Liquid discharge device

Abstract

To provide a liquid discharge device that is configured to slightly vibrate a liquid surface in a nozzle in a non-jetting period of time during which the nozzle does not jet liquid so as to prevent the liquid from thickening, which can prevent the liquid in the nozzle from thickening even when the non-jetting period of time is long.SOLUTION: The liquid discharge device comprises a head having a nozzle group and a control part for controlling the head. The control part executes stand-by time determination of determining whether a stand-by time that is required after a reference time until a discharging start time at which a specific nozzle starts discharging liquid is within a predetermined reference time or not. When the stand-by time determination shows that the stand-by time is within the reference time, the control part executes first non-discharge driving which vibrates a surface of the liquid in the specific nozzle fine enough not to discharge the liquid from the specific nozzle. Unless the determination shows that the stand-by time is within the reference time, the control part executes second non-discharge driving which vibrates the liquid surface in the specific nozzle by vibration smaller than vibration in the first non-discharge driving.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection device, and more particularly to a technique for suppressing thickening of liquid inside a nozzle provided in a head. [Background technology]

[0002] For example, as disclosed in Patent Document 1, a liquid ejection device is known that, if the length of a non-ejection period during which liquid is not ejected from a nozzle provided in a head is longer than a threshold value, vibrates the liquid surface in the nozzle slightly, and if the length of that period is shorter than the threshold value, stops the vibration, thereby preventing the liquid from thickening and reducing the amount of liquid consumed due to nozzle flushing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-171308 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, if the non-ejection period is relatively long, continuing to slightly vibrate the liquid surface in the nozzle of the liquid ejection device during that period will cause the liquid to be stirred in the nozzle, resulting in excessive evaporation of the liquid and actually causing the viscosity of the liquid to increase.

[0005] Therefore, the present disclosure aims to provide a liquid ejection device that suppresses thickening of the liquid by slightly vibrating the liquid surface in the nozzle during non-ejection periods when liquid is not ejected from the nozzle, and to make it possible to suppress thickening of the liquid in the nozzle even when the non-ejection period is long. [Means for solving the problem]

[0006] In order to solve the above problem, a liquid ejection device according to one aspect of the present disclosure includes a head having a group of nozzles that eject liquid onto a recording medium, and a control unit that controls the head to perform a printing process based on print job information, wherein the control unit performs a wait time determination to determine whether the wait time required from a predetermined reference time for the printing process to an ejection start time at which ejection of liquid from a specific nozzle belonging to the nozzle group begins is within a predetermined reference time, and if the wait time determination determines that the wait time is within the reference time, performs a first non-ejection drive that vibrates the liquid surface in the specific nozzle with a vibration of a magnitude that prevents the liquid from being ejected from the specific nozzle, and if the wait time determination determines that the wait time is not within the reference time, performs a second non-ejection drive that vibrates the liquid surface in the specific nozzle with a vibration of a magnitude smaller than that of the first non-ejection drive. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, in a liquid ejection device that suppresses thickening of the liquid by slightly vibrating the liquid surface in the nozzle during non-ejection periods when liquid is not ejected from the nozzle, thickening of the liquid in the nozzle can be suppressed even if the non-ejection period is long. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view showing a schematic configuration of a liquid ejection device according to a first embodiment. [Figure 2] FIG. 2 is a functional block diagram of the liquid ejection device of FIG. [Figure 3] FIG. 3 is a control flow diagram of the liquid ejection device of FIG. [Figure 4] FIG. 4 is a cross-sectional view that schematically shows vibrations of a liquid surface L of the liquid inside a specific nozzle that the liquid ejection device of FIG. 1 has. [Figure 5] FIG. 5 is a diagram showing a driving waveform of a voltage applied to the piezoelectric element of FIG. [Figure 6] FIG. 6 is a plan view schematically showing the non-ejection drive of the liquid ejection device according to the first embodiment. [Figure 7] FIG. 7 is a plan view schematically showing the non-ejection drive of the liquid ejection device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, each embodiment of the present disclosure will be described with reference to the drawings. Note that the same or corresponding elements throughout the drawings will be designated by the same reference numerals, and redundant description will be omitted. Furthermore, the present disclosure is not limited to the embodiments, and additions, deletions, and modifications are possible within the scope of the present disclosure.

[0010] (First embodiment) [Configuration of liquid ejection device] FIG. 1 is a plan view showing a schematic configuration of a liquid ejection device 1 (hereinafter also referred to as "device 1") according to a first embodiment. The device 1 is an inkjet printer that performs a printing process in which a liquid such as ink is ejected (squirted) from nozzles 22 (see FIG. 4) included in a nozzle group 21 of a head 2 to form characters, images, etc. on a sheet-like recording medium M. The device 1 is of a serial head type, and forms an image on the recording medium M by ejecting a liquid from the nozzles 22 included in the nozzle group 21 of the head 2.

[0011] As will be described later, if the waiting time T2 required from a reference time T0 predetermined for the printing process to an ejection start time T1 at which ejection of liquid from a specific nozzle 23 included in the nozzle group 21 begins is within the reference time Tr, the device 1 executes a first non-ejection drive that vibrates the liquid level L (see FIG. 4) in the specific nozzle 23 with a vibration of a magnitude that prevents liquid from being ejected from the specific nozzle 23. Furthermore, if the waiting time T2 is not within the reference time Tr, the device 1 executes a second non-ejection drive that vibrates the liquid level L in the specific nozzle 23 with a vibration of a magnitude smaller than that of the first non-ejection drive. In this way, the device 1 is configured to suppress thickening of the liquid in the specific nozzle 23, regardless of the length of the period during which liquid is not ejected from the specific nozzle 23.

[0012] Specifically, as shown in FIG. 1, the device 1 includes a head 2, a carriage 3, a platen 4, a transport mechanism 5, a liquid tank 7, a control unit 8, and a casing 10. The head 2 has a nozzle group 21 including nozzles 22 that eject liquid onto the recording medium M. In this embodiment, the nozzle group 21 includes a plurality of color-specific nozzle groups that eject liquid of different colors. The head 2 is disposed on the carriage 3. The carriage 3 moves back and forth together with the head 2 in a direction P2 (main scanning direction) perpendicular to a transport direction P1 (sub-scanning direction) of the recording medium M. This causes the head 2 to scan the recording medium M in a predetermined direction.

[0013] The platen 4 is a plate member with a flat upper surface, and is disposed opposite the head 2. The dimension of the platen 4 in the orthogonal direction P2 is longer than that of the head 2. As a result, the platen 4 is disposed so that the entire landing area of ​​droplets ejected from each nozzle 22 included in the nozzle group 21 is located within the upper surface area of ​​the platen 4. The platen 4 supports, on its upper surface, the recording medium M that is transported along a predetermined transport direction P1. This defines the distance between the head 2 and the recording medium M.

[0014] The transport mechanism 5 has two pairs of transport rollers 12 and 13, and a transport motor. One of the pairs of transport rollers, 12, is disposed upstream of the platen 4 in the transport direction P1. The transport roller pair 12 includes a vertical pair of a drive roller and a driven roller. The drive roller is driven by the transport motor, and holds the recording medium M between itself and the driven roller, and transports the recording medium M downstream in the transport direction P1 onto the platen 4.

[0015] The other pair of transport rollers 13 is disposed downstream in the transport direction P1 relative to the platen 4. The pair of transport rollers 13 includes a vertical pair of a drive roller and a driven roller. The drive roller is driven by a transport motor, and holds the recording medium M between itself and the driven roller, and transports the recording medium M from the platen 4 downstream in the transport direction P1.

[0016] The multiple liquid tanks 7 store liquid to be supplied to the multiple heads 2. The device 1 of this embodiment includes multiple liquid tanks 7, the number of which corresponds to the type of ink, which is an example of the liquid. The device 1 includes, as an example of the multiple liquid tanks 7, a first tank 7A that stores ink of a first color and a second tank 7B that stores ink of a second color. The color of the ink can be set appropriately. For example, two colors can be selected from black, blue, and red. The multiple liquid tanks 7 are connected to the multiple heads 2 by supply tubes 14. The liquid stored in the multiple liquid tanks 7 is supplied to the heads 2 via the supply tubes 14. The control unit 8 controls the operation of the drive elements of each part of the device 1. The casing 10 houses the liquid tanks 7 and the control unit 8.

[0017] FIG. 2 is a functional block diagram of the device 1. As shown in FIG. 2, the device 1 further includes at least one piezoelectric element 20 arranged to correspond to each nozzle 22 included in the nozzle group 21, and a head driver 15 that operates the piezoelectric element 20. The piezoelectric element 20 applies pressure to the liquid so that the liquid is ejected from the nozzle 22 when an externally applied voltage is applied. The piezoelectric element 20 also applies pressure to the liquid in the nozzle 22 when an externally applied voltage is applied to the liquid so that the liquid vibrates at a level that does not cause the liquid to be ejected from the nozzle 22 (details will be described later as "non-ejection driving"). The device 1 also includes an operation unit 16, a display unit 17, and a movement mechanism 18. The operation unit 16 is operated by a user to input a predetermined job. The display unit 17 displays information to the user. The movement mechanism 18 has a drive motor and moves the carriage 3 in the orthogonal direction P2 (main scanning direction).

[0018] The control unit 8 has a calculation unit 80 and a storage unit 81. As an example, the calculation unit 80 includes a circuit such as a processor exemplified by an MPU or an integrated circuit exemplified by an ASIC. The calculation unit 80 may have either a single processor or multiple processors. As an example, the storage unit 81 includes a ROM, a RAM, and an EEPROM.

[0019] The ROM stores a control program for the calculation unit 80 to execute predetermined jobs (including jobs related to the first and second non-ejection drives, which will be described later). The EEPROM stores various initial setting information input by the user. As an example, the processor, ROM, RAM, and EEPROM are mounted on a mounting board.

[0020] The calculation unit 80 receives a command to execute a print job via the operation unit 16 or an external input unit. Upon receiving the command to execute a print job, the calculation unit 80 drives the transport mechanism 5, the head driver 15, and the movement mechanism 18 at a predetermined timing.

[0021] When the device 1 is in operation, the control unit 8, upon receiving an external command to execute a print job, controls the transport mechanism 5 to transport the recording medium M onto the platen 4. When the recording medium M reaches a predetermined position on the platen 4, it controls the movement mechanism 18 to scan the head 2 together with the carriage 3 in the orthogonal direction P2. The control unit 8 also controls the head driver 15 to eject liquid from the nozzles 22 of the nozzle group 21 of the head 2 based on image data specified by the print job information, thereby forming an image on the recording medium M. In this way, the printing process is executed.

[0022] In the printing process, the recording medium M is transported from the upstream side to the downstream side in the transport direction P1, while the carriage 3 scans back and forth along a plurality of virtual scanning lines (see scanning lines SL1 to SL4 in FIG. 6) parallel to the perpendicular direction P2. At this time, liquid is ejected toward the recording medium M from predetermined nozzles 22 included in the nozzle group 21 of the head 2, thereby forming an image on the recording medium M. The recording medium M on which the image has been formed is transported by the transport mechanism 5 and discharged from the device 1.

[0023] [Non-ejection drive] Here, the control unit 8 performs a wait time determination to determine whether the wait time T2 required from a reference time T0 predetermined for the printing process to an ejection start time T1 at which ejection of liquid from a specific nozzle 23 included in the nozzle group 21 begins is within a predetermined reference time Tr. If the control unit 8 determines in the wait time determination that the wait time T2 is within the reference time Tr, it performs a first non-ejection drive that vibrates the liquid level L in the specific nozzle 23 with a vibration of a magnitude that prevents liquid from being ejected from the specific nozzle 23. Furthermore, if the control unit 8 determines in the wait time determination that the wait time T2 is not within the reference time Tr, it performs a second non-ejection drive that vibrates the liquid level L in the specific nozzle 23 with a vibration of a magnitude smaller than that of the first non-ejection drive. The operation of the device 1, including this non-ejection drive, will be described below.

[0024] Figure 3 is a control flow diagram of the device 1 in Figure 1. In the following description, "S" indicates a step, and "Yes" or "No" following ":" indicates the determination result at the step described immediately before ":".

[0025] During operation of the device 1, the control unit 8 first determines whether a print job has been received (S1). In S1, the control unit 8 repeats this determination until it determines that a print job has been received. If the control unit 8 determines that a print job has been received in S1 (S1: Yes), it then determines whether the waiting time T2 is within the reference time Tr (S2). This performs a waiting time determination to determine whether the waiting time T2 is within a predetermined reference time Tr. If the control unit 8 determines in the waiting time determination of S2 that the waiting time T2 is within the reference time Tr (S2: Yes), it then executes the first non-ejection drive (S3).

[0026] FIG. 4 is a cross-sectional view schematically illustrating the vibration of the liquid level L (also referred to as meniscus vibration) inside the specific nozzle 23 included in the device 1 of FIG. 1. FIG. 4 shows a cross-sectional view of the specific nozzle 23 along the nozzle axis direction. The dashed line in FIG. 4 indicates the position of the liquid level L inside the specific nozzle 23. As shown in FIG. 4, the control unit 8 drives the piezoelectric element 20 to apply pressure to the liquid inside the specific nozzle 23, thereby vibrating the liquid level L inside the specific nozzle 23 in the nozzle axis direction. This circulates the liquid inside the specific nozzle 23, preventing the liquid from thickening. In this embodiment, as an example, the control unit 8 individually determines the standby time for each specific nozzle 23 belonging to each of the multiple color nozzle groups. After performing the process of S3 for a predetermined time, the control unit 8 executes the printing process (S4).

[0027] Alternatively, if the control unit 8 determines in the standby time determination of S2 that the standby time T2 is not within the reference time Tr (in other words, that the standby time T2 exceeds the reference time Tr) (S2: No), then it executes a second non-ejection drive (S5). In this second ejection drive, the control unit 8 vibrates the liquid level L in the specific nozzle 23 with a smaller magnitude of vibration than the first non-ejection drive. As another example, the control unit 8 of this embodiment executes a standby time determination and the first non-ejection drive or the second non-ejection drive based on the result of the standby time determination for each specific nozzle 23 individually. After executing the process of S5 for a predetermined time, the control unit 8 executes the printing process (S4).

[0028] FIG. 6 is a plan view schematically illustrating the non-ejection drive of the device 1 according to the first embodiment. In FIG. 6, the first non-ejection drive, the second non-ejection drive, and the printing process executed by the device 1 are schematically illustrated using marks C1, C2, and C6. For illustrative purposes, in FIG. 6, the vibration magnitude of the liquid in the specific nozzle 23 during the first non-ejection drive is indicated by a relatively large circular mark C1, the vibration magnitude of the liquid in the specific nozzle 23 during the second non-ejection drive is indicated by a relatively small circular mark C2, and the ejection state of the liquid from the specific nozzle 23 during the printing process is indicated by a rectangular mark C6. The head 2 is scanned in the direction of the arrows shown in FIG. 6 along imaginary scanning lines SL1 to SL4.

[0029] 6, during scanning of the head 2, the control unit 8 first performs a first non-ejection drive on the entire area of ​​the scan line SL1 on the recording medium M being transported in the transport direction P1. Then, the control unit 8 performs a printing process on the recording medium M up to an intermediate area on the scan line SL2. Then, the control unit 8 performs the first non-ejection drive on the remaining area of ​​the scan line SL2. Then, the control unit 8 performs a second non-ejection drive on the scan lines SL3 and SL4.

[0030] In this way, when the device 1 is operating, during periods other than printing processing, the first non-ejection drive and the second non-ejection drive cause the liquid in the specific nozzle 23 to vibrate at different scales, thereby suppressing thickening of the liquid while preventing excessive agitation of the liquid.

[0031] In this specification, "the magnitude of vibration is different" means, for example, that the agitation effect of the liquid in the specific nozzle 23 is different between the first non-ejection drive and the second non-ejection drive, and refers to the difference in the total surface area of ​​the liquid level L of the liquid in the specific nozzle 23 that is in contact with the outside air. In the second non-ejection drive, the total surface area of ​​the liquid level L that is in contact with the outside air is larger than in the first non-ejection drive. In order to make the magnitude of vibration different in this way, for example, it is sufficient to make the waveform of the voltage applied to the piezoelectric element 20 different (as will be described later with reference to FIG. 5).

[0032] Furthermore, in areas where the recording medium M and the head 2 do not overlap in the nozzle axis direction (for example, areas outside both sides of the recording medium M in the orthogonal direction P2), flushing may be performed as necessary to discharge a certain amount of liquid from the nozzle 22 to maintain a liquid state inside the nozzle 22. In FIG. 6, flushing is indicated by a round mark C3 that is larger than C1. The example shown in FIG. 6 shows how flushing is performed when the head 2 is positioned in an area outside both ends of the scanning lines SL1 to SL4 in the orthogonal direction P2.

[0033] 3, after executing S4, the control unit 8 determines whether all printing processes have been completed (S6). If the control unit 8 determines in S6 that all printing processes have not been completed (S6: No), the control unit 8 returns to step S2. If the control unit 8 determines in S6 that all printing processes have been completed (S6: Yes), the control unit 8 ends the flow.

[0034] In this way, if the waiting time T2 is within the reference time Tr, the time from reference time T0 to ejection start time T1 is relatively short, so performing the first non-ejection drive properly vibrates the liquid in the specific nozzle 23 and suppresses thickening of the liquid. On the other hand, if the waiting time T2 exceeds the reference time Tr, the time from reference time T0 to ejection start time T1 is relatively long, so performing the second non-ejection drive suppresses vibration of the liquid in the specific nozzle 23 to a smaller extent than when performing the first non-ejection drive. This suppresses thickening of the liquid due to long-term liquid vibration. As a result, regardless of the time from reference time T0 to ejection start time T1, thickening of the liquid in the specific nozzle 23 is suppressed, suppressing the occurrence of problems such as blurring of image formation locations, and ensuring appropriate execution of the printing process.

[0035] [Voltage drive waveform] Next, we will explain how to set the drive waveform of the voltage applied to the piezoelectric element 20 when performing the first non-ejection drive and the second non-ejection drive. Fig. 5 is a diagram showing the drive waveform of the voltage applied to the piezoelectric element 20 in Fig. 2. As shown in Fig. 5, the drive waveform includes a plurality of rectangular pulses arranged at a pulse period F2.

[0036] The rectangular pulse has a voltage value corresponding to an amplitude Hv based on a predetermined voltage (for example, 0 V). In the drive waveform, pulse groups each containing a predetermined number of rectangular pulses are repeatedly arranged with a group period F1 therebetween. The vibration of the liquid surface L in the specific nozzle 23 is adjusted by changing at least one of the amplitude Hv, pulse period F2, and group period F1. For example, the vibration of the liquid surface L per unit time can be reduced by at least one of decreasing the amplitude Hv, increasing the pulse period F2, and increasing the group period F1. Furthermore, the vibration of the liquid surface L per unit time can be reduced by at least one of increasing the amplitude Hv, decreasing the pulse period F2, and decreasing the group period F1. Based on the above methods, the first non-ejection drive and the second non-ejection drive are set.

[0037] 5 shows, as examples of drive waveforms, a first pattern waveform PT1 in which the amplitude Hv is set to a predetermined value, and a second pattern waveform PT2 in which the vibration applied to the liquid level L in the specific nozzle is different from that of the first pattern waveform PT1. In this example, the control unit 8 applies a voltage of either the first pattern waveform PT1 or the second pattern waveform PT2 in which the vibration applied to the liquid level L in the specific nozzle is different from that of the first pattern waveform PT1 to the piezoelectric element 20. The first pattern waveform PT1 inflicts greater vibration on the liquid level L and has a greater agitation force on the liquid in the specific nozzle 23 than the second pattern waveform PT2.

[0038] The first pattern waveform PT1 and the second pattern waveform PT2 may have different frequencies, for example. Alternatively, the first pattern waveform PT1 and the second pattern waveform PT2 may have different maximum amplitudes Hv. As an example, FIG. 5 shows the first pattern waveform PT1 whose maximum amplitude Hv is V1 and the second pattern waveform PT2 whose maximum amplitude Hv is V2, which is smaller than V1.

[0039] As described above, the device 1 of this embodiment includes a head 2 having a nozzle group 21 that ejects liquid onto a recording medium M, and a control unit 8 that controls the head 2 to perform a printing process based on print job information. The control unit 8 performs a wait time determination to determine whether a wait time T2, which is the time required from a predetermined reference time T0 for the printing process to an ejection start time T1 at which ejection of liquid from a specific nozzle 23 belonging to the nozzle group 21 begins, is within a predetermined reference time Tr. If the control unit 8 determines in the wait time determination that the wait time T2 is within the reference time Tr, it performs a first non-ejection drive that vibrates the liquid level L in the specific nozzle 23 with a vibration magnitude that prevents liquid from being ejected from the specific nozzle 23. If the control unit 8 determines in the wait time determination that the wait time T2 is not within the reference time Tr, it performs a second non-ejection drive that vibrates the liquid level L in the specific nozzle 23 with a vibration magnitude smaller than that of the first non-ejection drive.

[0040] According to the above configuration, in the second non-ejection drive, the liquid level L in the specific nozzle 23 can be vibrated at a smaller scale than in the first non-ejection drive, thereby preventing the liquid from volatilizing. Therefore, even if the period during which the liquid is not ejected from the specific nozzle 23 is relatively long, the thickening of the liquid in the nozzle 22 can be suppressed. Therefore, in the device 1 that suppresses the thickening of the liquid by slightly vibrating the liquid level L in the nozzle 22 during the non-ejection period during which the liquid is not ejected from the nozzle 22, the thickening of the liquid in the nozzle 22 can be suppressed even if the non-ejection period is long. This effect is particularly effective when using ink that is susceptible to drying, for example. Furthermore, suppressing the thickening of the liquid allows for appropriate printing processing, thereby improving print quality.

[0041] Furthermore, when flushing is performed in the device 1, the amount of liquid consumed by the operation can be reduced. Furthermore, since the number of flushing operations can be reduced, printing speed can be increased. Furthermore, the second non-ejection drive imposes a smaller driving load on the piezoelectric element 20 than the first non-ejection drive, which extends the life of the piezoelectric element 20 and suppresses the temperature rise of the head 2 when the device 1 is driven. Furthermore, the power consumption of the device 1 can be reduced.

[0042] Furthermore, in this embodiment, the nozzle group 21 includes a plurality of color nozzle groups that eject liquid of different colors. The control unit 8 performs standby time determination individually for a specific nozzle 23 that belongs to each of the plurality of color nozzle groups. With this configuration, it is possible to individually respond to each of the specific nozzles 23 that belong to the plurality of color nozzle groups and suppress thickening of the liquid in the specific nozzle 23. Therefore, for example, it is possible to appropriately suppress thickening of the liquid in a specific nozzle 23 that ejects liquid of a specific color.

[0043] Also, for example, it is possible to individually address nozzles 22 that eject liquid of a color that is used relatively frequently and nozzles 22 that eject liquid of a color that is used relatively less, and suppress thickening of the liquid in specific nozzles 23. This makes it possible to reduce the amount of liquid consumed by flushing throughout the device 1, while maintaining printing speed.

[0044] Furthermore, in the device 1 of this embodiment, the control unit 8 performs a wait time determination and a first non-ejection drive or a second non-ejection drive based on the results of the wait time determination, individually for each specific nozzle 23. As a result, even if a nozzle row is used infrequently in the direction P2 perpendicular to the conveyance direction P1 of the recording medium M, depending on the content of the printing process, it is possible to appropriately suppress thickening of the liquid in the specific nozzles 23 included in that nozzle row. Furthermore, because the first non-ejection drive or the second non-ejection drive is performed individually for each specific nozzle 23, it is possible to reduce the amount of liquid consumed by flushing throughout the device 1.

[0045] The device 1 of this embodiment also includes at least one piezoelectric element 20 that applies pressure to the liquid by an externally applied voltage so as to eject the liquid from the specific nozzle 23. The control unit 8 applies to the piezoelectric element 20 a voltage having either a first pattern waveform PT1 or a second pattern waveform PT2 that applies a different vibration to the liquid level L in the specific nozzle 23 than the first pattern waveform PT1. By configuring the voltage waveform applied to the piezoelectric element 20 to include both the first pattern waveform PT1 and the second pattern waveform PT2 in this way, thickening of the liquid in the specific nozzle 23 can be appropriately suppressed compared to when the voltage waveform includes only the first pattern waveform PT1.

[0046] Furthermore, the first pattern waveform PT1 of the present embodiment, as an example, applies greater vibration to the liquid surface L and greater stirring force to the liquid in the specific nozzle 23 than the second pattern waveform PT2. In this way, by using the second pattern waveform PT2 and the first pattern waveform PT1, which applies greater vibration to the liquid surface L and greater stirring force to the liquid in the specific nozzle 23 than the second pattern waveform PT2, these pattern waveforms PT1 and PT2 can be used appropriately to appropriately suppress thickening of the liquid in the specific nozzle 23 both when the standby time T2 is within the reference time Tr and when it is longer than the reference time Tr.

[0047] Furthermore, in this embodiment, during the second non-ejection drive, the control unit 8 selectively switches between the voltage of the first pattern waveform PT1 and the voltage of the second pattern waveform PT2 and applies them to the piezoelectric element 20. As a result, during the second non-ejection drive, the first pattern waveform PT1 prevents the liquid in the specific nozzle 23 from drying out, and the second pattern waveform PT2 allows the liquid in the specific nozzle 23 to recover from a dried state, thereby enabling the printing process to be carried out quickly.

[0048] In this embodiment, the first pattern waveform PT1 and the second pattern waveform PT2 have different frequencies. With this configuration, the first pattern waveform PT1 and the second pattern waveform PT2 can be easily configured by adjusting the frequencies of the first pattern waveform PT1 and the second pattern waveform PT2. Furthermore, by making the frequencies of the first pattern waveform PT1 and the second pattern waveform PT2 different, it is possible to prevent unnecessary resonance from occurring between the two waveforms PT1 and PT2.

[0049] The first pattern waveform PT1 and the second pattern waveform PT2 may have different maximum values ​​V1 and V2 of the amplitude Hv. This makes it possible to easily configure the first pattern waveform PT1 and the second pattern waveform PT2 by adjusting the maximum values ​​V1 and V2 of the amplitude Hv of the first pattern waveform PT1 and the second pattern waveform PT2. Below, the other embodiments will be described, focusing on the differences from the first embodiment.

[0050] (Second embodiment) In the second embodiment, the second non-ejection drive includes a suppression drive that suppresses vibration of the liquid level L in the specific nozzle 23 for a certain period of time before the ejection start time T1, and a pre-ejection drive that vibrates the liquid level L in the specific nozzle 23 at a magnitude greater than the vibration caused by the suppression drive after the suppression drive.

[0051] FIG. 7 is a plan view schematically illustrating the non-ejection drive of the device 1 according to the second embodiment. In FIG. 7, the suppression drive, the preceding drive, and the printing process executed by the device 1 are schematically illustrated using marks C4 to C6. For illustrative purposes, in FIG. 7, the vibration magnitude of the liquid in the specific nozzle 23 during the suppression drive is indicated by a round mark C4, the vibration magnitude of the liquid in the specific nozzle 23 during the preceding drive is indicated by an oval mark C5, and the ejection state of the liquid from the specific nozzle 23 during the printing process is indicated by a rectangular mark C6. As an example, the vibration magnitude of the liquid during the suppression drive is set to be the same as the vibration magnitude indicated by the round mark C2 in the first embodiment (see FIG. 6), but the magnitude of the vibration magnitude is not limited to this.

[0052] 7, the control unit 8 first executes the second non-ejection drive, and then executes the printing process. Specifically, during scanning of the head 2, the control unit 8 first executes suppression drive for the entire area of ​​the scanning line SL1 on the recording medium M transported in the transport direction P1. Then, the control unit 8 executes last-minute drive on the upstream side of the scanning line SL2 in the scanning direction. After this last-minute drive, the control unit 8 executes the printing process on the recording medium M. Thereafter, the control unit 8 executes the first non-ejection drive again on the scanning line SL2, for example, and then executes the second non-ejection drive on the scanning lines SL3 and SL4.

[0053] According to the second embodiment, during the second non-ejection drive, the suppression drive suppresses the thickening of the liquid in the specific nozzle 23, while the immediate prior drive promotes the circulation of the liquid in the specific nozzle 23 immediately prior to the printing process, making it easier to eject the liquid appropriately from the specific nozzle 23.

[0054] (Third embodiment) In this embodiment, during the first non-ejection drive, the control unit 8 applies a voltage of the first pattern waveform PT1 to the piezoelectric element 20, and during the second non-ejection drive, the control unit 8 applies a voltage of the second pattern waveform PT2 to the piezoelectric element 20. That is, in this embodiment, the pattern waveforms PT1 and PT2 are used separately for the first and second non-ejection drives.

[0055] As a result, during the first non-ejection drive, when the waiting time T2 is within the reference time Tr, it is possible to appropriately prevent the liquid in the specific nozzle 23 from drying out. Furthermore, during the second non-ejection drive, even when the waiting time T2 is longer than the reference time Tr, it is possible to prevent the liquid in the specific nozzle 23 from drying out excessively. As a result, whether the waiting time T2 is within or outside the reference time Tr, it is possible to appropriately prevent the liquid in the specific nozzle 23 from drying out.

[0056] When a printing process is executed immediately after the first non-ejection drive or the second non-ejection drive is performed, the drive waveform of the voltage applied to the piezoelectric element 20 may be modified immediately before the printing process so as to reduce vibrations of the liquid surface L of the liquid in the specific nozzle 23 caused by the non-ejection drive immediately before the printing process. This makes it possible to more reliably prevent, for example, the effects of the non-ejection drive from affecting the printing process immediately after the drive.

[0057] Furthermore, the nozzle group 21 of the head 2 may include at least one unused nozzle that is not used during the printing process. When performing non-ejection drive for such an unused nozzle, the first non-ejection drive and the second non-ejection drive can be selectively used.

[0058] The second non-ejection drive may also include a case where a pulse waveform is not actually applied. Even with this second non-ejection drive, excessive drying of the liquid in the specific nozzle 23 can be appropriately prevented, thereby suppressing thickening of the liquid. [Industrial Applicability]

[0059] The present disclosure can be applied to a liquid ejection device equipped with a head that ejects a liquid such as ink onto a recording medium. [Explanation of symbols]

[0060] Hv amplitude L Liquid level M Recording medium PT1 First pattern waveform PT2 Second pattern waveform T0 Reference time T1 Discharge start time T2 waiting time Tr reference time Maximum amplitude of V1 and V2 1 Liquid discharge device 3 heads 8 Control Unit 20 Piezoelectric element 21 nozzle group 23 Specific nozzle

Claims

1. a head having a nozzle group that ejects liquid onto a recording medium; a control unit that controls the head so as to perform printing processing based on print job information, The control unit executes a wait time determination to determine whether a wait time required from a reference time predetermined for the printing process to an ejection start time at which ejection of liquid from a specific nozzle belonging to the nozzle group begins is within a predetermined reference time; When it is determined in the waiting time determination that the waiting time is within the reference time, a first non-ejection drive is executed to vibrate the liquid surface of the liquid in the specific nozzle with a vibration of a magnitude that does not cause the liquid to be ejected from the specific nozzle; If the waiting time determination determines that the waiting time is not within the reference time, a liquid ejection device executes a second non-ejection drive that vibrates the liquid surface in the specific nozzle with a vibration of a smaller magnitude than the first non-ejection drive.

2. the nozzle group includes a plurality of color nozzle groups that eject liquids of different colors, The liquid ejection device according to claim 1 , wherein the control unit executes the standby time determination individually for the specific nozzle belonging to each of the plurality of color nozzle groups.

3. The liquid ejection device according to claim 1 , wherein the control unit executes the wait time determination and the first non-ejection drive or the second non-ejection drive based on the result of the wait time determination, individually for each of the specific nozzles.

4. further comprising at least one piezoelectric element that applies pressure to the liquid by an externally applied voltage so as to eject the liquid from the specific nozzle; The liquid ejection device described in claim 1, wherein the control unit applies to the piezoelectric element a voltage of either a first pattern waveform or a second pattern waveform that imparts a different vibration to the liquid surface in the specific nozzle than the first pattern waveform.

5. The liquid ejection device according to claim 4 , wherein the first pattern waveform applies a greater vibration to the liquid surface and a greater agitating force to the liquid in the specific nozzle than the second pattern waveform.

6. The liquid ejection device according to claim 5 , wherein the control unit selectively switches between the voltage of the first pattern waveform and the voltage of the second pattern waveform and applies the voltage to the piezoelectric element during the second non-ejection driving.

7. The control unit During the first non-ejection driving, a voltage of the first pattern waveform is applied to the piezoelectric element; The liquid ejection device according to claim 5 , wherein a voltage of the second pattern waveform is applied to the piezoelectric element during the second non-ejection driving.

8. The liquid ejection device according to claim 4 , wherein the first waveform pattern and the second waveform pattern have different frequencies.

9. The liquid ejection device according to claim 4 , wherein the first pattern waveform and the second pattern waveform have different maximum amplitude values.

10. The second non-ejection drive is suppression drive for suppressing vibration of the liquid surface in the specific nozzle for a certain period before the ejection start time; The liquid ejection device according to claim 1 , further comprising: a pre-drive after the suppression drive, which vibrates the liquid surface in the specific nozzle at a magnitude greater than the vibration caused by the suppression drive.

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