JP2022147107A - Printer, printing method, printing program, and recording medium - Google Patents

Abstract

To output a small drive signal to a drive element of a discharge head in an appropriate manner according to a relative speed of a printing medium for the discharge head.SOLUTION: When a transport speed V of a printing medium WP is in a low speed range Rvl, a discharge signal Sd is output to a piezoelectric element 55 (drive element) at a cycle Csl corresponding to the transport speed V, and a small drive signal Sm is not output to the piezoelectric element 55. When the transport speed V is in a medium speed range Rvm higher speed than the low speed range Rvl, the small drive signal Sm is output to the piezoelectric element 55 between the continuously output discharge signals Sd while the discharge signal Sd is output to the piezoelectric element 55 at a cycle Csm corresponding to the transport speed V. When the transport speed V is in a high speed range Rvh higher than the medium speed range Rvm, the discharge signal Sd is output to the piezoelectric element 55 at a cycle Csh corresponding to the transport speed V, and the small drive signal Sm is not output to the piezoelectric element 55.SELECTED DRAWING: Figure 7

Description

The present invention relates to ink jet technology for ejecting ink from nozzles communicating with pressure chambers by applying pressure fluctuations to ink stored in pressure chambers.

2. Description of the Related Art A printing apparatus is known that prints an image on a print medium by ejecting ink from nozzles of the ejection head while moving the print medium relative to the ejection head. In such a printing apparatus, ink is ejected at time intervals according to the relative speed of the print medium with respect to the ejection head. That is, by shortening the ink ejection interval as the relative speed of the print medium increases, the ink is accurately landed on the target position of the print medium.

This ejection head has pressure chambers that store ink and nozzles that communicate with the pressure chambers. Driving elements provided for the pressure chambers apply pressure fluctuations to the ink in the pressure chambers, thereby ejecting the ink from the nozzles. to dispense. As pointed out in Japanese Unexamined Patent Application Publication No. 2002-100001, in such an ejection head, the ink meniscus formed in the nozzles vibrates as the ink is ejected, and the vibrations attenuate with the lapse of time. In other words, residual vibration exists in the meniscus of the ink until a predetermined damping time elapses after the ink is ejected.

If the ink ejection interval is longer than the damping time of the residual vibration, the residual vibration is damped from one ink ejection to the next ink ejection. Therefore, ink can be ejected from the nozzles without being affected by residual vibration. On the other hand, if the ink ejection interval is shorter than the attenuation time of the residual vibration, the residual vibration does not decay from one ink ejection to the next ink ejection. Therefore, the residual vibration affects the pressure fluctuation applied to the ink in the pressure chamber for the next ink ejection. As a result, the ejection speed of the ink from the nozzles is significantly reduced, and the position where the ink lands on the print medium may be largely misaligned.

That is, when the relative speed of the print medium is relatively low, the ink ejection interval is long, so there is no effect of residual vibration. On the other hand, when the relative speed of the print medium is relatively high, the ink ejection interval is shortened, resulting in the influence of residual vibration. Therefore, in Patent Document 1, when the relative speed of the print medium becomes higher than a predetermined value, a minute signal (fine drive signal) is output to the drive element following ink ejection, and the pressure chamber is moved according to the fine drive signal. Residual vibration is suppressed by the generated ink pressure fluctuation.

JP 2001-277484 A

However, as will be described in detail later, when the relative speed of the print medium increases further, it is not necessarily appropriate to output a fine drive signal to the drive element following ejection of ink to vary the pressure of the ink in the pressure chamber. Sometimes it wasn't.

The present invention has been made in view of the above problems, and fine driving is performed in an appropriate manner according to the relative speed of the print medium with respect to the ejection head that ejects ink from nozzles by applying pressure fluctuations to ink in the pressure chambers with a drive element. The object is to allow a signal to be output to the drive element.

A printing apparatus according to the present invention includes an ejection head having pressure chambers that store ink, nozzles that communicate with the pressure chambers, and drive elements that apply pressure fluctuations to the ink in the pressure chambers, and ejects a print medium facing the nozzles. A drive unit that moves relative to the head, an ejection signal that applies pressure fluctuations to the ink in the pressure chambers to cause ink to be ejected from the nozzles, and a fine drive signal that applies pressure fluctuations to the ink in the pressure chambers to prevent ink from being ejected from the nozzles. to the driving element, and the control unit drives the ejection signal at time intervals according to the relative velocity when the relative velocity between the print medium and the ejection head is within the first velocity range. When the relative speed is in the second speed range higher than the first speed range, the ejection signal is output to the drive element at time intervals corresponding to the relative speed. while outputting a fine drive signal to the drive element between ejection signals that are continuously output, and if the relative speed is in a third speed range higher than the second speed range, While the ejection signal is output to the drive element at regular time intervals, the fine drive signal is not output to the drive element.

In the printing method according to the present invention, ink is ejected onto a print medium from nozzles of an ejection head that has pressure chambers that store ink, nozzles that communicate with the pressure chambers, and drive elements that apply pressure fluctuations to the ink in the pressure chambers. In this printing method, while the print medium is moved relative to the ejection head at a relative speed within a first speed range, an ejection signal that gives pressure fluctuations for ejecting ink from the nozzles to the ink in the pressure chamber is changed to the relative speed. a step of outputting to the driving element at corresponding time intervals; and moving the print medium relative to the ejection head at a relative speed in a second speed range higher than the first speed range, while performing a time interval corresponding to the relative speed. a step of outputting an ejection signal to the drive element and outputting a fine drive signal to the drive element between the successively output ejection signals to give pressure fluctuations to the ink in the pressure chamber so as not to eject ink from the nozzle; and outputting an ejection signal to the drive element at time intervals according to the relative velocity while moving the print medium relative to the ejection head at a relative velocity in a third velocity range higher than the second velocity range. , in the step of moving the print medium at the relative speed in the first speed range and the step of transporting the print medium at the relative speed in the third speed range, no fine drive signal is output to the drive element.

A printing program according to the present invention is a printing program for supplying ink onto a printing medium from nozzles of an ejection head having pressure chambers that store ink, nozzles that communicate with the pressure chambers, and drive elements that apply pressure fluctuations to the ink in the pressure chambers. In a printing program that causes a computer to control ejection, the print medium is moved relative to the ejection head at a relative speed within a first speed range, and pressure fluctuations for ejecting ink from the nozzles are applied to the ink in the pressure chambers. outputting a signal to the drive element at time intervals according to the relative speed; An ejection signal is output to the drive element at time intervals corresponding to the speed, and a fine drive signal is applied to the ink in the pressure chamber so that the ink in the pressure chamber does not eject ink from the nozzle. and outputting an ejection signal to the drive element at time intervals according to the relative speed while moving the print medium relative to the ejection head at a relative speed in a third speed range higher than the second speed range. and outputting a fine drive signal to the drive element in the step of moving the print medium at a relative speed within the first speed range and the step of transporting the print medium at a relative speed within the third speed range. does not output

A recording medium according to the present invention records the above printing program so that it can be read by a computer.

The present invention (printing device, printing method, printing program, and recording medium) configured as described above provides a time interval corresponding to the relative speed when the relative speed between the printing medium and the ejection head is within the first speed range. , the ejection signal is output to the driving element, while the fine driving signal is not output to the driving element. As a result, when the relative speed of the print medium is low and there is no influence of residual vibration, ink can be properly ejected from the nozzles by not outputting the fine drive signal to the drive element. Further, when the relative speed is in the second speed range higher than the first speed range, while the ejection signals are output to the driving element at time intervals according to the relative speed, to output a fine drive signal to the drive element. As a result, when the relative speed of the print medium increases and the effect of residual vibration begins to appear, a fine drive signal is output to the drive element, thereby suppressing the effect of residual vibration and ejecting ink from the nozzles. It can be discharged properly. Furthermore, when the relative speed is in the third speed range higher than the second speed range, the ejection signal is output to the drive element at time intervals according to the relative speed, while the fine drive signal is not output to the drive element. Accordingly, when the relative speed of the print medium is further increased, ink can be appropriately ejected from the nozzles by not outputting the fine drive signal to the drive element. As a result, it is possible to output the fine drive signal to the drive element in an appropriate manner according to the relative speed of the print medium with respect to the ejection head.

The control unit further includes a detection unit that detects ink that has landed on the print medium. The printing apparatus may be configured to perform a condition determination operation for determining conditions for outputting the fine drive signal to the drive element based on the detection result. This makes it possible to optimize the conditions for outputting the fine drive signal to the drive element.

For example, in the test printing operation, while the fine drive signal is not output to the drive element, the drive unit changes the relative speed and outputs the ejection signal to the drive element at time intervals according to the relative speed to print the test image. In the condition determination operation, the printing apparatus may be configured to determine the first speed range, the second speed range, and the third speed range based on the result of detection of the test image by the detection unit. This makes it possible to optimize the first and third speed ranges in which the fine drive signal should not be output to the drive element and the second speed range in which the fine drive signal should be output to the drive element.

In the test printing operation, while the print medium is moved with respect to the ejection head at a relative speed within the second speed range, ejection signals are output to the drive elements at time intervals corresponding to the relative speed. Next, while changing the timing of outputting the fine drive signal, the fine drive signal is output at the timing, the test image is printed on the printing medium, and the condition determination operation is based on the result of detecting the test image by the detection unit. Alternatively, the printing apparatus may be configured to determine the timing of outputting the fine drive signal following the ejection signal. This makes it possible to optimize the timing of outputting the fine drive signal to the driving element following the ejection signal.

In the test printing operation, the print medium is moved with respect to the ejection head at a relative speed within the second speed range, and ejection signals are output to the drive elements at time intervals corresponding to the relative speed. While changing the amplitude of the fine drive signal output by the step of printing a test image on a print medium, in the condition determination operation, the amplitude of the fine drive signal is determined based on the result of detection of the test image by the detection unit, A printing device may be configured. This makes it possible to optimize the amplitude of the fine drive signal.

As described above, according to the present invention, the fine drive signal is generated in an appropriate manner according to the relative speed of the print medium with respect to the ejection head that ejects ink from the nozzles by applying pressure fluctuations to the ink in the pressure chambers using the drive elements. It becomes possible to output to the driving element.

1 is a front view schematically showing a printing system equipped with an example of a printing apparatus according to the present invention; FIG. FIG. 2 is a partial cross-sectional view schematically showing the configuration of an ejection head; FIG. 2 is a block diagram showing an electrical configuration included in the printing apparatus of FIG. 1; 4A and 4B are diagrams schematically showing waveforms of ejection signals output to piezoelectric elements of the ejection head; FIG. FIG. 4 is a diagram schematically showing residual vibrations that occur as ink is output in response to an ejection signal; FIG. 4 is a diagram schematically showing an example of temporal changes in the conveying speed of a print medium; FIG. 4 is a diagram schematically showing an example of control according to a speed region to which the transport speed of the print medium belongs; 4 is a flowchart showing an example of processing for determining a target speed region for outputting a fine drive signal; 4 is a flowchart showing an example of processing for determining the timing of outputting a fine drive signal; 4 is a flowchart showing an example of processing for determining the amplitude of the fine drive signal;

FIG. 1 is a front view schematically showing a printing system 100 equipped with an example of a printing apparatus according to the invention. In FIG. 1 and the figures shown below, in order to clarify the arrangement relationship of each part of the apparatus, the X direction, which is the horizontal direction in which the paper feeding unit 1, the printing device 3, and the paper discharging unit 4 constituting the printing system 100 are arranged, The Y direction, which is a horizontal direction perpendicular to the X direction, is shown as appropriate.

A printing system 100 according to this embodiment includes a paper feeding unit 1 , a printing device 3 , and a paper discharging unit 4 . The paper feeding unit 1 holds a roll of continuous paper WP rotatably around a horizontal axis. The paper feeding unit 1 unwinds and supplies the printing medium WP made of continuous paper to the printing device 3 . The printing device 3 performs printing by ejecting ink onto the print medium WP to form an image, and delivers the print medium WP to the paper discharge section 4 . The paper discharge unit 4 winds the print medium WP printed by the printing device 3 around the horizontal axis.

Here, the direction in which the print medium WP, which is continuous paper, is sent out and transported by the paper feeding unit 1 is defined as the transport direction X. As shown in FIG. A horizontal direction orthogonal to the transport direction X is defined as a width direction Y. As shown in FIG. The paper feeding unit 1 described above is arranged on the upstream side of the printing device 3 in the transport direction X. As shown in FIG. The above-described paper discharge section 4 is arranged on the downstream side of the printing device 3 in the transport direction X. As shown in FIG.

Note that the above-described print medium WP made of continuous paper corresponds to the "print medium" in the present invention.

The printing device 3 has a drive roller 7 on the upstream side for taking in the print medium WP from the paper feeding unit 1 . The print medium WP taken in from the paper feeding unit 1 by the drive roller 7 is sent in the transport direction X by a plurality of transport rollers 9 and transported toward the paper discharge unit 4 on the downstream side. A driving roller 11 is arranged between the most downstream conveying roller 9 and the paper discharge section 4 . The driving roller 11 sends out the print medium WP conveyed on the conveying roller 9 toward the paper discharge section 4 .

The printing device 3 includes a printing unit 13 , a drying unit 15 , and a line scanner 17 in this order along the transport direction X from the upstream side between the drive roller 7 and the drive roller 11 . The printing unit 13 prints on the print medium WP. The drying unit 15 dries the print medium WP printed by the printing unit 13 . The line scanner 17 inspects whether or not the printed portion of the print medium WP is stained or missing.

The printing unit 13 includes an ejection head 5 having a plurality of nozzles for ejecting ink onto the print medium WP. A plurality of printing units 13 are generally arranged along the transport direction X of the print medium WP. For example, a total of four printing units 13 for black (K), cyan (C), magenta (M), and yellow (Y) are provided. However, in the following description, a configuration in which the printing device 3 includes only one printing unit 13 will be described as an example. In addition, the printing unit 13 has a length that exceeds the width of the print medium WP in the width direction Y of the print medium WP. The printing unit 13 includes an ejection head 5 that can print a print area in the width direction of the print medium WP without moving in the width direction Y. As shown in FIG.

FIG. 2 is a partial cross-sectional view schematically showing the configuration of the ejection head. As described above, the printing unit 13 has a plurality of ejection heads 5, and each ejection head 5 ejects ink using an inkjet method. As shown in FIG. 2, the ejection head 5 has a housing 51 and a plurality of nozzles 52 arranged in a predetermined direction at the bottom of the housing 51. Each of the plurality of nozzles 52 opens downward. A plurality of cavities 53 communicating with the plurality of nozzles 52 and an ink supply chamber 54 communicating with the plurality of cavities 53 are provided inside the housing 51 . Further, an inlet 511 and an outlet 512 communicating with the ink supply chamber 54 are opened in the housing 51, and ink supplied from the inlet 511 to the ink supply chamber 54 by an ink circulation mechanism (not shown) flows. The ink is cyclically supplied to the ink supply chamber 54 by being collected from the outlet 512 . Ink is supplied to each cavity 53 from the ink supply chamber 54 .

A piezoelectric element 55 is provided for each of the plurality of cavities 53 . The piezoelectric element 55 is, for example, a piezoelectric element, and deforms according to an applied electrical signal. The pressure of the ink inside the cavity 53 fluctuates according to the deformation of the piezoelectric element 55 . As will be described later, the piezoelectric element 55 is applied with an ejection signal and a fine drive signal, which are electric signals different from each other. When the ejection signal is applied to the piezoelectric element 55 , the piezoelectric element 55 gives the ink in the cavity 53 pressure fluctuation (ejection pressure fluctuation) required for ejecting ink from the nozzle 52 . On the other hand, when the fine drive signal is applied to the piezoelectric element 55 , the piezoelectric element 55 applies pressure fluctuation (fine drive pressure fluctuation) to the ink in the cavity 53 to such an extent that ink is not ejected from the nozzle 52 .

FIG. 3 is a block diagram showing the electrical configuration of the printer 3 of FIG. 1. As shown in FIG. As shown in FIG. 3, the printing apparatus 3 has a transport motor 341 that drives the driving roller 7 to transport the print medium WP, and the rotational position of the transport motor 341 (in other words, the transport position of the print medium WP). and an encoder 342 for detecting. The transport motor 341 is a servomotor that rotates the drive roller 7 . The printing device 3 also includes a line scanner 17 (line camera). The line scanner 17 is arranged perpendicular to the transport direction of the print medium WP, and passes through an imaging position between the drying unit 15 and the discharge unit 4, which is located downstream of the printing unit 13, for example. An image printed on the recording surface of the print medium WP is captured.

Further, the printing device 3 includes a control unit 39 that controls the entire device. The control unit 39 includes an arithmetic unit 391 configured by a processor such as a CPU (Central Processing Unit) and a storage unit 392 configured by a storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). have. The computing unit 391 controls the conveying motor 341 , the encoder 342 , the line scanner 17 and the piezoelectric elements 55 , and the storage unit 392 stores a print program 393 executed by the computing unit 391 . This print program 393 is provided, for example, by a recording medium 399 provided separately from the control unit 39 . This recording medium 399 records the print program 393 so that it can be read by the computer (control unit 39). Such a recording medium 399 includes, for example, a USB (Universal Serial Bus) memory, a memory card, or a storage device of an external server computer. The print program 393 defines the content of control executed by the control unit 39 . Next, control executed by the calculation unit 391 according to the print program 393 will be described.

FIG. 4 is a diagram schematically showing the waveform of the ejection signal output to the piezoelectric element of the ejection head. In FIG. 4, the horizontal axis represents time, and the vertical axis represents voltage. As shown in FIG. 4, the ejection signal Sd is a voltage signal with an amplitude Ad whose voltage changes with the lapse of time. The pressure applied to the ink in the cavity 53 is varied according to the change in the voltage indicated by . This pressure fluctuation causes ink to be ejected from the nozzle 52 communicating with the cavity 53 . The ejection signal Sd is periodically output according to the transport speed of the print medium WP.

Specifically, the calculation unit 391 calculates the speed at which the print medium WP is transported based on the transport position of the print medium WP detected by the encoder 342 . The calculation unit 391 determines the cycle Cs (that is, the time interval) for outputting the ejection signal Sd to the piezoelectric element 55 based on the transport speed of the printing medium WP thus calculated. In other words, in order to cause ink to land on the print medium WP with a constant resolution regardless of the transport speed of the print medium WP, it is necessary to adjust the cycle Cs for outputting the ejection signal Sd according to the transport speed of the print medium WP. . Specifically, the calculation unit 391 shortens the cycle Cs of the ejection signal Sd as the transport speed of the print medium WP increases, and shortens the cycle Cs of the ejection signal Sd as the transport speed of the print medium WP decreases. Lengthen the period Cs. That is, the period Cs is inversely proportional to the conveying speed V.

FIG. 5 is a diagram schematically showing residual vibration that occurs as ink is output in response to an ejection signal. In FIG. 5, the horizontal axis represents time, and the vertical axis represents meniscus pressure. When the ink is ejected from the nozzle 52, the meniscus of the ink formed at the nozzle 52 vibrates. The residual vibration of the meniscus generated with ink ejection is attenuated with the lapse of time. Therefore, if the cycle Cs of the ejection signal Sd is longer than the attenuation time of the residual vibration, the residual meniscus vibration does not affect ink ejection according to the ejection signal Sd. On the other hand, if the cycle Cs of the ejection signal Sd is shorter than the damping time of the residual vibration of the meniscus, ink will be ejected according to the ejection signal Sd while the meniscus is vibrating. As a result, the ejection speed of the ink is remarkably lowered, and the landing position of the ink on the print medium WP may be greatly deviated.

The influence of this residual meniscus vibration on ink ejection depends on the relationship between the phase of the meniscus residual vibration and the ink ejection timing. Here, consider a case where the ink ejection speed drops significantly when the ink ejection timing according to the ejection signal Sd coincides with or approaches one peak of the residual vibration (time t11, t13). In this case, for example, even if the ink ejection timing corresponding to the ejection signal Sd coincides with or approaches the peaks (t12, t14) of the residual vibration on the other side, which have opposite phases to the peaks on the one side of the residual vibration, residual Vibration has little effect on ink ejection. That is, when the ink ejection timing is included in the predetermined residual vibration influence period Pv including the peak on one side of the residual vibration, the residual vibration affects the ink ejection, and the ink ejection timing changes from the residual vibration influence period Pv. If it is off, the effect of residual vibration on ink ejection can be ignored. On the other hand, the cycle Cs (that is, ejection timing) of ejecting ink changes according to the transport speed of the print medium WP. Therefore, whether the influence of the residual meniscus vibration is significant or negligible depends on the transport speed of the print medium WP.

FIG. 6 is a diagram schematically showing an example of temporal changes in the conveying speed of the print medium. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the conveying speed V of the print medium WP. In the example shown in the figure, during the acceleration period Pa, the transport speed V of the print medium WP increases from zero to a predetermined steady speed Vt. During the steady period Pb following the acceleration period Pa, the transport speed V of the print medium WP is constant at the steady speed Vt. Further, in the deceleration period Pc following the steady period Pb, the conveying speed V of the print medium WP decreases from the steady speed Vt to zero.

As described above, the output cycle Cs of the ejection signal Sd is set to be shorter as the transport speed V is higher and longer as the transport speed V is lower. Therefore, the output cycle Cs of the ejection signal Sd changes according to the change in the transport speed V shown in FIG. As a result, when the print medium WP is transported at the transport speed V in the low speed region Rvl from zero speed to Vl, the ink ejection timing according to the ejection signal Sd is out of the residual vibration influence period Pv. Further, when the print medium WP is transported at the transport speed V in the medium speed region Rvm from the speed Vl to the speed Vm higher than the speed Vl, the ejection timing of the ink corresponding to the ejection signal Sd is set during the residual vibration influence period Pv. overlaps with Further, when the print medium WP is transported at a transport speed V in a high speed region Rvh from a speed Vm to a speed Vh higher than the speed Vm, the ink ejection timing corresponding to the ejection signal Sd is set during the residual vibration influence period Pv. deviate from Note that, in this example, the steady-state speed Vt is higher than the speed Vm and lower than the speed Vh. Therefore, different control is executed depending on whether the conveying speed V belongs to the low speed region Rvl, the medium speed region Rvm, or the high speed region Rvh.

FIG. 7 is a diagram schematically showing an example of control according to the speed region to which the transport speed of the print medium belongs. In FIG. 7, the horizontal axis represents time. In the low speed region Rvl, a plurality of ejection signals Sd are output with a cycle Csl, in the middle speed region Rvm, a plurality of ejection signals Sd are output with a cycle Csm shorter than the cycle Csl, and in the high speed region Rvh, a plurality of ejection signals are output. Sd is output with a period Csh shorter than the period Csm.

As described above, in the middle speed region Rvm, the ink ejection timing corresponding to the ejection signal Sd overlaps with the residual vibration influence period Pv, and the ink ejection speed is affected by the residual vibration. In order to cope with this, the calculation unit 391 outputs the fine drive signal Sm to the piezoelectric element 55 at the timing when the predetermined elapsed period Pp has passed since the ejection signal Sd was output to the piezoelectric element 55 .

The fine drive signal Sm is a pulse voltage signal whose voltage changes over time, and the amplitude of the fine drive signal Sm is smaller than the amplitude of the ejection signal Sd. When the calculation unit 391 outputs the fine drive signal Sm to the piezoelectric element 55, the piezoelectric element 55 gives the ink in the cavity 53 pressure fluctuations according to the voltage change indicated by the fine drive signal Sm. Since the amplitude of the fine drive signal Sm is small, the ink is not ejected from the nozzles 52 due to the pressure fluctuation of the ink according to the fine drive signal Sm. In other words, the fine drive signal Sm is a signal that prevents ejection of ink from the nozzles 52 and causes pressure fluctuations in the ink inside the cavity 53 . Then, the residual vibration of the meniscus is suppressed by the minute pressure fluctuations generated in response to the minute drive signal Sm. Therefore, when the ejection signal Sd is output after the fine drive signal Sm, the residual vibration of the meniscus can be sufficiently attenuated.

The elapsed period Pp for giving the output timing of the fine drive signal Sm is set to a period shorter than the period Csm. Theoretically, it is preferable to set the elapsed period Pp so that the output timing of the fine drive signal Sm overlaps with the residual vibration influence period Pv, in other words, so that it coincides with the peak of the residual vibration in the residual vibration influence period Pv. . However, the elapsed period Pp can also be obtained experimentally as described later.

As shown in FIG. 7, only the ejection signal Sd of the ejection signal Sd and the fine drive signal Sm is output to the piezoelectric element 55 during the period in which the print medium WP is transported at the transport speed V in the low speed region Rvl. Fine drive signal Sm is not output. While the print medium WP is being conveyed at the conveying speed V in the medium speed region Rvm, the ejection signal Sd is output to the piezoelectric element 55, and the fine drive signal Sm is output to the piezoelectric element 55 following the ejection signal Sd. be. Of the ejection signal Sd and the fine drive signal Sm, only the ejection signal Sd is output to the piezoelectric element 55, and the fine drive signal Sm is not output during the period in which the print medium WP is transported at the transport speed V in the high speed region Rvh. . In this manner, whether or not to output the fine drive signal Sm is switched according to the speed regions Rvl, Rvm, and Rvh to which the conveying speed V belongs.

In the embodiment described above, when the transport speed V of the print medium WP is in the low speed region Rvl (first speed range), the ejection signal Sd is applied to the piezoelectric element 55 (driven element), but does not output the fine drive signal Sm to the piezoelectric element 55. FIG. As a result, when the transport speed V of the print medium WP is low and there is no influence of residual vibration, ink can be appropriately ejected from the nozzles 52 by not outputting the fine drive signal Sm to the piezoelectric element 55 . Further, when the conveying speed V is in the medium speed region Rvm (second speed range) higher than the low speed region Rvl, while the ejection signal Sd is output to the piezoelectric element 55 at the cycle Csm corresponding to the conveying speed V, The fine drive signal Sm is output to the piezoelectric element 55 between the ejection signals Sd that are continuously output. As a result, when the conveying speed V of the print medium WP increases and the influence of the residual vibration begins to appear, the fine drive signal Sm is output to the piezoelectric element 55 to suppress the influence of the residual vibration. Ink can be appropriately ejected from the nozzles 52 . Further, when the conveying speed V is in the high speed region Rvh (third speed range) higher than the medium speed region Rvm, the ejection signal Sd is output to the piezoelectric element 55 at the cycle Csh corresponding to the conveying speed V. The fine drive signal Sm is not output to the piezoelectric element 55 . As a result, when the transport speed V of the print medium WP is further increased, the ink can be appropriately ejected from the nozzles 52 by not outputting the fine drive signal Sm to the piezoelectric element 55 . As a result, it is possible to output the fine drive signal Sm to the piezoelectric element 55 in an appropriate manner according to the transport speed V of the print medium WP.

FIG. 8 is a flow chart showing an example of processing for determining the target speed region for outputting the fine drive signal. The flowchart of FIG. 8 determines the medium speed region Rvm shown in FIGS. In step S101, Qv that identifies the transport speed V is reset to zero, and in step S102, Qv is incremented by one. In this example, the higher the value of Qv, the higher the conveying speed V is. Then, in step S103, the print medium WP is transported at the transport speed V (Qv). Further, in step S104, the cycle Cs for outputting the ejection signal Sd is set according to the transport speed V (Qv).

In step S105, a patch image is printed on the print medium WP transported at a constant transport speed V (Qv). In step S105, the calculation unit 391 prints the patch image by outputting only the ejection signal Sd to the piezoelectric element 55 without outputting the fine drive signal Sm. Thus, a patch image is printed with ink ejected from the nozzles 52 in response to each ejection signal Sd. In addition, as described above, the printing unit 13 has a plurality of ejection heads 5 . However, the configuration of each ejection head 5 provided in the printing device 3 is common. Therefore, printing of patch images may be executed using one ejection head 5 .

The patch image printed on the print medium WP in this manner moves toward the imaging position of the line scanner 17 as the print medium WP is conveyed. Then, the line scanner 17 acquires the captured image IM(Qv) by capturing the patch image that has reached the imaging position, and stores it in the storage unit 392 (step S106).

In step S107, it is determined whether or not Qv matches Qvx. If Qv does not match Qvx ("NO" in step S107), Qv is incremented by 1 in step S102, and the conveying speed V (Qv) is increased by one step. In step S103, the print medium WP is transported at the transport speed V(Qv), and in step S104, the output timing of the ejection signal Sd is set according to the transport speed V(Qv). Then, the patch image is printed, captured, and saved (steps S105 and S106).

In this way, by repeating steps S103 to S106 while increasing the transport speed V(Qv), the captured image IM(Qv) of the patch image printed on the print medium WP while transporting the print medium WP at different transport speeds V ) is obtained. Then, when it is determined in step S107 that Qv matches Qvx (YES), the calculation unit 391 analyzes the captured image IM(Qv) (steps S108 and S109).

Specifically, in step S108, a plurality of captured images IM (Qv) (Qv=1, 2, . density unevenness is calculated. In step S109, a medium speed region Rvm (target speed region) is determined based on this density unevenness. Specifically, a captured image IM(Qv) having density unevenness larger than a predetermined threshold is specified. In other words, when the ink is affected by the residual vibration, the ink ejection is not stable, and the printed patch image has large density unevenness. In other words, the captured image IM(Qv) showing large density unevenness is composed of ink ejected while being affected by the residual vibration. Therefore, the medium speed region Rvm (target speed region) can be specified based on the transport speed V of the print medium WP when the captured image IM(Qv) is printed. Further, along with the identification of the middle speed region Rvm, the speed region lower than the middle speed region Rvm is identified as the low speed region Rvl, and the speed region higher than the middle speed region Rvm is identified as the high speed region Rvh.

Various methods for calculating density unevenness can be considered. For example, the captured image IM(Qv) may be divided into a plurality of minute areas, and the variance or standard deviation of the density of each of the plurality of minute areas may be calculated as the density unevenness.

As described above, in the target speed region determination process of FIG. 8, the calculation unit 391 performs a test printing operation (step S102) of printing a patch image (test image) on the print medium WP by ink ejected from the nozzles 52 of the ejection head 5. to S105), and a condition determination operation (step S106) for determining the condition (middle speed region Rvm) for outputting the fine drive signal Sm to the piezoelectric element 55 based on the result of the patch image being imaged by the line scanner 17 (detection unit). to S109) are executed. As a result, the conditions for outputting the fine drive signal Sm to the piezoelectric element 55 (medium speed region Rvm) can be optimized.

In particular, in steps S102 to S105, while the fine driving signal Sm is not output to the piezoelectric element 55, the conveying motor 341 (driving unit) changes the conveying speed V and discharges at a cycle Cs (time interval) according to the conveying speed V. A signal Sd is output to the piezoelectric element 55 to print a patch image. Then, in steps S106 to S109, based on the result of picking up the patch image by the line scanner 17, the low velocity area Rvl, the medium velocity area Rvm and the high velocity area Rvh are determined. Thus, the low speed region Rvl and the high speed region Rvh in which the fine drive signal Sm should not be output to the piezoelectric element 55 and the medium speed region Rvm in which the fine drive signal Sm should be output to the piezoelectric element 55 are appropriately selected. can be

FIG. 9 is a flow chart showing an example of processing for determining the timing for outputting the fine drive signal. As described above, the output timing of the fine drive signal Sm is given by the elapsed period Pp. Therefore, the flowchart of FIG. 9 determines the elapsed period Pp shown in FIG. In step S201, the conveying speed V is set to the medium speed region Rvm. For example, the transport speed V can be set to the median value of the medium speed region Rvm determined in the target speed region determination process of FIG. In step S202, the print medium WP is transported at the transport speed V thus set.

In step S203, Qp, which identifies the elapsed period Pp, is reset to zero, and in step S204, Qp is incremented by one. In this example, a larger value of Qp indicates a longer elapsed period Pp. Then, in step S205, the output timing of the fine driving signal Sm is set to the timing when the elapsed period Pp (Qp) has elapsed from the ejection signal Sd.

In step S206, the patch image is printed on the print medium WP transported at a constant transport speed V. FIG. In this step S206, the calculation unit 391 outputs the ejection signal Sd to the piezoelectric element 55 at the cycle Cs corresponding to the transport speed V, and outputs the fine drive signal Sm at the timing when the elapsed period Pp (Qp) has elapsed from the ejection signal Sd. to the piezoelectric element 55 to print the patch image. As in the case of the target speed area determination process described above, the printing of patch images may be executed using one ejection head 5 .

The patch image printed on the print medium WP in this manner moves toward the imaging position of the line scanner 17 as the print medium WP is conveyed. Then, the line scanner 17 acquires the captured image IM(Qp) by capturing the patch image that has reached the imaging position, and stores it in the storage unit 392 (step S207).

In step S208, it is determined whether or not Qp matches Qpx. If Qv does not match Qvx ("NO" in step S208), Qp is incremented by 1 in step S204 to lengthen the elapsed period Pp (Qp) by one step. Steps S205 to S207 are executed based on the changed elapsed period Pp (Qp).

In this way, by repeating steps S205 to S207 while increasing the elapsed period Pp (Qp), the patch image printed on the print medium WP while outputting the fine drive signal Sm at different timings of the elapsed period Pp. A captured image IM(Qp) is acquired. Then, when it is determined in step S208 that Qp matches Qpx (YES), the calculation unit 391 analyzes the captured image IM (Qp) (steps S209 and S210).

More specifically, in step S209, a plurality of captured images IM (Qp) (Qp=1, Qp=1, 2, . . . , Qpx). In step S209, the elapsed period Pp is determined based on this density unevenness. Specifically, the captured image IM(Qp) having the smallest density unevenness is specified among the plurality of captured images IM(Qp). In other words, if the elapsed period Pp is inappropriate and the influence of residual vibration cannot be suppressed, ink ejection will not be stable, resulting in large density unevenness in the printed patch image. In a state in which the influence of the residual vibration is suppressed, the ejection of ink is stable, and density unevenness of the printed patch image can be kept small. In other words, the picked-up image IM(Qp) showing the minimum density unevenness is composed of ink ejected while suppressing the influence of the residual vibration. Therefore, the elapsed period Pp (Qp) when this captured image IM (Qp) is printed is specified.

As described above, in the fine drive timing determination process of FIG. 9, the calculation unit 391 performs a test printing operation (step S204) of printing a patch image (test image) on the print medium WP by ink ejected from the nozzles 52 of the ejection head 5. to S206), and a condition determination operation (steps S207 to S210) for determining the condition (elapsed period Pp) for outputting the fine drive signal Sm to the piezoelectric element 55 based on the result of picking up the patch image by the line scanner 17. do. This makes it possible to optimize the condition (elapsed period Pp) for outputting the fine drive signal Sm to the piezoelectric element 55 .

In particular, in steps S204 to S206, the ejection signal Sd is output to the piezoelectric element 55 at a cycle Cs corresponding to the transportation speed V while the print medium WP is being moved at the transportation speed V in the middle speed region Rvm. The patch image is printed on the print medium WP by outputting the fine drive signal Sm at the timing when the elapsed period Pp elapses while changing the elapsed period Pp from output to output of the fine drive signal Sm. Then, in steps S207 to S210, based on the result of picking up the patch image by the line scanner 17, the elapsed period Pp until the fine drive signal Sm is output following the ejection signal Sd is determined. This makes it possible to optimize the timing of outputting the fine drive signal Sm to the piezoelectric element 55 following the ejection signal Sd.

FIG. 10 is a flow chart showing an example of processing for determining the amplitude of the fine drive signal. The flow chart of FIG. 10 determines the amplitude of the fine drive signal Sm shown in FIG. In step S301, the conveying speed V is set to the medium speed region Rvm. For example, the transport speed V can be set to the median value of the medium speed region Rvm determined in the target speed region determination process of FIG. In step S302, the print medium WP is transported at the transport speed V thus set.

In step S303, Qa, which identifies the amplitude Am of the fine drive signal Sm, is reset to zero, and in step S304, Qa is incremented by one. In this example, a larger value of Qa indicates a larger amplitude Am. Then, in step S305, the amplitude Am of the fine drive signal Sm is set to A (Qa). Further, in step S306, the elapsed period Pp for giving the output timing of the fine drive signal Sm is set to the elapsed period Pp (Qp) determined in the fine drive timing determination process.

In step S307, the patch image is printed on the print medium WP transported at a constant transport speed V. FIG. In this step S307, the calculation unit 391 outputs the ejection signal Sd to the piezoelectric element 55 at the cycle Cs corresponding to the transport speed V, and outputs the fine drive signal Sm at the timing when the elapsed period Pp (Qp) has elapsed from the ejection signal Sd. to the piezoelectric element 55 to print the patch image. As in the case of the target speed area determination process described above, the printing of patch images may be executed using one ejection head 5 .

The patch image printed on the print medium WP in this manner moves toward the imaging position of the line scanner 17 as the print medium WP is conveyed. Then, the line scanner 17 acquires the captured image IM(Qp) by capturing the patch image that has reached the imaging position, and stores it in the storage unit 392 (step S308).

In step S309, it is determined whether or not Qa matches Qax. If Qa does not match Qax ("NO" in step S309), Qa is incremented by 1 in step S304 to increase amplitude Am(Qa) by one step. Steps S305 to S308 are executed based on the amplitude Am(Qa) thus changed.

In this way, by repeating steps S305 to S308 while increasing the amplitude Am(Qa), the captured image IM of the patch image printed on the print medium WP while outputting the fine drive signals Sm with mutually different amplitudes Am(Qa). (Qa) is obtained. Then, when it is determined in step S309 that Qa matches Qax (YES), the calculation unit 391 analyzes the captured image IM(Qa) (steps S310 and S311).

Specifically, in step S310, a plurality of captured images IM (Qp) (Qp=1, 2, . ) each density unevenness is calculated. In step S310, the amplitude Am (Qa) is determined based on this density unevenness. Specifically, among the plurality of captured images IM(Qa), the captured image IM(Qa) having the smallest density unevenness is specified. In other words, if the amplitude Am(Qa) is inappropriate and the influence of the residual vibration cannot be suppressed, the ink ejection will not be stable, resulting in large density unevenness in the printed patch image, while the amplitude Am(Qa) is appropriate and the influence of the residual vibration can be suppressed, the ejection of ink is stable, and the density unevenness of the printed patch image can be kept small. In other words, the captured image IM(Qa) showing the minimum density unevenness is composed of ink ejected while suppressing the influence of the residual vibration. Therefore, the amplitude Am(Qa) when printing this captured image IM(Qa) is specified.

As described above, in the fine drive amplitude determination process of FIG. 10, the calculation unit 391 performs a test printing operation (step S304) of printing a patch image (test image) on the print medium WP by ink ejected from the nozzles 52 of the ejection head 5. to S307), and a condition determination operation (steps S308 to S311) for determining the condition (amplitude Am) for outputting the fine drive signal Sm to the piezoelectric element 55 based on the result of picking up the patch image by the line scanner 17. . This makes it possible to optimize the conditions (amplitude Am) for outputting the fine drive signal Sm to the piezoelectric element 55 .

In particular, in steps S304 to S307, while the print medium WP is being moved at the transport speed V in the medium speed region Rvm, the ejection signal Sd is output to the piezoelectric element 55 at the cycle Cs corresponding to the transport speed V. The patch image is printed on the print medium WP while changing the amplitude Am of the fine drive signal Sm to be subsequently output. Then, in steps S308 to S311, the amplitude Am of the fine drive signal Sm is determined based on the result of the patch image picked up by the line scanner 17. FIG. This makes it possible to optimize the amplitude Am of the fine drive signal Sm.

In the embodiment described above, the printing device 3 corresponds to an example of the "printing device" of the present invention, and the drive roller 7, the plurality of conveying rollers 9 and the drive roller 11 are examples of the "driving unit" of the present invention. , the line scanner 17 corresponds to an example of the "detection unit" of the present invention, the control unit 39 corresponds to an example of the "control unit" and the "computer" of the present invention, and the print program 393 corresponds to the "printing unit" of the present invention. The recording medium 399 corresponds to an example of the "recording medium" of the present invention, the ejection head 5 corresponds to the "ejection head" of the present invention, and the nozzle 52 corresponds to the "nozzle" of the present invention. The cavity 53 corresponds to an example of the "pressure chamber" of the present invention, the piezoelectric element 55 corresponds to an example of the "driving element" of the present invention, and the low velocity region Rvl corresponds to the "first velocity" of the present invention. range”, the medium speed region Rvm corresponds to an example of the “second speed range” of the present invention, and the high speed region Rvh corresponds to an example of the “third speed range” of the present invention. The Sd corresponds to an example of the "ejection signal" of the present invention, and the fine drive signal Sm corresponds to an example of the "fine drive signal" of the present invention.

The present invention is not limited to the above-described embodiments, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, the method of ejecting ink is not limited to the method using the piezoelectric element 55 described above.

Further, the specific mechanism for moving the print medium WP relative to the ejection head 5 is not limited to the above example. That is, instead of transporting the print medium WP by the drive roller 7, the plurality of transport rollers 9, and the drive roller 11, the ejection head 5 may be moved by the carriage.

Also, the patch image printing described above is executed using one ejection head 5 . However, a plurality of ejection heads 5 may be used to print patch images.

8, 9 and 10 are not essential, and the conditions for outputting the fine drive signal Sm may be set by other methods. may decide.

Further, although the material of the print medium WP described above is continuous paper, the material is not limited to this, and may be, for example, a sheet of paper. Moreover, the material of the printing medium is not necessarily limited to paper, and examples include OPP (oriented polypropylene) and PET (polyethylene).
terephthalate) or the like.

INDUSTRIAL APPLICABILITY The present invention can be applied to general inkjet technology that ejects ink from nozzles communicating with pressure chambers by applying pressure fluctuations to the ink stored in the pressure chambers.

3... Printing device 7... Driving roller (driving unit)
9... Conveying roller (driving unit)
11... Driving roller (driving unit)
17 line scanner (detection unit)
39... Control unit (computer)
393...Printing program 399...Recording medium 5...Ejection head 52...Nozzle 53...Cavity (pressure chamber)
55 Piezoelectric element (driving element)
Rvl: Low speed range (first speed range)
Rvm: middle speed range (second speed range)
Rvh: high speed range (third speed range)
Sd... Ejection signal Sm... Fine drive signal

Claims (8)

an ejection head having a pressure chamber that stores ink, a nozzle that communicates with the pressure chamber, and a driving element that applies pressure fluctuations to the ink in the pressure chamber;
a drive unit that moves the print medium facing the nozzles relative to the ejection head;
An ejection signal that gives pressure fluctuations for ejecting ink from the nozzles to the ink in the pressure chambers and a fine drive signal that gives pressure fluctuations to the ink in the pressure chambers for not ejecting ink from the nozzles are output to the drive element. and a control unit,
The control unit
When the relative speed between the print medium and the ejection head is within the first speed range, the ejection signal is output to the drive element at time intervals corresponding to the relative speed, and the fine drive signal is applied to the driving element. without outputting to the element,
When the relative speed is in a second speed range higher than the first speed range, the discharge signal is output to the drive element at time intervals corresponding to the relative speed, and the discharge signal is continuously output. outputting the fine drive signal to the drive element between ejection signals;
When the relative speed is in a third speed range higher than the second speed range, the ejection signal is output to the drive element at time intervals corresponding to the relative speed, and the fine drive signal is output to the driving element. A printing device that does not output to an element. further comprising a detection unit that detects ink that has landed on the print medium;
The control unit
a test printing operation of printing a test image on the print medium by ink ejected from the nozzles of the ejection head;
2. The printing apparatus according to claim 1, further comprising determining a condition for outputting the fine drive signal to the drive element based on the result of detection of the test image by the detection unit. In the test printing operation, while the fine drive signal is not output to the drive element, the ejection signal is output to the drive element at time intervals corresponding to the relative speed while changing the relative speed by the drive unit. to print the test image,
3. The printing apparatus according to claim 2, wherein in said condition determination operation, said first speed range, said second speed range and said third speed range are determined based on a result of detection of said test image by said detection unit. In the test printing operation, the print medium is moved with respect to the ejection head at the relative speed in the second speed range, and the ejection signal is output to the drive element at time intervals corresponding to the relative speed. printing the test image on the print medium by outputting the fine drive signal at the timing while changing the timing of outputting the fine drive signal following the output of the ejection signal;
4. The printing apparatus according to claim 2, wherein, in said condition determination operation, timing for outputting said fine drive signal subsequent to said ejection signal is determined based on a result of detection of said test image by said detection unit. In the test printing operation, the print medium is moved with respect to the ejection head at the relative speed in the second speed range, and the ejection signal is output to the drive element at time intervals corresponding to the relative speed. printing the test image on the print medium while changing the amplitude of the fine drive signal output following the ejection signal;
5. The printing apparatus according to any one of claims 2 to 4, wherein in said condition determination operation, the amplitude of said fine drive signal is determined based on the result of detection of said test image by said detection unit. A printing method in which ink is ejected onto a printing medium from the nozzles of an ejection head having pressure chambers for storing ink, nozzles communicating with the pressure chambers, and driving elements that apply pressure fluctuations to the ink in the pressure chambers,
While moving the print medium relative to the ejection head at a relative speed within a first speed range, an ejection signal that imparts pressure fluctuations for ejecting ink from the nozzles to the ink in the pressure chamber is set to the relative speed. outputting to the drive element at corresponding time intervals;
While moving the print medium relative to the ejection head at a relative speed in a second speed range higher than the first speed range, the ejection signal is applied to the drive element at time intervals according to the relative speed. a step of outputting a fine drive signal to the drive element between the successively output ejection signals, while outputting a fine drive signal that applies a pressure fluctuation to the ink in the pressure chamber that does not eject ink from the nozzle;
While moving the print medium relative to the ejection head at a relative speed in a third speed range higher than the second speed range, the ejection signal is sent to the drive element at time intervals according to the relative speed. and outputting,
In the step of moving the print medium at a relative speed within the first speed range and the step of transporting the print medium at a relative speed within the third speed range, the printing method does not output the fine drive signal to the drive element. . A computer controls the ejection of ink onto a print medium from the nozzles of an ejection head having pressure chambers for storing ink, nozzles communicating with the pressure chambers, and driving elements that apply pressure fluctuations to the ink in the pressure chambers. In the printing program to be controlled,
While moving the print medium relative to the ejection head at a relative speed within a first speed range, an ejection signal that imparts pressure fluctuations for ejecting ink from the nozzles to the ink in the pressure chamber is set to the relative speed. outputting to the drive element at corresponding time intervals;
While moving the print medium relative to the ejection head at a relative speed in a second speed range higher than the first speed range, the ejection signal is applied to the drive element at time intervals according to the relative speed. a step of outputting a fine drive signal to the drive element between the successively output ejection signals, while outputting a fine drive signal that applies a pressure fluctuation to the ink in the pressure chamber that does not eject ink from the nozzle;
While moving the print medium relative to the ejection head at a relative speed in a third speed range higher than the second speed range, the ejection signal is sent to the drive element at time intervals according to the relative speed. causing the computer to execute a step of outputting,
a printing program that does not output the fine drive signal to the drive element in the step of moving the print medium at a relative speed within the first speed range and the step of transporting the print medium at a relative speed within the third speed range; . A recording medium for recording the print program according to claim 7 in a computer-readable manner.

Images