Image forming device

Abstract

To provide an image forming device that suppresses image quality degradation due to increased ink viscosity, without performing preliminary ejection, even when ink is ejected using a line-head type recording head.SOLUTION: A controller 75 causes a line-head type recording head to eject ink to print an image. When a nozzle corresponding to a pixel of interest in an image to be printed ejects ink for a predetermined first number of consecutive lines, and one or both of two nozzles corresponding to adjacent pixels on both sides of the pixel of interest fail to eject ink for a predetermined second number of consecutive lines, the controller 75 causes the recording head to eject ink from one or both of the two nozzles instead of the ink ejection from the nozzle corresponding to the pixel of interest.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In a certain inkjet image forming device, when printing in multiple passes, the proportion of dots formed consecutively by a single nozzle in a certain scan is set to be higher in low-density areas than in high-density areas, thereby suppressing image quality degradation caused by ink viscosity increase without performing preliminary ejection (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-25120 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the case of a line head image forming apparatus, since printing is not performed in multiple passes, it is difficult to suppress image quality degradation caused by ink viscosity increase without performing preliminary ejection as described above. Note that if preliminary ejection (ink flushing other than printing) is used to suppress image quality degradation caused by ink viscosity increase, a mechanical configuration for preliminary ejection is required, and there is a possibility that printing will be delayed due to preliminary ejection.

[0005] The present invention has been made in consideration of the above problems, and aims to provide an image forming device that suppresses image quality degradation caused by increased ink viscosity without performing preliminary ejection, even when ink is ejected using a line head type recording head. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention includes a line-head type recording head having a plurality of nozzles that eject ink from the nozzles, and a controller that causes the recording head to eject ink to print an image. When a nozzle corresponding to a pixel of interest in the image ejects ink for a predetermined first number of consecutive lines, and one or both of two nozzles corresponding to adjacent pixels on both sides of the pixel of interest fail to eject ink for a predetermined second number of consecutive lines, the controller causes the recording head to eject ink from one or both of the two nozzles instead of the nozzle corresponding to the pixel of interest. [Effects of the Invention]

[0007] According to the present invention, an image forming apparatus can be obtained that suppresses image quality degradation due to increased ink viscosity without performing preliminary ejection, even when ink is ejected using a line-type recording head.

[0008] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view illustrating the mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of the image forming apparatus shown in FIG. [Figure 3] FIG. 3 is a block diagram showing the electrical configuration of the image forming apparatus 10 according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram illustrating the alternative discharge according to the first embodiment. [Figure 5] FIG. 5 is a flowchart illustrating the operation of the image forming apparatus 10 according to the first embodiment. [Figure 6] FIG. 6 is a flowchart illustrating the continuous counter control in FIG. [Figure 7]FIG. 7 is a flowchart illustrating the discharge control in the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating alternative ejection in the second embodiment. [Figure 9] FIG. 9 is a flowchart illustrating the discharge control in the second embodiment. [Figure 10] FIG. 10 is a diagram illustrating the position of the alternative ejection in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] Embodiment 1

[0012] Fig. 1 is a side view illustrating the internal mechanical configuration of an image forming apparatus according to an embodiment of the present invention. Fig. 2 is a plan view of the image forming apparatus shown in Fig. 1. The image forming apparatus 10 according to this embodiment is a device such as a printer, copier, facsimile machine, or multifunction device, and in this embodiment is equipped with a line-head inkjet color printing mechanism.

[0013] The image forming apparatus 10 shown in FIG. 1 includes a print engine 10a and a sheet transport unit 10b. The print engine 10a physically prints an image to be printed on a print sheet (such as print paper). An ink cartridge is detachably attached to the print engine 10a, and the print engine 10a performs printing using ink supplied from the ink cartridge. The sheet transport unit 10b transports the print sheet to the print engine 10a.

[0014] In this embodiment, print engine 10a is equipped with line-head type recording heads 1a to 1d corresponding to four ink colors: cyan, magenta, yellow, and black, and ink is ejected onto a print sheet by recording heads 1a to 1d.

[0015] As shown in Figure 2, in this embodiment, each of the recording heads 1a, 1b, 1c, and 1d has one or more (three in this example) head units 11. These head units 11 are arranged along the main scanning direction and are detachable from the device body. The head unit 11 (i.e., each of the recording heads 1a, 1b, 1c, and 1d) has multiple nozzles arranged in the main scanning direction, and ejects ink from the nozzles onto a print sheet.

[0016] In this embodiment, the sheet conveying section 10b includes a circular conveying belt 2 arranged opposite the print engine 10a to convey the print sheet, a drive roller 3, a driven roller 4, and a tension roller 4a around which the conveying belt 2 is suspended, an adsorption roller 5 that nips the print sheet together with the conveying belt 2, a downstream conveying belt 6, and a dryer 7.

[0017] A drive roller 3, a driven roller 4, and a tension roller 4a rotate the conveyor belt 2. The print sheet 101 conveyed from a paper feed cassette 20 (described later) is nipped by an attraction roller 5, and the nipped print sheet 101 is conveyed by the conveyor belt 2 to the printing positions of the recording heads 1a to 1d in order, where an image of each color is printed by the recording heads 1a to 1d. The sheet sensor 2a detects the passage of the print sheet, and the current position of the print sheet on the conveyance path is determined based on the detection timing. The image is then printed at the appropriate position on the print sheet. After printing, the print sheet is discharged to a discharge tray 10c or the like by a subsequent conveyor belt 6. At this time, a dryer 7 dries the print sheet on which the ink has been ejected.

[0018] The sheet suction unit 8 is disposed along the sheet transport path. Negative pressure is applied to the sheet suction unit 8, causing the print sheet to be attracted to the transport belt 2 through the sheet suction holes.

[0019] Furthermore, the sheet transport unit 10b is equipped with a paper feed cassette 20 as a paper feed source. The paper feed cassette 20 stores print sheets 101, and a lift plate 21 pushes the print sheets 101 upward to abut against a pickup roller 22. The print sheets 101 placed in the paper feed cassette 20 are picked up one by one from above by the pickup roller 22 onto a paper feed roller 23. The paper feed roller 23 is a roller that transports the print sheets 101 fed from the paper feed cassette 20 by the pickup roller 22 onto a transport path one by one.

[0020] The transport rollers 27 are rollers that transport the print sheet 101 on a predetermined transport path. When the transported print sheet 101 is detected by the resist sensor 28a, the registration rollers 28 temporarily stop the print sheet 101 and transport the print sheet 101 to the print engine 10a (specifically, to the nip position between the attraction roller 5 and the transport belt 2) at the secondary paper feed timing. The secondary paper feed timing is specified by the controller 75, which will be described later, so that an image is formed at a specified position on the print sheet 101.

[0021] Fig. 3 is a block diagram showing the electrical configuration of image forming apparatus 10 according to an embodiment of the present invention. As shown in Fig. 3, image forming apparatus 10 includes a printing device 71 having the mechanical configuration shown in Figs. 1 and 2, as well as an operation panel 72, a storage device 73, an image reading device 74, and a controller 75.

[0022] The operation panel 72 is arranged on the surface of the housing of the image forming device 10 and is equipped with a display device 72a such as an LCD display and an input device 72b such as hard keys or a touch panel, and displays various messages to the user on the display device 72a and accepts user operations on the input device 72b.

[0023] The storage device 73 is a non-volatile storage device (such as a flash memory or a hard disk drive) that stores data, programs, and the like required for controlling the image forming apparatus 10.

[0024] The image reading device 74 is equipped with a platen glass and an automatic document feeder, and optically reads the image of a document placed on the platen glass or a document transported by the automatic document feeder, and generates image data of that image.

[0025] The controller 75 includes a computer that operates according to a program, an ASIC (Application Specific Integrated Circuit) that executes predetermined operations, and an FPGA (Field Programmable Gate Array), and operates as various processing units. The computer includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and operates as various processing units (together with the ASIC and FPGA as necessary) by loading programs stored in the ROM, storage device 73, etc. into the RAM and executing them on the CPU.

[0026] The controller 75 causes the recording heads 1a to 1d to eject ink to print an image. Specifically, the controller 75 controls the printing device 71 (print engine 10a, sheet conveying unit 10b, etc.) to execute a print job requested by the user. In doing so, the controller 75 executes predetermined image processing on the image (image data) specified by the user, and controls the print engine 10a (head unit 11) to eject ink to form the image on a print sheet.

[0027] Furthermore, when a nozzle corresponding to a pixel of interest in an image specified by the user ejects ink for a predetermined first number of consecutive lines, and both of the two nozzles corresponding to adjacent pixels on both sides of the pixel of interest fail to eject ink for a predetermined second number of consecutive lines, the controller 75 causes the recording heads 1a to 1d to eject ink from both of the two nozzles mentioned above instead of ejecting ink from the nozzle corresponding to the pixel of interest.

[0028] In this way, when the pixel of interest is an ink ejection pixel, if the nozzles corresponding to adjacent pixels have consecutive non-ejection events, substitute ejection is performed by the nozzles corresponding to the adjacent pixels. This reduces the number of nozzles that are non-ejecting for a long period of time.

[0029] Specifically, the controller 75 (a) includes a first continuity counter CNT_BLK[x] for counting the number of consecutive lines of ink ejection and a second continuity counter CNT_WHT[x] for counting the number of consecutive lines of ink non-ejection for each pixel position x in the main scanning direction, (b) determines whether the nozzle corresponding to the pixel of interest ejects ink for a predetermined first number of consecutive lines based on the value of the continuity counter CNT_BLK[x], and (c) determines whether one or both of the two nozzles corresponding to adjacent pixels on both sides have failed to eject ink for a predetermined second number of consecutive lines based on the value of the continuity counter CNT_WHT[x]. Specifically, if the value of the continuity counter CNT_BLK[x] for the pixel of interest exceeds a threshold value TH1, it is determined that the nozzle corresponding to the pixel of interest has ejected ink for the predetermined first number of consecutive lines, and if the values ​​of the continuity counters CNT_WHT[x] for the adjacent pixels on both sides exceed a threshold value TH2, it is determined that one or both of the two nozzles corresponding to the adjacent pixels on both sides have failed to eject ink for a predetermined second number of consecutive lines.

[0030] Fig. 4 is a diagram illustrating alternative ejection in embodiment 1. For example, as shown in Fig. 4, in embodiment 1, (a) when the controller 75 causes the recording heads 1a to 1d to eject ink from both of the two nozzles described above instead of ejecting ink from the nozzle corresponding to the pixel of interest, the controller 75 makes the ink ejection amount from each of the two nozzles described above less than the ink ejection amount from the nozzle corresponding to the pixel of interest.

[0031] Next, a description will be given of the operation of the image forming apparatus 10 according to the first embodiment. Fig. 5 is a flowchart illustrating the operation of the image forming apparatus 10 according to the first embodiment.

[0032] When the controller 75 receives a job request, it executes the requested print job, and in the print job, executes the following processing on the image data of the image to be printed for each page.

[0033] First, the controller 75 initializes the continuity counters CNT_BLK[x] and CNT_WHT[x] for all pixel positions in the main scanning direction to zero (step S1).

[0034] Next, the controller 75 selects a line of interest (line position y) along the sub-scanning direction (step S2), and selects a pixel of interest (pixel position x) along the main scanning direction (step S3).

[0035] Then, the controller 75 performs the continuous counter control (step S4) described below for the pixel of interest on the line of interest, and performs the discharge control (step S5) described below. In the discharge control, alternative discharge is selected as needed, and the image data of the page is changed according to the alternative discharge.

[0036] Thereafter, the controller 75 determines whether the current pixel of interest is the pixel at the end of the line (step S6), and if the current pixel of interest is not the pixel at the end of the line, returns to step S3, selects the next pixel of interest along the main scanning direction (step S3), and performs the same processing from step S4 onwards.

[0037] On the other hand, if the current pixel of interest is the pixel at the end of the line, the process for the current line of interest ends, and the controller 75 determines whether the current line of interest is the line at the end of the page (step S7). If the current line of interest is not the line at the end of the page, the process returns to step S2, the next line of interest is selected in the sub-scanning direction (step S2), and the process from step S3 onwards is similarly performed.

[0038] In this way, image data after discharge control is obtained for each page, and the controller 75 causes the printing device 71 to print the image for each page using the image data after discharge control.

[0039] Here, the continuous counter control will be explained. Fig. 6 is a flowchart for explaining the continuous counter control in Fig. 5.

[0040] In continuous counter control, first, the controller 75 determines whether the pixel of interest (pixel position x) is a black pixel (ink ejection pixel) (step S11). Specifically, it determines whether the value of the image data D[x] of the pixel of interest is a value that indicates ink ejection at a predetermined ink ejection amount.

[0041] If the target pixel (pixel position x) is determined to be a black pixel, the controller 75 increments (increases by 1) the black pixel continuation counter CNT_BLK[x] of the target pixel (step S12), and clears the white pixel continuation counter CNT_WHT[x] of the target pixel to a predetermined value (e.g., 0) (step S13).

[0042] On the other hand, if it is determined that the pixel of interest (pixel position x) is not a black pixel, the controller 75 clears the black pixel continuation counter CNT_BLK[x] of the pixel of interest to a predetermined value (e.g., 0) (step S14), and increments the white pixel continuation counter CNT_WHT[x] of the pixel of interest (step S15).

[0043] Therefore, if ink ejection continues along the sub-scanning direction at a pixel position in the main scanning direction, the value of the consecutive black pixel counter CNT_BLK[x] increases, and if ink non-ejection continues along the sub-scanning direction, the value of the consecutive white pixel counter CNT_WHT[x] increases.

[0044] Here, a description will be given of the discharge control in the embodiment 1. Fig. 7 is a flowchart illustrating the discharge control in the embodiment 1.

[0045] In the discharge control, first, the controller 75 determines whether or not the value of the black pixel consecutive counter CNT_BLK[x] of the pixel of interest (pixel position x) exceeds the threshold value TH1 (step S21).

[0046] If the value of the black pixel continuity counter CNT_BLK[x] exceeds the threshold value TH1, the controller 75 determines whether the values ​​of the white pixel continuity counters CNT_WHT[x+1] and CNT_WHT[x-1] of the adjacent pixels on both sides (pixel positions x+1, x-1) both exceed the threshold value TH2 (step S22).

[0047] If the values ​​of both the white pixel continuity counters CNT_WHT[x+1] and CNT_WHT[x-1] exceed the threshold value TH2, the controller 75 first changes one of the adjacent pixels (pixel position x-1) from a white pixel (a pixel that does not eject ink) to a small dot black pixel (step S23). Specifically, the value of the image data D[x-1] of the adjacent pixel is changed to a value corresponding to a small dot black pixel (a value corresponding to a dot size smaller than the dot size based on D[x]). Furthermore, the controller 75 clears the value of the white pixel continuity counter CNT_WHT[x-1] of the adjacent pixel to a predetermined value (step S24), and increments the value of the black pixel continuity counter CNT_BLK[x-1] of the adjacent pixel (step S25).

[0048] Similarly, the controller 75 changes the other adjacent pixel (pixel position x+1) from a white pixel to a small black pixel (step S26). Specifically, the value of the image data D[x+1] of the adjacent pixel is changed to a value corresponding to the small black pixel. Note that the values ​​of the white pixel continuity counter CNT_WHT[x+1] and the black pixel continuity counter CNT_BLK[x+1] of the adjacent pixel are not updated here; they will be updated in the next continuity counter control.

[0049] Then, the controller 75 changes the pixel of interest from a black pixel to a white pixel (step S27). Specifically, the value of the image data D[x] of the pixel of interest is changed to a value indicating a white pixel. Furthermore, the controller 75 increments the value of the white pixel consecutive counter CNT_WHT[x] of the pixel of interest (step S28), and clears the value of the black pixel consecutive counter CNT_BLK[x] of the pixel of interest to a predetermined value (step S29).

[0050] In addition, if it is determined in step S21 that the value of the black pixel continuous counter CNT_BLK[x] does not exceed the threshold value TH1, or if it is determined in step S22 that the value of either the white pixel continuous counter CNT_WHT[x+1] or CNT_WHT[x-1] does not exceed the threshold value TH2, the controller 75 does not change the image data for the above-mentioned alternative ejection.

[0051] As described above, according to the first embodiment, the controller 75 causes the line-head recording heads 1a to 1d to eject ink to print an image. When a nozzle corresponding to a pixel of interest in an image to be printed ejects ink for a predetermined first number of consecutive lines, and both of the two nozzles corresponding to adjacent pixels on both sides of the pixel of interest fail to eject ink for a predetermined second number of consecutive lines, the controller 75 causes the recording heads 1a to 1d to eject ink from both of the two nozzles described above instead of ejecting ink from the nozzle corresponding to the pixel of interest.

[0052] As a result, substitute ejection is performed when printing the image to be printed, so even when ink is ejected using a line-type recording head, preliminary ejection is not performed and image quality degradation due to increased ink viscosity is suppressed. Therefore, the recording heads 1a to 1d do not perform preliminary ejection.

[0053] Embodiment 2

[0054] FIG. 8 is a diagram illustrating alternative ejection in the second embodiment.

[0055] 8, when a nozzle corresponding to a pixel of interest in an image to be printed ejects ink for a predetermined first number of consecutive lines, and only one of the two nozzles corresponding to adjacent pixels on either side of the pixel of interest fails to eject ink for a predetermined second number of consecutive lines, the controller 75 causes the recording heads 1a-1d to eject ink from only that one of the two nozzles instead of the nozzle corresponding to the pixel of interest. Furthermore, when causing the recording heads 1a-1d to eject ink from only one of the two nozzles, the controller 75 increases the amount of ink ejected from that one of the two nozzles compared to the amount of ink ejected from the nozzle corresponding to the pixel of interest.

[0056] Next, a description will be given of the operation of the image forming apparatus 10 according to the second embodiment. Fig. 9 is a flowchart illustrating the discharge control in the second embodiment.

[0057] In the discharge control of the second embodiment, first, the controller 75 determines whether or not the value of the black pixel consecutive counter CNT_BLK[x] of the pixel of interest (pixel position x) exceeds the threshold value TH1 (step S31).

[0058] If the value of the black pixel continuity counter CNT_BLK[x] exceeds the threshold value TH1, the controller 75 determines whether the value of the white pixel continuity counter CNT_WHT[x-1] of one adjacent pixel (pixel position x-1) exceeds the threshold value TH2 (step S32).

[0059] If the value of the white pixel continuity counter CNT_WHT[x-1] of one adjacent pixel (pixel position x-1) exceeds the threshold value TH2, the controller 75 determines whether the value of the white pixel continuity counter CNT_WHT[x+1] of the other adjacent pixel (pixel position x+1) is less than or equal to the threshold value TH2 (step S33).

[0060] If the value of the white pixel continuity counter CNT_WHT[x-1] for one adjacent pixel (pixel position x-1) exceeds the threshold value TH2 and the value of the white pixel continuity counter CNT_WHT[x+1] for the other adjacent pixel (pixel position x+1) is equal to or less than the threshold value TH2, the controller 75 changes the one adjacent pixel from a white pixel to a large dot black pixel (step S34). Specifically, the value of the image data D[x-1] for the one adjacent pixel is changed to a value corresponding to a large dot black pixel (a value corresponding to a dot size larger than the dot size based on D[x]). Furthermore, the controller 75 clears the value of the white pixel continuity counter CNT_WHT[x-1] for that adjacent pixel to a predetermined value (step S35) and increments the value of the black pixel continuity counter CNT_BLK[x-1] for that adjacent pixel (step S36).

[0061] Then, the controller 75 changes the pixel of interest from a black pixel to a white pixel (step S37), increments the value of the white pixel consecutive counter CNT_WHT[x] of the pixel of interest (step S38), and clears the value of the black pixel consecutive counter CNT_BLK[x] of the pixel of interest to a predetermined value (step S39).

[0062] On the other hand, if the value of the white pixel continuity counter CNT_WHT[x-1] of one adjacent pixel (pixel position x-1) does not exceed the threshold value TH2 in step S32, the controller 75 determines whether the value of the white pixel continuity counter CNT_WHT[x+1] of the other adjacent pixel (pixel position x+1) exceeds the threshold value TH2 (step S40).

[0063] If the value of the white pixel continuity counter CNT_WHT[x-1] for one adjacent pixel (pixel position x-1) does not exceed the threshold value TH2, and the value of the white pixel continuity counter CNT_WHT[x+1] for the other adjacent pixel (pixel position x+1) exceeds the threshold value TH2, the controller 75 changes the other adjacent pixel from a white pixel to a large dot black pixel (step S41). Specifically, the value of the image data D[x+1] for the other adjacent pixel is changed to a value corresponding to the large dot black pixel. Then, the processes from step S37 onwards are executed.

[0064] In addition, if it is determined in step S31 that the value of the black pixel continuous counter CNT_BLK[x] does not exceed the threshold value TH1, if it is determined in step S33 that the value of the white pixel continuous counter CNT_WHT[x+1] is not equal to or less than the threshold value TH2, or if it is determined in step S40 that the value of the white pixel continuous counter CNT_WHT[x+1] exceeds the threshold value TH2, the controller 75 will not change the image data for the above-mentioned alternative ejection.

[0065] The other configurations and operations of the image forming apparatus according to the second embodiment are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0066] Embodiment 3

[0067] In the third embodiment, the ejection control of the first embodiment and the ejection control of the second embodiment are performed. That is, when the nozzles corresponding to adjacent pixels on both sides of the pixel of interest fail to eject a predetermined number of consecutive lines as in the first embodiment, substitute ejection is performed by the two nozzles corresponding to the adjacent pixels on both sides, and when the nozzle corresponding to only one adjacent pixel of the pixel of interest fails to eject a predetermined number of consecutive lines as in the second embodiment, substitute ejection is performed by the nozzle corresponding to that one adjacent pixel.

[0068] The other configurations and operations of the image forming apparatus according to the third embodiment are the same as those of the first or second embodiment, and therefore the description thereof will be omitted.

[0069] Embodiment 4

[0070] Fig. 10 is a diagram illustrating the position of substitute ejection in embodiment 4. In embodiment 4, for example, as shown in Fig. 4, the above-mentioned predetermined first number of lines is individually set so as to be different for each pixel position x of the pixel of interest. For example, when an image to be printed contains a grid pattern such as a table, if the above-mentioned predetermined first number of lines is constant, substitute ejection will be performed at multiple positions in the main scanning direction on one line, and streaks may appear on that line; however, if the predetermined first number of lines differs for each pixel position x, such streaks are less likely to appear.

[0071] The other configurations and operations of the image forming apparatus according to the fourth embodiment are the same as those of any of the first to third embodiments, and therefore, description thereof will be omitted.

[0072] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, it is intended that such changes and modifications be included within the scope of the claims.

[0073] For example, in the first to fourth embodiments, the value of the black continuous counter CNT_BLK[x] may be weighted according to the ink ejection amount (the value of the image data D[x]). In this case, the greater the ink ejection amount, the greater the increment value. When the ink ejection amount of the target pixel is large, the dot size of the target pixel becomes larger, so that the substitution ejection is less noticeable.

[0074] Furthermore, in the above-described first to fourth embodiments, the initial value of the second continuity counter CNT_WHT[x] after clearing may be set according to the amount of ink ejected when ink is ejected from one or both of the two nozzles described above, instead of the ink ejected from the nozzle corresponding to the pixel of interest. In this case, the smaller the ink ejection amount, the larger the initial value after clearing. In other words, the smaller the ink ejection amount immediately before a non-ejection, the more likely the effects of ink thickening will be felt thereafter. Therefore, the initial value after clearing is made larger, making it easier for alternative ejection to be performed in a short period of time. [Industrial Applicability]

[0075] The present invention is applicable to, for example, an inkjet type image forming apparatus. [Explanation of symbols]

[0076] 1a to 1d recording head 10 Image forming device 75 Controller

Claims

1. a line head type recording head having a plurality of nozzles and ejecting ink from the nozzles; a controller that causes the recording head to eject ink and print an image; the controller, when a nozzle corresponding to a pixel of interest in the image ejects ink for a predetermined first number of consecutive lines, and one or both of two nozzles corresponding to adjacent pixels on both sides of the pixel of interest fail to eject ink for a predetermined second number of consecutive lines, causes the recording head to eject ink from one or both of the two nozzles instead of ejecting ink from the nozzle corresponding to the pixel of interest; An image forming apparatus comprising:

2. The image forming apparatus according to claim 1, characterized in that the controller (a) when causing the recording head to eject ink from both of the two nozzles instead of ejecting ink from the nozzle corresponding to the target pixel, makes the ink ejection volume of each of the two nozzles smaller than the ink ejection volume of the nozzle corresponding to the target pixel, and (b) when causing the recording head to eject ink from only one of the two nozzles instead of ejecting ink from the nozzle corresponding to the target pixel, makes the ink ejection volume of one of the two nozzles larger than the ink ejection volume of the nozzle corresponding to the target pixel.

3. 2. The image forming apparatus according to claim 1, wherein the predetermined first number of lines is individually set to be different for each pixel position of the target pixel.

4. The controller (a) includes a first continuity counter for counting the number of consecutive lines of ink ejection and a second continuity counter for counting the number of consecutive lines of ink non-ejection for each pixel position in the main scanning direction, (b) determines whether or not the nozzle corresponding to the pixel of interest ejects ink for the predetermined first number of consecutive lines based on the value of the first continuity counter, and (c) determines whether or not one or both of the two nozzles corresponding to the adjacent pixels on both sides fail to eject ink for the predetermined second number of consecutive lines based on the value of the second continuity counter, the value of the first continuity counter is weighted in accordance with the ink ejection amount of the ink ejection; an initial value after clearing of the second continuity counter for the pixel of interest is set according to the amount of ink ejected when ink is ejected from one or both of the two nozzles instead of ink ejected from the nozzle corresponding to the pixel of interest; 2. The image forming apparatus according to claim 1, wherein:

5. 5. The image forming apparatus according to claim 1, wherein the recording head does not perform preliminary ejection.

Images