Image forming apparatus

Abstract

The invention relates to an image forming apparatus. The recording head ejects ink corresponding to an image to be printed by means of nozzles arranged side by side, the control unit (81) determines the nozzle corresponding to the image to be printed and causes the recording heads (1a-1d) to eject ink from the nozzles, and the ejection failure nozzle detection unit (83) performs ejection failure inspection of the nozzles and detects ejection failure nozzles. A correction processing unit (84) that performs correction processing corresponding to the detected injection failure nozzle; furthermore, during the continuous printing, the defective ejection nozzle detection unit (83) performs an ejection defect check without performing the correction process every time a predetermined number of pages are printed, and updates the defective ejection nozzles that have been subjected to the correction process on the basis of the result of the ejection defect check.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus. Background Art

[0002] In an inkjet image forming device, a test pattern is printed on printing paper using a recording head. Based on the read image of the printed test pattern, the defective nozzles that cannot normally eject ink among the nozzles that eject ink in the recording head are detected, and as a correction process, the amount of ink in its adjacent dots is increased.

[0003] Furthermore, the image forming apparatus periodically performs nozzle inspections, sets abnormal nozzles as unusable nozzles, and when the unusable nozzles are judged to be normal in a subsequent inspection, the nozzles are restored to usable nozzles, and when the unusable nozzles are judged to be abnormal in a predetermined number of inspections, the unusable nozzles are continuously set as unusable nozzles. In this way, even if an abnormal nozzle is misdetected, the misdetection problem can be eliminated in subsequent inspections.

[0004] However, even if the abnormal nozzle is detected normally, foreign matter or dirt attached to the nozzle may be removed over time during subsequent printing operations.

[0005] In the above-mentioned device, when there is an erroneous detection of an abnormal nozzle, the erroneous detection problem can be eliminated in subsequent inspections. However, in the case where an abnormality occurs in a nozzle due to a cause that is eliminated over time during the printing action, the nozzle is still detected as an abnormal nozzle in subsequent inspections. Therefore, even if the cause of the abnormality is eliminated later, the nozzle continues to be set as an unusable nozzle. Summary of the invention

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus capable of suppressing unnecessary correction processing and improving print quality.

[0007] The image forming device of the present invention comprises: a recording head which uses arranged nozzles to eject ink corresponding to an image to be printed; a control unit which determines the nozzles corresponding to the image to be printed and causes the recording head to eject ink from the nozzles; a defective ejection nozzle detection unit which performs a defective ejection inspection on the nozzles and detects defective ejection nozzles among the nozzles; and a correction processing unit which performs correction processing corresponding to the detected defective ejection nozzles.

[0008] Furthermore, during continuous printing, the defective ejection nozzle detection unit performs the defective ejection inspection instead of the correction processing every time a predetermined number of pages are printed, and updates the defective ejection nozzle that performs the correction processing based on the result of the defective ejection inspection.

[0009] (Effects of the Invention)

[0010] According to the present invention, it is possible to obtain an image forming apparatus capable of suppressing unnecessary correction processing and improving print quality.

[0011] The above and other objects, features and advantages of the present invention will become more apparent in combination with the following detailed description based on the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a side view for explaining the internal mechanical structure of the image forming apparatus according to the embodiment of the present invention.

[0013] Figure 2 Yes means Figure 1 FIG. 1 is a plan view of an example of recording heads 1 a , 1 b , 1 c , and 1 d in the image forming apparatus 10 .

[0014] Figure 3 1 is a block diagram showing the electrical configuration of the image forming apparatus 10 according to the embodiment of the present invention.

[0015] Figure 4 Yes Figure 1-Figure 3 The flowchart is used to explain the operation of the image forming apparatus during continuous printing.

[0016] Figure 5 This is a diagram for explaining an example of the number of nozzles to be calibrated when continuously printing 50,000 pages in the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0018] Figure 1 This is a side view for explaining the internal mechanical structure of the image forming apparatus according to the embodiment of the present invention. The image forming apparatus 10 according to the present embodiment is a printer, a copier, a facsimile machine, a multifunction machine, or the like.

[0019] Figure 1The image forming apparatus 10 shown in FIG. 1 includes a print engine 10a and a paper conveying unit 10b. The print engine 10a physically forms a page image to be printed on a printing paper (printing paper, etc.). In the present embodiment, the print engine 10a is a line type ink-jet type print engine.

[0020] In the present embodiment, the print engine 10 a includes line-type recording heads 1 a to 1 d corresponding to four ink colors, cyan, magenta, yellow, and black, respectively.

[0021] Figure 2 Yes means Figure 1 FIG. 1 is a top view of an example of recording heads 1a, 1b, 1c, and 1d in the image forming apparatus 10. Figure 2 As shown, in this embodiment, each recording head 1a, 1b, 1c, 1d has a plurality of (here, three) heads 11. These heads 11 are arranged along the main scanning direction and can be installed or removed relative to the device body. It should be noted that the head 11 of the recording heads 1a, 1b, 1c, 1d can also be one.

[0022] The head 11 of the recording heads 1a, 1b, 1c, and 1d includes nozzles arranged in a two-dimensional shape corresponding to ejection positions arranged in the main scanning direction, and ejects ink corresponding to an image to be printed using the nozzles.

[0023] The paper conveying unit 10 b conveys pre-printed print sheets to the print engine 10 a along a predetermined conveying path, and conveys the printed print sheets from the print engine 10 a to a predetermined discharge unit (discharge tray 10 c or the like).

[0024] The paper conveying unit 10b includes a main paper conveying unit 10b1 and a circulating paper conveying unit 10b2. When performing double-sided printing, the main paper conveying unit 10b1 conveys the printing paper used for printing the first side page image to the printing engine 10a, and the circulating paper conveying unit 10b2 stops a predetermined number of printing papers and conveys the printing paper from the rear section to the front section of the printing engine 10a.

[0025] In this embodiment, the main paper conveying unit 10b1 includes: an endless conveyor belt 2 arranged opposite to the print engine 10a and conveying the printing paper, a driving roller 3 and a driven roller 4 on which the conveyor belt 2 is hung, an adsorption roller 5 for flattening (nipping) the printing paper together with the conveyor belt 2, and a pair of discharge rollers (a pair of discharge rollers) 6 and 6a.

[0026] The driving roller 3 and the driven roller 4 rotate the conveyor belt 2. Then, the printing paper conveyed from the paper supply cassettes 20-1 and 20-2 described later is flattened by the suction roller 5, and the flattened printing paper is sequentially conveyed to the printing positions of the recording heads 1a to 1d by the conveyor belt 2, and the recording heads 1a to 1d print images of each color. Then, the printing paper after the color printing is completed is discharged to the discharge tray 10c, etc. by the discharge roller pair 6 and 6a.

[0027] Furthermore, the main paper conveying unit 10b1 is provided with a plurality of paper feed cassettes 20-1 and 20-2. The paper feed cassettes 20-1 and 20-2 contain printing papers SH1 and SH2, respectively. The printing papers SH1 and SH2 are pushed upward by lift plates 21 and 24, respectively, so that the printing papers SH1 and SH2 come into contact with pickup rollers 22 and 25, respectively. The printing papers SH1 and SH2 respectively placed in the paper feed cassettes 20-1 and 20-2 are picked up one by one from the upper side by the pickup rollers 22 and 25, respectively. The paper feed rollers 23 and 26 are rollers that convey the printing papers SH1 and SH2 supplied from the paper feed cassettes 20-1 and 20-2, respectively, through the pickup rollers 22 and 25, respectively, one by one toward the conveying path. The transport roller 27 is a transport roller on a common transport path for the printing papers SH1 and SH2 fed from the paper feed cassettes 20 - 1 and 20 - 2 .

[0028] When performing double-sided printing, the circulating paper conveying unit 10b2 returns the printing paper from a predetermined position on the downstream side of the printing engine 10a to a predetermined position on the upstream side (here, a predetermined position on the upstream side of the line sensor 31 described later). The circulating paper conveying unit 10b2 includes a conveying roller 41 and a switch back conveying path 41a, which reverses the advancing direction of the printing paper to switch the side of the printing paper facing the printing engine 10a from the first side to the second side.

[0029] Furthermore, the image forming apparatus 10 includes a line sensor 31 and a paper detection sensor 32 .

[0030] The line sensor 31 is an optical sensor arranged in a direction perpendicular to the paper conveying direction and detecting the positions of the two end edges (two side edges) of the paper. For example, the line sensor 31 is a CIS (Contact Image Sensor). In the present embodiment, the line sensor 31 is arranged between the registration roller 28 and the print engine 10a.

[0031] The paper detection sensor 32 is an optical sensor that detects when the leading edge of the printing paper SH1 or SH2 passes a predetermined position on the conveyance path. When the paper detection sensor 32 detects the leading edge of the printing paper SH1 or SH2, the line sensor 31 detects the positions of both end edges of the printing paper.

[0032] In addition, for example Figure 1 As shown in the figure, the print engine 10a is arranged on one side (here, above) of the upper and lower sides of the print paper conveying path, the line sensor 31 is arranged on the other side (here, below) of the upper and lower sides of the print paper conveying path, and the circulating paper conveying unit 10b2 switches the print paper (switch back) from the downstream side of the print engine 10a toward the upstream side of the line sensor 31 and conveys the print paper.

[0033] Figure 3 FIG. 1 is a block diagram showing the electrical structure of the image forming apparatus 10 according to the embodiment of the present invention. Figure 3 As shown in FIG. 1 , the image forming apparatus 10 includes the following Figure 1 and Figure 2 The mechanical structure shown includes, in addition to the image output unit 71 , an operation panel 72 , a storage device 73 , an image reading device 74 , and a controller 75 .

[0034] The operation panel 72 is arranged on the housing surface of the image forming apparatus 10, and includes a display device 72a such as a liquid crystal display, and an input device 72b such as a hard key or a touch panel. The display device 72a is used to display various information to the user, and the input device 72b is used to accept user operations.

[0035] The storage device 73 is a nonvolatile storage device (a flash memory, a hard disk drive, etc.) that stores data, programs, and the like necessary for controlling the image forming apparatus 10 .

[0036] The image reading device 74 includes a platen glass and an automatic document feeding device, and optically reads an image of a document placed on the platen glass or a document fed by the automatic document feeding device, and generates image data of the image.

[0037] The controller 75 includes a computer that performs software processing according to a program, an ASIC (Application Specific Integrated Circuit) that performs predetermined hardware processing, and the like, and operates as various processing units.

[0038] The computer includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. It works as various processing units (together with an ASIC as needed) by downloading programs stored in the ROM, storage device 73, etc. into the RAM and executing the programs by the CPU.

[0039] Here, the controller 75 functions as a control unit 81 , an image processing unit 82 , a defective ejection nozzle detection unit 83 , and a correction processing unit 84 .

[0040] The control unit 81 controls the image output unit 71 (print engine 10a, paper conveying unit 10b, etc.) to perform the print job requested by the user. In the present embodiment, the control unit 81 causes the image processing unit 82 to perform a predetermined image processing, controls the print engine 10a (head unit 11) to eject ink, and thus forms a print image on the print paper. The image processing unit 82 performs a predetermined image processing such as RIP (Raster Image Processing), color conversion processing, and halftone processing on the image data of the image to be printed on the print paper.

[0041] Specifically, the control unit 81 causes the print engine 10 a to print the user's document image based on the print image data designated by the user.

[0042] In addition, in this embodiment, the control unit 81 has: (a) determining the center position of the printing paper as the actual position of the center of the paper based on the positions of the two end edges of the printing paper detected by the line sensor 31, and (b) an automatic centering function for adjusting the center position of the image to be printed based on the actual position of the center of the paper, and the automatic centering function is performed as hardware processing.

[0043] Specifically, in the automatic centering function, the control unit 81 changes the drawing position of the image to be printed along the main scanning direction, and the change amount is the difference between the reference center position of the print engine 10a and the actual position of the center of the paper. In this embodiment, the nozzles in the recording heads 1a to 1d do not move, so the nozzles corresponding to each pixel in the image to be printed change according to the drawing position of the image to be printed.

[0044] In this way, the control unit 81 determines the nozzles corresponding to the image to be printed (the nozzles corresponding to each pixel of the image) (here, based on the position of the printing paper), and causes the recording heads 1 a to 1 d to eject ink from the nozzles.

[0045] The defective ejection nozzle detection unit 83 performs a defective ejection inspection on the nozzles of the recording heads 1a to 1d, and detects the defective ejection nozzles among the nozzles of the recording heads 1a to 1d. Specifically, the defective ejection nozzle detection unit 83 performs the following processing: (a) prints a test pattern on a printing paper using the recording heads 1a to 1d, and (b) detects the defective ejection nozzle based on the density distribution of the read image of the test pattern.

[0046] Furthermore, the ejection defective nozzle detection unit 83 stores ejection defective nozzle data (such as a nozzle number) indicating the detected ejection defective nozzle in the storage device 73 as setting data 73 a .

[0047] The test pattern is a known image, such as a stripe image of a single density, or an image including thin lines corresponding to each nozzle.

[0048] The read image of the test chart is obtained as, for example, RGB image data using the line sensor 31 or the image reading device 74. When the image of the test chart is read using the line sensor 31, the printing paper on which the test chart is printed by the print engine 10a is conveyed to the position of the line sensor 31 using the circulating paper conveying unit 10b2.

[0049] Furthermore, the resolution of the read image (scanning resolution) is lower than the resolution of the test image printed on the printing paper by the recording heads 1a to 1d (printing resolution). For example, the resolution of the read image is less than one quarter of the printing resolution. For example, the printing resolution is 1200 dpi and the resolution of the read image is 300 dpi.

[0050] If a poor ejection occurs in the nozzle, insufficient density occurs in the test image. Therefore, in the density distribution of the read image, a decrease in density also occurs at the insufficient density portion of the test image. However, in the case where the scanning resolution of the read image is lower than the printing resolution, the decrease in density will not be steep (peak) but will be gentle. Therefore, the poor ejection nozzle detection unit 83 determines the pixel with the lowest density after the density decrease of the read image density distribution, and determines the poor ejection nozzle from the nozzles corresponding to the pixel based on the shape of the density decrease of the read image density distribution.

[0051] The correction processing unit 84 performs correction processing (here, hardware processing) corresponding to the correction target nozzle corresponding to the print image. It should be noted that in this correction processing, for example, the image data (pixel value) of the pixel corresponding to the nozzle with abnormal ejection is corrected to a density of no ink ejection, and the image data (pixel value) of the pixel corresponding to the nozzle adjacent to the nozzle with poor ejection is corrected to a higher density of the pixel.

[0052] Moreover, in continuous printing (i.e., a print job of continuously printing multiple pages), the defective ejection nozzle detection unit 83 does not perform correction processing (i.e., does not perform correction processing, but prints a test image) but instead performs a defective ejection check each time a specified number of pages are printed, and updates the defective ejection nozzle that performs the correction processing based on the result of the defective ejection check.

[0053] For example, in a continuous printing of 50,000 pages, the ejection failure inspection is performed every 10,000 pages are printed. It should be noted that the predetermined number of pages that serves as the interval between ejection failure inspections may be a fixed value or may be set by the user.

[0054] In the ejection failure inspection performed every time a predetermined number of pages are printed, the ejection failure nozzle detection unit 83 sets both ejection failure nozzles to be corrected and ejection failure nozzles not to be corrected based on the result of the current ejection failure inspection.

[0055] In the present embodiment, the number of poor ejection nozzles to be corrected is limited to a prescribed upper limit (e.g., 100). The upper limit is the limit number of poor ejection nozzles that can be corrected from the time when the nozzles corresponding to each pixel of the image to be printed are determined to the time when the nozzles are caused to eject ink. The correction processing unit 84 performs the following processing: (a) when the number of poor ejection nozzles in the current poor ejection inspection does not exceed the prescribed upper limit, regardless of the result of the previous poor ejection inspection, the poor ejection nozzles to be corrected and the poor ejection nozzles not to be corrected are set according to the result of the current poor ejection inspection; (b) when the number of poor ejection nozzles in the current poor ejection inspection exceeds the prescribed upper limit, the poor ejection nozzles to be corrected can be set according to the result of the previous poor ejection inspection and the result of the current poor ejection inspection.

[0056] In this case, for example, when the result of the poor ejection inspection (the nozzle number of the poor ejection nozzle, etc.) is stored in the storage device 73 as history data, and the number of poor ejection nozzles in this poor ejection inspection exceeds a specified upper limit, based on the history data, the more times a nozzle has been detected as a poor ejection nozzle in the past specified number of inspections, the more preferentially the poor ejection nozzle is selected as the poor ejection nozzle for correction processing.

[0057] Next, the operation of the above-mentioned image forming apparatus 10 will be described.

[0058] (a) Setting of nozzles to be calibrated

[0059] The ejection defective nozzle detection unit 83 performs an ejection defect inspection at a predetermined timing. In the ejection defect inspection, first, the ejection defective nozzle detection unit 83 uses the control unit 81 to cause the image output unit 71 to print the above-mentioned test chart on the printing paper at a predetermined printing resolution, and uses the line sensor 31 or the image reading device 74 to obtain a read image (RGB image data, gray scale image data, etc.) of the test chart printed on the printing paper at a predetermined scanning resolution.

[0060] Then, the defective ejection nozzle detection unit 83 detects the defective ejection nozzle as described above based on the density distribution in the main scanning direction of the test chart read image, and uses the defective ejection nozzle as a correction target nozzle, and stores the setting data 73a indicating the correction target nozzle (identification information such as the nozzle number) in the storage device 73. At this time, the history data indicating the defective ejection nozzle may also be stored in the storage device 73.

[0061] In this way, the nozzles to be corrected are set in the ejection defective nozzle data.

[0062] (b) Printing operation

[0063] When a print request is received, the control unit 81 causes the image processing unit 82 to perform image processing on the image specified by the print request to obtain image data of the image to be printed, and causes the image output unit 71 to transport printing paper and print the image to be printed on the printing paper based on the image data.

[0064] At this time, the correction processing unit 84 reads the setting data 73a from the storage device 73 in advance before printing starts to determine the correction target nozzle. When the position of the printing paper is detected by the line sensor 31, the following processing is performed: (a) the nozzle corresponding to each pixel in the above image is determined, (b) the correction target nozzle used for the above image is determined, and (c) the correction processing corresponding to the correction target nozzle is performed. In this way, the correction processing is performed on the part of the image corresponding to the correction target nozzle (and the adjacent nozzles of the nozzle with poor ejection in the main scanning direction). Then, the control unit 81 performs the above printing based on the image data after the correction processing.

[0065] (c) Operation during continuous printing

[0066] Figure 4 Yes Figure 1-Figure 3 For example, when the number of pages to be printed continuously is greater than a predetermined value, the following processing is performed.

[0067] First, when a print request is received, the correction processing unit 84 reads the setting data 73a from the storage device 73 before printing starts to determine the nozzles to be corrected (step S1), the control unit 81 selects a page image (step S2), and when the position of the printing paper is detected by the line sensor 31, the correction processing is performed as described above (step S3). Then, the control unit 81 causes the print engine 10a to perform a print process based on the page image after the correction processing (step S4).

[0068] The control unit 81 determines whether printing up to the last page is completed (step S5 ). If it is determined that printing up to the last page is completed, the control unit 81 ends the continuous printing.

[0069] On the other hand, when it is determined that printing up to the last page is not completed, the ejection defective nozzle detection unit 83 determines whether the number of printed pages since the start of continuous printing or since the last ejection defect inspection has reached the predetermined number of pages (step S6 ).

[0070] When it is determined that the number of printed pages has not reached the above-mentioned specified number of pages, the process returns to step S2 and the processing in and after step S2 is performed on the next page.

[0071] On the other hand, when it is determined that the number of printed pages has reached the above-mentioned predetermined number of pages, the ejection defective nozzle detection unit 83 interrupts the continuous printing, performs the ejection defective inspection as described above (step S7), and updates the nozzle to be corrected (setting data 73a) (step S8). Then, the continuous printing is restarted, and the process returns to step S2 to perform the process of step S2 and thereafter on the next page.

[0072] As described above, in the above-mentioned embodiment, the recording heads 1a to 1d eject ink corresponding to the image to be printed using the nozzles arranged in an array. The control unit 81 determines the nozzles corresponding to the image to be printed, and causes the recording heads 1a to 1d to eject ink from the nozzles. The defective ejection nozzle detection unit 83 performs a defective ejection inspection of the nozzles, and detects the defective ejection nozzles. The correction processing unit 84 performs a correction process corresponding to the detected defective ejection nozzles.

[0073] Furthermore, during continuous printing, the defective ejection nozzle detection unit 83 performs ejection defect detection instead of correction processing every time a predetermined number of pages are printed, and updates the defective ejection nozzles to be corrected based on the result of the ejection defect detection.

[0074] In this way, the nozzles that have eliminated the problem of poor ejection during continuous printing are not corrected, thereby suppressing unnecessary correction processing and improving the print quality (image quality). In particular, when an upper limit is set for the number of nozzles to be corrected, the number of poor ejection nozzles that are not corrected can be reduced.

[0075] Figure 5 This is a diagram for explaining an example of the number of nozzles to be calibrated when continuously printing 50,000 pages in the image forming apparatus according to the embodiment of the present invention.

[0076] exist Figure 5 In the example shown, under the conditions of an output resolution of 1200 dpi and using 5000 nozzles of only black ink, the image forming apparatus of this embodiment performs ejection failure inspection and updates the nozzles to be corrected every 10,000 pages.

[0077] In the case of coated paper, 19 nozzles of the first nozzles to be calibrated are eliminated by the ejection failure inspection and updating of the nozzles to be calibrated every 10,000 pages, and finally 13 nozzles to be calibrated are left.

[0078] In the case of plain paper, 35 nozzles of the initial nozzles to be calibrated are eliminated through the ejection failure inspection and the updating of the nozzles to be calibrated every 10,000 pages, and the final number of nozzles to be calibrated is 78. Compared with coated paper, paper dust that causes ejection failure is more likely to be generated in the case of plain paper, and there is a tendency for the number of nozzles with ejection failure (i.e., nozzles to be calibrated) to increase.

[0079] In addition, in the comparative example, the ejection defect inspection and the update of the nozzles to be corrected are not performed every 10,000 pages, but the nozzles to be corrected at the beginning are all the nozzles to be corrected until the end. In the case of coated paper, the number of nozzles to be corrected is 30. In the case of plain paper, 100 (upper limit) of the 122 ejection defect nozzles are set as the nozzles to be corrected, and the 22 ejection defect nozzles are not corrected.

[0080] in addition, Figure 5 The "sense of streaks when visually observed" in the table means whether white streaks in the printed product can be visually recognized, "○" (good) means that no white streaks are visually recognized, and "×" (bad) means that white streaks are visually recognized.

[0081] in addition, Figure 5 The "sense of stripes during scanning" means whether white stripes are detected in the scanned image of the 1200dpi print product. "○" (good) means that the maximum value of the difference in RGB values ​​between the normal image and the image after correction is less than 10% relative to the normal value. "△" (medium) means that the maximum value is more than 10% and less than 20% relative to the normal value. "×" (poor) means that the maximum value is more than 20% relative to the normal value.

[0082] like Figure 5As shown in the example of FIG. 1 , in this embodiment, the print quality is good for all types of print paper (“striping feeling when visually observed” is “○”, “striping feeling when scanning” is “○”).

[0083] On the other hand, in the comparative example, in the case of plain paper, uncorrected defective ejection nozzles continue to exist (remain), and the print quality is poor ("striping sensation during visual observation" is "×", "striping sensation during scanning" is "×").

[0084] It should be noted that various changes and modifications may be made to the described implementation mode without departing from its spirit and scope and without diminishing its intended advantages. Since these changes and modifications are obvious to those skilled in the art, these changes and modifications should also be included in the scope of protection of the claims of this application.

[0085] For example, in the above embodiment, the predetermined number of pages may be set according to the type of printing paper used for printing. For example, the more likely the type of paper dust that causes ejection failure is to be generated, the smaller the predetermined number of pages may be set.

[0086] In the above embodiment, the predetermined number of pages may be set according to whether double-sided printing or single-sided printing is performed.

[0087] Furthermore, in the above-described embodiment, in the ejection failure inspection during continuous printing, only the nozzles determined to be ejection failure nozzles in the previous ejection failure inspection may be inspected.

[0088] (Industrial Applicability)

[0089] The present invention can be applied to, for example, an inkjet image forming apparatus.

Claims

1. An image forming device, characterized in that: have: The recording head ejects ink corresponding to the image to be printed using the arranged nozzles. a control unit that determines the nozzles corresponding to the image to be printed and causes the recording head to eject ink from the nozzles; a defective ejection nozzle detection unit that performs a defective ejection inspection on the nozzles and detects a defective ejection nozzle among the nozzles, and a correction processing unit that performs correction processing corresponding to the detected ejection defective nozzle; In continuous printing, the ejection defective nozzle detection unit performs the ejection defect inspection instead of the correction processing every time a predetermined number of pages are printed, and updates the ejection defective nozzle for which the correction processing is performed based on a result of the ejection defect inspection.

2. The image forming apparatus according to claim 1, wherein: In the ejection failure inspection, the ejection failure nozzle detection unit performs the following processing: (a) printing a test pattern on a printing paper using the recording head, (b) detecting ejection failure nozzles based on the density distribution of a read image of the test pattern; In continuous printing, the defective ejection nozzle detection unit does not perform the correction process every time a specified number of pages are printed, but prints the test chart and performs the defective ejection check, and updates the defective ejection nozzle that should be subjected to the correction process based on the result of the defective ejection check.

3. The image forming apparatus according to claim 1, wherein: In the ejection failure inspection performed every time the predetermined number of pages are printed, the ejection failure nozzle detection section sets both the ejection failure nozzles to be subjected to the correction process and the ejection failure nozzles not subjected to the correction process based on the result of the current ejection failure inspection.

4. The image forming apparatus according to claim 1, wherein: The ejection defective nozzles to be corrected are limited to a number below a predetermined upper limit. The correction processing unit performs the following processing: (a) when the number of the defective ejection nozzles in the current defective ejection inspection does not exceed a prescribed upper limit, regardless of the result of the previous defective ejection inspection, the defective ejection nozzles to be subjected to the correction processing and the defective ejection nozzles not subjected to the correction processing are set according to the result of the current defective ejection inspection; (b) when the number of the defective ejection nozzles in the current defective ejection inspection exceeds a prescribed upper limit, the defective ejection nozzles to be subjected to the correction processing are set according to the result of the previous defective ejection inspection and the result of the current defective ejection inspection.

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