Image forming device

Abstract

To provide an image forming apparatus that stably maintains the high image quality of a reference image used in inspection of a printed material.SOLUTION: An image forming apparatus 101 comprises: a printer 107 that prints an image on a sheet; and an inspection device 108 that performs inspection of an image of a printed material to be inspected formed on the sheet by the printer 107. The inspection device 108 includes an image reading unit 235 that reads an image formed on the sheet by the printer 107, and a memory 234 that stores a result of reading of a sheet performed by the image reading unit 235, the sheet being formed with a reference image to be an inspection reference for an image to be inspected, and the inspection device compares the result of reading of the reference image stored in the memory 234 with the image of the printed material to perform inspection. The printer 107 includes a CPU 222 that adjusts the image quality of an image to be formed before forming the reference image on the sheet.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus having an inspection function for determining whether an image formed on a printed matter is good or bad. [Background technology]

[0002] Some image forming systems equipped with electrophotographic image forming devices use an inspection device that has the function of determining whether an image formed on a printed matter (printed image) is normal or not. In this image forming system, printed matter determined to have an abnormal printed image is discharged to an escape tray that is different from the discharge tray to which printed matter determined to be normal is discharged, and reprinting is automatically performed. This allows the user to obtain high-quality printed matter without performing any special work.

[0003] Patent Document 1 discloses a technique for inspecting printed matter. In this inspection technique, an image forming device first prints an image that a user wants to print on a recording medium such as a sheet as a reference image. Next, the image forming device reads images from the sheet on which the reference image is printed and from the printed matter to be inspected. The image forming device compares the read reference image with the printed image of the printed matter to be inspected. If the comparison results in a mismatch, the image forming device determines that the printed matter is not normal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-132661 A Summary of the Invention [Problem to be solved by the invention]

[0005] In this way, the reference image serves as the standard of judgment when inspecting the printout being inspected. If the quality of the reference image deteriorates, the quality of the printed image of the printout judged to be normal will also deteriorate. The quality of the image printed on the sheet is affected by the condition of the components of the image forming device. For example, if the inside of the image forming device is dirty, this dirt will adhere to the sheet and deteriorate the image quality. Naturally, the quality of the reference image will deteriorate when it is printed.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In view of the above problems, a primary object of the present invention is to provide an image forming apparatus that stably maintains high image quality of a reference image used when inspecting printed matter. [Means for solving the problem]

[0007] The image forming apparatus of the present invention comprises a printing means for printing an image on a sheet, an inspection means for inspecting an image of a printed matter to be inspected formed on the sheet by the printing means, and a control means, wherein the inspection means comprises a reading means for reading the image formed on the sheet by the printing means, and a storage means for storing a reading result by the reading means of a sheet on which a reference image serving as an inspection standard for the image to be inspected is formed, and the inspection is performed by comparing the reading result of the reference image stored in the storage means with the image of the printed matter, The control means Reference image generation mode was set If it is determined that the reference image generation mode is set Depending on Before forming the reference image, The method is characterized in that, when an adjustment process for forming an image is performed by the printing means, the reference image is formed on a sheet by the printing means after the adjustment process is performed, the reference image formed on the sheet is read by the reading means, and reference data is stored in the storage means, and the inspection is performed after the formation of the reference image, the printing means forms an image of the inspection object, the reading means reads the inspection object, and the inspection means performs the inspection by comparing the reference image stored in the storage means with the image of the inspection object read. Effect of the Invention

[0008] According to the present invention, it is possible to obtain a reference image whose image quality is stably maintained at a high level. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of an image processing system. [Diagram 2] system configuration diagram. [Diagram 3] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus. [Figure 4] 4 is a flowchart showing a printing process. [Diagram 5] 4 is a flowchart showing a printing process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

[0011] (Image forming system) 1 is a configuration diagram of an image processing system including an image forming apparatus according to this embodiment. The image processing system includes an image forming apparatus 101 and an external controller 102. The image forming apparatus 101 is, for example, a multifunction peripheral (MFP), etc. The external controller 102 is, for example, an image processing controller, a digital front end (DFE), a print server, etc.

[0012] The image forming apparatus 101 and the external controller 102 are communicatively connected via an internal LAN (Local Area Network) 105 and a video cable 106. The external controller 102 is connected to a client PC (Personal Computer) 103 via an external LAN 104. The external controller 102 obtains a print instruction (print job) from the client PC 103.

[0013] A printer driver having a function of converting print data into a print description language that can be processed by the external controller 102 is installed in the client PC 103. A user can issue a print instruction from various applications via the printer driver. The printer driver transmits a print instruction including print data to the external controller 102 based on an instruction from the user. The external controller 102 accepts a print instruction including print data from the client PC 103, performs data analysis and rasterization processing, and instructs the image forming apparatus 101 to print (form an image) based on the print data.

[0014] The image forming apparatus 101 is configured by connecting a plurality of devices having different functions including a printing apparatus 107, and is capable of complex printing processes such as bookbinding. The image forming apparatus 101 of this embodiment includes a printing apparatus 107, an inspection apparatus 108, and a finisher 109. The printing apparatus 107 forms an image on a sheet fed from a paper feed unit provided at the bottom of the main body by using a developer (e.g., toner). The printing apparatus 107 forms images of yellow (Y), magenta (M), cyan (C), and black (K). A full-color image in which images of each color are superimposed is formed on the sheet. The sheet on which the image is formed is transported from the printing apparatus 107 to the finisher 109 via the inspection apparatus 108. The inspection apparatus 108 judges whether the printed image is normal or not by comparing an image (printed image) printed on a sheet (printed material) by the printing apparatus 107 with a reference image registered in advance. The reference image becomes the inspection standard for the printed image. The finisher 109 separates printed matter determined by the inspection device 108 to have a normal image formed thereon from printed matter determined to have an abnormal image formed thereon. Printed matter determined to have a normal image formed thereon is stacked in the finisher 109, and printed matter determined to have an abnormal image formed thereon is discharged from the finisher 109.

[0015] In this image processing system, an external controller 102 is connected to an image forming apparatus 101, but the external controller 102 is not essential. For example, the image forming apparatus 101 may be configured to directly receive a print instruction including print data from a client PC 103 via an external LAN 104. In this case, the image forming apparatus 101 performs the data analysis and rasterization processing that are performed by the external controller 102. In other words, the image forming apparatus 101 and the external controller 102 may be configured as one unit.

[0016] (System Configuration) 2 is a system configuration diagram for controlling the operation of the image processing system. Here, controllers for controlling the operation of the image forming apparatus 101, the external controller 102, and the client PC 103 will be described.

[0017] ·Printing device The printing device 107 includes a communication interface (I / F) 217, a LAN I / F 218, and a video I / F 220 for communicating with other devices. The printing device 107 includes a CPU (Central Processing Unit) 222, a memory 223, and a storage 221 for controlling the operation of the printing device 107. The printing device 107 includes an exposure unit 227, an image creating unit 228, a fixing unit 229, and a paper feed unit 230 for printing (image formation). The printing device 107 includes an operation unit 224 and a display unit 225 as user interfaces. These components are connected to each other via a system bus 231 so as to be able to communicate with each other.

[0018] The communication I / F 217 is connected to the inspection device 108 and the finisher 109 via a communication cable 249, and controls communication between these devices. When the printing device 107 operates in cooperation with the inspection device 108 or the finisher 109, data is transmitted and received via the communication I / F 217. The LAN I / F 218 is connected to the external controller 102 via the internal LAN 105, and controls communication with the external controller 102. The printing device 107 receives print data and the like representing settings at the time of printing from the external controller 102 via the LAN I / F 218. The video I / F 220 is connected to the external controller 102 via a video cable 106, and controls communication with the external controller 102. The printing device 107 receives image data and the like representing an image to be formed from the external controller 102 via the video I / F 220.

[0019] The CPU 222 comprehensively controls image processing and printing by executing computer programs stored in the storage 221. The memory 223 provides a work area when the CPU 222 executes various processes. When performing image formation processing, the CPU 222 controls an exposure unit 227, an image forming unit 228, a fixing unit 229, and a paper feed unit 230. The CPU 222 counts the operation time and the number of times these components used in image formation are operated, and stores the count values ​​in the memory 223. The CPU 222 can determine the aging status of each component by checking the count values.

[0020] The exposure unit 227 uniformly charges the surface of the photosensitive drum, which is an image carrier, and irradiates the charged surface of the photosensitive drum with laser light based on image data. The exposure unit 227 charges the surface of the photosensitive drum to a uniform negative potential. The exposure unit 227 outputs laser light using a laser driver (not shown), and scans the uniformly charged surface of the photosensitive drum with the laser light while adjusting the reflection angle of the laser light using a rotating polygon mirror. The potential of the photosensitive drum at the position irradiated with the laser light fluctuates, and an electrostatic latent image is formed on the surface. Four photosensitive drums are provided corresponding to four colors: yellow (Y), magenta (M), cyan (C), and black (K). Electrostatic latent images of different colors are formed on the four photosensitive drums.

[0021] The image creating unit 228 transfers the toner image formed on the photosensitive drum onto a sheet. The image creating unit 228 includes a developing unit, a transfer unit, a toner supply unit, and the like. The developing unit contains toner, and forms a toner image by attaching negatively charged toner from a developing cylinder to an electrostatic latent image formed on the surface of the photosensitive drum. Four developing units are provided corresponding to four colors: yellow, magenta, cyan, and black. The developing units make the electrostatic latent image on the photosensitive drum visible with toner of the corresponding color. When the amount of toner inside the developing unit becomes insufficient due to the formation of a toner image, the toner supply unit replenishes the toner.

[0022] The transfer unit has an intermediate transfer belt, which is an image carrier, and transfers a toner image from each photosensitive drum to the intermediate transfer belt. A primary transfer roller is provided at a position facing the photosensitive drum across the intermediate transfer belt. A positive potential is applied to the primary transfer roller, so that the toner images from each of the four photosensitive drums are transferred to the intermediate transfer belt in a superimposed manner. As a result, a full-color toner image is formed on the intermediate transfer belt. The toner image formed on the intermediate transfer belt is transferred to a sheet by a secondary transfer roller. A positive potential is applied to the secondary transfer roller, so that the full-color toner image is transferred from the intermediate transfer belt to the sheet.

[0023] The fixing unit 229 fixes the transferred toner image onto the sheet. The fixing unit 229 applies heat and pressure to the toner image on the sheet to melt and fix the toner image to the sheet. The paper feed unit 230 includes rollers such as a conveying roller and various sensors on the conveying path, and controls the sheet feeding operation.

[0024] The operation unit 224 is an input device that accepts various setting inputs and operation instructions from a user. The operation unit 224 is, for example, various input keys or a touch panel. The display unit 225 is an output device that displays setting information of the image forming apparatus 101 and the processing status (status information) of a print job.

[0025] Inspection equipment The inspection device 108 includes a communication I / F 232, a CPU 233, a memory 234, an image reading unit 235, a display unit 236, an operation unit 237, and an image processing unit 250. These components are connected to each other via a system bus 238 so as to be able to communicate with each other. The communication I / F 232 is connected to the printing device 107 and the finisher 109 via a communication cable 249, and controls communication between the printing device 107 and the finisher 109. When the inspection device 108 operates in cooperation with the printing device 107 and the finisher 109, data is transmitted and received via the communication I / F 232. The CPU 233 performs various controls required for inspection according to a control program stored in the memory 234. In addition to the control program, a reference image used in the inspection process is stored in the memory 234.

[0026] The image reading unit 235 reads a print image from a sheet (printed matter) on which an image is formed by the printing device 107, based on an instruction from the CPU 233. The CPU 233 compares the print image read by the image reading unit 235 with a reference image that serves as a judgment criterion when inspecting the print object to be inspected and is stored in the memory 234, and judges whether the print object (printed image) is normal or not. The CPU 233 notifies the finisher 109 of the judgment result. The operation unit 237 is an input device that accepts instructions such as setting the inspection device 108 and registering the reference image. The operation unit 237 is, for example, various input keys or a touch panel. The display unit 225 is an output device that displays the inspection result by the inspection device 108, a setting screen, etc. The image processing unit 250 performs image processing such as gain adjustment of the image read by the image reading unit 235.

[0027] Finisher The finisher 109 is, for example, a large-capacity stacker. The finisher 109 includes a communication I / F 244, a CPU 243, a memory 246, and a paper discharge control unit 247. These components are connected to each other via a system bus 242 so that they can communicate with each other. The communication I / F 244 is connected to the printing device 107 and the inspection device 108 via a communication cable 249, and controls communication between the printing device 107 and the inspection device 108. When the finisher 109 operates in cooperation with the printing device 107 and the inspection device 108, data is transmitted and received via the communication I / F 244. The CPU 243 executes a control program stored in the memory 246 and performs various controls required for paper discharge. The CPU 243 of this embodiment performs paper discharge control of the printed matter based on the inspection judgment result by the inspection device 108. The memory 246 stores the control program. The memory 246 also provides a work area when the CPU 243 executes various processes. Based on an instruction from the CPU 243, the sheet discharge control unit 247 conveys the conveyed sheet to a stack tray or an escape tray, which will be described later.

[0028] External Controller The external controller 102 includes a LAN I / F 213, a LAN I / F 214, and a video I / F 215 for communicating with other devices. The external controller 102 includes a CPU 208, a memory 209, and a storage 210 for controlling the operation of the external controller 102. The external controller 102 includes a keyboard 211 and a display unit 212 as user interfaces. These components are connected to each other via a system bus 216 so as to be able to communicate with each other.

[0029] The LAN I / F 213 is connected to the client PC 103 via the external LAN 104, and controls communication with the client PC 103. The external controller 102 acquires print instructions and the like from the client PC 103 via the LAN I / F 213. The LAN I / F 214 is connected to the printing device 107 via the internal LAN 105, and controls communication with the printing device 107. The external controller 102 transmits print data and the like indicating settings and the like at the time of printing to the printing device 107 via the LAN I / F 214. The video I / F 215 is connected to the printing device 107 via the video cable 106, and controls communication with the printing device 107. The external controller 102 transmits image data and the like to the printing device 107 via the video I / F 215.

[0030] The CPU 208 executes computer programs stored in the storage 210 to comprehensively perform processes such as receiving print data acquired from the client PC 103, RIP processing, and transmitting the print data to the image forming apparatus 101. The memory 209 provides a work area when the CPU 208 executes various processes. The keyboard 211 is an input device that accepts input of various settings and operation instructions from the user. The display unit 212 is an output device that displays information such as applications executed by the external controller 102 as still images and moving images.

[0031] Client PC The client PC 103 includes a CPU 201, a memory 202, a storage 203, a keyboard 204, a display unit 205, and a LAN I / F 206. These components are connected via a system bus 207 so as to be able to communicate with each other.

[0032] The CPU 201 controls the operation of the client PC 103 by executing a computer program stored in the storage 203. In this embodiment, the CPU 201 creates print data and transmits a print instruction. The memory 202 provides a work area for the CPU 201 to execute various processes. The keyboard 204 and the display unit 205 are user interfaces. The keyboard 204 is an input device that accepts instructions from a user. The display unit 205 is an output device that displays information such as an application executed by the client PC 103 as a still image or a moving image. The LAN I / F 206 is connected to the external controller 102 via the external LAN 104 and controls communication with the external controller 102. The client PC 103 transmits a print instruction or the like to the external controller 102 via the LAN I / F 206.

[0033] The external controller 102 and the image forming apparatus 101 are connected by an internal LAN 105 and a video cable 106, but any other configuration is acceptable as long as data necessary for printing can be transmitted and received, and for example, the connection may be made by only a video cable. Each of the memory 202, memory 209, memory 223, memory 234, and memory 246 may be a storage device for holding data and programs. For example, volatile RAM (Random Access Memory), non-volatile ROM (Read Only Memory), storage, USB (Universal Serial Bus) memory, etc. may be used as these memories.

[0034] (Configuration of Image Forming Apparatus) 3 is a configuration diagram of the image forming apparatus 101. A display unit 225 is provided on the upper part of the printing device 107. The display unit 225 displays information for the printing status and settings of the image forming apparatus 101. A sheet (printed material) on which an image is formed by the printing device 107 is inspected by an inspection device 108 provided in the subsequent stage, and is transported to a finisher 109.

[0035] The printing device 107 includes a plurality of paper feed decks 301, 302 and a conveying path 303 as the paper feed section 230. Each of the paper feed decks 301, 302 can accommodate different types of sheets. The top sheet of each of the paper feed decks 301, 302 is separated and fed to the conveying path 303. The printing device 107 includes image forming units 305y, 305m, 305c, and 305k for forming images as the exposure unit 227. The printing device 107 forms a color image. To this end, the image forming unit 305y forms a yellow (Y) image (toner image). The image forming unit 305y includes a photosensitive drum 304y on which a yellow toner image is formed. The image forming unit 305m forms a magenta (M) image (toner image). The image forming unit 305m includes a photosensitive drum 304m on which a magenta toner image is formed. The image forming unit 305c forms a cyan (C) image (toner image). The image forming unit 305c has a photosensitive drum 304c on which a cyan toner image is formed. The image forming unit 305k forms a black (K) image (toner image). The image forming unit 305k has a photosensitive drum 304k on which a black toner image is formed.

[0036] The printing device 107 includes, as the image creating unit 228, an intermediate transfer belt 308 onto which toner images are transferred from the image forming units 305y, 305m, 305c, and 305k, and a secondary transfer roller 309. An intermediate transfer body cleaner 318 is provided near the intermediate transfer belt 308. The intermediate transfer belt 308 rotates clockwise in the figure, and the toner images are transferred and superimposed on each other in the order of the image forming units 305y, 305m, 305c, and 305k. As a result, a full-color toner image is formed on the intermediate transfer belt 308.

[0037] A primary transfer roller 306y is provided corresponding to the image forming unit 305y. The primary transfer roller 306y transfers a yellow toner image from the photosensitive drum 304y to the intermediate transfer belt 308. A primary transfer roller 306m is provided corresponding to the image forming unit 305m. The primary transfer roller 306m transfers a magenta toner image from the photosensitive drum 304m to the intermediate transfer belt 308. A primary transfer roller 306c is provided corresponding to the image forming unit 305c. The primary transfer roller 306c transfers a cyan toner image from the photosensitive drum 304c to the intermediate transfer belt 308. A primary transfer roller 306k is provided corresponding to the image forming unit 305k. The primary transfer roller 306k transfers a black toner image from the photosensitive drum 304k to the intermediate transfer belt 308. In the following description, the suffixes y, m, c, and k of the image forming units 305y, 305m, 305c, and 305k, the photosensitive drums 304y, 304m, 304c, and 304k, and the primary transfer rollers 306y, 306m, 306c, and 306k will be omitted when there is no need to distinguish between colors.

[0038] Intermediate transfer belt 308 rotates to transport the toner image to secondary transfer roller 309. A sheet is transported to secondary transfer roller 309 in synchronization with the timing at which the toner image is transported to secondary transfer roller 309. Secondary transfer roller 309 transfers the toner image on intermediate transfer belt 308 to the transported sheet. Intermediate transfer body cleaner 318 cleans toner remaining on intermediate transfer belt 308 after transfer and toner images for image adjustment, for example, that are not transferred to the sheet.

[0039] The printing device 107 includes a first fixing device 311 and a second fixing device 313 as the fixing unit 229. The first fixing device 311 and the second fixing device 313 have the same configuration and fix the toner image to the sheet. For this purpose, the first fixing device 311 and the second fixing device 313 each include a pressure roller and a heating roller. The sheet is heated and pressurized by passing between the pressure roller and the heating roller, and the toner image is melted and pressed onto the sheet. The sheet that has passed the second fixing device 313 is conveyed to a conveying path 314. The second fixing device 313 is disposed downstream of the first fixing device 311 in the sheet conveying direction, and is used to add gloss to the image on the sheet that has been fixed by the first fixing device 311 and to ensure fixability. For this purpose, the second fixing device 313 may not be used depending on the type of sheet and the contents of the image forming process. In order to transport the sheet subjected to the fixing process by the first fixing device 311 without passing through the second fixing device 313, a transport path 312 is provided.

[0040] After the conveying path 314 and the conveying path 312 join, a conveying path 315 and an inversion path 316 are provided. When double-sided printing is instructed, the sheet is conveyed to the inversion path 316. The conveying direction of the sheet conveyed to the inversion path 316 is inverted by the inversion path 316, and the sheet is conveyed to a double-sided conveying path 317. The inversion path 316 and the double-sided conveying path 317 invert the side on which the image is formed (first side). The sheet is conveyed to the conveying path 303 by the double-sided conveying path 317, and passes through a secondary transfer roller 309 and a fixing unit 229, whereby an image is formed on the second side.

[0041] In the case of single-sided printing, or in the case of double-sided printing in which images are formed on both sides, the sheet is transported to a transport path 315. An inspection device 108 is provided downstream of the transport path 315 in the sheet transport direction. The sheet on which an image is printed by the printing device 107 is transported from the printing device 107 to the inspection device 108. The sheet discharged from the printing device 107 is a printed matter on which an image is printed.

[0042] The inspection device 108 includes a conveying path 323 and CIS (Contact Image Sensor) units 321 and 322. A display unit 236 is provided on the upper portion of the inspection device 108. The CIS units 321 and 322 are an example of the image reading unit 235, and are disposed opposite each other across the conveying path 323. The CIS unit 321 is an optical sensor that reads an image of the upper surface (second surface) of the printed material conveyed on the conveying path 323. The CIS unit 322 is an optical sensor that reads an image of the lower surface (first surface) of the printed material conveyed on the conveying path 323.

[0043] The inspection device 108 performs an inspection process in which the print image read from the printed material by the CIS units 321 and 322 is compared with a reference image to determine whether the print image is a normal image. The inspection device 108 displays the results of the inspection process on the display unit 236. The printed material after the inspection process is transported from the inspection device 108 to the finisher 109. The image reading unit 235 can also be realized by a CCD or CMOS sensor.

[0044] The finisher 109 can stack a large number of printed materials delivered from the inspection device 108. The finisher 109 includes transport paths 332, 333, 335, and 336, a reversing unit 337, and a stack tray 331 for stacking printed materials. An escape tray 334, which is a paper discharge tray, is provided at the top of the finisher 109. If the printed image of the printed material delivered from the inspection device 108 is normal, it is stacked on the stack tray 331 via the transport paths 332 and 333. If the printed image of the printed material delivered from the inspection device 108 is not normal, it is discharged to the escape tray 334 via the transport paths 332 and 335. If another device is provided downstream of the finisher 109, the printed material whose printed image is determined to be normal may be transported to that device. In this case, the printed material is transported to that device via the transport paths 332 and 336.

[0045] The inverting unit 337 inverts the front and back sides of the printed matter handed over from the inspection device 108 and conveys it to the conveying path 332. The inverting unit 337 is used, for example, when the pages of the printed matter are aligned and stacked on the stack tray 331. The inverting unit 337 is not used when the printed matter is discharged onto the escape tray 334 or when it is conveyed to a device at a subsequent stage.

[0046] (Inspection operation of the inspection device) As described above, the inspection device 108 inspects the printed image of the printed matter to be inspected. The inspection is performed by comparing the printed image with a reference image registered in advance. If the printed image is the same as the reference image, the printed image is determined to be normal. The reference image is acquired by operating the image forming device 101 in a reference image generation mode. The reference image generation mode is set by the operation unit 237 of the inspection device 108. The reference image is formed on a sheet by the printing device 107, and is read by the CIS units 321, 322 of the inspection device 108. In the reference image generation mode, the results of reading the reference image by the CIS units 321, 322 are stored in the memory 234.

[0047] The reference image must be of good image quality, as it is the standard for judging whether a printed image is good or bad. To improve and stabilize image quality, an image averaging process is performed. In the averaging process, images printed on multiple sheets using the same image data are read, and the multiple images read are averaged. The averaging process averages the color tone (hue, saturation, etc.) of each pixel in the image, and removes noise in the image caused by dust adhering to the sheets. The image that has undergone the averaging process is adopted as the final reference image and is stored in memory 234.

[0048] When a printed matter to be inspected is generated, the reference image generation mode is released. The printed matter to be inspected has a printed image read by the CIS units 321 and 322. The read printed image is compared with the reference image stored in the memory 234 to determine whether or not they match. If the printed image does not match the reference image, the printed matter to be inspected is determined to have an abnormal image (does not meet the standard). If the printed image of the printed matter to be inspected is abnormal, the inspection device 108 displays that fact on the display unit 236. Also, if the printed image of the printed matter to be inspected is abnormal, the inspection device 108 transmits an instruction to the finisher 109 to eject the printed matter to the escape tray 334. As a result, printed matters whose printed images are determined to be abnormal are ejected to the escape tray 334.

[0049] (Image quality adjustment processing) An image adjustment mode is set in the printing device 107 to maintain image quality at a certain level. In this embodiment, in the image adjustment mode, in addition to adjustment processes for image formation conditions such as color misregistration adjustment and density adjustment, toner supply and cleaning processes are performed. When acquiring a reference image, these image quality adjustment processes are performed before acquiring the reference image to maintain the image quality constant in a good state.

[0050] Color registration correction During image formation, the CPU 222 controls the exposure unit 227 using image data acquired via the video I / F 220. The CPU 222 also manages timing such as the on-timing of the laser light emitted from the exposure unit 227. The image forming apparatus 101, which forms a color image, overlaps a plurality of images of different colors. Therefore, color shift occurs when the formation position of the image of each color shifts from a predetermined position. To eliminate the color shift, the CPU 222 controls the exposure unit 227 and adjusts the write timing of the image other than the reference color, thereby correcting the color shift in the sub-scanning direction (the conveying direction of the intermediate transfer belt 308).

[0051] More specifically, in order to obtain the color shift correction amount, the printing device 107 forms a measurement image for adjusting the color shift for each of the colors yellow, magenta, cyan, and black on the intermediate transfer belt 308. These measurement images are read by an image reading sensor (not shown) provided near the intermediate transfer belt 308. Based on the measurement image reading result, the distance from the measurement image of the reference color (e.g., yellow) to the measurement image of the color other than the reference color (e.g., magenta, cyan, and black) is measured. If the measured distance is not a predetermined distance, it is determined that a color shift occurs. The CPU 222 of the printing device 107 calculates the color shift correction amount based on the measured distance and stores it in the memory 223. The CPU 222 corrects the color shift by adjusting the writing timing of the toner image of the color other than the reference color based on the color shift correction amount during image formation.

[0052] Image density adjustment processing A transfer bias voltage is applied to the primary transfer roller 306 in order to transfer the toner image formed on the photosensitive drum 304 to the intermediate transfer belt 308. The voltage value of the transfer bias voltage is set in consideration of the resistance value of the intermediate transfer belt 308, aging of the photosensitive drum 304, the thickness (grammage) of the sheet, the installation environment of the printing device 107 (e.g., ambient temperature), and the like. The transfer bias voltage is set so that an optimal current flows through the primary transfer roller 306. This stabilizes the image quality (the amount of movement of the toner image is stable). For example, the CPU 222 performs an ATVC (Active Transfer Voltage Control) operation in order to set a transfer bias voltage for flowing an optimal transfer current through the primary transfer roller 306.

[0053] During image formation, an electrostatic latent image is formed on the photosensitive drum 304 by a laser beam output from the exposure unit 227. The depth of the electrostatic latent image formed on the photosensitive drum 304 is determined by the amount of laser beam. The depth of the latent image is related to the amount of movement of the toner image from the photosensitive drum 304, so the amount of laser beam affects the image density of the toner image. Therefore, the maximum image density and halftone gradation characteristics of each color are adjusted by setting the amount of laser beam and the transfer bias voltage value to appropriate values. Image density control that keeps the maximum image density of each color constant is called Dmax control, and image density control that keeps the halftone gradation characteristics linear with respect to the image data is called Dhalf control. Dmax control prevents scattering of color-overlaid characters and poor fixing caused by excessive toner application, and improves long-term stability by correcting image density fluctuations caused by aging and environmental changes.

[0054] Toner supply processing The developer is composed of two components, a magnetic carrier and a non-magnetic toner. The developer is stirred in the developing device of the image forming unit 305, and the magnetic carrier and the toner are frictionally charged. This gives the toner a negative charging characteristic. The toner image is visualized when the negatively charged toner adheres to the photosensitive drum 304 on which an electrostatic latent image is formed by the laser light. The toner image formed on the photosensitive drum 304 is transferred to a sheet via the intermediate transfer belt 308. The toner in the developing device is consumed by this series of development and transfer processes. The magnetic carrier in the developing device is not consumed at this time. This causes the ratio of the toner and the magnetic carrier in the developing device to change. When the ratio of the toner and the magnetic carrier changes, the amount of negative charge that the toner is charged with changes. The amount of charge is related to the amount of toner moving to the photosensitive drum 304, and therefore affects the image density.

[0055] To solve this problem, the printing device 107 forms a detection image (toner image) for detecting the toner concentration on the intermediate transfer belt 308, and detects the toner concentration based on the detection result of the detection image by a concentration sensor (not shown) for the detection image. The ratio of toner to magnetic carrier is calculated from the toner concentration, and the amount of toner to be replenished is determined so that this ratio becomes constant. If the toner is less than a predetermined amount, a process of replenishing toner from a toner replenishing unit to the developing device is performed.

[0056] -Cleaning of intermediate transfer belt The intermediate transfer body cleaner 318 forms a nip while being pressed against the intermediate transfer belt 308 which is rotated. Therefore, friction occurs in the intermediate transfer body cleaner 318. Since the intermediate transfer body cleaner 318 is made of a rubber-like material, elastic deformation occurs due to friction with the intermediate transfer belt 308. This elastic deformation occurs significantly when the degree of friction between the intermediate transfer body cleaner 318 and the intermediate transfer belt 308 is large. When the friction exceeds a certain value, the intermediate transfer body cleaner 318 deforms significantly in the rotation direction of the intermediate transfer belt 308, and a curling phenomenon occurs. The intermediate transfer body cleaner 318 cannot form a nip with the intermediate transfer belt 308 due to the curling. As a result, the intermediate transfer body cleaner 318 loses the function of collecting toner on the intermediate transfer belt 308.

[0057] The intermediate transfer belt 308 forms a transfer nip at the position of the secondary transfer roller 309 and transfers the toner image onto the sheet. Due to the manufacturing process, fine paper dust is present on the surface of the sheet. Therefore, residual toner and paper dust are mixed on the intermediate transfer belt 308 after the transfer nip. In many cases, the paper dust has a larger particle size and more pronounced unevenness than the toner used in the printing device 107. If the intermediate transfer body cleaner 318 is unable to maintain a stable posture due to a large amount of elastic deformation caused by friction, the gap between the intermediate transfer body cleaner 318 and the intermediate transfer belt 308 becomes large. Therefore, the paper dust of the sheet is likely to be caught between the intermediate transfer body cleaner 318 and the intermediate transfer belt 308.

[0058] When the particle size of the paper dust is larger than the toner shape and the unevenness is large, the residual toner slips through the gap between the intermediate transfer body cleaner 318 and the intermediate transfer belt 308 that is formed by the paper dust being sandwiched. As a result, the previous toner image partially remains when the next image is formed, which is one of the causes of deterioration in image quality. In order to prevent such toner slipping through at the position of the intermediate transfer body cleaner 318, a banding process is performed. The banding process is a process in which a band-shaped toner band is generated on the intermediate transfer belt 308 in a direction perpendicular to the rotation direction of the intermediate transfer belt, and the toner band is sent directly to the position of the intermediate transfer body cleaner 318 without being transferred to a sheet. By forming a toner band on the intermediate transfer belt 308, the toner of the toner band adheres to the intermediate transfer body cleaner 318, making it easier to scrape off the paper dust on the intermediate transfer belt 308. As a result, the paper dust remaining on the intermediate transfer belt 308 is collected. In other words, the paper dust on the intermediate transfer belt 308 is removed by the toner adhered to the intermediate transfer body cleaner 318. As a result, friction between the intermediate transfer belt 308 and the intermediate transfer member cleaner 318 is reduced, and the cleaning ability of the intermediate transfer member cleaner 318 is maintained.

[0059] Photosensitive drum cleaning process On the photosensitive drum 304, toner (residual toner) that remains without being transferred to the intermediate transfer belt 308 may accumulate. In particular, as the photosensitive drum 304 ages (as the operating time increases), the charge on the photosensitive drum 304 becomes unstable, and the amount of accumulated residual toner increases. The photosensitive drum 304 is cleaned by collecting the accumulated residual toner using a toner band formed on the intermediate transfer belt 308.

[0060] - Processing to determine the progress of aging of components As described above, the CPU 222 counts the operating frequency of components used in image formation, that is, the operating time, the number of operations, or the travel distance. For example, the CPU 222 counts the distance the intermediate transfer belt 308 is driven. The CPU 222 counts the time that a voltage is applied to the image forming unit 305. The CPU 222 counts the time that a voltage is applied to the primary transfer roller 306 and the secondary transfer roller 309. The CPU 222 counts the distance traveled without applying a voltage to the photosensitive drum 304. These count values ​​are held in the memory 223. By checking these count values, the CPU 222 can determine the progress of aging of the components.

[0061] (Overview of image formation operation of a printing device) 4 is a flowchart showing the print processing, which shows the procedure of the image forming operation performed by the printing device 107 when a print instruction is received from the client PC 103.

[0062] Before starting printing, the CPU 222 determines whether the operation mode is set to the reference image generation mode (S1001).

[0063] When the reference image generation mode is set (S1001: Y), the CPU 222 performs the image quality adjustment process to keep the image quality constant and high quality. The CPU 222 first performs the toner supply process (S1002). The CPU 222 stabilizes the developer in the developing device by the toner supply process. When the toner supply process is completed, the CPU 222 performs the color shift correction process (S1003). The CPU 222 eliminates color shifts of the images of the respective colors of yellow, magenta, cyan, and black by the color shift correction process. When the color shift correction process is completed, the CPU 222 performs the image density adjustment process (S1004). The CPU 222 determines a setting value for keeping the image density at an appropriate level during image formation by the image density correction process. When the image density adjustment process is completed, the CPU 222 performs the cleaning process of the intermediate transfer belt 308 and the photosensitive drum 304 (S1005). The processes of S1002 to S1005 complete the preparation for preparing the environment for forming an optimal reference image.

[0064] When the image quality adjustment process is completed, the CPU 222 forms a reference image on a sheet (S1006). The CPU 222 determines whether the reference image has been formed on a predetermined number of sheets, for example, 10 sheets (S1007). If printing of the reference image on the predetermined number of sheets has not been completed (S1007: N), the CPU 222 repeats printing of the reference image on the predetermined number of sheets until the predetermined number is reached (S1006). When printing of the reference image on the predetermined number of sheets is completed (S1007: Y), the CPU 222 ends the printing process in the reference image generation mode. The sheets on which the predetermined number of reference images have been formed are sequentially conveyed to the inspection device 108. The inspection device 108 reads the reference image from each sheet, performs averaging processing on the read results, and stores the result in the memory 234 as a reference image.

[0065] If the operating mode is not set to the reference image generation mode (S1001: Y), the CPU 222 determines whether or not image quality adjustment processing is required to maintain constant image quality (S1008). The CPU 222 determines that image quality adjustment processing is required when it is necessary to execute at least one of the processing items of the image quality adjustment processing performed in the reference image generation mode. If image quality adjustment processing is required (S1008: Y), the CPU 222 performs the image quality adjustment processing determined to be required (S1009). For example, if the CPU 222 determines that color shift correction processing is not required but density correction processing is required, it executes density adjustment processing but does not execute color shift correction processing.

[0066] When it is determined that all the processing items of the image quality adjustment process do not need to be executed (S1008: N), or after the image quality adjustment process, the CPU 222 performs image formation processing based on the image data instructed by the print job (S1010). The CPU 222 determines whether the image formation instructed by the print job has been completed (S1011). When the image formation instructed by the print job has not been completed (S1011: N), the CPU 222 repeats image formation on the number of sheets instructed by the print job until the specified number of sheets is reached (S1008). When printing of images on the specified number of sheets is completed (S1011: Y), the CPU 222 ends the print processing according to the print job. The printed matter formed according to the print job is inspected by the inspection device 108.

[0067] In the above process, when the reference image generation mode is set, all of the image quality adjustment processes, including the toner supply process, the color shift correction process, the density correction process, and the cleaning process, are performed. However, the present invention is not limited to this, and the process may be one that performs at least one of these image quality adjustment processes.

[0068] In the image forming system of this embodiment, when the image forming apparatus 101 operates in the reference image acquisition mode, image quality adjustment processing of the printing apparatus 107 is automatically performed before acquiring the reference image. This makes it possible to acquire a high-quality reference image from a sheet on which a high-quality reference image is printed. Since the printed matter is inspected by comparing it with such a high-quality reference image, only the high-quality printed matter can be selected. In addition, since the components involved in the image formation of the printing apparatus 107 are automatically adjusted, the maintenance time of the printing apparatus 107 can be shortened.

[0069] (When component parts have deteriorated over time) The printing device 107 has components such as an intermediate transfer belt 308, an image forming unit 305, a primary transfer roller 306, a secondary transfer roller 309, and a photosensitive drum 304. When these components age, the amount of toner remaining from the previous image formation increases, and the amount of remaining toner accumulates. For this reason, a cleaning process is performed to remove the remaining toner according to the degree of the ageing. By removing the remaining toner, it is possible to improve the image quality when the next image is formed. The cleaning process is performed between an image forming operation on a sheet and an image forming operation on a subsequent sheet, that is, between image forming operations.

[0070] 5 is a flowchart showing the print processing in this case. This processing shows the procedure of the image forming operation performed by the CPU 222 when a print instruction is received from the client PC 103.

[0071] Before starting printing, the CPU 222 determines whether the operation mode is set to the reference image generation mode (S2001).

[0072] When the reference image generation mode is set (S2001: Y), the CPU 222 judges whether or not an image is to be formed on the first sheet (S2002). When an image is to be formed on the first sheet (S2002: Y), the CPU 222 forms a reference image on the sheet (S2008). The first sheet is the sheet on which printing is performed first when the printing device 107 is used for the first time, after replacing components, after maintenance of the printing device 107, immediately after performing image quality adjustment processing, etc. When an image is to be formed on the second or subsequent sheets (S2002: N), at least one image has been formed, so the CPU 222 judges the progress of aging of each component.

[0073] The CPU 222 determines the progress of deterioration of the intermediate transfer belt 308 over time (S2003). The CPU 222 counts the driving distance of the intermediate transfer belt 308 as the operating frequency. The CPU 222 determines the progress of deterioration of the intermediate transfer belt 308 over time based on this count value. If the count value is equal to or greater than a predetermined value and deterioration of the intermediate transfer belt 308 over time is progressing (S2003: Y), the CPU 222 executes a cleaning process for the intermediate transfer belt 308 (S2007). After the cleaning process, the CPU 222 forms a reference image on a sheet (S2008).

[0074] If the intermediate transfer belt 308 is not deteriorated over time (S2003: N), the CPU 222 judges the progress of deterioration of the image forming unit 305 (S2004). The CPU 222 counts the time during which a voltage is applied to the image forming unit 305 as the operation frequency of the image forming unit 305. The CPU 222 judges the progress of deterioration of the image forming unit 305 based on this count value. If the count value is equal to or greater than a predetermined value and deterioration of the image forming unit 305 is progressing (S2004: Y), the CPU 222 executes a cleaning process for the image forming unit 305 (S2007). After the cleaning process, the CPU 222 forms a reference image on a sheet (S2008).

[0075] If the image forming unit 305 is not deteriorated over time (S2004: N), the CPU 222 judges the deterioration of the primary transfer roller 306 or the secondary transfer roller 309 (S2005). The CPU 222 counts the voltage application time to the primary transfer roller 306 or the secondary transfer roller 309 as the operation frequency of the transfer roller. The CPU 222 judges the deterioration of the primary transfer roller 306 or the secondary transfer roller 309 from the count value. If the count value is equal to or greater than a predetermined value and the deterioration of the primary transfer roller 306 or the secondary transfer roller 309 is progressing (S2005: Y), the CPU 222 executes a cleaning process for the primary transfer roller 306 or the secondary transfer roller 309 (S2007). After the cleaning process, the CPU 222 forms a reference image on a sheet (S2008).

[0076] If the primary transfer roller 306 or the secondary transfer roller 309 is not deteriorated (S2005: N), the CPU 222 judges the deterioration of the photosensitive drum 304. The CPU 222 counts the distance traveled without applying a voltage to the photosensitive drum 304 as the operation frequency of the photosensitive drum 304. The CPU 222 judges the deterioration of the photosensitive drum 304 from the count value. If the count value is equal to or greater than a predetermined value and the deterioration of the photosensitive drum 304 is progressing (S2006: Y), the CPU 222 executes a cleaning process for the photosensitive drum 304 (S2007). After the cleaning process, the CPU 222 forms a reference image on a sheet (S2008). If the deterioration of the photosensitive drum 304 is not progressing (S2006: N), the CPU 222 forms a reference image without performing a cleaning process (S2008).

[0077] In each process of S2003 to S2006, it is determined whether or not the image forming capability is degraded due to the deterioration of the performance of each component used in image formation caused by the aging of the components. In the cleaning process of S2007, cleaning is performed by performing the above-mentioned banding on the intermediate transfer belt 308. By the banding, the remaining toner of each component is collected by the intermediate transfer body cleaner 318 via the intermediate transfer belt 308.

[0078] The sheet on which the reference image is formed in the process of S2008 is conveyed to the inspection device 108. The CPU 222 judges whether the reference image has been formed on a predetermined number of sheets, for example, 10 sheets (S2009). If printing of the reference image on the predetermined number of sheets has not been completed (S2009: N), the CPU 222 repeats the process from S2002 onwards until the reference image is printed on the predetermined number of sheets. When printing of the reference image on the predetermined number of sheets is completed (S2009: Y), the CPU 222 ends the printing process in the reference image generation mode. The sheets on which the predetermined number of reference images are formed are conveyed sequentially to the inspection device 108. The inspection device 108 reads the reference image from each sheet, and stores the result of averaging the read results in the memory 234 as the reference image.

[0079] If the operation mode is not set to the reference image generation mode (S2001: N), the CPU 222 performs image formation processing based on image data instructed by the print job (S2010). The CPU 222 determines whether the image formation instructed by the print job has been completed (S2011). If the image formation instructed by the print job has not been completed (S2011: N), the CPU 222 repeats image formation on the number of sheets instructed by the print job until the specified number of sheets is reached (S2010). When printing of images on the specified number of sheets is completed (S2011: Y), the CPU 222 ends the print processing according to the print job. The printed matter formed according to the print job is inspected by the inspection device 108.

[0080] In the above process, after checking the reference image generation mode, it is checked whether or not an image is to be formed on the first sheet (S2001, S2002). However, the processes of S1002 to S1005 in FIG. 4 may be performed between these processes.

[0081] By performing image quality adjustment processing such as cleaning processing before printing the reference image on a sheet in this manner, degradation of image quality due to dirt on components or performance degradation when printing the reference image on a sheet is suppressed. This reduces degradation and variation in image quality of the reference image. Since printed matter is inspected by comparing it with such a high-quality reference image, only high-quality printed matter can be selected. In addition, since adjustment of components related to image formation of the printing device 107 is performed automatically, maintenance time for the printing device 107 can be shortened.

Claims

1. a printing means for printing an image on a sheet; an inspection unit that inspects an image of a print object to be inspected formed on a sheet by the printing unit; A control means, the inspection means includes a reading means for reading the image formed on the sheet by the printing means, and a storage means for storing a reading result by the reading means of a sheet on which a reference image serving as an inspection standard for the image to be inspected is formed, and performs the inspection by comparing the reading result of the reference image stored in the storage means with the image of the printed matter; When the control means determines that a reference image generation mode has been set before inspection, the control means performs an adjustment process for forming an image by the printing means without forming the reference image before forming the reference image in response to the setting of the reference image generation mode, causes the printing means to form the reference image on a sheet after performing the adjustment process, causes the reading means to read the reference image formed on the sheet, and stores the reference data in the storage means. When the inspection is performed after forming the reference image, the printing means forms an image of an inspection object, the reading means reads the inspection object, and the inspection means performs the inspection by comparing the reference image stored in the storage means with the image obtained by reading the inspection object. Image forming device.

2. The printing means forms the reference image on a predetermined number of sheets, the inspection means performs an averaging process on the reading results of the reference images of the predetermined number of sheets by the reading means, and stores the reading results of the reference images obtained by the averaging process in the storage means.

2. The image forming apparatus according to claim 1.

3. the printing unit includes a developing unit that contains toner consumed in forming the image, the control means performs a process of replenishing the toner to the developing device before the reference image is formed on the sheet by the printing means, 3. The image forming apparatus according to claim 1 or 2.

4. The printing means forms a color image on a sheet by superimposing a plurality of color images; The control unit performs a correction process for color shift of the images of the plurality of colors before the reference image is formed on the sheet by the printing unit. The image forming apparatus according to any one of claims 1 to 3.

5. The control unit performs a correction process for the image density of the reference image before the reference image is formed on the sheet by the printing unit. The image forming apparatus according to any one of claims 1 to 4.

6. the printing unit includes an image carrier that carries the image, a transfer unit that transfers the image carried by the image carrier to the sheet, and a cleaner that removes toner remaining on the sheet after the image is transferred; the control unit performs a process of removing toner remaining on the image carrier by the cleaner before the printing unit forms the reference image on the sheet. The image forming apparatus according to any one of claims 1 to 5.

7. the printing unit includes a counting unit that counts the operation frequency of components used in image formation; The control means determines the deterioration of the component based on the count value by the counting means, and performs a process of adjusting the image quality of the image for the component determined to have deteriorated over time. The image forming apparatus according to any one of claims 1 to 6.

8. The control means performs processing to adjust image quality of an image of a component whose count value is equal to or greater than a predetermined value.

8. The image forming apparatus according to claim 7.

9. The printing method further comprises a finisher that separates printed matter determined to be normal from printed matter determined to be abnormal based on the result of the inspection. The image forming apparatus according to any one of claims 1 to 8.

10. The finisher includes a stacker for stacking printed matter that is determined to be normal; and a tray to which printed matter that is not determined to be normal is discharged.

10. The image forming apparatus according to claim 9.

Images