Liquid discharge device

Abstract

To provide a liquid discharge device which suppresses lowering of ink discharge stability.SOLUTION: In a liquid discharge device, a driving signal includes a first common driving signal having a plurality of discharge pulses corresponding to a plurality of droplets combined by the time when the droplets land on a medium; a discharge element of an initial first discharge pulse has a potential changed to a reference potential from a first potential, and is connected to a first connection element; a filling element of a last discharge pulse has a potential changed to a second potential from a potential equal to or more than the reference potential; a discharge element of the last discharge pulse has a potential changed to a third potential from the second potential; the last discharge pulse has a damping element for weakening pressure variation in a pressure chamber by the change of the potential after the discharge element of the last discharge pulse; the reference potential is positioned between the first potential and the third potential; the reference potential is positioned between the second potential and the third potential; and a period from the start of the filling element of the last discharge pulse to the start of the discharge element of the last discharge pulse is 0.3 TC or more and less than 0.5 TC.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection device. [Background technology]

[0002] Liquid ejection devices, such as inkjet printers, generally have a liquid ejection head that ejects liquid such as ink. The liquid ejection head includes nozzles that eject the liquid onto a medium, pressure chambers that communicate with the nozzles, and drive elements, such as piezoelectric elements, that apply pressure fluctuations to the liquid in the pressure chambers in response to drive signals.

[0003] The liquid ejection device described in Patent Document 1 discloses a technology in which multiple liquid droplets ejected from a nozzle are combined and landed on the medium, for example, in order to increase the size of dots formed on a printing medium.

[0004] Specifically, a droplet is ejected from a nozzle by driving the piezoelectric element in response to a change in drive voltage Va. After a predetermined period of time has passed since the ejection of this droplet, another droplet is ejected from the nozzle by driving the piezoelectric element in response to a change in drive voltage Vb. Then, the other droplet ejected later catches up with the droplet ejected earlier, and the combined liquid lands on the medium. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-140761 Summary of the Invention [Problem to be solved by the invention]

[0006] FIG. 28 is a diagram showing a conventional drive signal Comx. The drive signal Comx shown in FIG. 28 includes multiple ejection pulses Px within one drive period Tux. Ink droplets are ejected based on each ejection pulse Px, and a combined droplet formed by combining multiple droplets lands on a medium. Each ejection pulse Px included in the drive signal Comx shown in FIG. 28 includes a waveform that changes potential from a reference potential E0x to a minimum potential Emin, then changes potential to a maximum potential Emax, and returns to the reference potential E0x. Each ejection pulse Px has a so-called pull-push-pull waveform.

[0007] However, in the case of the drive signal Comx, if the interval between multiple ejection pulses Px is narrowed in order to shorten the ink ejection interval through high-speed driving, there is a problem that a sufficient period cannot be secured for damping the vibration of the ink remaining in the nozzle after ejection, making it difficult to eject ink stably. [Means for solving the problem]

[0008] In order to solve the above problems, a liquid ejection device according to a preferred aspect of the present disclosure includes an ejection section having a nozzle that ejects liquid to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates a pressure fluctuation in the liquid in the pressure chamber when a drive signal is supplied, and a drive signal generation section that generates the drive signal, wherein the drive signal includes a first common drive signal having a plurality of ejection pulses that correspond to a plurality of droplets that combine before landing on the medium, and the plurality of ejection pulses each have a filling element that drives the drive element to generate a negative pressure in the pressure chamber by changing a potential, and an ejection element that drives the drive element to generate a positive pressure in the pressure chamber by changing a potential, thereby ejecting a droplet from the nozzle, and The ejection element of the first ejection pulse changes potential from a first potential to a reference potential and connects to a first connection element, the filling element of the last ejection pulse of the plurality of ejection pulses changes potential from a potential equal to or higher than the reference potential to a second potential, and the ejection element of the last ejection pulse changes potential from the second potential to a third potential, the last ejection pulse has a damping element that attenuates pressure fluctuations in the pressure chamber by changing potential after the ejection element of the last ejection pulse, the reference potential is located between the first potential and the third potential, and the reference potential is located between the second potential and the third potential, the period from the start of the filling element of the last ejection pulse to the start of the ejection element of the last ejection pulse is greater than or equal to 0.3TC and less than 0.5TC, where TC indicates the natural vibration period of the ejection section. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of a liquid ejection device according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing the electrical configuration of the liquid ejection device according to the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view showing an example of a head chip. [Figure 4] FIG. 2 is a diagram for explaining a switching circuit. [Figure 5]FIG. 3 is a diagram for explaining a drive signal used in the first embodiment. [Figure 6] FIG. 4 is a diagram showing a first dot drive signal in the first embodiment. [Figure 7] 10A and 10B are diagrams illustrating a combined droplet obtained by combining a plurality of droplets sequentially ejected from a nozzle. [Figure 8] FIG. 10 is a diagram showing a residual vibration signal. [Figure 9] FIG. 6 is a diagram showing a second dot drive signal in the first embodiment. [Figure 10] FIG. 10 is a diagram showing a third dot drive signal in the first embodiment. [Figure 11] FIG. 10 is a diagram showing a first dot drive signal in a first modified example. [Figure 12] FIG. 10 is a diagram showing a first dot drive signal in a second modified example. [Figure 13] FIG. 10 is a diagram for explaining a drive signal used in the second embodiment. [Figure 14] FIG. 10 is a diagram showing a second dot drive signal in the second embodiment. [Figure 15] FIG. 10 is a diagram showing a third dot drive signal in the second embodiment. [Figure 16] FIG. 10 is a diagram for explaining a drive signal used in the third embodiment. [Figure 17] FIG. 11 is a diagram showing a first dot drive signal in the third embodiment. [Figure 18] FIG. 11 is a diagram showing a second dot drive signal in the third embodiment. [Figure 19] FIG. 11 is a diagram showing a third dot drive signal in the third embodiment. [Figure 20] FIG. 10 is a diagram for explaining a drive signal used in the fourth embodiment. [Figure 21] FIG. 11 is a diagram showing a first dot drive signal in the fourth embodiment. [Figure 22] FIG. 13 is a diagram showing a second dot drive signal in the fourth embodiment. [Figure 23] FIG. 10 is a diagram for explaining a drive signal of a reference example. [Figure 24]FIG. 10 is a diagram showing a first dot drive signal of a reference example. [Figure 25] FIG. 10 is a diagram illustrating a second dot drive signal of a reference example. [Figure 26] FIG. 10 is a diagram illustrating a third dot drive signal of a reference example. [Figure 27] FIG. 10 is a diagram showing a first dot drive signal in another reference example. [Figure 28] FIG. 1 is a diagram illustrating a conventional driving signal. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0011] In the following description, the mutually intersecting X-axis, Y-axis, and Z-axis will be used as appropriate. In the following description, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. The opposite directions along the Z-axis are the Z1 direction and the Z2 direction.

[0012] Typically, the Z axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°.

[0013] A. First embodiment A1. Overall configuration of the liquid ejection device Fig. 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100 according to a first embodiment. The liquid ejection device 100 in Fig. 1 is an inkjet printing device that ejects liquid such as ink as droplets onto a medium M. The medium M is, for example, printing paper. Note that the medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

[0014] As shown in FIG. 1, the liquid ejection device 100 includes a liquid container 10, a control unit 20, a transport mechanism 30, a moving mechanism 40, and a head 50.

[0015] The liquid container 10 stores ink. Specific examples of the liquid container 10 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. The type of ink stored in the liquid container 10 is arbitrary.

[0016] The control unit 20 controls the operation of each element of the liquid ejection device 100. The control unit 20 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory.

[0017] The transport mechanism 30 transports the medium M in the Y1 direction under the control of the control unit 20. The movement mechanism 40 reciprocates the head 50 along the X axis under the control of the control unit 20. The movement mechanism 40 has a substantially box-shaped carriage 41 that houses the head 50, and an endless transport belt 42 to which the carriage 41 is fixed. Note that the number of heads 50 mounted on the carriage 41 is not limited to one, and may be multiple. In addition to the head 50, the carriage 41 may also be equipped with the aforementioned liquid container 10.

[0018] Under the control of the control unit 20, the head 50 ejects ink supplied from the liquid container 10 from each of the multiple nozzles onto the medium M. This ejection is performed in parallel with the transport of the medium M by the transport mechanism 30 and the reciprocating movement of the head 50 by the movement mechanism 40, so that an image is formed on the surface of the medium M using ink.

[0019] A2. Electrical configuration of the liquid ejection device 2 is a diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment. As shown in FIG.

[0020] The head chip 51 has a plurality of ejection units 510. Under the control of the control unit 20, the switching circuit 52 switches whether or not to supply at least a part of the common drive signal Com output from the control unit 20 as the supply signal Vin to each of the plurality of ejection units 510 included in the head chip 51.

[0021] In the example shown in FIG. 2, the head chip 51 has M discharge units 510. M is a natural number equal to or greater than 1. Hereinafter, the m-th discharge unit 510 among the M discharge units 510 may be referred to as discharge unit 510m. m is a natural number satisfying "1≦m≦M." Hereinafter, when a component or signal of the head 50 corresponds to discharge unit 510m among the M discharge units 510, the subscript m may be added to the symbol representing the component or signal.

[0022] The control unit 20 includes a control circuit 21, a memory circuit 22, a power supply circuit 23, and a drive signal generation unit 24.

[0023] The control circuit 21 has a function to control the operation of each part of the liquid ejection device 100 and a function to process various data. The control circuit 21 includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the control circuit 21 may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU. Furthermore, when the control circuit 21 is made up of multiple processors, the multiple processors may be mounted on different boards or the like.

[0024] The memory circuit 22 stores various programs executed by the control circuit 21 and various data such as print data Img processed by the control circuit 21. The memory circuit 22 includes, for example, one or both of semiconductor memories: a volatile memory such as RAM (Random Access Memory) and a non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM). The print data Img is supplied from an external device 200 such as a personal computer or digital camera. The memory circuit 22 may be configured as part of the control circuit 21.

[0025] The power supply circuit 23 receives power from a commercial power supply (not shown) and generates various predetermined potentials. The generated potentials are supplied to each section of the liquid ejection device 100 as appropriate. For example, the power supply circuit 23 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head 50. The power supply potential VHV is also supplied to the drive signal generation section 24.

[0026] The drive signal generation unit 24 is a circuit that generates the common drive signal Com. Specifically, the drive signal generation unit 24 has, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation unit 24, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 21 from a digital signal to an analog signal, and the amplifier circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 23, thereby generating the common drive signal Com. Of the waveforms included in the common drive signal Com, the signal with the waveform that is actually supplied to the ejection unit 510 is the aforementioned supply signal Vin. The waveform designation signal dCom is a digital signal that defines the waveform of the common drive signal Com.

[0027] The control circuit 21 executes a program stored in the memory circuit 22 to control the operation of each part of the liquid ejection device 100. Here, by executing the program, the control circuit 21 generates control signals Sk1 and Sk2, a print data signal SI, a waveform designation signal dCom, a latch signal LAT, a change signal CNG, and a clock signal CLK as signals for controlling the operation of each part of the liquid ejection device 100.

[0028] The control signal Sk1 is a signal for controlling the driving of the transport mechanism 30. The control signal Sk2 is a signal for controlling the driving of the movement mechanism 40. The print data signal SI is a digital signal for specifying the operating state of the ejection unit 510. The latch signal LAT and the change signal CNG are used in conjunction with the print data signal SI and are timing signals that determine the timing of ink ejection from each nozzle of the head chip 51. These timing signals are generated, for example, based on the output of an encoder that detects the position of the carriage 41 described above.

[0029] A3.Specific structure of the head chip FIG. 3 is a cross-sectional view showing an example of a head chip 51. As shown in FIG. 3, the head chip 51 has a plurality of nozzles N arranged in a direction along the Y axis. Each nozzle N ejects ink to land on a medium M. The plurality of nozzles N are divided into a first row L1 and a second row L2 arranged at intervals in a direction along the X axis. Each of the first row L1 and the second row L2 is a collection of a plurality of nozzles N arranged linearly in a direction along the Y axis.

[0030] The head chips 51 are configured to be approximately symmetrical with respect to each other in the direction along the X-axis. The positions of the multiple nozzles N in the first row L1 and the multiple nozzles N in the second row L2 in the direction along the Y-axis may be the same or different. Figure 3 illustrates a configuration in which the positions of the multiple nozzles N in the first row L1 and the multiple nozzles N in the second row L2 in the direction along the Y-axis are the same.

[0031] As shown in FIG. 3, the head chip 51 has a flow path substrate 51a, a pressure chamber substrate 51b, a nozzle plate 51c, a vibration absorber 51d, a vibration plate 51e, a plurality of drive elements 51f, a protective plate 51g, a case 51h, and a wiring substrate 51i.

[0032] The flow path substrate 51a and the pressure chamber substrate 51b are stacked in this order in the Z1 direction to form a flow path for supplying ink to the multiple nozzles N. A diaphragm 51e, multiple drive elements 51f, a protective plate 51g, a case 51h, and a wiring substrate 51i are provided in an area positioned in the Z1 direction from the stack of the flow path substrate 51a and the pressure chamber substrate 51b. On the other hand, a nozzle plate 51c and a vibration absorber 51d are provided in an area positioned in the Z2 direction from the stack. Each element of the head chip 51 is roughly a plate-like member that is elongated in the Y direction, and is joined to one another by, for example, an adhesive.

[0033] The nozzle plate 51c is a plate-like member provided with a plurality of nozzles N in a first row L1 and a second row L2. Each of the plurality of nozzles N is a through-hole that allows ink to pass through. The surface of the nozzle plate 51c facing the Z2 direction is the nozzle surface FN. The nozzle plate 51c is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing techniques such as dry etching or wet etching. However, other known methods and materials may also be used as appropriate to manufacture the nozzle plate 51c. Furthermore, the cross-sectional shape of the nozzle is typically circular, but is not limited thereto and may be a non-circular shape such as a polygonal or elliptical shape.

[0034] The flow path substrate 51a is provided with a space R1, a plurality of supply flow paths Ra, and a plurality of communication flow paths Na for each of the first row L1 and the second row L2. The space R1 is an elongated opening extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. Each of the supply flow paths Ra and the communication flow paths Na is a through hole formed for each nozzle N. Each supply flow path Ra communicates with the space R1.

[0035] The pressure chamber substrate 51b is a plate-like member in which a plurality of pressure chambers C, called cavities, are provided in each of a first row L1 and a second row L2. The pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in a direction along the X axis in a plan view. Like the nozzle plate 51c described above, the flow path substrate 51a and the pressure chamber substrate 51b are each manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example. Note that other known methods and materials may also be used as appropriate to manufacture the flow path substrate 51a and the pressure chamber substrate 51b.

[0036] The pressure chambers C are spaces located between the flow path substrate 51a and the vibration plate 51e. A plurality of pressure chambers C are arranged in the direction along the Y axis in each of the first row L1 and the second row L2. The pressure chambers C are also in communication with the communication flow path Na and the supply flow path Ra. Therefore, the pressure chambers C are in communication with the nozzle N via the communication flow path Na, and are in communication with the space R1 via the supply flow path Ra.

[0037] A diaphragm 51e is disposed on the surface of the pressure chamber substrate 51b facing the Z1 direction. The diaphragm 51e is a plate-like member that can vibrate elastically. The diaphragm 51e has, for example, a first layer and a second layer, which are stacked in this order in the Z1 direction. The first layer is, for example, an elastic film made of silicon oxide (SiO2). The elastic film is formed, for example, by thermally oxidizing one surface of a silicon single crystal substrate. The second layer is, for example, an insulating film made of zirconium oxide (ZrO2). The insulating film is formed, for example, by forming a zirconium layer by sputtering and then thermally oxidizing the layer. Note that the diaphragm 51e is not limited to the configuration of the stacked first and second layers described above, and may be, for example, a single layer or three or more layers.

[0038] A plurality of drive elements 51f corresponding to the nozzles N are arranged on the surface of the vibration plate 51e facing the Z1 direction. Each drive element 51f generates a pressure fluctuation in the ink in the pressure chamber C when supplied with a supply signal Vin generated from a common drive signal Com. Each drive element 51f has an elongated shape extending in the direction along the X axis in a plan view. The plurality of drive elements 51f are arranged in the direction along the Y axis so as to correspond to the plurality of pressure chambers C. The drive elements 51f overlap the pressure chambers C in a plan view.

[0039] Each drive element 51f is a piezoelectric element and includes a first electrode, a piezoelectric layer, and a second electrode (not shown), which are stacked in this order in the Z1 direction. One of the first and second electrodes is an individual electrode spaced apart from one another for each drive element 51f. A supply signal Vin is applied to the one electrode. The other of the first and second electrodes is a strip-shaped common electrode extending continuously along the Y-axis across the multiple drive elements 51f. An offset potential VBS is supplied to the other electrode. Examples of metal materials for these electrodes include platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), and copper (Cu). These materials can be used singly or in combination, such as in the form of an alloy or a laminate. The piezoelectric layer is made of a piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O3) and has, for example, a strip shape extending continuously along the Y-axis across the plurality of drive elements 51f. However, the piezoelectric layer may be integral across the plurality of drive elements 51f. In this case, through-holes that penetrate the piezoelectric layer and extend along the X-axis are provided in areas that correspond in plan view to the gaps between adjacent pressure chambers C. When the diaphragm 51e vibrates in conjunction with the deformation of the drive elements 51f, the pressure in the pressure chambers C fluctuates, causing ink to be ejected from the nozzles N.

[0040] The protective plate 51g is a plate-like member installed on the surface of the diaphragm 51e facing the Z1 direction, and protects the multiple drive elements 51f and reinforces the mechanical strength of the diaphragm 51e. The multiple drive elements 51f are housed between the protective plate 51g and the diaphragm 51e. The protective plate 51g is made of, for example, a resin material.

[0041] The case 51h is a member for storing ink to be supplied to the multiple pressure chambers C. The case 51h is made of, for example, a resin material. A space R2 is provided in the case 51h for each of the first row L1 and the second row L2. The space R2 is a space that communicates with the aforementioned space R1, and together with the space R1, functions as a reservoir R that stores ink to be supplied to the multiple pressure chambers C. The case 51h is provided with an inlet IH for supplying ink to each reservoir R. The ink in each reservoir R is supplied to the pressure chamber C via each supply flow path Ra.

[0042] The vibration absorber 51d is also called a compliance substrate. The vibration absorber 51d is a flexible resin film that forms the wall surface of the reservoir R and absorbs pressure fluctuations of the ink inside the reservoir R. The vibration absorber 51d may also be a flexible thin metal plate. The surface of the vibration absorber 51d facing the Z1 direction is bonded to the flow path substrate 51a with an adhesive or the like.

[0043] The wiring board 51i is mounted on the surface of the diaphragm 51e facing the Z1 direction, and is a mounting component for electrically connecting the control unit 20 and the head chip 51. The wiring board 51i is a flexible wiring board such as a COF (Chip On Film), an FPC (Flexible Printed Circuit), or an FFC (Flexible Flat Cable). A switching circuit 52 for supplying a drive voltage to each drive element 51f is mounted on the wiring board 51i of this embodiment.

[0044] In the head chip 51 configured as described above, the ejection section 510 includes at least the nozzle N, the pressure chamber C, and the drive element 51f. In this embodiment, the ejection section 510 includes the nozzle N, the pressure chamber C, the supply flow path Ra, the communication flow path Na, the drive element 51f, and the part of the diaphragm 51e that is involved in the operation of ejecting ink from the nozzle N by driving the drive element 51f.

[0045] A4. Driving element 51f 4 is a diagram for explaining the switching circuit 52. The driving element 51f is driven by the supply signal Vin from the switching circuit 52.

[0046] As shown in FIG. 4, wirings LHa and LHb are connected to the switching circuit 52. In this embodiment, the common drive signal Com is exemplified by a first common drive signal ComA and a second common drive signal ComB. The wiring LHa is a signal line that transmits the first common drive signal ComA. The wiring LHb is a signal line that transmits the second common drive signal ComB. In FIG. 4, one of the first electrode and second electrode of the drive element 51f is shown as electrode Zd[m], and the other is shown as electrode Zu[m]. The wiring LHd is connected to the electrode Zd[m]. The wiring LHd is a power supply line to which an offset potential VBS is supplied.

[0047] The switching circuit 52 has M switches SWa (SWa[1] to SWa[M]), M switches SWb (SWb[1] to SWb[M]), and a connection state designation circuit 52a that designates the connection states of these switches.

[0048] The switch SWa[m] is a switch that switches between conduction (ON) and non-conduction (OFF) between the wiring LHa for transmitting the first common drive signal ComA and the electrode Zu[m] of the drive element 51f[m]. The switch SWb[m] is a switch that switches between conduction (ON) and non-conduction (OFF) between the wiring LHb for transmitting the second common drive signal ComB and the electrode Zu[m] of the drive element 51f[m]. Each of these switches is, for example, a transmission gate.

[0049] The connection state designation circuit 52a generates connection state designation signals SLa[1] to SLa[M] that designate the on / off states of the switches SWa[1] to SWa[M], and connection state designation signals SLb[1] to SLb[M] that designate the on / off states of the switches SWb[1] to SWb[M], based on the clock signal CLK, print data signal SI, latch signal LAT, and change signal CNG supplied from the control circuit 21.

[0050] For example, although not shown, the connection state designation circuit 52a includes multiple transfer circuits, multiple latch circuits, and multiple decoders in one-to-one correspondence with the drive elements 51f[1] to 51f[M]. Of these, the transfer circuit receives a print data signal SI. The print data signal SI includes an individual designation signal for each drive element 51f. The individual designation signals are serially supplied and transferred sequentially to the multiple transfer circuits in synchronization with a clock signal CLK. The latch circuit latches the individual designation signal supplied to the transfer circuit based on a latch signal LAT. The decoder generates connection state designation signals SLa[m] and SLb[m] based on the individual designation signal, the latch signal LAT, and the change signal CNG.

[0051] The switch SWa[m] is switched on and off according to the connection state designation signal SLa[m] generated as described above. For example, the switch SWa[m] is in an on state when the connection state designation signal SLa[m] is at a high level, and in an off state when the connection state designation signal SLa[m] is at a low level. As described above, the switching circuit 52 supplies part or all of the waveform included in the first common drive signal ComA as the supply signal Vin to one or more drive elements 51f selected from the plurality of drive elements 51f.

[0052] Similarly, the switch SWb[m] is switched on and off in response to the connection state designation signal SLb[m]. For example, the switch SWb[m] is turned on when the connection state designation signal SLb[m] is at a high level, and turned off when the connection state designation signal SLb[m] is at a low level. As described above, the switching circuit 52 supplies part or all of the waveform included in the second common drive signal ComB as the supply signal Vin to one or more drive elements 51f selected from the plurality of drive elements 51f.

[0053] A5. Drive signal 5 is a diagram illustrating the common drive signal Com used in the first embodiment. As shown in FIG. 5, the latch signal LAT includes a pulse PL for defining a drive period Tu. The drive period Tu corresponds to a printing period for forming dots of ink from the nozzles N on the medium M. The drive period Tu is defined as, for example, the period from the rising edge of a pulse PL to the rising edge of the next pulse PL. The specific length or period of the drive period Tu is not particularly limited.

[0054] The change signal CNG1 also includes a pulse PLA for dividing the drive period Tu into a preceding control period Tua1 and a following control period Tua2. The control period Tua1 is, for example, the period from the rising edge of the pulse PL to the rising edge of the pulse PLA. The control period Tua2 is, for example, the period from the rising edge of the pulse PLA to the rising edge of the pulse PL. The change signal CNG2 also includes a pulse PLB for dividing the drive period Tu into a preceding control period Tub1 and a following control period Tub2. The control period Tub1 is, for example, the period from the rising edge of the pulse PL to the rising edge of the pulse PLB. The control period Tub2 is, for example, the period from the rising edge of the pulse PLB to the rising edge of the pulse PL.

[0055] The first common drive signal ComA includes a first ejection pulse P1 and a final ejection pulse P2 in this order within a drive period Tu. The first ejection pulse P1 is provided in a control period Tua1. The final ejection pulse P2 is provided in a control period Tua2.

[0056] The second common drive signal ComB includes a vibration imparting pulse P3 and an ejection pulse P4, in this order. The vibration imparting pulse P3 is provided in the control period Tub1. The ejection pulse P4 is provided in the control period Tub2.

[0057] In the following description, the first ejection pulse P1, the final ejection pulse P2, and the ejection pulse P4 may each be referred to as an ejection pulse P. The ejection pulse P is a potential pulse that drives the drive element 51f to generate a pressure fluctuation in the pressure chamber C strong enough to eject ink from the nozzle N.

[0058] The first ejection pulse P1, the final ejection pulse P2, the vibration imparting pulse P3, and the ejection pulse P4 are appropriately selected and used as the supply signal Vin. By selecting the pulses, it is possible to adjust the amount of ink ejected from the nozzle N or to slightly vibrate the ink in the nozzle N without ejecting ink from the nozzle N.

[0059] For example, by appropriately combining pulses in the drive period Tu, it is possible to eject dots of different sizes from the nozzle N, namely a first dot which is a large dot, a second dot which is a medium dot, and a third dot which is a small dot.

[0060] Multiple types of dot drive signals are generated by appropriately selecting pulses included in the common drive signal Com. Specifically, a first dot drive signal Vin1 for forming a first dot that is a large dot, a second dot drive signal Vin2 for forming a second dot that is a medium dot, and a third dot drive signal Vin3 for forming a third dot that is a small dot are generated.

[0061] A6. First dot drive signal Vin1 Fig. 6 is a diagram showing the first dot drive signal Vin1 in the first embodiment. Fig. 6 shows the waveform of the first dot drive signal Vin1 when forming large dots on the medium M. The first dot drive signal Vin1 is supplied to the drive element 51f as the supply signal Vin.

[0062] The first dot drive signal Vin1 is the same as the first common drive signal ComA and includes multiple ejection pulses P, including a first ejection pulse P1 and a final ejection pulse P2. The first dot drive signal Vin1 is generated by selecting the first ejection pulse P1 and the final ejection pulse P2 of the first common drive signal ComA. Each ejection pulse P ejects one droplet DR. The multiple droplets DR generated by the multiple ejection pulses P combine before landing on the medium M, and the combined droplet DRA formed by the combination of the multiple droplets DR lands on the medium M.

[0063] Among the multiple ejection pulses P, the first ejection pulse P in chronological order is the first ejection pulse P1. The last ejection pulse P2 is also the second ejection pulse in chronological order among the multiple ejection pulses P. In addition, a first connection element CN1 is provided between the first ejection pulse P1 and the last ejection pulse P2. In this embodiment, the first connection element CN1 maintains a reference potential E0. The reference potential E0 is a potential higher than zero potential, for example, a potential higher than an offset potential VBS. The first connection element CN1 is a connection element that connects the first ejection pulse P1 and the following second pulse.

[0064] The first ejection pulse P1 is a trapezoidal wave having a fill element a1, a sustain element a2, and an ejection element a3 in this order. The first ejection pulse P1 is a so-called pull-push waveform. The fill element a1 is an element that drives the drive element 51f to generate negative pressure in the pressure chamber C by changing its potential. The fill element a1 changes its potential from a reference potential E0 to a first potential E1 that is lower than the reference potential E0. The first potential E1 is the minimum potential of the voltage of the first ejection pulse P1. The sustain element a2 is an element that maintains the first potential E1. The ejection element a3 is an element that drives the drive element 51f to generate positive pressure in the pressure chamber C by changing its potential, thereby ejecting a droplet DR from the nozzle N. The ejection element a3 changes its potential from the first potential E1 to the reference potential E0 and connects to the first connection element CN1. The first connection element CN1 maintains the reference potential E0 until the start p4 of the last ejection pulse P2.

[0065] The final ejection pulse P2 includes a fill element b1, a sustain element b2, an ejection element b3, a sustain element b4, a damping element b5, a sustain element b6, and a return element b7, in this order. The final ejection pulse P2 includes a so-called pull-push-pull waveform consisting of the fill element b1, the sustain element b2, the ejection element b3, the sustain element b4, and the damping element b5. The fill element b1 drives the drive element 51f to generate a negative pressure in the pressure chamber C by changing the potential. The fill element b1 is connected to the first connection element CN1, and changes its potential from a reference potential E0 to a second potential E2 that is lower than the reference potential E0. The second potential E2 is the minimum voltage of the final ejection pulse P2. The sustain element b2 maintains the second potential E2. The ejection element b3 drives the drive element 51f to generate a positive pressure in the pressure chamber C by changing the potential, thereby ejecting a droplet DR from the nozzle N. The potential of the ejection element b3 changes from the second potential E2 to a third potential E3 higher than the reference potential E0. The third potential E3 is the maximum potential of the voltage of the last ejection pulse P2. The reference potential E0 is located between the third potential E3 and the first potential E1. The reference potential E0 is also located between the third potential E3 and the second potential E2.

[0066] The sustain element b4, the damping element b5, the sustain element b6, and the return element b7 constitute a damping pulse. The sustain element b4 maintains the third potential E3 after the ejection element b3. The damping element b5 is an element that attenuates the pressure fluctuations in the pressure chamber C by changing its potential after the ejection element b3. The damping element b5 is an element that drives the drive element 51f to generate negative pressure in the pressure chamber C. The period of the sustain element b4 is set so that the damping element b5 generates negative pressure and attenuates the residual vibration when the pressure vibration remaining in the ink in the ejection section 510 after the ejection element b3 is positive. The damping element b5 changes in potential from the third potential E3 to a potential E4 that is equal to or lower than the reference potential E0. The potential E4 is higher than the second potential E2 and lower than the reference potential E0. The sustain element b6 is an element that maintains the potential E4. The return element b7 is an element that drives the drive element 51f to generate a positive pressure in the pressure chamber C. The return element b7 changes potential from potential E4 to reference potential E0. In other words, the return element b7 is an element that returns from potential E4 other than the reference potential E0 to the reference potential E0.

[0067] By supplying the first dot drive signal Vin1 to the drive element 51f during one drive period Tu, it is possible to print the first dot, which is a large dot, on the medium M.

[0068] Fig. 7 is a diagram illustrating a combined droplet DRA obtained by combining a plurality of droplets DR sequentially ejected from a nozzle N. In Fig. 7, the plurality of droplets DR are shown as a droplet DR1 based on a first ejection pulse P1 and a droplet DR2 based on a final ejection pulse P2.

[0069] 7 is supplied to the drive element 51f, the droplet DR1 and the droplet DR2 are ejected from the nozzle N in this order, as shown in FIG. 7. The ejection conditions, such as the flight speed and ejection timing of the droplets DR1 and DR2, are set so that the subsequent droplet DR2 catches up with the droplet DR1 before it lands on the medium M. The droplets DR1 and DR2 combine to form a combined droplet DRA before landing on the medium M. The combined droplet DRA then lands on the medium M.

[0070] As described above, the ejection element a3 of the first ejection pulse P1 changes in potential from the first potential E1 to the reference potential E0 and connects to the first connection element CN1. Therefore, the first ejection pulse P1 includes a trapezoidal pulse and a so-called pull-push waveform, not a so-called pull-push-pull waveform. In contrast, the filling element b1 of the last ejection pulse P2 changes in potential from a potential equal to or greater than the reference potential E0 to a second potential E2. The ejection element b3 of the last ejection pulse P2 changes in potential from the second potential E2 to a third potential E3 greater than the reference potential E0. The damping element b5 of the last ejection pulse P2 changes in potential from the third potential E3 to a potential equal to or less than the reference potential E0. Therefore, the last ejection pulse P2 includes a so-called pull-push-pull waveform, and has a larger potential change width than the first ejection pulse P1.

[0071] By providing the first ejection pulse P1, which is a trapezoidal pulse, the drive period Tu can be shortened without excessively increasing the ink flight speed, compared to the conventional ejection pulse Px with a so-called pull-push-pull waveform shown in Figure 28. Therefore, even if the interval between the first ejection pulse P1 and the last ejection pulse P2 is narrowed by high-speed driving, the droplets DR1 and DR2 are easily combined, and the instability of ink ejection can be reduced compared to the conventional method. Furthermore, the first ejection pulse P1, which is a trapezoidal pulse, has a smaller ejection volume and faster ink refill than the ejection pulse Px with a so-called pull-push-pull waveform, which is advantageous in terms of ensuring the ejection volume of the last ejection pulse P2.

[0072] Furthermore, by providing the final ejection pulse P2, the potential change width can be made larger than that of the first ejection pulse P1, thereby increasing the droplet volume. Therefore, by using the first dot drive signal Vin1 that includes the first ejection pulse P1 and the final ejection pulse P2, it is possible to reduce the instability of ink ejection during high-speed driving while ensuring the ink droplet volume.

[0073] In this way, the first dot drive signal Vin1 is a combination of the first ejection pulse P1, which is a trapezoidal wave, and the last ejection pulse P2, which is a so-called pull-push-pull waveform that is not a trapezoidal wave. Therefore, it is possible to adjust the droplet flight speed while generating different droplet sizes without increasing the waveform length, and to land the combined droplet DRA at the desired position.

[0074] In this embodiment, the period T1 from the start p4 of the fill element b1 of the last ejection pulse P2 to the start p5 of the ejection element b3 of the last ejection pulse P2 shown in FIG. 6 is equal to or greater than 0.3 TC and less than 0.5 TC. TC indicates the natural vibration period of the ejection unit 510. By setting the period T1 within this range, it is possible to reduce the variation in the ink landing positions of the multiple ejection units 510 compared to when it is outside this range. Furthermore, the residual vibration can increase the amount of ink ejected.

[0075] Furthermore, the final ejection pulse P2 of the first dot drive signal Vin1 includes a damping element b5, which makes it possible to improve the stability of the meniscus of the nozzle N after the application of the final ejection pulse P2 compared to when the damping element b5 is not included.

[0076] Fig. 8 is a diagram showing the residual vibration signal Vout corresponding to the pressure fluctuation of the ink remaining after a pressure fluctuation is applied to the ink in the pressure chamber C. For example, if the drive element 51f is driven to generate a pressure fluctuation in the ink in the pressure chamber C and then the electromotive force generated in the drive element 51f is measured, a residual vibration signal Vout such as that shown in Fig. 8 is detected. The residual vibration has a natural vibration period TC that is determined by the shape of the nozzle N, the shape of the individual flow path, the weight of the ink in the flow path of the head chip 3, the viscosity of the ink, etc.

[0077] The residual vibration signal Vout shown in FIG. 8 may differ from one another among the multiple ejectors 510 due to manufacturing errors, etc. For example, the residual vibration signal Vout of one ejector 510 is shown by a solid line, and the residual vibration signal Vout of another ejector 510 is shown by a dashed line. The difference in signals between such ejectors 510 increases as time passes. The difference is smallest in the period Ta before the first peak P0 of the residual vibration signal Vout. The period Ta includes a period of 0.3 TC or more and less than 0.5 TC. Note that the period Tb immediately after the first peak P0 is less susceptible to the influence of residual vibrations and less likely to produce satellites than the period Ta. The period Tb includes a period of 0.5 TC or more and less than 0.7 TC.

[0078] As described above, the final ejection pulse P2 ejects a larger amount of ink than the first ejection pulse P1. Therefore, the final ejection pulse P2 has a greater effect on the landing speed and landing position of the combined droplet DRA than the first ejection pulse P1. Therefore, the influence of the droplet DR2 on the combined droplet DRA is significant. Therefore, by setting the period T1 of the final ejection pulse P2 related to the droplet DR2, which has a significant effect on the landing speed and landing position of the combined droplet DRA, to be greater than or equal to 0.3 TC and less than 0.5 TC, it is possible to reduce the variation in the landing positions of the ink from the multiple ejection sections 510.

[0079] Furthermore, the first pulse interval T0 is not particularly limited, but is preferably 1.7TC or more and less than 2.7TC. The first pulse interval T0 is the period from the start p1 of the fill element a1 of the first ejection pulse P1 to the start p4 of the fill element b1 of the last ejection pulse P2, which is the second ejection pulse. By setting the first pulse interval T0 within the above range, the ejection volume of the droplet DR2 can be increased compared to when the first pulse interval T0 is outside the range due to the synergistic effect of the residual vibration generated in the ink in the ejection section 510 by the first ejection pulse P1 and the pressure fluctuation applied to the ink in the ejection section 510 by the last ejection pulse P2. In addition, it is easier for the droplets DR1 and DR2 to merge before the droplet DR2 hits the medium M.

[0080] If the first pulse interval T0 is less than 1.7 TC, satellites are likely to occur during the ejection of the final ejection pulse P2. This is because the amplitude of the residual vibration caused by the first ejection pulse P1 is still too large, making the ink pressure fluctuation caused by the final ejection pulse P2 following the first ejection pulse P1 unstable. On the other hand, if the first pulse interval T0 is 2.7 TC or greater, the interval between the first ejection pulse P1 and the final ejection pulse P2 is too long, preventing the droplet DR2 from catching up with the droplet DR1 and forming a combined droplet DRA. Furthermore, the residual vibration of the first ejection pulse P1 is attenuated, preventing a synergistic effect with the pressure fluctuation imparted to the ink in the ejection section 510 by the final ejection pulse P2, potentially resulting in an inability to eject the desired amount of ink.

[0081] The pulse width T2 of the first ejection pulse P1 is not particularly limited, but is preferably 0.3TC or more and less than 0.5TC. The pulse width T2 is the period from the start p1 of the fill element a1 of the first ejection pulse P1 to the start p2 of the ejection element a3. By keeping the pulse width T2 within the above range, it is possible to reduce the overall waveform length while minimizing variations in the flight speed and weight of ink droplets ejected from the multiple ejection sections 510, compared to when the pulse width T2 is outside the range. Therefore, this is particularly suitable for high-speed driving.

[0082] Furthermore, the potential change rate r1 of the filling element a1 of the first ejection pulse P1 is equal to or less than the potential change rate r3 of the filling element b1 of the last ejection pulse P2, and in this embodiment, is equal to the potential change rate r3. Therefore, even if the influence of the residual vibration of the last ejection pulse P2 remains at the start p1 of the first ejection pulse P1 in the next two cycles after the last ejection pulse P2 in one cycle, the instability of ejection by the first ejection pulse P1 can be reduced.

[0083] A7. Second dot drive signal Vin2 9 is a diagram showing the second dot drive signal Vin2 in the first embodiment, showing the waveform of the second dot drive signal Vin2 when forming second dots that are medium dots on the medium M.

[0084] The second dot drive signal Vin2 includes a vibration imparting pulse P3 and a final ejection pulse P2. Specifically, the second dot drive signal Vin2 is generated by selecting the vibration imparting pulse P3 of the second common drive signal ComB and the final ejection pulse P2 of the first common drive signal ComA during one drive period Tu. A second connection element CN2 is provided between the vibration imparting pulse P3 and the final ejection pulse P2. The second connection element CN2 maintains a reference potential E0.

[0085] The vibration imparting pulse P3 pressurizes and depressurizes the ink in the pressure chamber C, thereby imparting a pressure fluctuation to the liquid in the pressure chamber C without ejecting ink from the nozzle N. As described above, the final ejection pulse P2 imparts a pressure fluctuation to the liquid in the pressure chamber C so as to eject ink from the nozzle N. Therefore, application of the second common drive signal ComB causes one droplet DR to be ejected from the nozzle N, and the droplet DR lands on the medium M. In other words, the second dot drive signal Vin2 does not form a combined droplet DRA.

[0086] The vibration imparting pulse P3 has an expansion element c1, a sustain element c2, and a contraction element c3, in this order. The expansion element c1 is an element that drives the driving element 51f to generate negative pressure in the pressure chamber C by changing its potential. The expansion element c1 changes its potential from a reference potential E0 to a lower potential E5. The potential E5 is the minimum potential of the voltage of the vibration imparting pulse P3. The sustain element c2 is an element that maintains the potential E5. The contraction element c3 is an element that drives the driving element 51f to generate positive pressure in the pressure chamber C to the extent that a droplet DR is not ejected from the nozzle N by changing its potential. The contraction element c3 changes its potential from the potential E5 to the reference potential E0 and connects to the second connecting element CN2. The second connecting element CN2 connects the end point p9 of the vibration imparting pulse P3 to the start point p4, which is the beginning point of the final ejection pulse P2. The second connecting element CN2 maintains the reference potential E0. The start p4 of the final ejection pulse P2 is also the starting edge of the final ejection pulse P2.

[0087] By supplying the second dot drive signal Vin2 to the drive element 51f during one drive cycle Tu, it is possible to print the second dot, which is a medium dot that is smaller than the first dot, which is a large dot, on the medium M. The residual vibration caused by the vibration imparting pulse P3 can be used to increase the amount of ink ejected by the final ejection pulse P2.

[0088] Furthermore, as described above, by supplying the first dot drive signal Vin1 generated by selecting the first ejection pulse P1 and the last ejection pulse P2 of the first common drive signal ComA to the drive element 51f during one drive period Tu, a large first dot can be printed on the medium M. Then, by supplying the second dot drive signal Vin2 generated by selecting the vibration imparting pulse P3 of a second common drive signal ComB that is different from the first common drive signal ComA and the last ejection pulse P2 of the first common drive signal ComA to the drive element 51f, a medium second dot can be printed on the medium M. For this reason, rather than arranging all of the pulses required to form different dots in chronological order in one common drive signal Com, the pulses required to form different dots are distributed among multiple common drive signals Com and some pulses are commonly used to form the different dots, thereby shortening the length of one drive period and enabling gradation expression with high-frequency drive. Furthermore, the second dot drive signal Vin2 and the first dot drive signal Vin1 each include the final ejection pulse P2 of the first common drive signal ComA. Therefore, by using the final ejection pulse P2 when forming dots of different sizes, it is possible to easily align the landing positions of dots of different sizes.

[0089] For example, for two adjacent nozzles N, a first dot drive signal Vin1 is applied as a supply signal Vin[m] to the drive element 51f[m] corresponding to one nozzle N[m], and a second dot drive signal Vin2 is applied as a supply signal Vin[m+1] to the drive element 51f[m+1] corresponding to the other nozzle N[m+1]. In this case, it is possible to reduce the deviation in the landing position in the dot alignment direction between the first dot ejected from the one nozzle N[m] and the second dot ejected from the other nozzle N[m+1].

[0090] The size ratio of the second dot to the first dot can be easily adjusted by adjusting the length of the second connecting element CN2. The duration of the second connecting element CN2 is not particularly limited, but is preferably 0.3 TC or more and less than 0.5 TC. In the example shown in FIG. 9, the period between the end of the vibration imparting pulse P3, p9, and the start of the fill element b1, p4, of the final ejection pulse P2, can be set to 0.3 TC or more and less than 0.5 TC. The duration of the second connecting element CN2 within the above range makes it easier to increase the size of the second dot and reduces the deviation of the landing position compared to when the duration is outside the range.

[0091] When forming the second dot, if the flight speed of the last ejection pulse P2 is slowed down to match the landing position of the first dot and to reduce the size of the first dot, the period of the second connection element CN2 can be set to 0.5TC or more and less than 0.7TC.

[0092] Furthermore, the vibration imparting pulse P3 is not limited to being used for forming the second dot. For example, the vibration imparting pulse P3 can also be used to drive the ink meniscus of the nozzle N to slightly vibrate in order to suppress thickening of the ink in the nozzle N during the non-ejecting drive cycle Tu. Therefore, the vibration imparting pulse P3 is used both for forming the second dot and for driving the ink to slightly vibrate in order to suppress thickening.

[0093] Furthermore, the pulse width T3 of the vibration imparting pulse P3 is not particularly limited, but is preferably equal to or greater than 0.3 TC and less than 0.5 TC. The pulse width T3 is the period from the start p7 of the expansion component c1 of the vibration imparting pulse P3 to the start p8 of the contraction component c3. By keeping the pulse width T3 within the above range, it is possible to efficiently generate pressure fluctuations in the ink in the pressure chamber C with a relatively small potential change amplitude, compared to when the pulse width T3 is outside this range.

[0094] A8. Third dot drive signal Vin3 10 is a diagram showing the third dot drive signal Vin3 in the first embodiment, showing the waveform of the third dot drive signal Vin3 when forming third dots that are small dots on the medium M.

[0095] The third dot drive signal Vin3 includes an ejection pulse P4. The third dot drive signal Vin3 is generated by selecting the ejection pulse P4 of the second common drive signal ComB during one drive period Tu. The ejection pulse P4 applies pressure fluctuations to the liquid in the pressure chamber C so as to eject ink from the nozzle N by pressurizing and depressurizing the ink in the pressure chamber C.

[0096] The potential of the ejection pulse P4 changes from the reference potential E0 to a lower potential E6, maintains the potential E6, then changes to an even lower potential E7, and maintains the potential E7. The ejection pulse P4 then changes from the potential E7 to a potential E8 higher than the reference potential E0, maintains the potential E8, then changes to a potential E9 lower than the reference potential E0, and maintains the potential E9. The ejection pulse P4 then changes from the potential E9 to a potential E10 higher than the potential E8, maintains the potential E10, and then returns to the reference potential E0. A third dot is ejected during the potential changes of the ejection pulse P4 from the potential E7 to the potential E8 and then from the potential E8 to the potential E9.

[0097] By supplying the third dot drive signal Vin3 to the drive element 51f during one drive period Tu, it is possible to print the third dot, which is a small dot, on the medium M.

[0098] A9. First variant 11 is a diagram showing the first dot drive signal Vin1 in the first modified example. In the first dot drive signal Vin1 in the first modified example, the preferred range of the pulse width T2 of the first ejection pulse P1 is different from the range in the first embodiment.

[0099] Specifically, the pulse width T2 of the first ejection pulse P1 is preferably equal to or greater than 0.5 TC and less than 0.7 TC. The pulse width T2 is the period from the start p1 of the filling element a1 of the first ejection pulse P1 to the start p2 of the ejection element a3. Negative pressure fluctuations begin in the ink within the ejection section 510 with the start of the filling element a1, and then change to positive pressure fluctuations after 0.5 TC. By setting the pulse width T2 of the first ejection pulse P1 to be equal to or greater than 0.5 TC and less than 0.7 TC, positive pressure can be applied by the ejection element a3 in synergy with the natural vibration occurring in the ink within the ejection section 510. Therefore, by setting the pulse width T2 of the first ejection pulse P1 within the above range, the pressure applied by the ejection element a3 can be suppressed compared to when the pulse width T2 is outside the range. This makes it easier to ensure the weight of the droplet DR1 produced by the first ejection pulse P1 while suppressing the speed of the first ejection pulse P1. The period Tb of the residual vibration signal Vout shown in FIG. 8 includes a period of 0.5 TC to 0.7 TC.

[0100] By setting the pulse width T2 of the first ejection pulse P1 to 0.5TC or more, the droplet DR1 generated by the first ejection pulse P1 is absorbed by the droplet DR2 generated by the subsequent final ejection pulse P2, even if the velocity of the droplet DR1 generated by the first ejection pulse P1 varies due to variations in the natural vibration period TC of each ejection section 510. Therefore, the first ejection pulse P1 has a low contribution rate to deviation in landing position.

[0101] A10. Second variant 12 is a diagram showing the first dot drive signal Vin1 in the second modified example. In the first dot drive signal Vin1 in the second modified example, the first connection element CN1 does not maintain the reference potential E0 from the end p3 of the first ejection pulse P1 to the start p4 of the last ejection pulse P2. In the second modified example, the first connection element CN1 maintains the reference potential E0 for a certain period from the end p3 of the first ejection pulse P1, and then changes to a potential E10 that exceeds the reference potential E0.

[0102] In the second modification, the potential of the filling element b1 of the final ejection pulse P2 changes from a potential E10 exceeding the reference potential E0 to a second potential E2. This second modification can also achieve the same effects as the first embodiment. Furthermore, the first connection element CN1 of the second modification can generate a larger negative pressure in the pressure chamber C during the filling element b1 of the final ejection pulse P2 than in the first embodiment. This can increase the weight of the droplet DR2.

[0103] B. Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiment, elements whose actions and functions are similar to those of the first embodiment will be designated by the same reference numerals as those used in the description of the first embodiment, and detailed descriptions of each element will be omitted as appropriate.

[0104] 13 is a diagram illustrating the common drive signal Com used in the second embodiment. As shown in FIG. 13, the common drive signal Com of the present embodiment includes a first common drive signal ComAa and a second common drive signal ComBa.

[0105] The first common drive signal ComAa includes a first ejection pulse P1, a vibration imparting pulse P3, and a final ejection pulse P2, in this order. The first ejection pulse P1 is provided in the control period Tua1. The vibration imparting pulse P3 is provided in the control period Tua2. The final ejection pulse P2 is provided in the control period Tua3. The second common drive signal ComBa includes a second ejection pulse P5 and an ejection pulse P13. The second ejection pulse P5 is provided in the control period Tub1. The ejection pulse P13 is provided in the control period Tub2.

[0106] The first dot drive signal Vin1, the second dot drive signal Vin2a, and the third dot drive signal Vin3a are generated by appropriately selecting pulses included in the first common drive signal ComAa and the second common drive signal ComBa. The first dot drive signal Vin1 is the same as the first dot drive signal Vin1 of the first embodiment, and is generated by selecting the first ejection pulse P1 and the last ejection pulse P2 from the first common drive signal ComAa. The third dot drive signal Vin3a is generated by selecting the ejection pulse P13 from the second common drive signal ComBa.

[0107] 14 is a diagram showing the second dot drive signal Vin2a in the second embodiment. As shown in Fig. 14, the second dot drive signal Vin2a is generated by selecting the second ejection pulse P5 from the second common drive signal ComBa during one drive period Tu. In this embodiment, unlike the first embodiment, the second dot drive signal Vin2a does not include the vibration imparting pulse P3.

[0108] The second ejection pulse P5 includes a fill element e1, a sustain element e2, an ejection element e3, a sustain element e4, and a damping element e5. The fill element e1 is an element that drives the drive element 51f to generate a negative pressure in the pressure chamber C by changing the potential. The fill element e1 changes its potential from a reference potential E0 to a lower potential E11. The potential E11 is the minimum potential of the voltage of the second ejection pulse P5. The sustain element e2 is an element that maintains the potential E11. The ejection element e3 is an element that drives the drive element 51f to generate a positive pressure in the pressure chamber C by changing the potential, thereby ejecting a droplet DR from the nozzle N. The ejection element e3 changes its potential from the potential E11 to a potential E12 that is higher than the reference potential E0. The potential E12 is the maximum potential of the voltage of the second ejection pulse P5. The sustain element e4 is an element that maintains the potential E12. The vibration damping element e5 is an element that drives the drive element 51f to generate positive pressure in the pressure chamber C. The potential of the vibration damping element e5 changes from potential E12 to reference potential E0. The period of the sustain element e4 is set so that, when the pressure vibration remaining in the ink in the ejection unit 510 after the ejection element e3 is positive, the vibration damping element b5 generates negative pressure to weaken the residual vibration. The vibration damping element e5 is also an element that returns to the reference potential E0 from a potential E12 other than the reference potential E0.

[0109] By supplying the second dot drive signal Vin2a to the drive element 51f during one drive period Tu, the second dot, which is a medium dot, can be printed on the medium M.

[0110] 13, the period ta1 of the filling element a1 of the first ejection pulse P1 in the first common drive signal ComAa overlaps with the period te1 of the filling element e1 of the second ejection pulse P5 in the second common drive signal ComBa. Also, the period ta3 of the ejection element a3 of the first ejection pulse P1 in the first common drive signal ComAa overlaps with the period te3 of the ejection element e3 of the second ejection pulse P5 in the second common drive signal ComBa.

[0111] By overlapping the period ta1 of the filling element a1 with the period te1 of the filling element e1, and by overlapping the period ta3 of the ejection element a3 with the period te3 of the ejection element e3, when a first dot is ejected from one of two adjacent ejection sections 510 and a second dot is ejected from the other, interference due to pressure fluctuations between them can be suppressed.

[0112] Note that the overlap between the period ta1 of the filling element a1 and the period te1 of the filling element e1 includes a complete overlap as well as a partial overlap. Similarly, the overlap between the period ta3 of the discharge element a3 and the period te3 of the discharge element e3 includes a complete overlap as well as a partial overlap. However, the greater the degree of overlap between the two, the more pronounced the effect described above becomes.

[0113] 15 is a diagram showing the third dot drive signal Vin3a in the second embodiment. As shown in Fig. 15, the third dot drive signal Vin3a is generated by selecting the ejection pulse P13 from the second common drive signal ComBa during one drive period Tu. In this embodiment, the third dot, which is a small dot, is formed by the droplet DR based on the ejection pulse P13.

[0114] The ejection pulse P13 applies pressure fluctuations to the liquid in the pressure chamber C so as to eject the ink from the nozzle N by pressurizing and depressurizing the ink in the pressure chamber C.

[0115] The ejection pulse P13 changes in potential from the reference potential E0 to a potential E30 lower than the reference potential E0, maintains the potential E30, then changes from the potential E30 to a potential E31 higher than the reference potential E0, and maintains the potential E31. The ejection pulse P13 then changes in potential from the potential E31 to a potential E32 lower than the reference potential E0, maintains the potential E32, and then changes in potential from the potential E32 to a potential E33 higher than the reference potential E0. After maintaining the potential E33, the potential changes from the potential E33 back to the reference potential E0. A third dot is ejected during the potential change of the ejection pulse P13 from the potential E30 to the potential E31 and then from the potential E31 to the potential E32.

[0116] By supplying the third dot drive signal Vin3a to the drive element 51f during one drive period Tu, the third dot, which is a small dot, can be printed on the medium M.

[0117] C. Third embodiment A third embodiment of the present disclosure will be described below. In the following exemplary embodiments, elements whose actions and functions are similar to those of the first embodiment will be designated by the same reference numerals as those used in the description of the first embodiment, and detailed descriptions thereof will be omitted where appropriate.

[0118] Fig. 16 is a diagram for explaining the common drive signal Com used in the third embodiment. As shown in Fig. 13, the common drive signal Com of this embodiment includes a first common drive signal ComAb and a second common drive signal ComBb.

[0119] The first common drive signal ComAb includes a first ejection pulse P1, a second ejection pulse P6, and a final ejection pulse P7, in this order. The first ejection pulse P1 is provided in the control period Tua1. The second ejection pulse P6 is provided in the control period Tua2. The final ejection pulse P7 is provided in the control period Tua3. The second common drive signal ComBb includes a vibration imparting pulse P3, a second ejection pulse P8, and an ejection pulse P9. The vibration imparting pulse P3 is provided in the control period Tub1. The second ejection pulse P8 is provided in the control period Tub2. The ejection pulse P9 is provided in the control period Tub3.

[0120] The first dot drive signal Vin1b, the second dot drive signal Vin2b, and the third dot drive signal Vin3b are formed by appropriately selecting pulses contained in the first common drive signal ComAb and the second common drive signal ComBb.

[0121] 17 is a diagram showing the first dot drive signal Vin1b in the third embodiment. As shown in Fig. 17, the first dot drive signal Vin1b has the same waveform as the first common drive signal ComAb and includes a first ejection pulse P1, a second ejection pulse P6, and a final ejection pulse P7. A combined droplet DRA is formed by three droplets DR: the droplet DR based on the first ejection pulse P1, the droplet DR based on the second ejection pulse P6, and the droplet DR based on the final ejection pulse P7.

[0122] The first ejection pulse P1 is a trapezoidal wave having a filling element a1, a sustaining element a2, and an ejection element a3 in this order. As in the first embodiment, the pulse width T2 of the first ejection pulse P1 is preferably equal to or greater than 0.3TC and less than 0.5TC, or equal to or greater than 0.5TC and less than 0.7TC.

[0123] The second ejection pulse P6 is the second ejection pulse in chronological order among the multiple ejection pulses P included in the first dot drive signal Vin1b. The second ejection pulse P6 has a filling element f1, a sustain element f2, an ejection element f3, a sustain element f4, and a damping element f5, in this order.

[0124] The fill element f1 is an element that drives the drive element 51f to generate negative pressure in the pressure chamber C by changing the potential. The fill element f1 changes its potential from a reference potential E0 to a lower potential E13. The potential E13 is the minimum voltage of the second ejection pulse P6. The sustain element f2 is an element that maintains the potential E13. The ejection element f3 is an element that drives the drive element 51f to generate positive pressure in the pressure chamber C and eject a droplet DR from the nozzle N by changing its potential. The ejection element f3 changes its potential from the potential E13 to a potential E14 that is higher than the reference potential E0. The potential E14 is the maximum potential of the voltage of the second ejection pulse P6. The sustain element f4 is an element that maintains the potential E14. The damping element f5 is an element that drives the drive element 51f to generate negative pressure in the pressure chamber C. The damping element f5 changes its potential from the potential E14 to the reference potential E0. The period of the sustain element f4 is set so that the vibration damping element f5 generates negative pressure to weaken the residual vibration when the pressure vibration remaining in the ink in the ejection section 510 after the ejection element f3 is positive. The vibration damping element f5 is an element that returns the potential to the reference potential E0 from a potential E14 other than the reference potential E0.

[0125] The final ejection pulse P7 has, in this order, a filling element g1, a sustaining element g2, an ejection element g3, a sustaining element g4, and a damping element g5.

[0126] The fill element g1 is an element that drives the drive element 51f to generate negative pressure in the pressure chamber C by changing the potential. The fill element g1 changes its potential from a reference potential E0 to a lower potential E15. The potential E15 is the minimum voltage of the final ejection pulse P7. The sustain element g2 is an element that maintains the potential E15. The ejection element g3 is an element that drives the drive element 51f to generate positive pressure in the pressure chamber C and eject a droplet DR from the nozzle N by changing its potential. The ejection element g3 changes its potential from the potential E15 to a potential E16 that is higher than the reference potential E0. The potential E16 is the maximum potential of the voltage of the final ejection pulse P7. The sustain element g4 is an element that maintains the potential E16. The damping element g5 is an element that drives the drive element 51f to generate negative pressure in the pressure chamber C. The damping element g5 changes its potential from the potential E16 to the reference potential E0. The period of the sustaining element g4 is set so that, at the timing when the pressure vibration remaining in the ink in the ejection section 510 after the ejection element g3 is positive, negative pressure is generated by the damping element g5 to weaken the residual vibration.

[0127] By supplying the first dot drive signal Vin1b to the drive element 51f during one drive cycle Tu, it is possible to print a large first dot on the medium M. As described above, the large dot is formed by a combined droplet DRA that is formed by combining three droplets DR based on the three ejection pulses P1, P6, and P7.

[0128] In this embodiment, as in the first embodiment, the period T1 from the start p7 of the fill element g1 of the last ejection pulse P7 to the start p8 of the ejection element g3 of the last ejection pulse P7 is equal to or greater than 0.3 TC and less than 0.5 TC. By setting the period T1 within this range, it is possible to reduce the variation in the ink landing positions of the multiple ejection sections 510 compared to when it is outside this range. In addition, the amount of ink ejected can be increased due to residual vibration.

[0129] Furthermore, in the first dot drive signal Vin1b, the first pulse interval T0, which is the interval between the start p1 of the fill element a1 of the first ejection pulse P1 and the start p13 of the fill element of the second ejection pulse P6 in the chronological order, is equal to or greater than 1.7 TC and less than 2.7 TC. Therefore, when the first pulse interval T0 is within the above range, the residual vibration of the first ejection pulse P1 can increase the ejection amount of the droplet DR based on the second ejection pulse P6 compared to when the first pulse interval T0 is outside the range. In addition, before the droplet DR based on the second ejection pulse P6 lands on the medium M, the droplet DR and the droplet DR based on the first ejection pulse P1 can be more easily combined. Furthermore, the potential change width of the ejection element g3 of the last ejection pulse P7 is larger than the potential change width of the ejection element f3 of the second ejection pulse P6, and the flight speed of the droplets DR based on the last ejection pulse P7 is faster than the flight speed of the droplets DR based on the second ejection pulse P6, making it easier for all the droplets DR to coalesce before landing on the medium M.

[0130] 18 is a diagram showing the second dot drive signal Vin2b in the third embodiment. As shown in FIG. 18, the second dot drive signal Vin2b includes a first ejection pulse P1 and a second ejection pulse P8, in this order. The second dot drive signal Vin2b is generated by selecting the first ejection pulse P1 of the first common drive signal ComAb and the second ejection pulse P8 of the second common drive signal ComBb. In this embodiment, a combined droplet DRA is formed by two droplets DR: one based on the first ejection pulse P1 and the other based on the second ejection pulse P8. Therefore, in this embodiment, the second dot, which is a medium dot, is formed by the combined droplet DRA.

[0131] The second ejection pulse P8 has, in this order, a filling element h1, a sustaining element h2, an ejection element h3, a sustaining element h4, and a damping element h5.

[0132] The fill element h1 is an element that drives the drive element 51f to generate a negative pressure in the pressure chamber C by changing the potential. The fill element h1 changes its potential from a reference potential E0 to a lower potential E17. The potential E17 is the minimum voltage of the second ejection pulse P8. The sustain element h2 is an element that maintains the potential E17. The ejection element h3 is an element that drives the drive element 51f to generate a positive pressure in the pressure chamber C by changing the potential, thereby ejecting a droplet DR from the nozzle N. The ejection element f3 changes its potential from the potential E17 to a potential E18 that is higher than the reference potential E0. The potential E18 is the maximum potential of the voltage of the second ejection pulse P8. The sustain element h4 is an element that maintains the potential E18. The damping element h5 is an element that drives the drive element 51f to generate a positive pressure in the pressure chamber C. The damping element h5 changes its potential from the potential E18 to the reference potential E0. The period of the sustain element h4 is set so that, at the timing when the pressure vibration remaining in the ink in the ejection section 510 after the ejection element h3 is positive, a negative pressure is generated by the vibration damping element h5 to weaken the residual vibration. The vibration damping element h5 is an element that returns the potential to the reference potential E0 from a potential E18 other than the reference potential E0.

[0133] By supplying the second dot drive signal Vin2b to the drive element 51f during one drive period Tu, the second dot, which is a medium dot, can be printed on the medium M.

[0134] In this embodiment, as in the first embodiment, the pulses required to form different dots are distributed among multiple common drive signals Com, and some pulses are commonly used to form different dots, thereby shortening the length of one drive cycle and enabling gradation expression with high-frequency drive. Furthermore, as described above, the first dot drive signal Vin1b and the second dot drive signal Vin2b each include the first ejection pulse P1 of the first common drive signal ComAb. Therefore, regardless of the size of dot to be formed, by using the first ejection pulse P1, which is a trapezoidal wave, it is easy to combine the droplet DR based on the first ejection pulse P1 and the droplet DR based on the next ejection pulse P. Furthermore, in the second dot drive signal Vin2b, the pulse to be combined with the first ejection pulse P1 of the first common drive signal ComAb is the second ejection pulse P8 of the second common drive signal ComBb, which is not selected in the first dot drive signal Vin1b.By adjusting the pulse shape of the second ejection pulse P8 regardless of the ejection amount of the first dot, it is easy to adjust the ejection amount of the second dot.

[0135] Furthermore, in the second dot drive signal Vin2b, the pulse interval T4, which is the interval between the start p1 of the fill element a1 of the first ejection pulse P1 and the start p14 of the fill element h1 of the second ejection pulse P8, is equal to or greater than 1.7 TC and less than 2.7 TC. When the pulse interval T4 is within the above range, the residual vibration of the first ejection pulse P1 ensures the ejection volume of the droplet DR2, and it is easier to combine the droplets DR1 and DR2 before the droplet DR2 hits the medium M, compared to when the pulse interval T4 is outside this range.

[0136] Furthermore, the first pulse interval T0 of the first dot drive signal Vin1b is equal to or greater than 1.7TC and less than 2.7TC. Also, by having the first pulse interval T0 and pulse interval T4 within the above range, when one of two adjacent ejection sections 510 ejects a first dot and the other ejects a second dot, interference due to pressure fluctuations between them can be suppressed compared to when they are outside the range.

[0137] 19 is a diagram showing the third dot drive signal Vin3b in the third embodiment. As shown in FIG. 19, the third dot drive signal Vin3b includes an ejection pulse P9. The third dot drive signal Vin3b is generated by selecting the ejection pulse P9 of the second common drive signal ComBb. In this embodiment, the third dot, which is a small dot, is formed by a droplet DR based on the ejection pulse P9.

[0138] The ejection pulse P9 applies pressure fluctuations to the liquid in the pressure chamber C so as to eject the ink from the nozzle N by pressurizing and depressurizing the ink in the pressure chamber C.

[0139] The ejection pulse P9 changes in potential from the reference potential E0 to a lower potential E19, maintains the potential E19, then changes in potential to a potential E20 higher than E19 but lower than the reference potential E0, and maintains the potential E20. The ejection pulse P9 then changes in potential from the potential E20 to a potential E21 higher than the reference potential E0, maintains the potential E21, and then returns to the reference potential E0. When the ejection pulse P9 changes in potential from the potential E19 to the potential E21, a third dot is ejected.

[0140] By supplying the third dot drive signal Vin3b to the drive element 51f during one drive period Tu, it is possible to print the third dot, which is a small dot, on the medium M.

[0141] D. Fourth embodiment A fourth embodiment of the present disclosure will be described below. In the following exemplary embodiments, elements whose actions and functions are similar to those of the first embodiment will be designated by the same reference numerals as those used in the description of the first embodiment, and detailed descriptions thereof will be omitted as appropriate.

[0142] 20 is a diagram illustrating the common drive signal Com used in the fourth embodiment. As shown in Fig. 20, the common drive signal Com of the present embodiment includes a first common drive signal ComAc and a second common drive signal ComBc.

[0143] The first common drive signal ComAc includes a first ejection pulse P1, a second ejection pulse P10, and a final ejection pulse P7, in this order. The first ejection pulse P1 is provided in the control period Tua1. The second ejection pulse P10 is provided in the control period Tua2. The final ejection pulse P7 is provided in the control period Tua3. The second common drive signal ComBc includes a vibration imparting pulse P3, a second ejection pulse P11, and an ejection pulse P9. The vibration imparting pulse P3 is provided in the control period Tub1. The second ejection pulse P11 is provided in the control period Tub2. The ejection pulse P9 is provided in the control period Tub3.

[0144] The first dot drive signal Vin1c, the second dot drive signal Vin2c, and the third dot drive signal Vin3b are generated by appropriately selecting pulses included in the first common drive signal ComAc and the second common drive signal ComBc. The third dot drive signal Vin3b is the same as that in the third embodiment, and its waveform is as shown in FIG.

[0145] 21 is a diagram showing the first dot drive signal Vin1c in the fourth embodiment. As shown in Fig. 21, the first dot drive signal Vin1c has the same waveform as the first common drive signal ComAc and includes a first ejection pulse P1, a second ejection pulse P10, and a final ejection pulse P7. A combined droplet DRA is formed by three droplets DR: the droplet DR based on the first ejection pulse P1, the droplet DR based on the second ejection pulse P10, and the droplet DR based on the final ejection pulse P7.

[0146] The first ejection pulse P1 is a trapezoidal wave having a filling element a1, a sustaining element a2, and an ejection element a3 in this order. As in the first embodiment, the pulse width T2 of the first ejection pulse P1 is preferably equal to or greater than 0.3TC and less than 0.5TC, or equal to or greater than 0.5TC and less than 0.7TC.

[0147] The second ejection pulse P10 is the second ejection pulse in chronological order among the multiple ejection pulses P included in the first dot drive signal Vin1c. The second ejection pulse P10 has a fill element i1, a sustain element i2, and an ejection element i3, in this order.

[0148] The fill element i1 is an element that drives the drive element 51f to generate negative pressure in the pressure chamber C by changing its potential. The fill element i1 changes its potential from a reference potential E0 to a lower potential E22. The potential E22 is the minimum voltage of the second ejection pulse P10. The sustain element i2 is an element that maintains the potential E22. The ejection element i3 is an element that drives the drive element 51f to generate positive pressure in the pressure chamber C by changing its potential, thereby ejecting ink from the nozzle N. The ejection element i3 changes its potential from the potential E22 to the reference potential E0. Furthermore, the ejection element i3 includes an element that changes its potential from the potential E22 to a potential E23, which is a potential between the reference potential E0 and the potential E22, and a damping element i30 that maintains the potential E23 and then changes its potential from the potential E23 to the reference potential E0. The period for maintaining potential E23 is set so that, at the timing when the pressure vibration remaining in the ink in the ejection section 510 is negative pressure after the potential change from potential E22 to potential E23, a positive pressure is generated by the potential change from potential E23 to reference potential E0, thereby weakening the residual vibration.

[0149] The final ejection pulse P7 is as described in the third embodiment, and includes a filling element g1, a sustaining element g2, an ejection element g3, a sustaining element g4, and a damping element g5 in this order.

[0150] By supplying the first dot drive signal Vin1c to the drive element 51f during one drive cycle Tu, it is possible to print a large first dot on the medium M. The large dot is formed by a combined droplet DRA formed by combining three droplets DR based on three ejection pulses P.

[0151] In this embodiment, as in the first embodiment, the period T1 from the start p7 of the fill element g1 of the last ejection pulse P7 to the start p8 of the ejection element g3 of the last ejection pulse P7 is equal to or greater than 0.3 TC and less than 0.5 TC. By setting the period T1 within this range, as in the first embodiment, it is possible to reduce the variation in the ink landing positions of the multiple ejectors 510 compared to when it is outside this range. Furthermore, the amount of ink ejected can be increased due to residual vibration.

[0152] Furthermore, the ejection element i3 of the second ejection pulse P10, which is a predetermined ejection pulse among the multiple ejection pulses included in the first common drive signal ComAc, includes a damping element i30. The damping element i30 maintains a potential E23 between the start potential and the end potential of the ejection element i3 during the potential change from the start potential p15 to the end potential p16, and then changes potential from the potential E23 to a reference potential E0. The inclusion of this damping element i30 reduces the droplet dropping speed of the droplet DR caused by the second ejection pulse P10 compared to when the damping element i30 is not included, and also enables effective damping adjustment of residual vibrations of the second ejection pulse P10. This facilitates the formation of a combined droplet DRA and suppresses unstable ejection of the final ejection pulse P7.

[0153] The waveform shape of the second ejection pulse is different between the first dot drive signal Vin1c of the fourth embodiment and the first dot drive signal Vin1b of the third embodiment. The first dot drive signal Vin1c of the fourth embodiment has a second ejection pulse P10, which allows the first dot to be ejected with a waveform length that is shorter than the waveform length of the first dot drive signal Vin1b of the third embodiment.

[0154] Furthermore, the potential change rate r1 of the filling element a1 of the first ejection pulse P1 is lower than the potential change rates of the filling elements i1 and g1 of the ejection pulses P other than the first ejection pulse P1. Specifically, the potential change rate r1 is lower than the potential change rate r2 of the filling element i1 of the second ejection pulse P10 and the potential change rate r3 of the filling element g1 of the last ejection pulse P7. By lowering the potential change rate r1 in this way, it is possible to prevent the ejection by the first ejection pulse P1 of the current cycle from becoming unstable even if residual vibration from the previous cycle remains.

[0155] FIG. 22 is a diagram showing the second dot drive signal Vin2c in the fourth embodiment. As shown in FIG. 22, the second dot drive signal Vin2c includes a second ejection pulse P11 and a final ejection pulse P7, in this order. The second dot drive signal Vin2c is generated by selecting the second ejection pulse P11 of the second common drive signal ComBc and the final ejection pulse P7 of the first common drive signal ComAc. In this embodiment, a combined droplet DRA is formed by two droplets DR: one based on the second ejection pulse P11 and the other based on the final ejection pulse P7. Therefore, in this embodiment, the second dot, which is a medium dot, is formed by the combined droplet DRA.

[0156] The second ejection pulse P11 is a trapezoidal wave, and has a filling element j1, a sustain element j2, and an ejection element j3 in this order.

[0157] The fill element j1 is an element that drives the drive element 51f to generate a negative pressure in the pressure chamber C by changing the potential. The fill element j1 changes its potential from a reference potential E0 to a fourth potential E24 that is lower than the reference potential E0. The fourth potential E24 is the minimum voltage of the second ejection pulse P11. The sustain element j2 is an element that maintains the fourth potential E24. The ejection element j3 is an element that drives the drive element 51f to generate a positive pressure in the pressure chamber C by changing the potential, thereby ejecting a droplet DR from the nozzle N. The ejection element j3 changes its potential from the fourth potential E24 to the reference potential E0.

[0158] The final ejection pulse P7 is as described in the third embodiment, and includes a filling element g1, a sustaining element g2, an ejection element g3, a sustaining element g4, and a damping element g5 in this order.

[0159] By supplying the second dot drive signal Vin2c to the drive element 51f during one drive period Tu, the second dot, which is a medium dot, can be printed on the medium M.

[0160] In this embodiment, as in the first embodiment, the pulses required to form different dots are distributed among multiple common drive signals Com, and some pulses are commonly used to form different dots. This shortens the length of one drive cycle and enables gradation expression with high-frequency drive. Also, as described above, by using the last ejection pulse P7 of the first common drive signal ComAc in common to both the first dot drive signal Vin1c and the second dot drive signal Vin2c, it is easy to align the landing positions of the first and second dots. Furthermore, in the second dot drive signal Vin2c, the pulse combined with the last ejection pulse P7 of the first common drive signal ComAc is the second ejection pulse P11 of the second common drive signal ComBc, which is not selected in the first dot drive signal Vin1c. This allows the pulse shape of the second ejection pulse P11 to be adjusted regardless of the ejection volume of the first dot, making it easy to adjust the ejection volume of the second dot relative to the ejection volume of the first dot.

[0161] E. Variations The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Any of the following embodiments can be combined as desired within the scope of their mutual compatibility.

[0162] In the above-described embodiment, the number of ejection pulses P within the drive period Tu may be four or more. Furthermore, for example, a third common drive signal may be used in addition to the first common drive signal ComA and the second common drive signal ComB. The number of common drive signals Com used is not limited to two.

[0163] The width of the nozzle N in each of the above-described embodiments may be constant or may vary in stages, for example. The configuration of the head chip 51 is not limited to the example shown in Fig. 3, and may be any configuration.

[0164] In each of the above-mentioned embodiments, a serial-type liquid ejection device 100 in which a carriage 41 carrying a head 50 moves back and forth has been exemplified, but the present disclosure can also be applied to a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium M.

[0165] The liquid ejection device 100 exemplified in the above embodiment may be employed in various devices such as facsimile machines and copiers, in addition to devices dedicated to printing, and the applications of the present disclosure are not particularly limited. However, the applications of the liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Furthermore, a liquid ejection device that ejects a solution of an organic substance related to a living body is used as a manufacturing device for manufacturing biochips, for example.

[0166] F. Reference example 23 is a diagram illustrating a common drive signal Com of a reference example. As shown in FIG. 23, the first common drive signal ComAd of the reference example includes a first ejection pulse P1 and a final ejection pulse P7, in this order, within a drive period Tu. The first ejection pulse P1 is provided in a control period Tua1. The final ejection pulse P7 is provided in a control period Tua2.

[0167] The second common drive signal ComBd of the reference example includes a vibration imparting pulse P3 and an ejection pulse P12 in this order. The vibration imparting pulse P3 is provided in the control period Tub1. The ejection pulse P12 is provided in the control period Tub2.

[0168] By appropriately combining pulses selected from the first common drive signal ComAd and the second common drive signal ComBd in the drive period Tu to generate the supply signal Vin, dots of different sizes, namely a first dot which is a large dot, a second dot which is a medium dot, and a third dot which is a small dot, can be ejected from the nozzle N.

[0169] 24 is a diagram showing a first dot drive signal Vin1d of a reference example. As shown in FIG. 24, the first dot drive signal Vin1d has the same waveform as the first common drive signal ComAd and includes a first ejection pulse P1 and a final ejection pulse P7. The first dot drive signal Vin1d is generated by selecting the first ejection pulse P1 and the final ejection pulse P7 of the first common drive signal ComAd. The final ejection pulse P7 is also the second ejection pulse in chronological order among the multiple ejection pulses P. A first connecting element CN1 is provided between the first ejection pulse P1 and the final ejection pulse P7. The first connecting element CN1 maintains a reference potential E0.

[0170] The first ejection pulse P1 is as described in the first embodiment, and the last ejection pulse P7 is as described in the third embodiment.

[0171] By supplying the first dot drive signal Vin1d to the drive element 51f during one drive period Tu, the first dot, which is a large dot, can be printed on the medium M.

[0172] In the reference example, as in each embodiment, the first ejection pulse P1, which is a trapezoidal pulse, is provided, thereby enabling the drive period Tu to be shortened without excessively increasing the ink flight speed, compared to the conventional ejection pulse Px shown in Fig. 28. Therefore, even if the interval between the first ejection pulse P1 and the final ejection pulse P7 is narrowed by high-speed driving, the droplets DR1 and DR2 are easily combined, and the instability of ink ejection can be reduced compared to conventional methods. Furthermore, the first ejection pulse P1, which is a trapezoidal pulse, has a smaller ejection volume and faster ink refill than the ejection pulse Px with a so-called pull-push-pull waveform, and is therefore advantageous in terms of ensuring the ejection volume of the final ejection pulse P7.

[0173] Furthermore, the final ejection pulse P7 can increase the droplet volume by increasing the potential change width compared to the first ejection pulse P1. Therefore, by including the first ejection pulse P1 and the final ejection pulse P7 in the first dot drive signal Vin1d, it is possible to ensure the ink droplet volume while reducing the instability of ink ejection during high-speed driving.

[0174] In the reference example, the period T1 from the start p10 of the fill element g1 of the last ejection pulse P7 to the start p11 of the ejection element g3 of the last ejection pulse P7 is greater than or equal to 0.5 TC and less than 0.75 TC. With the start of the fill element g1, the ink in the ejection section 510 begins to fluctuate negatively, and after 0.5 TC, the pressure fluctuates to a positive value. By setting the period T1 of the last ejection pulse P7 to greater than or equal to 0.5 TC and less than 0.7 TC, positive pressure due to the ejection element g3 can be applied in synergy with the natural vibration occurring in the ink in the ejection section 510. Therefore, by setting the pulse width period T1 of the last ejection pulse P7 within the above range, the pressure due to the ejection element g3 can be suppressed compared to when it is outside the range, thereby suppressing satellites and ensuring ejection stability. Furthermore, the amount of ink ejected can be increased.

[0175] Furthermore, the first pulse interval T0 is preferably equal to or greater than 1.7TC and less than 2.7TC. The first pulse interval T0 is the period from the start p1 of the fill element a1 of the first ejection pulse P1 to the start p10 of the fill element g1 of the last ejection pulse P7, which is the second ejection pulse. By having the first pulse interval T0 within the above range, it is easier to combine the droplets DR1 and DR2 before the droplets DR1 ejected by the first ejection pulse P1 land on the medium M, while ensuring the ejection amount of the droplets DR2 ejected by the second ejection pulse P7 due to the residual vibration of the first ejection pulse P1, compared to when the first pulse interval T0 is outside the range.

[0176] Furthermore, the pulse width T2 of the first ejection pulse P1 of the first dot drive signal Vin1d is equal to or greater than 0.3 TC and less than 0.5 TC. The pulse width T2 is the period from the start p1 of the fill element a1 of the first ejection pulse P1 to the start p2 of the ejection element a3. By keeping the pulse width T2 within this range, the overall waveform length can be shortened while minimizing variations in the flight speed and weight of ink droplets ejected from the multiple ejectors 510, compared to when the pulse width T2 is outside this range. Therefore, this is particularly suitable for high-speed driving.

[0177] 25 is a diagram showing a second dot drive signal Vin2d of a reference example. The second dot drive signal Vin2d includes a vibration imparting pulse P3 and a final ejection pulse P7. Specifically, the second dot drive signal Vin2d is generated by selecting the vibration imparting pulse P3 of the second common drive signal ComBd and the final ejection pulse P7 of the first common drive signal ComAd during one drive period Tu. In addition, a second connection element CN2 is provided between the vibration imparting pulse P3 and the final ejection pulse P7. The second connection element CN2 maintains the reference potential E0.

[0178] The vibration imparting pulse P3 is as described in the first embodiment, and the final ejection pulse P7 is as described in the third embodiment.

[0179] By supplying the second dot drive signal Vin2d to the drive element 51f during one drive period Tu, the second dot, which is a medium dot, can be printed on the medium M.

[0180] 26 is a diagram showing the third dot drive signal Vin3d of a reference example. As shown in Fig. 26, the third dot drive signal Vin3d is generated by selecting the ejection pulse P12 of the second common drive signal ComBd during one drive period Tu. The ejection pulse P12 applies pressure fluctuations to the liquid in the pressure chamber C by pressurizing and depressurizing the ink in the pressure chamber C so as to eject the ink from the nozzle N.

[0181] The ejection pulse P12 changes in potential from the reference potential E0 to a higher potential E25, maintains the potential E25, then changes in potential to a lower potential E26 than the reference potential E0, and maintains the potential E26. The ejection pulse P12 then changes in potential from the potential E26 to a higher potential E27 than the reference potential E0, maintains the potential E27, then changes in potential to a lower potential E28 than the reference potential E0, and maintains the potential E28. The ejection pulse P12 then changes in potential from the potential E28 to a potential E29 higher than the reference potential E0, maintains the potential E29, and then returns to the reference potential E0. A third dot is ejected during the potential change of the ejection pulse P12 from the potential E26 to the potential E27 and then from the potential E27 to the potential E28.

[0182] By supplying the third dot drive signal Vin3d to the drive element 51f during one drive period Tu, the third dot, which is a small dot, can be printed on the medium M.

[0183] G. Other Reference Examples 27 is a diagram showing a first dot drive signal Vin1d in another reference example. In the first dot drive signal Vin1d in the other reference example shown in FIG. 27, the preferable range of the pulse width T2 of the first ejection pulse P1 is different from the range in the above-mentioned reference example.

[0184] Specifically, the pulse width T2 of the first ejection pulse P1 of the first dot drive signal Vin1d in another reference example is greater than or equal to 0.5 TC and less than 0.7 TC. Negative pressure fluctuations in the ink in the ejection section 510 begin with the start of the filling element a1, and then change to positive pressure fluctuations after 0.5 TC. By setting the pulse width T2 of the first ejection pulse P1 to greater than or equal to 0.5 TC and less than 0.7 TC, positive pressure can be applied by the ejection element a3 in synergy with the natural vibration occurring in the ink in the ejection section 510. Therefore, by setting the pulse width T2 of the first ejection pulse P1 within this range, the pressure applied by the ejection element a3 can be suppressed compared to when the pulse width T2 is outside this range, and the speed of the first ejection pulse P1 can be suppressed. This allows for stable ejection. Furthermore, by setting the pulse width T2 of the first ejection pulse P1 within this range, the weight of the droplet DR1 produced by the first ejection pulse P1 can be more easily ensured compared to when the pulse width T2 is outside this range. [Explanation of symbols]

[0185] 3...head chip, 24...driving signal generating section, 50...head, 51...head chip, 51f...driving element, 52...switching circuit, 100...liquid ejection device, 510...ejection section, C...pressure chamber, CN1...first connecting element, CN2...second connecting element, Vin1...first dot driving signal, Vin2...second dot driving signal, Vin3...third dot driving signal, ComA...first common driving signal, ComB...second common driving signal, Comx...driving signal, DR...droplet, DRA...combined droplet, E0...reference potential, M...medium Body, N...nozzle, P1...first ejection pulse, P11...second ejection pulse, P2...last ejection pulse, P3...vibration imparting pulse, P5...second ejection pulse, P8...second ejection pulse, T0...first pulse interval, T1...period, T2...pulse width, T3...pulse width, T4...pulse interval, Tu...driving period, VBS...offset potential, Vin...supply signal, a1...filling element, a2...sustaining element, a3...ejection element, i30...sustaining element, r1...potential change rate, r2...potential change rate, r3...potential change rate.

Claims

1. a discharge unit having a nozzle that discharges liquid to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates a pressure fluctuation in the liquid in the pressure chamber when a drive signal is supplied; a drive signal generation unit that generates the drive signal; Equipped with the drive signal includes a first common drive signal having a plurality of ejection pulses corresponding to a plurality of droplets that coalesce before landing on the medium; the plurality of ejection pulses each have a filling element that drives the drive element to generate a negative pressure in the pressure chamber by changing a potential, and an ejection element that drives the drive element to generate a positive pressure in the pressure chamber by changing a potential, thereby ejecting a droplet from the nozzle; an ejection element of a first ejection pulse, which is the first in time series among the plurality of ejection pulses, changes in potential from a first potential to a reference potential and connects to a first connection element; a filling element of a final ejection pulse among the plurality of ejection pulses changes in potential from a potential equal to or higher than the reference potential to a second potential, and an ejection element of the final ejection pulse changes in potential from the second potential to a third potential; the final ejection pulse has a damping element that attenuates pressure fluctuations in the pressure chamber by changing potential after the ejection element of the final ejection pulse, the reference potential is located between the first potential and the third potential; the reference potential is located between the second potential and the third potential; a period from the start of the fill element of the last ejection pulse to the start of the ejection element of the last ejection pulse is greater than or equal to 0.3 TC and less than 0.5 TC; TC represents the natural vibration period of the ejection portion, A liquid ejection device characterized by:

2. the first connection element is an element that maintains the reference potential until the start of a second ejection pulse in chronological order among the plurality of ejection pulses, The liquid ejection device according to claim 1 , wherein a first pulse interval from the start of the fill element of the first ejection pulse to the start of the fill element of the second ejection pulse is equal to or greater than 1.7 TC and less than 2.7 TC.

3. The pulse width of the first ejection pulse is equal to or greater than 0.5 TC and less than 0.7 TC. The liquid ejection device according to claim 1 .

4. The pulse width of the first ejection pulse is equal to or greater than 0.3 TC and less than 0.5 TC. The liquid ejection device according to claim 1 .

5. the drive signal includes a second common drive signal having a vibration-imparting pulse that imparts pressure fluctuations to the liquid in the pressure chamber without ejecting the liquid from the nozzle by pressurizing and depressurizing the liquid in the pressure chamber, a first dot is printed on the medium by supplying a first dot drive signal generated by selecting the first ejection pulse and the last ejection pulse of the first common drive signal to the drive element during one drive cycle of the drive signal; a second dot smaller than the first dot is printed on the medium by supplying a second dot drive signal generated by selecting the vibration imparting pulse of the second common drive signal and the final ejection pulse of the first common drive signal to the drive element during one drive cycle of the drive signal; In the first dot drive signal, a first pulse interval, which is an interval between a start end of a fill element of the first ejection pulse and a start end of a fill element of the last ejection pulse, is equal to or greater than 1.7 TC and less than 2.7 TC; In the second dot drive signal, a period of a second connection element that connects the end of the vibration imparting pulse and the start of the ejection element of the last ejection pulse is equal to or greater than 0.3 TC and less than 0.5 TC. The liquid ejection device according to claim 1 .

6. the drive signal includes a second common drive signal having a second ejection pulse including a fill element that drives the drive element to generate a negative pressure in the pressure chamber by changing a potential, and an ejection element that drives the drive element to generate a positive pressure in the pressure chamber by changing a potential, thereby ejecting a droplet from the nozzle; a first dot is printed on the medium by supplying a first dot drive signal generated by selecting the first ejection pulse and the last ejection pulse of the first common drive signal to the drive element during one drive cycle of the drive signal; a second dot that is smaller than the first dot is printed on the medium by supplying a second dot drive signal that is generated by selecting the second ejection pulse of the second common drive signal to the drive element during one drive cycle of the drive signal; In the first dot drive signal, a first pulse interval, which is an interval between a start end of a fill element of the first ejection pulse and a start end of a fill element of the last ejection pulse, is equal to or greater than 1.7 TC and less than 2.7 TC; a period of a filling element of the first ejection pulse in the first common drive signal and a period of a filling element of the second ejection pulse in the second common drive signal overlap with each other; a period of an ejection element of the first ejection pulse in the first common drive signal and a period of an ejection element of the second ejection pulse in the second common drive signal overlap with each other; The liquid ejection device according to claim 1 .

7. the drive signal includes a fill element that drives the drive element to generate a negative pressure in the pressure chamber by changing a potential, and a second common drive signal having a second ejection pulse that drives the drive element to generate a positive pressure in the pressure chamber by changing a potential, thereby ejecting a droplet from the nozzle; a first dot is printed on the medium by supplying a first dot drive signal generated by selecting a plurality of ejection pulses of the first common drive signal to the drive element during one drive cycle of the drive signal; a second dot smaller than the first dot is printed on the medium by supplying a second dot drive signal generated by selecting the first ejection pulse of the first common drive signal and the second ejection pulse of the second common drive signal to the drive element during one drive cycle of the drive signal; In the first dot drive signal, a pulse interval between the start of a fill element of the first ejection pulse and the start of a fill element of a second ejection pulse in time series is equal to or greater than 1.7 TC and less than 2.7 TC; In the second dot drive signal, a pulse interval between a start end of a fill element of the first ejection pulse and a start end of a fill element of the second ejection pulse is equal to or greater than 1.7 TC and less than 2.7 TC. The liquid ejection device according to claim 1 .

8. the drive signal includes a fill element that drives the drive element to generate a negative pressure in the pressure chamber by changing a potential from the reference potential to a fourth potential, and a second common drive signal having a second ejection pulse that drives the drive element to generate a positive pressure in the pressure chamber by changing a potential from the fourth potential to the reference potential, thereby ejecting a droplet from the nozzle; a first dot is printed on the medium by supplying a first dot drive signal generated by selecting a plurality of ejection pulses of the first common drive signal to the drive element during one drive cycle of the drive signal; a second dot smaller than the first dot is printed on the medium by supplying a second dot drive signal generated by selecting the second ejection pulse of the second common drive signal and the last ejection pulse of the first common drive signal to the drive element during one drive cycle of the drive signal; The liquid ejection device according to claim 1 .

9. an ejection element of a predetermined ejection pulse among the plurality of ejection pulses of the first common drive signal includes a sustain element that sustains a potential between a start potential and an end potential during a potential change from the start potential to an end potential; The liquid ejection device according to claim 8 .

10. a potential change rate of the filling element of the first ejection pulse is lower than a potential change rate of the filling element of an ejection pulse other than the first ejection pulse; The liquid ejection device according to claim 8 .

Images