Image forming apparatus

Abstract

To provide an image forming device configured so that a shift roller which corrects deviation in a main scanning direction of a recording medium such as a sheet can be suppressed from being wasted.SOLUTION: An image forming device comprises: a conveying part that conveys a recording medium; a printing part that forms an image on the recording medium conveyed by the conveying part; a correcting part that detects main-scanning deviation which is deviation in a main scanning direction of the recording medium during conveyance of the recording medium and makes the conveying part correct the main-scanning deviation; an image processing part that shifts a position at which an image is formed with respect to the sheet with a position in a predetermined range in the main-scanning direction as an original point; a detecting part that detects a correction residual error at the time after the main-scanning deviation is corrected by the correcting part; and a determining part that determines a shift amount by which the image processing part shifts the image, on the basis of the correction residual error, where the correcting part switches whether correction by the correcting part should be executed, in accordance with a range where the image can be shifted by the image processing part and the main-scanning deviation.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] A correction technology has been developed that uses a sensor to detect the edge of the paper, detects the deviation in the main scanning direction caused by paper transport (hereinafter referred to as "main scanning deviation") based on the detection result of the paper edge, and corrects the main scanning deviation using a shift roller. [Overview of the project] [Problems that the invention aims to solve]

[0003] However, with the above correction technique, if the accuracy of the preceding paper transport is poor, the amount of paper shifting (the amount requiring correction) becomes large, making it difficult to shift with high precision using the shift roller, and requiring more torque from the shift roller. Furthermore, the above correction technique may shorten the lifespan of the shift roller.

[0004] The present invention has been made in view of the above, and aims to provide an image forming apparatus that can suppress wear of a shift roller that corrects misalignment in the main scanning direction of a recording medium such as paper. [Means for solving the problem]

[0005] To solve the above-mentioned problems and achieve the objective, the present invention provides a transport unit for transporting a recording medium, By a print head in which inkjet heads are lined up in the main scanning direction of the recording medium, A printing unit that forms an image on the recording medium transported by the transport unit, and during the transport of the recording medium The aforementioned A correction unit detects the main scanning deviation, which is a deviation in the main scanning direction, and corrects the main scanning deviation using the transport unit. By nozzle shifting, which changes the position of the image written to the recording medium in the main scanning direction by the print head,The system includes an image processing unit that shifts the position in which an image is formed on the paper with the origin being a predetermined range in the main scanning direction, a detection unit that detects the correction residual after the main scanning misalignment has been corrected by the correction unit, and a determination unit that determines the amount by which the image processing unit shifts the image based on the correction residual. If the main scanning misalignment is greater than the amount obtained by adding a margin to the shiftable range that can be handled by the image shift by the image processing unit, the correction unit repeatedly corrects the main scanning misalignment with the transport unit during a period in which the transport unit can correct the orientation of the recording medium until the main scanning misalignment becomes smaller than the amount obtained by adding a margin to the shiftable range. After the period ends, the image processing unit shifts the position in which an image is formed on the recording medium. [Effects of the Invention]

[0006] The present invention has the effect of suppressing wear on the shift roller that corrects the misalignment of the main scanning direction of a recording medium such as paper. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows an example of the configuration of a line-head type printing press according to this embodiment. [Figure 2] Figure 2 shows an example of the configuration of the image-making unit in the line-head type printing press according to this embodiment. [Figure 3] Figure 3 shows an example of the functional configuration of a line-head type printing press according to this embodiment. [Figure 4] Figure 4 is a diagram illustrating an example of the paper correction function in a line-head type printing press according to this embodiment. [Figure 5] Figure 5 is a diagram illustrating an example of the paper correction function in a line-head type printing press according to this embodiment. [Figure 6] Figure 6 is a diagram illustrating an example of a function for correcting the misalignment of the main scanning direction in the print head of a line-head type printing press according to this embodiment. [Figure 7]FIG. 7 is a diagram for explaining an example of a paper correction function in a conventional line head type printing machine. [Figure 8] FIG. 8 is a diagram for explaining an example of a paper correction function in the line head type printing machine according to the present embodiment. [Figure 9] FIG. 9 is a diagram for explaining an example of a paper correction function in the line head type printing machine according to the present embodiment. [Figure 10] FIG. 10 is a flowchart showing an example of the flow of paper correction processing in the line head type printing machine according to the present embodiment.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of a line head type printing machine will be described in detail with reference to the accompanying drawings.

[0009] FIG. 1 is a diagram showing an example of the configuration of a line head type printing machine according to the present embodiment. As shown in FIG. 1, the line head type printing machine (an example of an image forming apparatus) according to the present embodiment includes an image forming unit 1, a pre-coating unit 2, a paper feeding unit 3, a drying and cooling unit 4, a reversing unit 5, and a paper discharging unit 6.

[0010] The paper feeding unit 3 feeds and conveys sheets of paper (an example of a recording medium) one by one. Since it is difficult for ink to be fixed depending on the paper, the pre-coating unit 2 applies a pre-coating liquid for fixing the ink to the paper in advance. The image forming unit 1 winds the paper around a drum and performs printing on the paper by a line head.

[0011] The drying and cooling unit 4 has a drying unit that dries the moisture of the ink and fixes the ink on the paper. Further, the drying and cooling unit 4 has a cooling unit that cools the paper that has become hot. The reversing unit 5 performs a switchback reversal of the paper during automatic printing on the back side and conveys the paper to the image forming unit 1. The paper discharging unit 6 stacks the printed paper.

[0012] FIG. 2 is a diagram showing an example of the configuration of an image forming unit included in the line head type printing machine according to the present embodiment. As shown in FIG. 2, the image forming unit 1 according to the present embodiment includes a shift roller 11, edge sensors 12, a gripper 13, an inlet cylinder 14, an image forming drum 15, a printing timing sensor 16, a printing head 17, and an outlet cylinder 18.

[0013] The image forming unit 1 detects the deviation in the main scanning direction (hereinafter referred to as the main scanning deviation) and the skew amount of the paper conveyed to the shift roller 11 by the edge sensors 12a and 12b, and corrects the main scanning deviation and the skew amount by the shift roller 11. Here, the main scanning deviation is the deviation of the paper in the main scanning direction. Thereafter, the image forming unit 1 causes the gripper 13 attached to the inlet cylinder 14 and mechanically opened and closed to hold the leading edge of the paper. The inlet cylinder 14, the image forming drum 15, and the outlet cylinder 18 are connected by gears, and convey the paper while changing the holding of the paper by the grippers attached to each of them.

[0014] The printing head 17 is a line head in which a plurality of color (for example, K, C, M, Y) ink jet heads 17a to 17d are connected in the X-axis direction (main scanning direction). The image forming unit 1 ejects ink when the paper passes under the ink jet heads 17a to 17d to form an image on the paper. At that time, the image forming unit 1 determines the printing timing (the timing of ejecting ink onto the paper) based on the timing when the paper passes through the printing timing sensor 16.

[0015] FIG. 3 is a diagram showing an example of the functional configuration of the line head type printing machine according to the present embodiment. As shown in FIG. 3, the line head type printing machine according to the present embodiment roughly includes a paper conveyance device 40 and an image forming device 30.

[0016] The paper conveyance device 40 includes a paper posture detection unit 41, a paper posture correction amount determination unit 42, a paper posture correction unit 43, a correction residual storage unit 44, and a paper conveyance unit 45.

[0017] The paper transport unit 45 has a shift roller 11 and the like, and is an example of a transport unit that transports a recording medium such as paper. The paper attitude detection unit 41 has an edge sensor 12 and the like, and detects the attitude of the paper (for example, the amount of skew and the amount of shift, which is the amount of main scan deviation) when the paper is transported by the paper transport unit 45. The paper attitude detection unit 41 also functions as an example of a detection unit that detects the correction residual of the main scan deviation after the main scan deviation of the paper has been corrected by the paper attitude correction unit 43, which will be described later.

[0018] The paper orientation correction amount determination unit 42 determines the amount of correction for the paper orientation. The paper orientation correction unit 43 corrects the paper orientation based on the correction amount determined by the paper orientation correction amount determination unit 42. The correction residual storage unit 44 stores the correction residual detected by the paper orientation detection unit 41.

[0019] In other words, in this embodiment, the paper orientation detection unit 41, the paper orientation correction amount determination unit 42, and the paper orientation correction unit 43 function as an example of a correction unit that detects the main scanning deviation of the paper when the paper transport unit 45 transports the paper and corrects the main scanning deviation.

[0020] The image forming apparatus 30 includes an image printing unit 31 and an image printing position correction unit 32. The image printing unit 31 has a print head 17, etc., and prints image data onto the paper at the printing timing when the paper transported by the paper transport device 40 is delivered.

[0021] The image print position correction unit 32 functions as an example of an image processing unit that shifts (nozzles shifts) image data with a predetermined range in the main scanning direction as the origin. Here, the predetermined range is a preset range in the main scanning direction. The image print position correction unit 32 also functions as an example of a determination unit that determines the shift amount, which is the amount by which the image print position correction unit 32 shifts the image data, based on the correction residual stored in the correction residual storage unit 44.

[0022] The paper orientation correction unit 43 then switches whether or not to perform correction of the main scan misalignment depending on the shiftable range of the image data and the main scan misalignment. Here, the shiftable range is the range in which the image data can be shifted by the image print position correction unit 32. This minimizes the correction of the main scan misalignment by the shift roller 11 of the paper transport device 40, thereby suppressing wear of the shift roller 11 due to the correction of the main scan misalignment of the recording medium such as paper.

[0023] Specifically, the paper orientation correction unit 43 does not perform correction of the main scan misalignment if the main scan misalignment is within the shiftable range. On the other hand, if the main scan misalignment is outside the shiftable range or near the shiftable range, the paper orientation correction unit 43 reduces the target value for main scan misalignment correction. Furthermore, the paper orientation correction unit 43 repeatedly corrects the main scan misalignment using the paper transport device 40 during the period in which the paper orientation can be corrected by the paper transport unit 45 (hereinafter referred to as the correctionable period).

[0024] Figure 4 is a diagram illustrating an example of the paper correction function in a line-head type printing press according to this embodiment. In this embodiment, the shift roller 11 is a roller that can rotate and move in the Y direction. The shift roller 11 also has the function of correcting (correcting) the skew amount and main scanning deviation calculated based on the edges of the paper 10 detected by a plurality of edge sensors 12 by shifting the paper 10 while transporting the paper 10 in the transport direction (X direction).

[0025] The multiple edge sensors 12a, 12b may be, for example, CIS (Contact Image Sensors). In the example shown in Figure 4, the image-forming unit 1 uses the multiple edge sensors 12a, 12b to determine the skew amount θ of the side surface of the paper 10 with respect to the transport direction of the paper 10. 12 Main scan shift: L 12 Detect and correct for -(dL').

[0026] Here, L 12This is the average value of the distance L1 between the reference point 20 in the main scanning direction and the edge detected by the edge sensor 12a, and the distance L2 between the reference point 20 in the main scanning direction and the edge detected by the edge sensor 12b. Reference numeral 23 indicates the transport center (origin) of the paper 10 in a predetermined range (range indicated by reference numerals 21 and 24) in the main scanning direction, and after the correction of the main scanning misalignment, the paper 10 is transported along the transport center. Furthermore, since correcting the skew amount also changes the main scanning misalignment, the paper orientation correction unit 43 basically repeats the correction of the skew amount and the main scanning misalignment simultaneously (or alternately).

[0027] Figure 5 is a diagram illustrating an example of the paper correction function in a line-head type printing press according to this embodiment. Here, for the sake of simplicity, an example of the paper correction function in a state where no skew occurs will be described. In the example shown in Figure 5, the main scanning misalignment of the paper 10 is Lt = L with respect to the target position 21. 12 Because it is shifted by -(dL'), the paper orientation correction unit 43 shifts the shift roller 11 by Lt in the Y direction (main scanning direction). This allows the center of the paper 10 to be aligned with the transport center 23.

[0028] Figure 6 illustrates an example of a function for correcting misalignment in the main scanning direction at the print head in a line-head type printing press according to this embodiment. The paper position of the paper 10 in the main scanning direction is corrected by the shift roller 11 from the paper position 10a before correction to the target position (origin) 21. On the other hand, the print head 17 (for example, inkjet heads 17a to 17d) has mounting errors (variations) that vary depending on the color. Therefore, the image print position correction unit 32 changes the output position of the image for each color (nozzle shift) by image processing and prints the image on the paper. Here, the mounting error of the print head 17 is uniquely determined at the time of manufacture. Therefore, the image print position correction unit 32 performs a static nozzle shift, shifting the output position of the image for each color by Ra, Rb, Rc, and Rd.

[0029] The range in which nozzle shifting is possible through image processing is Rmax for each color. However, changing the output position through image processing requires memory and image processing speed equal to Rmax, making it difficult to set a large Rmax for large-size, high-speed commercial printing. Therefore, the shift roller 11 corrects (compensates) for the main scan misalignment of the paper 10.

[0030] Figure 7 illustrates an example of a paper correction function in a conventional line-head type printing press. As shown in Figure 6, the paper position of the paper 10 cannot always be fully corrected to the target position 21 by the shift roller 11, and a residual difference ΔR, which is the correction residual of the main scan misalignment, remains. However, the range in which nozzle shift is possible by image processing is, with reference to the target position 21, in the negative direction of R in the main scan direction. - , in the positive direction R + There is just enough room. Here, R - and R + This range of shiftability is common to all inkjet heads 17a to 17d, including the mounting error of each color. Furthermore, in line-head type printers, even if the residual ΔR is added to the mounting error, the output position of each color image can be aligned as long as the range for correcting the paper position of paper 10 is less than or equal to Rmax.

[0031] Therefore, in this embodiment, after correcting the paper position with the shift roller 11, the line head type printing press detects the residual ΔR, which is the correction residual of the main scan misalignment of the paper 10, again with the edge sensor 12. The residual ΔR is then absorbed by image processing, which causes the nozzle to shift the writing position of each document's image by Ra', Rb', Rc', Rd'. Here, the residual ΔR is the amount of dynamic nozzle shift. As a result, even if the residual ΔR varies from page to page, it is possible to cancel the main scan misalignment and print.

[0032] FIG. 8 is a diagram for explaining an example of a paper correction function in the line head type printing machine according to the present embodiment. When the paper 10 is conveyed to the shift roller 11 with the main scanning deviation being 0, if the error (residual ΔR) is within the shiftable range, the paper posture correction unit 43 does not perform position correction in the main scanning direction by the shift roller 11, but instead corresponds by dynamic nozzle shift by the image printing position correction unit 32. Thereby, since the shift amount of the shift roller 11 can always be minimized, it is possible to suppress the wear of the shift roller 11. Here, R0 is the difference between the origin 24 in the main scanning direction and the position of the print head 17 at the time of attachment of the print head 17, and it is assumed that this is acquired in advance when the print head 17 is assembled.

[0033] FIG. 9 is a diagram for explaining an example of a paper correction function in the line head type printing machine according to the present embodiment. When the paper 10 reaches the shift roller 11 and the main scanning deviation is near the range (or outside the range) that can be corresponded by nozzle shift, the paper posture correction unit 43 corrects the main scanning deviation by the shift roller 11. At that time, the paper posture correction unit 43 shifts the shift roller 11 so that the movement amount of the shift roller 11 becomes minimum within the shiftable range that can be corresponded by nozzle shift.

[0034] In the example shown in FIG. 9, the case where the paper 10 is shifted in the + direction in the main scanning direction is taken as an example, but when the residual ΔR becomes larger than R + -Rf, correction by the shift roller 11 is performed so that the paper position after correction becomes R + -Rf. Here, Rf is the margin of the shiftable range by nozzle shift in consideration of various variations. Thereby, as in FIG. 8, since the shift amount of the shift roller 11 can be minimized, it is possible to suppress the wear of the shift roller 11.

[0035] Figure 10 is a flowchart illustrating an example of the paper correction process in a line-head type printing press according to this embodiment. Specifically, Figure 10 shows the flow of the main scan misalignment correction process from when the paper is transported to the shift roller 11 until printing is completed.

[0036] First, the paper orientation detection unit 41 detects the main scanning misalignment ΔR of the paper using the edge sensor 12 (step S1001). Next, the paper orientation correction amount determination unit 42 determines the shiftable range R that the main scanning misalignment ΔR of the paper can be corrected by nozzle shift. + Determine whether or not there is insufficient margin in Rf (step S1002).

[0037] The main scanning misalignment ΔR of the paper can be corrected by nozzle shifting within the adjustable range R. + If there is a margin of Rf (step S1002: No), the paper orientation correction amount determination unit 42 determines the shiftable range R that the main scanning misalignment ΔR of the paper can be corrected by nozzle shift. - Determine whether there is still insufficient margin in Rf (step S1003). The main scanning misalignment ΔR of the paper is within the shiftable range R that can be corrected by nozzle shifting. - If there is more Rf available (step S1003: Yes), the paper orientation correction unit 43 proceeds to step S1006 without correcting the main scan misalignment with the shift roller 11.

[0038] On the other hand, the main scanning misalignment ΔR of the paper can be corrected by nozzle shifting within the shiftable range R. + ,R - If there is less margin than Rf (step S1002: Yes, step S1003: No), the paper posture correction unit 43 corrects the main scan misalignment ΔR with the shift roller 11 by an amount that leaves a margin of Rf within the shiftable range that can be handled by the nozzle shift (steps S1004, S1005). Next, the paper posture correction unit 43 determines whether the correction period for correcting the paper position with the shift roller 11 has ended (step S1006). If the correction period has not ended (step S1006: No), the paper posture detection unit 41 returns to step S1001 and detects the main scan misalignment ΔR of the paper.

[0039] On the other hand, if the correction period ends (step S1006: Yes), the paper orientation detection unit 41 uses the edge sensor 12 to re-detect the main scan misalignment ΔR of the paper (step S1007). Next, the image print position correction unit 32 adds the main scan misalignment ΔR (dynamic nozzle shift amount ΔR) to the mounting error of the print head 17 and prints the image data with the nozzle shifted by the amount of the main scan misalignment ΔR (step S1008).

[0040] Thus, with the line-head type printing press according to this embodiment, the correction of the main scanning misalignment by the shift roller 11 of the paper transport device 40 can be minimized, and wear of the shift roller 11 due to the correction of the main scanning misalignment of the recording medium such as paper can be suppressed.

[0041] In the above embodiment, the image forming apparatus of the present invention is described using an example in which it is applied to a multifunction device having at least two functions from among a copy function, a printer function, a scanner function, and a facsimile function. However, it can be applied to any image forming apparatus such as a copier, printer, scanner, or facsimile device. [Explanation of symbols]

[0042] 1 Image-making unit 2 Pre-coating unit 3. Paper feed unit 4. Drying and cooling unit 5 Reversal Unit 6. Paper output unit 11 Shift roller 12 Edge Sensors 13 Grippa 14 Inlet Cylinder 15. Sculpting Drum 16 Printing timing sensor 17 Print head 18 Outlet Cylinder 30 Image forming apparatus 31 Image printing section 32 Image Print Position Correction Unit 40 Paper transport device 41 Paper orientation detection unit 42 Paper orientation correction amount determination unit 43 Paper posture correction section 44 Corrected residual storage unit 45 Paper transport section [Prior art documents] [Patent Documents]

[0043] [Patent Document 1] Japanese Patent Publication No. 2014-037296

Claims

1. A transport unit that transports the recording medium, A printing unit that forms an image on the recording medium transported by the transport unit using a printing head in which inkjet heads are arranged in the main scanning direction of the recording medium, A correction unit detects the main scanning deviation, which is the deviation in the main scanning direction during the transport of the recording medium, and corrects the main scanning deviation using the transport unit. An image processing unit that shifts the position where an image is formed on the recording medium with a predetermined range in the main scanning direction as the origin by nozzle shifting, which changes the position where the image is written to the recording medium by the print head in the main scanning direction, A detection unit detects the correction residual after the correction of the main scan deviation by the correction unit, The system includes a determination unit that determines the amount of shift to shift the image based on the correction residual, If the main scan misalignment is greater than the amount obtained by adding a margin to the shiftable range that can be handled by the image shifting by the image processing unit, the correction unit will repeatedly correct the main scan misalignment with the transport unit during the period in which the transport unit can correct the orientation of the recording medium until the main scan misalignment becomes smaller than the amount obtained by adding a margin to the shiftable range. The image processing unit shifts the position on the recording medium where the image is formed after the aforementioned period has ended, and is an image forming apparatus.

2. The image forming apparatus according to claim 1, wherein the correction unit does not perform correction of the main scan misalignment by the transport unit when the main scan misalignment is less than the amount obtained by adding a margin to the shiftable range.

Images