LIQUID EJECTION DEVICE AND METHOD FOR CONTROLLING LIQUID EJECTION DEVICE

Abstract

To prevent liquid droplets from being discharged unstably.SOLUTION: A liquid discharge device comprises a plurality of discharge parts including a nozzle, a pressure chamber and a driving element, and a signal generating part that generates a driving signal for making the nozzle discharge a plurality of liquid droplets integrally until the liquid droplets impact on a medium. The driving signal includes a plurality of drive waveforms and a first connection waveform connecting the last drive waveform to the second drive waveform from the last, of the plurality of drive waveforms so that a potential of the drive signal is maintained at a reference potential. Each of the plurality of drive waveforms includes an expand waveform which expands volumes of the pressure chamber so that the potential of the drive signal varies from the reference potential and a constricting waveform that constricts volumes of the pressure chamber expanded by the expand waveform so that the potential of the drive signal varies so as to make the nozzle discharge liquid droplets. Pressure fluctuation of liquid in the pressure chamber caused by the constricting waveform is larger in the last drive waveform than in the second waveform from the last, and a period of the first connection waveform is 0.8 times or more natural vibration periods of the discharge parts.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a method for controlling the liquid ejection apparatus. [Background technology]

[0002] Liquid ejection devices are known that print images by ejecting liquid such as ink from multiple nozzles using piezoelectric elements. In this type of liquid ejection device, for example, the piezoelectric element ejects ink from the nozzles by contracting a pressure chamber connected to the nozzle in response to a drive signal including a pulse for ejecting ink from the nozzle. Another known method for controlling a liquid ejection device is to supply multiple pulses to a piezoelectric element and combine multiple droplets ejected from each nozzle before landing on a print medium. For example, Patent Document 1 discloses an inkjet head in which multiple ink ejection pulse signals that drive an actuator including a piezoelectric element are selected from pulse signals generated consecutively in a reference drive signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-146011 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a conventional control method in which multiple pulses are supplied successively to a piezoelectric element, the velocity of droplets ejected by a subsequent pulse is increased by combining the residual vibration of the pressure fluctuation in the pressure chamber caused by a previous pulse with the pressure fluctuation in the pressure chamber caused by a subsequent pulse. Therefore, in the conventional control method, if the behavior of the residual vibration caused by the previous pulse changes, the ejection of droplets by the subsequent pulse may become unstable. [Means for solving the problem]

[0005] In order to solve the above problems, a liquid ejection device according to the present invention comprises a nozzle that ejects droplets, a pressure chamber that communicates with the nozzle, and a plurality of ejection units including a drive element; and a signal generation unit that generates a signal as a drive signal for the drive element to eject a plurality of droplets from the nozzle so that they combine before landing on a medium, the drive signal including a plurality of drive waveforms that impart pressure fluctuations to the liquid in the pressure chamber, and a first connection waveform that connects the last drive waveform and the second-to-last drive waveform of the plurality of drive waveforms and maintains the potential of the drive signal at a reference potential, each of the plurality of drive waveforms including an expansion waveform that changes the potential of the drive signal from the reference potential so as to expand the volume of the pressure chamber, and a contraction waveform that changes the potential of the drive signal so as to contract the volume of the pressure chamber that has expanded due to the expansion waveform, causing the droplet to be ejected from the nozzle, and the pressure fluctuations of the liquid in the pressure chamber caused by the contraction waveform The final drive waveform is larger than the second-to-last drive waveform, and the period of the first connection waveform is 0.8 times or more the natural vibration period of the ejection portion.

[0006] Furthermore, a control method for a liquid ejection device according to the present invention is a control method for a liquid ejection device having a nozzle that ejects droplets, a pressure chamber connected to the nozzle, and a plurality of ejection units including a drive element, wherein a signal is generated as a drive signal for the drive element to eject a plurality of droplets from the nozzle so that they combine before impacting a medium, the drive signal including a plurality of drive waveforms that impart pressure fluctuations to the liquid in the pressure chamber, and a first connection waveform that connects the last drive waveform and the second-to-last drive waveform of the plurality of drive waveforms and maintains the potential of the drive signal at a reference potential, each of the plurality of drive waveforms including an expansion waveform that changes the potential of the drive signal from the reference potential to expand the volume of the pressure chamber, and a contraction waveform that changes the potential of the drive signal to contract the volume of the pressure chamber expanded by the expansion waveform, causing droplets to be ejected from the nozzle, the pressure fluctuation of the liquid in the pressure chamber caused by the contraction waveform is greater for the last drive waveform than for the second-to-last drive waveform, and the period of the first connection waveform is 0.8 times or more the natural vibration period of the ejection unit. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a block diagram showing an example of the configuration of an inkjet printer according to a first embodiment of the invention. [Figure 2] FIG. 1 is a perspective view illustrating an example of a schematic internal structure of an inkjet printer. [Figure 3] FIG. 4 is a cross-sectional view illustrating an example of the structure of a discharge portion. [Figure 4] FIG. 2 is a plan view showing an example of the arrangement of nozzles in a head unit. [Figure 5] FIG. 2 is a block diagram showing an example of the configuration of a head unit. [Figure 6] 4 is a timing chart illustrating an example of a signal supplied to a head unit. [Figure 7] 10A and 10B are explanatory diagrams showing the results of an ink ejection experiment when the interval between the preceding waveform and the following waveform is changed. [Figure 8] FIG. 10 is a block diagram illustrating an example of the configuration of an inkjet printer according to a second embodiment. [Figure 9] 10 is a timing chart illustrating an example of a drive signal in the first modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part are appropriately different from those of the actual parts. Furthermore, since the embodiments described below are preferred examples of the present invention, various technically preferable limitations are applied, but the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited.

[0009] [1. Embodiment] In this embodiment, a liquid ejection device will be described using an inkjet printer as an example, which ejects ink onto recording paper to form an image. Note that in this embodiment, ink is an example of a "liquid," and recording paper is an example of a "medium."

[0010] [First embodiment] FIG. 1 is a block diagram showing an example of the configuration of an inkjet printer 1 according to an embodiment of the invention.

[0011] Print data IMG indicating the image to be formed by the inkjet printer 1 is supplied to the inkjet printer 1 from a host computer such as a personal computer or digital camera. The inkjet printer 1 executes a printing process to form the image indicated by the print data IMG supplied from the host computer on a medium. In this embodiment, the medium is assumed to be recording paper P shown in Figure 2, which will be described later.

[0012] The inkjet printer 1 has a control unit 2 that controls each part of the inkjet printer 1, a head unit 3 that is provided with ejection units D that eject ink, and a drive signal generation unit 4 that generates drive signals COM for driving the ejection units D. The inkjet printer 1 also has a transport unit 7 that changes the relative position of the recording paper P with respect to the head unit 3, and a maintenance unit 8 that executes maintenance processing to maintain the ejection units D provided in the head unit 3.

[0013] In this embodiment, it is assumed that the head units 3 and the drive signal generation units 4 correspond to each other. For example, the inkjet printer 1 may have multiple head units 3 and multiple drive signal generation units 4 that correspond one-to-one to the multiple head units 3. Alternatively, the inkjet printer 1 may have one head unit 3 and one drive signal generation unit 4 that corresponds one-to-one to the single head unit 3. In this embodiment, it is assumed that the inkjet printer 1 has four head units 3 and four drive signal generation units 4 that correspond one-to-one to the four head units 3. However, for ease of explanation, the following description may focus on one of the four head units 3 and one of the four drive signal generation units 4 that is provided to correspond to one of the head units 3, as shown in FIG. 1.

[0014] The control unit 2 is configured to include one or more central processing units (CPUs). Note that the control unit 2 may be configured to include a programmable logic device such as a field-programmable gate array (FPGA) instead of or in addition to a CPU. The control unit 2 is also configured to include one or both of a volatile memory such as a random access memory (RAM) and a non-volatile memory such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), or a programmable ROM (PROM).

[0015] As will be described in more detail below, the control unit 2 generates signals such as a print signal SI and a waveform designation signal dCOM to control the operation of each part of the inkjet printer 1. Here, the waveform designation signal dCOM is a digital signal that defines the waveform of the drive signal COM. The drive signal COM is an analog signal for driving the discharge section D. The print signal SI is a digital signal for specifying the type of operation of the discharge section D. Specifically, the print signal SI is a signal that specifies the type of operation of the discharge section D by specifying whether or not to supply the drive signal COM to the discharge section D.

[0016] The drive signal generation unit 4 includes, for example, a DAC (Digital Analog Converter), and generates the drive signal COM based on the waveform specification signal dCOM supplied from the control unit 2. For example, the drive signal generation unit 4 generates the drive signal COM including a waveform defined by the waveform specification signal dCOM. The drive signal generation unit 4 outputs the drive signal COM generated based on the waveform specification signal dCOM to a supply circuit 31 included in the head unit 3. The drive signal generation unit 4 is an example of a "signal generation section." Furthermore, for example, of the functional blocks realized by the control unit 2, a functional block that generates the waveform specification signal dCOM may be included in the "signal generation section."

[0017] The head unit 3 includes a supply circuit 31 and a recording head 32 .

[0018] The recording head 32 has M discharge sections D. The value M is a natural number greater than or equal to 1. Below, the mth discharge section D of the M discharge sections D provided in the recording head 32 may be referred to as discharge section D[m]. Here, the variable m is a natural number that satisfies "1≦m≦M." Also, below, when a component or signal of the inkjet printer 1 corresponds to a discharge section D[m] among the M discharge sections D, the subscript [m] may be added to the symbol representing the component or signal.

[0019] The supply circuit 31 switches whether to supply the drive signal COM to the discharge section D[m] based on the print signal SI. Note that, hereinafter, as shown in FIG. 5 and other figures described later, the drive signal COM supplied to the discharge section D[m] may be referred to as an individual drive signal Vin[m].

[0020] As described above, in this embodiment, the inkjet printer 1 executes a printing process. When the printing process is executed, the control unit 2 generates signals, such as print signals SI, for controlling the head unit 3 based on the print data IMG. When the printing process is executed, the control unit 2 also generates signals, such as waveform designation signals dCOM, for controlling the drive signal generation unit 4. When the printing process is executed, the control unit 2 also generates signals for controlling the transport unit 7. In this way, during the printing process, the control unit 2 controls the transport unit 7 to change the relative position of the recording paper P with respect to the head unit 3, while also adjusting the presence or absence of ink ejection from the ejection unit D[m], the amount of ink ejection, the timing of ink ejection, and so on. In this way, the control unit 2 controls each part of the inkjet printer 1 so that an image corresponding to the print data IMG is formed on the recording paper P.

[0021] As described above, in this embodiment, the inkjet printer 1 executes maintenance processes. For example, the maintenance processes include a flushing process that discharges ink from the ejection section D, a wiping process that uses a wiper to wipe off foreign matter such as ink adhering to the vicinity of the nozzles N of the ejection section D, and a pumping process that uses a tube pump or the like to suck ink from inside the ejection section D. The nozzles N will be described later with reference to FIG. 3.

[0022] The maintenance unit 8 has a discharged ink receiving section 80 for receiving the discharged ink when the ink is discharged from the discharge section D during the flushing process, a wiper for wiping off foreign matter such as ink adhering to the vicinity of the nozzles N of the discharge section D, and a tube pump for sucking ink, air bubbles, etc. from the discharge section D. The discharged ink receiving section 80 will be described later in FIG. 2. The wiper and tube pump are not shown in the drawings. Next, the general internal structure of the inkjet printer 1 will be described with reference to FIG. 2.

[0023] FIG. 2 is a perspective view showing an example of the general internal structure of the inkjet printer 1. As shown in FIG.

[0024] 2, this embodiment assumes that the inkjet printer 1 is a serial printer. Specifically, when performing a printing process, the inkjet printer 1 transports the recording paper P in the sub-scanning direction, while reciprocating the head unit 3 in the main scanning direction that intersects the sub-scanning direction, and ejects ink from the ejection units D[m] to form dots on the recording paper P according to the print data IMG.

[0025] For ease of explanation, a three-axis Cartesian coordinate system having mutually orthogonal X, Y, and Z axes will be introduced as appropriate below. Furthermore, hereinafter, the direction indicated by the X-axis arrow will be referred to as the +X direction, and the direction opposite to the +X direction will be referred to as the -X direction. The direction indicated by the Y-axis arrow will be referred to as the +Y direction, and the direction opposite to the +Y direction will be referred to as the -Y direction. Furthermore, hereinafter, the +X direction and the -X direction will sometimes be referred to as the X direction without any particular distinction, and the +Y direction and the -Y direction will sometimes be referred to as the Y direction without any particular distinction. Furthermore, the +Z direction and the -Z direction will sometimes be referred to as the Z direction without any particular distinction. Furthermore, in this embodiment, the +X direction is the sub-scanning direction, and the +Y direction and the -Y direction are the main scanning directions. In this embodiment, as shown in FIG. 2, the −Z direction is the ejection direction of ink from the ejection section D[m].

[0026] The inkjet printer 1 according to this embodiment has a housing 100 and a carriage 110 that can move back and forth in the Y direction within the housing 100 and that has four head units 3 mounted thereon.

[0027] In this embodiment, it is assumed that the carriage 110 stores four ink cartridges 120 that correspond one-to-one to the four colors of ink: cyan, magenta, yellow, and black. As described above, it is also assumed in this embodiment that the inkjet printer 1 has four head units 3 that correspond one-to-one to the four ink cartridges 120. Each ejection section D[m] receives a supply of ink from the ink cartridge 120 that corresponds to the head unit 3 in which the ejection section D[m] is provided. This allows each ejection section D[m] to fill itself with the supplied ink and eject the filled ink from the nozzles N. Note that the ink cartridges 120 may also be provided outside the carriage 110.

[0028] As described with reference to FIG. 1 , the inkjet printer 1 according to this embodiment also includes a transport unit 7. The transport unit 7 includes a carriage transport mechanism 71 for reciprocating the carriage 110 in the Y direction, and a carriage guide shaft 76 that supports the carriage 110 so that it can reciprocate in the Y direction. The transport unit 7 also includes a medium transport mechanism 73 for transporting the recording paper P, and a platen 75 that is disposed in the −Z direction relative to the carriage 110. For example, during a printing process, the carriage transport mechanism 71 reciprocates the head unit 3 together with the carriage 110 along the carriage guide shaft 76 in the Y direction, and the medium transport mechanism 73 transports the recording paper P on the platen 75 in the +X direction. Therefore, during a printing process, the transport unit 7 causes the carriage transport mechanism 71 and the medium transport mechanism 73 to perform the above-described operations, thereby changing the relative position of the recording paper P with respect to the head unit 3 and enabling ink to land on the entire recording paper P. In this embodiment, it is assumed that multiple ink droplets are ejected from the nozzle N, which combine before landing on the recording paper P. The ink droplets are, for example, ink particles. An ink droplet is an example of a "droplet," and multiple ink droplets are an example of "multiple droplets."

[0029] Next, the general structure of the recording head 32 will be described with reference to FIG.

[0030] Fig. 3 is a cross-sectional view for explaining an example of the structure of the discharge portion D. Note that Fig. 3 schematically shows a cross section of a portion of the recording head 32 when the recording head 32 is cut so as to include the discharge portion D[m].

[0031] The ejection unit D[m] has a piezoelectric element PZ[m], a cavity CV filled with ink, a nozzle N communicating with the cavity CV, and a vibration plate 321. The ejection unit D[m] ejects ink in the cavity CV from the nozzle N when the piezoelectric element PZ[m] is driven by an individual drive signal Vin[m]. The cavity CV is an example of a "pressure chamber," and the piezoelectric element PZ is an example of a "drive element."

[0032] The cavity CV is a space defined by a cavity plate 324, a nozzle plate 323 in which nozzles N are formed, and a vibration plate 321. The cavity CV is in communication with a reservoir 325 via an ink supply port 326. The reservoir 325 is in communication with the ink cartridge 120 corresponding to the ejection section D[m] via an ink intake port 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric body Zb[m] provided between the upper electrode Zu[m] and the lower electrode Zd[m]. The upper electrode Zu[m] is electrically connected to wiring Li to which an individual drive signal Vin[m] is supplied. The lower electrode Zd[m] is electrically connected to wiring Ld to which a bias voltage signal VBS is supplied. When an individual drive signal Vin[m] is supplied to the upper electrode Zu[m], a voltage is applied between the upper electrode Zu[m] and the lower electrode Zd[m]. The piezoelectric element PZ[m] is displaced in the +Z direction or the -Z direction depending on the voltage applied between the upper electrode Zu[m] and the lower electrode Zd[m].

[0033] In this way, the piezoelectric element PZ[m] vibrates in response to the voltage applied between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is joined to the diaphragm 321. Therefore, when the piezoelectric element PZ[m] is driven to vibrate by the individual drive signal Vin[m], the diaphragm 321 also vibrates. The vibration of the diaphragm 321 changes the volume of the cavity CV and the pressure within the cavity CV, causing the ink filled in the cavity CV to be ejected from the nozzle N.

[0034] In this embodiment, as an example, it is assumed that the potential of the individual drive signal Vin[m] supplied to the discharge section D[m] changes from low to high, causing the piezoelectric element PZ to be displaced in the -Z direction. That is, in this embodiment, it is assumed that when the potential of the individual drive signal Vin[m] supplied to the discharge section D[m] is high, the volume of the cavity CV provided in the discharge section D[m] becomes smaller than when the potential is low.

[0035] Next, an example of the arrangement of the nozzles N will be described with reference to FIG.

[0036] Fig. 4 is a plan view showing an example of the arrangement of nozzles N in a head unit 3. Fig. 4 shows an example of the arrangement of four head units 3 mounted on a carriage 110 and a total of 4M nozzles N provided in the four head units 3 when the inkjet printer 1 is viewed from above in the -Z direction.

[0037] Each head unit 3 provided on the carriage 110 is provided with a nozzle row NL. Here, the nozzle row NL is a plurality of nozzles N arranged to extend in a row in a predetermined direction. In this embodiment, it is assumed as an example that each nozzle row NL is composed of M nozzles N arranged to extend in the X direction.

[0038] Next, an overview of the head unit 3 will be described with reference to FIGS.

[0039] FIG. 5 is a block diagram showing an example of the configuration of the head unit 3.

[0040] 1, the head unit 3 has a supply circuit 31 and a recording head 32. The head unit 3 also has a wiring La to which a drive signal COM is supplied from the drive signal generation unit 4, and a wiring Li[m] that supplies an individual drive signal Vin[m] to the discharge section D[m].

[0041] The supply circuit 31 has M switches Wa[1] to Wa[M] that correspond one-to-one to the M discharge sections D[1] to D[M], and a connection state designation circuit 310. The connection state designation circuit 310 designates the connection state of each of the M switches Wa. For example, the connection state designation circuit 310 generates a connection state designation signal Qa[m] that designates the on / off state of the switch Wa[m] based on at least a part of the print signal SI and the latch signal LAT supplied from the control unit 2.

[0042] The switch Wa[m] switches between conduction and non-conduction between the wiring La and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] based on the connection state designation signal Qa[m]. That is, the switch Wa[m] switches between conduction and non-conduction between the wiring La and the wiring Li[m] connected to the upper electrode Zu[m] based on the connection state designation signal Qa[m]. In this embodiment, the switch Wa[m] is turned on when the connection state designation signal Qa[m] is at a high level and turned off when the connection state designation signal Qa[m] is at a low level. When the switch Wa[m] is turned on, the drive signal COM supplied to the wiring La is supplied as an individual drive signal Vin[m] to the upper electrode Zu[m] of the discharge section D[m] via the wiring Li[m].

[0043] Next, the operation of the head unit 3 will be described with reference to FIG.

[0044] In this embodiment, when the inkjet printer 1 executes a printing process or a flushing process, one or more unit periods TP are set as the operating period of the inkjet printer 1. In each unit period TP, the inkjet printer 1 according to this embodiment can drive each ejection section D[m] for the printing process or the flushing process.

[0045] FIG. 6 is a timing chart for explaining an example of a signal supplied to the head unit 3. In FIG.

[0046] The control unit 2 outputs a latch signal LAT having a pulse PLL. As a result, the control unit 2 defines a unit period TP as the period from the rising edge of a pulse PLL to the rising edge of the next pulse PLL. The unit period TP is, for example, the period required to form one dot corresponding to each nozzle N on the recording paper P. In this embodiment, it is assumed that two ink droplets are ejected from the nozzle N during the same unit period TP, and that the two ink droplets combine before landing on the recording paper P, thereby forming one dot on the recording paper P.

[0047] The print signal SI according to this embodiment includes M individual designation signals Sd[1] to Sd[M] that correspond one-to-one to the M discharge sections D[1] to D[M]. The individual designation signal Sd[m] specifies the drive mode of the discharge section D[m] during each unit period TP when the inkjet printer 1 executes a printing process or a flushing process. For example, prior to each unit period TP, the control unit 2 supplies the print signal SI, including the M individual designation signals Sd[1] to Sd[M], to the connection state designation circuit 310 in synchronization with the clock signal CL. The connection state designation circuit 310 then generates a connection state designation signal Qa[m] during that unit period TP based on the individual designation signal Sd[m].

[0048] For example, the discharge section D[m] is designated by the individual designation signal Sd[m] as either a discharge section D that forms dots or a discharge section D that does not form dots during the unit period TP in which the printing process is executed.

[0049] The drive signal COM has waveforms PD1 and PD2 that impart pressure fluctuations to the ink in the cavity CV, and a waveform PCO1 that connects the waveforms PD1 and PD2. For example, the drive signal COM has a pulse of waveform PD1 and a pulse of waveform PD2 provided in a unit period TP. The waveforms PD1 and PD2 are an example of "multiple drive waveforms." Therefore, the waveform PD1 is an example of the "penultimate drive waveform," and the waveform PD2 is an example of the "last drive waveform." Furthermore, the waveform PCO1 is an example of a "first connecting waveform." Hereinafter, the waveforms PD1 and PD2 will also be referred to as waveforms PD without any particular distinction.

[0050] Although details will be described later, waveforms PD1 and PD2 are waveforms for ejecting ink droplets from nozzle N. For example, in the same unit period TP, the ink droplets ejected from nozzle N by waveform PD1 and the ink droplets ejected from nozzle N by waveform PD2 combine before landing on recording paper P. First, waveform PD1 will be described.

[0051] The waveform PD1 is a waveform in which the potential of the drive signal COM changes from a reference potential V0, through potentials VL1 and VH1, and back to the reference potential V0. The potential VH1 is higher than the reference potential V0, and the potential VL1 is lower than the reference potential V0. Each of the reference potential V0, the potential VH1, and the potential VL1 is determined based on, for example, the ink ejection characteristics of the ejection section D. Examples of the ink ejection characteristics include the amount of ink ejected as ink droplets and the speed of the ejected ink droplets.

[0052] Hereinafter, the portion of the waveform PD1 where the potential of the drive signal COM changes from the reference potential V0 to the potential VL1 will be referred to as the waveform Pep1, and the portion where the potential of the drive signal COM is maintained at the potential VL1 will be referred to as the waveform Peh1. Also, the portion of the waveform PD1 where the potential of the drive signal COM changes from the potential VL1 to the potential VH1 will be referred to as the waveform Pcn1, and the portion where the potential of the drive signal COM is maintained at the potential VH1 will be referred to as the waveform Pch1. Also, the portion of the waveform PD1 where the potential of the drive signal COM changes from the potential VH1 to the reference potential V0 will be referred to as the waveform Pdm1. That is, the waveform PD1 includes the waveforms Pep1, Peh1, Pcn1, Pch1, and Pdm1.

[0053] The waveform Pep1 is a waveform for displacing the piezoelectric element PZ in the +Z direction. In other words, the waveform Pep1 is a waveform in which the potential of the drive signal COM changes so as to expand the volume of the cavity CV. Therefore, among the multiple elements that make up the pulse of the waveform PD1, the waveform Pep1 corresponds to the expansion element that changes the potential of the drive signal COM in order to drive the piezoelectric element PZ so as to expand the volume of the cavity CV. The waveform Pep1 is an example of an "expansion waveform."

[0054] The waveform Peh1 is a waveform for maintaining the position of the piezoelectric element PZ in the Z direction. For example, among the multiple elements that make up the pulse of the waveform PD1, the waveform Peh1 corresponds to an expansion maintaining element that maintains the potential of the drive signal COM in order to drive the piezoelectric element PZ so as to maintain the volume of the cavity CV expanded by the waveform Pep1. In the example shown in Figure 6, the waveform Peh1 is a waveform that maintains the potential of the drive signal COM at the potential VL1 at the end of the waveform Pep1.

[0055] The waveform Pcn1 is a waveform for displacing the piezoelectric element PZ in the -Z direction. In other words, the waveform Pcn1 is a waveform in which the potential of the drive signal COM changes so as to contract the volume of the cavity CV. Therefore, among the multiple elements that make up the pulse of the waveform PD1, the waveform Pcn1 corresponds to a contraction element that changes the potential of the drive signal COM in order to drive the piezoelectric element PZ so as to contract the volume of the cavity CV. Note that the waveform Pcn1 is an example of a "contraction waveform."

[0056] 3, this embodiment assumes that when the potential of the individual drive signal Vin[m] is high, the volume of the cavity CV of the discharge section D[m] is smaller than when the potential is low. Therefore, when the drive signal COM is supplied to the discharge section D[m] as the individual drive signal Vin[m], the waveform Pcn1, which changes the potential of the individual drive signal Vin[m] from low to high, causes ink in the discharge section D[m] to be discharged from the nozzle N as the first ink droplet. In other words, the waveform Pcn1 is a waveform that changes the potential of the drive signal COM so as to contract the volume of the cavity CV, which has expanded due to the waveform Pep1, and thereby eject an ink droplet from the nozzle N.

[0057] The waveform Pch1 is a waveform for maintaining the position of the piezoelectric element PZ in the Z direction. For example, among the multiple elements that make up the pulse of the waveform PD1, the waveform Pch1 corresponds to a contraction maintaining element that maintains the potential of the drive signal COM in order to drive the piezoelectric element PZ so as to maintain the volume of the cavity CV that has contracted due to the waveform Pcn1. In the example shown in FIG. 6, the waveform Pch1 is a waveform that maintains the potential of the drive signal COM at the potential VH1 at the end of the waveform Pch1. The waveform Pch1 is an example of a "first contraction maintaining waveform."

[0058] The waveform Pdm1 is a waveform for displacing the piezoelectric element PZ in the +Z direction. For example, the waveform Pdm1 is a waveform that changes the potential of the drive signal COM so as to expand the volume of the cavity CV contracted by the waveform Pcn1 and damp the residual vibration of the ink in the cavity CV. In other words, the waveform Pdm1 is a waveform that changes the potential of the drive signal COM from potential VH1 to reference potential V0 so as to expand the volume of the cavity CV maintained by the waveform Pch1 and damp the residual vibration of the ink in the cavity CV. Therefore, among the multiple elements that make up the pulse of the waveform PD1, the waveform Pdm1 corresponds to a damping element that changes the potential of the drive signal COM in order to drive the piezoelectric element PZ so as to expand the volume of the cavity CV and damp the residual vibration of the ink in the cavity CV. The waveform Pdm1 is an example of a "first damping waveform."

[0059] For example, the vibration of the ink in the cavity CV that has occurred up to the waveform Pcn1 is combined with the vibration generated by the waveform Pdm1 at a timing that corresponds to the length of the waveform Pch1. That is, the piezoelectric element PZ[m] expands the volume of the cavity CV in response to the change in potential of the waveform Pdm1, thereby damping the vibration of the ink in the cavity CV.

[0060] In this embodiment, it is assumed that the period Tsm, which is the sum of the period Tcn1 of the waveform Pcn1 and the period Tch1 of the waveform Pch1 in the waveform PD1, has the same length as the natural vibration period of the discharge section D. However, "same" does not only mean "strictly the same" but also means "substantially the same" (for example, "matching within a margin of error"). Furthermore, the natural vibration period of the discharge section D is, for example, a natural vibration period representative of the natural vibration periods of M discharge sections D. For example, the natural vibration period representative of the natural vibration periods of M discharge sections D may be the natural vibration period of one of the M discharge sections D. Alternatively, the natural vibration period representative of the natural vibration periods of M discharge sections D may be the average value of the natural vibration periods of N discharge sections D, or the maximum or minimum value of the natural vibration periods of N discharge sections D. Here, the value N is a natural number satisfying "2≦N≦M".

[0061] In this embodiment, the natural vibration period of the ejection section D and the period Tsm have the same length, so the interval from the start timing of the waveform Pcn1 corresponding to the contraction element to the start timing of the waveform Pdm1 corresponding to the damping element has the same length as the natural vibration period of the ejection section D. As a result, in this embodiment, the waveform Pdm1 can efficiently damp the vibration of the ink in the cavity CV.

[0062] Furthermore, in this embodiment, the interval between waveforms PD1 and PD2 is ensured by waveform PCO1, so that residual vibration due to waveform PD1 can be sufficiently attenuated by the time waveform PD2 starts. As a result, in this embodiment, the influence of residual vibration due to waveform PD1 on the ejection of ink droplets by the next waveform PD2 can be reduced, and the ejection of ink droplets by waveform PD2 can be prevented from becoming unstable. Ink droplet ejection becoming unstable means, for example, that the ejection direction of ink droplets deviates from a predetermined direction, that ink droplets are not ejected from nozzle N, etc.

[0063] The waveform PCO1 is a waveform in which the potential of the drive signal COM is maintained at the potential at which the waveform PD1 ends and the starting potential of the waveform PD2. The potential at which the waveform PD1 ends and the starting potential of the waveform PD2 are the reference potential V0, which is the potential at which the waveform Pdm1 ends and the potential at which the waveform Pep2 starts. In other words, the waveform PCO1 is a waveform in which the potential of the drive signal COM is maintained at the reference potential V0. Note that, because the potential of the drive signal COM at the end of the waveform Pdm1 is the reference potential V0, the volume of the cavity CV at the end of the waveform PD1 returns to the volume of the cavity CV in the reference state before the waveform PD1 was supplied to the piezoelectric element PZ. Therefore, the volume of the cavity CV is maintained at the volume of the cavity CV in the reference state by the waveform PCO1. The period Tco1 of the waveform PCO1 is, for example, 0.8 times or more the natural vibration period of the ejection section D.

[0064] Next, the waveform PD2 will be described. Detailed description of elements similar to those of the waveform PD1 will be omitted.

[0065] The waveform PD2 is a waveform in which the potential of the drive signal COM changes from a reference potential V0 through potentials VL1, VH1, and VL2, and then returns to the reference potential V0. The potential VL2 is determined, for example, so that residual vibration due to the waveform PD2 of the current unit period TP is sufficiently attenuated by the start of the waveform PD1 of the next unit period TP.

[0066] Hereinafter, the portion of the waveform PD2 where the potential of the drive signal COM changes from the reference potential V0 to the potential VL1 is also referred to as the waveform Pep2, and the portion where the potential of the drive signal COM is maintained at the potential VL1 is also referred to as the waveform Peh2. Furthermore, the portion of the waveform PD2 where the potential of the drive signal COM changes from the potential VL1 to the potential VH1 is also referred to as the waveform Pcn2, and the portion where the potential of the drive signal COM is maintained at the potential VH1 is also referred to as the waveform Pch2. Furthermore, the portion of the waveform PD2 where the potential of the drive signal COM changes from the potential VH1 to the potential VL2 is also referred to as the waveform Pdm2, and the portion where the potential of the drive signal COM is maintained at the potential VL2 is also referred to as the waveform Pdh. Furthermore, the portion of the waveform PD2 where the potential of the drive signal COM changes from the potential VL2 to the reference potential V0 is also referred to as the waveform Prn. That is, the waveform PD2 includes waveforms Pep2, Peh2, Pcn2, Pch2, Pdm2, Pdh, and Prn.

[0067] The waveform PD2 is similar to the waveform PD1, except that it includes waveforms Pdh and Prn. For example, the waveform Pep2 is a waveform that expands the volume of the cavity CV, similar to the waveform Pep1, and the waveform Peh2 is a waveform that maintains the expanded volume of the cavity CV, similar to the waveform Peh1. The waveform Pcn2 is a waveform that ejects ink from the nozzle N by contracting the expanded volume of the cavity CV, similar to the waveform Pcn1, except that the potential change per unit time of the waveform Pcn2 is greater than the potential change per unit time of the waveform Pcn1. The waveform Pch2 is a waveform that maintains the contracted volume of the cavity CV, similar to the waveform Pch1, and the waveform Pdm2 is a waveform that expands the contracted volume of the cavity CV, similar to the waveform Pdm1, except for the potential at the end, to damp the residual vibration of the ink in the cavity CV. The waveform Pep2 is an example of an "expansion waveform," and the waveform Pcn2 is an example of a "contraction waveform." Moreover, the waveform Pch2 is an example of a "second contraction maintaining waveform," and the waveform Pdm2 is an example of a "second vibration suppressing waveform."

[0068] The following description focuses on waveforms Pcn2, Pdm2, Pdh, and Prn, which are the main differences between waveform PD1 and waveform PD2. Note that, hereinafter, waveforms Pcn1 and Pcn2 are also referred to as waveform Pcn without any particular distinction. Similarly, waveforms Pdm1 and Pdm2 are also referred to as waveform Pdm. Furthermore, waveforms Pep1 and Pep2 are also referred to as waveform Pep, waveforms Peh1 and Peh2 are also referred to as waveform Peh, and waveforms Pch1 and Pch2 are also referred to as waveform Pch.

[0069] The waveform Pcn2 changes the potential of the drive signal COM so as to contract the volume of the cavity CV expanded by the waveform Pep2, thereby ejecting an ink droplet from the nozzle N. For example, when the drive signal COM is supplied to the ejection section D[m] as the individual drive signal Vin[m], the waveform Pcn2 changes the potential of the individual drive signal Vin[m] from low to high, causing the ink in the ejection section D[m] to be ejected from the nozzle N as a second ink droplet. Note that in this embodiment, the amount of potential change per unit time of the waveform Pcn2 is greater than the amount of potential change per unit time of the waveform Pcn1, so the speed of the second ink droplet is faster than the speed of the first ink droplet generated by the waveform Pcn1. As a result, the second ink droplet generated by the waveform Pcn2 merges with the first ink droplet generated by the waveform Pcn1 before landing on the recording paper P.

[0070] Here, when the amount of potential change per unit time of the waveform Pcn is large, the pressure fluctuation of the ink in the cavity CV caused by the waveform Pcn is larger than when the amount of potential change per unit time of the waveform Pcn is small. Also, when the pressure fluctuation of the ink in the cavity CV is large, the speed of the ink droplets ejected from the nozzle N is faster than when the pressure fluctuation of the ink in the cavity CV is small.

[0071] In this embodiment, as described above, the amount of potential change per unit time of the waveform Pcn2 is greater than the amount of potential change per unit time of the waveform Pcn1, and therefore the pressure fluctuation of the ink in the cavity CV caused by the waveform Pcn is greater for the waveform Pcn2 than for the waveform Pcn1. As a result, in this embodiment, the speed of ink droplets ejected from the nozzle N by the waveform Pcn2 can be made faster than the speed of ink droplets ejected from the nozzle N by the waveform Pcn1.

[0072] Although this embodiment assumes that the potential change amount of the waveform Pcn1 is the same as the potential change amount of the waveform Pcn2, the potential change amount of the waveform Pcn1 may be different from the potential change amount of the waveform Pcn2. For example, if the potential change amount of the waveform Pcn2 is greater than the potential change amount of the waveform Pcn1, the pressure fluctuation of the ink in the cavity CV caused by the waveform Pcn2 will be greater than the pressure fluctuation of the ink in the cavity CV caused by the waveform Pcn1. Even in this case, the velocity of ink droplets ejected from the nozzle N by the waveform Pcn2 can be made faster than the velocity of ink droplets ejected from the nozzle N by the waveform Pcn1. However, when the waveforms Pcn1 and Pcn2 have different potentials at the start and end of the waveform Pcn, the piezoelectric element PZ is more susceptible to manufacturing variations and the like than when both the potentials at the start and end of the waveform Pcn are the same for the waveforms Pcn1 and Pcn2.

[0073] For this reason, in this embodiment, the potential at the start of the waveform Pcn1 and the potential at the start of the waveform Pcn2 are set to the same potential VL1, and the potential at the end of the waveform Pcn1 and the potential at the end of the waveform Pcn2 are set to the same potential VH1. In this embodiment, the waveforms Pcn1 and Pcn2 are set so that the amount of potential change per unit time of the waveform Pcn2 is greater than the amount of potential change per unit time of the waveform Pcn1. This makes it possible to make the velocity of ink droplets ejected from the nozzle N by the waveform Pcn2 faster than the velocity of ink droplets ejected from the nozzle N by the waveform Pcn1, while suppressing the piezoelectric element PZ from being susceptible to manufacturing variations and the like. The period of the waveform Pch2 is different from the period of the waveform Pch1 so that the combined period of the waveform Pcn2 and the waveform Pch2 has the same length as the natural vibration period of the ejection section D.

[0074] Like the waveform Pdm1, the waveform Pdm2 changes the potential of the drive signal COM from potential VH1 to potential VL2 so as to expand the volume of the cavity CV maintained by the waveform Pch2 and damp residual vibration of the ink in the cavity CV. However, as described above, the potential at the end of the waveform Pdm2 is different from the potential at the end of the waveform Pdm1. For example, the potential at the end of the waveform Pdm2 is potential VL2, which is lower than the reference potential V0, which is the potential at the end of the waveform Pdm1. In other words, the reference potential V0 is a potential between the potential VH1 of the drive signal COM at the start of the waveform Pdm2 and the potential VL2 of the drive signal COM at the end of the waveform Pdm2.

[0075] In this embodiment, the potential VL2 at the end of the waveform Pdm2 is lower than the reference potential V0, which is the potential at the end of the waveform Pdm1, so that residual vibration of the ink in the cavity CV can be efficiently damped. For example, when the temperature of the ink in the ejection section D is high, the viscosity of the ink is lower than when the temperature of the ink in the ejection section D is low. For this reason, the potential VL2 at the end of the waveform Pdm2 may be adjusted so that it is lower when the temperature of the ink in the ejection section D is high than when the temperature of the ink in the ejection section D is low.

[0076] The waveform Pdh is a waveform for maintaining the position of the piezoelectric element PZ in the Z direction. For example, among the multiple elements constituting the pulse of the waveform PD2, the waveform Pdh corresponds to an expansion maintaining element that maintains the potential of the drive signal COM in order to drive the piezoelectric element PZ so as to maintain the volume of the cavity CV expanded by the waveform Pdm2. In the example shown in FIG. 6, the waveform Pdh is a waveform that maintains the potential of the drive signal COM at the potential VL2 at the end of the waveform Pdm2. The waveform Pdh is an example of an "expansion maintaining waveform."

[0077] The waveform Prn is a waveform in which the potential of the drive signal COM changes from the potential VL2 at the end of the waveform Pdh to the reference potential V0, and the amount of potential change per unit time is smaller than the amount of potential change per unit time of the waveform Pdm2.

[0078] For example, the ink vibrations occurring in the cavity CV up to the waveform Pdm2 are combined with the vibrations generated by the waveform Prn at a timing corresponding to the length of the waveform Pdh. That is, the piezoelectric element PZ[m] contracts the volume of the cavity CV in response to changes in the potential of the waveform Prn, thereby damping the ink vibrations in the cavity CV. In this embodiment, since the waveform PD2 includes the waveforms Pdm2 and Prn, damping of the residual ink vibrations in the cavity CV is performed in two stages. This reduces the impact of the ink vibrations occurring in the cavity CV during the current unit period TP on the ejection of ink droplets during the next unit period TP, improving the stability of ink droplet ejection at high frequencies. For example, the volume of the cavity CV at the end of the waveform PD2 returns to the reference state because the potential of the drive signal COM at the end of the waveform Prn is the reference potential V0.

[0079] Furthermore, in this embodiment, the amount of potential change per unit time of the waveform Prn is smaller than the amount of potential change per unit time of the waveform Pdm2, so it is possible to reduce the vibration of the ink in the cavity CV caused by the waveform Prn. As a result, in this embodiment, it is possible to reduce the effect of residual vibration caused by the waveform PD2 in the current unit period TP on the ejection of ink droplets caused by the waveform PD1 in the next unit period TP, and it is possible to prevent the ejection of ink droplets from becoming unstable. In other words, in this embodiment, it is possible to ensure the stability of the ejection of ink droplets. Note that the waveform Prn is an example of a "return waveform."

[0080] Furthermore, in this embodiment, because the waveform PD2 includes the waveforms Pdm2 and Prn, damping that attenuates residual vibrations of the ink in the cavity CV is performed in two stages. As a result, in this embodiment, residual vibrations that occur in the current unit period TP can be sufficiently attenuated by the start of the next unit period TP. For example, in this embodiment, even if the drive cycle of the piezoelectric element PZ fluctuates, the residual vibrations that occur in the current unit period TP have little effect on the ejection of ink droplets in the next unit period TP, thereby improving the stability of ink droplet ejection. In this way, in this embodiment, the effect of residual vibrations that occur in the current unit period TP on the ejection of ink droplets in the next unit period TP can be reduced, thereby improving the stability of ink droplet ejection at high frequencies.

[0081] Next, with reference to FIG. 7, the results of an ink ejection experiment in which the period Tco1 of the waveform PCO1 is changed will be described.

[0082] Fig. 7 is an explanatory diagram showing the results of an ink ejection experiment when the interval between the leading waveform PD1 and the trailing waveform PD2 is changed, i.e., Fig. 7 is an explanatory diagram showing the results of an ink ejection experiment when the period Tco1 of the waveform PCO1 is changed.

[0083] In the "Period of Connection Waveform" of FIG. 7, the length of the period Tco1 of the waveform PCO1 is shown as a ratio to the natural vibration period of the discharge portion D.

[0084] "Stability of the second shot" in FIG. 7 indicates the stability of ink droplet ejection by the waveform PD2. For example, in "Stability of the second shot" in FIG. 7, a double circle indicates that ink droplet ejection by the waveform PD2 is stable. Stability means, for example, that the ejection direction of the ink droplets is approximately aligned with a predetermined direction. Also, in "Stability of the second shot" in FIG. 7, a single circle indicates that the stability of ink droplet ejection by the waveform PD2 is within an acceptable range. Stability within an acceptable range means, for example, that the deviation of the ink droplet ejection direction from a predetermined direction is within an acceptable range. Also, in "Stability of the second shot" in FIG. 7, an x ​​indicates that the stability of ink droplet ejection by the waveform PD2 is outside the acceptable range. Stability outside the acceptable range means, for example, that the deviation of the ink droplet ejection direction from a predetermined direction is outside the acceptable range.

[0085] In addition, in the "coalescence" section of Figure 7, a double circle indicates that the first ink droplet generated by waveform Pcn1 and the second ink droplet generated by waveform Pcn2 coalesce within 0.5 mm from the nozzle face. In addition, in the "coalescence" section of Figure 7, a single circle indicates that the first ink droplet generated by waveform Pcn1 and the second ink droplet generated by waveform Pcn2 coalesce within 1 mm from the nozzle face. In addition, in the "coalescence" section of Figure 7, a triangle indicates that the first ink droplet generated by waveform Pcn1 and the second ink droplet generated by waveform Pcn2 do not coalesce within 1 mm from the nozzle face.

[0086] As shown in "Stability of the Second Shot" in Figure 7, when the period Tco1 of the waveform PCO1 is 0.7 times or less the natural vibration period of the ejector D, the deviation of the ink droplet ejection direction from the specified direction by the waveform PD2 falls outside the allowable range. When the period Tco1 of the waveform PCO1 is 0.8 times or more the natural vibration period of the ejector D, the stability of ink droplet ejection by the waveform PD2 falls within the allowable range. When the period Tco1 of the waveform PCO1 is 1.0 times or more the natural vibration period of the ejector D, the ink droplet ejection by the waveform PD2 is stable.

[0087] Furthermore, as shown in "Combination" in Figure 7, when the period Tco1 of waveform PCO1 is 0.6 times or less the natural vibration period of ejection section D, the first ink droplet generated by waveform Pcn1 and the second ink droplet generated by waveform Pcn2 do not combine within 1 mm from the nozzle face. When the period Tco1 of waveform PCO1 is 0.7 to 1.1 times the natural vibration period of ejection section D, the first ink droplet generated by waveform Pcn1 and the second ink droplet generated by waveform Pcn2 combine within 0.5 mm from the nozzle face. When the period Tco1 of waveform PCO1 is 1.2 times the natural vibration period of ejection section D, the first ink droplet generated by waveform Pcn1 and the second ink droplet generated by waveform Pcn2 combine within 1 mm from the nozzle face. When the period Tco1 of the waveform PCO1 is 1.3 times or more the natural vibration period of the ejection section D, the first ink droplet generated by the waveform Pcn1 and the second ink droplet generated by the waveform Pcn2 do not combine until they are within 1 mm of the nozzle surface.

[0088] When focusing on the stability of the ejection of the second ink droplet by the waveform Pcn2, it is preferable that the period Tco1 of the waveform PCO1 be 0.8 times or more the natural vibration period of the ejection section D. More preferably, the period Tco1 of the waveform PCO1 be 1 time or more the natural vibration period of the ejection section D. As described above, in this embodiment, by lengthening the period of the waveform PCO1, the residual vibration caused by the waveform PD1 can be sufficiently attenuated by the start of the waveform PD2 following the waveform PD1, thereby improving the stability of the ejection of ink droplets by the waveform PD2. As a result, in this embodiment, even if the drive period of the piezoelectric element PZ fluctuates, the influence of the residual vibration generated in the current unit period TP on the ejection of ink droplets in the next unit period TP can be reduced, thereby improving the stability of the ejection of ink droplets at high frequencies. Furthermore, when considering the merging of the first ink droplet by the waveform Pcn1 and the second ink droplet by the waveform Pcn2, it is preferable that the period Tco1 of the waveform PCO1 be 1.2 times or less the natural vibration period of the ejection section D.

[0089] As described above, in this embodiment, the inkjet printer 1 includes a nozzle N that ejects ink, a cavity CV that communicates with the nozzle N, and multiple ejection sections D that include a piezoelectric element PZ. The inkjet printer 1 also includes a drive signal generation unit 4 that generates a signal as a drive signal COM for the piezoelectric element PZ, causing multiple ink droplets to be ejected from the nozzle N so that they coalesce before landing on the recording paper P. The drive signal COM includes multiple waveforms PD that impart pressure fluctuations to the ink in the cavity CV, and a waveform PCO1 that connects the last waveform PD2 and the penultimate waveform PD1 of the multiple waveforms PD, maintaining the potential of the drive signal COM at a reference potential V0. Each of the multiple waveforms PD includes a waveform Pep that changes the potential of the drive signal COM from the reference potential V0 to expand the volume of the cavity CV, and a waveform Pcn that changes the potential of the drive signal COM to contract the volume of the cavity CV expanded by the waveform Pep, thereby ejecting ink droplets from the nozzle N. The pressure fluctuation of the ink in the cavity CV caused by the waveform Pcn is larger for the last waveform PD2 than for the second to last waveform PD1. The period of the waveform PCO1 is 0.8 times or more the natural vibration period of the ejection section D.

[0090] Thus, in this embodiment, the pressure fluctuation of the ink in the cavity CV caused by the waveform Pcn that ejects ink droplets from the nozzle N is greater for the last waveform PD2 than for the second-to-last waveform PD1. As a result, in this embodiment, the speed of the ink droplets ejected from the nozzle N by the waveform Pcn2 of the last waveform PD2 can be made faster than the speed of the ink droplets ejected from the nozzle N by the waveform Pcn1 of the second-to-last waveform PD1. As a result, in this embodiment, it is possible to reduce the occurrence of ink droplets ejected from the nozzle N by the waveform Pcn1 and ink droplets ejected from the nozzle N by the waveform Pcn2 not coalescing before landing on the recording paper P.

[0091] Furthermore, in this embodiment, the period of waveform PCO1 is 0.8 times or more the natural vibration period of ejection section D, so the residual vibration due to waveform PD1 can be sufficiently attenuated by the time waveform PD2 starts. As a result, in this embodiment, the influence of the residual vibration due to waveform PD1 on the ejection of ink droplets by waveform PD2, which follows waveform PD1, can be reduced, and unstable ejection of ink droplets by waveform PD2 can be prevented. In this way, this embodiment can improve the stability of ink ejection.

[0092] In this embodiment, the potential of the drive signal COM at the end of the waveform Pcn is the same for the final waveform PD2 and the second-to-last waveform PD1, and the amount of potential change per unit time of the waveform Pcn is greater for the final waveform PD2 than for the second-to-last waveform PD1. As a result, in this embodiment, the speed of the last ink droplet ejected can be made faster than the speed of the second-to-last ink droplet ejected without changing the amount of potential change of the waveform Pcn between the final waveform PD2 and the second-to-last waveform PD1.

[0093] For example, if the amount of potential change in the waveform Pcn is the same in the last waveform PD2 and the second-to-last waveform PD1, the voltage applied to the piezoelectric element PZ by the waveform Pcn is the same in the last waveform PD2 and the second-to-last waveform PD1. In other words, if the amount of potential change in the waveform Pcn is different in the last waveform PD2 and the second-to-last waveform PD1, the voltage applied to the piezoelectric element PZ by the waveform Pcn is different in the last waveform PD2 and the second-to-last waveform PD1. If the voltage applied to the piezoelectric element PZ by the waveform Pcn is different in the last waveform PD2 and the second-to-last waveform PD1, the piezoelectric element PZ is susceptible to the influence of manufacturing variations, etc. In other words, if the voltage applied to the piezoelectric element PZ by the waveform Pcn is the same in the last waveform PD2 and the second-to-last waveform PD1, the piezoelectric element PZ is less susceptible to the influence of manufacturing variations, etc. Therefore, in this embodiment, the speed of ink droplets ejected from nozzle N using waveform Pcn2 can be made faster than the speed of ink droplets ejected from nozzle N using waveform Pcn1, while suppressing the piezoelectric element PZ from being susceptible to manufacturing variations, etc.

[0094] In this embodiment, the penultimate waveform PD1 further includes a waveform Pch1 in which the potential of the drive signal COM is maintained at the potential VH1 at the end of the waveform Pcn1 so as to maintain the volume of the cavity CV contracted by the waveform Pcn1, and a waveform Pdm1 in which the potential of the drive signal COM is changed to the reference potential V0 so as to expand the volume of the cavity CV maintained by the waveform Pch1 and attenuate residual vibration of the ink in the cavity CV. In the penultimate waveform PD1, the period Tam, which is the sum of the period Tcn1 of the waveform Pcn1 and the period Tch1 of the waveform Pch1, has the same length as the natural vibration period of the ejection section D.

[0095] Thus, in this embodiment, the period Tam obtained by combining the period Tcn1 of the waveform Pcn1 and the period Tch1 of the waveform Pch1 has the same length as the natural vibration period of the ejection section D. As a result, in this embodiment, the interval from the start timing of the waveform Pcn1 to the start timing of the waveform Pdm1 has the same length as the natural vibration period of the ejection section D, so that the vibration of the ink in the cavity CV can be efficiently damped.

[0096] Furthermore, in this embodiment, the period of the waveform PCO1 may be equal to or greater than the natural vibration period of the ejection section D. In this case, the residual vibration due to the waveform PD1 can be sufficiently attenuated by the start of the waveform PD2 that follows the waveform PD1, thereby improving the stability of ink droplet ejection by the waveform PD2.

[0097] Furthermore, in this embodiment, the period of waveform PCO1 may be 1.2 times or less the natural vibration period of the ejection section D. In this case, it is possible to reduce the occurrence of ink droplets ejected from nozzle N by waveform Pcn1 and ink droplets ejected from nozzle N by waveform Pcn2 not coalescing before landing on recording paper P.

[0098] In this embodiment, the final waveform PD2 further includes a waveform Pch2 in which the potential of the drive signal COM is maintained at the potential VH1 at the end of the waveform Pcn2 so as to maintain the volume of the cavity CV contracted by the waveform Pcn2, and a waveform Pdm2 in which the potential of the drive signal COM changes so as to expand the volume of the cavity CV maintained by the waveform Pch2 and damp residual vibration of the ink in the cavity CV. The reference potential V0 is a potential between the potential VH1 of the drive signal COM at the start of the waveform Pdm2 and the potential VL2 of the drive signal COM at the end of the waveform Pdm2.

[0099] As described above, in this embodiment, the amount of potential change of the waveform Pdm2 is greater than the amount of potential change from the potential VH1 to the reference potential V0. Therefore, in this embodiment, the residual vibration of the ink in the cavity CV can be damped more efficiently than in an embodiment in which the amount of potential change of the waveform Pdm corresponding to the vibration damping element is the amount of potential change from the potential VH1 to the reference potential V0. For example, in this embodiment, the amount of potential change of the waveform Pdm2 may be adjusted so that it is greater when the temperature of the ink in the ejection section D is high than when the temperature of the ink in the ejection section D is low.

[0100] In addition, in this embodiment, the final waveform PD2 further includes a waveform Pdh in which the potential of the drive signal COM is maintained at the potential VL2 at the end of the waveform Pdm2 so as to maintain the volume of the cavity CV expanded by the waveform Pdm2, and a waveform Prn in which the potential of the drive signal COM changes from the potential VL2 at the end of the waveform Pdh to the reference potential V0, and the amount of potential change per unit time is smaller than the amount of potential change per unit time of the waveform Pdm2.

[0101] As described above, in this embodiment, the final waveform PD2 performs two-stage damping to damp the residual vibration of the ink in the cavity CV using the waveforms Pdm2 and Prn. This allows the ink vibration in the cavity CV generated by the waveform PD2 to be efficiently damped. As a result, this embodiment can improve the stability of ink droplet ejection at high frequencies, for example.

[0102] Furthermore, in this embodiment, the amount of potential change per unit time of the waveform Prn is smaller than the amount of potential change per unit time of the waveform Pdm2, so the vibration of the ink in the cavity CV caused by the waveform Prn can be reduced. As a result, in this embodiment, the residual vibration caused by the waveform PD2 can be sufficiently damped. As a result, in this embodiment, even when the drive signal COM including the waveforms PD1 and PD2 is repeatedly supplied to the piezoelectric element PZ at a predetermined drive cycle, it is possible to prevent the ejection of ink droplets from becoming unstable.

[0103] [Second embodiment] Figure 8 is a block diagram showing an example of the configuration of an inkjet printer 1A according to the second embodiment. Elements that are the same as those described in Figures 1 to 7 are given the same reference numerals, and detailed description will be omitted.

[0104] Inkjet printer 1A is similar to inkjet printer 1, except that it has a control unit 2A and a head unit 3A instead of the control unit 2 and head unit 3 shown in Fig. 1. For example, inkjet printer 1A has a control unit 2A, a head unit 3A, a drive signal generation unit 4, a transport unit 7, and a maintenance unit 8.

[0105] The head unit 3A is similar to the head unit 3 except that it has a detection unit 33. For example, the head unit 3A has a supply circuit 31, a recording head 32, and the detection unit 33 that detects a temperature corresponding to the temperature of the ink in the ejection unit D.

[0106] The detection unit 33 is, for example, a temperature sensor that detects the temperature of the recording head 32. For example, the detection unit 33 detects the temperature of the recording head 32 and outputs temperature information indicating the detected temperature to the control unit 2A. The detection unit 33 is an example of a "temperature detection unit." The temperature of the recording head 32 corresponds to the temperature of the ink in the ejection unit D.

[0107] Here, for example, one temperature sensor may be provided as the detection unit 33 in the recording head 32, or multiple temperature sensors may be provided as the detection unit 33 in the recording head 32. When multiple temperature sensors are provided in the recording head 32, a temperature sensor may be provided for each discharge unit D, or may be provided corresponding to two or more but fewer than M of the M discharge units D. Furthermore, when multiple temperature sensors are provided in the recording head 32, the temperature of the recording head 32 may be, for example, the average value of the detection results of the multiple temperature sensors, or the maximum or minimum value of the detection results of the multiple temperature sensors. In this embodiment, the temperature of the ink in the discharge unit D can be indirectly detected by detecting the temperature of the recording head 32. Note that the detection unit 33 may also directly detect the temperature of the ink in the discharge unit D.

[0108] The control unit 2A adjusts the waveform PD2 etc. defined by the waveform designation signal dCOM based on the temperature detected by the detection unit 33. Then, the drive signal generation unit 4 adjusts the waveform PD2 etc. of the drive signal COM based on the waveform designation signal dCOM indicating the waveform PD2 etc. adjusted based on the temperature detected by the detection unit 33.

[0109] For example, when the temperature detected by the detection unit 33 is a second temperature higher than the first temperature, the control unit 2A adjusts the waveform PD2 so that the potential VL2 at the end of the waveform Pdm2 is lower than when the temperature detected by the detection unit 33 is the first temperature. In other words, the control unit 2A adjusts the potential difference of the drive signal COM between the start and end of the waveform Pdm2 so that it is larger when the temperature detected by the detection unit 33 is the second temperature than when the temperature detected by the detection unit 33 is the first temperature.

[0110] For example, when the temperature of the ink in the ejection section D is high, the viscosity of the ink decreases compared to when the temperature of the ink in the ejection section D is low, and therefore the vibration of the ink in the cavity CV increases. In this embodiment, the amount of change in potential of the waveform Pdm2 can be adjusted according to the temperature of the ink in the ejection section D, so that the vibration of the ink in the cavity CV can be sufficiently damped even when the temperature of the ink in the ejection section D changes. Therefore, in this embodiment, even when the temperature of the ink in the ejection section D changes, the effect of residual vibration generated in the current unit period TP on the ejection of ink droplets in the next unit period TP can be reduced, thereby improving the stability of the ejection of ink droplets.

[0111] The control unit 2A may adjust the period Tco1 of the waveform Pco1 based on the temperature detected by the detection unit 33. For example, when the temperature detected by the detection unit 33 is the second temperature, the control unit 2A may lengthen the period Tco1 of the waveform Pco1 compared to when the temperature detected by the detection unit 33 is the first temperature.

[0112] As described above, in this embodiment, the inkjet printer 1 further includes a detection unit 33 that detects a temperature corresponding to the temperature of the ink inside the ejection unit D. The potential difference of the drive signal COM between the start and end of the waveform Pdm2 is adjusted so that it is greater when the temperature detected by the detection unit 33 is a second temperature higher than the first temperature than when the temperature detected by the detection unit 33 is a first temperature.

[0113] In this way, in this embodiment, the amount of change in potential of the waveform Pdm2 can be adjusted according to the temperature of the ink in the ejection section D, so that it is possible to sufficiently damp the vibration of the ink in the cavity CV even when the temperature of the ink in the ejection section D changes. As a result, in this embodiment, it is possible to improve the stability of ink droplet ejection even when the temperature of the ink in the ejection section D changes.

[0114] [2. Modifications] Each of the above embodiments can be modified in various ways. Specific modified embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within a range that does not contradict each other. In the modified examples exemplified below, elements whose actions and functions are equivalent to those of the embodiments will be designated by the same reference numerals as in the above description, and detailed descriptions of each will be omitted as appropriate.

[0115] [First Modification] In the above-described embodiment, the drive signal COM includes two waveforms PD provided in the unit period TP, but the present invention is not limited to this. For example, the drive signal COM may include three or more waveforms PD provided in the unit period TP.

[0116] Figure 9 is a timing chart illustrating an example of a drive signal COM in the first modified example. Elements similar to those described in Figures 1 to 8 are assigned the same reference numerals, and detailed description thereof will be omitted. Note that Figure 9 assumes that three ink droplets are ejected from a nozzle N during the same unit period TP, and that the three ink droplets combine before landing on the recording paper P, thereby forming one dot on the recording paper P.

[0117] The drive signal COM shown in FIG. 9 is similar to the drive signal COM shown in FIG. 6, except that waveforms PD3 and PCO2 have been added to the drive signal COM shown in FIG. 6. For example, the drive signal COM includes waveforms PD1, PD2, and PD3 that impart pressure fluctuations to the ink in the cavity CV, a waveform PCO1 that connects the waveforms PD1 and PD2, and a waveform PCO2 that connects the waveforms PD1 and PD3. For example, the waveform PD3 precedes the waveform PD1. Note that the waveforms PD1, PD2, and PD3 are examples of "plural drive waveforms," ​​and the waveform PD3 is an example of "a drive waveform other than the last drive waveform and the penultimate drive waveform among the plurality of drive waveforms." Furthermore, the waveform PCO2 is an example of a "second connecting waveform." Hereinafter, the waveforms PD1, PD2, and PD3 will also be referred to as waveforms PD without any particular distinction.

[0118] Like the waveform PD1, the waveform PD3 is a waveform for ejecting ink droplets from the nozzle N. For example, in the same unit period TP, the ink droplets ejected from the nozzle N by the waveform PD3, the ink droplets ejected from the nozzle N by the waveform PD1, and the ink droplets ejected from the nozzle N by the waveform PD2 all combine before landing on the recording paper P.

[0119] For example, the waveform PD3 is a waveform similar to the waveform PD1. Specifically, the waveform PD3 is a waveform in which the potential of the drive signal COM changes from a reference potential V0, passes through a potential VL1 and a potential VH1, and returns to the reference potential V0. For example, the waveform PD3 includes a waveform Pep3 similar to the waveform Pep1, a waveform Peh3 similar to the waveform Peh1, a waveform Pcn3 similar to the waveform Pcn1, a waveform Pch3 similar to the waveform Pch1, and a waveform Pdm3 similar to the waveform Pdm1.

[0120] Therefore, the waveform PD3 can be explained by replacing the waveforms PD1, Pep1, Peh1, Pcn1, Pch1, and Pdm1 in the waveform PD1 described in FIG. 6 with waveforms PD3, Pep3, Peh3, Pcn3, Pch3, and Pdm3. However, the potential change per unit time of the waveform Pcn3 is smaller than the potential change per unit time of the waveform Pcn1. In other words, the potential change per unit time of the waveform Pcn1 is larger than the potential change per unit time of the waveform Pcn3. Also, in the waveform PD3, the period Tsm, which is the sum of the period Tcn3 of the waveform Pcn3 and the period Tch3 of the waveform Pch3, may be the same length as the natural vibration period of the ejection section D. Note that the waveform Pep3 is an example of an "expansion waveform," and the waveform Pcn3 is an example of a "contraction waveform." Moreover, the waveform Pch3 is an example of a "third contraction maintaining waveform," and the waveform Pdm3 is an example of a "third vibration suppressing waveform."

[0121] Furthermore, in this modification, the interval between the waveforms PD3 and PD1 is ensured by the waveform PCO2, so that the residual vibration due to the waveform PD3 can be sufficiently damped by the time the waveform PD1 starts. As a result, in this modification, the effect of the residual vibration due to the waveform PD3 on the ejection of ink droplets by the next waveform PD1 can be reduced, and the ejection of ink droplets by the waveform PD1 can be prevented from becoming unstable.

[0122] For example, the waveform PCO2 is a waveform in which the potential of the drive signal COM is maintained at the potential at the end of the waveform PD3. The potential at the end of the waveform PD3 is the reference potential V0, which is the potential at the end of the waveform Pdm3. In other words, the waveform PCO2 is a waveform in which the potential of the drive signal COM is maintained at the reference potential V0. The period Tco2 of the waveform PCO2 is, for example, 0.8 times or more the natural vibration period of the ejection section D. Preferably, the period Tco2 of the waveform PCO2 is 1 time or more the natural vibration period of the ejection section D. Furthermore, the upper limit of the period Tco2 of the waveform PCO2 is preferably 1.2 times the natural vibration period of the ejection section D.

[0123] As described above, in this modified example, the multiple waveforms PD include three or more waveforms PD. Of the multiple waveforms PD, the waveforms PD3 other than the last waveform PD2 and the penultimate waveform PD1 include a waveform Pch3 in which the potential of the drive signal COM is maintained at the potential VH1 at the end of the waveform Pcn3 to maintain the volume of the cavity CV contracted by the waveform Pcn3, and a waveform Pdm3 in which the potential of the drive signal COM is changed to the reference potential V0 to expand the volume of the cavity CV maintained by the waveform Pch3 and damp residual vibration of the ink in the cavity CV. The drive signal COM further includes a waveform PCO2 that connects one of the multiple waveforms PD other than the last waveform PD2 with the waveform PD immediately preceding that one waveform PD, maintaining the potential of the drive signal COM at the reference potential V0. The period Tco2 of the waveform PCO2 is 0.8 times or more the natural vibration period of the ejection section D.

[0124] This modification also achieves the same effects as the above-described embodiment. Furthermore, in this modification, the period of the waveform PCO2 is 0.8 times or more the natural vibration period of the ejection section D, so that residual vibration due to the waveform PD preceding a waveform PD can be sufficiently attenuated by the time the waveform PD starts. This reduces the effect of residual vibration due to the waveform PD preceding a waveform PD on the ejection of ink droplets by the waveform PD, thereby preventing the ejection of ink droplets by the waveform PD from becoming unstable. In this way, this modification also improves the stability of ink ejection.

[0125] [Second Modification] In the above-described embodiment and modified example, the period Tsm obtained by combining the period Tcn1 of the waveform Pcn1 and the period Tch1 of the waveform Pch1 has the same length as the natural vibration period of the discharge section D. However, the present invention is not limited to this. For example, in the waveform PD1, the period Tsm obtained by combining the period Tcn1 of the waveform Pcn1 and the period Tch1 of the waveform Pch1 may be different from the natural vibration period of the discharge section D. Similarly, in the waveform PD3, the period Tsm obtained by combining the period Tcn3 of the waveform Pcn3 and the period Tch3 of the waveform Pch3 may be different from the natural vibration period of the discharge section D. In this modified example, the same effects as those of the above-described embodiment and modified example can be obtained, except for the effect obtained by the period Tsm being the same length as the natural vibration period of the discharge section D.

[0126] [Third Modification] In the above-described embodiment and modified example, the potential change per unit time of the waveform Prn, which changes the potential of the drive signal COM to the reference potential V0, is smaller than the potential change per unit time of the waveform Pdm2, which corresponds to the vibration damping element. However, the present invention is not limited to this example. For example, the potential change per unit time of the waveform Prn may be the same as or larger than the potential change per unit time of the waveform Pdm2. This modified example also achieves the same effects as the above-described embodiment and modified example, except for the effect achieved by the potential change per unit time of the waveform Prn being smaller than the potential change per unit time of the waveform Pdm2.

[0127] [Fourth Modification] In the above-described embodiment and modified example, the final waveform PD2 includes waveforms Pdm2, Pdh, and Prn, but the present invention is not limited to this. For example, instead of waveforms Pdm2, Pdh, and Prn, waveform PD2 may have a waveform in which the potential of the drive signal COM changes from the potential VH1 at the end of waveform Pch2 to the reference potential V0. This modified example also achieves the same effects as the above-described embodiment and modified example, except for the effect achieved by performing vibration control, which attenuates residual vibrations of the ink in cavity CV, in two stages using waveforms Pdm2 and Prn.

[0128] [Fifth Modification] In the above-described embodiment and modified example, the piezoelectric element PZ is displaced in the -Z direction when the potential of the individual drive signal Vin[m] changes from a low potential to a high potential, but the present invention is not limited to such an embodiment. For example, a piezoelectric element PZ that is displaced in the -Z direction when the potential of the individual drive signal Vin[m] changes from a high potential to a low potential may be used. In this case, for example, the potential of the drive signal COM changes from a low potential to a high potential in a portion corresponding to an expansion element, and changes from a high potential to a low potential in a portion corresponding to a contraction element. In this modified example, the same effects as those of the above-described embodiment and modified example can be obtained.

[0129] [Sixth Modification] In the above-described embodiment and modified example, each head unit 3 has one nozzle row NL, but the present invention is not limited to this. For example, each head unit 3 may have multiple nozzle rows NL. Similarly, each head unit 3A may have multiple nozzle rows NL. In this modified example, the same effects as those of the above-described embodiment and modified example can be obtained.

[0130] [Seventh Modification] In the above-described embodiment and modified example, the inkjet printer 1 has four head units 3, but the present invention is not limited to this. For example, the inkjet printer 1 may have one to three head units 3, or five or more head units 3.

[0131] [Eighth Modification] In the second embodiment described above, the head unit 3A is provided with a detection unit 33 for detecting the temperature of the recording head 32. However, the present invention is not limited to this configuration. For example, the head unit 3A may include a viscosity detection unit for detecting the viscosity of the ink in the nozzles N, instead of or in addition to the detection unit 33. For example, the viscosity detection unit detects the viscosity of the ink in the ejection section D based on a detection signal indicating the potential of the upper electrode Zu of the piezoelectric element PZ. Specifically, the viscosity detection unit generates a residual vibration signal based on the detection signal indicating the potential of the upper electrode Zu of the piezoelectric element PZ. The viscosity detection unit may then detect the viscosity relative to the predetermined viscosity by comparing feature quantities, such as the period and amplitude, of the residual vibration signal with reference feature quantities of the residual vibration signal when the ink has a predetermined viscosity. This modification can also achieve the same effects as the second embodiment described above.

[0132] [Ninth Variation] In the above-described embodiment and modified example, the inkjet printer 1 is a serial printer, but the present invention is not limited to this. For example, the inkjet printer 1 may be a so-called line printer in which the head unit 3 has multiple nozzles N that extend wider than the width of the recording paper P. Similarly, the inkjet printer 1A may be a line printer. This modified example also provides the same effects as the above-described embodiment and modified example.

[0133] [Tenth Modification] In the above-described embodiment and modified example, the case where there is one drive signal COM is illustrated, but the present invention is not limited to such an embodiment. For example, the drive signal COM may include, in addition to the drive signal COM shown in FIG. 6, a drive signal having a waveform different from the waveforms PD1 and PD2 of the drive signal COM. In this modified example, the same effects as those of the above-described embodiment and modified example can be obtained. [Explanation of symbols]

[0134] 1, 1A... inkjet printer, 2, 2A... control unit, 3, 3A... head unit, 4... drive signal generation unit, 7... transport unit, 8... maintenance unit, 31... supply circuit, 32... recording head, D... ejection section, N... nozzle

Claims

1. a plurality of ejection units each including a nozzle for ejecting droplets, a pressure chamber communicating with the nozzle, and a drive element; a signal generating unit that generates, as a drive signal for the drive element, a signal for ejecting a plurality of droplets from the nozzle so that the droplets coalesce before landing on a medium; Equipped with The drive signal is a plurality of drive waveforms that impart pressure fluctuations to the liquid in the pressure chamber; connecting the last drive waveform and the second-to-last drive waveform among the plurality of drive waveforms; a first connection waveform in which the potential of the drive signal is maintained at a reference potential; Including, Each of the plurality of drive waveforms is an expansion waveform in which the potential of the drive signal changes from the reference potential so as to expand the volume of the pressure chamber; a contraction waveform in which the potential of the drive signal is changed so as to contract the volume of the pressure chamber expanded by the expansion waveform and eject a droplet from the nozzle; and Including, the pressure fluctuation of the liquid in the pressure chamber caused by the contraction waveform is greater in the last drive waveform than in the second-to-last drive waveform; The period of the first connection waveform is 0.8 times or more the natural vibration period of the ejection portion, The potential of the drive signal at the end of the contraction waveform is the last drive waveform and the second-to-last drive waveform are the same, The amount of potential change per unit time of the contraction waveform is the final drive waveform is greater than the second-to-last drive waveform; A liquid ejection device characterized by:

2. The second to last drive waveform is: a first contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a first damping waveform in which the potential of the drive signal changes to the reference potential so as to expand the volume of the pressure chamber maintained by the first contraction maintaining waveform and damp residual vibration of the liquid in the pressure chamber; further comprising In the second-to-last driving waveform, a period obtained by combining the period of the contraction waveform and the period of the first contraction maintaining waveform has the same length as the natural vibration period of the ejection section. The liquid ejection device according to claim 1 .

3. a period of the first connection waveform is equal to or greater than one time the natural vibration period of the ejection portion; 3. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

4. a period of the first connection waveform is 1.2 times or less the natural vibration period of the ejection portion; 4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

5. The final drive waveform is: a second contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a second damping waveform in which the potential of the drive signal is changed so as to expand the volume of the pressure chamber maintained by the second contraction maintaining waveform and damp the residual vibration of the liquid in the pressure chamber; further comprising The reference potential is a potential between a potential of the drive signal at the start of the second damping waveform and a potential of the drive signal at the end of the second damping waveform; 5. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

6. a temperature detection unit that detects a temperature corresponding to the temperature of the liquid in the discharge unit; a potential difference of the drive signal at the start and end of the second damping waveform is adjusted to be larger when the temperature detected by the temperature detection unit is a second temperature higher than the first temperature than when the temperature detected by the temperature detection unit is a first temperature; 6. The liquid ejection device according to claim 5.

7. The final drive waveform is: an expansion maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the second damping waveform so as to maintain the volume of the pressure chamber expanded by the second damping waveform; a return waveform in which the potential of the drive signal changes from the potential at the end of the expansion maintaining waveform to the reference potential, and the amount of potential change per unit time is smaller than the amount of potential change per unit time of the second damping waveform; further comprising:

7. The liquid ejection device according to claim 5, wherein the liquid ejection device is a liquid ejection device.

8. the plurality of drive waveforms are three or more drive waveforms, Among the plurality of drive waveforms, drive waveforms other than the last drive waveform and the second-to-last drive waveform are a third contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a third damping waveform in which the potential of the drive signal changes to the reference potential so as to expand the volume of the pressure chamber maintained by the third contraction maintaining waveform and damp residual vibration of the liquid in the pressure chamber; further comprising The drive signal is further including a second connecting waveform that connects a drive waveform other than the last drive waveform among the plurality of drive waveforms with a drive waveform preceding the one drive waveform, and maintains a potential of the drive signal at the reference potential; The period of the second connection waveform is 0.8 times or more the natural vibration period of the ejection portion. The liquid ejection device according to any one of claims 1 to 7.

9. A nozzle for ejecting droplets, a pressure chamber communicating with the nozzle, and a plurality of ejection units including a drive element; a signal generating unit that generates, as a drive signal for the drive element, a signal for ejecting a plurality of droplets from the nozzle so that the droplets coalesce before landing on a medium; Equipped with The drive signal is a plurality of drive waveforms that impart pressure fluctuations to the liquid in the pressure chamber; connecting the last drive waveform and the second-to-last drive waveform among the plurality of drive waveforms; a first connection waveform in which the potential of the drive signal is maintained at a reference potential; Including, Each of the plurality of drive waveforms is an expansion waveform in which the potential of the drive signal changes from the reference potential so as to expand the volume of the pressure chamber; a contraction waveform in which the potential of the drive signal is changed so as to contract the volume of the pressure chamber expanded by the expansion waveform and eject a droplet from the nozzle; and Including, the pressure fluctuation of the liquid in the pressure chamber caused by the contraction waveform is greater in the last drive waveform than in the second-to-last drive waveform; The period of the first connection waveform is 0.8 times or more the natural vibration period of the ejection portion, The second to last drive waveform is: a first contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a first damping waveform in which the potential of the drive signal changes to the reference potential so as to expand the volume of the pressure chamber maintained by the first contraction maintaining waveform and damp residual vibration of the liquid in the pressure chamber; further comprising In the second-to-last driving waveform, a period obtained by combining the period of the contraction waveform and the period of the first contraction maintaining waveform has the same length as the natural vibration period of the ejection section. A liquid ejection device characterized by:

10. The period of the first connection waveform is equal to or greater than one time the natural vibration period of the ejection portion. The liquid ejection device according to claim 9 .

11. The period of the first connection waveform is 1.2 times or less the natural vibration period of the ejection portion.

11. The liquid ejection device according to claim 9 or 10.

12. The final drive waveform: a second contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a second damping waveform in which the potential of the drive signal is changed so as to expand the volume of the pressure chamber maintained by the second contraction maintaining waveform and damp the residual vibration of the liquid in the pressure chamber; further comprising The reference potential is a potential between a potential of the drive signal at the start of the second damping waveform and a potential of the drive signal at the end of the second damping waveform; 12. The liquid ejection device according to claim 9, wherein the ejection head is a nozzle.

13. Further comprising a temperature detection unit for detecting a temperature corresponding to the temperature of the liquid in the discharge unit, a potential difference of the drive signal at the start and end of the second damping waveform is adjusted to be larger when the temperature detected by the temperature detection unit is a second temperature higher than the first temperature than when the temperature detected by the temperature detection unit is a first temperature; The liquid ejection device according to claim 12 .

14. The final drive waveform is an expansion maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the second damping waveform so as to maintain the volume of the pressure chamber expanded by the second damping waveform; a return waveform in which the potential of the drive signal changes from the potential at the end of the expansion maintaining waveform to the reference potential, and the amount of potential change per unit time is smaller than the amount of potential change per unit time of the second damping waveform; further comprising:

14. The liquid ejection device according to claim 12 or 13.

15. The plurality of drive waveforms are three or more drive waveforms, Among the plurality of drive waveforms, drive waveforms other than the last drive waveform and the second-to-last drive waveform are a third contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a third damping waveform in which the potential of the drive signal changes to the reference potential so as to expand the volume of the pressure chamber maintained by the third contraction maintaining waveform and damp residual vibration of the liquid in the pressure chamber; further comprising The drive signal is further including a second connecting waveform that connects a drive waveform other than the last drive waveform among the plurality of drive waveforms with a drive waveform preceding the one drive waveform, and maintains a potential of the drive signal at the reference potential; The period of the second connection waveform is 0.8 times or more the natural vibration period of the ejection portion.

15. The liquid ejection device according to claim 9, wherein the ejection head is a nozzle.

16. A method for manufacturing a liquid ejection head, comprising: a nozzle for ejecting droplets; a pressure chamber communicating with the nozzle; and a plurality of ejection units including a drive element; a signal generating unit that generates, as a drive signal for the drive element, a signal for ejecting a plurality of droplets from the nozzle so that the droplets coalesce before landing on a medium; Equipped with The drive signal is a plurality of drive waveforms that impart pressure fluctuations to the liquid in the pressure chamber; connecting the last drive waveform and the second-to-last drive waveform among the plurality of drive waveforms; a first connection waveform in which the potential of the drive signal is maintained at a reference potential; Including, Each of the plurality of drive waveforms is an expansion waveform in which the potential of the drive signal changes from the reference potential so as to expand the volume of the pressure chamber; a contraction waveform in which the potential of the drive signal is changed so as to contract the volume of the pressure chamber expanded by the expansion waveform and eject a droplet from the nozzle; and Including, the pressure fluctuation of the liquid in the pressure chamber caused by the contraction waveform is greater in the last drive waveform than in the second-to-last drive waveform; The period of the first connection waveform is 0.8 times or more the natural vibration period of the ejection portion, The final drive waveform is: a second contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a second damping waveform in which the potential of the drive signal is changed so as to expand the volume of the pressure chamber maintained by the second contraction maintaining waveform and damp the residual vibration of the liquid in the pressure chamber; further comprising The reference potential is a potential between a potential of the drive signal at the start of the second damping waveform and a potential of the drive signal at the end of the second damping waveform; A liquid ejection device characterized by:

17. Further comprising a temperature detection unit for detecting a temperature corresponding to the temperature of the liquid in the discharge unit, a potential difference of the drive signal at the start and end of the second damping waveform is adjusted to be larger when the temperature detected by the temperature detection unit is a second temperature higher than the first temperature than when the temperature detected by the temperature detection unit is a first temperature; 17. The liquid ejection device according to claim 16.

18. The final drive waveform: an expansion maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the second damping waveform so as to maintain the volume of the pressure chamber expanded by the second damping waveform; a return waveform in which the potential of the drive signal changes from the potential at the end of the expansion maintaining waveform to the reference potential, and the amount of potential change per unit time is smaller than the amount of potential change per unit time of the second damping waveform; further comprising:

18. The liquid ejection device according to claim 16 or 17.

19. The period of the first connection waveform is equal to or greater than one time the natural vibration period of the ejection portion.

19. The liquid ejection device according to claim 16, wherein the liquid ejection device is a liquid ejection device.

20. The period of the first connection waveform is 1.2 times or less the natural vibration period of the ejection portion.

20. The liquid ejection device according to claim 16, wherein the ejection head is a nozzle.

21. A method for controlling a liquid ejection device having a plurality of ejection units including nozzles that eject droplets, pressure chambers that communicate with the nozzles, and drive elements, comprising: generating a signal for discharging a plurality of droplets from the nozzle so that the droplets coalesce before landing on a medium, as a drive signal for the drive element; The drive signal is a plurality of drive waveforms that impart pressure fluctuations to the liquid in the pressure chamber; a first connection waveform that connects the last drive waveform and the second-to-last drive waveform of the plurality of drive waveforms, and maintains the potential of the drive signal at a reference potential; Including, Each of the plurality of drive waveforms is an expansion waveform in which the potential of the drive signal changes from the reference potential so as to expand the volume of the pressure chamber; a contraction waveform in which the potential of the drive signal is changed so as to contract the volume of the pressure chamber expanded by the expansion waveform and eject a droplet from the nozzle; and Including, the pressure fluctuation of the liquid in the pressure chamber caused by the contraction waveform is greater in the last drive waveform than in the second-to-last drive waveform; The period of the first connection waveform is 0.8 times or more the natural vibration period of the ejection portion, The potential of the drive signal at the end of the contraction waveform is the last drive waveform and the second-to-last drive waveform are the same, The amount of potential change per unit time of the contraction waveform is the final drive waveform is greater than the second-to-last drive waveform; A method for controlling a liquid ejection device.

22. A method for controlling a liquid ejection device having a nozzle for ejecting droplets, a pressure chamber communicating with the nozzle, and a plurality of ejection units including drive elements, comprising: generating a signal for discharging a plurality of droplets from the nozzle so that the droplets coalesce before landing on a medium, as a drive signal for the drive element; The drive signal is a plurality of drive waveforms that impart pressure fluctuations to the liquid in the pressure chamber; a first connection waveform that connects the last drive waveform and the second-to-last drive waveform of the plurality of drive waveforms, and maintains the potential of the drive signal at a reference potential; Including, Each of the plurality of drive waveforms is an expansion waveform in which the potential of the drive signal changes from the reference potential so as to expand the volume of the pressure chamber; a contraction waveform in which the potential of the drive signal is changed so as to contract the volume of the pressure chamber expanded by the expansion waveform and eject a droplet from the nozzle; and Including, the pressure fluctuation of the liquid in the pressure chamber caused by the contraction waveform is greater in the last drive waveform than in the second-to-last drive waveform; The period of the first connection waveform is 0.8 times or more the natural vibration period of the ejection portion, The second to last drive waveform is: a first contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a first damping waveform in which the potential of the drive signal changes to the reference potential so as to expand the volume of the pressure chamber maintained by the first contraction maintaining waveform and damp residual vibration of the liquid in the pressure chamber; further comprising In the second-to-last driving waveform, a period obtained by combining the period of the contraction waveform and the period of the first contraction maintaining waveform has the same length as the natural vibration period of the ejection section. A method for controlling a liquid ejection device.

23. A method for controlling a liquid ejection device having a nozzle for ejecting droplets, a pressure chamber communicating with the nozzle, and a plurality of ejection units including drive elements, comprising: generating a signal for discharging a plurality of droplets from the nozzle so that the droplets coalesce before landing on a medium, as a drive signal for the drive element; The drive signal is a plurality of drive waveforms that impart pressure fluctuations to the liquid in the pressure chamber; a first connection waveform that connects the last drive waveform and the second-to-last drive waveform of the plurality of drive waveforms, and maintains the potential of the drive signal at a reference potential; Including, Each of the plurality of drive waveforms is an expansion waveform in which the potential of the drive signal changes from the reference potential so as to expand the volume of the pressure chamber; a contraction waveform in which the potential of the drive signal is changed so as to contract the volume of the pressure chamber expanded by the expansion waveform and eject a droplet from the nozzle; and Including, the pressure fluctuation of the liquid in the pressure chamber caused by the contraction waveform is greater in the last drive waveform than in the second-to-last drive waveform; The period of the first connection waveform is 0.8 times or more the natural vibration period of the ejection portion, The final drive waveform is: a second contraction maintaining waveform in which the potential of the drive signal is maintained at the potential at the end of the contraction waveform so as to maintain the volume of the pressure chamber contracted by the contraction waveform; a second damping waveform in which the potential of the drive signal is changed so as to expand the volume of the pressure chamber maintained by the second contraction maintaining waveform and damp the residual vibration of the liquid in the pressure chamber; further comprising The reference potential is a potential between a potential of the drive signal at the start of the second damping waveform and a potential of the drive signal at the end of the second damping waveform; A method for controlling a liquid ejection device.

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