JP2016159435A - Liquid discharge device and liquid discharge method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge device and a liquid discharge method capable of suppressing a deviation of the impact position of liquid due to the air stream occurring between a liquid discharge part and a discharge object in a process of relative movement of them.SOLUTION: A printer comprises a carriage provided with a discharge head and a controller controlling the discharge timing of the discharge head. The controller distinguishes the acceleration process, the constant speed process and the deceleration process from each other in the process in which the discharge head moves together with the carriage (S14, S17), controls discharging at the discharge timings on the basis of mutually-different delay values Dpa, Dpc, Dpb (S15, S16, S18, S19, S20, S21), and delays the discharge timing of the acceleration process with respect to the discharge timing of the deceleration process if the speeds of the acceleration process and the deceleration process are the same.SELECTED DRAWING: Figure 18

Description

  The present invention relates to a liquid discharge apparatus and a liquid discharge method for discharging liquid from a discharge head and landing on a discharge target such as paper.

  2. Description of the Related Art Conventionally, serial type printing apparatuses in which a carriage having a recording head is provided so as to be capable of reciprocating in the scanning direction are widely known (for example, Patent Documents 1 to 4). In the serial type printing apparatus, a printing operation for recording (printing) on a medium such as paper by a recording head while moving (scanning) the carriage in the scanning direction, and the next printing position in the conveyance direction intersecting the scanning direction. Printing is performed on the paper while repeating the carrying operation to carry it substantially alternately. For example, Patent Documents 1 to 4 disclose techniques for correcting the liquid discharge timing of the discharge head in order to land the liquid discharged from the nozzle of the discharge head at an appropriate position on the medium.

  For example, Patent Document 1 discloses a technique for correcting the ejection timing according to the thickness of the print medium, the ink ejection speed, and the relative movement speed between the ejection head and the print medium. Patent Document 2 discloses a technique for correcting the ejection timing in accordance with the liquid ejection speed estimated from the difference in the positions of dots formed by ejecting liquid under different movement speeds of the ejection head. ing. Patent Document 3 discloses a technique for correcting the discharge timing based on the flying speed (discharge speed) of the liquid obtained from the stored data in accordance with the distance between the discharge head and the medium. Further, Patent Document 4 discloses a technique for performing control to vary the ejection timing in accordance with the size of dots formed by ejecting liquid onto a medium.

JP 2000-198189 A JP 2006-192575 A JP 2010-142978 A JP 2010-142979 A

  By the way, air current is generated around the carriage during scanning during printing. When the ink droplets ejected from the ejection head are caused to flow by the air flow, the landing position of the ink droplet is shifted from the assumed target position. As a result, there is a problem that the print image quality deteriorates due to the positional deviation of the print dots. In particular, in the acceleration / deceleration process of the carriage, an air flow is more easily generated than in the constant speed process, and the landing position of the ink droplet is shifted from the target position due to the air flow at that time. In particular, if the ink droplet size is reduced and the weight is reduced in order to increase the printing resolution, it is more susceptible to airflow, and in high-resolution printing, a slight shift affects the print image quality. It cannot be ignored. Note that this type of problem is generally common in a recording method in which the ejection head moves during printing, such as a lateral printing device, as well as a serial printing device. Further, in the line printer, ink droplets are ejected from the ejection head during the conveyance of a medium such as paper that is conveyed at a considerably high speed as compared with a serial printing apparatus. Therefore, when a medium transported at high speed or a moving body of a transport system that moves at a relatively high speed, such as a transport roller or a transport belt, becomes a source of airflow, and the generated airflow flows into the discharge area of the discharge head Since the ink droplets in flight are caused to flow and the landing position is displaced, the line printer has a similar problem.

  An object of the present invention is to provide a liquid ejecting apparatus and a liquid ejecting method capable of minimizing a deviation in the landing position of a liquid caused by an air flow generated in a relative movement process between a liquid ejecting unit and an ejected object. There is to do.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
A liquid ejection apparatus that solves the above-described problem is a liquid ejection apparatus that ejects liquid onto an ejection target, and controls a liquid ejection section that can eject liquid and ejection timing for ejecting liquid from the liquid ejection section A discharge timing when the relative speed at which the liquid discharge section and the discharge target object move relative to each other is the same in the acceleration process and the deceleration process. Is delayed from the discharge timing in the deceleration process.

  According to this configuration, if the relative speed is the same in the acceleration process and the deceleration process during the relative movement of the liquid ejection unit and the ejection target, the ejection timing in the acceleration process is delayed from the ejection timing in the deceleration process. That is, if the relative speeds are the same, the discharge timing in the deceleration process is made earlier than the discharge timing in the acceleration process. In the acceleration process and the deceleration process during the relative movement between the liquid discharge unit and the discharge target, an air flow (wind) is relatively easily generated compared to the constant speed process. Even if the liquid ejected in the acceleration process is caused to flow on the side opposite to the traveling direction of the liquid ejection part by the air flow generated in the acceleration process, the deviation of the landing position of the liquid with respect to the ejection target can be suppressed. Further, even if the liquid discharged in the deceleration process is caused to flow toward the traveling direction side of the liquid discharge part by the air flow generated in the deceleration process, the deviation of the landing position of the liquid with respect to the discharge target can be suppressed. Accordingly, it is possible to suppress a deviation in the landing position of the liquid due to the air flow generated in the relative movement process between the liquid discharge unit and the discharge target.

  In the liquid ejection device, the control unit is based on a relative speed at a constant speed between the liquid ejection unit and the ejection object and a gap between the liquid ejection unit and the ejection object in a constant speed process. The liquid discharge unit is controlled to be discharged at the first discharge timing, and the liquid discharge unit is controlled to be discharged at the second discharge timing delayed from the first discharge timing based on the relative speed and the gap during acceleration in the acceleration process. Is preferred.

  According to this configuration, in the acceleration process, the discharge of the liquid discharge unit is controlled at the second discharge timing delayed from the first discharge timing based on the relative speed and the gap at the time of acceleration. Therefore, even if the liquid ejected in the acceleration process flows on the opposite side to the traveling direction of the liquid ejecting portion, the deviation of the landing position of the liquid can be suppressed small.

  In the liquid ejection device, the control unit is based on a relative speed at a constant speed between the liquid ejection unit and the ejection object and a gap between the liquid ejection unit and the ejection object in a constant speed process. The liquid discharge unit is controlled to discharge at the first discharge timing, and the liquid discharge unit is controlled to discharge at the second discharge timing that is earlier than the first discharge timing based on the relative speed and the gap at the time of deceleration in the deceleration process. Is preferred.

  According to this configuration, in the deceleration process, the liquid discharge unit is controlled to discharge at the second discharge timing that is earlier than the first discharge timing based on the relative speed and the gap at the time of deceleration. Therefore, even if the liquid ejected in the deceleration process flows toward the traveling direction side of the liquid ejecting section, the deviation of the liquid landing position can be suppressed.

  In the liquid ejection apparatus, the control unit may set the second ejection timing to the first ejection timing when the gap is a second gap larger than the first gap in the acceleration process. It is preferable to delay more than.

  According to this configuration, in the acceleration process, the second discharge timing is delayed from the first discharge timing when the second gap is larger than the first gap than when the first gap is used. Therefore, even when the first gap is used even when the second gap in which the time during which the liquid discharged in the acceleration process is caused to flow on the side opposite to the traveling direction of the liquid discharge portion is relatively longer than when the first gap is used. Similarly, the deviation of the landing position of the liquid can be suppressed small.

  In the liquid ejection apparatus, it is preferable that the control unit increases the degree of delaying the second ejection timing relative to the first ejection timing as the gap is larger in the acceleration process.

  According to this configuration, in the acceleration process, the greater the gap, the greater the degree to which the second discharge timing is delayed from the first discharge timing. Therefore, even when the time during which the liquid ejected in the acceleration process flows in the direction opposite to the traveling direction of the liquid ejection unit becomes long when the gap is large, the deviation of the landing position of the liquid can be suppressed small.

  In the liquid ejection apparatus, the control unit may set the second ejection timing to the first ejection timing when the gap is a second gap larger than the first gap in the deceleration process. It is preferable to make it earlier.

  According to this configuration, in the deceleration process, the second discharge timing is earlier than the first discharge timing when the second gap is larger than the first gap than when it is the first gap. Therefore, even in the case of the second gap in which the time during which the liquid ejected in the deceleration process is caused to flow toward the traveling direction of the liquid ejection portion is relatively longer than in the first gap, similarly to the case of the first gap. The displacement of the liquid landing position can be kept small.

  In the liquid ejection apparatus, it is preferable that the controller increases the degree of advancement of the second ejection timing relative to the first ejection timing as the gap is larger in the deceleration process.

  According to this configuration, in the deceleration process, the greater the gap, the greater the degree to which the second discharge timing is advanced than the first discharge timing. Therefore, even when the time during which the liquid ejected in the deceleration process is caused to flow toward the traveling direction of the liquid ejection unit becomes long when the gap is large, the deviation of the landing position of the liquid can be suppressed small.

  In the liquid ejection apparatus, the degree to which the second ejection timing is delayed relative to the first ejection timing as the gap is larger in the acceleration process or the deceleration process is a quadratic function with the gap as a variable. It is preferably set.

  According to this configuration, the degree to which the discharge timing is delayed with respect to the first discharge timing as the gap increases in the acceleration process or the deceleration process is set by a quadratic function with the gap as a variable. Therefore, when the gap is large in the acceleration process and the deceleration process, even if the time during which the discharged liquid flows in the direction opposite to the traveling direction of the liquid ejecting portion or the traveling direction side becomes relatively long, the landing position of the liquid Can be kept small. Moreover, since it is a quadratic function, the calculation processing load when the control unit acquires the ejection timing can be reduced. Therefore, it is possible to cope with relatively high-speed discharge control.

  In the liquid ejection apparatus, it is preferable that the control unit controls the liquid ejection unit at the first ejection timing when the gap is less than a threshold value even in the acceleration process or the deceleration process.

  According to this configuration, even in the acceleration process or the deceleration process, when the gap is smaller than the threshold value, the liquid discharge unit is controlled at the first discharge timing. When the gap is smaller than the threshold value, the same discharge control based on the speed and the gap can be performed in the acceleration process, the constant speed process, and the deceleration process.

  A liquid discharge method that solves the above problem is a liquid discharge method that discharges liquid to a discharge target, and discharges liquid from the liquid discharge unit in an acceleration process in which the liquid discharge unit and the discharge target move relative to each other. A first ejection step, a second ejection step for ejecting liquid from the liquid ejection section in a constant speed process in which the liquid ejection section and the ejection object move relatively, and the liquid ejection section and the ejection object. And a third discharge step for discharging liquid from the liquid discharge portion in the deceleration process in which the liquid discharge portion moves relatively, and in the first discharge step and the third discharge step, the liquid discharge portion and the discharge target object The discharge timing when the relative speed of the relative movement is the same in the acceleration process and the deceleration process delays the discharge timing in the acceleration process from the discharge timing in the deceleration process. According to this method, it is possible to obtain the same effect as that of the liquid ejecting apparatus.

  A liquid discharge method that solves the above problem is a liquid discharge method that discharges liquid to a discharge target, and discharges liquid from the liquid discharge unit in an acceleration process in which the liquid discharge unit and the discharge target move relative to each other. A first ejection step, a second ejection step for ejecting liquid from the liquid ejection section in a constant speed process in which the liquid ejection section and the ejection object move relatively, and the liquid ejection section and the ejection object. And a third discharge step for discharging the liquid from the liquid discharge unit in the deceleration process in which the liquid discharge unit relatively moves, and in the constant speed process, a relative speed at a constant speed between the liquid discharge unit and the discharge target object. And the discharge control of the liquid discharge unit at a first discharge timing based on the gap between the liquid discharge unit and the discharge target, and in the acceleration process, the first discharge timing based on the relative speed and the gap at the time of acceleration. Too late The liquid discharge unit is controlled to be discharged at the second discharge timing, and in the deceleration process, the liquid discharge unit is controlled to be discharged at a second discharge timing that is earlier than the first discharge timing based on the relative speed and the gap at the time of deceleration. And a liquid ejection method. According to this method, it is possible to obtain the same effect as that of the liquid ejecting apparatus.

1 is a perspective view illustrating a printer in a state where an exterior cover is removed according to an embodiment. FIG. 3 is a schematic diagram illustrating a bottom surface of an ejection head and an ejection drive system. The schematic diagram which shows the structure and encoder signal of a linear encoder. The graph which shows the speed profile when a carriage scans once. FIG. 4A is a schematic front view illustrating ink droplet ejection in a constant speed process, and FIG. FIG. 3 is a block diagram illustrating an electrical configuration of the printer. The block diagram which shows the electric constitution of a discharge control system. FIG. 4 is a schematic front view illustrating a state of ink droplets affected by wind flowing into a gap between an ejection head and a medium. The graph which shows the wind speed distribution of an acceleration process. The graph which shows the wind speed distribution of a constant speed process. The graph which shows the wind speed distribution of a deceleration process. The graph which shows the relationship between the shift | offset | difference of a landing position in an acceleration process, a constant speed area | region, and a deceleration process, and a gap. The graph which shows the quadratic curve for the landing position shift correction | amendment used for correction | amendment of a delay value. The graph which shows the relationship between the carriage speed and wind correction value at the time of PG1. The graph which shows the relationship between the carriage speed and wind correction value at the time of PG6. (A) is a graph showing landing deviation between acceleration process and deceleration process without correction, and (b) is a graph showing landing deviation between acceleration process and deceleration process with correction. The graph which shows the relationship between the shift | offset | difference of the landing position in the acceleration process at the time of correction | amendment, a constant speed area | region, and a deceleration process, and a gap. The flowchart which shows a discharge control routine.

Hereinafter, an embodiment of a serial printer as an example of a liquid ejection apparatus will be described with reference to the drawings.
As shown in FIG. 1, a serial printer 11 (serial printer) as an example of a liquid ejection apparatus is an ink jet color printer as an example. In FIG. 1, the printer 11 has a main body frame 12 having a substantially square box shape in which the outer housing is removed and the upper side and the front side are open. A feed tray 14 having a pair of edge guides 13 capable of positioning a recording medium P such as a plurality of sheets (hereinafter also simply referred to as “medium P”) in the width direction is provided on the back surface of the main body frame 12. An automatic feeding device 15 is provided. The automatic feeding device 15 feeds one sheet of the medium group set on the feeding tray 14 into the main body of the printer 11. The automatic feeding device 15 may be a cassette feeding method or a roll paper feeding method.

  As shown in FIG. 1, a guide shaft 21 having a predetermined length is installed between the left and right side walls of the main body frame 12 in FIG. 1, and the carriage 22 is moved along the guide shaft 21 in the scanning direction X1 (main scanning direction). ) To be reciprocally movable. The carriage 22 is fixed to a part of an endless timing belt 24 wound around a pair of pulleys 23 and 23 attached to the inside of the back plate of the main body frame 12. The right pulley 23 in FIG. 1 is connected to the drive shaft of the carriage motor 25. When the carriage motor 25 is driven forward / reversely, the timing belt 24 is rotated forward / reversely, whereby the carriage 22 reciprocates in the scanning direction X1.

  As shown in FIG. 1, a plurality of (four in the example of FIG. 1) ink cartridges 26 as an example of a liquid supply source are mounted on the cartridge holder 22 a at the top of the carriage 22. In each ink cartridge 26, as an example of the liquid, for example, inks of a plurality of colors (four colors in the example of FIG. 1) including black (K), cyan (C), magenta (M), and yellow (Y) are each 1 Each color is housed. Of course, the number of ink colors is not limited to four, and may be one color (black as an example), two colors, three colors, or five to eight colors. The mounting method of the ink cartridge 26 may be a so-called off-carriage type in which the ink cartridge is mounted in a cartridge holder (not shown) installed on the main body frame 12 side instead of the so-called on-carriage type as shown in FIG. The liquid supply source may be an ink replenishment type ink tank attached to the side surface of the printer 11 or the like, for example.

  As shown in FIG. 1, an ejection head 27 is provided below the carriage 22. The ejection head 27 has a nozzle opening surface 27a in which a plurality of nozzles 27b are opened on a surface facing the fed medium P, and the ink supplied from each ink cartridge 26 is supplied to each nozzle 27b (both of them). (See FIG. 2). The discharge head 27 is communicably connected to a controller 50 (see FIG. 6) as an example of a control unit provided in the printer 11 via a flexible flat cable FC connected to the carriage 22. The discharge head 27 is driven to discharge based on discharge data transferred from the controller 50 during printing.

  As shown in FIG. 1, a long support base 28 is disposed at a lower position facing the moving area (scanning area) of the ejection head 27 so that the scanning direction X1 is the longitudinal direction. The support base 28 defines an interval (gap) between the ejection head 27 and the medium P. The support base 28 extends in the scanning direction X1 over a region slightly wider than the entire printing region where printing by the discharge head 27 is performed. During printing, the ink droplets ejected from the nozzles 27b of the ejection head 27 are landed on the portion of the medium P supported by the upper surface (support surface) of the support base 28, thereby forming dots. Documents, images, etc. are printed on the screen.

  A linear encoder 29 that outputs a detection signal (encoder pulse signal) including a number of pulses proportional to the amount of movement of the carriage 22 is provided on the back side of the carriage 22 so as to extend along the guide shaft 21. . The printer 11 grasps the position and speed (number of pulses per unit time) of the carriage 22 in the scanning direction X1 by counting the number of pulse edges of the detection signal of the linear encoder 29, and information on these positions and speeds. Based on this, the position control and speed control of the carriage 22 are performed. The encoder pulse signal output from the linear encoder 29 is also used for discharge control for determining the discharge timing at which the discharge head 27 discharges ink droplets. That is, the ejection timing signal PTS that determines the ink ejection timing of the ejection head 27 is generated based on the encoder pulse signal output from the linear encoder 29.

  Further, a feeding motor 30 and a conveying motor 31 are disposed on the lower right side of the main body frame 12 in FIG. The feed motor 30 drives a feed roller (not shown) to feed the medium P one by one from the top. The fed medium P is sent out until its leading end reaches the conveying roller pair 32.

  The conveyance motor 31 shown in FIG. 1 is a power source that rotates a conveyance roller pair 32 and a discharge roller pair 33 that are respectively arranged at upstream and downstream positions of the support base 28 in the conveyance direction F1. Each of the roller pairs 32 and 33 includes drive rollers 32a and 33a that are rotationally driven by the power of the transport motor 31, and driven rollers 32b and 33b that are in contact with the drive rollers 32a and 33a and rotate. The fed medium P is intermittently transported in the transport direction F <b> 1 while being supported (supported) by the support base 28 and being sandwiched (nip) between the pair of rollers 32 and 33. In the present embodiment, an example of a conveyance unit is configured by a feeding mechanism including the feeding motor 30 and a feeding roller and a conveyance mechanism including the conveyance motor 31 and both roller pairs 32 and 33.

  The serial printer 11 shown in FIG. 1 has a printing operation for ejecting ink from the nozzles 27b (see FIG. 2) of the ejection head 27 toward the medium P while reciprocating the carriage 22 in the scanning direction X, and the medium P. A document, an image, or the like is printed on the medium P by substantially alternately repeating the feeding operation for transporting to the next scanning position (printing position) in the transport direction F1. During the printing operation, the area of the medium P that is nipped between the two roller pairs 32 and 33 is supported on the upper surface of the support base 28, so that the interval between the ejection head 27 and the medium P is a predetermined gap (paper gap). Retained. The printed medium P is discharged onto a discharge stacker (discharge tray) (not shown) from a discharge port (not shown) that opens at the front of the apparatus main body of the printer 11.

  In FIG. 1, one end position (right end position in FIG. 1) on the movement path of the carriage 22 is a home position HP (home position) where the carriage 22 stands by when not printing. A maintenance device 34 that performs maintenance on the ejection head 27 is disposed at a position directly below the carriage 22 at the home position HP. The maintenance device 34 includes a cap 35, a wiper 36, a suction pump 37, and the like.

  During printing, the carriage 22 moves to the home position HP, and performs flushing by ejecting ink droplets unrelated to printing from the nozzles of the ejection head 27 toward the cap 35 (empty ejection). The thickened ink in the nozzle is discharged by flushing to prevent clogging of the nozzle. Further, when the carriage 22 stands by at the home position HP, the raised cap 35 caps the ejection head 27, thereby preventing the ink in the nozzle from being thickened or dried. At a predetermined time, the maintenance device 34 forcibly sucks ink from the nozzles 27b by driving the suction pump 37 in a state where the discharge head 27 arranged at the home position HP is capped with the cap 35. Cleaning is performed to remove the thickened ink and bubbles in the nozzle. The waste ink sucked and discharged during this cleaning is discharged to a waste liquid tank 38 disposed below the support base 28. The power source of the suction pump 37 is the transport motor 31 or an electric motor dedicated thereto.

  In the printer 11, the ink ejection is performed both in the forward movement in which the ejection head 27 moves away from the home position HP and in the backward movement in which the ejection head 27 moves in the direction approaching the home position HP (bidirectional). Printing and unidirectional printing are performed in which ink droplets are ejected only when the ejection head 27 moves forward, and when the carriage 22 returns, the carriage 22 is returned. The printer 11 according to the present embodiment is a high-quality print mode that is used for printing a photograph or the like and prioritizes the print quality over the print speed, and a normal print that is used for printing a document or the like and prioritizes the print speed over the print quality. A plurality of print modes including a mode. For example, unidirectional printing is performed in the high quality printing mode, and bidirectional printing is performed in the normal printing mode.

  As shown in FIG. 2, a total of n nozzle openings 27a, which are the bottom surface of the ejection head 27, are arranged in a line at a constant nozzle pitch in the transport direction F1 (sub-scanning direction) (vertical direction in FIG. 2). A plurality of nozzle rows N composed of (for example, 400) nozzles # 1 to #n (where n is a natural number of 2 or more) are formed. As an example, the ejection head 27 includes a total of eight nozzle rows N from A rows to H rows. The nozzle rows in the even rows (B, D, F, H rows) with respect to the nozzle rows in the odd rows (A, C, E, G rows) from the left are downstream in the transport direction F1 by the half pitch of the nozzle pitch ( It is shifted to the upper side in FIG. In this example, “# 1 to #n” are assigned to the nozzles constituting the nozzle row in order from the upstream side in the transport direction F1. In this example, printing is performed in four colors of black (K), cyan (C), magenta (M), and yellow (Y) using a total of eight nozzle rows. Examples of combinations of two nozzle rows having the same ink color are (A row, H row), (B row, G row), (C row, F row) (D row, E row). As long as the combination is an odd number column and an even number column, other combinations may be used. By printing the same color with the two nozzle rows of the odd and even rows, high-resolution printing is possible with a resolution that is half the nozzle pitch.

  Also, the ejection head 27 includes the same number of ejection drive elements 39 shown in FIG. 2 corresponding to the nozzles # 1 to #n as the number of nozzles (however, in FIG. Only one nozzle row is drawn). The ejection drive element 39 is composed of, for example, a piezoelectric vibration element or an electrostatic drive element, and when a voltage pulse having a predetermined drive waveform is applied, the ink chamber communicating with the nozzle is expanded and compressed by an electrostrictive action or an electrostatic drive action. As a result, ink droplets are ejected from the nozzles. The ejection head 27 may be a thermal type in which the ejection driving element 39 is a heater element, and ink droplets are ejected from the nozzles using the expansion pressure of bubbles generated by film boiling of the ink heated by the heater element.

  As shown in FIG. 2, the ejection head 27 includes n ejection units 40 each having nozzles 27 b and ejection drive elements 39 for each of the nozzle arrays A to H. Each nozzle row is provided with a discharge drive element group 41 including n discharge drive elements 39. Voltage control (discharge control) of the discharge drive element 39 is performed via the head drive circuit 54 by the controller 50 (see FIG. 6).

  The linear encoder 29 shown in FIG. 3 includes a tape-shaped code plate 42 (linear scale) in which a large number of slits 42a are formed at a constant pitch, and an optical sensor 43 that moves with the carriage 22 using the code plate 42 as a detection target. Prepare. The optical sensor 43 includes a light emitting element 44 and a light receiving element 45 that face each other with a tape-shaped code plate 42 interposed therebetween. The light emitting element 44 has a pair of light emitting portions 44a arranged in the scanning direction X, and the light receiving element 45 has a pair of light receiving portions 45a facing the pair of light emitting portions 44a. The optical sensor 43 outputs an encoder signal (detection signal) having a number of pulses corresponding to the number of intermittent light passing through the slits 42 a as the carriage 22 is scanned. The optical sensor 43 outputs two types of encoder signals, phase A and phase B, which are out of phase by 3/4 period. When the pulse period of the encoder signal is set to “T”, 1 / T (1 / second) that is the reciprocal of the period T is proportional to the carriage speed.

  FIG. 6 shows the electrical configuration of the printer 11. As shown in FIG. 6, the printer 11 includes a controller 50, motor drive circuits 51 to 53, and a head drive circuit 54. The printer 11 also includes the above-described linear encoder 29 as an input system. The controller 50 drives and controls the carriage motor 25 via the motor drive circuit 51, and moves the carriage 22 and the ejection head 27 in the scanning direction X1 according to a predetermined speed profile with acceleration, constant speed, and deceleration. One scan of 22 is performed. The controller 50 controls the feeding motor 30 via the motor driving circuit 52 to feed the medium P by rotating the feeding roller, and after the medium P is fed to a predetermined position, the motor 50 By driving and controlling the transport motor 31 via the drive circuit 53, the medium P being printed is transported intermittently. Further, the controller 50 controls driving of the ejection head 27 (specifically, the ejection drive element 39 built in each nozzle) via the head drive circuit 54 based on print data PD input from a host device (not shown), for example. To do. Examples of the host device include personal computers, smart phones, mobile phones, tablet PCs, and portable terminals such as personal digital assistants (PDA (Personal Digital Assistants)).

  The controller 50 includes a CPU 60 (central processing unit), an ASIC 61 (Application Specific Integrated Circuit) (customized integrated circuit) as a custom LSI, a ROM 62, a RAM 63, a nonvolatile memory 64 (for example, a flash ROM), an input interface 65, an input / output The interface 66 and the clock circuit 67 are included. The CPU 60, ASIC 61, ROM 62, RAM 63, nonvolatile memory 64, input interface 65 and input / output interface 66 are connected to each other via a bus 68.

  The ROM 62 stores various control programs and various data. The nonvolatile memory 64 stores various programs including a print control program (firmware program), various data necessary for print processing, and the like. The nonvolatile memory 64 stores a program PR for controlling ejection timing of the ejection head 27, speed control data VD for carriage, and the like.

  The RAM 63 temporarily stores a program executed by the CPU 60, various data that are calculation results and processing results by the CPU 60, and various data processed by the ASIC 61. The RAM 63 includes a reception buffer 63a that stores received print data PD, and an intermediate buffer that stores intermediate data such as color separation data and halftone data generated in the process of generating ejection data from the print data PD. 63b, and an output buffer 63c for temporarily storing ejection data before being output to the head drive circuit 54. The ejection data is data for one pass in which the ejection head 27 ejects ink droplets from the nozzles in the course of one scan.

  Next, speed control of the carriage 22 performed using the carriage speed control data VD will be described with reference to FIG. As shown in the graph of FIG. 4, the speed control data VD is data indicating the relationship between the carriage position and the carriage speed. The CPU 60 refers to the speed control data VD from the carriage position acquired based on the encoder signal, obtains a target speed corresponding to the position, and performs feedback control to reduce the difference between the actual speed and the target speed. However, feedforward control may be performed for at least a part of the carriage movement range (for example, an acceleration / deceleration region). In this example, a section from the carriage position 22 to the origin position P0 to the position P2 is an acceleration area from the stop state (speed “0”) to the constant speed Vc, and a range from the position P2 to the position P3 is fixed. A constant speed region where the speed is controlled at the speed Vc, and a range from the position P3 to the stop position P5 is a deceleration area where the speed is decelerated from the constant speed Vc to the stop (speed “0”). In this embodiment, not only constant speed printing is performed in the constant speed area of the carriage 22, but also printing is performed in a part of the acceleration area and a part of the deceleration area on both sides of the constant speed area. Acceleration / deceleration printing that performs deceleration printing is used. That is, the printable range in the scanning direction X1 (carriage movement direction) includes the constant speed printing performed in the constant speed area, the accelerated printing performed in the section between the positions P1 and P2 in the acceleration area, and the deceleration area. Reduced printing performed in the section between the positions P3 to P4 is set. In the following description, the acceleration region where acceleration printing is performed and the deceleration region where deceleration printing is performed are collectively referred to as “acceleration / deceleration region”.

  Next, the discharge control of the discharge head 27 will be described with reference to FIG. As shown in FIG. 5 (a), when the head speed Vh is a constant speed Vc (Vh = Vc), the speed Vm from the nozzle 27b of the ejection head 27 is perpendicular to the nozzle opening surface 27a, that is, vertically downward. Ink droplets are ejected at (initial speed). The ejected ink droplets fly at the direction and speed of the combined velocity vector of the vertical velocity Vm in the vertical direction and the head velocity Vh = Vc in the head traveling direction, and land on the target landing position on the medium P. At this time, the point in time at which the predetermined position is reached by the first distance from the target landing position is set as the discharge timing.

  On the other hand, as shown in FIG. 5B, in the acceleration / deceleration process, the head speed Vh moves at a speed Va (<Vc) lower than the constant speed Vc. At this time, when the ink droplet is ejected from the position indicated by a two-dot chain line in FIG. 5B with respect to the target landing position as in the case of the constant speed process, the ejected ink droplet has a velocity Vm that is directed downward in the vertical direction. Then, it flies at the direction and speed of the combined velocity vector of the head velocity Vh = Va (Vc) in the head traveling direction, and lands on the target landing position on the medium P. As indicated by a two-dot chain line in FIG. 5B, the robot lands at a position considerably before the target landing position. For this reason, in the acceleration / deceleration process, the ink droplets are made to land at the target landing position by ejecting the target landing position by delaying the ejection timing by the delay time Δt compared to the constant speed process. At this time, the point in time when the position reaches a position a second distance before the target landing position is set as the discharge timing.

  The delay value Dp (the number of PTS delay stages) is expressed by the equation Dp = (PG / Vm) * (1 / Tref−1 / Tprt) using the gap PG and the discharge speed Vm. Here, Tref is a reference period (reference pulse period) when the carriage 22 moves at a constant speed Vc, and Tprt is a current period (current pulse period) corresponding to the current speed Vcr of the carriage 22.

  Returning to FIG. 6, the input interface 65 is communicably connected to the host computer in a wired or wireless manner, and receives print data PD transferred from the host computer via, for example, a communication cable (none of which is shown). Input to the printer 11. The print data PD input (received) by the printer 11 is stored in the reception buffer 63 a of the RAM 63 from the input interface 65. The ASIC 61 analyzes (interprets) a command described in the print language included in the print data PD to generate an intermediate code, and the intermediate code in the intermediate buffer 63b has pixels corresponding to the print dots determined in advance. And an image development processing unit 72 that converts the data into bitmap data indicated by the gray scales and develops the data on the RAM 63. The image development processing unit 72 performs data development processing for each scan, and the output buffer 63c stores ejection data (tone value data) for each scan. Then, the ejection data (gradation value data) for one scan read from the output buffer 63c is output from the input / output interface 66 to the head drive circuit 54 on the carriage 22 side via the flexible flat cable FC. The head drive circuit 54 drives and controls the ejection drive element 39 in the ejection head 27 based on the received ejection data, and controls ejection of ink droplets from the nozzles.

  Further, when the CPU 60 executes the print control program, the motor command value of the scanning system targeting the carriage speed determined according to the carriage position at that time is referred to through the input / output interface 66 by referring to the speed control data VD. By outputting to the motor drive circuit 51, the carriage motor 25 is driven and controlled by the motor drive circuit 51. By the drive control of the carriage motor 25, for example, the carriage 22 during printing is speed-controlled according to the speed profile shown in the graph of FIG.

  In addition, the motor command value of the transport system generated by the CPU 60 executing the print control program is output to the motor drive circuits 52 and 53 via the input / output interface 66, whereby the feed motor 30 and the transport motor. 31 is driven and controlled. The feed mechanism and the transport mechanism are driven by the drive control of these motors 30 and 31 to feed the medium P, intermittently transport the medium P to the next printing position, and discharge the medium P after the printing is completed. Is done. The controller 50 is electrically connected with an encoder (rotary encoder) (not shown) that outputs an encoder signal having a number of pulses proportional to the rotation amount of the transport motor 31 and a paper detector as an input system. The controller 50 controls the transport of the medium P by the motors 30 and 31 in accordance with the transport position of the medium P obtained by counting the pulse edges of the encoder signal input from the encoder. The motor command value output from the CPU 60 is, for example, a PWM (pulse width modulation) command value. The current of each motor 25, 30, 31 is controlled according to each command value, and each motor 25, 30, 31 is controlled. It is possible to drive by the commanded rotational speed and the commanded drive amount.

  The ASIC 61 shown in FIG. 6 performs processing for generating an ejection timing signal PTS for determining ejection timing of ink droplets ejected from the nozzles of the ejection head 27, in addition to image development processing and the like. Therefore, the ASIC 61 includes an edge detection circuit 73 and a print timing generation circuit 74 that are used to generate the ejection timing signal PTS. The edge detection circuit 73 receives an encoder signal from the optical sensor 43 of the linear encoder 29 and detects its rising edge, and generates a pulse every time the rising edge is detected to generate a cycle of the encoder signal (encoder cycle). A reference pulse signal RS having the same cycle is output.

  The print timing generation circuit 74 performs signal generation processing using the reference pulse signal RS input from the edge detection circuit 73 and the clock signal CK input from the clock circuit 67 to generate the ejection timing signal PTS. The signal generation process performed by the print timing generation circuit 74 includes a period division process (multiplication process) in which one period of the reference pulse signal RS is divided (multiplication) to generate a pulse signal, and the obtained pulse signal is transmitted to the carriage 22. And a delay process for generating the discharge timing signal PTS by delaying it by a delay time corresponding to the speed and the moving direction (difference between forward movement and backward movement). The ejection timing signal PTS generated by the print timing generation circuit 74 is output to the head drive circuit 54.

  A drive pulse selected based on the ejection data is applied to the ejection drive element 39 provided for each nozzle in the ejection head 27. When the ejection drive element 39 is driven by the application of the drive pulse, the ink chamber provided for each nozzle expands and compresses, and ink droplets are ejected from the nozzle. The head drive circuit 54 determines an application timing at which a drive pulse is applied to each ejection drive element 39 in the ejection head 27 based on the ejection timing signal PTS.

  The reference pulse signal RS output from the edge detection circuit 73 is input to the CPU 60 as a position detection pulse. The CPU 60 acquires the moving direction of the carriage 22 based on the phase difference between the A phase and the B phase included in the encoder pulse signal from the linear encoder 29. Then, the CPU 60 counts the rising edge of the reference pulse signal RS with the CR counter 75, increments the counted value when the carriage moves forward, and decrements when the carriage moves backward, and based on the obtained count value, for example, the home position of the carriage 22 A position in the scanning direction X1 with HP as the origin (hereinafter also referred to as “carriage position”) is detected. This carriage position is used for speed control of the carriage motor 25 executed with reference to the speed control data VD (FIG. 4).

  The print timing generation circuit 74 outputs speed data to the CPU 60. Specifically, the print timing generation circuit 74 counts the number of pulse edges of the clock signal CK from the clock circuit 67 during the period of one cycle of the reference pulse signal RS input from the edge detection circuit 73 to thereby obtain the current carriage speed. The period Tprt of the reference pulse signal RS that is inversely proportional to Vcr is counted. Further, the print timing generation circuit 74 outputs the value obtained by calculating the reciprocal of the cycle Tprt to the CPU 60 as the current speed data Vcr. The print timing generation circuit 74 receives from the CPU 60 set values such as a reference value and a correction value necessary for determining a delay value Dp, which will be described later, which determines the output timing of the ejection timing signal PTS. The ASIC 61 includes a PF counter (not shown) that counts the number of pulse edges of an encoder pulse signal input from an encoder (not shown) that detects the rotation of the transport motor 31. Then, when a detector (not shown) detects the medium P being fed, the ASIC 61 causes the PF counter to start counting. Thus, the CPU 60 performs position control and speed control of the medium P by the transport motor 31 based on the transport position of the medium P acquired from the count value of the PF counter.

  As shown in FIG. 7, the printer 11 includes a print control unit 81 having various functional units that is constructed by a computer in the controller 50 executing a program PR. The print control unit 81 includes a main control unit 82, a carriage control unit 83, a head control unit 84, and a drive pulse generation unit 86 as functional units.

The main control unit 82 gives instructions to the units 83, 84, and 86 to control various controls such as carriage scanning control and ejection head ejection timing control.
The carriage control unit 83 performs speed control when moving the carriage 22 in the scanning direction X <b> 1 by driving and controlling the carriage motor 25. At this time, the carriage control unit 83 obtains the actual speed (current carriage speed Vcr) of the carriage 22 during printing, and refers to the actual speed Vcr based on the current carriage position and the speed control data VD (see FIG. 4). Thus, feedback control is performed so as to approach the target speed acquired. As a result, the carriage control unit 83 causes the carriage 22 to perform one scan (movement for one pass) by accelerating / constant / decelerating the carriage 22 along the speed profile shown in FIG.

  The head controller 84 performs ejection control for ejecting ink droplets from the nozzles 27 b of the plurality of ejection units 40 included in the ejection head 27. The head control unit 84 includes an image development processing unit 72 (see FIG. 6). The image development processing unit 72 generates ejection data from the print data PD and outputs the ejection data to the head drive circuit 54. Further, the head control unit 84 outputs a reference value (delay reference value) serving as a reference when correcting the ejection timing to the print timing generation circuit 74. The reference value is a reference delay value that is set so that an appropriate discharge timing is obtained when the carriage speed Vcr is the constant speed Vc. This reference value is set for each constant speed Vc corresponding to the print mode. In the case of a printing mode in which bidirectional printing is performed, since the proper ejection timing is different between the forward movement process and the backward movement process of the carriage 22, different reference values are used in the forward movement process and the backward movement process.

  The drive pulse generator 86 generates a drive pulse including a plurality of types (for example, two types or three types) of discharge waveforms for each discharge cycle (one cycle) at which one dot is discharged from the nozzle 27 b and outputs the drive pulse to the head drive circuit 54. To do. The ejection head 27 of the present embodiment is capable of ejecting ink droplets of a plurality of sizes, for example, three types of large, medium and small ink droplets.

  The head drive circuit 54 inputs ejection data and drive pulses. The head drive circuit 54 selects one type or two types of discharge waveforms according to the gradation value of the pixel of the input discharge data from the input drive pulses, and discharges the drive pulse of the selected discharge waveform to the discharge timing. The ink droplet size is controlled by applying to the ejection driving elements 39 constituting the ejection driving element group 41 at a timing based on the signal PTS. The discharge data is, for example, data representing a pixel gradation value in 2 bits. When the gradation value is “00”, non-ejection, when “01” is small, and when it is “10”, it is medium. A dot, “11”, represents a large dot. Then, by applying a drive pulse having a discharge waveform corresponding to the gradation value of the discharge data to the discharge drive element 39, the ink chamber expands and compresses due to, for example, electrostriction, so that the ink 27 responds to the discharge data. Ink droplets of different sizes are ejected. The size of the ink droplets ejected from the ejection head 27 may be one type instead of a plurality of types.

  As shown in FIG. 8, the ink droplets ejected from the nozzles by the ejection head moving at a speed Vcr in the scanning direction X together with the carriage 22 are caused to flow by the wind (airflow) of the wind speed Vair flowing into the ejection area. Land on the medium P along a flight path that draws a curve as shown. For this reason, landing is made at a position Pr that is shifted by the amount of the air that has been swept away by the wind with respect to the target landing position Pg when landing on the assumed flight path shown by the one-dot chain line in FIG. Here, the downward direction in the vertical direction with respect to the nozzle opening surface 27a of the ejection head 27 (in this example, the direction of gravity) is defined as the Y direction. The ink droplet in flight flies at a combined speed of the speed component Vx in the scanning direction X equal to the speed Vcr at the time of ejection of the carriage 22 and the speed component Vy in the Y direction equal to the ejection speed.

  Here, a distance y in the Y direction with the nozzle opening surface 27a of the ejection head 27 as the origin is assumed. In FIG. 8, when the gap between the nozzle opening surface 27a and the medium P is PG, each position where the ink droplet is flying through the gap PGo is represented by a distance y. The gap PG changes according to the type of the medium P and the print mode.

Here, the equation of motion is expressed by the following equations (1) and (2).
X direction: mx ″ = 1/2, Cd, ρair, Ap, (Vairx−x ′) ^ 2 (1)
Y direction: my ″ = 1/2, Cd, ρair, Ap, (Vairy−y ′) ^ 2 + mg (2)
Here, x is the position in the X direction, y is the position in the Y direction, Cd is the drag coefficient, m is the mass of the ink droplet (m = 4π / 3 · ρink), ρink is the ink density, and Ap is the surface area of the ink droplet ( Ap = πr ^ 2 (where r is the radius of the ink droplet), ρair is the air density, Vairx is the wind velocity in the x direction (air flow velocity), and Vairy is the wind velocity in the y direction. “X ″” represents a second-order derivative at time x, “x ′” represents a first-order derivative at time x, “y ″” represents a second-order derivative at time y, “y” “” Represents the first derivative in the time of y. The symbol “·” represents a multiplication operator, and the symbol “^” represents a power operator.

Here, the wind speeds Vairx and Vairy are given by the following wind speed model. The wind speed model employed in this example is represented by the sum of a primary model indicating a shear flow when one side of a parallel plate moves and a parabolic model indicating a Hagen-Poiseuille flow when the wind flows into the parallel plate. By this wind speed model, the wind speeds Vairx and Vairy are expressed by the following (3) and (4).
Vairx = Vcr / PG ・ (PG−y) + Vpeak ・ (1−4 / PG ^ 2 ・ (y−PG / 2) ^ 2) (3)
Vary = 0 (4)
Here, Vcr is the carriage speed, and Vpeak is the peak flow velocity of the parabolic distribution. Vpeak is a constant determined by the shape of the carriage, the internal space of the printer, the speed and acceleration of the carriage, and takes a negative value during acceleration and a positive value during deceleration. During acceleration, when the carriage 22 moves with respect to the stopped space, air flows in the −X direction between the gaps PG at the rate of volume movement, so the constant Vpeak becomes negative. Further, at the time of deceleration, since the inertia of the air flowing between the gaps PG during the constant speed movement works in the X direction when the carriage 22 is decelerated, the constant Vpeak becomes positive. In the above equation (1), the term Vcr / PG • (PG−y) is the primary model, and the term Vpeak • (1−4 / PG ^ 2 • (y−PG / 2) ^ 2) is a parabolic model. It corresponds to.

  Next, the wind speed distribution in the gap PG during the movement of the carriage 22 in the above wind speed model will be described with reference to FIGS. The graphs of FIGS. 9 to 11 show the wind speed distribution in the acceleration process, constant speed process, and deceleration process of the carriage 22, respectively. In each graph, the vertical axis represents the distance y (position) in the Y direction from the nozzle opening surface, and the horizontal axis represents the wind speed Vair (Vairx) in the X direction. In this example, the gap PG is 1.6 mm. In this example, the carriage speed Vcr in the acceleration process is 0.5 m / second, the carriage speed Vcr in the constant speed process is 0.7 m / second, and the carriage speed Vcr in the deceleration process is 0.5 m / second. In each graph, the velocity distribution VD1 based on the primary model indicating the shear flow when one side of the parallel plate moves is indicated by a solid line, and the velocity distribution VD2 based on the parabolic model indicating the Hagen-Poiseuille flow when the wind flows into the parallel plate is one point. Shown with a chain line.

  As shown in FIG. 9, in the acceleration process, the wind speed distribution WD based on the wind speed model is indicated by a thick line in the graph. This wind speed distribution WD is represented by the sum of a speed distribution VD1 based on a primary model indicated by a solid line in the graph and a speed distribution VD2 based on a parabolic model indicated by a one-dot chain line. In the acceleration process, as can be seen from the wind speed distribution WD, the wind speed Vair is equal to the carriage speed Vcr (Vair = Vcr (= 0.5)) at the nozzle opening surface (y = 0), and the surface of the medium P (medium surface). Becomes 0 (zero) (Vair = 0), and takes a parabolic value convex in the negative direction between the gaps PG.

  Further, as shown in FIG. 10, in the constant speed process, the wind speed distribution WD based on the wind speed model is indicated by a thick line in the graph. This wind speed distribution WD is represented by the sum of a speed distribution VD1 based on a primary model indicated by a solid line in the graph and a speed distribution VD2 based on a parabolic model indicated by a one-dot chain line. In the constant speed process, as can be seen from the wind speed distribution WD, the wind speed Vair is equal to the carriage speed Vcr at the nozzle opening surface (y = 0) (Vair = Vcr (= 0.7 m / sec)), and the surface of the medium P ( It becomes 0 (zero) (Vair = 0) at the medium surface, and takes a parabolic value slightly convex in the minus direction between the gaps PG.

  Further, as shown in FIG. 11, in the deceleration process, the wind speed distribution WD based on the wind speed model is indicated by a thick line in the graph. This wind speed distribution WD is represented by the sum of a speed distribution VD1 based on a primary model indicated by a solid line in the graph and a speed distribution VD2 based on a parabolic model indicated by a one-dot chain line. In the deceleration process, as can be seen from the wind speed distribution WD, the wind speed Vair is equal to the carriage speed Vcr at the nozzle opening surface (y = 0) (Vair = Vcr (= 0.5 m / sec)) and the surface of the medium P (medium The surface becomes 0 (zero) (Vair = 0), and takes a parabolic value convex in the plus direction between the gaps PG.

  Next, the relationship between the gap PG and the landing position will be described with reference to FIG. In the graph shown in FIG. 12, the vertical axis represents the gap PG (μm), and the horizontal axis represents the landing position Px (mm). The landing position Px has the X direction position of the nozzle at the start of discharge as the origin, and the X direction is the plus direction. In the constant speed process, the landing position Px shifts to the plus side as the gap PG increases. This is because the ink droplet ejection speed Vm has a velocity component Vx in the X direction (plus direction), so that the ink droplet advances in the plus direction from the position (Px = 0) at the start of ejection as the gap PG increases. .

  On the other hand, in the acceleration process, when the gap PG is in the range of 0 to 1 mm, there is almost no deviation of the landing position Px from the landing position in the constant speed process. However, when the gap PG exceeds 1 mm, the landing position Px shifts to the minus side as the gap PG increases with respect to the landing position in the constant speed process. In particular, when the gap PG exceeds 2.5 mm, the shifting of the minus side shifts. The size increases rapidly.

  Further, in the deceleration process, when the gap PG is in the range of 0 to 1 mm, there is almost no deviation of the landing position Px from the landing position in the constant speed process. However, when the gap PG exceeds 1 mm, the landing position Px shifts to the plus side as the gap PG increases with respect to the landing position in the constant speed process. In particular, when the gap PG exceeds 2.5 mm, the plus side deviation is reduced. The size increases rapidly.

  When the gap PG is in the range of 0 to 1.5 mm, the deviation between the landing position in the acceleration process and the deceleration process with respect to the landing position in the constant speed process is within 50 μm or less, which is the allowable range of the printer of this example. However, when the gap PG exceeds 1.5 mm, the deviation between the landing position in the acceleration process and the deceleration process with respect to the landing position in the constant speed process exceeds the allowable range of 50 μm, and the deviation increases as the gap PG increases.

  In the present embodiment, the gap PGp (also referred to as “platen gap”) between the nozzle opening surface 27a and the support base 28 is adjusted in a plurality of stages according to the medium type (for example, paper type) and the printing mode. . The printer 11 is provided with an elevating mechanism (not shown) that can move the ejection head 27 up and down. By changing the position of the ejection head 27 relative to the guide shaft 21 in the vertical direction, the medium type and the printing mode at that time are changed. The gap PGp is adjusted accordingly. For example, one of the six gaps PG1 to PG6 is selected as the gap PGp. PG1 to PG6 are, for example, 1.3, 1.7, 1.9, 2.6, 3.4, and 4.3 mm. For example, the gap PG1 is used when the medium type is “plain paper” having a relatively small thickness, and the gap PG6 is used when the medium type is an “envelope” having a relatively large thickness.

  As can be seen from the graph shown in FIG. 12, when the gap PG is PG1 + plain paper (PG is about 1.2 mm) and PG2, the deviation of the landing position is within the allowable range. On the other hand, when the gap PG is PG3 to PG6, PG6 + envelope (PG is about 3.8 mm), the deviation of the landing position exceeds the allowable range. For this reason, in this embodiment, when the gap PG is equal to or larger than the threshold SG at which the deviation of the landing position exceeds the allowable range, the ejection timing is corrected.

Next, with reference to FIGS. 13 and 14, a method for correcting the ejection timing when the gap PG exceeds the threshold value will be described. In the present embodiment, the ejection timing is corrected by correcting the delay value Dp in consideration of the influence of wind. The delay value Dp is given by the following equation.
Dp = PG / Vm · (1 / Tref−1 / Tprt) + α (5)
Here, PG is a gap, Vm is a discharge speed, Tref is a reference pulse period at a constant speed of the carriage, and Tprt is a current reference pulse period. Α is a correction term indicating a wind correction value for eliminating the influence of wind. 1 / Tref is proportional to the constant speed of the carriage, and 1 / Tprt is proportional to the current speed of the carriage.

Further, the wind correction value α is expressed by a quadratic expression in this example, and is given by the following expression.
α = (a · PG ^ 2 + b · PG + c) · (Tprt / Tref−1) · d (6)
Here, a, b, and c are constants, and d is an adjustment value for fine adjustment.
In this way, the delay value Dp is corrected by the wind correction value α given by the quadratic function, by the equations (5) and (6). The wind correction value α is corrected with (Tprt / Tref−1) and parameters a to c so that it becomes 0 (zero) in the constant speed process, minus in the acceleration process, and plus in the deceleration process.

  The quadratic expression (a · PG ^ 2 + b · PG + c) in the wind correction value α indicates the landing position deviation correction value Δx. This landing position deviation correction value Δx is expressed by a quadratic expression as shown in FIG. In the acceleration process, Δx = a1 · y ^ 2 + b1 · y + c1 (where a1> 0), and the correction value Δx is almost zero when the gap PG is the minimum value PG1 in the use range. It becomes larger in a curved line. On the other hand, in the deceleration process, Δx = a2 · y ^ 2 + b2 · y + c2 (where a2 <0), and the correction value Δx is almost zero when the gap PG is the minimum value PG1 in the use range, and the gap PG becomes larger. It becomes small in a quadratic curve.

  Next, the wind correction value α will be described with reference to FIGS. 14 and 15 show the wind correction value α using the quadratic expression for the acceleration process and the quadratic expression for the deceleration process shown in FIG. The horizontal axis of the graph is the carriage speed Vcr, and the vertical axis is the wind correction value α. However, the wind correction value α is indicated by a shift amount (μm) corresponding to the delay value correction amount. 14 is a wind correction value α when the minimum value PG1 (1.3 mm) in the use range, and the graph of FIG. 15 is a wind correction value when the maximum value PG6 (4.3 mm) is in the use range. α is shown.

  As shown in the graph of FIG. 14, the wind correction value α at PG1 takes a positive value in the acceleration process, and becomes smaller as the carriage speed Vcr becomes faster, and becomes 0 (zero) when reaching the constant speed Vc. . Further, in the deceleration process, the wind correction value α takes a negative value and increases as the carriage speed Vcr increases, and becomes 0 (zero) when the constant speed Vc is reached. The wind correction value α in the acceleration process is extremely small at less than 10 μm when the delay value correction amount is expressed by the landing deviation correction amount.

  Further, as shown in the graph of FIG. 15, the wind correction value α for PG6 takes a positive value (0 to 600 μm in the example in the figure) in the acceleration process, and becomes smaller as the carriage speed Vcr increases. When the speed Vc is reached, it becomes 0 (zero). In the deceleration process, the wind correction value α takes a negative value (−700 to 0 μm in the example in the figure), and increases as the carriage speed Vcr increases, and becomes 0 (zero) when the constant speed Vc is reached.

Assuming that the wind correction value α1 in the acceleration process and the wind correction value α2 in the deceleration process are used, the delay values Dpa, Dpc, Dpb in the acceleration process, constant speed process, and deceleration process are given by the following equations.
Dpa = PG / Vm · (1 / Tref−1 / Tprt) + α1 (7)
However, α1 = (a1 · PG ^ 2 + b1 · PG + c1) · (Tprt / Tref−1) · d (8)
Dpc = PG / Vm · (1 / Tref−1 / Tprt) (9)
Dpb = PG / Vm · (1 / Tref−1 / Tprt) + α2 (10)
However, α2 = (a2 · PG ^ 2 + b2 · PG + c2) · (Tprt / Tref−1) · d (11)
In the constant speed process, the above (based on the gap PG between the ejection head 27 and the medium P and (1 / Tprt) corresponding to the carriage speed Vcr, which is the current relative speed between the ejection head 27 and the medium P, is The discharge timing defined by PG / Vm · (1 / Tref−1 / Tprt) in the equation 9) corresponds to an example of “first discharge timing”. In the acceleration process, the term PG / Vm · (1 / Tref−1 / Tprt) in the equation (7) based on the current relative speed (1 / Tprt) corresponding to the carriage speed Vcr and the gap PG. The discharge timing delayed by “wind correction value α1 (> 0)” with respect to the “first discharge timing” defined by the above corresponds to an example of “second discharge timing”. In the deceleration process, the term PG / Vm · (1 / Tref−1 / Tprt) in the above equation (10) based on the current relative speed (1 / Tprt) corresponding to the carriage speed Vcr and the gap PG. The discharge timing that is earlier than the “first discharge timing” defined by the “wind correction value α2 (<0)” corresponds to an example of the “second discharge timing”.

  Next, with reference to FIG. 17, the simulation result of the landing position when the discharge control based on the delay value Dp corrected using the wind correction value α shown in FIG. 15 is performed will be described. In the graph shown in FIG. 17, the vertical axis represents the gap PG (μm) and the horizontal axis represents the landing position Px (mm). The landing position Px is indicated by a relative position in which the X-direction position of the nozzle at the start of discharge is the origin and the X-direction is the plus direction. Since the wind correction value α = 0 in the constant speed process, the landing position Px takes a value shifted to the positive side as the gap PG increases, as in the case of no correction shown in FIG.

  In the acceleration process, the corrected delay value Dp, which is corrected by the amount corresponding to the wind correction value α (> 0), is discharged with a delay corresponding to the wind correction value α as compared to the case without correction shown in FIG. . Therefore, the landing position Px in the acceleration process is shifted to the carriage traveling direction side (right side in the graph) by an amount corresponding to the wind correction value α, compared to the case without correction (one-dot chain line in FIG. 17). A value approximating the landing position in the constant speed process is taken in the entire range (1.2 to 4.3 mm).

  In the deceleration process, the corrected delay value Dp, which is corrected to be smaller by the wind correction value α (<0), discharges earlier by the wind correction value α than in the case of no correction shown in FIG. Is done. For this reason, the landing position Px in the deceleration process is shifted to the side opposite to the carriage traveling direction (left side in the graph) by an amount corresponding to the wind correction value α, compared to the case without correction (two-dot chain line in FIG. 17). In the entire use range (1.2 to 4.3 mm), a value approximating the landing position in the constant speed process is taken.

  Therefore, in all the gaps PG1 to PG6, the landing position Px falls within an allowable range (for example, 100 μm or less) in all of the acceleration process, the constant speed process, and the deceleration process. FIG. 16 is a graph comparing the landing deviation (μm) for each gap between the comparative example without wind correction and the example with wind correction. The graph of FIG. 16A shows landing deviation of the comparative example, and the graph of FIG. 16B shows landing deviation of the example. In FIG. 16A, as the gap PG increases in both the acceleration process and the deceleration process, the landing deviation with respect to the landing position in the constant speed process increases. However, by adopting the wind correction, the entire range of use of the gap PG is achieved. In both the acceleration process and the deceleration process, the landing deviation with respect to the landing position in the constant speed process falls within the allowable range.

Next, the operation of the printer 11 will be described.
When a print job is received, the controller 50 (specifically, an internal computer) executes a discharge control routine shown in FIG. In addition to the discharge control routine for controlling the discharge head 27, the controller 50 also performs a transport control routine for controlling the motors 30 and 31 of the transport system. By driving and controlling the motors 30 and 31 of the transport system, the medium P is fed and transported. When the medium P is conveyed to a predetermined printing start position, the controller 50 next controls the carriage motor 25 to move the carriage 22 in the scanning direction X. Then, printing for one pass is performed by ejecting ink droplets from the ejection head 27 while the carriage 22 is moving. Thereafter, a transport operation for transporting the medium P to the next printing position, and a print for performing printing for one pass by moving the carriage 22 in the scanning direction X and discharging ink droplets from the nozzles of the discharge head 27 during the movement. The operation is performed alternately. Then, every time the carriage 22 moves for printing, the controller 50 executes a discharge control routine shown in FIG. 18 and performs discharge control for discharging ink droplets from the nozzles 27b of the discharge head 27. When the carriage 22 moves in the scanning direction X, air flows into a space that is separated from the gap PG between the ejection head 27 and the medium P.

Hereinafter, the discharge control routine executed by the controller 50 will be described with reference to FIG.
First, in step S11, print conditions (print mode / medium type) are acquired. The print job received by the printer 11 includes print condition information such as a print mode and a medium type (paper type).

  In step S12, a gap PG corresponding to the printing conditions is acquired. The controller 50 calculates the gap PG based on one of the gaps PG1 to PG6 determined by the printing mode and the medium type and the thickness of the medium type. The reciprocal 1 / Tref of the reference period Tref corresponding to the period of the reference pulse signal RS when the carriage speed Vcr is a constant speed Vc determined from the print mode is sent to the correction unit 92 as reference speed data (Vc). .

  In step S13, the current carriage speed is acquired. The edge detection circuit 73 in the controller 50 detects the pulse edge of the A-phase / B-phase encoder pulse signal input from the linear encoder 29 and generates the reference pulse signal RS. The speed detection unit 91 (see FIG. 7) in the print timing generation circuit 74 measures (counts) the interval time between the pulse edges of the reference pulse signal RS, and acquires the cycle T (a count value proportional to the cycle T). In this example, the carriage speed Vcr is managed by the reciprocal of the cycle of the reference pulse signal RS. Therefore, the correction unit 92 in the controller 50 acquires the current carriage speed Vcr as the reciprocal 1 / Tprt of the period Tprt of the current reference pulse signal RS.

  In step S14, it is determined whether or not an acceleration process is in progress. From the current carriage speed and the position of the carriage in the scanning direction X1 (carriage position), it can be determined whether the process is an acceleration process, a constant speed process, or a deceleration process. If it is an acceleration process, it will progress to step S15, and if it is not an acceleration process, it will progress to step S17.

  In step S15, the delay value Dpa of the acceleration process is calculated. That is, the correction unit 92 in the controller 50 calculates the delay value Dpa of the acceleration process using the equations (7) and (8). As a result of the calculation, the second discharge timing delayed by the wind correction value α1 (> 0) from the first discharge timing defined by the term PG / Vm · (1 / Tref−1 / Tprt) in the equation (7). Is determined.

  In step S16, discharge control is performed based on the delay value Dpa. The discharge timing signal generation unit 94 reads the delay value Dpa from the delay value setting unit 93 and sets it in the delay counter 95. The delay counter 95 outputs a discharge timing signal PTS to the head drive circuit 54 when the count value is reduced to 0 (zero). As a result, in the acceleration process, ink droplets are ejected from the nozzles 27b at the second ejection timing based on the delay value Dpa.

  During this acceleration process, since it is determined in step S22 that printing has not ended, the processes in steps S13 to S16 are repeated. Thus, during the acceleration process, discharge control is performed at the second discharge timing based on the delay value Dpa of the acceleration process for each printing cycle (that is, for each discharge) in which one discharge is performed. When the acceleration process ends, the process proceeds to a constant speed process.

In step S17, it is determined whether or not a deceleration process is in progress. If it is not a deceleration process, that is, if it is a constant speed process, the process proceeds to step S18, and if it is a deceleration process, the process proceeds to step S20.
In step S18, the delay value Dpc of the constant speed process is calculated. That is, the correction unit 92 in the controller 50 calculates the delay value Dpc of the constant speed process using the equation (9). As a result of the calculation, a delay value Dpc that defines the first discharge timing defined by PG / Vm · (1 / Tref−1 / Tprt) expressed by the equation (9) is obtained.

  In step S19, discharge control is performed based on the delay value Dpc. The discharge timing signal generation unit 94 reads the delay value Dpc from the delay value setting unit 93 and sets it in the delay counter 95. The delay counter 95 outputs a discharge timing signal PTS to the head drive circuit 54 when the count value is reduced to 0 (zero). As a result, in the constant speed process, ink droplets are ejected from each nozzle 27b at the first ejection timing based on the delay value Dpc. During this constant speed process, since it is determined in step S22 that printing has not ended, the processes in steps S13, S14, and S17 to S19 are repeated. In this way, during the constant speed process, the discharge control is performed at the first discharge timing based on the delay value Dpc of the constant speed process for each printing cycle in which one discharge is performed (that is, for each discharge). When the constant speed process ends, the process proceeds to the deceleration process. In the deceleration process, since it is determined in step S17 that the process is a deceleration process, the process proceeds to step S20.

  In step S20, a delay value Dpb for the deceleration process is calculated. That is, the correction unit 92 in the controller 50 calculates the delay value Dpb of the deceleration process using the equations (10) and (11). As a result of the calculation, the second discharge timing is advanced by the wind correction value α2 (<0) from the first discharge timing defined by the term PG / Vm · (1 / Tref−1 / Tprt) in the equation (10). Is determined.

  In step S21, discharge control is performed based on the delay value Dpb. The discharge timing signal generation unit 94 reads the delay value Dpb from the delay value setting unit 93 and sets it in the delay counter 95. The delay counter 95 outputs a discharge timing signal PTS to the head drive circuit 54 when the count value is reduced to 0 (zero). As a result, in the deceleration process, ink droplets are ejected from each nozzle 27b at the second ejection timing based on the delay value Dpb. During this deceleration process, since it is determined in step S22 that printing has not ended, the processes in steps S13, S14, S17, S20, and S21 are repeated. Thus, during the deceleration process, the ejection control is performed at the second ejection timing based on the delay value Dpb in the deceleration process at every printing cycle in which one ejection is performed (that is, every ejection).

  From the above equations (7) to (11), when the influence of the wind is small (when the absolute values of the wind correction values α1 and α2 are small), the discharge timing (delay value Dp) is the slowest in the acceleration process. The deceleration process is intermediate and the constant speed process is fastest (Dpa> Dpb> Dpc). Further, when the influence of the wind is large (when the absolute values of the wind correction values α1 and α2 are large), the discharge timing (delay value Dp) is the slowest in the acceleration process, intermediate in the constant speed process, and most in the deceleration process. Faster (Dpa> Dpc> Dpb).

According to the first embodiment described in detail above, the following effects can be obtained.
(1) At the same carriage speed Vcr in the acceleration process and the deceleration process of the carriage 22, the discharge timing in the acceleration process is delayed from the discharge timing in the deceleration process. That is, at the same carriage speed Vcr, the discharge timing in the deceleration process is made earlier than the discharge timing in the acceleration process. For this reason, even if the ink droplets ejected in the acceleration process are caused to flow on the side opposite to the traveling direction of the carriage 22 (that is, the ejection head 27) by the air flow generated in the acceleration process of the carriage 22, Deviation from the target landing position can be kept small. Further, even when the ink droplets ejected in the deceleration process are caused to flow toward the traveling direction side of the carriage 22 by the air flow generated in the deceleration process of the carriage 22, the deviation of the ink droplets from the target landing position on the medium P is suppressed to be small. be able to.

  (2) In the acceleration process, based on the carriage speed Vcr (= 1 / Tprt) and the gap PG, the first discharge defined by the term PG / Vm · (1 / Tref−1 / Tprt) in the equation (7) The discharge head 27 is controlled to be discharged at the second discharge timing delayed by the wind correction value α1 (> 0) from the timing. Therefore, even when the ink droplets ejected in the acceleration process are caused to flow on the side opposite to the traveling direction of the carriage 22, the deviation of the landing positions of the ink droplets can be suppressed to a small value.

  (3) In the deceleration process, the first discharge defined by the term PG / Vm · (1 / Tref−1 / Tprt) in the equation (10) based on the carriage speed Vcr (= 1 / Tprt) and the gap PG. The ejection head 27 is controlled to be ejected at the second ejection timing that is earlier than the timing by the wind correction value α2 (<0). Therefore, even if the ink droplets ejected in the deceleration process are caused to flow toward the traveling direction of the carriage 22, the deviation of the landing positions of the ink droplets can be suppressed.

  (4) In the acceleration process, the second discharge timing is delayed more than the first discharge timing when the second gap is larger than the first gap than when the first gap is used. Therefore, even when the first gap is used for the second gap, the time during which the ink droplets ejected in the acceleration process are caused to flow in the direction opposite to the traveling direction of the carriage 22 is relatively longer than that for the first gap. Similarly, the deviation of the landing positions of the ink droplets can be suppressed small.

  (5) Particularly in the acceleration process, the degree of delaying the second discharge timing relative to the first discharge timing is increased as the gap PG is increased. Therefore, even when the time during which the ink droplets ejected in the acceleration process are caused to flow in the direction opposite to the traveling direction of the carriage 22 becomes relatively long when the gap is large, the displacement of the landing positions of the ink droplets is more effective. Can be kept small.

  (6) In the deceleration process, the second discharge timing is earlier than the first discharge timing when the second gap is larger than the first gap than when it is the first gap. Therefore, even in the second gap, in which the time during which the ink droplets ejected in the deceleration process are caused to flow in the traveling direction side of the carriage 22 is relatively longer than in the first gap, similarly to the first gap. In addition, it is possible to suppress the deviation of the landing position of the ink droplets.

  (7) Especially in the deceleration process, the greater the gap, the greater the degree to which the second discharge timing is advanced than the first discharge timing. Therefore, even when the time period for which the ink droplets ejected in the deceleration process are caused to flow toward the traveling direction of the carriage 22 becomes long when the gap is large, the deviation of the landing positions of the ink droplets can be suppressed more effectively. it can.

  (7) The degree to which the discharge timing is delayed with respect to the first discharge timing as the gap increases in the acceleration process and the deceleration process is set by a quadratic function with the gap as a variable. Therefore, when the gap is large in the acceleration process and the deceleration process, even if the time during which the ejected ink droplet is caused to flow in the direction opposite to the traveling direction of the carriage 22 or the traveling direction side becomes relatively long, the landing of the ink droplet The positional shift can be suppressed small. Moreover, since it is a quadratic function, the calculation processing burden when the controller 50 acquires the ejection timing can be reduced. Therefore, it is possible to cope with relatively high-speed discharge control.

  (8) Even in the acceleration process or the deceleration process, when the gap is as small as less than the threshold SG, the ejection head 27 is controlled at the first ejection timing. When the gap is smaller than the threshold SG, the discharge control at the first discharge timing defined by the same calculation formula based on the carriage speed Vcr and the gap PG is sufficient in the acceleration process, the constant speed process, and the deceleration process.

In addition, the said embodiment can also be changed into the following forms.
Even in the acceleration process or the deceleration process, when the gap is less than the threshold SG, the liquid ejection unit is controlled at the first ejection timing. However, even when the gap is less than the threshold SG, the liquid ejection unit is controlled at the second ejection timing. Thus, in the acceleration process or the deceleration process, the liquid discharge unit may be always controlled at the second discharge timing regardless of the gap value.

  ・ The larger the gap, the slower the second discharge timing than the first discharge timing is in the acceleration process, and the degree to which the second discharge timing is advanced in the deceleration process (the degree to which it is delayed). But you can. For example, it may be a function that becomes larger in a curve as the gap is larger. For example, a multidimensional function such as a cubic function or a quartic function may be used. Further, a trigonometric function, a function of a circle or an ellipse may be used. Even this type of function may be used in a range where the gap of the second discharge timing with respect to the first discharge timing becomes larger as the gap is larger in the use range of the gap.

The above function may be a linear function instead of a quadratic function.
-Instead of a quadratic function, a constant may be used when calculating the discharge timing. For example, when the ejection timing is determined by correcting to a larger gap when the second gap is larger than the first gap than when the first gap is used, the correction is performed when the second gap is larger than the first gap. The absolute value of the acceleration constant to be added in the acceleration process and the deceleration constant to be subtracted in the deceleration process are made larger.

  -Under the same relative speed, the larger the gap in the acceleration process, the greater the degree of delay of the second discharge timing relative to the first discharge timing based on the relative speed and gap during acceleration, and the larger the gap in the deceleration process The second discharge timing was made earlier than the first discharge timing based on the relative speed during deceleration and the gap. On the other hand, when the gaps are different but close to each other, the wind correction value α1 or α2 that determines the degree of delay of the second discharge timing with respect to the first discharge timing in each of the acceleration process and the deceleration process is set. The same value may be used. For example, when the gaps PG11 and PG12 are close values, the expressions (8) and (11) may be applied by regarding PG11 = PG12. Also, the function (a1 · PG ^ 2 + b1 · PG + c1) that defines the degree of delay in the equation (8) is replaced with a step function (step function) having two or more steps, or the degree of advancement in the equation (11) is defined. The function to be performed (a2 · PG ^ 2 + b2 · PG + c2) may be replaced with a step function having two or more steps. Even when the second discharge timing of the different gaps has the same degree of delay with respect to the first discharge timing, the second discharge timing is set to the first discharge timing within the use range of the gap. It is sufficient that there is at least one gap combination with different degrees of delay. For example, one set of at least one set of gaps having different degrees of delay is defined as a first gap and a second gap. In this case, in the acceleration process, when the gap is the second gap larger than the first gap, the degree of delay is increased and the second ejection timing is delayed more than the first ejection timing than when the gap is the first gap. Further, in the deceleration process, when the gap is the second gap larger than the first gap, the degree of advancement is increased and the second ejection timing is made earlier than the first ejection timing than when the gap is the first gap.

  Instead of the function, table data indicating a correspondence relationship between the gap and the delay value may be stored, and the corresponding delay value may be acquired by referring to the table data based on the gap at that time.

  Even in one of the acceleration process and the deceleration process, the discharge control may be performed at the second discharge timing in which the influence of the wind is corrected with respect to the first discharge timing based on the relative speed (carriage speed as an example) and the gap. Good. For example, if the second ejection timing is used only in the acceleration process, it is possible to suppress a deviation in the landing position of the liquid in the acceleration process. Further, for example, if the second discharge timing is used only in the deceleration process, it is possible to suppress a deviation in the landing position of the liquid in the deceleration process.

  In the above-described embodiment, the present invention is applied to a serial printer, but any scanning printing apparatus that performs printing while moving a carriage (or recording head) may be used. For example, the carriage may be in two directions, a main scanning direction and a sub-scanning direction. It may be applied to a movable lateral printer.

  -You may apply to the line printer provided with the line head. In the case of a line printer, the medium P as an example of the discharge target object moves in the transport direction by a transport mechanism such as a transport belt or a transport roller, so that the discharge head and the discharge target object move relative to each other. Then, the discharge timing at the same speed (relative speed) in the acceleration process and the deceleration process in the relative movement process of the liquid discharge unit (for example, the line head) and the discharge target (for example, the medium) is determined from the discharge timing in the acceleration process. Alternatively, the control unit may perform control to delay the discharge timing in the deceleration process. In this case, for example, even if an air flow (wind) is generated in the acceleration / deceleration process when the discharge target object moves, the deviation of the landing position due to the wind of the discharged liquid can be suppressed small. Note that a liquid discharge apparatus in which both of the liquid discharge unit and the discharge target object move relative to each other may be used. Even in this type of liquid ejecting apparatus, since an air flow is generated during the acceleration / deceleration process of the relative movement process, it is possible to suppress the deviation of the landing position of the liquid by controlling the ejection timing.

  Each functional unit constructed in the print control unit 81 and the print timing generation circuit 74 of the printer is realized by software by a computer executing a program, for example, an FPGA (field-programmable gate array) or an ASIC (Application Specific). It may be realized in hardware by an electronic circuit such as an IC) or may be realized by cooperation between software and hardware.

  -The medium that is an example of the discharge target is not limited to paper, but is a resin film or sheet, a resin-metal composite film (laminate film), woven fabric, non-woven fabric, metal foil, metal film, ceramic sheet, etc. There may be. Moreover, not only flat things, such as a paper and a sheet | seat, but the solid thing which has predetermined shapes, such as a cylinder, a cone, and a polygonal pyramid, may be sufficient.

  The liquid ejecting apparatus is not limited to a printing apparatus that performs printing on a medium, but may be a liquid ejecting apparatus that forms a three-dimensional solid object by ejecting resin droplets onto an ejected object using a liquid ejecting method (for example, an ink jet method). In this case, the three-dimensional solid object or the molding intermediate object constitutes an example of the discharge object. Even in such a liquid ejecting apparatus, by correcting the ejection timing, for example, it is possible to increase the accuracy of the liquid landing position while avoiding the influence of wind, and thus a highly accurate three-dimensional object can be formed.

  DESCRIPTION OF SYMBOLS 11 ... Printer as an example of a liquid discharge apparatus, 22 ... Carriage which comprises an example of a liquid discharge part, 27 ... Discharge head which comprises an example of a liquid discharge part, 27a ... Nozzle opening surface, 27b ... Nozzle, 40 ... Discharge part, 50: Controller as an example of a control unit, 92: Correction unit, PD: Print data, P: Medium as an example of an ejection target, X1: Scanning direction, F1: Transport direction, N: Nozzle array, PG ... Gap, Vcr: carriage speed as an example of relative speed, y: distance, Vair: wind speed.

Claims (11)

A liquid ejection device that ejects liquid onto an ejection object,
A liquid discharger capable of discharging liquid;
A control unit for controlling the discharge timing of discharging the liquid from the liquid discharge unit,
The controller controls the discharge timing in the acceleration process to the discharge timing in the deceleration process when the relative speed at which the liquid discharge unit and the discharge target object move relative to each other is the same speed in the acceleration process and the deceleration process. A liquid ejecting apparatus characterized by being delayed more than that. In the constant speed process, the control unit is configured to perform the first discharge timing based on a relative speed at a constant speed between the liquid discharge unit and the discharge target and a gap between the liquid discharge unit and the discharge target. Control discharge of the liquid discharge part,
2. The liquid ejection apparatus according to claim 1, wherein in the acceleration process, the liquid ejection unit is controlled to be ejected at a second ejection timing that is delayed from a first ejection timing based on a relative speed and a gap during acceleration. In the constant speed process, the control unit is configured to perform the first discharge timing based on a relative speed at a constant speed between the liquid discharge unit and the discharge target and a gap between the liquid discharge unit and the discharge target. Control discharge of the liquid discharge part,
3. The liquid ejection according to claim 1, wherein in the deceleration process, the liquid ejection unit is controlled to be ejected at a second ejection timing that is earlier than the first ejection timing based on a relative speed and a gap at the time of deceleration. apparatus.   In the acceleration process, the control unit delays the second discharge timing from the first discharge timing when the gap is a second gap larger than the first gap than when the gap is the first gap. The liquid ejecting apparatus according to claim 2, wherein the liquid ejecting apparatus is a liquid ejecting apparatus.   3. The liquid ejection apparatus according to claim 2, wherein the controller increases the degree of delaying the second ejection timing with respect to the first ejection timing as the gap increases in the acceleration process.   In the deceleration process, the control unit causes the second discharge timing to be earlier than the first discharge timing when the gap is a second gap larger than the first gap than when the gap is the first gap. The liquid ejecting apparatus according to claim 3, wherein the liquid ejecting apparatus is a liquid ejecting apparatus.   4. The liquid ejection apparatus according to claim 3, wherein the controller increases the degree of advancement of the second ejection timing with respect to the first ejection timing as the gap is larger in the deceleration process. 5.   In the acceleration process or the deceleration process, the degree to which the second discharge timing is delayed with respect to the first discharge timing as the gap is larger is set by a quadratic function using the gap as a variable. The liquid ejection apparatus according to claim 5 or 7.   9. The control unit according to claim 2, wherein the control unit controls the liquid discharge unit at the first discharge timing when the gap is less than a threshold value even in the acceleration process or the deceleration process. The liquid discharge apparatus according to any one of the above. A liquid discharge method for discharging a liquid onto a discharge object,
A first discharge step of discharging liquid from the liquid discharge unit in an acceleration process in which the liquid discharge unit and the discharge target object move relative to each other;
A second ejection step of ejecting liquid from the liquid ejection section in a constant speed process in which the liquid ejection section and the ejection object move relative to each other;
A third discharge step of discharging liquid from the liquid discharge unit in a deceleration process in which the liquid discharge unit and the discharge target object move relative to each other;
In the first discharge step and the third discharge step, the discharge timing when the relative speed of the relative movement of the liquid discharge unit and the discharge target is the same in the acceleration process and the deceleration process is the acceleration process. The liquid discharge method is characterized in that the discharge timing of the liquid is delayed from the discharge timing of the deceleration process. A liquid discharge method for discharging a liquid onto a discharge object,
A first discharge step of discharging liquid from the liquid discharge unit in an acceleration process in which the liquid discharge unit and the discharge target object move relative to each other;
A second ejection step of ejecting liquid from the liquid ejection section in a constant speed process in which the liquid ejection section and the ejection object move relative to each other;
In a deceleration process in which the liquid discharge unit and the discharge target are relatively moved, a third discharge step of discharging liquid from the liquid discharge unit,
In the constant speed process, the liquid discharge unit is discharged at a first discharge timing based on a relative speed at a constant speed between the liquid discharge unit and the discharge target and a gap between the liquid discharge unit and the discharge target. Control
In the acceleration process, the liquid discharge unit is controlled to be discharged at a second discharge timing delayed from the first discharge timing based on the relative speed and the gap at the time of acceleration,
In the deceleration process, the liquid ejection part is controlled to be ejected at a second ejection timing that is earlier than the first ejection timing based on a relative speed and a gap at the time of deceleration.