Method for adjusting the droplet ejection head in a printing system and printing system

Abstract

Even if the line head frame and the droplet dispensing head do not have means for detecting the position of the droplet dispensing head when attaching the droplet dispensing head to the line head, the position of the droplet dispensing head can be appropriately adjusted. [Solution] The adjustment method includes forming an adjustment target pattern on a single medium using an adjustment target head; forming a reference pattern identical to the adjustment target pattern on the single medium using a reference head adjacent to the adjustment target head; determining a first distance, which is the distance in a first direction between the adjustment target pattern and the reference pattern formed on the medium, and a second distance, which is the distance in a second direction perpendicular to the first direction; operating an actuator to move the adjustment target head along the first direction within the first distance; and adjusting the discharge timing from the adjustment target head according to the second distance.

Description

Technical Field

[0001] The present invention relates to a method for adjusting a droplet ejection head in a printing system and a printing system.

Background Art

[0002] Conventionally, a line head capable of adjusting the position of a head module after replacement has been known (Patent Document 1). Specifically, when replacing the head module, the position of the head module after replacement is adjusted with the position of the head module before replacement in the line head as the target position. To store the position of the head module before replacement, which is the target position, the module base frame on which the head module is mounted has a magnetic sensor. On the other hand, the head modules before and after replacement each have a magnet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described conventional line head, the magnetic sensor and the magnet are members that are only required when replacing the head module, and are not used for, for example, ink ejection by the head module after replacing the head module. Moreover, the time required for replacing the head module is overwhelmingly shorter than the time from when the head module is replaced until it is replaced next. Therefore, from the viewpoint of manufacturing cost, it is desirable that the module pace frame and the head module of the line head do not have a magnetic sensor or a magnet.

[0005] The present invention was made to solve the above-mentioned problems, and aims to provide a method for adjusting a droplet ejection head in a printing system and a printing system that allows for appropriate adjustment of the position of the droplet ejection head even if the line head frame and the droplet ejection head do not have means for detecting the position of the droplet ejection head when attaching the droplet ejection head to the line head.

[0006] According to an aspect of the present invention, a method for adjusting droplet ejection heads, performed by a controller in a printing system, is provided. The printing system comprises a line head including a plurality of droplet ejection heads arranged along a first direction, and actuators for adjusting the positions of the plurality of droplet ejection heads in the line head. The adjustment method includes: discharging a droplet onto a medium from one of the plurality of droplet discharging heads to form an adjustment target pattern on the medium; discharging a droplet onto the medium from a reference head adjacent to the adjustment target head from one of the plurality of droplet discharging heads to form a reference pattern identical to the adjustment target pattern on the medium; determining a first distance, which is the distance in the first direction between the adjustment target pattern and the reference pattern formed on the medium, and a second distance, which is the distance in the second direction that is orthogonal to the first direction and is the relative movement direction between the medium and the line head; operating the actuator to move the adjustment target head along the first direction within the first distance without moving the reference head, according to the first distance; and adjusting the discharge timing from the adjustment target head without changing the discharge timing from the reference head, according to the second distance.

[0007] According to another aspect of the present invention, a printing system is provided comprising a line head including a plurality of droplet dispensing heads arranged along a first direction, actuators for adjusting the positions of the plurality of droplet dispensing heads on the line head, and a controller electrically connected to the plurality of droplet dispensing heads and the actuators. The controller dispenses a droplet onto one medium from one of the plurality of droplet dispensing heads to form a pattern to be adjusted on the medium, and dispenses a droplet onto the medium from a reference head adjacent to the head to be adjusted on one of the plurality of droplet dispensing heads to form a reference pattern identical to the pattern to be adjusted on the medium. The controller determines a first distance, which is the distance in the first direction between the pattern to be adjusted and the reference pattern formed on the medium, and a second distance, which is the distance in the second direction that is orthogonal to the first direction and is the relative movement direction between the medium and the line head. The controller operates the actuator to move the head to be adjusted along the first direction within the first distance without moving the reference head, according to the first distance, and adjusts the dispensing timing from the head to be adjusted without changing the dispensing timing from the reference head, according to the second distance.

[0008] According to the above embodiment of the present invention, even if the line head frame and the droplet dispensing head do not have means for detecting the position of the droplet dispensing head when attaching the droplet dispensing head to the line head, the position of the droplet dispensing head can be appropriately adjusted. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the configuration of the printing system. [Figure 2] This diagram schematically shows the configuration of the printers that make up the printing system. [Figure 3] This is a plan view showing an example of a line head that makes up a printer. [Figure 4] This is a cross-sectional view of the flow path member and piezoelectric actuator that constitute the head. [Figure 5] This flowchart shows how to adjust the print head in a printing system. [Figure 6] This figure shows an example of a test pattern. [Figure 7] This figure shows an example of how to adjust the head. [Figure 8] This figure shows an example of how to adjust the head. [Modes for carrying out the invention]

[0010] As shown in Figure 1, the printing system 1000 according to an embodiment of the present invention comprises a printer 100, a PC 200, and a scanner 300. The printer 100 is a digital printing machine.

[0011] The PC200, as an example, comprises a CPU 210, memory 220 such as RAM, a storage unit 230 such as a hard disk drive, an input unit 240 such as a keyboard, a display unit 250 such as a display, and an input / output interface 260 such as USB. The processor 210 temporarily reads data and programs stored in the storage unit 230 into the memory 220 and executes various processes described later according to the read data and programs. The printer 100 and scanner 300 are electrically connected to the PC200 via the input / output interface 260.

[0012] Next, the configuration of the printer 100 will be described in detail. As shown in Figure 2, the printer 100 mainly consists of line heads 10A to 10H, a transport device 20, and head controllers 6A to 6H.

[0013] The line heads 10A to 10H are arranged in this order from the upstream side in the transport direction. The transport direction is the direction in which the medium M, such as roll paper, is transported by the transport device 20. Each of the line heads 10A to 10H is long in the width direction. The width direction is along the width of the medium M and is perpendicular to the vertical direction and the transport direction. Each of the line heads 10A to 10H ejects ink onto the medium M while fixed in position on the housing (not shown) of the printer 100. The width direction is an example of the first direction of the present invention, and the transport direction is an example of the second direction of the present invention.

[0014] Line heads 10C to 10H on the downstream side in the conveying direction are supplied with, for example, yellow, orange, magenta, violet, cyan, and black inks, respectively. Line heads 10A and 10B on the upstream side in the conveying direction are supplied with, for example, white ink, respectively. As these inks, for example, UV-curable inks that harden when exposed to ultraviolet (UV) light can be used.

[0015] As shown in Figure 3, each of the line heads 10A to 10H has a frame FR, and at the vertically lower end of that frame, there are, for example, 10 droplet dispensing heads 1 (hereinafter simply referred to as "head 1"). The 10 heads 1 are arranged in a staggered pattern in the width direction, with their lower surfaces lying on the same plane. As shown in Figure 3, the lower surface of each head 1 is a nozzle surface NS from which multiple nozzles N open. On the nozzle surface NS, the multiple nozzles N are arranged in a staggered pattern in the width direction, forming two rows of nozzles aligned in the transport direction. Each row of nozzles extends in the width direction. In this embodiment, each head 1 has two rows of nozzles, but there may be one row of nozzles, or three or more rows. In addition, each head 1 is provided with an actuator 5, such as an eccentric pin. The actuator 5 is configured to be displaced by the drive of a motor fixed to each of the frames FR of the line heads 10A to 10H, for example. Each head 1 is electrically connected to a driver IC 4 (see Figure 4) that supplies a drive voltage to that head 1.

[0016] The conveying device 20 comprises a feed roller 20A and a recovery roller 20B as shown in Figure 2, and a plurality of conveying rollers (not shown). Furthermore, the conveying device 20 comprises a conveying motor (not shown) connected to the feed roller 20A and the recovery roller 20B. The feed roller 20A and the recovery roller 20B are aligned in the conveying direction, with the feed roller 20A located upstream of the recovery roller 20B in the conveying direction. In the conveying direction, line heads 10A to 10H are located between the feed roller 20A and the recovery roller 20B. The plurality of conveying rollers are located between the feed roller 20A and the recovery roller 20B in the conveying direction and are aligned in the conveying direction. The plurality of conveying rollers are located below the line heads 10A to 10H.

[0017] The feed roller 20A, the recovery roller 20B, and the multiple transport rollers all extend in the width direction and rotate around a rotation axis that extends in the width direction. The feed roller 20A and the recovery roller 20B are each driven to rotate by a transport motor. A roll-shaped medium M, whose length in the transport direction is longer than its length in the width direction, is attached to the feed roller 20A. The medium M, which is fed out from the feed roller 20A by the rotation of the feed roller 20A, passes between the line heads 10A to 10H and the multiple transport rollers, and is wound onto the recovery roller 20B by the rotation of the recovery roller 20B. In this way, the medium M is transported in the transport direction. The multiple transport rollers rotate in conjunction with the transport of the medium M. The transport motor drives the feed roller 20A and the recovery roller 20B to rotate so that the medium M is transported while in contact with the upper part of the circumferential surface of each of the multiple transport rollers.

[0018] The head controllers 6A to 6H are each electrically connected to the line heads 10A to 10H. For example, the head controller 6A is electrically connected to the ten driver ICs 4 included in the line head 10A. Further, the head controller 6A is also electrically connected to the ten motors fixed to the frame FR of the line head 10A. The head controllers 6A to 6H all include a CPU 61, a ROM 62, and a RAM 63. When the CPU 61 receives various instructions from the PC 200 shown in FIG. 1, it temporarily reads out the data and programs stored in the ROM 62 into the RAM 63, and executes processing according to the various instructions in accordance with the read data and programs. Then, the head controllers 6A to 6H are each electrically connected to the PC 200. The CPU 210 of the PC 200 and / or the CPU 61 of each of the head controllers 6A to 6H functions as an example of the controller of the present invention.

[0019] Next, the configuration of each head 1 will be described. As shown in FIG. 4, the head 1 includes a flow path member 2 and a piezoelectric actuator 3.

[0020] The flow path member 2 is formed by a plurality of metal plates and a nozzle plate NP laminated in the vertical direction. Ink flow paths such as individual flow paths 2B including the pressure chamber P and a supply manifold 2A are formed in the plurality of metal plates by etching. The nozzle plate NP is formed of a polymer synthetic resin material such as polyimide, for example, and is joined to the lower surface of the laminated metal plates with an adhesive. The lower surface of the nozzle plate NP is a nozzle surface NS as an ink ejection surface where the nozzles N open. Note that the nozzle plate NP may be formed of a metal material such as stainless steel.

[0021] Inside the flow path member 2, an individual flow path 2B communicating with each nozzle N and a supply manifold 2A communicating with the individual flow path 2B are formed. Although not shown, the supply manifold 2A extends in the width direction (the direction perpendicular to the paper surface in FIG. 4). The supply manifold 2A is connected to a tank (not shown) located outside the head 1 via an ink supply port (not shown) formed in the flow path member 2. The ink discharged from the tank flows into the supply manifold 2A via the ink supply port and is supplied from the supply manifold 2A to the individual flow path 2B.

[0022] Also, although not shown, the flow path member 2 is formed with a plurality of individual flow paths 2B respectively corresponding to the plurality of nozzles N. And corresponding to the formation of the plurality of nozzles N into two rows of nozzle rows respectively extending in the width direction as described above, the plurality of individual flow paths 2B form two rows of individual flow path rows respectively extending in the width direction. And the supply manifold 2A communicates with the plurality of individual flow paths 2B constituting the two rows of individual flow path rows. Note that the number of supply manifolds 2A formed in the flow path member 2 is adjusted according to the number of nozzles N. Also, when a plurality of supply manifolds 2A are formed, the number of individual flow paths 2B communicating with each supply manifold 2A is also adjusted according to the number of nozzles N.

[0023] As shown in FIG. 4, the piezoelectric actuator 3 is fixed to the upper surface of the flow path member 2. The piezoelectric actuator 3 includes a metal diaphragm 3A, a piezoelectric layer 3B, and a plurality of individual electrodes 3C.

[0024] The piezoelectric actuator 3 is formed by sequentially forming a thin film serving as the piezoelectric layer 3B and a thin film serving as the individual electrode 3C on the upper surface of the diaphragm 3A.

[0025] The diaphragm 3A is positioned on the upper surface of the flow channel member 2 so as to cover all of the pressure chambers P. The diaphragm 3A is a metal plate that is approximately rectangular in shape when viewed from above. The upper surface of the conductive diaphragm 3A is located below the piezoelectric layer 3B. Therefore, the upper surface of the diaphragm 3A can also serve as a common electrode. As a common electrode, the diaphragm 3A is connected to the ground wiring of the driver IC 4 that drives the actuator member 3 and is always maintained at ground potential. Note that the diaphragm 3A does not necessarily have to be a metal plate; for example, it may be formed from the same piezoelectric material as the piezoelectric layer 3B, with a metal film formed on its upper surface to serve as a common electrode.

[0026] The piezoelectric layer 3B is located on the upper surface of the diaphragm 3A. The piezoelectric layer 3B is formed from a piezoelectric material whose main component is lead zirconate titanate (PZT), a ferroelectric solid solution of lead titanate and lead zirconate. The piezoelectric layer 3B is polarized vertically at least in the region facing the pressure chamber P (the portion sandwiched between the individual electrodes 3C and the diaphragm 3A).

[0027] The individual electrodes 3C are arranged on the upper surface of the piezoelectric layer 3B so as to overlap the pressure chamber P vertically. The diaphragm 3A, which acts as a common electrode, the individual electrodes 3C, and the portion of the piezoelectric layer 3B sandwiched between the individual electrodes 3C and the diaphragm 3A form a single piezoelectric element 3X.

[0028] When a predetermined drive voltage is applied to an individual electrode 3C from the driver IC 4, a potential difference is created between the individual electrode 3C to which this drive voltage is applied and the diaphragm 3A, which is a common electrode held at ground potential. As a result, an electric field acts in the thickness direction on the piezoelectric layer 3B sandwiched between the individual electrode 3C and the diaphragm 3A. The direction of this electric field is parallel to the polarization direction of the piezoelectric layer 3B. Therefore, the region of the piezoelectric layer 3B facing the individual electrode 3C (active region) contracts in a planar direction perpendicular to the thickness direction. Here, the diaphragm 3A below the piezoelectric layer 3B is fixed to the flow channel member 2. Therefore, as the piezoelectric layer 3B located on the upper surface of the diaphragm 3A contracts in the planar direction, the portion of the diaphragm 3A covering the pressure chamber P deforms so that it becomes convex toward the pressure chamber P (unimorph deformation). At this time, the volume inside the pressure chamber P decreases, the ink pressure inside the pressure chamber P increases, and ink is ejected from the nozzle N that communicates with this pressure chamber P. In other words, the piezoelectric actuator 3 is located in a position corresponding to the pressure chamber P and applies pressure to the ink in the pressure chamber P in order to eject ink from the nozzle N.

[0029] Next, the adjustment method for the head 1 in the printing system 1000 of this embodiment will be described with reference to Figures 5 to 8. This adjustment method is performed, for example, when a user replaces any of the heads 1 in any of the line heads 10A to 10H, in order to adjust the widthwise position, ejection timing, and drive voltage of the replaced head 1.

[0030] The flow shown in Figure 5 is initiated when the user specifies the replaced head 1 as the head to be adjusted and inputs a test pattern print command via the input unit 240 of the PC200. The following explanation will use the case where head 1 included in line head 10H is replaced as an example, but the flow is the same when head 1 included in the other line heads 10A to 10G is replaced.

[0031] When the CPU 210 of the PC200 receives a test pattern print instruction via the input unit 240, it sends the instruction to the head controller 6H. Upon receiving the test pattern print instruction, the head controller 6H drives all 10 heads 1 included in the line head 10H to eject ink droplets, thereby printing 10 identical test patterns TP arranged in the width direction onto the medium M being transported in the transport direction (step S10).

[0032] Here, each test pattern TP consists of a first pattern P1, a second pattern P2, and a third pattern P3, as shown in Figure 6. The first pattern P1 consists of multiple lines (hereinafter referred to as vertical lines) that extend in the transport direction. Each vertical line is formed by continuously ejecting ink droplets from a single nozzle N. In the first pattern P1, the multiple vertical lines are arranged in the width direction, for example, at equal intervals. The second pattern P2 consists of multiple lines (hereinafter referred to as horizontal lines) that extend in the width direction. Each horizontal line is formed by ejecting ink droplets only once from all nozzles N. In the second pattern P2, the multiple horizontal lines are arranged in the transport direction, for example, at equal intervals. The third pattern P3 consists of two solid color patterns of different densities. The third pattern P3 is formed by continuously ejecting ink droplets from all nozzles N.

[0033] Next, when the user inputs a command to read the test pattern TP printed on the medium M via the input unit 240 of the PC200, the CPU 210 of the PC200 causes the scanner 300 to read the 10 test pattern TP printed on the medium M (step S20).

[0034] Next, the CPU 210 of PC200 acquires and analyzes the image data of the 10 test patterns TP read by the scanner 300 (step S30).

[0035] Specifically, the CPU 210 of the PC200 identifies, from among the 10 test patterns TP, the test pattern TP printed by head 1 designated as the head to be adjusted (hereinafter referred to as the adjusted test pattern TP) and the test pattern TP printed by head 1 adjacent to the adjusted head (hereinafter referred to as the reference head 1) (hereinafter referred to as the reference test pattern TP). The CPU 210 of the PC200 then determines the distance in the width direction and the distance in the transport direction between the adjusted test pattern TP and the reference test pattern TP. The distance in the width direction between the adjusted test pattern TP and the reference test pattern TP is determined based on the distance between the first patterns P1 contained in each. As an example, as shown in Figure 7, the distance in the width direction between the adjusted test pattern TP1 and the reference test pattern TP2 is determined based on the distance in the width direction between the vertical line closest to the reference test pattern TP2 (the rightmost) in the adjusted test pattern TP1 and the vertical line closest to the adjusted test pattern TP1 (the leftmost) in the reference test pattern TP2. The distance in the transport direction between the test pattern TP to be adjusted and the reference test pattern TP is determined based on the distance between the second patterns P2 contained within each. As an example, as shown in Figure 7, the distance in the transport direction between the test pattern TP1 to be adjusted and the reference test pattern TP2 is determined based on the distance in the transport direction between the horizontal line located at the uppermost position in the transport direction of the test pattern TP1 and the horizontal line located at the uppermost position in the transport direction of the reference test pattern TP2.

[0036] Furthermore, the CPU210 of PC200 determines the concentration difference between the test pattern TP to be adjusted and the reference test pattern TP. The concentration difference between the test pattern TP to be adjusted and the reference test pattern TP is determined based on the concentration of the third pattern P3 contained in each.

[0037] For example, if head 1 located at the far left in Figure 3 is designated as the head to be adjusted, then the single head 1 located second from the left in Figure 3 becomes the reference head 1. Also, for example, if head 1 located second from the left in Figure 3 is designated as the head to be adjusted, then the two heads 1 located at the far left and third from the left in Figure 3 become the reference head 1.

[0038] Then, the CPU 210 of PC200 displays the analysis results from step S30 on the display unit 250 of PC200 (step S40).

[0039] The user checks the analysis results displayed on the PC200's display unit 250 and inputs whether adjustment is necessary for the widthwise position, transport direction position, and concentration of the test pattern TP to be adjusted, via the PC200's input unit 240.

[0040] If the CPU 210 of PC200 receives input indicating that adjustment of the widthwise position is necessary (step S50: YES), the CPU 210 of PC200 performs a widthwise position adjustment on the head to be adjusted (step S55). Specifically, the CPU 210 of PC200 sends a position adjustment instruction to the head controller 6H. Upon receiving the position adjustment instruction, the head controller 6H drives the motor corresponding to the head to be adjusted to activate the actuator 5 on the head to be adjusted so that the head moves in the widthwise direction within the widthwise distance determined in step S30. When step S55 is completed, the CPU 210 of PC200 proceeds to step S60. On the other hand, if the CPU 210 of PC200 receives input indicating that adjustment of the widthwise position is not necessary (step S50: NO), the CPU 210 of PC200 proceeds to step S60.

[0041] If the CPU 210 of PC200 receives input indicating that adjustment of the transport direction position is necessary (step S60: YES), the CPU 210 of PC200 adjusts the discharge timing of the head to be adjusted (step S65). Specifically, the CPU 210 of PC200 sends an instruction to the head controller 6H to adjust the discharge timing of the head to be adjusted. Upon receiving the instruction to adjust the discharge timing of the head to be adjusted, the head controller 6H adjusts the discharge timing of the head to be adjusted according to the transport direction distance determined in step S30. When step S65 is completed, the CPU 210 of PC200 proceeds to step S70. On the other hand, if the CPU 210 of PC200 receives input indicating that adjustment of the transport direction position is not necessary (step S60: NO), the CPU 210 of PC200 proceeds to step S70.

[0042] If the CPU 210 of PC200 receives input indicating that density adjustment is necessary (step S70: YES), the CPU 210 of PC200 adjusts the drive voltage for the head to be adjusted (step S75). Specifically, the CPU 210 of PC200 sends a density adjustment instruction for the head to be adjusted to the head controller 6H. Upon receiving the density adjustment instruction for the head to be adjusted, the head controller 6H adjusts the drive voltage for the head to be adjusted according to the density difference determined in step S30. When step S75 is completed, the CPU 210 of PC200 proceeds to step S80. On the other hand, if the CPU 210 of PC200 receives input indicating that density adjustment is not necessary (step S70: NO), the CPU 210 of PC200 proceeds to step S80.

[0043] In step S80, the CPU 210 of PC200 sends a test pattern print instruction to the head controller 6H. Upon receiving the test pattern print instruction, the head controller 6H drives all 10 heads 1 included in the line head 10H to eject ink droplets, thereby printing 10 identical test patterns TP arranged in the width direction onto the medium M being transported in the transport direction. If the result in steps S50, S60, and S70 is NO, then no adjustments are needed for the head to be adjusted, and steps S80 and the subsequent step S90 are not performed, and the flow is terminated.

[0044] Then, in step S80, the user visually checks the reprinted test pattern and inputs whether sufficient image quality was obtained via the input unit 240 of the PC200. If the CPU 210 of the PC200 receives input that sufficient image quality was not obtained (S90: NO), the CPU 210 of the PC200 returns to step S20. On the other hand, if the CPU 210 of the PC200 receives input that sufficient image quality was obtained (S90: YES), the CPU 210 of the PC200 terminates the flow.

[0045] Next, we will specifically explain the widthwise position adjustment in step S55, the discharge timing adjustment in step S65, and the drive voltage adjustment in step S75.

[0046] First, if one of the ten heads 1 included in the line head 10H is designated as the head to be adjusted, then, as described above, only the one head 1 adjacent to the head to be adjusted becomes the reference head 1.

[0047] Then, as a result of step S30, we assume that the distance in the width direction between the test pattern TP1 to be adjusted and the reference test pattern TP2 is d1 and the distance in the transport direction is d2, as shown in Figure 7. In this case, in step S55, the head controller 6H drives the motor corresponding to the head to be adjusted to activate the actuator 5 of the head to be adjusted so that the head to be adjusted moves by a distance d1 in the width direction. To explain using the specific example in Figure 7, the vertical lines of the test pattern TP1 to be adjusted are shifted to the left by a distance d1 relative to the vertical lines of the reference test pattern TP2. That is, the head to be adjusted is shifted to the left by a distance d1 relative to the reference head 1. Therefore, the head controller 6H drives the motor to activate the actuator 5 so that the head to be adjusted moves to the right by a distance d1. Also, in step S65, the head controller 6H adjusts the discharge timing of the head to be adjusted so that the position of the test pattern TP1 in the transport direction is the same as the position of the reference test pattern TP2 in the transport direction. As illustrated in the specific example in Figure 7, the horizontal lines of the test pattern TP1 to be adjusted are shifted upstream in the transport direction by a distance d2 relative to the horizontal lines of the reference test pattern TP2. In other words, the ejection timing of the head to be adjusted is earlier than that of the reference head 1 by a time equivalent to a distance d2. Therefore, the head controller 6H delays the ejection timing of the head to be adjusted by a time equivalent to a distance d2. Furthermore, if a density difference is observed between the test pattern TP1 to be adjusted and the reference test pattern TP2 as a result of step S30, in step S75, the head controller 6H adjusts the drive voltage of the head to be adjusted so that the density of the test pattern TP1 becomes equal to the density of the reference test pattern TP2. At this time, the head controller 6H adjusts the drive voltage of the head to be adjusted by referring to a mapping table of voltage values ​​and density values ​​that is pre-stored in, for example, ROM 62. Note that when printing the test pattern in step S10 after replacing the head to be adjusted, the drive voltage of the head to be adjusted is set to the same voltage value as the drive voltage of the reference head 1.

[0048] Next, we will explain the case where one of the ten heads 1 included in the line head 10H, located outside the widthwise end, is designated as the head to be adjusted. In this case, as described above, the two heads 1 located on either side of the head to be adjusted become the reference heads 1.

[0049] If there are two reference heads 1, in step S30, the distance in the width direction, the distance in the transport direction, and the density difference between the two reference test patterns TP printed by the two reference heads 1 are determined. For example, let's assume that the distance in the width direction between the two reference test patterns TP2 and TP3 is d, as shown in Figure 8. In this case, it is desirable that the reference test pattern TP2, the test pattern to be adjusted TP1, and the reference test pattern TP be printed at equal intervals in the width direction. Therefore, in step S55, the head controller 6H determines the target position of the head to be adjusted. Specifically, it determines a target position where the distance from one reference head 1 to the target position is equal to the distance from the other reference head 1 to the target position. The head controller 6H then drives the motor corresponding to the head to be adjusted to operate the actuator 5 of the head to be adjusted so that the head to be adjusted moves to the target position. This will be explained with a specific example in Figure 8. In Figure 8, let X1 be the position in the width direction of a predetermined vertical line of the test pattern TP1 to be adjusted before adjustment, and let X be the position in the width direction after adjustment. Furthermore, the positions in the width direction of the predetermined vertical lines of the reference test patterns TP2 and TP3 are denoted as X2 and X3. Before adjustment, the distance from position X2 to position X1 is longer than the distance from position X3 to position X1. In other words, before adjustment, the head to be adjusted is shifted to the right by |X1-X| relative to the target position where the distance from the two reference heads 1 is equal. Therefore, the head controller 6H drives the motor corresponding to the head to be adjusted to move the head to be adjusted to the left by |X1-X|, thereby activating the actuator 5 of the head to be adjusted.

[0050] Furthermore, in step S65, the head controller 6H determines the target discharge timing of the head to be adjusted in order to equalize the distance in the transport direction from the reference test pattern TP2 to the test pattern TP1 to be adjusted with the distance in the transport direction from the reference test pattern TP3 to the test pattern TP1 to be adjusted. This will be explained with a specific example in Figure 8. In Figure 8, let Y1 be the position in the transport direction of a predetermined horizontal line of the test pattern TP1 to be adjusted before adjustment, and Y be the position in the transport direction after adjustment. Also, let Y2 and Y3 be the positions in the transport direction of the predetermined horizontal lines of the reference test patterns TP2 and TP3, respectively. Before adjustment, the distance from position Y2 to position Y1 is shorter than the distance from position Y3 to position Y1. In other words, position Y1 is shifted upstream in the transport direction by a distance of |Y-Y1| from position Y, where the distance from the horizontal lines of the reference test patterns TP2 and TP3 is equal. That is, the discharge timing of the head to be adjusted is earlier than the ideal discharge timing by a time corresponding to the distance of |Y-Y1|. Therefore, the head controller 6H delays the ejection timing of the head to be adjusted by a time equivalent to the distance |Y-Y1|.

[0051] Furthermore, in step S75, the head controller 6H determines the target drive voltage value of the head to be adjusted in order to equalize the density difference between the reference test pattern TP2 and the test pattern TP1 to be adjusted, and the density difference between the test pattern TP1 to be adjusted and the reference test pattern TP3. Specifically, the head controller 6H determines the target drive voltage value of the head to be adjusted by referring to a mapping table of voltage values ​​and density values ​​pre-stored in, for example, the ROM 62, so that the density of the test pattern TP1 to be adjusted becomes the average density of the density of the reference test pattern TP2 and the density of the reference test pattern TP3. For example, if the density of the reference test pattern TP2 is 62 and the density of the reference test pattern TP3 is 65, the head controller 6H determines the target drive voltage value of the head to be adjusted so that the density of the test pattern to be adjusted becomes 63.5, which is the average value of 62 and 65. Then, the head controller 6H adjusts the drive voltage of the head to be adjusted to the target drive voltage value. Furthermore, when printing a test pattern in step S10 after replacing the head to be adjusted, the drive voltage of the head to be adjusted is set to the average value of the drive voltages of the two reference heads 1.

[0052] Even if n (n≧2) consecutive heads 1 located outside the widthwise ends of the 10 heads 1 included in the line head 10H are designated as heads to be adjusted, the same adjustment can be performed as when there is only one head to be adjusted.

[0053] In other words, in step S55, the head controller 6H determines n target positions that divide the widthwise distance from one reference head 1 to the other reference head 1 into (n+1) equal parts. Then, the head controller 6H operates the n actuators 5 of each of the n heads to be adjusted so that each of the n heads to be adjusted moves to the n target positions.

[0054] Furthermore, in step S65, the head controller 6H determines the target discharge timings for the n heads to be adjusted so that the n test patterns to be adjusted are positioned at n target positions, each of which divides the transport distance from the reference test pattern TP2 to the reference test pattern TP3 into (n+1) equal parts. The head controller 6H then shifts the discharge timings of the n heads to be adjusted to the n target discharge timings.

[0055] Furthermore, in step S75, the head controller 6H determines the target drive voltage value for each of the n heads to be adjusted such that the density of each of the n test patterns to be adjusted is a value that divides the difference between the density of the reference test pattern TP2 and the density of the reference test pattern TP3 into (n+1) equal parts. In this case, the head controller 6H determines the target drive voltage value for each of the n heads to be adjusted by referring to a mapping table of voltage values ​​and density values ​​that is pre-stored in, for example, the ROM 62. For example, suppose there are two heads to be adjusted, and the density of the reference test pattern TP2 is 62 and the density of the reference test pattern TP3 is 65. In this case, the head controller 6H determines the target voltage values ​​for the two heads to be adjusted such that the densities of the two test patterns to be adjusted are 63 and 64 (two values ​​that divide the density difference between 65 and 62 into three equal parts). Then, the head controller 6H adjusts the drive voltage of each of the n heads to be adjusted to the n target drive voltage values. Furthermore, after replacing the heads with n adjustment targets, when printing a test pattern in step S10, the drive voltage of the n adjustment target heads is set to the average voltage value of the drive voltages of the two reference heads 1.

[0056] According to the embodiment described above, the widthwise position, discharge timing, and drive voltage of the head to be adjusted are adjusted based on the widthwise position, discharge timing, and drive voltage of the reference head 1 adjacent to the head to be adjusted. Therefore, even if the line head frame and the head to be adjusted do not have means for detecting the position of the head to be adjusted in the line head, the widthwise position, discharge timing, and drive voltage of the head to be adjusted can be appropriately adjusted.

[0057] Furthermore, if the head to be adjusted is located anywhere other than the edge in the width direction, the position in the width direction, the position in the transport direction, and the density of the test pattern to be adjusted can be adjusted so that they change in steps from one reference test pattern TP to the other reference test pattern TP. This allows for obtaining good image quality.

[0058] The embodiments described above are illustrative in all respects and not restrictive. Not all of the configurations shown in the embodiments are essential, and configurations can be modified or omitted as needed.

[0059] In the above embodiment, the scanner 300 was electrically connected to the PC 200 via the input / output interface 260, but this is not limited to this. For example, the printer 100 may have a CIS (contact image sensor). In this case, a PC for storing image data read by the CIS may be provided and electrically connected to the printer 100 and the PC 200.

[0060] In the above embodiment, in steps S10 and S80, all 10 heads included in the line head were driven to print 10 identical test patterns TP on the medium M, but this is not limited to this. For example, only the head to be adjusted and the reference head 1 may be driven to print only the test pattern to be adjusted TP and the reference test pattern TP on the medium M.

[0061] In the above embodiment, the number and arrangement of heads 1 included in each of the line heads 10A to 10H can be changed as appropriate. Furthermore, the number and arrangement of nozzles N included in each head 1 can also be changed as appropriate.

[0062] Furthermore, in the above embodiment, white, yellow, orange, magenta, violet, cyan, and black inks were ejected from the line heads 10A to 10H, but the invention is not limited to these, and inks of any appropriate color may be ejected.

[0063] In the above embodiment, roll paper was used as the medium M, but any medium of an appropriate material can be used as needed. For example, the medium M may be a roll of resin film or cloth. [Explanation of Symbols]

[0064] 1. Droplet dispensing head 2 Flow channel members 3. Piezoelectric actuator 4 Driver ICs 5 Actuators 6A~6H Head Controller 10A~10H Line Head 20 Conveying device 100 Printers 200 PC 300 Scanners 1000 Printing Systems

Claims

1. A method for adjusting a droplet ejection head, performed by a controller in a printing system, The aforementioned printing system, A line head including multiple droplet dispensing heads arranged along a first direction, The system includes an actuator for adjusting the position of the plurality of droplet dispensing heads in the line head, The adjustment method described above is: From one of the plurality of droplet dispensing heads, a droplet is dispensed onto a single medium to form a pattern to be adjusted on the medium. From one of the plurality of droplet dispensing heads, a reference head adjacent to the head to be adjusted is used to dispense droplets onto the single medium, thereby forming a reference pattern identical to the pattern to be adjusted on the medium. To determine a first distance, which is the distance in the first direction between the adjustment target pattern formed on the medium and the reference pattern, and a second distance, which is the distance in the second direction that is orthogonal to the first direction and is the relative movement direction between the medium and the line head, The actuator is operated to move the head to be adjusted along the first direction within the first distance without moving the reference head, according to the first distance. An adjustment method comprising adjusting the discharge timing from the head to be adjusted without changing the discharge timing from the reference head, according to the second distance.

2. In the line head, if the head to be adjusted is located at one end in the first direction, The aforementioned controller, The actuator is operated to move the head to be adjusted by a first distance along the first direction. The adjustment method according to claim 1, wherein the discharge timing of the head to be adjusted is adjusted by a time corresponding to the second distance so that the position of the pattern to be adjusted in the second direction is the same as the position of the reference pattern in the second direction.

3. In the line head, if the head to be adjusted is not located at either end or the other end in the first direction, the reference head includes a first reference head adjacent to the head to be adjusted on one end side in the first direction, and a second reference head adjacent to the head to be adjusted on the other end side in the first direction. The aforementioned controller, The liquid droplets are ejected from the head to be adjusted onto the medium to form the pattern to be adjusted on the medium. The first reference head discharges the droplets into the medium to form a first reference pattern identical to the pattern to be adjusted in the medium. The droplets are ejected from the second reference head onto the medium to form a second reference pattern identical to the pattern to be adjusted onto the medium. Determine the distance in the first direction and the distance in the second direction for the first reference pattern and the second reference pattern. Without moving the first reference head and the second reference head, the actuator is operated to move the head to be adjusted along the first direction by a distance smaller than the distance between the first reference pattern and the second reference pattern in the first direction. The adjustment method according to claim 1, wherein the discharge timing of the head to be adjusted is adjusted such that, in the second direction, the pattern to be adjusted is located between the first reference pattern and the second reference pattern.

4. The line head includes one of the heads to be adjusted, The aforementioned controller, A target position is determined for the head to be adjusted in the first direction, such that the distance from the first reference head to the target position in the first direction is equal to the distance from the second reference head to the target position in the first direction. The adjustment method according to claim 3, wherein the actuator is operated to move the head to be adjusted to the target position in the first direction.

5. The controller further, The target discharge timing for the head to be adjusted is determined such that the distance in the second direction between the first reference pattern and the pattern to be adjusted is equal to the distance in the second direction between the pattern to be adjusted and the second reference pattern. The adjustment method according to claim 4, wherein the discharge timing of the head to be adjusted is shifted to the target discharge timing.

6. The line head includes n (n≧2) of the adjustment target heads that are continuous along the first direction, The aforementioned controller, Determine n target positions for each of the n heads to be adjusted, such that the distance between the first reference head and the second reference head in the first direction is divided into (n+1) equal parts. The adjustment method according to claim 3, wherein the actuator is operated to move each of the n heads to be adjusted to the n target positions in the first direction.

7. The controller further, The n target discharge timings are determined for each of the n heads to be adjusted, such that each of the n patterns to be adjusted is located at n target positions that divide the distance between the first reference pattern and the second reference pattern in the second direction into (n+1) equal parts. The adjustment method according to claim 6, wherein the discharge timing of each of the n heads to be adjusted is shifted to the n target discharge timings.

8. The adjustment method according to claim 2, further comprising setting the drive voltage of the head to be adjusted to the same voltage value as the drive voltage of the reference head before forming the adjustment pattern on the medium.

9. The adjustment method according to claim 8, further comprising adjusting the drive voltage of the head to be adjusted without changing the drive voltage of the reference head, such that the density of the pattern to be adjusted becomes equal to the density of the reference pattern.

10. The adjustment method according to claim 4, further comprising setting the drive voltage of the head to be adjusted to the average voltage value of the drive voltage of the first reference head and the drive voltage of the second reference head before forming the adjustment pattern on the medium.

11. The adjustment method according to claim 10, further comprising adjusting the drive voltage of the head to be adjusted without changing the drive voltage of the first reference head and the drive voltage of the second reference head, such that the concentration of the pattern to be adjusted becomes the average value of the concentration of the first reference pattern and the concentration of the second reference pattern.

12. A printing system, A line head including multiple droplet dispensing heads arranged along a first direction, An actuator for adjusting the position of the plurality of droplet dispensing heads in the line head, The system comprises the plurality of droplet dispensing heads and a controller electrically connected to the actuator, The aforementioned controller, From one of the plurality of droplet dispensing heads, the head to be adjusted dispenses droplets onto a single medium to form the pattern to be adjusted on the medium. From one of the plurality of droplet dispensing heads, a reference head adjacent to the head to be adjusted is used to dispense droplets onto the single medium, thereby forming a reference pattern identical to the pattern to be adjusted on the medium. A first distance is determined, which is the distance in the first direction between the adjustment target pattern formed on the medium and the reference pattern, and a second distance is determined, which is the distance in the second direction that is orthogonal to the first direction and is the relative movement direction between the medium and the line head. In accordance with the first distance, the actuator is operated to move the head to be adjusted along the first direction within the first distance without moving the reference head. A printing system that adjusts the ejection timing from the head to be adjusted without changing the ejection timing from the reference head, according to the second distance.

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