JP2009292017A - Delivery controlling device and delivery controlling method - Google Patents

Abstract

The image quality in the main scanning direction can be improved.
An ink jet printer includes a linear scale with reference marks at predetermined intervals, a head unit that can move in a main scanning direction and eject ink, and a control unit that performs ink ejection control. The head unit 7 is provided with an ink jet head 8 that ejects ink and a linear encoder 9 that detects a reference mark attached to the linear scale 5. When the linear encoder 9 detects the reference mark due to the movement of the head unit 7, the control unit 10 varies the delay time from the reference mark detection timing, determines the ejection timing for ejecting ink, and the inkjet head 8. Ink is discharged from Thereby, the deviation of the ink dots landed on the medium 3 can be made visually inconspicuous.
[Selection] Figure 1

Description

  The present invention relates to an ejection control device and an ejection control method for an inkjet printer that ejects ink from an inkjet head.

  In general, an ink jet printer reciprocates an ink jet head for ejecting ink in a main scanning direction to perform printing for one line on a medium placed on a platen, and then a conveyance direction orthogonal to the main scanning direction. The media is conveyed by one line in the (sub-scanning direction). The entire medium is printed by repeating the printing by the movement of the inkjet head and the conveyance of the medium.

  In this ink jet printer, a linear scale extending in the main scanning direction is fixed. The linear scale is provided with reference marks at predetermined intervals in order to indicate positions in the main scanning direction. On the other hand, a linear encoder that detects a linear scale is attached to the inkjet head that moves in the main scanning direction. The position of the inkjet head in the main scanning direction can be grasped by detecting the reference mark of the linear scale with a linear encoder (see, for example, Patent Document 1).

  However, because of the positional relationship between the position of the linear encoder and the position of the discharge nozzle that discharges ink and the processing time required for ink discharge control, the ink is discharged from the inkjet head after the reference mark is detected by the linear encoder. In the meantime, a predetermined delay time occurs.

Therefore, in the conventional ejection control device, when the linear encoder detects the reference mark of the linear scale when the inkjet head scans in the main scanning direction, the timing at which a predetermined delay time has elapsed is determined as the ink ejection timing. It was.
JP 2001-310456 A

  In practice, however, the moving speed of the ink jet head slightly varies due to vibrations of a motor that moves the ink jet head. For this reason, in the conventional ejection control device, the time between the detection of the reference mark and the ejection of the ink varies, so that the dot interval of the ink landed on the media varies locally, and the printed image There was a problem that printing stripes such as banding occurred.

  In practice, the dot diameter of ink landed on the medium varies depending on the nozzle diameter error of the inkjet head, the temperature of the ink, the ambient temperature, the type of the medium to be printed, and the like. For this reason, even if the moving speed of the inkjet head is constant, there is a problem that when the dot diameter is locally reduced, the printed image is locally thinned and print stripes such as banding occur.

  SUMMARY An advantage of some aspects of the invention is that it provides a discharge control apparatus and a discharge control method that can improve image quality in the main scanning direction.

  An ejection control apparatus according to the present invention is an ejection control apparatus for an inkjet printer that ejects ink from an inkjet head, and includes a reference position detection unit that detects a reference position for ejecting ink, and a reference position by the reference position detection unit. And a discharge timing determining means for determining the ink discharge timing by varying the delay time from the detection of the reference position to the discharge of ink every time the reference position is detected. .

  According to the ejection control device of the present invention, when the reference position detection unit detects the reference position, the ejection timing determination unit calculates the delay time from the detection of the reference position to the ejection of ink every time the reference position is detected. To determine the ink ejection timing. In other words, each time the reference position is detected, the discharge timing determination unit discharges the discharge timing so that the delay time from the detection of the reference position to the discharge of ink is not a fixed time (not uniform). To decide. In this way, by determining the ejection timing by intentionally changing the delay time, the dot interval of the ink that has landed on the medium becomes non-uniform in the main scanning direction, and the dot interval is locally non-uniform. Therefore, the deviation of the dot interval of the ink landed on the medium can be made visually inconspicuous. As a result, it is possible to prevent the occurrence of printing stripes such as banding due to a local dot interval shift, and to improve the image quality in the main scanning direction. In particular, when performing solid fill printing such as solid coating, print fringes such as banding tend to be noticeable, which is particularly effective.

  In this case, it is preferable that the ejection timing determination unit varies the delay time according to a random number value. According to this discharge control apparatus, since the delay time is changed based on the random number value, the delay time can be changed irregularly. For this reason, the dot interval of the ink landed on the medium can be irregularly changed.

  On the other hand, it is preferable that the discharge timing determining means varies the delay time in a wave shape having a predetermined frequency. According to this ejection control device, the delay time can be varied in a wave shape with a predetermined frequency, so that the dot interval of ink landed on the medium can be varied, and this dot interval can be adjusted by adjusting this frequency. Can be adjusted.

  In addition, it is preferable that the ejection timing determination unit adjusts the fluctuation range of the delay time according to the moving speed of the inkjet head. According to this discharge control apparatus, the discharge timing determination means adjusts the fluctuation range of the delay time according to the moving speed of the inkjet head. That is, when the moving speed of the ink jet head increases, the dot interval of ink that lands on the medium increases, and when the moving speed of the ink jet head decreases, the dot interval of the ink that lands on the medium decreases. For this reason, by adjusting the fluctuation range of the delay time according to the moving speed of the inkjet head, it is possible to obtain an appropriate ejection timing according to the dot interval of the ink that lands on the medium. For example, when increasing the moving speed of the inkjet head in order to prioritize throughput over image quality, the dot interval of the ink that lands on the media becomes wider, so the variation range of the delay time should be increased to determine the ejection timing Thus, it is possible to make the deviation of the dot interval more inconspicuous. On the other hand, if the moving speed of the inkjet head is slowed down in order to prioritize image quality over throughput, the interval between the ink dots that land on the media will be narrowed, so the variation range of the delay time should be reduced to determine the ejection timing. Thus, it is possible to make the dot interval shift inconspicuous and enable high-definition printing.

  In addition, it is preferable that the ejection timing determination unit adjusts the fluctuation range of the delay time according to at least one of the ink temperature, the ambient temperature, and the type of the medium to be printed. According to this discharge control apparatus, the discharge timing determination unit adjusts the fluctuation range of the delay time according to at least one of the ink temperature, the ambient temperature, and the type of the medium to be printed. That is, the dot diameter of the ink that lands on the medium varies depending on the temperature of the ink, the ambient temperature, and the type of the medium to be printed. For this reason, by adjusting the fluctuation range of the delay time according to at least one of the temperature of the ink, the ambient temperature, and the type of the medium to be printed, an appropriate ejection corresponding to the dot diameter of the ink that lands on the medium. Timing can be obtained. For example, if the dot diameter of the ink that lands on the media is large, the dot interval becomes narrow, and the local dot interval shift is less noticeable, so high-definition printing is possible by narrowing the fluctuation range of the delay time It can be. On the other hand, when the dot diameter of the ink that lands on the media is small, the dot interval becomes wide, and the deviation of the local dot interval tends to be conspicuous. Can be suppressed.

  The ink ejected from the inkjet head is an ultraviolet curable ink that is cured by the irradiation of ultraviolet rays, and the ejection timing determining means is responsive to the amount of ultraviolet radiation that irradiates the ultraviolet curable ink ejected from the inkjet head. The fluctuation range of the delay time may be adjusted.

  According to this discharge control apparatus, the discharge timing determination unit adjusts the fluctuation range of the delay time according to the amount of ultraviolet light irradiated to the ultraviolet curable ink discharged from the inkjet head. That is, since the ultraviolet curable ink is cured by irradiation with ultraviolet rays, the dot diameter of the ultraviolet curable ink changes according to the amount of ultraviolet rays. For this reason, by adjusting the fluctuation range of the delay time according to the amount of ultraviolet light, it is possible to obtain an appropriate ejection timing according to the dot diameter of the ultraviolet curable ink.

  An ejection control method according to the present invention is an ejection control method for an ink jet printer that ejects ink from an ink jet head, and includes a detection step for detecting a reference position for ejecting ink, and detection of a reference position by the detection step. An ejection timing determination step for determining an ejection timing for ejecting ink, and the ejection timing determination step varies a delay time from the detection of the reference position to the ejection of the ink every time the reference position is detected. Thus, the ejection timing is determined.

  According to the ejection control method of the present invention, when the reference position is detected in the detection step, the delay time from the detection of the reference position to the ejection of ink is varied for each detection of the reference position in the ejection timing determination step. Thus, the ink ejection timing is determined. That is, every time the reference position is detected, the ejection timing determination step is performed so that the delay time from the detection of the reference position to the ejection of ink is not a fixed time (so as to be non-uniform). To decide. In this way, by determining the ejection timing by intentionally changing the delay time, the dot interval of the ink that has landed on the medium becomes non-uniform in the main scanning direction, and the dot interval is locally non-uniform. Therefore, the deviation of the dot interval of the ink landed on the medium can be made visually inconspicuous. As a result, it is possible to prevent the occurrence of printing stripes such as banding due to a local dot interval shift, and to improve the image quality in the main scanning direction. In particular, when performing solid fill printing such as solid coating, print fringes such as banding tend to be noticeable, which is particularly effective.

  An ejection control program according to the present invention is an ejection control program for causing an inkjet printer that ejects ink from an inkjet head to execute a detection step of detecting a reference position for ejecting ink, and the detection step An ejection timing determination step for determining an ejection timing for ejecting ink based on detection of a reference position, and the ejection timing determination step includes a delay from the detection of the reference position to the ejection of the ink. The ejection timing is determined by varying the time for each detection of the reference position.

  According to the ejection control program according to the present invention, when the reference position is detected by the detection step, the delay time from the detection of the reference position to the ejection of the ink is changed every time the reference position is detected by the ejection timing determination step. Thus, the ink ejection timing is determined. That is, every time the reference position is detected, the ejection timing determination step is performed so that the delay time from the detection of the reference position to the ejection of ink is not a fixed time (so as to be non-uniform). To decide. In this way, by determining the ejection timing by intentionally changing the delay time, the dot interval of the ink that has landed on the medium becomes non-uniform in the main scanning direction, and the dot interval is locally non-uniform. Therefore, the deviation of the dot interval of the ink landed on the medium can be made visually inconspicuous. As a result, it is possible to prevent the occurrence of printing stripes such as banding due to a local dot interval shift, and to improve the image quality in the main scanning direction. In particular, when performing solid fill printing such as solid coating, print fringes such as banding tend to be noticeable, which is particularly effective.

  According to the present invention, the image quality in the main scanning direction can be improved.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a discharge control device and a discharge control method according to the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a plan view of an ink jet printer according to this embodiment, and FIG. 2 is a partially enlarged view of the ink jet printer shown in FIG. As shown in FIGS. 1 and 2, the ink jet printer 1 according to the present embodiment is an ink jet printer that prints a color image on a medium 3 conveyed on a platen 2.

  The ink jet printer 1 is provided with a transport roller 4 that transports the medium 3 placed on the platen 2 in the transport direction B. The transport roller 4 transports the media 3 in the transport direction B at a pitch of one line.

  In addition, the inkjet printer 1 is provided with a linear scale 5 that extends in the main scanning direction A perpendicular to the conveyance direction B of the medium 3 above the platen 2 (front side in FIG. 1). The linear scale 5 is formed in a long plate shape extending in the main scanning direction A. Reference marks M are attached to the linear scale 5 at predetermined intervals. The reference mark M is for indicating a position in the main scanning direction A. For this reason, the reference mark M may be provided at any interval as long as the position in the main scanning direction A is known.

  The ink jet printer 1 is provided with a guide rail 6 that extends in the main scanning direction A above the platen 2. The guide rail 6 is formed in a long plate shape extending in the main scanning direction A, and is arranged in parallel with the linear scale 5. A head unit 7 on which an ink jet head 8 that discharges ink is mounted is held on the guide rail 6 so as to be movable in the extending direction of the guide rail 6.

  The head unit 7 is provided with an ink jet head 8 and a linear encoder 9. The head unit 7 can be moved in a scanning direction A (leftward in FIGS. 1 and 2) and a direction opposite to the main scanning direction A (rightward in FIGS. 1 and 2) by a driving unit (not shown). Yes. The movement of the head unit 7 is realized, for example, by rotating a conveyor belt connected to the head unit 7 with a motor or the like. The rear end of the guide rail 6 in the main scanning direction A (the right end in FIGS. 1 and 2) is the standby position of the head unit 7.

  The inkjet head 8 prints an image on the medium 3 by ejecting ink. Although only the inkjet head 8 that discharges one color of ink is shown in the drawing, each inkjet head that discharges yellow Y, magenta M, cyan C, and black K inks is actually provided. The ink jet head 8 is connected to an ink tank (not shown) for storing ink. The ink can be ejected from the inkjet head 8 by supplying ink from the ink tank.

  The linear encoder 9 is a detector that detects the reference mark M attached to the linear scale 5. When detecting the reference mark M, the linear encoder 9 transmits an encoder signal. Since the head unit 7 and the linear scale 5 are arranged in parallel, the position in the main scanning direction A of the head unit 7 that moves in the main scanning direction A when the linear encoder 9 detects the reference mark M. Can be grasped.

  The inkjet printer 1 is provided with a control unit 10 that controls the transport roller 4, the head unit 7, and the inkjet head 8.

  The control unit 10 is connected to the transport roller 4, the head unit 7, the inkjet head 8, and the linear encoder 9. And the control part 10 controls the conveyance roller 4, the head unit 7, the inkjet head 8, etc. by transmitting an electrical signal to the conveyance roller 4, the head unit 7, the inkjet head 8, etc. FIG.

  FIG. 3 is a diagram illustrating a functional configuration example of the control unit. As shown in FIG. 3, the control unit 10 functions as a media conveyance control unit 11, a head unit movement control unit 12, a discharge control unit 13, a reference mark detection unit 14, and a discharge timing determination unit 15. In addition, the control part 10 is comprised mainly by the computer containing CPU, ROM, and RAM, for example. Each function described in FIG. 3 is realized by reading predetermined computer software on the CPU or RAM and operating it under the control of the CPU.

  The media transport control unit 11 controls the driving of the transport roller 4 and transports the media 3 placed on the platen 2 in the transport direction B at a pitch of one line for each scan.

  The head unit movement control unit 12 controls the driving of the head unit 7 and moves the head unit 7 in a main scanning direction A and a direction opposite to the main scanning direction A at a predetermined speed.

  The ejection control unit 13 controls ejection of the inkjet head 8 and ejects ink from the inkjet head 8.

  The reference mark detection unit 14 detects an encoder signal transmitted from the linear encoder 9. That is, the reference mark detection unit 14 recognizes the timing at which the linear encoder 9 detects the reference mark M by detecting this encoder signal.

  The ejection timing determination unit 15 determines the ejection timing for ejecting ink from the inkjet head 8 in order for the ejection control unit 13 to perform ejection control of the inkjet head 8. That is, the ejection timing determination unit 15 determines the ink ejection timing based on the detection timing of the encoder signal in the reference mark detection unit 14.

  FIG. 4 is a diagram showing the relationship between the encoder signal and the discharge timing, where (a) shows the linear scale, (b) shows the encoder signal, and (c) shows the delay time and the discharge timing. As shown in FIG. 4, when the linear encoder 9 detects the reference mark M and transmits an encoder signal, the reference mark detector 14 detects the encoder signal. Then, the ejection timing determination unit 15 calculates a delay time t from when the reference mark detection unit 14 detects the encoder signal until the ink is ejected, and determines the ejection timing Q.

  The delay time calculated by the discharge timing determination unit 15 varies every time an encoder signal is detected, as shown in FIGS. 5 and 6, for example.

  FIG. 5 shows a delay time calculated using a random value. In FIG. 5, P1 to P8 indicate detection timings P when the reference mark detection unit 14 detects the encoder signal, and Q1 to Q8 indicate discharge timings Q corresponding to P1 to P8. Further, t1 to t8 connecting P1 to P8 and Q1 to Q8 indicate the delay time t. In FIG. 5, the detection timings P <b> 1 to P <b> 8 are arranged in the detection order so that they are aligned on the time axis. In the case of FIG. 5, the discharge timing determination unit 15 first determines a reference delay time. The reference delay time is the minimum time of the delay time, and is the minimum time required from when the linear encoder 9 detects the reference mark M to when ink is ejected from the inkjet head 8. The ejection timing determination unit 15 generates a random value by a random number generator (not shown), and determines a value obtained by multiplying the random value by a predetermined coefficient as the delay times t1 to t8. And the discharge timing determination part 15 determines the timing which delay time t1-t8 passed from detection timing P1-P8 as discharge timing Q1-Q8.

  FIG. 6 shows a delay time calculated using a wave having a predetermined frequency. In FIG. 6, P11 to P18 indicate detection timings P at which the reference mark detection unit 14 detects the encoder signal, and Q11 to Q18 indicate discharge timings Q corresponding to P11 to P18. Further, t1 to t8 connecting P11 to P18 and Q11 to Q18 indicate the delay time t. In FIG. 6, the detection timings P <b> 11 to P <b> 18 are arranged in the detection order so that they are aligned on the time axis. In the case of FIG. 6, the discharge timing determination unit 15 first determines a reference delay time. This reference delay time is the same as the reference delay time defined in FIG. And the discharge timing determination part 15 produces | generates the noise (time) (alpha) of the predetermined frequency which amplitudes with a predetermined width with respect to elapsed time. Then, the ejection timing determination unit 15 determines values obtained by adding the value of the noise α corresponding to the time of the encoder signal to the reference delay time as delay times t11 to t18. And the discharge timing determination part 15 determines the timing which delay time t11-t18 passed from the detection timings P11-P18 as the discharge timings Q11-Q18.

  The fluctuation range of the delay time calculated by the ejection timing determination unit 15 includes, for example, the moving speed of the head unit 7 (the driving frequency of the head unit 7), the ink temperature, the temperature around the inkjet printer 1, and the medium 3 to be printed. It is set by various factors such as the type. Hereinafter, the setting of the fluctuation range of the delay time will be specifically described.

  When the moving speed of the head unit 7 is increased in order to prioritize the throughput over the image quality, since the dot interval of the ink that lands on the medium 3 becomes wider, the fluctuation range of the delay time is increased. On the other hand, when the moving speed of the head unit 7 is slowed down in order to prioritize the image quality over the throughput, the interval between the ink dots that land on the medium 3 becomes narrow, so the fluctuation range of the delay time is reduced.

  With respect to the ink temperature, the temperature around the inkjet printer 1, and the type of the medium 3 to be printed, the dot diameter of the ink that lands on the medium 3 varies as these conditions vary. For this reason, the dot diameter of the ink landed on the medium 3 is measured in advance according to the temperature of the ink, the temperature around the ink jet printer 1, and the type of the medium 3 to be printed. Thereafter, in the ink jet printer 1, when any of the ink temperature, the ambient temperature of the ink jet printer 1, and the type of the medium 3 to be printed is set manually or automatically, the measured value is used to land on the medium 3. The dot diameter of the ink to be calculated is calculated. When the calculated dot diameter is larger than the predetermined diameter, the interval between the dots of ink printed on the medium 3 is narrowed, and the deviation of the local dot interval is less noticeable. Reduce the width. On the other hand, when the calculated dot diameter is smaller than the predetermined diameter, the dot interval of the ink printed on the medium 3 becomes wide, and the deviation of the local dot interval becomes conspicuous. To widen.

  Next, the operation of the inkjet printer 1 according to the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing the processing operation of the control unit. The operation of the inkjet printer 1 described below is performed under the control of the control unit 10. That is, in the control unit 10, a processing unit (not shown) configured by a CPU or the like follows a program recorded in a storage device such as a ROM, the media transport control unit 11, the head unit movement control unit 12, and the ejection control unit 13. The following processing is performed by comprehensively managing functions such as the reference mark detection unit 14 and the discharge timing determination unit 15.

  The control unit 10 issues a command to transport the medium 3 placed on the platen 2 in the transport direction B by driving control of the transport roller 4, and the medium 3 starts printing at the initial printing position (printing starts when moving for each pass). When set to (position), print control described below is performed.

  First, the control unit 10 performs drive control of the head unit 7 and issues a command to the head unit 7 to move in the main scanning direction A at a predetermined speed (step S1). Then, the head unit 7 that has received this command moves in the main scanning direction A at a predetermined speed.

  And the control part 10 determines whether the reference mark M was detected in the linear encoder 9 (step S2). In step S <b> 2, determination is made based on whether or not the control unit 10 has received an encoder signal transmitted from the linear encoder 9. And when it determines with the reference mark M not being detected in the linear encoder 9 (step S2: NO), the control part 10 repeats determination of step S2.

  On the other hand, when it is determined that the reference mark M is detected in the linear encoder 9 (step S2: YES), the control unit 10 determines the ink ejection timing based on the detection of the reference mark M (step S3). In step S3, when the control unit 10 detects the encoder signal transmitted from the linear encoder 9, the control unit 10 varies the delay time from the detection of the encoder signal to the ejection of ink by a predetermined width every time the encoder signal is detected. To decide. And the control part 10 determines the timing which this determined delay time passed as discharge timing from the detection timing of an encoder signal.

  Next, the control unit 10 issues a command to eject ink to the inkjet head 8 at the ejection timing determined in step S3 (step S4). That is, in step S4, the control unit 10 performs discharge control of the ink jet head 8, and issues a command to the ink jet head 8 to discharge ink at the discharge timing determined in step S3. Then, the inkjet head 8 ejects ink at this ejection timing.

  Next, when the scanning of the same line is completed, the control unit 10 performs drive control of the head unit 7, moves the head unit 7 in the reverse direction of the main scanning direction A at a predetermined speed, and moves to the standby position. A command to return is issued (step S5). Then, the head unit 7 that has received this command moves in the reverse direction of the main scanning direction A and returns to the standby position.

  Next, the control unit 10 performs drive control of the transport roller 4 and issues a command so that the medium 3 is transported in the transport direction B for one line (step S6). Then, the transport roller 4 transports the medium 3 in the transport direction B for one line. Then, the medium 3 is set at the printing position of the next line.

  Next, the control unit 10 determines whether printing is completed (step S7). If it is determined in step S7 that printing has not been completed (step S7: NO), the control unit 10 returns to step S1 and repeats the above processing (steps S1 to S6) again. On the other hand, when it is determined in step S7 that printing is completed (step S7: YES), the control unit 10 ends the printing process.

  Thus, according to the present embodiment, when the linear encoder 9 detects the reference mark M of the linear scale 5 and the reference mark detection unit 14 detects the encoder signal, the ejection timing determination unit 15 detects the encoder signal. The ink discharge timing is determined by varying the delay time from the detection of ink until the ink is discharged every time the encoder signal is detected. That is, every time the encoder signal is detected by the reference mark detection unit 14, the ejection timing determination unit 15 makes the delay time from the detection of the encoder signal to the ejection of the ink not a fixed time (non-uniform) The discharge timing is determined. In this way, by determining the ejection timing by intentionally changing the delay time, in the main scanning direction A, the dot interval of the ink that has landed on the medium 3 becomes entirely non-uniform, and the dot interval is locally increased. Since unevenness can be prevented, the deviation of the dot interval of the ink that has landed on the medium 3 can be made visually inconspicuous. As a result, it is possible to prevent the occurrence of print stripes such as banding due to a local shift in the dot interval, and the image quality in the main scanning direction A can be improved. In particular, when performing solid fill printing such as solid coating, print fringes such as banding tend to be noticeable, which is particularly effective.

  In addition, according to the present embodiment, since the delay time varies based on the random number value, the delay time can be irregularly varied. For this reason, the dot interval of the ink landed on the medium 3 can be irregularly changed.

  In addition, according to the present embodiment, since the delay time can be changed based on the wavy noise α that increases or decreases at a predetermined frequency, the dot interval of the ink that has landed on the medium 3 can be changed, and the noise α This dot interval can be adjusted by adjusting the frequency of.

  Further, according to the present embodiment, the ejection timing determination unit 15 adjusts the fluctuation range of the delay time according to the moving speed of the head unit 7. That is, when the moving speed of the head unit 7 increases, the dot interval of ink that lands on the medium 3 increases, and when the moving speed of the head unit 7 decreases, the dot interval of ink that lands on the medium 3 decreases. For this reason, by adjusting the fluctuation range of the delay time according to the moving speed of the head unit 7, it is possible to obtain an appropriate ejection timing corresponding to the dot interval of the ink landed on the medium 3. When the moving speed of the head unit 7 is increased in order to prioritize the throughput over the image quality, since the dot interval of the ink that lands on the medium 3 becomes wider, the ejection timing is determined by increasing the fluctuation range of the delay time. By doing so, the shift of the dot interval can be made inconspicuous more effectively. On the other hand, when the moving speed of the head unit 7 is slowed down in order to prioritize the image quality over the throughput, since the dot interval of the ink that lands on the medium 3 becomes narrow, the fluctuation timing of the delay time is reduced to determine the ejection timing. By doing so, the deviation of the dot interval is made inconspicuous and high-definition printing can be performed.

  Further, according to the present embodiment, the ejection timing determination unit 15 adjusts the fluctuation range of the delay time according to at least one of the ink temperature, the ambient temperature, and the type of the medium 3 to be printed. That is, the dot diameter of the ink that lands on the medium 3 varies depending on the ink temperature, the ambient temperature, and the type of the medium to be printed. For this reason, by adjusting the fluctuation range of the delay time according to at least one of the temperature of the ink, the ambient temperature, and the type of the medium 3 to be printed, an appropriate amount corresponding to the dot diameter of the ink landed on the medium 3 can be obtained. A proper discharge timing can be obtained. When the dot diameter of the ink that lands on the medium 3 is large, the dot interval is narrowed, and the deviation of the local dot interval is difficult to notice. Therefore, by narrowing the fluctuation range of the delay time, high-definition printing can be performed. Can be possible. On the other hand, when the dot diameter of the ink that lands on the medium 3 is small, the dot interval becomes wide, and the deviation of the local dot interval is easily noticeable. Can be suppressed.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, the ink ejected by the inkjet printer 1 is not particularly limited, and may be, for example, a solvent, water-based, ultraviolet curable ink (UV ink), or the like.

  When the ultraviolet curable ink is ejected from the ink jet printer 1, it is preferable to adjust the fluctuation range of the delay time according to the amount of ultraviolet light irradiated to the ultraviolet curable ink ejected from the ink jet head 8. According to the inkjet printer 1, the ejection timing determination unit 15 adjusts the fluctuation range of the delay time according to the amount of ultraviolet rays irradiated to the ultraviolet curable ink ejected from the inkjet head 8. That is, since the ultraviolet curable ink is cured by irradiation with ultraviolet rays, the dot diameter of the ultraviolet curable ink changes according to the amount of ultraviolet rays. For this reason, by adjusting the fluctuation range of the delay time according to the amount of ultraviolet light, it is possible to obtain an appropriate ejection timing according to the dot diameter of the ultraviolet curable ink.

  In the above embodiment, the single-head type inkjet printer 1 in which one inkjet head 8 is mounted on the head unit 7 has been described. For example, as illustrated in FIG. The present invention may be applied to a multi-head type ink jet printer 21 on which the heads 8a and 8b are mounted. In this case, the ink jet head 8a and the ink jet head 8b are arranged at a predetermined distance in the main scanning direction A. For this reason, the reference delay time for determining the ejection timing of the inkjet head 8b is the reference delay time for determining the ejection timing of the inkjet head 8a, and the head unit 7 is between the inkjet head 8a and the inkjet head 8b. This is the time plus the travel time to move. In addition, when each inkjet head 8a, 8b has a plurality of ejection nozzles in the main scanning direction A, the reference delay time is calculated in consideration of the movement time of the head unit 7 between the ejection nozzles.

  In the above-described embodiment, it has been described that ink is ejected from the inkjet head 8 only when the head unit 7 moves in the main scanning direction A. However, when the head unit 7 moves in the direction opposite to the main scanning direction A. Alternatively, a bidirectional ejection method in which ink is ejected from the inkjet head 8 may be used.

  In the above-described embodiment, the inkjet printer 1 is provided with the conveyance roller 4 in order to convey the medium 3. However, the medium 3 may be conveyed by a mechanism other than the conveyance roller 4.

  In the above embodiment, the medium 3 and the head unit 7 are relatively moved in the transport direction B by transporting the medium 3 in the transport direction B. Alternatively, any of the head units 7 may be used, and both of them may be moved. For example, the present invention is applied to a flat bed type ink jet printer including a flat bed on which the medium 3 is placed and fixed, and a mechanism for moving the head unit 7 in the transport direction B and the direction opposite to the transport direction B. May be. Even in this flat bed type ink jet printer, since the ink is ejected when the head unit 7 is moved in the main scanning direction A or in the reverse direction of the main scanning direction A, the same effect as the ink jet printer 1 is obtained. be able to.

It is a top view of the ink jet printer concerning this embodiment. It is the elements on larger scale of the inkjet printer shown in FIG. It is the figure which showed the function structural example of the control part. It is the figure which showed the relationship between an encoder signal and discharge timing, (a) is a linear scale, (b) is an encoder signal, (c) has shown discharge timing, respectively. The delay time calculated using a random value is shown. The delay time calculated using the wave of a predetermined frequency is shown. It is a flowchart which shows the processing operation of a control part. It is the figure which showed the other structural example of the head unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 21 ... Inkjet printer, 3 ... Medium, 5 ... Linear scale, M ... Reference mark (reference position), 7 ... Head unit, 8 ... Inkjet head, 9 ... Linear encoder (reference position detection means), 10 ... Control part (Discharge control device), 14... Reference mark detector (reference position detector), 15.

Claims (8)

An inkjet printer ejection control device that ejects ink from an inkjet head,
Reference position detecting means for detecting a reference position for ejecting ink;
When the reference position is detected by the reference position detection means, an ejection timing for determining an ink ejection timing by varying a delay time from the detection of the reference position to the ejection of ink every time the reference position is detected. A determination means;
A discharge control device comprising:   The discharge control apparatus according to claim 1, wherein the discharge timing determination unit varies the delay time according to a random value.   The discharge control apparatus according to claim 1, wherein the discharge timing determining unit varies the delay time in a wave shape having a predetermined frequency.   The ejection control apparatus according to claim 1, wherein the ejection timing determination unit adjusts a fluctuation range of the delay time according to a moving speed of the inkjet head.   The discharge timing determination unit adjusts a fluctuation range of the delay time according to at least one of an ink temperature, an ambient temperature, and a type of a medium to be printed. The discharge control device according to claim 1. The ink ejected from the inkjet head is an ultraviolet curable ink that is cured by irradiation with ultraviolet rays,
The discharge timing determination unit adjusts the fluctuation range of the delay time according to the amount of ultraviolet light applied to the ultraviolet curable ink discharged from the inkjet head. The discharge control device according to claim 1. An inkjet printer ejection control method for ejecting ink from an inkjet head,
A detection step for detecting a reference position for ejecting ink;
An ejection timing determination step for determining an ejection timing for ejecting ink based on the detection of the reference position by the detection step;
The ejection timing determining step determines the ejection timing by varying a delay time from the detection of the reference position to the ejection of the ink every time the reference position is detected. . An ejection control program for causing an inkjet printer to eject ink from an inkjet head,
A detection step for detecting a reference position for ejecting ink;
An ejection timing determination step for determining an ejection timing for ejecting ink based on the detection of the reference position by the detection step;
In the ejection timing determination step, the ejection timing is determined by varying a delay time from the detection of the reference position to the ejection of the ink for each detection of the reference position. .

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