether the paper state (paper transport state and paper physical property values) is within the threshold range defined for each item shown in FIG. 4 described later, or is less than the threshold. is. A paper state satisfies a condition if the paper state is within a threshold or less than a threshold. On the other hand, if a certain paper state is out of the range of the threshold value or exceeds the threshold value, it is said that the condition is not satisfied. A method for deciding whether feedback correction can be performed will be described later with reference to FIG. 3 and subsequent figures.

Note that even if the control unit 50 determines that the feedback correction can be performed, it is necessary to prevent abrupt correction of the image on the paper Sh that is being printed. Therefore, the control unit 50 calculates a moving average of the amount of misregistration using read images read from a plurality of sheets Sh on which images are continuously formed at the time when print output is completed for a plurality of sheets Sh. Calculate the value. Then, the control unit 50 uses the moving average value to perform feedback correction of the position of the image formed on the sheet Sh by the image forming unit 30 . The operator can arbitrarily change the setting of the data points of the positional deviation amount used for calculating the moving average value through the operation display unit 13 .

Also, the control unit 50 receives an operation signal from the operation display unit 13 and performs control according to the operation signal. Further, the control unit 50 outputs a display signal to the operation display unit 13, and the operation display unit 13 displays various setting screens for inputting various operation instructions and setting information and operation screens for displaying various processing results. display on the panel.

The storage unit 52 stores parameters used when the CPU 501 of the control unit 50 executes the program, data obtained by executing the program, and the like. For example, the storage unit 52 stores information such as image forming conditions for each density level. A program executed by the CPU 501 may be stored in the storage unit 52 . A non-volatile storage medium such as a HDD (Hard Disk Drive), an SSD (Solid State Drive), or a non-volatile memory is used for the storage unit 52, for example. The storage unit 52 stores programs for operating the image forming system 1 in addition to an OS (Operating System) and various parameters. The ROM 502 and the storage unit 52 record programs and data necessary for the operation of the CPU 501, and are examples of computer-readable non-transitory storage media storing programs executed by the image forming system 1. used as

FIG. 3 is a graph showing image misalignment and feedback correction targets. The horizontal axis of this graph represents the amount of deviation [mm] in the X direction (direction perpendicular to the paper feeding direction) (referred to as "X image deviation"), and the vertical axis represents the deviation in the Y direction (paper feeding direction). (referred to as “Y image shift”) amount [mm].

The graph shown in FIG. 3 indicates how much the read image read by the reading unit 45 deviates from the reference image each time printing is performed. In the figure, the positional deviation point representing the amount of deviation of the image position from the reference image is identified by the notation of (X image deviation, Y image deviation). The black dots in the drawing represent misalignment points of the image formed on the sheet Sh when there is no sheet conveyance abnormality. In addition, the x mark in the figure represents the positional deviation point of the image formed on the sheet Sh when there is an abnormality in the sheet conveyance.

In FIG. 3, the moving average value of the positional deviation of the images is represented, for example, around (1.0, 1.0). Based on this moving average value, the control unit 50 performs feedback correction for the position of the image formed on the sheet Sh. For example, in subsequent printing processes, the origin (0, 0) of the image formed on the sheet Sh is moved to the moving average value (1.0, 1.0).

In the shaded area above the dashed-dotted line connecting (5.0, 0.0) and (0.0, 5.0), the paper Sh is detected as waste (referred to as a "waste detection area"). represents When at least one of the paper Sh and the image is of poor quality, it is called "waste", and the paper Sh on which waste occurs is also called "waste paper".

Conventionally, if there is an abnormality in paper transport and there is a misalignment point within the waste detection area, it has not been subject to feedback correction. Further, even if there is no abnormality in paper transport, if there is a position deviation point within the waste detection area, it is not subject to feedback correction. In either case, the sheet Sh on which an image with a positional deviation point within the waste detection area is formed is discarded as waste paper.

On the other hand, even if there is an abnormality in paper transport, if there is no misalignment point within the waste detection area, the paper Sh on which the image is formed is not discarded as waste paper. For example, this corresponds to the sheet Sh at the point of misalignment indicated by an x marked with a circle of a dashed line in the figure. The x-marked points represent misalignment points of the sheet Sh that does not satisfy the prescribed conditions. For example, the paper Sh may not be of the type originally used, or the water content of the paper Sh may be high, and the image may blur and become unclear. Conventionally, however, even with such a sheet Sh, the amount of positional deviation of the image is not within the waste detection area, so the amount of positional deviation has been subject to feedback correction.

In the control unit 50 according to the present embodiment, even if there is no misalignment point within the waste detection area, if the paper state is abnormal, the amount of misalignment is not subject to feedback correction. The control unit 50 can treat the sheet Sh determined to be in an abnormal state as a waste sheet and discharge the sheet Sh to the discharge tray 48, for example.

Here, the control unit 50 detects the positional deviation of the formation positions of the plurality of read images read from the plurality of sheets Sh to be printed out, and the image forming unit 30 performs the sheet Sh from the next time onward during continuous printing. feedback correction of the position of the image to be formed. Here, the control unit 50 uses a combination of the physical property values of the sheet Sh detected by the sensor and the transport state in the process of determining whether feedback correction can be performed.

If the control unit 50 determines that the paper state does not satisfy the preset condition even if the positional deviation amount is within the target range of the feedback correction, the control unit 50 sets the positional deviation amount as the target of the feedback correction. do not do. In other words, the control unit 50 may not subject the image positional deviation amount to the feedback correction even if the image positional deviation amount obtained from the read image after the printout is not within the waste detection area shown in FIG.

As described above, the positional deviation amount indicated by encircling the x mark with the dashed-dotted line in FIG. and not. In this way, the control unit 50 determines that the sheet information and state information detected during at least one of the transport path 21, the reverse transport path 22, and the transport path 41 do not satisfy the preset conditions. In this case, the positional deviation amount of the sheet Sh for which the sheet information and the state information are detected is not subject to feedback correction.

FIG. 4 is a table defining conditions for determining whether or not to subject the sheet transport state and the sheet physical property value to feedback correction.

In this list, items, judgment condition examples (threshold values), judgment condition definitions, and cases exceeding the judgment conditions (examples) are used as column names, and paper transport states and paper physical property values are used as row names. The items of the paper transport state include the items of bending, deviation, transport time, and amount of curl of the paper Sh that can be detected by the transport state detection sensor 62 . Items of paper physical properties include stiffness, air permeability, smoothness, thickness, and moisture content. The operator can change each item shown in FIG. 4 to any condition or threshold through the operation display unit 13 .

(Paper feeding state)
First, conditions for determining the paper transport state will be described. It is assumed that the transport state detection sensor 62 is installed at one of the installation positions P1 to P4.
If the sheet Sh is bent during transport, the allowable threshold is within ±1% of the reference value. The control unit 50 controls the difference in the time it takes for both ends of the sheet Sh to pass through the detection range of the transport state detection sensors 62 installed at both ends in the X direction (direction perpendicular to the paper transport direction) and the transport speed of the sheet Sh. Based on this, the amount of bending of the sheet Sh is calculated. The skew judgment condition definition defines the amount of sheet inclination with respect to the transport direction. In other words, the amount of inclination within ±1% with respect to the conveying direction of the sheet Sh is allowed. Here, as a case where the determination condition is exceeded, for example, a situation in which the sheet Sh is caught or slipped on the transport path and a transport abnormality occurs is assumed.

If the sheet Sh is skewed while being conveyed, the allowable threshold is within ±0.5 mm of the reference value. The controller 50 calculates the amount of deviation of the sheet Sh based on the leading edge position of the sheet Sh detected by the transport state detection sensor 62 (for example, an in-line sensor). The deviation determination condition definition defines the amount of deviation of the paper in the transport direction. In other words, the amount of deviation within ±0.5 mm with respect to the conveying direction of the sheet Sh is allowed. An example of exceeding the judgment condition is the same as the case of bending.

For the transport time of the paper Sh, the allowable threshold is within ±10% of the reference value. The control unit 50 calculates the transport time based on the passing time of the leading edge of the sheet Sh detected by the transport state detection sensor 62 . The determination condition definition of the transportation time defines the variation of the transportation time in the section defined on the transportation path. In other words, the transport time allows for variation in time within ±10% of the reference value with respect to the interval transport time of the sheet Sh. An example of exceeding the judgment condition is the same as the case of bending.

For the amount of curl of the sheet Sh, the permissible threshold is within 30 mm. The control unit 50 calculates the difference in the height of the leading edge of the sheet Sh detected by the transport state detection sensor 62 from the reference height as the amount of curl. The curl amount determination condition definition defines the deformation curl amount of the sheet Sh. That is, the curl amount within 30 mm is the allowable curl amount for the flat sheet Sh before curling. Examples of cases in which the judgment condition is exceeded include the use of paper Sh with poor paper characteristics, the poor storage condition of paper Sh, or an error in the type of paper Sh set by the operator in the main body (image forming apparatus 2). Either of the following cases can be mentioned.

(Paper physical properties)
Next, conditions for judging paper physical property values will be described. For example, the control unit 50 acquires physical property values of the sheet Sh detected by the media sensor 61 installed at the installation position P1. After the image is formed on the surface of the paper Sh (an example of the first surface), the physical property values of the paper Sh change from the original values due to the pressure and heat applied when the image is fixed on the paper Sh. .

For the stiffness of the sheet Sh, the allowable threshold is within ±10% of the reference value. The determination condition definition of the stiffness defines the variation of the paper Sh to be passed with respect to the reference value. That is, the stiffness allows a change of ±10% with respect to the reference value of the sheet Sh. An example of exceeding the judgment condition is the same as the curl amount.

For the air permeability of the sheet Sh, the allowable threshold is within ±10% of the reference value. The determination condition definition of the air permeability prescribes the variation of the paper Sh to be passed from the reference value. That is, the air permeability allows a change of ±10% with respect to the reference value of the paper Sh. An example of exceeding the judgment condition is the same as the curl amount.

In the following, if the smoothness of the sheet Sh is the same, the allowable threshold value is within ±10% of the smoothness reference value. For the thickness of the sheet Sh, the allowable threshold is within ±50 μm of the thickness reference value. For the moisture content of the sheet Sh, the allowable threshold is within ±50 μm of the moisture content reference value.

The control unit 50 determines whether feedback correction is possible based on one sheet state or a combination of a plurality of sheet states. When the control unit 50 determines whether or not the feedback correction is possible based on only one paper state, one of the items listed in each row of the list in FIG. 4 is selected. Further, when the control unit 50 determines whether or not feedback correction is possible based on a combination of a plurality of paper states, at least one item is selected for each item of the paper transport state and the paper physical property value in the list of FIG. be done. It should be noted that a plurality of items selected from the items of paper transport state may be combined, or a plurality of items selected from the items of paper physical property values may be combined.

As described above, it is desirable that the media sensor 61 detects the physical property values of the paper Sh before an image is formed and fixed on the surface of the paper Sh. However, even after the image is formed and fixed on the front surface of the sheet Sh, the control unit 50 causes the media sensor 61 to detect the image before the image is formed on the back surface (an example of the second surface) of the sheet Sh. The state of the sheet Sh may be determined based on the electrical resistance value of the sheet Sh. As the image is formed and fixed on the surface of the paper Sh, the water in the paper Sh is lost, and the electric resistance value of the paper Sh changes. Therefore, the control unit 50 can calculate the amount of change in the electrical resistance value of the sheet Sh and determine whether the physical property values of the sheet Sh are appropriate.

<Processing example of image forming system>
Next, an example of processing of the image forming system 1 will be described.
FIG. 5 is a flow chart showing an example of processing of the image forming system 1 .

First, the operator sets the paper brand of the paper Sh to be used in the job to be executed by the image forming system 1 through the operation display unit 13 . When the paper brand is set, the control unit 50 reads each reference value of the paper physical property value and the paper conveyance state linked to the paper brand stored in the storage unit 52, and determines each reference value. (S1).

Next, the control unit 50 determines whether or not the number of sheets specified in the job has been printed (S2). When the control unit 50 determines that the specified number of sheets have been printed (YES in S2), the processing ends. On the other hand, when the control unit 50 determines that printing of the prescribed number of sheets has not been completed (NO in S2), it starts printing (S3).

After step S3, the controller 50 acquires the paper physical property values of the paper Sh (S4). At this time, the control unit 50 acquires from the media sensor 61 the paper physical property values measured by the media sensor 61 installed at the installation position P1. Then, the control unit 50 determines whether or not the paper physical property values are out of the range of the reference values shown in the judgment condition examples based on the paper physical property value items in the list shown in FIG. At this time, if the control unit 50 determines that the paper physical property value is NG (for example, out of the range of the reference values), it sets a flag 1 in the flag area provided in the RAM 503 corresponding to the paper physical property value. On the other hand, the control unit 50 does not set the flag 1 when determining that the paper physical property values are OK (for example, within the range of the reference values).

Next, the control unit 50 acquires the paper transport state of the paper Sh (S5). At this time, the control unit 50 acquires from the transport state detection sensor 62 the sheet transport state measured by the transport state detection sensor 62 installed at either or both of the installation positions P2 and P3. Then, the control unit 50 determines whether or not the paper transport state is out of the range of the reference value shown in the determination condition example based on the item of the paper transport state in the list shown in FIG. At this time, if the control unit 50 determines that the paper transport state is NG (for example, out of the range of the reference value), it sets a flag 2 in the flag area provided in the RAM 503 corresponding to the paper transport state. On the other hand, when the control unit 50 determines that the paper transport state is OK (for example, within the range of the reference value), the flag 2 is not set.

Next, the control unit 50 prints out the paper Sh on which the image is formed by the image forming unit 30 (S6). Next, the reading unit 45 reads the output image of the printed sheet Sh and outputs the read image to the control unit 50 . Then, the control unit 50 measures the positional deviation between the read image and the reference image, and determines whether the positional deviation of the printed sheet Sh is included in the waste detection area in FIG. 3 (S7).

When the positional deviation of the printed sheet Sh is included in the waste detection area in FIG. 3, the control unit 50 detects that the sheet Sh is waste (S8). The control unit 50 instructs the inspection device 3 to discharge the paper Sh whose waste has been detected to the paper discharge tray 48 . After detecting that the paper Sh is damaged in step S8, the control unit 50 may return to step S2 and determine again whether or not printing is finished.

On the other hand, when the positional deviation of the printed sheet Sh is not included in the waste detection area in FIG.

Then, when the flags 1 and 2 are set in steps S4 and S5, the control unit 50 determines that the feedback correction is NG, that is, the positional deviation is not targeted for feedback correction, and the feedback correction based on this positional deviation is not performed. do. "Flag 1: Present" in the drawing indicates that Flag 1 is set, and "Flag 2: Present" indicates that Flag 2 is set. In addition, although "flag 1: present and flag 2: present" is described in the drawing, the control unit 50 determines that the feedback correction is NG even in the case of "flag 1: present or flag 2: present". do. Then, the control unit 50 returns the process to step S2 without performing feedback correction based on the positional deviation.

On the other hand, if the flags 1 and 2 are not set in steps S4 and S5, the control unit 50 determines that the feedback correction is OK, that is, the positional deviation is the object of the feedback correction, and the feedback correction based on the positional deviation is performed. . "Flag 1: None" shown in the figure means that the flag 1 is not set. Similarly, "flag 2: none" means that flag 2 is not set. In the case of "flag 1: none and flag 2: none", the control unit 50 performs feedback correction of the image formed on the sheet Sh by the image forming unit 30 based on the positional deviation (S10). After that, the control unit 50 returns the processing to step S2.

After step S9 or S10, the process returns to step S2, and if printing has not ended (NO in S2), printing continues. Therefore, the print start process of step S3 is skipped, and the process is performed from step S4.

Here, the flowchart shown in FIG. 5 represents the process of acquiring the paper physical property values and the paper transport state. For example, when only one item shown in FIG. 4 is selected for the paper physical property value or the paper transport state and compared with the reference value, flag 1 or flag 2 of the paper physical property value or paper transport state corresponding to the selected item is used. Therefore, only either step S4 or S5 may be executed. Then, in the feedback correction determination processing in step S9, it is determined whether or not flag 1 or flag 2 of the paper physical property value or the paper transport state corresponding to the selected item is present. Further, if there is no paper physical property value or flag 1 or flag 2 of the paper transport state corresponding to the selected item, the feedback correction in step S10 is performed.

Note that the control unit 50 is configured to perform a process (S4) for acquiring the paper physical property values and a process (S5) for acquiring the paper transport state before printing out in step S6. However, a process of acquiring the paper transport state may be added after the print output. For example, the transport state detection sensors 62 installed at the installation positions P2 to P4 shown in FIG. 1 can acquire the paper transport state after print output.

Further, since the process shown in FIG. 5 is performed once for the front surface of the sheet Sh and once for the back surface, steps S5 and S6 may be looped once. In this case, in the first processing of steps S4 and S5, after the control unit 50 acquires the paper physical property values and the paper transport state of the paper Sh before the image is printed on the surface, the surface of the paper Sh is printed out. be done. Next, in the second process of step S5, after the control unit 50 acquires the paper transport state of the sheet Sh before the image is printed on the back side, the back side of the sheet Sh is printed out. After that, the loop may be exited and the determination processing of steps S7 and S8 may be performed based on the read images of the front and back sides of the sheet Sh.

FIG. 6 is a list showing differences between the conventional technology and the technology according to the present embodiment.

This list has items of waste detection, paper conveyance abnormality, conventional technology, and technology according to the present embodiment.
The waste detection item stores whether or not there is waste detection.
The paper transport error item stores whether or not there is a paper transport error.
In the items of the conventional technology and the technology according to the present embodiment, one of feedback correction (marked with ◯) and feedback correction not performed (marked with x) is stored.

It explains in order from the top of the list.
In the case where there is detection of waste and there is an abnormality in paper conveyance, neither the conventional technique nor the technique according to the present embodiment performs feedback correction.

In the case where there is detection of waste and there is no abnormality in paper transport, neither the conventional technique nor the technique according to the present embodiment performs feedback correction. However, in the technique according to the present embodiment, whether or not feedback correction is possible may be determined based only on the presence or absence of a paper conveyance abnormality. In this case, as indicated by the addition of a circle mark in parentheses to the item of the technique according to the present embodiment, it is possible to indicate that feedback correction is required even when waste detection is present and there is no paper conveyance error.

In the prior art, feedback correction is performed when there is no detection of paper loss and there is an abnormality in paper conveyance. For this reason, if the feedback correction is performed without noticing the paper conveyance abnormality, the image may be formed at a position that is greatly deviated from the reference position when the paper conveyance becomes normal. On the other hand, in the technique according to the present embodiment, feedback correction is not performed when there is a paper transport error even if there is no waste detection. Therefore, when the paper conveyance becomes normal, the misalignment of the image formed on the paper Sh does not increase.

In the case where there is no detection of waste and no abnormality in paper conveyance, both the conventional technique and the technique according to the present embodiment perform feedback correction. That is, if the positional deviation of the read image with respect to the reference image is large, the positional deviation of the image formed on the sheet Sh is feedback-corrected.

The control unit 50 of the image forming system 1 according to the embodiment described above calculates the positional deviation amount of the image and performs the feedback correction of the image position in real time. Determine whether the conditions are met. When the control unit 50 determines that the paper state does not satisfy the condition, the image positional deviation amount is not subject to feedback correction. In this way, even if a sudden abnormality occurs in the sheet Sh unrelated to the original performance of the image forming apparatus 2, it is possible to provide the image forming system 1 that does not perform unnecessary feedback correction.

Here, the control unit 50 uses at least one of the paper physical property value and the paper transport state as the paper state of the paper Sh to determine whether feedback correction is possible. At this time, the control unit 50 confirms whether the paper physical property values of the paper Sh before image formation satisfy the determination conditions. Further, the control unit 50 confirms whether the paper transport state of the paper Sh before and after image formation satisfies the determination condition. If the control unit 50 determines that at least one of the paper physical property value and the paper transport state does not satisfy the condition even if the misalignment of the read image is not within the waste detection area (see FIG. 3), , no feedback correction. Therefore, it is possible to avoid deterioration of the image quality of the image formed on the sheet Sh when the sheet condition returns to normal.

Also, the paper transport state and paper physical property value thresholds shown in FIG. 4 can be set to appropriate values for each image forming system 1 used by the operator. Therefore, based on the paper type of the paper Sh set in the job, the installation environment of the image forming system 1, and the quality requirements, the operator sets a judgment reference value higher than the default value (for example, the threshold value for bending is set to ±0.8%). ) can be set. Further, the operator can arbitrarily change the combination of the sheet transport state and the sheet physical property value that are not subject to feedback correction.

[Modification]
An image forming system 1 shown in FIG. 1 has a configuration in which an image forming apparatus 2 and an inspection apparatus 3 are combined. However, an image forming system in which the configuration of the inspection device 3 is incorporated in the printer section 10 of the image forming device 2 may be used. In this case, the image forming apparatus 2 includes the transport paths 41, 42, 43, the switching unit 44, the reading units 45a, 45b, the colorimeters 46a, 46b, the paper discharge tray 47, 48. Even in the image forming apparatus 2 having such a configuration, the control unit 50 can determine whether or not to feedback-correct the positional deviation of the image based on the sheet state of the sheet Sh described above.

Further, the information on the sheet state acquired by the control unit 50 is not usually notified to the operator. However, if the control unit 50 determines NG in step S9, the control unit 50 displays the operation display according to the increase in the ratio of the number of sheets Sh not subjected to feedback correction to the total number of sheets Sh printed out. A warning may be displayed on the unit 13 or the like, or the operation of the image forming system 1 may be stopped. At this time, the control unit 50 may notify the operator that the feedback correction was not performed and the content of the physical property value or the paper transport state that did not satisfy the conditions.

In addition, in order for the operator to grasp the operation status of the image forming system 1, the control unit 50 stores the fact that the feedback correction was not performed and the content of the physical property value or the paper transport state that did not satisfy the conditions as log data in the storage unit 52. can be saved to Further, the control unit 50 uses the communication function of the communication I/F unit 51 to transmit log data to the PC 70, so that the operator using the PC 70 can grasp the state of the image forming system 1. . Also, the log data may be collected by a monitoring center provided at a remote location, and the contents may be confirmed by an operator of the monitoring center.

It should be noted that the present invention is not limited to the above-described embodiment, and of course, various other applications and modifications can be made without departing from the gist of the present invention described in the claims.
For example, the above-described embodiments are detailed and specific descriptions of the system configuration for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. Moreover, it is possible to add, delete, or replace a part of the configuration of this embodiment with another configuration.
In addition, the control lines and information lines indicate those considered to be necessary for explanation, and not all the control lines and information lines are necessarily indicated on the product. In practice, it may be considered that almost all configurations are interconnected.

DESCRIPTION OF SYMBOLS 1... Image forming system, 2... Image forming apparatus, 3... Inspection apparatus, 10... Printer part, 13... Operation display part, 21... Conveyance path, 22... Reverse conveyance path, 30... Image forming part, 41 to 43... Conveyance Path 45 Reading unit 50 Control unit 61 Media sensor 62 Conveyance state detection sensor P1 to P4 Installation position

Claims (11)

An image forming system that performs feedback correction for correcting the position of an image formed on a plurality of recording materials based on a positional deviation amount of images formed on a plurality of recording materials by an image forming unit in succession with respect to a reference image,
a recording material state detection unit that detects a recording material state of the recording material conveyed on the conveying path;
an image forming system comprising: a control unit that does not subject the positional deviation amount to the feedback correction when it is determined that the state of the recording material does not satisfy a preset condition. If the control unit determines that the state of the recording material does not satisfy a preset condition even if the amount of positional deviation is within the range to be subjected to the feedback correction, the controller determines the amount of positional deviation as feedback. 2. The image forming system according to claim 1, which is not subject to correction. The image forming unit for forming an image on the recording material conveyed by the conveying path,
3. The image forming system according to claim 2, wherein at least one of the one or more recording material state detection units installed in the conveying path is installed upstream of the image forming unit. 4. The image forming system according to claim 3, wherein the control unit determines whether or not the feedback correction is applicable after calculating the positional deviation amount based on the read image of the image formed on the recording material. 5. The image forming system according to claim 4, wherein the control unit determines whether or not the feedback correction is applicable based on one recording material state or a combination of a plurality of recording material states. The recording material state detection unit is installed on the upstream side of the image forming unit and on the conveying path from the recording material supply unit that supplies the recording material to the image forming unit, and detects physical property values of the recording material. 6. The image forming system according to claim 5, which is a physical property value sensor for sensing. 7. The physical property value sensor according to claim 6, wherein the physical property value sensor detects at least one physical property value among stiffness, air permeability, smoothness, thickness, moisture content, and resistance value of the recording material as the state of the recording material. imaging system. As the conveying path, a first conveying path from a recording material supply unit that supplies the recording material to the image forming unit, and a fixing unit that fixes an image formed on the recording material to discharge the recording material. a second conveying path, a third conveying path from when the image is formed on the first surface of the recording material by the image forming unit until the image is formed on the second surface of the recording material, and the image A fourth transport path is provided until the recording material on which is formed is discharged,
The recording material state detection unit is provided in at least one of the first conveying path, the second conveying path, the third conveying path, and the fourth conveying path, and detects the conveying state of the recording material. The image forming system according to any one of claims 4 to 7, wherein the image forming system is a transport state detection sensor. 9. The image forming system according to claim 8, wherein the conveying state detection sensor detects at least one conveying state of bending, deviation, conveying time, and curl amount of the recording material as the recording material state. 8. The control unit performs the feedback correction based on a moving average value of the displacement amount calculated from the read images read from a plurality of the recording materials on which the images are continuously formed. The image forming system according to any one of . An image formed by an image forming system that performs feedback correction for correcting the position of an image formed on a plurality of recording materials based on the amount of positional deviation of the images formed on the recording materials by an image forming unit from a reference image. In the forming method,
a process in which a recording material state detection unit provided in the image forming system detects a recording material state of the recording material being conveyed along a conveying path;
an image forming method including, when a control unit provided in the image forming system determines that the state of the recording material does not satisfy a preset condition, a process in which the amount of positional deviation is not subject to the feedback correction. .

Images