Droplet discharge device and method for driving droplet discharge device

Abstract

A droplet discharge device 1 is provided with: an acquisition unit that acquires a distance L between a recording medium M and a droplet discharge head 23; an adjustment unit that expands or contracts a pulse width of a common drive waveform P00 on the basis of the distance L; a determination unit that selects one or more drive pulses corresponding to sizes of droplets from the common drive waveform P01 adjusted by the adjustment unit to determine a discharge drive pulse; and a discharge control unit that causes the nozzles 21 to discharge droplets of a plurality of sizes using a plurality of discharge drive pulses determined by the determination unit.

Description

Droplet ejection device and method for driving the droplet ejection device

[0001] The present invention relates to a droplet ejection device and a method for driving the droplet ejection device.

[0002] 2. Description of the Related Art Conventionally, there is known a droplet ejection device that ejects droplets onto a recording surface of a recording medium to record an image. In such a droplet ejection device, droplets are ejected at appropriate timing from nozzles of a droplet ejection head based on image data.

[0003] As an example of such a droplet ejection device, Patent Document 1 describes an invention in which droplets of different sizes ejected in response to a plurality of drive pulses are aligned in their landing positions.

[0004] Japanese Patent Application Laid-Open No. 2007-144659

[0005] However, droplets of different sizes experience different air resistance, which results in differences in ejection speed. Therefore, when the media gap widens, the landing position varies depending on the difference in ejection speed. Patent Document 1 does not mention or suggest how to align the landing positions when the media gap changes.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a droplet ejection device and a method for driving a droplet ejection device that can align the landing positions of droplets of different sizes even if the media gap changes.

[0007] In order to solve the above problems, the invention described in claim 1 is a droplet ejection device having a droplet ejection head that performs a recording operation on a recording medium by ejecting droplets of multiple sizes from a nozzle using a common drive waveform including multiple drive pulses that exist in a drive cycle, and is equipped with an acquisition unit that acquires the distance between the recording medium and the droplet ejection head, an adjustment unit that expands or contracts the pulse width of the common drive waveform based on the distance, a determination unit that selects one or more drive pulses according to the droplet size from the common drive waveform adjusted by the adjustment unit to determine an ejection drive pulse, and an ejection control unit that ejects droplets of multiple sizes from the nozzle using the multiple ejection drive pulses determined by the determination unit.

[0008] The invention described in claim 2 is a droplet ejection device described in claim 1, which is provided with a selection unit that selects the waveform rank based on a table in which the distance and waveform rank are associated, and the adjustment unit extends or contracts the pulse width of the common drive waveform based on the waveform rank.

[0009] A third aspect of the present invention is the droplet ejection device according to the second aspect, wherein the adjustment section expands or contracts the amplitude width of the common drive waveform based on the waveform rank.

[0010] A fourth aspect of the present invention is the droplet ejection device according to the third aspect, wherein the adjustment section extends or contracts the plurality of drive pulses at an equal rate.

[0011] A fifth aspect of the present invention is the droplet ejection device according to any one of the first to fourth aspects, wherein the common drive waveform has an amplitude width of at least 18 V / μs for switching between droplets of different sizes.

[0012] A sixth aspect of the present invention is the droplet ejection device according to any one of the first to fourth aspects, wherein the ejection drive pulses include at least four or more drive pulses.

[0013] The invention described in claim 7 is a method for driving a droplet ejection device equipped with a droplet ejection head that performs a recording operation on a recording medium by ejecting droplets of multiple sizes from a nozzle using a common drive waveform including multiple drive pulses that exist in a drive cycle, and includes an acquisition step of acquiring the distance between the recording medium and the droplet ejection head; an adjustment step of expanding or contracting the pulse width of the common drive waveform based on the distance; a determination step of selecting one or more drive pulses corresponding to the droplet size from the multiple drive pulses in the common drive waveform adjusted in the adjustment step to determine an ejection drive pulse; and an ejection control step of ejecting droplets of multiple sizes from the nozzle using the multiple ejection drive pulses determined in the determination step.

[0014] According to the present invention, the landing positions of droplets of different sizes can be aligned even if the media gap changes.

[0015] 1 is a perspective view of an inkjet recording apparatus; FIG. 2 is a block diagram of an inkjet recording apparatus; FIG. 3 is a schematic diagram of pressure chambers and nozzles as viewed in the axial direction of the nozzles, showing changes in the pressure chambers in response to drive pulses; FIG. 4 is a flowchart showing a driving method of an inkjet recording apparatus according to the present embodiment; FIG. 5 is a diagram showing a media gap; FIG. 6 is a diagram showing a correspondence table between media gaps and length ranks; FIG. 7 is a diagram showing one common drive waveform before adjustment control is performed; FIG. 8 is a diagram showing multiple common drive waveforms for which adjustment control according to length rank has been performed; FIG. 9 is a graph of droplet ejection speed when the amplitude width of the waveform for switching between different sizes of droplets is 12 V / μs; FIG. 10 is a graph of droplet ejection speed when the amplitude width of the waveform for switching between different sizes of droplets is 14 V / μs; FIG. 11 is a graph of droplet ejection speed when the amplitude width of the waveform for switching between different sizes of droplets is 18 V / μs; FIG. 12 is a graph of the difference in ejection speed between small droplets and large droplets for each amplitude width of the waveform for switching between different sizes of droplets; and FIG. 13 is a graph of droplet ejection speed when three drive pulses are used to eject one dot. 1 is a graph showing the droplet ejection speed when four drive pulses are used to eject one dot. 2 is a graph showing the difference in ejection speed between small droplets and medium droplets for each number of drive pulses used to eject one dot. 3 is a diagram showing a plurality of common drive waveforms for which adjustment control according to amplifier rank has been performed.

[0016] An embodiment of the present invention will be described below with reference to the accompanying drawings. The following description is for illustrating an embodiment of the present invention and is not intended to limit the present invention.

[0017] [Overall Configuration of Inkjet Recording Apparatus] First, as a droplet ejection apparatus according to this embodiment, an example of the configuration of an inkjet recording apparatus 1 equipped with an inkjet head 23 that is a droplet ejection head will be disclosed.

[0018] Fig. 1 is a perspective view of an inkjet recording apparatus 1. Fig. 2 is a block diagram showing the functional configuration of the inkjet recording apparatus 1. The inkjet recording apparatus 1 includes, for example, a conveying unit 10, a recording operation unit 20, a cleaning unit 30, a control unit 40, a storage unit 50, a communication unit 60, an operation reception unit 70, a display unit 80, and a power supply unit 90.

[0019] (Transport Unit) The transport unit 10 moves the recording medium M on which an image is to be recorded. The recording medium M is not particularly limited. For example, the recording medium M may be a piece of fabric or multiple sheets of paper that are continuous in the transport direction. The transport unit 10 positions the recording medium M opposite the recording range of the recording operation unit 20.

[0020] The conveying section 10 includes a driving roller 11, a conveying belt 12, a driven roller 13, a conveying motor 14, a pressure roller 15, a peeling roller 16, and the like.

[0021] The conveyor belt 12 is endless and is stretched between a drive roller 11 and a driven roller 13. The conveyor belt 12 moves in a circular motion in accordance with the rotation of the drive roller 11. As the conveyor belt 12 moves in a circular motion, the recording medium M placed on the conveying surface moves in the conveying direction in FIG.

[0022] The driven roller 13 rotates in accordance with the movement of the conveyor belt 12. The conveyor motor 14 rotates the drive roller 11 at a rotation speed according to a control signal from the control unit 40. The pressure roller 15 removes any lifting from the loading surface, such as wrinkles. Specifically, the pressure roller 15 presses the recording medium M on the loading surface of the conveyor belt 12 against the loading surface. The peeling roller 16 peels the recording medium M from the transport surface and sends it to a post-processing device. Specifically, the peeling roller 16 pulls the recording medium M from the conveyor belt 12 with a predetermined pressure.

[0023] (Recording Operation Unit) The recording operation unit 20 ejects ink droplets onto the recording medium M to record an image. The recording operation unit 20 includes a plurality of head units 20a arranged along the transport direction of the recording medium M. Each head unit 20a includes a plurality of inkjet heads 23 that are arranged in a predetermined pattern and eject ink droplets from openings. Each inkjet head 23 includes nozzles 21, piezoelectric elements 22, etc.

[0024] The recording operation unit 20 also includes a head driving unit 24. The head driving unit 24 outputs driving pulses that expand or contract each piezoelectric element 22 under the control of the control unit 40. As shown in Fig. 3, the piezoelectric elements 22 deform due to the driving pulses, thereby deforming ink flow paths (pressure chambers) 25 that supply ink to the nozzles 21. The ink in the ink flow paths 25 is subjected to pressure fluctuations due to the deformation, and is ejected from the nozzles 21.

[0025] (Cleaning Unit) The cleaning unit 30 cleans the nozzle surface N (see FIG. 5 ) on which the openings of the nozzles 21 of the inkjet head 23 are arranged. The cleaning unit 30 includes, for example, a wiping member 32 that wipes off ink and solidified ink adhering to the nozzle surface N, and a driving unit 31 that operates the wiping member 32. The wiping member 32 is not particularly limited, but may be, for example, a nonwoven fabric that absorbs ink, or a resin member on a blade that scrapes off solid matter.

[0026] (Control Unit) The control unit 40 is a processor that controls the overall operation of the inkjet recording apparatus 1. The control unit 40 includes, for example, a CPU 41 (Central Processing Unit) and a RAM 42 (Random Access Memory). The CPU 41 performs calculations and performs various control processes for the inkjet recording apparatus 1. The RAM 42 provides the CPU 41 with working memory space and stores temporary data. The control unit 40 functions as an adjustment unit, a determination unit, and an ejection control unit by executing predetermined programs.

[0027] Furthermore, the control unit 40 functions as an adjustment unit to adjust the waveform of the common drive waveform P00 (see FIG. 7A). Details of the common drive waveform P00 and adjustment control will be described later.

[0028] Furthermore, the control unit 40 functions as a determination unit and generates a waveform selection signal. The waveform selection signal selects a drive pulse corresponding to the dot size from the common drive waveform P01 (see FIG. 7B) and determines an ejection drive pulse for ejecting ink from the nozzles 21.

[0029] Specifically, the waveform selection signal is a negative logic pulse signal. When the control unit 40 performs a logical OR operation between the negative logic pulse signal and the common drive waveform P01, drive pulses other than the selected drive pulse are removed, and the ejection drive pulse is determined.

[0030] Furthermore, the control unit 40, as an ejection control unit, controls the head drive unit 24 to output the determined ejection drive pulse to the piezoelectric element 22. Then, the control unit 40 causes the nozzle 21 to eject ink.

[0031] (Storage Unit) The storage unit 50 stores image data to be recorded, processing data for the image data, and other setting data and programs. The image data is stored, for example, in a dynamic random access memory (DRAM) that is capable of temporary large-capacity storage and high-speed output. The setting data and programs are stored in a non-volatile memory such as a flash memory and / or a hard disk drive (HDD). This configuration makes it possible to store setting data even when the power supply to the inkjet recording apparatus 1 is stopped.

[0032] The storage unit 50 also stores a common drive waveform P00 before adjustment control by the control unit 40 and a common drive waveform P01 after adjustment control. The storage unit 50 also stores a correspondence table T (see FIG. 6 ) between media gaps and length ranks (waveform ranks) that is necessary for the control unit 40 to execute adjustment control.

[0033] (Communication Unit) The communication unit 60 controls data transmission and reception with external devices in accordance with a predetermined communication standard, for example, TCP / IP (Transmission Control Protocol / Internet Protocol). The communication unit 60 may be connected to a LAN (Local Area Network) and connectable to the external Internet via a router. The communication unit 60 may also be directly connectable to peripheral devices via a USB (Universal Serial Bus) cable connected to a USB terminal.

[0034] (Operation Receiving Unit) The operation receiving unit 70 receives input operations by the user and outputs the received content as an input signal to the control unit 40. The operation receiving unit 70 includes, for example, a touch panel or a push button switch. If the operation receiving unit 70 is a touch panel, it may be positioned so as to overlap the display screen of the display unit 80, and the operation content may be specified in synchronization with the display content on the display screen.

[0035] (Display Unit) The display unit 80 displays status and selection menus to the user. The display unit 80 has, for example, a display screen and an indicator (lamp). The indicator is used, for example, to indicate the presence or absence of power supply or operational abnormalities using an LED (Light Emitting Diode) lamp. The display unit 80 also has, for example, a liquid crystal display, and can display various characters and figures on the display screen in a dot matrix format.

[0036] (Power Supply Unit) The power supply unit 90 supplies power from a power source to the inkjet recording apparatus 1 .

[0037] [Driving Process During Recording Operation] Next, the driving process of the inkjet head 23 during recording operation will be described with reference to Fig. 4. The control unit 40 of the inkjet recording apparatus 1 executes the driving process of the inkjet head 23 when it receives a print instruction, for example, through a user's operation on the operation reception unit 70.

[0038] (Media Gap Acquisition Step) First, the control unit 40 acquires the media gap (step S1). The media gap refers to the distance L from the nozzle surface N of the inkjet head 23 to the image formation surface of the recording medium M, as shown in FIG.

[0039] Specifically, for example, the storage unit 50 stores in advance the media gap for each type of recording medium M. Therefore, the control unit 40 acquires the media gap based on the type of recording medium M included in the print command. Alternatively, a device (distance sensor) capable of measuring the media gap from the recording medium M may be provided upstream of the inkjet head 23 in the transport direction. The control unit 40 then acquires the media gap based on the measurement data of that device. The control unit 40 functions as an acquisition unit that acquires the distance L between the recording medium M and the droplet ejection head 23 through the control described above.

[0040] (Length Rank Selection Step) Next, the control unit 40 selects a length rank (step S2).

[0041] As described above, the storage unit 50 stores a correspondence table T between media gaps and length ranks. Therefore, the control unit 40 selects a corresponding length rank based on the media gap acquired in step S1. Through this control, the control unit 40 functions as a selection unit that selects a waveform rank based on the media gap.

[0042] An example of the correspondence table T is shown in Fig. 6. As shown in Fig. 6, in the correspondence table T, the length rank is associated with the larger media gap. Therefore, in the adjustment control described later, the pulse width is adjusted to be extended as the media gap increases.

[0043] The correspondence table T can be created by, for example, ejecting droplets of different sizes while changing the media gap and length rank, and recording the media gap and length rank at which the ejection positions are aligned.

[0044] (Common Drive Waveform Adjustment Step) After selecting the Length rank, the control unit 40 executes adjustment control to adjust the waveform of the common drive waveform P00 in accordance with the selected Length rank (step S3).

[0045] 7A and 7B, the control unit 40 expands or contracts the pulse width of each drive waveform of the common drive waveform P00 in the time direction by the same expansion or contraction rate depending on the Length rank, while leaving the drive frequency unchanged. In this way, the control unit 40 adjusts the common drive waveform P00 to the common drive waveform P01. Note that in FIGS. 7A and 7B, the common drive waveform P01 when the Length rank is 12 is not modified from the common drive waveform P00, but this case is also considered to have been subjected to adjustment control.

[0046] The subsequent operations are the same as those of the conventional inkjet recording apparatus 1. That is, the control unit 40 generates a waveform selection signal for forming dots of a desired size (step S4). Then, the control unit 40 determines the ejection drive pulse by selecting one or more drive pulses to be used for ejecting ink from the group of drive pulses by taking the logical sum of the common drive waveform P01 and the waveform selection signal (step S5).

[0047] 7B , when the length rank is 8 and small droplets are to be ejected, the control unit 40 performs a logical sum with the common drive waveform P01 in the range indicated by arrow A1. When medium droplets are to be ejected, the control unit 40 performs a logical sum with the common drive waveform P01 in the range indicated by arrow A2. When large droplets are to be ejected, the control unit 40 performs a logical sum with the common drive waveform P01 in the range indicated by arrow A3.

[0048] Then, the control unit 40 causes the head driving unit 24 to apply the selected driving pulse to the piezoelectric element 22, thereby ejecting ink from the nozzle 21 (step S6). The control unit 40 then repeatedly executes steps S4 to S6 until image formation according to the acquired print instruction is completed.

[0049] Next, the results of evaluation of preferred configurations of the present invention will be described. Note that, while the present invention will be specifically described below based on examples, the present invention is not limited to the following specific examples. In the following examples, droplets of less than 10 pl are defined as small droplets, those of 10 pl or more but less than 20 pl as medium droplets, and those of more than 20 pl as large droplets.

[0050] Example 1 Relationship between the gradient of the waveform at which droplet size changes and the droplet ejection speed The amplitude width of the waveform at which different droplet sizes change in the common drive waveform P01 was appropriately set by the control of the control unit 40. In addition, in this inkjet recording apparatus 1, the droplet ejection speed was measured while changing the length rank for each droplet size.

[0051] FIG. 8A is a graph showing the relationship between the length rank and the droplet ejection speed when the amplitude width of the waveform for switching between different sizes of droplets is set to 12 V / μs. FIG. 8B is a graph showing the relationship between the length rank and the droplet ejection speed when the amplitude width of the waveform for switching between different sizes of droplets is set to 14 V / μs. FIG. 8C is a graph showing the relationship between the length rank and the droplet ejection speed when the amplitude width of the waveform for switching between different sizes of droplets is set to 18 V / μs. In FIGS. 8A to 8C, the horizontal axis represents the length rank, and the vertical axis represents the droplet ejection speed. FIG. 8D is a graph showing the difference in droplet ejection speed between small droplets and large droplets for each length rank at each amplitude width, based on FIGS. 8A to 8C. In FIG. 8D, the horizontal axis represents the length rank, and the vertical axis represents the difference in droplet ejection speed.

[0052] As can be seen from a comparison of Figures 8A, 8B, and 8C, or from Figure 8D, when the amplitude width of the waveform for switching between droplets of different sizes is 18 V / μs or more, a difference in droplet speed occurs when droplets of different sizes are ejected.

[0053] Example 2: Relationship between the number of drive pulses for ejecting one dot of droplets and the ejection speed for each droplet size Under the control of the control unit 40, the inkjet recording device 1 was set to eject one dot of droplets using three drive pulses. Then, in this inkjet recording device 1, the droplet ejection speed was measured while changing the length rank for each droplet size. Similarly, the inkjet recording device 1 was set to eject one dot of droplets using four drive pulses. Then, the droplet ejection speed was measured while changing the length rank for each droplet size.

[0054] Fig. 9A is a graph of the droplet ejection speed when one dot of droplet is ejected using three drive pulses. Fig. 9B is a graph of the droplet ejection speed when one dot of droplet is ejected using four drive pulses. In Figs. 9A and 9B, the horizontal axis represents the length rank, and the vertical axis represents the droplet ejection speed. Fig. 9C is a graph showing the difference in droplet ejection speed between small and medium droplets for each length rank at each number of drive pulses, based on Figs. 9A and 9B. In Fig. 9C, the horizontal axis represents the length rank, and the vertical axis represents the difference in droplet ejection speed.

[0055] As can be seen from a comparison between FIGS. 9A and 9B, or from FIG. 9C, when one dot of droplets is ejected using four or more drive pulses, a difference in droplet speed occurs when droplets of different sizes are ejected.

[0056] [Summary] As described above in Examples 1 and 2, when the amplitude width of the waveform for switching between droplets of different sizes is 18 V / μs or more, or when four or more drive pulses are used to eject one dot of droplet, differences in ejection speed occur between different droplet sizes. This makes it easier for landing variations to occur. However, with the inkjet recording apparatus 1 according to this embodiment, it is possible to eliminate such differences in ejection speed between droplet sizes by selecting the length rank.

[0057] Effects of the Embodiment As described above, the inkjet recording apparatus 1 according to this embodiment includes an acquisition unit that acquires the distance L between the recording medium M and the inkjet head 23. The inkjet recording apparatus 1 also includes an adjustment unit that expands or contracts the pulse width of the common drive waveform P00 based on the distance L. The inkjet recording apparatus 1 also includes a determination unit that determines an ejection drive pulse by selecting one or more drive pulses from the adjusted common drive waveform P01 according to the droplet size. The inkjet recording apparatus 1 also includes an ejection control unit that causes the nozzles 21 to eject droplets of multiple sizes using the multiple ejection drive pulses determined by the determination unit. In this way, even if the media gap of the recording medium M changes, the inkjet recording apparatus 1 adjusts the common drive waveform P00 in response to the change. Therefore, the inkjet recording apparatus 1 according to this embodiment can align the landing positions of droplets of different sizes even if the media gap of the recording medium M changes.

[0058] In the inkjet recording apparatus 1 according to this embodiment, the adjustment unit expands or contracts the plurality of drive pulses at equal rates. The determination unit determines the ejection drive pulses for ejecting droplets of a plurality of sizes from one common drive waveform. This configuration allows the adjustment unit to precisely adjust the pulse width and amplitude of the common drive waveform P00.

[0059] Furthermore, in the inkjet recording apparatus 1 according to this embodiment, the amplitude width of the waveform of the common drive waveform P00 at least when switching between different droplet sizes is 18 V / μs or more. Furthermore, in the inkjet recording apparatus 1 according to this embodiment, the ejection drive pulse includes at least four drive pulses. As described above, in this configuration, the difference in ejection speed between droplet sizes becomes greater, but the inkjet recording apparatus 1 according to this embodiment can align the landing positions.

[0060] [Other Configurations] While the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above-described embodiments. Of course, the present invention can be modified in various ways within the scope of the invention described in the claims and their equivalents.

[0061] In the above example, the impact position is adjusted by changing only the pulse width of the common drive waveform P00, but this is not limiting. For example, as shown in Figure 10, the impact position may be adjusted by changing the amplitude width (drive voltage value) of the common drive waveform P00.

[0062] This change is based on the amplifier rank (waveform rank) corresponding to the media gap. However, the amount of change in impact position caused by changing the amplitude width is small. Therefore, it is preferable to change the pulse width of the common drive waveform P00 and then change the drive voltage value if fine adjustment is required.

[0063] Furthermore, although the above example illustrates a case where the landing position is adjusted for one inkjet head 23, the present invention is also applicable to an inkjet recording apparatus 1 that includes a plurality of inkjet heads 23. In this configuration, different correspondence tables T may be set for the plurality of inkjet heads 23, respectively, in accordance with individual differences between the inkjet heads 23.

[0064] The droplet ejection speed also changes depending on the physical properties of the ink being ejected, such as viscosity, surface tension, and density. For example, in the case of ink containing large particles with a low specific gravity, the density is low, and the degree of decrease in the ejection speed increases. For this reason, a correspondence table T may be provided for each physical property of the ink being ejected.

[0065] In the above description, the control unit 40 acquires the length rank from the media gap by referring to the correspondence table T and adjusts the common drive waveform P00, but this is not limiting. For example, the control unit 40 may adjust the common drive waveform P00 from the media gap based on a predetermined function.

[0066] Although the above example illustrates a configuration in which the control unit 40 automatically acquires the media gap and length rank, the present invention is not limited to this. For example, the user may operate the operation reception unit 70 to receive input of the media gap, the range of droplet sizes, and the length rank.

[0067] 7B illustrates an example in which the control unit 40 performs a logical OR operation with the waveform selection signal in accordance with the droplet size, starting from the rear end of the common drive waveform P01 in the time direction, but this is not limiting. For example, the control unit 40 may perform a logical OR operation with the waveform selection signal in accordance with the droplet size, starting from the front end of the common drive waveform P01 in the time direction. Alternatively, the control unit 40 does not need to perform a logical OR operation with the waveform selection signal based on any position of the common drive waveform P01.

[0068] Furthermore, although the droplet ejection device has been described above as the inkjet recording device 1, the droplets ejected by the droplet ejection device are not limited to ink droplets. For example, the droplet ejection device may eject droplets of various functional liquids such as a pretreatment agent.

[0069] The present invention can be used in a droplet ejection device and a method for driving a droplet ejection device that can align the landing positions of droplets of different sizes even if the media gap changes.

[0070] REFERENCE SIGNS LIST 1 Inkjet recording device (droplet ejection device) 21 Nozzle 23 Inkjet head (droplet ejection head) 40 Control unit (acquisition unit, selection unit, adjustment unit, determination unit, ejection control unit) L Distance (media gap, distance between recording medium and droplet ejection head) M Recording medium T Correspondence table (table) P00 Common drive waveform P01 Common drive waveform (adjusted common drive waveform)

Claims

1. A droplet ejection device equipped with a droplet ejection head that performs a recording operation on a recording medium by ejecting droplets of multiple sizes from a nozzle using a common drive waveform including multiple drive pulses that exist in a drive cycle, the droplet ejection device comprising: an acquisition unit that acquires the distance between the recording medium and the droplet ejection head; an adjustment unit that expands or contracts the pulse width of the common drive waveform based on the distance; a determination unit that selects one or more drive pulses corresponding to the size of the droplet from the common drive waveform adjusted by the adjustment unit to determine an ejection drive pulse; and an ejection control unit that ejects droplets of multiple sizes from the nozzle using the multiple ejection drive pulses determined by the determination unit.

2. A droplet ejection device as described in claim 1, further comprising a selection unit that selects the waveform rank based on a table in which the distance and waveform rank are associated, and the adjustment unit expands or contracts the pulse width of the common drive waveform based on the waveform rank.

3. The droplet ejection device according to claim 2, wherein the adjustment section expands or contracts the amplitude width of the common drive waveform based on the waveform rank.

4. The droplet ejection device according to claim 3, wherein the adjustment section extends or contracts the plurality of drive pulses at an equal rate.

5. A droplet ejection device according to any one of claims 1 to 4, wherein the common drive waveform has an amplitude width of at least 18 V / μs for switching between droplets of different sizes.

6. A droplet ejection device according to any one of claims 1 to 4, wherein the ejection drive pulse includes at least four or more drive pulses.

7. A method for driving a droplet ejection device equipped with a droplet ejection head that performs a recording operation on a recording medium by ejecting droplets of multiple sizes from a nozzle using a common drive waveform including multiple drive pulses that exist in a drive cycle, the method comprising: an acquisition step of acquiring a distance between the recording medium and the droplet ejection head; an adjustment step of expanding or contracting a pulse width of the common drive waveform based on the distance; a determination step of selecting one or more drive pulses corresponding to the size of the droplet from the multiple drive pulses in the common drive waveform adjusted in the adjustment step to determine an ejection drive pulse; and an ejection control step of ejecting droplets of multiple sizes from the nozzle using the multiple ejection drive pulses determined in the determination step.

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