JP6187557B2 - Inkjet printer and gap information acquisition method for inkjet printer - Google Patents

Description

  The present invention relates to an inkjet printer that prints on a recording medium by ejecting ink from nozzles, and a gap information acquisition method for the inkjet printer.

  As an inkjet printer that prints on a recording medium by ejecting ink from nozzles, Patent Document 1 discloses that ink is ejected from a recording head (inkjet head) mounted on the carriage while reciprocating the carriage. An ink jet printer that performs printing on a recording sheet (recording medium) is described. In the ink jet printer described in Patent Document 1, the recording sheet is pressed against the recording sheet by pressing the recording sheet against the surface of the platen in which the convex portions and the concave portions are alternately formed in the scanning direction by a conveyance roller or a wavy holding spur. The crests projecting toward the ink ejection surface and the valleys recessed toward the opposite side of the ink ejection surface produce a wave shape alternately arranged along the scanning direction.

JP 2004-106978 A

  Here, in the ink jet printer described in Patent Document 1, the above-described wave shape is generated on the recording sheet, and therefore the gap between the ink ejection surface of the recording head and the recording sheet differs for each portion of the recording sheet. . Therefore, if ink is ejected from the recording head at the same ejection timing as when the waveform is not generated on the recording sheet and printing is performed on the recording sheet, the landing position of the ink landing on the recording sheet is shifted, resulting in a deterioration in image quality. Leads to. At this time, the amount of ink landing position deviation differs for each portion of the recording sheet.

  Therefore, when printing on a recording medium having such a wave shape, in order to land ink at an appropriate landing position of the recording medium, for example, each of the ink discharge surface of the inkjet head and the recording medium It is conceivable to adjust the ejection timing of the ink from the inkjet head in accordance with the gap between the peak portion and the valley portion. For this purpose, it is necessary to acquire information on the gap between the ink ejection surface and each part of the recording medium.

  An object of the present invention is to provide an ink jet printer and an ink jet printer gap information acquisition method capable of easily acquiring information on a gap between an ink ejection surface and each portion of a recording medium having a wave shape. It is to be.

  An ink jet printer according to a first aspect of the present invention is an ink jet head having an ink discharge surface on which nozzles for selectively discharging ink are formed, and a scanning direction parallel to the ink discharge surface with the ink jet head facing a recording medium. The head scanning means for reciprocating the head and the recording medium, the crest portions protruding to the ink ejection surface side and the valley portions recessed to the opposite side of the ink ejection surface along the scanning direction are alternately arranged. However, a wave shape generating mechanism for generating a predetermined wave shape, and a plurality of inspection portions of the recording medium including a peak portion of the peak portion and a valley bottom portion of the valley portion and arranged in the scanning direction. For each, discrete gap information holding means for holding gap information related to the gap between the recording medium and the ink ejection surface, and the discrete gap information Based on the gap information in the plurality of inspection portions held by the information holding means, over the entire region in the scanning direction of at least one of the plurality of sections divided by the plurality of inspection portions of the recording medium, Interpolating gap information calculating means for calculating the gap information.

  According to a ninth aspect of the present invention, there is provided an ink jet printer gap information acquisition method comprising: an ink jet head having an ink ejection surface on which nozzles for selectively ejecting ink are formed; and the ink ejection with the ink jet head facing a recording medium. A head scanning unit that reciprocates in a scanning direction parallel to the surface; a peak portion that protrudes toward the ink ejection surface along the scanning direction; and a valley that is recessed on the opposite side of the ink ejection surface. A method of acquiring gap information related to a gap between the recording medium and the ink ejection surface of an inkjet printer having a wave shape generation mechanism that generates a predetermined wave shape in which portions are alternately arranged, About each of a plurality of inspection parts including the peak part and the valley part of the recording medium and arranged in the scanning direction, Based on the discrete gap information acquisition step for acquiring gap information related to the gap between the recording medium and the ink ejection surface, and the gap information in the plurality of inspection portions acquired in the discrete gap information acquisition step. An interpolation gap information calculation step of calculating the gap information over the entire area in the scanning direction of at least one of the plurality of sections divided by the plurality of inspection portions of the recording medium. It is characterized by that.

  When acquiring information on the gap between the ink ejection surface and each part of the recording medium that caused the wave shape, if all the necessary gap information is retained, the number of gap information becomes enormous. In order to hold the gap information, the memory capacity becomes large.

  On the other hand, in these inventions, since the predetermined wave shape is intentionally generated on the recording medium by the wave shape generation mechanism, the positions of the peak portion and the valley bottom portion of the wave shape can be grasped in advance. Further, the gap between the ink ejection surface and the recording medium becomes maximum and minimum at the peak portion and the valley bottom portion. Therefore, if information related to the gap between the recording medium and the ink ejection surface is acquired at a plurality of inspection portions including the peak portion and the valley bottom portion of the recording medium, based on the acquired plurality of gap information The gap information in each section divided by the peak portion and the valley portion of the recording medium can be calculated. Thereby, even when the number of gap information to be held is small, the gap information can be accurately interpolated.

  The “gap information” may be the gap value itself or other information related to the gap. The peak portion is a portion where the gap is minimized, and the valley bottom portion is a portion where the gap is maximized.

  An ink jet printer according to a second aspect is the ink jet printer according to the first aspect, wherein the interpolation gap information calculation means is based on the gap information in the plurality of inspection portions held by the discrete gap information holding means. The gap information is calculated over the entire scanning direction for an area including all of the plurality of inspection portions of the recording medium.

  According to the present invention, based on gap information acquired in a plurality of inspection portions, gap information can be calculated over the entire region in the scanning direction for a region including all of the plurality of inspection portions.

  An ink jet printer according to a third invention is the ink jet printer according to the first or second invention, wherein the ink jet head and the head scanning means are controlled so that the ink jet is applied to the plurality of inspection portions of the recording medium. A landing position deviation amount in the scanning direction between a landing position of the ink ejected when the head moves in one direction of the scanning direction and a landing position of the ink ejected when the head moves in the other direction of the scanning direction. Pattern printing control means for printing landing deviation detection patterns for detection, respectively, and the discrete gap information holding means includes reading means capable of reading a pattern formed on the recording medium. By making the reading means read the plurality of landing deviation detection patterns, The landing position deviation amount is acquired for each of the inspection portions, and the landing position deviation amount acquisition device is communicably connected to the inspection portion and transmitted from the landing position deviation amount acquisition device. The landing position deviation amount is held as the gap information.

  When the recording medium has a wave shape, the bi-directional landing positions are shifted according to the change in the gap caused by the wave shape. In the present invention, it is possible to acquire the bidirectional landing position deviation amount as information related to the gap.

  An ink jet printer according to a fourth invention is the ink jet printer according to any one of the first to third inventions, wherein the interpolation gap information calculating means includes the gap information of the peak portion and the gap information of the valley portion. And interpolating the gap information in the section between the peak portion and the valley bottom portion with a cubic curve having the peak portion and the valley bottom portion as a maximum value and a minimum value, respectively. To do.

  According to the present invention, since there are four conditions of the maximum and minimum values of the gap information value of the peak portion and the valley bottom portion, and the peak portion and the valley bottom portion, the interpolation can be performed with a cubic function. In addition, it is possible to take gap information of another inspection part between the peak part and the valley part and interpolate with a higher order function, but if the number of gap information to be held increases, memory capacity will be required By using a higher-order function, the amount of calculation increases. That is, a cubic function is optimal for simple and accurate interpolation with a small number of points.

  An ink jet printer according to a fifth aspect of the invention is the ink jet printer according to the fourth aspect of the invention, wherein the wave shape generating mechanism has the wave shape in which the peak portion and the valley bottom portion are arranged at equal intervals on the recording medium. It is characterized by generating.

  According to the present invention, when interpolating with a cubic function, the denominator of this function is the cube of the distance between the peak portion and the valley bottom portion in the scanning direction, but the interval between the peak portion and the valley bottom portion is equal. If so, the distance is constant. Therefore, if the reciprocal of the distance is calculated in advance as a constant, division can be omitted when the gap information is calculated using the cubic function.

  An ink jet printer according to a sixth aspect of the invention is the ink jet printer according to any one of the first to fifth aspects, wherein the ink jet head ejects ink from the nozzle while moving in the scanning direction. It further comprises discharge timing determining means for determining discharge timing based on the gap information calculated for the one section by the interpolation gap information calculating means.

  According to the present invention, by determining the ejection timing based on the calculated gap information, it is possible to land ink at an appropriate position on the recording medium in which the waveform is generated.

  An ink jet printer according to a seventh aspect of the invention is the ink jet printer according to the sixth aspect of the invention, further comprising position detecting means for detecting the position of the ink jet head in the scanning direction, and during movement of the ink jet head in the scanning direction. The interpolation gap information calculation means calculates the gap information at this position from the position information of the inkjet head detected by the position detection means, and the ejection timing determination means further includes the interpolation gap information calculation means. The nozzle discharge timing is determined using the calculated gap information.

  According to the present invention, there is no need for a memory for storing gap information for the entire area by sequentially calculating gap information during head movement. In addition, when gap information for the entire area is stored, if gap information in a part of the area changes due to later adjustments or the like, it is necessary to individually change the stored gap information of the area. In the present invention, since gap information is sequentially calculated, it is easy to change gap information even in such a case.

  An ink jet printer according to an eighth aspect of the present invention is the ink jet printer according to any one of the first to seventh aspects, wherein the discrete gap information holding means uses the plurality of gap information as an average value of the plurality of gap information. And a deviation from the average value for each of the plurality of gap information.

  According to the present invention, by storing gap information of a plurality of inspection portions separately for the average value and the deviation, the average value and the deviation can be adjusted independently.

  According to the present invention, if information related to the gap between the recording medium and the ink ejection surface is acquired at a plurality of inspection portions including the crest portion and the valley bottom portion of the recording medium, the acquired plurality of gaps Based on the information, it is possible to calculate gap information in each section divided by the peak portion and the valley bottom portion of the recording medium. Thereby, even when the number of gap information to be held is small, the gap information can be accurately interpolated.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment of the present invention. It is a top view of a printing part. (A) is the figure which looked at FIG. 2 from the direction of arrow IIIA, (b) is the figure which looked at FIG. 2 from the direction of arrow IIIB. 4A is a cross-sectional view taken along the line IVA-IVA in FIG. 2, and FIG. 4B is a cross-sectional view taken along the line IVB-IVB in FIG. It is a functional block diagram of a control device. It is a flowchart which shows the process performed before printing among the procedures which determine the discharge timing of an ink. (A) is a figure which shows the landing deviation detection pattern and the reading position which were printed on the recording paper, (b) is a figure which expanded an example of (a) and showed an example of the landing deviation detection pattern It is. (A) is the relationship between the position and height of the recording sheet in the scanning direction, (b) is the relationship between the position in the scanning direction and the amount of landing position deviation in the scanning direction, and (c) is the sheet at the intersection of the scanning direction and the pattern. FIG. 6D is a diagram illustrating a relationship between a shift amount in a feeding direction and a relationship between a position in a scanning direction and a delay amount of ejection timing. It is a flowchart which shows the process performed at the time of printing among the procedures which determine the discharge timing of an ink. It is a block diagram equivalent to FIG. 5 of one modification.

  Hereinafter, preferred embodiments of the present invention will be described.

  The ink jet printer 1 according to the present embodiment is a so-called multi-function machine capable of performing printing on the recording paper P and reading of an image. The ink jet printer 1 includes a printing unit 2 (see FIG. 2), a paper feeding unit 3, a paper discharging unit 4, a reading unit 5, an operation unit 6, a display unit 7, and the like. The operation of the ink jet printer 1 is controlled by the control device 50 (see FIG. 5).

  The printing unit 2 is provided inside the inkjet printer 1 and performs printing on the recording paper P. The detailed configuration of the printing unit 2 will be described later. The paper feed unit 3 is a part for supplying the recording paper P to be printed by the printing unit 2. The paper discharge unit 4 is a part from which the recording paper P printed by the printing unit 2 is discharged. The reading unit 5 is a scanner or the like, and is a part that reads an image. The operation unit 6 includes buttons and the user performs necessary operations on the inkjet printer 1 by operating the buttons and the like of the operation unit 6. The display unit 7 is a liquid crystal display or the like, and displays information necessary when the ink jet printer 1 is used.

  Next, the printing unit 2 will be described. As shown in FIGS. 2 to 4, the printing unit 2 includes a carriage 11 (head scanning unit), an inkjet head 12, a paper feed roller 13, a platen 14, a plurality of corrugated plates 15, a plurality of ribs 16, and a paper discharge roller 17. A plurality of corrugated spurs 18 and 19 are provided. However, in FIG. 2, in order to make the drawing easy to see, the carriage 11 is illustrated by a two-dot chain line, and a portion positioned below the carriage 11 is illustrated by a solid line.

  The carriage 11 is reciprocated in the scanning direction while being guided by a guide rail (not shown). The inkjet head 12 is mounted on the carriage 11 and ejects ink from a plurality of nozzles 10 formed on the ink ejection surface 12a which is the lower surface thereof.

  The paper feed rollers 13 are a pair of rollers, and convey the recording paper P supplied from the paper feed unit 3 in a paper feed direction perpendicular to the scanning direction. The platen 14 is disposed so as to face the ink ejection surface 12 a, and the recording paper P conveyed by the paper feed roller 13 is conveyed along the upper surface of the platen 14.

  The plurality of corrugated plates 15 are arranged so as to face the upper surface of the upstream end of the platen 14 in the paper feeding direction, and are arranged at substantially equal intervals in the scanning direction. The recording paper P conveyed to the paper supply roller 13 passes between the platen 14 and the corrugated plate 15, and the plurality of corrugated plates 15 press the recording paper P from above by a pressing surface 15 a that is the lower surface thereof.

  The plurality of ribs 16 are arranged on the upper surface of the platen 14 between the corrugated plates 15 in the scanning direction, and are arranged at almost equal intervals in the scanning direction. Each of the ribs 16 protrudes from the upper surface of the platen 14 to above the pressing surface 15a of the corrugated plate 15, and extends from the upstream end of the platen 14 in the paper feeding direction toward the downstream side in the paper feeding direction. Yes. Thereby, the recording paper P on the platen 14 is supported from below by the plurality of ribs 16.

  The paper discharge rollers 17 are a pair of rollers, and convey the recording paper P toward the paper discharge unit 4 in the paper feed direction across a portion at the same position as the plurality of ribs 16 in the scanning direction of the recording paper P. To do. Of the pair of paper discharge rollers 17, the upper paper discharge roller is a spur so that ink that has landed on the recording paper P does not easily adhere.

  The plurality of corrugated spurs 18 are disposed at substantially the same position as the corrugated plate 15 in the scanning direction on the downstream side in the paper feeding direction of the paper discharge roller 17. The plurality of corrugated spurs 19 are disposed at substantially the same position as the corrugated plate 15 in the scanning direction on the downstream side of the plurality of corrugated spurs 18 in the paper feeding direction. The plurality of corrugated spurs 18 and 19 are positioned below the position where the paper discharge roller 17 sandwiches the recording paper P in the vertical direction, and the recording paper P is pressed from above at this position. The corrugated spurs 18 and 19 are not spur rollers with a flat outer peripheral surface, but are spurs, so that the ink that has landed on the recording paper P is difficult to adhere.

  Then, the recording paper P on the platen 14 is bent by being pressed from above by the plurality of corrugated plates 15 and the plurality of corrugated spurs 18 and 19 and supported by the plurality of ribs 16 from below, as shown in FIG. In this manner, the peak portion Pm protruding upward (ink discharge surface 12a side) and the valley portion Pv recessed downward (opposite side of the ink discharge surface 12a) are alternately arranged in a wave shape. In addition, the peak portion Pm is a peak portion Pt that protrudes the largest to the upper side at a portion that is substantially in the same position as the central portion of the rib 16 in the scanning direction. Further, the valley portion Pv is a valley bottom portion Pb that is recessed at the lowest side in a portion that is substantially the same position as the corrugated plate 15 and the corrugated spurs 18 and 19 in the scanning direction. In the present embodiment, the combination of the corrugated plate 15, the rib 16, and the corrugated spurs 18, 19 that make the recording paper P corrugated corresponds to the corrugated generating mechanism according to the present invention.

  The encoder sensor 20 is mounted on the carriage 11. The encoder sensor 20 forms a linear encoder together with an encoder belt (not shown) extending in the scanning direction, and the position of the inkjet head 12 moved in the scanning direction by the carriage 11 by detecting a slit formed in the encoder belt. Is detected.

  In the printing unit 2 having the above-described configuration, the recording paper P is transported in the paper feed direction by the paper feed roller 13 and the paper discharge roller 17, and ink is ejected from the inkjet head 12 that reciprocates in the scanning direction together with the carriage 11. By discharging, printing is performed on the recording paper P.

Next, the control device 50 for controlling the operation of the inkjet printer 1 will be described. The control device 50 includes a central processing unit (CPU) and a read only memory (ROM).
), A RAM (Random Access Memory), a control circuit, and the like. These are, as shown in FIG. 5, a recording control unit 51, a reading control unit 52, a deviation amount storage unit 53 (discrete gap information holding means), an interpolation. It functions as a function determination unit 54, a head position detection unit 55, a deviation amount calculation unit 56, a discharge timing determination unit 57, and the like. In the present embodiment, the combination of the interpolation function determination unit 54 and the deviation amount calculation unit 56 corresponds to the interpolation gap information calculation unit according to the present invention.

  The recording control unit 51 controls operations of the carriage 11, the ink jet head 12, the paper feed roller 13, the paper discharge roller 17, and the like when performing printing in the ink jet printer 1. The reading control unit 52 controls the operation of the reading unit 5 when reading an image.

  As will be described later, the deviation amount storage unit 53 obtains the deviation amount in the paper feed direction of the intersections of the plurality of peak portions Pt and valley bottom portions Pb of the recording paper P acquired from the landing deviation detection pattern (hereinafter referred to as intersection deviation amount). (Discrete gap information) is stored (retained). The interpolation function determination unit 54 determines an interpolation function for interpolating the intersection deviation amount in the entire scanning direction of the area of the recording paper P that has a wave shape from the intersection deviation amount stored in the deviation amount storage unit 53.

  The head position detection unit 55 detects the position of the inkjet head 12 reciprocated in the scanning direction by the carriage 11 during printing from the detection result of the encoder sensor 20. As will be described later, the misregistration amount calculation unit 56 uses the position of the inkjet head 12 detected by the head position detection unit 55, the interpolation function calculated by the interpolation function determination unit 54, and the like to detect the misalignment at each portion of the recording paper P. Calculate the amount.

  The discharge timing determination unit 57 determines the discharge timing of the ink from the nozzles 10 based on the intersection shift amount calculated by the shift amount calculation unit 56.

  Next, a description will be given of a procedure for determining the ink ejection timing from the nozzle 10 and performing printing in the inkjet printer 1. In order to determine the ejection timing of ink from the nozzle 10 and perform printing, as described below, before the user performs printing using the inkjet printer 1, such as at the manufacturing stage of the inkjet printer 1, As shown in FIG. 6, the processing of steps S101 to S103 (hereinafter simply referred to as S101, S102, S103, etc.) is executed. And when a user prints using the inkjet printer 1, as shown in FIG. 9, the process of S201-S205 is performed.

  In S101, the inkjet printer 1 prints a patch T including a plurality of landing deviation detection patterns Q as shown in FIG. 7 on the recording paper P (pattern printing step). More specifically, for example, by ejecting ink from the nozzle 10 while moving the carriage 11 in one direction in the scanning direction, each of the plurality of straight lines extends in parallel with the paper feed direction and is arranged in the scanning direction. L1 is printed. Thereafter, ink is ejected from the nozzles 10 while moving the carriage 11 in the other direction of the scanning direction, so that each of them is inclined with respect to the paper feed direction, and a plurality of straight lines L2 that respectively overlap with the plurality of straight lines L1 are printed. Let As a result, as shown in FIG. 7, a patch T in which a plurality of landing deviation detection patterns Q each formed by a set of straight lines L1 and L2 intersecting each other is arranged along the scanning direction is printed. At this time, the ink is ejected from the nozzles 10 at the design ejection timing when the recording paper P is not wave-shaped and is flat.

  In S <b> 102, a plurality of landing deviation detection patterns Q printed in S <b> 101 are read by a dedicated scanner 61 (reading unit) provided separately from the inkjet printer 1, and the landings read by the PC 62 connected to the scanner 61 are read. From the deviation detection pattern Q, the amount of intersection deviation in a plurality of peak portions Pt and valley bottom portions Pb is acquired.

  More specifically, for example, when the landing deviation detection pattern Q as shown in FIG. 7 is printed, the straight lines L1 and L2 are landing positions when the carriage 11 is moved to the right and to the left in the scanning direction. If there is misalignment, printing is performed with a shift in the scanning direction. Therefore, the intersection between the straight line L1 and the straight line L2 (hereinafter referred to as a pattern intersection) is shifted in the paper feed direction between the straight line L1 and the straight line L2 in accordance with the amount of landing position deviation in the scanning direction. Further, when the landing deviation detection pattern Q is read by the reading unit 5, the ratio of the area occupied by the straight lines L1 and L2 (black) to the ground portion (white) of the recording paper P at the pattern intersection becomes small. The detected luminance becomes higher. Therefore, by reading the landing deviation detection pattern Q and acquiring the position in the paper feed direction of the portion with the highest luminance, the position in the paper feed direction where the straight line L1 and the straight line L2 overlap can be detected.

  Here, the change in the overlapping position of the straight line L1 and the straight line L2 in the paper feeding direction is proportional to the change in the overlapping position in the scanning direction. Specifically, if the relative inclination of the straight line L1 and the straight line L2 is 10: 1 in the paper feed direction: scanning direction, the change in the overlapping position of the straight line L1 and the straight line L2 in the paper feed direction is the scanning direction. The information is obtained by amplifying the fluctuation of the overlapping position 10 times. In general, when the angle between the straight line L1 and the straight line L2 is θ, the shift amount in the paper feed direction of the pattern intersection is information obtained by amplifying the shift amount in the scanning direction by 1 / tan θ times. That is, by detecting the shift amount of the pattern intersection in the paper feed direction, it is possible to acquire information on the landing position shift amount in the main scanning direction in bidirectional printing.

  Therefore, in the present embodiment, among the plurality of landing deviation detection patterns Q, the peak portion Pt and the valley bottom portion Pb of the recording paper P (the portions surrounded by the alternate long and short dash line in FIG. 7A, hereinafter these are collectively inspected. By reading the landing deviation detection pattern Q printed on the portion Pe), the amount of intersection deviation at each peak portion Pt and each valley bottom portion Pb is acquired. In the present embodiment, the combination of S101 and S102 described above corresponds to the discrete gap information acquisition step according to the present invention, and the combination of the scanner 61 and the PC 62 corresponds to the landing according to the present invention. This corresponds to a positional deviation amount acquisition means.

  In S102, as described above, only the landing deviation detection pattern Q printed on the peak portion Pt and the valley bottom portion Pb of the recording paper P is read. Therefore, in S101, the landing deviation detection pattern at least on the mountain peak portion Pt and the valley bottom portion Pb is read. Q can be printed.

  In S103, as shown by a broken line in FIG. 5, the PC 62 and the shift amount storage unit 53 are communicably connected, and the intersection shift amount obtained in S102 at each peak portion Pt and valley bottom portion Pb is stored as a shift amount. The data is written in the unit 53 and stored. The connection between the PC 62 and the deviation amount storage unit 53 may be made at any timing as long as it is before S103.

  Here, the amount of deviation of the landing position varies depending on the position of the recording paper P in the scanning direction because the recording paper P has a wave shape. On the other hand, whether or not the recording paper P has a wave shape. Regardless, it changes if the overall height of the recording paper P, the moving speed of the carriage 11, the flying speed of ink droplets, and the like change.

  In other words, the amount of intersection misalignment acquired in S102 is the same as the height of the entire recording sheet P regardless of the portion that is generated when the recording sheet P has a waveform and the recording sheet P has a waveform. It consists of a portion generated according to the movement speed of the carriage 11. Therefore, the intersection deviation amount can be represented by an average value of the intersection deviation amounts in the plurality of inspection portions Pe and a deviation from the average value. Therefore, in S103, the intersection shift amount is divided into the average value and the deviation and stored in the shift amount storage unit 53.

  In S104, the interpolation function determination unit 54 covers the entire scanning direction of the wavy region of the recording paper P from the intersection shift amount in each peak portion Pt and valley bottom portion Pb stored in the shift amount storage unit 53 in S103. An interpolation function G (X) for calculating the intersection shift amount is determined.

  More specifically, as described above, when the recording paper P has a wave shape along the scanning direction, the horizontal axis indicates the position X in the scanning direction, and the vertical axis indicates the height in the vertical direction of the paper. When using Z to illustrate, it becomes as shown in FIG. Here, the position along the scanning direction of the Nth inspection portion is represented as XN. SN represents a section from X = XN to X = XN + 1. Here, the section width L = XN + 1−XN is constant regardless of N. At this time, the height Z of the recording paper P in the section SN can be expressed as Z = HN (X) using a certain function HN (X) for X. A combination of these functions HN (X) for each N for all intervals is expressed as Z = H (X).

  In FIG. 8B, the horizontal axis represents the position X in the scanning direction and the vertical axis represents the landing position deviation W = F (X) in the scanning direction. When the landing position deviation in the scanning direction when Z = Z0 is W0, (ink droplet movement distance) = (ink droplet velocity) × (ink flying time), and scanning is performed in the vertical direction during the same ink flying time. Since the ink droplets move in the respective directions (vertical ink droplet movement distance) / (vertical ink droplet velocity) = (scanning direction ink droplet movement distance) / (scanning direction ink droplet velocity), that is, (Z−Z0) / U = (W−W0) / V. However, V is the carriage speed in the scanning direction, and U is the ink flying speed in the vertical direction. Since Z0, W0, U, and V are constants that do not change depending on the value of X, Z = H (X) and W = F (X) are essentially similar graphs. FIG. 8C also shows the position X in the scanning direction on the horizontal axis and the pattern intersection position deviation Y = G (X) in the paper feeding direction on the vertical axis. As described above, since Y = W / tan θ, Y = G (X) is a graph similar to Z = H (X) and W = F (X).

  Therefore, as shown in FIGS. 8B and 8C, the change in the landing position deviation amount W in the scanning direction and the change in the intersection deviation amount Y corresponding to the position X in the scanning direction are also caused by the change in the recording paper P. It can be represented by a graph that can be overlapped only by the change in the height Z, the expansion and contraction of the vertical axis, and the parallel movement. That is, the graph of the interpolation function G (X) of the intersection deviation amount Y is obtained by the interpolation function H (X) of the height Z and the interpolation function F (X (X) of the landing position deviation amount W by the expansion and contraction and translation of the vertical axis. ).

  The graph of FIG. 8D (discharge timing correction amount graph) to be described later is also the same, and these four pieces of information are essentially equivalent when the related constants are known. Regardless of which one of the three pieces of information is stored or any of the four pieces of information is used for the interpolation calculation, the landing correction can be performed by appropriate conversion. Here, it is assumed that the intersection deviation amount Y is stored.

  The interpolation function G (X) is calculated individually for each section delimited by the inspection portion Pe. Among these interpolation functions, the deviation of the pattern intersection in the paper feed direction in the section SN having both ends of the Nth and N + 1th (N = 1, 2, 3,...) Inspection portions Pe from the left side in the scanning direction. Assuming that the interpolation function of the quantity Y is the interpolation function GN (X), the interpolation function GN (X) assumes that the positions in the scanning direction of the Nth and N + 1th inspection parts Pe from the left are XN and XN + 1, respectively. From the relationship with the deviation amount Y of the pattern intersection in the paper feed direction stored in the deviation amount storage unit 53, it is necessary to satisfy the following two conditional expressions. Here, YN is an intersection deviation amount in the inspection portion Pe at the position X = XN, and YN + 1 is an intersection deviation amount in the inspection portion Pe at the position X = XN + 1.

  Furthermore, in order to make the interpolation function GN (X) a function that is continuously and smoothly connected to the interpolation functions GN-1 (X) and GN + 1 (X) in the adjacent sections SN-1 and SN + 1, the interpolation function GN (X ) Requires that the interpolation functions GN-1 (X) and GN + 1 (X) in the adjacent sections and the first derivative with respect to X are continuous in the peak portion Pt and the valley bottom portion Pb, respectively. By the way, here, both ends of each section S are positions where the corrugated shape has a peak (maximum value) or a valley bottom (minimum value), so the first derivative at that position is zero. Therefore, the first-order differential G′N (X) with respect to X of the interpolation function GN (X) only needs to satisfy the following two conditional expressions.

  If the interpolation function GN (X) is to be expressed by a polynomial of coordinates X in the scanning direction of the recording paper P, the polynomial can be determined using the above four conditional expressions as boundary conditions. Therefore, the interpolation function GN (X ) Can be expressed by a cubic function. Specifically, a cubic function satisfying the above four conditional expressions is as follows.

  The interpolation function GN (X) is an interpolation function of the intersection deviation amount Y. However, the above relational expressions show that YN + 1, YN, and GN (X) are YN + 1−Y0, YN−Y0, and GN (X) −Y0, respectively. Even if it replaces, it holds equally (no matter how many values of Y0). That is, the following relationship is established.

  This function can be used as a function for calculating the absolute value of the intersection deviation amount at an arbitrary position by substituting the absolute value of the intersection deviation amount, or by substituting the deviation from a certain value (Y0) of the intersection deviation amount. It can also be used as a function for calculating a deviation from a certain value of the amount of misalignment at an arbitrary position. Therefore, the maximum / minimum intersection shift amount stored in the shift amount storage unit 53 may be expressed as a value based on any value Y0, but in this embodiment, the average value of Y in all sections is used. Let's say Y0.

  In step S <b> 201, during the movement of the carriage 11, the head position detection unit 55 detects the position in the scanning direction of the inkjet head 12 that reciprocates in the scanning direction together with the carriage 11.

  In S <b> 202, an intersection shift amount in each part of the recording paper P is calculated. Specifically, during the movement of the inkjet head 12 by the carriage 11, the position of the inkjet head 12 detected in S201 (corresponding to X of the interpolation function GN (X)) and the interpolation function corresponding to the detected position. The intersection shift amount Y = G (X) is sequentially calculated from GN (X). In the present embodiment, the combination of S104 and S202 corresponds to the interpolation gap information calculation step according to the present invention.

  In S203, the ejection timing of the ink from the nozzle 10 is determined based on the intersection shift amount calculated in S202. More specifically, [H (X) −Z0]: [F (X) −W0] = U: V. Further, if the angle formed by the straight line L1 and the straight line L2 in the landing deviation detection pattern Q is θ, [F (X) −W0]: [G (X) −Y0] = sin θ: cos θ. If the function of the delay time D from the original discharge timing is E (X), F (X) −W0 = V · (E (X) − D0) holds. From these relationships, E (X) is as follows.

  FIG. 8D is a graph showing the relationship D = E (X). And this graph can also be overlapped with the graphs of FIGS. 8A to 8C by expansion and contraction of the vertical axis and parallel movement.

  In S204, ink is ejected from the nozzles 10 at the ejection timing determined in S203. Until the printing is completed (S205: NO), the operations of S201 to S204 are repeated. When the printing is completed (S205: YES), the operation is terminated. In this embodiment, since the ink is ejected from the nozzle 10 in response to a signal from the encoder sensor 20 when the inkjet head 12 reaches a predetermined position, the ink is ejected at an earlier timing than the original ejection timing. Discharging is difficult. Therefore, the value of D0 is always selected such that D ≧ 0.

  According to the embodiment described above, when the recording paper P has a wave shape in which a plurality of crest portions Pm and a plurality of trough portions Pv are alternately arranged in the scanning direction, the gap between the ink ejection surface 12a and the recording paper P. Varies for each portion of the recording paper P. On the other hand, when the gap between the ink ejection surface 12a and the recording paper P is different, if ink is ejected from the nozzles 10 at the same ejection timing as when the recording paper P is flat, the carriage 11 is moved in the scanning direction. The amount of deviation between the landing position of ink ejected from the nozzle 10 while moving to the right side and the landing position of ink ejected from the nozzle 10 while moving the carriage 11 to the left side in the scanning direction is recorded on the ink ejection surface 12a. It changes according to the gap with the paper P. Therefore, when the recording paper P has such a wave shape, in order to land ink at an appropriate position, the ink ejection timing from the nozzle 10 is set according to the gap for each portion of the recording paper P. It is necessary to decide.

  On the other hand, in the present embodiment, the landing deviation detection pattern Q is printed on the recording paper P having a wave shape, and the printed landing deviation detection pattern Q is read, so that the peak portion Pt and the valley bottom portion Pb are read. Is obtained by dividing the obtained intersection deviation amount into an average value Y0 and a deviation Y-Y0 from the average value Y0 and storing it in the deviation amount storage unit 53. Then, the interpolation function GN (X) is calculated from the stored deviation Y-Y0 of the intersection deviation amount. As a result, from the average value Y0, the deviation Y-Y0 of the intersection deviation amount, and the interpolation function GN (X), the intersection deviation amount of each part of the recording paper P is changed over the entire scanning direction of the wave-shaped region (all It can be acquired over the entire scanning direction of the region including the inspection portion Pe.

  Then, at the time of printing, a wave shape is obtained by determining the ejection timing of the ink from the nozzle 10 based on the position of the inkjet head 12 and the ejection timing delay amount D calculated from the interpolation function GN (X) or the like. Ink can be landed at an appropriate position on the recording paper P.

  At this time, it is not necessary to obtain the intersection deviation amount in all the portions of the recording paper P in the scanning direction in the entire area in the scanning direction from the landing deviation detection pattern Q, but the intersection deviation amount in the peak portion Pt and the valley bottom portion Pb. And the interpolation function GN (X) is calculated from the acquired intersection deviation amount, and the intersection deviation amount of each part of the recording paper P is calculated from the average value Y0 of the intersection deviation amount and the interpolation function GN (X). Acquired over the entire scanning direction of the waveform area. For this reason, the intersection deviation amount of each part of the recording paper P is a wave-shaped area while reducing the number of intersection deviation amounts stored in the deviation amount storage unit 53 and suppressing the capacity of the RAM or the like of the control device 50 to be low. Can be obtained over the entire scanning direction.

  At this time, as described above, the interpolation function GN (X) can be a cubic function. Here, in S102, if the intersection shift amount in the portion between the peak portion Pt and the valley bottom portion Pb of the recording paper P is further acquired as the intersection shift amount in the inspection portion, the number of conditional expressions increases, and the interpolation function GN. It is also possible to calculate (X) as a polynomial having a quartic function or higher.

  However, in this case, the number of intersection shift amounts stored in the shift amount storage unit 53 increases, and the capacity of the RAM of the control device 50 needs to be increased. In addition, since the number of conditional expressions increases, the amount of calculation for calculating the interpolation function GN (X) in S104 increases. In addition, since the interpolation function GN (X) is a higher-order function, the amount of calculation when calculating the intersection shift amount in S202 also increases.

  Therefore, when the intersection deviation amount is interpolated with a polynomial, it is calculated as a cubic function from the viewpoint of reducing the number of intersection deviation amounts to be obtained and calculating the interpolation function GN (X) easily and accurately. Is optimal.

  Further, the denominator of the first term of the interpolation function GN (X) is (XN + 1−XN) 3. As described above, the corrugated plate 15, the rib 16, and the corrugated spurs 18 and 19 are scanned. When arranged at equal intervals in the direction, the value of (XN + 1−XN) corresponding to the distance in the scanning direction between the adjacent peak portion Pt and valley bottom portion Pb is constant, and the value of the denominator is also constant. Here, the computer generally requires time for division rather than multiplication, but when the value of (XN + 1−XN) is constant, the value of 1 / (XN + 1−XN) 3 is calculated in advance. When calculating the deviation D from the interpolation function GN (X), instead of performing an operation of dividing by (XN + 1−XN) 3, an operation of multiplying by a previously calculated constant 1 / (XN + 1−XN) 3 is performed. Thus, the time required for calculating the interpolation function GN (X) can be shortened.

  In the present embodiment, in S202, the position of the inkjet head 12 is acquired during the movement of the carriage 11 during printing, and the acquired position of the inkjet head 12 and the interpolation function GN (X) corresponding to the position are acquired. The intersection deviation amount is sequentially calculated from the deviation Y-Y0 of the intersection deviation amount and the average value Y0 of the intersection deviation amounts acquired by the above, and the ink ejection timing from the nozzle 10 is determined based on the calculated intersection deviation amount. It is determined sequentially.

  Therefore, it is not necessary to calculate the intersection shift amount for the entire region in advance and perform the calculation in the RAM of the control device 50 before printing. Therefore, the capacity of the RAM of the control device 50 can be reduced. Further, if the intersection deviation amount for the entire area is stored in the RAM of the control device 50, the intersection deviation amount in a part of the area changes when the position of the corrugated plate 15 is adjusted later. It is necessary to individually change the amount of deviation of the intersections of the areas stored in the RAM or the like. On the other hand, in the present embodiment, since the intersection shift amount is sequentially calculated, even in such a case, the intersection shift in the mountain peak portion Pt and the valley bottom portion Pb corresponding to the region stored in the shift amount storage unit 53. By simply changing the amount and calculating the interpolation function GN (X) from the changed intersection deviation amount, the intersection deviation amount of the entire region can be easily changed to the adjusted intersection deviation amount.

  In the present embodiment, in S103, the intersection deviation amount Y in the inspection portion Pe is divided into the average value Y0 and the deviation Y-Y0 from the average value Y0, and is stored in the deviation amount storage unit 53. Since the interpolation function GN (X) of the deviation D is calculated in FIG. 6, when the amplitude of the wave shape (the difference in height between the peak portion Pt and the valley bottom portion Pb) is changed by subsequent adjustment or the like, the deviation Y−Y0 The average value Y0 and the deviation Y−Y0 can be individually adjusted, for example, by adjusting the average value Y0 when the overall height of the recording paper P or the moving speed of the carriage 11 changes.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, the description of the same configuration as the present embodiment will be omitted as appropriate.

  In the above-described embodiment, the misalignment amount storage unit 53 stores the intersection misalignment amount Y in the inspection portion Pe by dividing it into the average value Y0 and the deviation from the average value Y0. Absent. The displacement amount storage unit 53 may store the value of the intersection displacement amount Y (such as the value of YN in FIG. 8A) itself in the inspection portion Pe.

  Further, the landing position deviation amount W in the main scanning direction in the inspection portion Pe, the ejection timing delay amount D to be applied in the inspection portion Pe, or a value obtained by increasing or decreasing a certain value thereof may be stored.

  In the above-described embodiment, in S203, while the inkjet head 12 is moving at the time of printing, the intersection shift amount in the portion corresponding to the position of the inkjet head 12 of the recording paper P is sequentially calculated, and the calculated intersection shift is calculated. The ink ejection timing is determined based on the amount, but is not limited thereto. For example, before printing, from the intersection deviation amount Y acquired from the interpolation function GN (X) in advance, the intersection deviation amount is calculated for the entire region of the waveform area, and all the calculated intersection deviation amounts are calculated by the control device 50. The ink ejection timing may be determined based on the stored intersection shift amount at the time of printing.

  In the above-described embodiment, the corrugated plate 15, the rib 16, and the corrugated spurs 18 and 19 are arranged at equal intervals in the scanning direction, but these intervals may not be equal.

  In the above-described embodiment, the interpolation function GN (X) is calculated as a cubic function. However, as described above, the interpolation function GN (X) may be calculated as a function of a fourth or higher order polynomial. Alternatively, the rate of change with respect to X of the function at a position where the interpolation function GN (X) in the section SN is connected to the interpolation function GN + 1 (X) in the adjacent section SN + 1 is obtained separately, and this is used as a boundary condition to obtain a third order The interpolation function G (X) may be determined as a multiple simultaneous equation. Alternatively, if the interpolation function GN (X) does not have to be smoothly connected to the adjacent sections SN-1, SN + 1, the interpolation functions GN-1 (X), GN + 1 (X), the interpolation function GN (X) is It is good also as a function of the polynomial below quadratic. Alternatively, the interpolation function GN (X) may be a function other than a polynomial such as a sine function.

  In the above-described embodiment, the printed landing deviation detection pattern Q is read by the scanner 61 different from the ink jet printer 1 in the manufacturing stage of the ink jet printer 1 or the like, so that the intersections at the peak portion Pt and the valley bottom portion Pb are obtained. Although the amount of deviation was acquired, it is not limited to this. In one modification, as illustrated in FIG. 10, the control device 50 is further provided with a deviation amount acquisition unit 58. Then, the landing deviation detection pattern Q is read by the reading unit 5 (landing position deviation amount acquisition device), and the deviation amount acquisition unit 58 determines the intersection deviation in the mountain peak portion Pt and the valley bottom portion Pb from the read landing deviation detection pattern Q. Get the quantity. Then, the acquired intersection deviation amount is stored in the deviation amount storage unit 53.

  In this case, the inkjet printer 1 needs to include the reading unit 5 in order to read the landing deviation detection pattern Q. In the above embodiment, the scanner 61 is different from the inkjet printer 1. In order to read the landing deviation detection pattern Q, the ink jet printer 1 may not be provided with the reading unit 5 and only capable of printing.

  Further, in the above-described embodiment, while moving the carriage 11 in one direction of the scanning direction, the ink is ejected from the nozzle 10 to print the straight line L1, and while moving the carriage 11 in the other direction of the scanning direction, Although the straight line L2 is printed by ejecting ink from the nozzle 10 and thereby the landing deviation detection pattern Q in which the straight line L1 and the straight line L2 overlap is printed, this is not restrictive.

  For example, ink is ejected from the nozzle 10 on the recording paper P on which straight lines similar to the plurality of straight lines L1 are printed in advance while moving the carriage 11 in one direction or the other direction of the scanning direction, thereby By printing the straight line L2, a landing deviation detection pattern in which the preprinted straight line and the printed straight line L2 overlap may be printed. Even in this case, by reading the landing deviation detection pattern, it is possible to acquire the landing position deviation amount with respect to the predetermined reference position in the peak portion Pt and the valley bottom portion Pb.

  Further, the landing deviation detection pattern is not limited to being formed by two intersecting straight lines, and may be another landing deviation detection pattern whose printing result changes according to the landing position deviation amount.

  Further, in the above-described embodiment, by calculating all the interpolation functions GN (X) for each section S, the intersection shift amount is calculated over the entire scanning direction of the waveform area of the recording paper P. This is not a limitation. For example, the corrugated recording paper P is greatly curved at some peak portions Pm and valley portions Pv, and is not so curved at other peak portions Pm and valley portions Pv. In this case, the interpolation function GN (X) is calculated only for the section S corresponding to the peak portion Pm and the valley portion Pv having a large curvature, and then the calculation of the misalignment amount and the determination of the ink discharge timing are performed. Good.

  In the section S where the interpolation function GN (X) has not been calculated, since the curvature of the peak portion Pm and the valley portion Pv is small, it is assumed that the landing position deviation does not significantly affect the image quality. Ink is ejected at the same timing as when the wave shape is not used.

  Further, in the above-described embodiment, by printing the landing deviation detection pattern Q and reading the printed landing deviation detection pattern Q, as information related to the gap between the ink ejection surface 12a and each part of the recording paper P, Although the intersection shift amount in the mountain top portion Pt and the valley bottom portion Pb is acquired, it is not limited thereto. In other words, other information related to the gap between the ink discharge surface 12a and the peak portion Pt and the valley bottom portion Pb other than the intersection shift amount may be acquired. Furthermore, information on the gap itself may be acquired by directly measuring a gap between the ink ejection surface 12a and each peak portion Pt and valley bottom portion Pb.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 5 Reading part 11 Carriage 12 Inkjet head 15 Corrugated plate 16 Rib 18, 19 Corrugated spur 53 Shift amount memory | storage part 54 Interpolation function determination part 55 Head position detection part 56 Deviation amount calculation part 57 Discharge timing determination part 58 Acquisition of shift amount Part 61 Scanner 62 PC

Claims (2)

An inkjet head having an ink ejection surface on which nozzles for ejecting ink are formed; a carriage that mounts the inkjet head; and that reciprocates in a scanning direction parallel to the ink ejection surface with the inkjet head facing a recording medium;
An encoder sensor mounted on the carriage for detecting a slit formed in an encoder belt extending in the scanning direction;
A wave shape that generates a predetermined wave shape in which a peak portion protruding toward the ink discharge surface and a valley portion recessed on the opposite side of the ink discharge surface are arranged along the scanning direction on the recording medium. Generation mechanism;
A control unit,
The controller is
The position of the inkjet head that is reciprocated in the scanning direction by the carriage is detected from the detection result of the encoder sensor,
Furthermore, the control unit
Wherein the plurality of gap information related to the gap between the crest portion and the trough portion of the root portion contains and the parallel department minutes plurality of the inspection unit in the scanning direction the ink discharge surface of the front Kiyama portion of the recording medium Holding an average value and a deviation from the average value for each of the plurality of gap information ,
Using the deviation, for an interval located between the plurality of inspection portions in the scanning direction, calculate an interpolation function for calculating the gap information corresponding to the interval,
The interpolation function is a function having the position of the inkjet head in the scanning direction as a variable,
Furthermore, the control unit
When ejecting ink from the inkjet head to the recording medium,
From the information on the current position of the inkjet head detected from the detection result of the encoder sensor, gap information corresponding to the current position is sequentially calculated using the interpolation function, and the calculated current position is supported. An ink jet head printer, wherein ink ejection timing is determined based on gap information, and ink is ejected from the ink jet head to the recording medium at the determined ejection timing . The controller is
When calculating the interpolation function,
Among the gap information in the plurality of inspection portions, the difference between the gap information corresponding to the peak portion and the average value is a maximum value, and the difference between the gap information corresponding to the valley bottom portion and the average value is a minimum value. for the interval between the peaks portion and the trough bottom, as represented by a cubic curve as having the minimum value and the maximum value, to claim 1, characterized in that to calculate the interpolation function The inkjet printer as described.

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