Image formation device, correction method of image formation device, and correction program

Abstract

To improve productivity even by using a recording medium of a plurality of kinds of printing objects.SOLUTION: An image formation device 100 includes: a sheet behavior detection correction part 523 of detecting deviation in a conveyance direction 10 of a discharge position to a web 120 between a plurality of liquid discharge head units 210 according to the type of the web 120, and performing sheet behavior detection correction of correcting a discharge timing of the plurality of liquid discharge head units 210 so that discharge positions of the plurality of liquid discharge head units 210 become constant regardless of the type of the web 120, on the basis of a detection result of the deviation; and an inter-color alignment adjustment part 524 for performing inter-color alignment adjustment of correcting the discharge timing of the plurality of liquid discharge head units 210 so that the discharge positions of the plurality of liquid discharge head units 210 are aligned, after the sheet behavior detection correction has bee performed. When the inter-color alignment adjustment has been completed using other kind of the web 120 in the past, the inter-color alignment adjustment part 524 does not perform the inter-color alignment adjustment.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, a correction method for an image forming apparatus, and a correction program. [Background technology]

[0002] 2. Description of the Related Art In an image forming apparatus having a line head, a technique is known for improving printing accuracy by adjusting the alignment of the line head.

[0003] For example, Patent Document 1 describes a configuration in which head position control is performed to eliminate a state in which the line head is tilted with respect to the transport direction of the recording medium, thereby preventing printing defects such as diagonal lines.

[0004] Patent Document 2 discloses a configuration for correcting the amount of misalignment of a plurality of line heads in the transport direction. Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional alignment adjustment methods such as those described in Patent Documents 1 and 2, it is necessary to adjust the alignment for each type (such as paper type) of recording medium to be printed on. This can result in a situation where the time required for alignment adjustment in a process increases depending on the number of types of recording media used, resulting in reduced productivity.

[0006] An object of the present invention is to improve productivity even when a plurality of types of recording media to be printed are used. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, an image forming apparatus according to one aspect of the present invention comprises an ejection unit having a plurality of liquid ejection head units which eject liquid for forming an image on a recording medium transported in a predetermined direction; a first correction unit which detects a displacement in the predetermined direction of the ejection positions on the recording medium between the plurality of liquid ejection head units according to the type of the recording medium, and performs a first correction based on the detection result of the displacement to correct the ejection timing of the plurality of liquid ejection head units so that the ejection positions of the plurality of liquid ejection head units are constant regardless of the type of the recording medium; and a second correction unit which performs a second correction after the second correction by the first correction unit to correct the ejection timing of the plurality of liquid ejection head units so that the ejection positions of the plurality of liquid ejection head units are aligned, and the second correction unit does not perform the second correction if the second correction has been completed in the past using another type of recording medium. Effect of the Invention

[0008] Productivity can also be improved when multiple types of recording media are used for printing. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of an image forming apparatus according to an embodiment; [Diagram 2] FIG. 1 is a diagram showing an example of a configuration of a discharge unit according to an embodiment; [Diagram 3] Functional block diagram of a controller related to ejection timing correction control [Figure 4] Controller hardware configuration diagram [Diagram 5] FIG. 1 is a schematic diagram for explaining an overview of ejection timing correction control; [Figure 6] Flowchart of ejection timing correction control according to an embodiment [Figure 7] Flowchart of head abnormality determination control according to the embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0011] <Configuration of Image Forming Apparatus> The configuration of an image forming apparatus 100 according to an embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing a schematic configuration of the image forming apparatus 100 according to an embodiment. The image forming apparatus 100 is a so-called inkjet type image forming apparatus that forms an image by ejecting liquid onto a conveyed object. The ejected liquid is a recording liquid such as a water-based or oil-based ink.

[0012] The object to be transported is, for example, a recording medium. In the illustrated example, the image forming apparatus 100 forms an image by ejecting liquid onto a web 120, which is an example of a recording medium transported by a roller 130 or the like. The web 120 is a so-called continuous paper printing medium or the like. That is, the web 120 is a roll-shaped sheet that can be wound up. In this way, the image forming apparatus 100 is a so-called production printer. In the following description, an example will be described in which the roller 130 adjusts the tension of the web 120 and transports the web 120 in the illustrated direction (hereinafter referred to as the "transport direction 10"). In this example, the image forming apparatus 100 is an inkjet printer that ejects ink of each of four colors, black (K), cyan (C), magenta (M), and yellow (Y), to form an image at a predetermined location on the web 120. The image forming apparatus 100 includes an ejection unit 110 that ejects such a plurality of inks onto the web 120.

[0013] 2 is a diagram showing an example of the configuration of the ejection section 110 according to the embodiment. As shown in the figure, the ejection section 110 of the image forming apparatus 100 has four liquid ejection head units 210 for ejecting ink of four colors.

[0014] Each liquid ejection head unit 210 ejects a liquid of each color onto the web 120 transported in the transport direction 10. The web 120 is transported by two pairs of nip rollers, roller 230, and the like. Of these two pairs of nip rollers, the nip roller installed upstream of each liquid ejection head unit 210 is referred to as the "first nip roller NR1." Meanwhile, the nip roller installed downstream of the first nip roller NR1 and each liquid ejection head unit 210 is referred to as the "second nip roller NR2." As shown in the figure, each nip roller rotates while nipping a transported object such as the web 120. In this manner, each nip roller NR1, NR2, and roller 230 are mechanisms for transporting the web 120 in a predetermined direction.

[0015] Moreover, it is desirable that the recording medium of the web 120 is long. Specifically, it is desirable that the length of the recording medium is longer than the distance between the first nip roller NR1 and the second nip roller NR2. Furthermore, the recording medium is not limited to the web 120. In other words, the recording medium may be a sheet that is folded and stored, so-called "Z paper," or the like.

[0016] In the illustrated overall configuration example, the liquid ejection head units 210 are installed in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side to the downstream side. That is, the liquid ejection head unit installed on the most upstream side (hereinafter referred to as the "black liquid ejection head unit 210K") is for black (K). The liquid ejection head unit installed next to the black liquid ejection head unit 210K (hereinafter referred to as the "cyan liquid ejection head unit 210C") is for cyan (C). Furthermore, the liquid ejection head unit installed next to the cyan liquid ejection head unit 210C (hereinafter referred to as the "magenta liquid ejection head unit 210M") is for magenta (M). Next, the liquid ejection head unit installed on the most downstream side (hereinafter referred to as the "yellow liquid ejection head unit 210Y") is for yellow (Y).

[0017] Each liquid ejection head unit 210 ejects ink of each color onto a predetermined location on the web 120 based on image data, etc. The position where this ink is ejected (hereinafter referred to as the "landing position") is approximately equal to the position where the liquid ejected from the liquid ejection head unit 210 lands on the recording medium, that is, the landing position is, for example, directly below the liquid ejection head unit 210. Below, an example will be described in which the processing position where processing is performed by the liquid ejection head unit 210 is taken as the landing position.

[0018] In this example, black ink is ejected onto the landing position of black liquid ejection head unit 210K (hereinafter referred to as "black landing position PK"). Similarly, cyan ink is ejected onto the landing position of cyan liquid ejection head unit 210C (hereinafter referred to as "cyan landing position PC"). Furthermore, magenta ink is ejected onto the landing position of magenta liquid ejection head unit 210M (hereinafter referred to as "magenta landing position PM"). Moreover, yellow ink is ejected onto the landing position of yellow liquid ejection head unit 210Y (hereinafter referred to as "yellow landing position PY").

[0019] The timing at which each liquid ejection head unit 210 ejects ink is controlled by a controller 520 connected to each liquid ejection head unit 210 .

[0020] Further, a plurality of rollers are provided for each liquid ejection head unit 210. As shown in the figure, the plurality of rollers are provided, for example, on the upstream side and downstream side of each liquid ejection head unit. In the example shown in the figure, a roller (hereinafter referred to as a "first roller") is provided upstream of each liquid ejection head unit for each liquid ejection head unit. In addition to the first roller, a roller (hereinafter referred to as a "second roller") is provided downstream of each liquid ejection head unit. When the first roller and the second roller are provided in this manner, so-called "fluttering" can be reduced at each landing position. The first roller and the second roller are driven rollers. The first roller and the second roller may be rollers that are rotated by a motor or the like.

[0021] In addition, the first roller, which is an example of the first support member, and the second roller, which is an example of the second support member, do not have to be rotating bodies such as driven rollers. In other words, the first roller and the second roller may be support members that support the transported object. For example, the first support member and the second support member may be a pipe or a shaft with a circular cross section. Alternatively, the first support member and the second support member may be a curved plate or the like in which the portion that contacts the transported object is an arc shape. Below, an example will be described in which the first support member is the first roller and the second support member is the second roller.

[0022] Specifically, a first roller for black CR1K is provided to transport the web 120 to a black landing position PK to eject black ink at a predetermined position on the web 120. In response to this, a second roller for black CR2K is provided to transport the web 120 downstream from the black landing position PK. Similarly, a first roller for cyan CR1C and a second roller for cyan CR2C are provided for the cyan liquid ejection head unit 210C. Furthermore, a first roller for magenta CR1M and a second roller for magenta CR2M are provided for the magenta liquid ejection head unit 210M. Furthermore, a first roller for yellow CR1Y and a second roller for yellow CR2Y are provided for the yellow liquid ejection head unit 210Y.

[0023] In the example shown in FIG. 2, the liquid ejection head unit 210 is configured with four heads, but the liquid ejection head unit may be configured with a number of heads other than four.

[0024] Each liquid ejection head unit 210 is provided with a sensor, which is an example of a detection unit, for detecting the position, movement speed, movement amount, or a combination of these of the recording medium. This sensor is preferably an optical sensor that uses light such as a laser or infrared light. The optical sensor may be, for example, a CCD (Charge Coupled Device) camera or a CMOS (Complementary Metal Oxide Semiconductor) camera. Furthermore, the optical sensor is preferably a global shutter. With a global shutter, even if the movement speed is fast, the optical sensor can reduce so-called image shift caused by shifts in shutter timing compared to a rolling shutter or the like.

[0025] Specifically, a black sensor SENK is provided for the black liquid ejection head unit 210K. Similarly, a cyan sensor SENC is provided for the cyan liquid ejection head unit 210C. Furthermore, a magenta sensor SENM is provided for the magenta liquid ejection head unit 210M. Furthermore, a yellow sensor SENY is provided for the yellow liquid ejection head unit 210Y. Note that in the following description, the black sensor SENK, cyan sensor SENC, magenta sensor SENM, and yellow sensor SENY may be collectively referred to simply as "sensor SEN."

[0026] Each sensor SEN provided in each liquid ejection head unit 210 can obtain coordinate information of the web 120 in each head unit. Each sensor SEN outputs the obtained coordinate information of the web 120 to the controller 520.

[0027] Furthermore, in this embodiment, the roller 230 disposed upstream of the liquid ejection head unit 210 in the transport direction 10 has an encoder 240. The encoder 240 is an example of a movement amount measuring unit that measures the movement amount of the web 120 in the transport direction 10. The encoder 240 is connected to, for example, the rotation shaft of the roller 230, detects the amount of rotation of the roller 230, and outputs it to the controller 520. The controller 520 can obtain position information of the web 120 in the transport direction 10 based on the detection result of the encoder 240.

[0028] The controller 520 implements a technique for grasping the paper displacement between the color heads of the web 120 based on the coordinate information of the web 120 acquired from each sensor SEN and the position information of the web 120 acquired from the encoder 240. In this embodiment, this technique is referred to as "paper behavior detection." For details of paper behavior detection, refer to the method described in Japanese Patent No. 7000687. In this method, the amount of deviation in the ink ejection timing of each liquid ejection head unit 210 is calculated based on information on the position, moving speed, moving amount, or a combination of these of the web 120 at the installation position of each sensor SEN provided on each liquid ejection head unit 210. This "amount of deviation" corresponds to the "paper displacement between the color heads of the web 120" in paper behavior detection.

[0029] Here, we consider a total of four nozzle arrays for each liquid ejection head unit 210, which are included in each of the multiple nozzle arrays arranged in the main scanning direction and are arranged in a specific order in the transport direction 10. The "paper displacement between the color heads on the web 120" that can be grasped by the above-mentioned paper behavior detection means the amount of deviation in the sub-scanning direction (i.e., the transport direction 10) of the actual landing positions PK, PC, PM, and PY of the ejected ink of each color on the web 120 when the ejection timing is controlled so that ink is ejected from a specific nozzle array for each liquid ejection head unit 210 to the same predetermined location on the web 120.

[0030] Further, the controller 520 can correct the ejection timing of each head (paper behavior detection correction) based on the paper displacement grasped by the paper behavior detection so that the ejection positions of each color are aligned to the same position on the paper. The paper behavior detection correction can eliminate the influence of the difference in the amount of elongation due to the difference in the type of recording medium, and can equalize the amount of deviation of the ejection positions of each color regardless of the type of recording medium. In this embodiment, such paper behavior detection correction may be referred to as "first correction." For details of the paper behavior detection correction, for example, the method described in Japanese Patent No. 7000687 can be referred to. In this method, the amount of deviation of the ink ejection timing of each liquid ejection head unit 210 is calculated as described above, and the ink ejection timing of the downstream head between two adjacent heads is adjusted in a direction to reduce the amount of deviation.

[0031] In particular, in this embodiment, the controller 520 first detects the displacement in the transport direction 10 of the ejection positions onto the web 120 between the multiple liquid ejection head units 210K, 210C, 210M, and 210Y according to the type of web 120, and based on the displacement detection results, performs paper behavior detection correction (first correction) to correct the ejection timing of each of the multiple liquid ejection head units 210 so that the ejection positions of the multiple liquid ejection head units 210 are constant regardless of the type of web 120.

[0032] Secondly, after the paper behavior detection correction, the controller 520 performs color alignment adjustment (second correction) to correct the ejection timing of the multiple liquid ejection head units 210 so that the ejection positions of the multiple liquid ejection head units 210K, 210C, 210M, and 210Y are aligned.

[0033] Furthermore, if color alignment adjustment has been completed in the past using another type of recording medium, the controller 520 does not perform color alignment adjustment, but instead uses the past adjustment results to create a correction command and outputs it to the liquid ejection head unit 210. Details of the ejection timing correction control of the liquid ejection head unit 210 by the controller 520 will be described later with reference to FIG. 3 and subsequent figures.

[0034] A scanner unit 53 is provided at a position downstream of the liquid ejection head unit 210 of the ejection section 110 in the transport direction 10. The scanner unit 53 reads the dots ejected onto the web 120 by the liquid ejection head unit 210, and outputs information on the reading result to a controller 520. The controller 520 can adjust the ejection timing of each head of the liquid ejection head unit 210 based on the information on the reading result of the dots ejected onto the web 120 acquired from the scanner unit 53.

[0035] <Ejection timing correction control> The ejection timing correction control according to this embodiment will be described with reference to FIGS.

[0036] Fig. 3 is a functional block diagram of the controller 520 related to the ejection timing correction control. As shown in Fig. 3, the controller 520 has an ejection control unit 521, a same-color alignment adjustment unit 522, a paper behavior detection correction unit 523 (first correction unit), an inter-color alignment adjustment unit 524 (second correction unit), and an adjustment result storage unit 525 as functions related to the ejection timing correction control.

[0037] The discharge control unit 521 controls the operation of the discharge unit 110 of the image forming apparatus 100. For example, based on image information input from outside the image forming apparatus 100, the discharge control unit 521 generates a control command for forming an image corresponding to the image information on the web 120. The discharge control unit 521 outputs the generated control command to each unit of the liquid discharge head unit 210.

[0038] The same-color alignment adjustment unit 522 adjusts the alignment of each head for each of the liquid ejection head units 210K, 210C, 210M, and 210Y, that is, for each liquid ejection head unit of the same color. The contents of the alignment adjustment by the same-color alignment adjustment unit 522 can include, for example, three processes: (1) analysis of the ejection results, (2) calculation of the ejection timing, and (3) feedback of the timing to the nozzle drive circuit.

[0039] That is, the same-color alignment adjustment section 522 performs same-color alignment adjustment based on information on the ejection results of the liquid ejection head units 210K, 210C, 210M, and 210Y, and provides information on the adjustment results to the ejection control section 521. The ejection control section 521 adjusts control commands to each liquid ejection head unit based on the information on the adjustment results input from the same-color alignment adjustment section 522. As a result, the ejection control section 521 can perform feedback control on a same-color unit basis for the multiple liquid ejection head units 210K, 210C, 210M, and 210Y.

[0040] The paper behavior detection correction unit 523 performs paper behavior detection correction (first correction) to correct the ejection timing of each of the multiple liquid ejection head units 210 so that the ejection positions of the multiple liquid ejection head units 210 are constant regardless of the type of web 120, based on the coordinate information of the web 120 acquired from each sensor SEN and the position information of the web 120 acquired from the encoder 240. The paper behavior detection correction unit 523 outputs information on the ejection positions of the multiple liquid ejection head units 210 after performing the paper behavior detection correction to the color alignment adjustment unit 524.

[0041] The inter-color alignment adjustment unit 524 performs inter-color alignment adjustment (second correction) to correct the ejection timing of the multiple liquid ejection head units 210 so that the ejection positions of the multiple liquid ejection head units 210K, 210C, 210M, and 210Y are aligned based on information on the ejection positions of the multiple liquid ejection head units 210 after paper behavior detection correction input from the paper behavior detection correction unit 523. The inter-color alignment adjustment unit 524 generates a correction command to correct the ejection timing of each of the multiple liquid ejection head units 210K, 210C, 210M, and 210Y based on the adjustment result of the inter-color alignment adjustment. The inter-color alignment adjustment unit 524 outputs the generated correction command to each part of the liquid ejection head unit 210.

[0042] Furthermore, the color alignment adjustment section 524 outputs information on the adjustment result to the adjustment result storage section 525. The information on the adjustment result includes information on the correction command output to the liquid ejection head unit 210 and the like.

[0043] The adjustment result storage unit 525 stores and saves information on the adjustment result of the color alignment adjustment (second correction) performed by the color alignment adjustment unit 524.

[0044] Particularly in this embodiment, if the adjustment result information is stored in the adjustment result storage unit 525, that is, if the color alignment adjustment (second correction) has already been performed in a previous printing operation, the color alignment adjustment unit 524 does not perform the color alignment adjustment in the current operation. In this case, the color alignment adjustment unit 524 can create and output a correction command using the adjustment result information stored in the adjustment result storage unit 525, for example.

[0045] Fig. 4 is an example of a hardware configuration diagram of the controller 520. As shown in Fig. 4, the controller 520 can be physically configured as a computer device or a circuit board including a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102 and a ROM (Read Only Memory) 103 which are main storage devices, an input device 104 such as a keyboard and a mouse which are input devices, an output device 105 such as a display, a communication module 106 which is a data transmission / reception device such as a network card, an auxiliary storage device 107, and the like.

[0046] 3 are realized by loading predetermined computer software onto hardware such as the CPU 101, RAM 102, etc., to operate the communication module 106, the input device 104, the output device 105, etc. under the control of the CPU 101, and by reading and writing data in the RAM 102 and the auxiliary storage device 107. Among the functions of the controller 520, the adjustment result storage unit 525 can be realized by utilizing a part of the storage device such as the RAM 102 or the auxiliary storage device 107 of the controller 520.

[0047] FIG. 5 is a schematic diagram for explaining the outline of the discharge timing correction control. FIG. 5(A) shows an outline of the procedure of the discharge timing correction control when a web 120 of an arbitrary paper type 1 is used as a recording medium. On the other hand, FIG. 5(B) shows an outline of the procedure of the discharge timing correction control when a web 120 of an arbitrary paper type 2 different from the paper type 1 is used as a recording medium after the correction control by the web 120 of the paper type 1 is performed. In both FIG. 5(A) and (B), one discharge line of each color along the main scanning direction when the control of discharging each color to the same position on the recording medium is performed is shown. In FIG. 5, the black discharge line is shown by a solid line, the cyan discharge line is shown by a dotted line, the magenta discharge line is shown by a dashed line, and the yellow discharge line is shown by a dashed line. In the following description, the discharge lines of each color at the same time are also collectively referred to as line groups L1 to L6.

[0048] In FIG. 5A, first, the ejection timing between the nozzles is adjusted for paper type 1. At this point, as shown in line group L1, there is no deviation in ejection timing for the same color, but there is deviation in ejection timing between colors, and there is also the effect of expansion and contraction of the paper. The example in FIG. 5 illustrates a case in which the paper stretch amount for paper type 1 is relatively small compared to paper type 2. The paper stretch amount is generated in order to apply tension to the recording medium in the transport direction 10 when the recording medium passes through the ejection section 110 in the image forming apparatus 100, stretching the recording medium and eliminating wrinkles and sagging, thereby forming an image on the recording medium with high accuracy.

[0049] Here, as shown by arrow A in FIG. 5A, when correction is made based on detection of the paper behavior, the effect of expansion and contraction of the paper is removed, as shown by line group L2.

[0050] Furthermore, as shown by arrow B in Fig. 5(A), by adjusting the alignment between the colors in this state, the deviation in the ejection timing of each color can be corrected, and the ejection lines of each color are formed overlapping at the same position on the recording medium, as in line group L3. Note that in Fig. 5(A), line group L3 is illustrated without overlapping the ejection lines so that the four color ejection lines can be individually viewed, but in reality, line group L3 is formed by completely overlapping the ejection lines of the four colors.

[0051] Next, consider the case where the recording medium is replaced with paper type 2, as shown in Fig. 5(B). First, the ejection timing between each nozzle is adjusted for paper type 2 as well. At this point, as shown in line group L4, there is no deviation in the ejection timing of the same color, but there is deviation in the ejection timing between colors, and there is also the effect of expansion and contraction of the paper. Also, as described above, the amount of paper expansion of paper type 2 is relatively large compared to paper type 1, so the amount of deviation of the ejection lines of each color in line group L4 is larger than that of line group L1 in Fig. 5(A).

[0052] In this state, when correction based on paper behavior detection is applied as shown by arrow C in Figure 5(B), the effect of paper expansion and contraction is removed, as shown in line group L5. The amount of deviation of the ejection lines of each color in this line group L5 is the same as that of line group L2 in Figure 5(A). This is because line groups L2 and L5 are both after paper behavior detection correction, and so are not affected by the difference in the amount of expansion between paper types 1 and 2.

[0053] As shown by the arrow B in FIG. 5A, the color alignment adjustment has already been performed when adjusting paper type 1. Since the deviation amounts of each color of line group L2 and line group L5 are similar, there is no need to perform color alignment adjustment from line group L5 to line group L6 again. Therefore, as shown by the arrow D in FIG. 5B, by applying the adjustment result for paper type 1, line group L6 can be corrected in the same way as line group L3 after final correction in FIG. 5A without performing new color alignment adjustment for paper type 2. Note that in FIG. 5B, line group L6 is illustrated without overlapping each ejection line so that the four color ejection lines can be individually viewed, but in reality, line group L6 is a set of four color ejection lines that are completely overlapped.

[0054] Therefore, in the ejection timing correction control of this embodiment, among the alignment adjustments (same color, between colors) that were conventionally performed every time the paper type was changed, the alignment adjustment between colors can be omitted and performed only the first time.

[0055] FIG. 6 is a flowchart of the ejection timing correction control according to the embodiment.

[0056] In step S101, various settings are performed. The setting processing performed in this step includes, for example, engine running, head voltage adjustment, main scanning adjustment, sensor SEN adjustment (adjustment of control parameters such as light quantity), and loading of the recording medium (web 120) that is the target of ejection timing correction control into the image forming apparatus 100. The setting processing in this step may be performed automatically by the ejection control unit 521 of the controller 520 or the like, or may be performed manually by an operator, or adjustment information may be input via an input device of the image forming apparatus 100 or the like, and the controller 520 may perform the processing in accordance with the input information.

[0057] In step S102, the conveyance of the recording medium is started, and the ejection unit 110 starts ejecting ink.

[0058] In step S103, same-color alignment adjustment is performed by the same-color alignment adjustment unit 522. The same-color alignment adjustment can include, for example, three steps: (1) analysis of the ejection result, (2) calculation of the ejection timing, and (3) feedback of the timing to the nozzle drive circuit.

[0059] In step S104, the controller 520 determines whether the paper type of the web 120 (i.e., the type of recording medium) has been changed since the previous operation (e.g., the previous execution of the ejection timing correction control). The determination process in this step may be automatically performed by the controller 520 or the like, or an operator may input information on the paper type via an input device of the image forming apparatus 100 or the like, and the controller 520 may make a determination based on the input information.

[0060] If the paper type has not been changed (NO in S104), the process proceeds to step S105, where the paper behavior detection correction unit 523 and the color alignment adjustment unit 524 use the current correction command.

[0061] On the other hand, if the paper type has been changed (YES in S104), the process proceeds to step S106, where the paper behavior detection correction unit 523 performs paper behavior detection correction on the web 120 of the new paper type after the change.

[0062] In step S107, the inter-color alignment adjustment unit 524 determines whether or not the inter-color alignment adjustment has been performed. The inter-color alignment adjustment unit 524 can determine that the inter-color alignment adjustment has been performed when information on the adjustment result is stored, for example, by referring to the adjustment result storage unit 525.

[0063] If color alignment adjustment has already been performed (YES in S107), the process proceeds to step S108, where the adjustment results already stored in adjustment result storage unit 525 are used to omit color alignment adjustment in the current operation.

[0064] If the color alignment adjustment has not been performed (NO in S107), the process proceeds to step S109, where the color alignment adjustment unit 524 performs the color alignment adjustment.

[0065] In step S110, the inter-color alignment adjustment unit 524 stores the adjustment result obtained in step S109 in the adjustment result storage unit 525.

[0066] In step S111, the color alignment adjustment section 524 creates a correction command based on the information obtained in steps S105, S108, and S109, and outputs the command to the liquid ejection head unit 210. When the process of step S111 is completed, this control flow ends.

[0067] After the ejection timing correction control shown in the flowchart of Figure 6 is performed, correction of the ejection timing of the liquid ejection head unit 210 for the web 120 (recording medium) currently installed in the image forming apparatus 100 is completed, and the image forming apparatus 100 becomes capable of printing using this web 120.

[0068] As described above, the image forming apparatus 100 according to the present embodiment includes a paper behavior detection and correction unit 523 that detects the displacement of the ejection positions of the liquid ejection head units 210 in the transport direction 10 on the web 120 according to the type of the web 120 and performs paper behavior detection and correction to correct the ejection timings of the liquid ejection head units 210 so that the ejection positions of the liquid ejection head units 210 are constant regardless of the type of the web 120 based on the detection result of the displacement, and a color alignment adjustment unit 524 that performs color alignment adjustment to correct the ejection timings of the liquid ejection head units 210 so that the ejection positions of the liquid ejection head units 210 are aligned after the paper behavior detection and correction is performed. The color alignment adjustment unit 524 does not perform color alignment adjustment if color alignment adjustment has been completed in the past using another type of web 120.

[0069] With this configuration, by applying ejection timing correction (paper behavior detection correction, first correction) using paper behavior detection during alignment adjustment, it becomes possible to avoid repeating "correction between colors affected by paper expansion and contraction" (inter-color alignment adjustment, second correction). This makes it possible to omit inter-color alignment adjustment when using recording media of different paper types, thereby shortening the time required for alignment adjustment and solving the problem of each process taking time. As a result, the image forming apparatus 100 of this embodiment can improve productivity even when using multiple types of recording media to be printed on.

[0070] Moreover, the image forming apparatus 100 according to the present embodiment includes an adjustment result storage unit 525 that stores the adjustment result of the intercolor alignment adjustment performed by the intercolor alignment adjustment unit 524. When the adjustment result is stored in the adjustment result storage unit 525, the intercolor alignment adjustment unit 524 reuses the adjustment result without performing intercolor alignment adjustment.

[0071] This configuration makes it possible to quickly determine whether or not inter-color alignment adjustment has been performed, thereby further improving productivity.

[0072] <Head abnormality judgment control> In this embodiment, the printed matter after the above-described ejection timing correction control is performed can be used to determine a head abnormality in the liquid ejection head unit 210. As shown in Fig. 3, the controller also has a head abnormality determination unit 526 as a function related to the head abnormality determination control.

[0073] After performing the first correction (paper behavior detection correction) and the second correction (color alignment adjustment), the head abnormality determination unit 526 determines head abnormality in the multiple liquid ejection head units 210 based on the image read by the scanner unit 53. When the head abnormality determination unit 526 determines a head abnormality, it notifies the user of the occurrence of the abnormality via, for example, the notification unit 140 provided in the image forming apparatus 100.

[0074] FIG. 7 is a flowchart of head abnormality determination control according to the embodiment.

[0075] In step S201, the head abnormality determination unit 526 determines whether or not the ejection timing correction control described with reference to Fig. 6 has been performed. If it has been performed (YES in S201), the process proceeds to step S202, and if it has not been performed (NO in S201), the control flow ends.

[0076] In step S202, a command related to head abnormality determination control is output from the head abnormality determination unit 526 to the discharge control unit 521, and test printing for head abnormality determination control is started by the discharge control unit 521. The discharge control unit 521 stores, for example, control command data for test printing in advance, and outputs control commands to the multiple liquid discharge head units 210 using this data.

[0077] In step S203, the scanner unit 53 reads the test print image formed on the web 120 by the multiple liquid ejection head units 210, and obtains a read image of the test print. The scanner unit 53 outputs information about the obtained read image to the head abnormality determination unit 526.

[0078] In step S204, the head abnormality determination unit 526 determines whether or not there is an abnormality in the read image. As a method of determination, for example, the head abnormality determination unit 526 stores image information of a test print when each head of the multiple liquid ejection head units 210 is in a normal state as a sample of evaluation criteria, and compares the read image acquired in step S203 with the sample image. The head abnormality determination unit 526 determines that there is an abnormality in the read image when, for example, there is a difference between the read image and the sample image that is equal to or greater than a predetermined threshold value. Here, the difference between the read image and the sample image includes, for example, misalignment or missing of multiple dots arranged in the image. Furthermore, the head abnormality determined in this step includes, for example, bending of the nozzles of each head and nozzle clogging.

[0079] In step S205, head abnormality determination unit 526 determines whether or not there is an abnormality in the read image. If there is an abnormality (YES in S205), the process proceeds to step S206, in which head abnormality determination unit 526 outputs a command to notification unit 140, which then notifies the occurrence of a head abnormality. Any method of notification can be used, such as an alarm sound, voice, a display on the operation panel of image forming apparatus 100, or the illumination of an alarm lamp. When the process of step S206 is completed, this control flow ends.

[0080] On the other hand, if there is no abnormality in the read image (NO in S205), this control flow ends. At this time, the notification unit 140 may be configured to notify that the head is normal.

[0081] As described above, the image forming apparatus 100 according to this embodiment is provided with a scanner unit 53 that is installed downstream in the transport direction 10 from the multiple liquid ejection head units 210 and reads an image formed on the web 120 by the ejection unit 110, and a head abnormality determination unit 526 that determines a head abnormality in the multiple liquid ejection head units 210 based on the image read by the scanner unit 53 after performing paper behavior detection correction and color-to-color alignment adjustment.

[0082] With this configuration, it is possible to use the correction results of the ejection timing correction control to determine whether or not there is an abnormality in the liquid ejection head unit 210, so that the convenience of the image forming apparatus 100 can be improved.

[0083] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Any design modifications made by a person skilled in the art to these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above-mentioned specific examples and their arrangements, conditions, shapes, etc. are not limited to those exemplified and can be changed as appropriate. The combination of each of the elements of each of the above-mentioned specific examples can be changed as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0084] 100 Image forming device 110 Discharge part 120 Web (recording medium) 210 Liquid ejection head unit 523 Paper behavior detection correction unit (first correction unit) 524 Color Alignment Adjustment Unit (Second Correction Unit) 525 Adjustment result storage section 53 Scanner section 526 Head Abnormality Judgment Unit [Prior art documents] [Patent documents]

[0085] [Patent Document 1] JP 2008-012712 A [Patent Document 2] JP 2015-066851 A

Claims

1. an ejection section having a plurality of liquid ejection head units that eject liquid for forming an image on a recording medium transported in a predetermined direction; a first correction unit that detects a displacement in the predetermined direction of the ejection positions on the recording medium between the plurality of liquid ejection head units according to the type of the recording medium, and performs a first correction based on a detection result of the displacement to correct the ejection timings of the plurality of liquid ejection head units so that the ejection positions of the plurality of liquid ejection head units are constant regardless of the type of the recording medium; a second correction unit that performs a second correction to correct the ejection timings of the liquid ejection head units so that the ejection positions of the liquid ejection head units are aligned after the first correction is performed by the first correction unit; Equipped with the second correction unit does not perform the second correction when the second correction has been completed in the past using another type of recording medium. Image forming device.

2. an adjustment result storage unit that stores an adjustment result of the second correction by the second correction unit; When the adjustment result is stored in the adjustment result storage unit, the second correction unit uses the adjustment result without performing the second correction. The image forming apparatus according to claim 1 .

3. a scanner unit that is disposed downstream of the plurality of liquid ejection head units in the predetermined direction and that reads an image formed on the recording medium by the ejection unit; a head abnormality determination unit that determines a head abnormality of the plurality of liquid ejection head units based on the image read by the scanner unit after the first correction and the second correction are performed; Equipped with 3. The image forming apparatus according to claim 1 or 2.

4. 1. A correction method for an image forming apparatus including an ejection section having a plurality of liquid ejection head units that eject liquid for forming an image on a recording medium transported in a predetermined direction, comprising: a first correction step of detecting a displacement in the predetermined direction of the ejection positions on the recording medium between the plurality of liquid ejection head units according to the type of the recording medium, and performing a first correction based on the detection result of the displacement to correct the ejection timings of the plurality of liquid ejection head units so that the ejection positions of the plurality of liquid ejection head units are constant regardless of the type of the recording medium; a second correction step of performing a second correction after the first correction step, in which the ejection timings of the plurality of liquid ejection head units are corrected so that the ejection positions of the plurality of liquid ejection head units are aligned; Including, the second correction step does not include the second correction if the second correction has been completed in the past using another type of recording medium; A correction method for an image forming apparatus.

5. A correction program for an image forming apparatus including a discharge unit having a plurality of liquid discharge head units that discharge liquid for forming an image on a recording medium transported in a predetermined direction, the correction program comprising: a first correction function that detects a displacement in the predetermined direction of the ejection positions of the liquid ejection head units onto the recording medium according to the type of the recording medium, and performs a first correction based on the detection result of the displacement to correct the ejection timings of the liquid ejection head units so that the ejection positions of the liquid ejection head units are constant regardless of the type of the recording medium; a second correction function that performs a second correction to correct the ejection timings of the liquid ejection head units so that the ejection positions of the liquid ejection head units are aligned after the first correction is performed by the first correction function; on the computer, the second correction function does not perform the second correction when the second correction has been completed in the past using another type of recording medium; A correction program for an image forming apparatus.

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