Liquid discharge apparatus and method of driving liquid discharge apparatus

Abstract

To supply an appropriate drive signal to a plurality of piezoelectric elements.SOLUTION: A liquid discharge apparatus includes a liquid discharge head provided with a plurality of piezoelectric elements that apply pressure to liquid in a pressure chamber by being driven, an acquisition unit that acquires a simultaneous driving number that is the number of piezoelectric elements to be simultaneously driven among the plurality of piezoelectric elements, a determination unit that determines a driving signal for driving the piezoelectric elements of the simultaneous driving number by adjusting a timing of changing a potential of the driving signal based on the simultaneous driving number, and a driving signal output unit that outputs the driving signal determined by the determination unit.SELECTED DRAWING: Figure 20

Description

[Technical Field]

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

[0002] A liquid ejection device that ejects a liquid such as ink onto a medium to form an image on the medium has been known. For example, Patent Document 1 discloses that a drive signal whose potential varies is supplied to one or more piezoelectric elements among a plurality of piezoelectric elements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-139519 Summary of the Invention [Problem to be solved by the invention]

[0004] After the potential of the drive signal supplied to the piezoelectric element fluctuates, it takes a certain period of time for the current to stabilize. By fluctuating the potential of the drive signal supplied to the piezoelectric element again after the current has stabilized, the characteristics of the piezoelectric element can be fully utilized. However, the period during which the current stabilizes after the potential of the drive signal fluctuates can vary, making it unclear when the current stabilizes. Therefore, with the above-mentioned conventional technology, there is a problem in that it is not possible to supply appropriate drive signals to multiple piezoelectric elements because it is unclear when the current stabilizes. [Means for solving the problem]

[0005] A liquid ejection device according to a preferred aspect of the present disclosure includes a liquid ejection head provided with a plurality of piezoelectric elements that, when driven, apply pressure to liquid in a pressure chamber; an acquisition unit that acquires a simultaneous drive number, which is the number of piezoelectric elements that are driven simultaneously among the plurality of piezoelectric elements; a determination unit that determines the drive signal by adjusting the timing of changing the potential of the drive signal for driving the simultaneously driven number of piezoelectric elements based on the simultaneously driven number; and a drive signal output unit that outputs the drive signal determined by the determination unit.

[0006] A preferred aspect of the present disclosure provides a method for driving a liquid ejection device having a liquid ejection head provided with a plurality of piezoelectric elements that, when driven, apply pressure to liquid in a pressure chamber, a drive signal output unit that outputs a drive signal for driving one or more of the plurality of piezoelectric elements, and a control unit that controls the liquid ejection head and the drive signal output unit, wherein the control unit obtains a simultaneous drive number, which is the number of piezoelectric elements that are driven simultaneously among the plurality of piezoelectric elements, and outputs the drive signal, the potential of which has been changed at a timing adjusted based on the simultaneous drive number, to the drive signal output unit. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a functional block diagram showing an example of the configuration of a liquid ejection device 100. [Figure 2] 1 is a schematic diagram illustrating a liquid ejection device 100. FIG. [Figure 3] FIG. 2 is an exploded perspective view of the liquid ejection head 1. [Figure 4] 4 is a cross-sectional view of line aa shown in FIG. 3. [Figure 5] FIG. 2 is an enlarged cross-sectional view of the vicinity of the piezoelectric element PZ. [Figure 6] FIG. 2 is a block diagram of a DA conversion circuit 3 and a drive signal generation circuit 2. [Figure 7] FIG. 2 is a block diagram showing an example of the configuration of a switching circuit 10. [Figure 8] FIG. 3 is a diagram for explaining a drive signal Com. [Figure 9]10 is a diagram showing a change in voltage when a drive signal Com is supplied to a piezoelectric element PZ. [Figure 10] FIG. 10 is a diagram showing the measurement results of the current response when the ejection waveform PD is supplied to the piezoelectric element PZ. [Figure 11] 10 is a diagram showing the measurement results of the charge amount response when an ejection waveform PD is supplied to a piezoelectric element PZ. FIG. [Figure 12] FIG. 10 is a diagram showing a determination period for each integer of the number of simultaneously driven pulses NPZ from 1 to 10. [Figure 13] FIG. 10 is a diagram showing the amount of polarization when the number of simultaneously driven NPZ is an integer from 1 to 10. [Figure 14] FIG. 10 is a diagram showing current values ​​calculated by equations (1) and (2). [Figure 15] FIG. 15 is a diagram showing the charge amount based on the current in FIG. 14. [Figure 16] FIG. 10 is a diagram showing the length of a push reversal period based on the current calculated by equations (1) and (2). [Figure 17] FIG. 10 is a diagram showing the polarization amount based on the current calculated by equations (1) and (2). [Figure 18] FIG. 4 is a flowchart showing a series of steps in a printing process. [Figure 19] FIG. 10 is a flowchart showing a series of steps in a drive signal adjustment process. [Figure 20] FIG. 10 is a diagram for explaining a specific example of the process of step SC112. [Figure 21] FIG. 10 is a diagram for explaining a specific example of the process of step SC112 in the second embodiment. [Figure 22] FIG. 10 is a diagram showing a hysteresis curve showing the relationship between the voltage and polarization of a piezoelectric body Zm. 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] A. First embodiment A1. Overview of liquid ejection device The configuration of the liquid ejection device 100 will be described with reference to Figures 1 and 2. Figure 1 is a functional block diagram showing an example of the configuration of the liquid ejection device 100 according to the first embodiment. Figure 2 is a schematic diagram illustrating the liquid ejection device 100. The liquid ejection device 100 is an inkjet printing device that ejects ink, which is an example of a liquid, onto a medium PP. The medium PP is typically printing paper, but any printing target such as a resin film or fabric can also be used as the medium PP.

[0010] 2, the liquid ejection device 100 includes a liquid container 93 that stores ink. The liquid container 93 may be, for example, a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, or an ink tank that can be refilled with ink. The liquid container 93 stores a plurality of types of ink with different colors.

[0011] As illustrated in FIG. 1, the liquid ejection device 100 includes a drive signal generation circuit 2, a DA conversion circuit 3, a liquid ejection head 1, an oscillation circuit 4, a control unit 7, a storage unit 5, a movement mechanism 91, and a transport mechanism 92. As illustrated in FIGS. 1 and 2, the liquid ejection device 100 has one liquid ejection head 1, but may have two or more liquid ejection heads 1. DAC is an abbreviation for Digital to Analog Converter. The drive signal generation circuit 2 is an example of a "drive signal output unit."

[0012] The oscillator circuit 4 generates a clock signal CLK that is used to time a plurality of circuits included in the liquid ejection device 100. The oscillator circuit 4 includes a quartz oscillator. The oscillator circuit 4 is, for example, a VCO that oscillates the clock signal CLK at a frequency corresponding to a control voltage. VCO is an abbreviation for Voltage Controlled Oscillator. The clock signal CLK is transmitted to, for example, the control unit 7, the DA conversion circuit 3, and the switching circuit 10. In the following, the reciprocal of the frequency of the clock signal CLK, i.e., the period in which the clock signal CLK is supplied, is referred to as the adjustment period T CLK Here, the clock signal CLK is sometimes described as a clock signal having a frequency that is an integer multiple of the input frequency, and a frequency divider circuit that generates a frequency that is an integer fraction of the input frequency. For example, the oscillator circuit 4 may include one or both of a multiplier circuit that generates a frequency that is an integer multiple of the input frequency, and a frequency divider circuit that generates a frequency that is an integer fraction of the input frequency. As an example, the oscillator circuit 4 may output a clock signal generated by a VCO to the controller 7, and output a clock signal whose frequency has been changed by one or both of the multiplier circuit and the frequency divider circuit to the DA converter circuit 3 and the switching circuit 10. The clock signal CLK is an example of an "adjustment signal." The oscillator circuit 4 is an example of an "adjustment signal output unit."

[0013] The control unit 7 is a processing circuit such as a CPU or FPGA. Here, CPU is an abbreviation for Central Processing Unit, and FPGA is an abbreviation for Field Programmable Gate Array. The control unit 7 controls each element of the liquid ejection device 100.

[0014] The storage unit 5 includes a volatile memory such as RAM, and a non-volatile memory such as ROM, EEPROM, or PROM. The storage unit 5 stores various information such as waveform information CI for generating the waveform designation signal dCom, print data Img supplied from a host computer such as a personal computer or digital camera, and a control program for the liquid ejection device 100. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. PROM is an abbreviation for Programmable ROM.

[0015] The movement mechanism 91 transports the medium PP in the Y1 direction along the Y axis under the control of the control unit 7. Hereinafter, the Y1 direction and the Y2 direction opposite to the Y1 direction will be collectively referred to as the Y-axis direction. Hereinafter, the X1 direction along the X axis intersecting the Y axis and the X2 direction opposite to the X1 direction will be collectively referred to as the X-axis direction. Hereinafter, the Z1 direction along the Z axis intersecting the X and Y axes and the Z2 direction opposite to the Z1 direction will be collectively referred to as the Z-axis direction. In this embodiment, as an example, a case will be described in which the X axis, Y axis, and Z axis are orthogonal to each other. However, the present disclosure is not limited to this example. It is sufficient that the X axis, Y axis, and Z axis intersect each other.

[0016] The transport mechanism 92 reciprocates the liquid ejection head 1 in the X1 direction and the X2 direction under the control of the control unit 7. As shown in Fig. 2, the transport mechanism 92 includes a storage case 921 that stores the liquid ejection head 1, and an endless belt 922 to which the storage case 921 is fixed. Note that the liquid container 93 may be stored in the storage case 921 together with the liquid ejection head 1.

[0017] The liquid ejection head 1 includes a recording head HD having M piezoelectric elements PZ for ejecting ink, and a switching circuit 10. In this embodiment, M is an integer of 2 or greater.

[0018] The control unit 7 controls the ejection operation of the liquid ejection head 1. Specifically, the control unit 7 generates an image signal SI for controlling the liquid ejection head 1, a waveform designation signal dCom input to the DA conversion circuit 3, a signal for controlling the transport mechanism 92, and a signal for controlling the movement mechanism 91.

[0019] Here, the waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com. The control unit 7 generates the waveform designation signal dCom based on waveform information CI. Details of the waveform information CI will be described later in Figure 8. The drive signal Com is an analog signal for driving the piezoelectric element PZ. The DA conversion circuit 3 converts the waveform designation signal dCom into an analog basic drive signal aA based on the clock signal CLK and the waveform designation signal dCom. This basic drive signal aA is a target signal for the drive signal Com before it is amplified. The drive signal generation circuit 2 generates the drive signal Com based on the basic drive signal aA. The configurations of the DA conversion circuit 3 and the drive signal generation circuit 2 will be described later in Figure 6.

[0020] The image signal SI is a digital signal for specifying the type of operation of the piezoelectric element PZ. Specifically, the image signal SI specifies whether or not to supply the drive signal Com to the piezoelectric element PZ, thereby specifying the type of operation of the piezoelectric element PZ.

[0021] The control unit 7 first stores the print data Img supplied from the host computer in the storage unit 5. Next, the control unit 7 outputs a clock signal CLK and generates various control signals, such as an image signal SI, a waveform designation signal dCom, a signal for controlling the transport mechanism 92, and a signal for controlling the movement mechanism 91, based on various data, such as the print data Img, stored in the storage unit 5. The control unit 7 then controls the transport mechanism 92 and the movement mechanism 91 to change the relative position of the medium PP with respect to the liquid ejection head 1, based on the various control signals and the various data stored in the storage unit 5, while controlling the liquid ejection head 1 to drive the piezoelectric element PZ. In this way, the control unit 7 adjusts whether or not ink is ejected, the amount of ink ejected, the timing of ink ejection, and the like, and controls the execution of a printing process to form an image corresponding to the print data Img on the medium PP.

[0022] The control unit 7 reads out a control program stored in the storage unit 5 and executes the read out control program, thereby functioning as an image signal output unit 71, an acquisition unit 73, and a waveform designation signal output unit 75. Furthermore, the control unit 7 functioning as the waveform designation signal output unit 75 and the DA conversion circuit 3 function as a determination unit (hereinafter also referred to as an adjustment unit) 70. The function of each unit will be described later.

[0023] A2. Configuration of liquid ejection head 1 The liquid ejection head 1 will now be described. In the following, to distinguish between the M piezoelectric elements PZ provided in the liquid ejection head 1, they may be referred to in order as 1st stage, 2nd stage, ..., Mth stage. Also, the mth stage piezoelectric element PZ may be referred to as piezoelectric element PZ[m]. In the following description, the variable m is an integer that is equal to or greater than 1 and equal to or less than M. Also, when a component, signal, etc. of the liquid ejection device 100 corresponds to the number m of stages of the piezoelectric elements PZ[m], the subscript [m] indicating that the component, signal, etc. corresponds to the number m of stages may be added to the symbol representing the component, signal, etc.

[0024] The switching circuit 10 switches whether or not the drive signal Com output from the drive signal generating circuit 2 is supplied to each piezoelectric element PZ.

[0025] The liquid ejection head 1 will be described with reference to FIGS.

[0026] Fig. 3 is an exploded perspective view of the liquid ejection head 1. Fig. 4 shows a cross-sectional view taken along line aa in Fig. 3. The aa cross section is parallel to the XZ plane and passes through an inlet 424, which will be described later. However, the switching circuit 10 is not shown in Figs. 3 and 4.

[0027] 3 and 4, the liquid ejection head 1 includes a flow path substrate 32 that is elongated along the Y axis and has a substantially rectangular shape. A pressure chamber substrate 34, a vibration plate 36, M piezoelectric elements PZ, a housing 42, and a sealing member 44 are disposed on the upper surface of the flow path substrate 32. A nozzle plate 46 and a vibration absorber 48 are disposed on the lower surface of the flow path substrate 32. The elements of the liquid ejection head 1 are generally plate-like members that are elongated along the Y axis, similar to the flow path substrate 32, and are joined to each other using, for example, an adhesive. Although not shown, the switching circuit 10 is provided, for example, on the Z1-direction surface of the sealing member 44.

[0028] As illustrated in FIG. 3, the nozzle plate 46 is a plate-like member on which M nozzles N are formed and arranged along the Y axis. The M nozzles N constitute a nozzle row Ln. Each nozzle N is a through-hole through which ink passes. The flow path substrate 32, the pressure chamber substrate 34, and the nozzle plate 46 are formed, for example, by processing a silicon single crystal substrate using semiconductor manufacturing techniques such as etching. However, the materials and manufacturing methods for each element of the liquid ejection head 1 are arbitrary. The direction of the Y axis can also be said to be the direction of the nozzle row Ln.

[0029] The flow path substrate 32 is a plate-like member for forming ink flow paths. As illustrated in FIGS. 3 and 4, the flow path substrate 32 has openings 322, supply flow paths 324, and communication flow paths 326 formed therein. The openings 322 are through-holes that are continuous along the Y axis across M nozzles N in a plan view in the Z axis direction. The supply flow paths 324 and communication flow paths 326 are through-holes that are individually formed for each nozzle N. Furthermore, as illustrated in FIG. 4, a relay flow path 328 that connects the M supply flow paths 324 is formed on the surface of the flow path substrate 32 in the Z2 direction. The relay flow path 328 is a flow path that connects the openings 322 and the M supply flow paths 324.

[0030] The housing 42 is a structure manufactured by, for example, injection molding of a resin material, and is fixed to the upper surface of the flow path substrate 32. As illustrated in FIG. 4, a storage portion 422 and an inlet 424 are formed in the housing 42. The storage portion 422 is a recess whose outer shape corresponds to the opening 322 of the flow path substrate 32. The inlet 424 is a through-hole that communicates with the storage portion 422. As can be seen from FIG. 3, the space that interconnects the opening 322 of the flow path substrate 32 and the storage portion 422 of the housing 42 functions as a liquid storage chamber R. Ink that is supplied from the liquid container 93 and passes through the inlet 424 is stored in the liquid storage chamber R.

[0031] 3 and 4, the sealing member 44 is a structure that protects the M piezoelectric elements PZ from the outside air and reinforces the mechanical strength of the pressure chamber substrate 34 and the vibration plate 36. The sealing member 44 is fixed to the surface of the vibration plate 36 with, for example, an adhesive. The sealing member 44 has a recess on the surface facing the vibration plate 36. A sealed space 442 is formed by fixing the sealing member 44 to the surface of the vibration plate 36. The sealed space 442 contains the M piezoelectric elements PZ.

[0032] The vibration absorber 48 absorbs pressure fluctuations within the liquid storage chamber R. The vibration absorber 48 includes, for example, a flexible sheet member that is capable of elastic deformation. Specifically, the vibration absorber 48 is installed on the downward surface of the flow path substrate 32 so as to close the opening 322, the relay flow path 328, and the plurality of supply flow paths 324 of the flow path substrate 32 and form the bottom surface of the liquid storage chamber R.

[0033] 3 and 4, the pressure chamber substrate 34 is a plate-like member in which M pressure chambers CV corresponding to the M nozzles N are formed. The M pressure chambers CV are arranged at intervals from one another along the Y axis. Each pressure chamber CV is an opening that is long along the X axis. The X1-direction end of each pressure chamber CV overlaps with one supply flow path 324 in a plan view, and the X2-direction end of each pressure chamber CV overlaps with one communication flow path 326 of the flow path substrate 32 in a plan view.

[0034] A diaphragm 36 is provided on the surface of the pressure chamber substrate 34 opposite to the surface facing the flow path substrate 32. The diaphragm 36 is an elastically deformable plate-like member. As shown in FIG. 4, the diaphragm 36 of the first embodiment is configured by laminating an elastic film 361 and an insulating film 362. The insulating film 362 is located on the opposite side of the pressure chamber substrate 34 from the elastic film 361. The elastic film 361 is made of, for example, silicon oxide. The insulating film 362 is made of, for example, zirconium oxide.

[0035] As can be seen from Figures 3 and 4, the flow path substrate 32 and the vibration plate 36 face each other at a distance inside each pressure chamber CV. The pressure chamber CV is located between the flow path substrate 32 and the vibration plate 36 and is a space for applying pressure to the ink filled in the pressure chamber CV. The vibration plate 36 forms part of the wall surface of the pressure chamber CV. The ink stored in the liquid storage chamber R branches from the relay flow path 328 to each supply flow path 324 and is supplied to and filled in parallel into the M pressure chambers CV. In other words, the liquid storage chamber R functions as a common liquid chamber for supplying ink to the M pressure chambers CV.

[0036] As illustrated in FIGS. 3 and 4, M piezoelectric elements PZ corresponding to the M nozzles N are provided on the surface of the vibration plate 36 facing away from the pressure chamber substrate 34. Each piezoelectric element PZ is an actuator that deforms when a drive signal Com is supplied, and is formed in an elongated shape along the X axis. The M piezoelectric elements PZ are arranged along the Y axis so as to correspond to the M pressure chambers CV. When the vibration plate 36 vibrates in conjunction with the deformation of the piezoelectric elements PZ, the pressure inside the pressure chambers CV fluctuates, causing ink filled in the pressure chambers CV to pass through the communication flow path 326 and the nozzles N and be ejected. In other words, the piezoelectric elements PZ are drive elements that vibrate the vibration plate 36, thereby ejecting ink from the pressure chambers CV through the nozzles N.

[0037] 5 is an enlarged cross-sectional view of the vicinity of the piezoelectric element PZ, but in order to avoid complicating the drawing, the sealing member 44 is omitted from the drawing.

[0038] 5, the piezoelectric element PZ is a laminated body in which a piezoelectric body Zm is interposed between an upper electrode Zu to which a predetermined reference potential Vbs is supplied and a lower electrode Zd to which a drive signal Com is supplied. When viewed from the Z1 direction, for example, the piezoelectric element PZ is a portion where the lower electrode Zd, the upper electrode Zu, and the piezoelectric body Zm overlap. A pressure chamber CV is provided in the Z2 direction of the piezoelectric element PZ. While the first embodiment illustrates a configuration in which the reference potential Vbs is supplied to the upper electrode Zu and the drive signal Com is supplied to the lower electrode Zd, it is also possible to provide a configuration in which the drive signal Com is supplied to the upper electrode Zu and the reference potential Vbs is supplied to the lower electrode Zd.

[0039] When a voltage is applied between the upper electrode Zu and the lower electrode Zd, the piezoelectric element PZ is displaced in the Z1 direction or the Z2 direction in accordance with the applied voltage, and as a result of this displacement, the piezoelectric element PZ vibrates.

[0040] A3. Configuration of DA conversion circuit 3 and drive signal generation circuit 2 6 is a block diagram of the DA conversion circuit 3 and the drive signal generation circuit 2. The DA conversion circuit 3 includes a DAC interface 21 and a DAC section 22. The drive signal generation circuit 2 has an amplification control signal generation circuit 20 and a drive signal output circuit 25. The amplification control signal generation circuit 20 generates amplification control signals Hgd and Lgd based on the basic drive signal aA. The amplification control signal generation circuit 20 includes a modulation section 23 and a gate driver 24. In this embodiment, the DA conversion circuit 3 and the drive signal generation circuit 2 may be separate entities or may be an integrated circuit.

[0041] The DAC interface 21 receives a waveform specification signal dCom supplied from the control unit 6 and a clock signal CLK output from the control unit 6. Based on the clock signal CLK and the waveform specification signal dCom, the DAC interface 21 generates, for example, 10-bit drive data dA that defines the waveform of the drive signal Com. For example, the DAC interface 21 is realized by a DDS. DDS is an abbreviation for Direct Digital Synthesizer. Specifically, the DAC interface 21 has an accumulator that accumulates the clock signal CLK, and an output circuit that includes a look-up table that stores the waveform specification signal dCom. The waveform specification signal dCom indicates the value of the potential of the drive signal Com for a number obtained by dividing a unit period Tu, which will be described later, by the frequency of the clock signal CLK. In the following description, the number obtained by dividing the unit period Tu by the frequency of the clock signal CLK is referred to as the number of clocks within the unit period N. CLK Specifically, the lookup table is written as follows: CLK is 16, the potential value of the drive signal Com at the 0th clock time to the 15th clock time is stored. The output circuit outputs the potential value of the drive signal Com according to the value indicated by the cumulative adder from the lookup table.

[0042] Drive data dA is input to the DAC section 22. The DAC section 22 converts the input drive data dA into a basic drive signal aA, which is an analog signal.

[0043] The modulation unit 23 receives a master drive signal aA. The modulation unit 23 outputs a modulated signal Ms obtained by pulse-width modulating the master drive signal aA. The gate driver 24 receives a voltage VHV, a voltage GVDD, and a modulated signal Ms. The voltage VHV is, for example, a DC voltage of 42 volts. The voltage GVDD is output from a voltage generator 30 included in the amplification control signal generation circuit 20. The gate driver 24 amplifies the input modulated signal Ms based on the voltage GVDD, and generates an amplification control signal Hgd that is level-shifted to a high-amplitude logic level based on the voltage VHV, and an amplification control signal Lgd that is amplified based on the voltage GVDD by inverting the logic level of the input modulated signal Ms. In other words, the logic levels of the amplification control signal Hgd and the amplification control signal Lgd are mutually exclusive. The amplification control signal Hgd and the amplification control signal Lgd are input to a drive signal output circuit 25.

[0044] The drive signal output circuit 25 operates based on the amplification control signals Hgd and Lgd to output the drive signal Com. The drive signal output circuit 25 includes a transistor 2501, a transistor 2502, a coil 2503, and a capacitor 2504. Note that the transistor 2501 and the transistor 2502 are each, for example, an N-channel FET. FET is an abbreviation for Field Effect Transistor.

[0045] A voltage VHV is supplied to the drain terminal of transistor 2501. An amplification control signal Hgd is supplied to the gate terminal of transistor 2501. A source terminal of transistor 2501 is electrically connected to the drain terminal of transistor 2502. An amplification control signal Lgd is supplied to the gate terminal of transistor 2502. A source electrode of transistor 2502 is connected to ground. Transistor 2501 connected as described above operates in response to the amplification control signal Hgd, and transistor 2502 operates in response to the amplification control signal Lgd. That is, transistors 2501 and 2502 are exclusively turned on. As a result, an amplified modulation signal obtained by amplifying modulation signal Ms based on voltage VHV is generated at the connection point between the source terminal of transistor 2501 and the drain terminal of transistor 2502. That is, transistors 2501 and 2502 function as an amplifier circuit.

[0046] One end of the coil 2503 is commonly connected to the source terminal of the transistor 2501 and the drain terminal of the transistor 2502. The other end of the coil 2503 is connected to one end of the capacitor 2504. The other end of the capacitor 2504 is connected to ground. That is, the coil 2503 and the capacitor 2504 form a low-pass filter. When an amplified modulated signal is supplied to the low-pass filter, the amplified modulated signal is demodulated to generate the drive signal Com. As described above, the drive signal Com is a signal generated by the switching operation of the drive signal output circuit 25, more specifically, by the switching operation of the transistors 2501 and 2502. The drive signal Com generated during the printing operation and the non-printing micro-vibration operation is a sinusoidal AC or non-sinusoidal AC signal, and in this embodiment, is a signal including a trapezoidal wave. The drive signal Com generated by the drive signal output circuit 25 is output from the drive signal generation circuit 2 and input to the switching circuit 10. The configuration of the switching circuit 10 will be described with reference to FIG.

[0047] A4. Configuration of switching circuit 10 7 is a block diagram showing an example of the configuration of the switching circuit 10. The liquid ejection head 1 includes an internal wiring LHa to which a drive signal Com is supplied from a drive signal generating circuit 2, and an internal wiring LHd connected to a ground potential GND.

[0048] 7, one switching circuit 10 controls M piezoelectric elements PZ corresponding to M nozzles N constituting one nozzle row Ln. The internal wiring LHd is electrically connected to the upper electrodes Zu[m] for all m from 1 to M.

[0049] 7, the switching circuit 10 includes M selection circuits 10b[1] to 10b[M] that select whether or not to supply the drive signal Com as the drive signal Vin to the piezoelectric elements PZ[1] to PZ[M], and a connection state designation circuit 10a that designates the connection state of the M selection circuits 10b. The connection state designation circuit 10a generates connection state designation signals SL[1] to SL[M] that designate the M selection circuits 10b[1] to 10b[M] to an on or off state based on an image signal SI supplied from the control unit 7, a clock signal CLK, and a latch signal LAT that defines the unit period Tu of the waveform included in the drive signal Com.

[0050] For example, although not shown, the connection state designation circuit 10a has multiple transfer circuits, multiple latch circuits, and multiple decoders in one-to-one correspondence with the piezoelectric elements PZ[1] to PZ[M]. Of these, the transfer circuit receives an image signal SI. The image signal SI includes an individual designation signal Sd for each piezoelectric element PZ. The individual designation signals Sd are supplied serially and, for example, are transferred sequentially to the multiple transfer circuits in synchronization with a clock signal CLK. The latch circuit latches the individual designation signal Sd supplied to the transfer circuit based on a latch signal LAT. The decoder generates a connection state designation signal SL[m] for each integer m ranging from 1 to M based on the individual designation signal Sd and the latch signal LAT.

[0051] For any integer m between 1 and M, the selection circuit 10b[m] switches between conduction and non-conduction between the internal wiring LHa and the lower electrode Zd[m] of the piezoelectric element PZ[m] in accordance with the connection state designation signal SL[m]. For example, the selection circuit 10b[m] is turned on when the connection state designation signal SL[m] is high level and turned off when the connection state designation signal SL[m] is low level. The upper electrode Zu[m] of the piezoelectric element PZ[m] is connected to a reference potential Vbs. The piezoelectric element PZ[m] is driven in accordance with the potential difference between the drive signal Vin and the reference potential Vbs. The nozzle N[m] ejects an amount of ink in accordance with this potential difference.

[0052] A5. Drive signal Com FIG. 8 is a diagram illustrating the drive signal Com. The drive signal Com has a start potential sustaining element as, an ejection waveform PD, and an end potential sustaining element ae within one unit period Tu. The ejection waveform PD has a first expansion element EF1, a first hold element PW1, a contraction element ET, a second hold element PW2, and a second expansion element EF2, in this order. Note that the drive signal Com may not have either the start potential sustaining element as or the end potential sustaining element ae within one unit period Tu. Note that the first expansion element EF1 is an example of an "expansion element."

[0053] The start potential maintaining element as is an element that maintains the reference potential E0 from the start of one unit period Tu to the start of the ejection waveform PD. The end potential maintaining element ae is an element that maintains the reference potential E0 from the end of the ejection waveform PD to the end of one unit period Tu.

[0054] The first expansion element EF1 changes the potential to expand the pressure chamber CV. Specifically, the first expansion element EF1 changes the potential from a reference potential E0, which is the starting potential of the ejection waveform PD, to a minimum potential EL. The first hold element PW1 is connected to the end of the first expansion element EF1 and maintains the minimum potential EL. The contraction element ET is connected to the end of the first hold element PW1 and changes the potential to contract the pressure chamber CV. Specifically, the contraction element ET changes the potential from the minimum potential EL to a maximum potential EH. The second hold element PW2 is connected to the end of the contraction element ET and maintains the maximum potential EH. The second expansion element EF2 is connected to the end of the second hold element PW2 and changes the potential to expand the pressure chamber CV. Specifically, the second expansion element EF2 changes the potential from the maximum potential EH to the reference potential E0.

[0055] The first expansion element EF1 generates negative pressure in the pressure chamber CV, thereby drawing the ink surface in the nozzle N in the Z1 direction. Hereinafter, the ink surface in the nozzle N may be referred to as the "meniscus." Drawing the meniscus in the Z1 direction may also be referred to as "pull." The contraction element ET generates positive pressure in the pressure chamber CV, thereby pushing the meniscus in the Z2 direction, and ink is ejected in the Z2 direction. Hereinafter, pushing the meniscus in the ejection direction may also be referred to as "push." ​​The second expansion element EF2 generates negative pressure in the pressure chamber CV, thereby drawing the meniscus in the Z1 direction. The ejection waveform PD is a so-called pull-push-pull waveform.

[0056] The drive signal Com may have a waveform different from the ejection waveform PD. For example, the drive signal Com may have a waveform having a first expansion element EF1, a first hold element PW1, a contraction element ET, and a second hold element PW2. In other words, the drive signal Com may have a so-called pull-push waveform that does not have the second expansion element EF2.

[0057] The waveform information CI shown in FIG. 1 indicates the waveform shape of the drive signal Com. Specifically, the waveform information CI includes end information including information indicating the end time of each element of the drive signal Com and information indicating the end potential. For example, the waveform information CI includes end information for a start potential maintaining element as, end information for a first expansion element EF1, end information for a first holding element PW1, end information for a contraction element ET, end information for a second holding element PW2, end information for a second expansion element EF2, and end information for an end potential maintaining element ae. The information indicating the end time included in the end information for the end potential maintaining element ae indicates one unit period Tu.

[0058] For example, if the ground potential GND is 0 [V], the reference potential Vbs is 6 [V], the minimum potential EL is 2.5 [V], and the maximum potential EH is 27.5 [V]. The potential difference ΔEh between the maximum potential EH and the minimum potential EL is 25 [V]. The reference potential E0 is the average voltage of the maximum potential EH and the minimum potential EL.

[0059] FIG. 9 is a diagram showing the change in voltage when a drive signal Com is supplied to the piezoelectric element PZ. For ease of explanation, the difference in potential from the reference potential Vbs supplied to the upper electrode Zu is referred to as "voltage" in this specification. As shown in FIG. 9, the reference voltage V0, which is the start voltage of the first expansion element EF1, is a voltage obtained by subtracting 6 [V] from the reference potential E0. The minimum voltage VL, which is the end voltage of the first expansion element EF1, is -3.5 [V]. The maximum voltage VH, which is the end voltage of the contraction element ET, is 21.5 [V]. The potential difference ΔVh between the maximum voltage VH and the minimum voltage VL is the same as the potential difference ΔEh, which is 25 [V].

[0060] A6. Characteristics of the piezoelectric element PZ A characteristic of the piezoelectric element PZ is that it takes a certain amount of time for the current to stabilize after the potential of the drive signal Com supplied to the piezoelectric element PZ changes. Hereinafter, the period it takes for the current to stabilize after the potential of the drive signal Com changes may be referred to as the "inversion period." Furthermore, the inversion period occurring immediately after the end of the first expansion element EF1 may be referred to as the "pull inversion period," the inversion period occurring immediately after the end of the contraction element ET may be referred to as the "push inversion period," and the inversion period occurring immediately after the end of the second expansion element EF2 may be referred to as the "reset inversion period." Hereinafter, the pull inversion period, push inversion period, and reset inversion period may be collectively referred to as the inversion period. A longer inversion period means that it takes longer for the current to follow the potential change. Therefore, the period during which the changed potential is maintained must be longer depending on the length of the inversion period. By varying the potential of the drive signal Com supplied to the piezoelectric element PZ after the inversion period has expired, the characteristics of the piezoelectric element PZ can be fully utilized. For example, if the contraction element ET is supplied to the piezoelectric element PZ before the pull reversal period expires, the pressure chamber CV will contract before it has been fully expanded, which will reduce the discharge characteristics such as the discharge volume and discharge speed, and the characteristics of the piezoelectric element PZ will not be fully utilized.

[0061] Here, the length of the inversion period may vary. It was unclear when the inversion period would expire. One example of a method for fully utilizing the characteristics of the piezoelectric element PZ is to consider the inversion period to be sufficiently long and vary the potential of the drive signal Com. However, in this case, if the inversion period is short, the voltage supplied to the piezoelectric element PZ is held uselessly, which poses problems in terms of circuit load and power consumption. Because of the above, it was unclear when the inversion period would expire, which led to the problem that an appropriate drive signal Com could not be supplied to the M piezoelectric elements PZ.

[0062] Therefore, the inventor investigated the length of the reversal period to determine the number of simultaneously driven piezoelectric elements PZ, N PZIt has been experimentally found that the number of simultaneously driven piezoelectric elements PZ is proportional to the inversion period. In this specification, the piezoelectric elements PZ that are driven in the same unit period Tu. Furthermore, the inventors have PZ The inventors have theoretically proven that the inversion period is proportional to the number of simultaneously driven N PZ The current and the amount of charge were measured when the ejection waveform PD was supplied to the piezoelectric element PZ for each integer from 1 to 10. The measurement results will be explained below with reference to FIGS.

[0063] 10 is a diagram showing the measurement results of the current response when the ejection waveform PD is supplied to the piezoelectric element PZ. However, in order to avoid the diagram becoming too complicated, in FIG. 10, the number of simultaneously driven N PZ Among the measurement results for each integer from 1 to 10, the number of simultaneous drives N PZ The measurement results are shown only when the number of simultaneous drives N is 5 or 10. PZ 12 is a diagram showing the measurement results of the charge amount response when the ejection waveform PD is supplied to the piezoelectric element PZ for each integer from 1 to 10. PZ 13 is a diagram showing the determination period for each integer from 1 to 10. PZ 10, 11, 12, and 13, the period of the first expansion element EF1, the period of the contraction element ET, and the period of the second expansion element EF2 are 2.5 [μsec], and the period of the first hold element PW1 and the period of the second hold element PW2 are 125 [μsec]. The period of the end potential hold element ae is 242.5 [μsec]. [μsec] means microseconds.

[0064] Furthermore, in the following description, the inversion period is the period from when the potential of the drive signal Com has finished changing until a current of 10% or more of the maximum current flows.

[0065] 10, the horizontal axis of the graph ge1 indicates time, and the vertical axis of the graph ge1 indicates the magnitude of the current. The current characteristic te_5 shown in the graph ge1 is PZ The graph ge1 shows the current characteristics when the number of simultaneous drives N PZ 11 shows the current characteristics when the number of simultaneous drives N is 10. The horizontal axis of graph ge2 shown in FIG. 11 shows time, and the vertical axis of graph ge2 shows the amount of charge. [nC] in graph ge2 means nanocoulomb. The charge amount characteristics ce_1, ce_2, ce_3, ce_4, ce_5, ce_6, ce_7, ce_8, ce_9, and ce_10 shown in graph ge2 are PZ The characteristics of the charge amount when is an integer between 1 and 10 are shown.

[0066] The horizontal axis of the graph ge3 shown in FIG. 12 is the number of simultaneous drives N PZ 13, the vertical axis of graph ge3 indicates the inversion period. Graph ge3 shows an inversion period characteristic te_Pull, an inversion period characteristic te_Push, and an inversion period characteristic te_Reset. The inversion period characteristic te_Pull indicates the characteristic of the pull inversion period. The inversion period characteristic te_Push indicates the characteristic of the push inversion period. The inversion period characteristic te_Reset indicates the characteristic of the reset inversion period. The horizontal axis of graph ge4 shown in FIG. 13 is the number of simultaneously driven N PZ , and the vertical axis of graph ge4 represents the polarization amount. Graph ge4 shows a polarization amount characteristic ce_Pull, a polarization amount characteristic ce_Push, and a polarization amount characteristic ce_Reset. The polarization amount characteristic ce_Pull represents the polarization amount characteristic immediately after the start of the first expansion element EF1. The polarization amount characteristic ce_Push represents the polarization amount characteristic immediately after the start of the contraction element ET. The polarization amount characteristic ce_Reset represents the polarization amount characteristic immediately after the start of the second expansion element EF2.

[0067] For example, as shown by the inversion period characteristic te_Pull and the current characteristic te_5, the number of simultaneously driven N PZ When the number of simultaneously driven N PZThe push inversion period te5_2 when the number of simultaneously driven N PZ When is 5, the reset inversion period te5_3 is approximately 6.1 [μsec].

[0068] In addition, as shown by the inversion period characteristic te_Pull and the current characteristic te_10, the number of simultaneously driven N PZ When the number of simultaneously driven transistors N is 10, the pull inversion period te10_1 is about 18.5 [μsec]. PZ When the number of simultaneously driven N is 10, the push inversion period te10_2 is about 12.4 [μsec]. PZ When is 10, the reset inversion period te10_3 is approximately 10.7 [μsec].

[0069] As shown by the inversion period characteristic te_Pull, the inversion period characteristic te_Push, and the inversion period characteristic te_Reset, the number of simultaneously driven N PZ When increases, the number of simultaneous drives N PZ Since the inversion period increases at approximately the same rate as the rate at which the number of simultaneously driven N PZ Similarly, as the polarization amount characteristic ce_Pull, the polarization amount characteristic ce_Push, and the polarization amount characteristic ce_Reset show, the number of simultaneously driven N PZ It can be inferred that there is a proportional relationship between the amount of polarization and the amount of polarization.

[0070] Next, the number of simultaneous drives N PZThe theory behind why the inversion period is proportional to the polarization characteristic ce_Pull is explained below. Each piezoelectric element PZ is connected in parallel. Therefore, as indicated by the polarization characteristic ce_Pull, the polarization characteristic ce_Push, and the polarization characteristic ce_Reset, the composite capacitance of the simultaneously driven piezoelectric elements PZ, when considered as one piezoelectric element PZ, increases in proportion to the number of simultaneously driven piezoelectric elements PZ. If the number of simultaneously driven piezoelectric elements PZ increases, the composite capacitance also increases. However, if the effect of the increased composite capacitance is not taken into account in the ejection waveform PD, the state of the piezoelectric elements PZ when the selection circuit 10b is switched by the image signal SI will be proportional to the number N of simultaneously driven piezoelectric elements PZ. PZ The inventor considered that this would depend on the voltage supplied to the piezoelectric element PZ, and that the characteristics of the piezoelectric element PZ would not be fully utilized. The inventor calculated the current while the voltage supplied to the piezoelectric element PZ was fluctuating and the current after the voltage fluctuation had ended.

[0071] When the voltage supplied to the piezoelectric element PZ is fluctuating, the current J is expressed by the following equation (1).

number

[0072] where C represents the combined capacitance of all piezoelectric elements PZ driven simultaneously, V represents the voltage applied to the piezoelectric element PZ, R represents the resistance in the circuit including the drive signal generating circuit 2 and the piezoelectric element PZ, and t represents the elapsed time. exp(x) is a function that calculates e to the xth power, and e is Napier's constant. The current J when the voltage of the piezoelectric element PZ is constant is expressed by the following equation (2).

number

[0073] However, J0 is the current when a constant voltage is reached. In other words, J0 can be said to be the current at the point when the fluctuation of the voltage supplied to the piezoelectric element PZ ends.

[0074] The inventors have determined that the number of simultaneous drives is N PZFor each integer from 1 to 10, the current due to the voltage fluctuation caused by the contraction element ET was calculated using equations (1) and (2). More specifically, the inventors calculated the current due to the voltage fluctuation caused by the contraction element ET for each integer from 1 to 10. PZ For each integer from 1 to 10, the current J when the voltage fluctuates between 0 [μsec] and 2.5 [μsec] was calculated using equation (1), and the current J after 2.5 [μsec] was calculated using equation (2).

[0075] 14 is a diagram showing the current values ​​calculated by the formulas (1) and (2). However, in order to avoid the diagram becoming too complicated, in FIG. 14, the number of simultaneously driven N PZ Among the calculation results for each integer from 1 to 10, the number of simultaneous drives N PZ Only the calculation results when the number of simultaneous drives N is 5 or 10 are shown. FIG. 15 is a diagram showing the amount of charge based on the current in FIG. 14. The amount of polarization is calculated by integrating the current. FIG. 16 shows the amount of charge based on the number of simultaneous drives N PZ 17 is a diagram showing the length of the push reversal period based on the current calculated by equations (1) and (2) for each integer from 1 to 10. PZ FIG. 10 is a diagram showing the amount of polarization based on the current calculated by equations (1) and (2) for each integer from 1 to 10.

[0076] The horizontal axis of the graph gt1 shown in FIG. 14 indicates the period from when the voltage fluctuation started. The vertical axis of the graph gt1 indicates the magnitude of the current calculated by the formulas (1) and (2). The current characteristic tt_5 shown in the graph gt1 is PZ The graph gt1 shows the current characteristics calculated by the formulas (1) and (2) when the number of simultaneous drives N is 5. PZ 15 shows the current characteristics calculated by equations (1) and (2) when the number of simultaneously driven elements N is 10. The horizontal axis of graph gt2 shown in FIG. 15 indicates time, and the vertical axis of graph gt2 indicates the amount of charge. The charge amount characteristics ce_1, ce_2, ce_3, ce_4, ce_5, ce_6, ce_7, ce_8, ce_9, and ce_10 shown in graph gt2 are PZis an integer between 1 and 10, the characteristics of the charge amount based on the calculation results of equations (1) and (2) are shown.

[0077] The horizontal axis of the graph gt3 shown in FIG. 16 is the number of simultaneous drives N PZ The vertical axis of the graph gt3 indicates the push inversion period. The inversion period characteristic tt_Push shown by the graph gt3 is PZ The horizontal axis of the graph gt4 shown in FIG. 17 represents the number of simultaneous drives N PZ The vertical axis of the graph gt4 indicates the polarization amount. The polarization amount characteristic ct_Push shown in the graph gt4 is PZ The characteristics of the polarization amount when is an integer from 1 to 10 are shown.

[0078] As the inversion period characteristic tt_Push shows, the number of simultaneously driven N PZ Furthermore, as the polarization characteristic ct_Push shows, the number of simultaneously driven N PZ Furthermore, it was found that the inversion period characteristic te_Push and the inversion period characteristic tt_Push approximately match, and the polarization amount characteristic ce_Push and the polarization amount characteristic ct_Push approximately match.

[0079] By modifying equation (2), the inversion period is the number of simultaneous drives N PZ It is proved that the combined capacitance C is proportional to the following equation (3).

[0080] C=C unit N PZ (3)

[0081] However, C unit indicates the capacitance of one piezoelectric element PZ. Substituting equation (3) into equation (2), dividing both sides by J0, and then taking the logarithm of both sides with Napier's constant e as the base, i.e., the natural logarithm, gives the following equation (4).

number

[0082] Here, ln(x) is a function to obtain the natural logarithm of x. The current J at the end of the inversion period is defined as J inv The length of the reversal period is t inv Then, equation (5) is obtained.

number

[0083] By the definition of the inversion period in this specification, J inv / J0 is 0.1. ln(0.1) is approximately -2.303. Therefore, equation (5) can be transformed into equation (6) below. t inv =2.303RC unit N PZ (6)

[0084] R is a value that hardly changes during a single printing process and can be considered a constant. unit is a value that does not change substantially if the same element is present in each of two or more unit periods Tu of the drive signal Com during a single printing process, and can be regarded as a constant. Therefore, as shown in equation (6), t inv is the number of simultaneous drives N PZ It can be said to be proportional to

[0085] In the liquid ejection device 100 of this embodiment, in the printing process, the reversal period is set to N PZ By using the fact that it is proportional to the number of simultaneous drives N, the timing to change the potential of the drive signal Com is PZ The drive signal Com is output with the potential changed at the adjusted timing. In the following description, the timing at which the potential of the drive signal Com is changed may be referred to as the "potential change timing."

[0086] 1, the liquid ejection device 100 has an image signal output unit 71, an acquisition unit 73, a determination unit 70, and a drive signal generation circuit 2. The image signal output unit 71 generates an image signal SI based on print data Img, and outputs the image signal SI to the liquid ejection head 1. The acquisition unit 73 determines the number of simultaneous drives N from the image signal SI. PZ The determination unit 70 determines the potential change timing based on the number of simultaneously driven N PZ The drive signal generating circuit 2 determines the drive signal Com by adjusting it based on the above. The drive signal generating circuit 2 outputs the drive signal Com determined by the determining unit 70 to the liquid ejection head 1.

[0087] A7. Printing Process in the First Embodiment There are two types of printing processes: bidirectional printing and unidirectional printing. The present disclosure can be applied to both bidirectional printing and unidirectional printing. For simplicity's sake, the following describes a case in which the present disclosure is applied to unidirectional printing. In the following description, one movement of the liquid ejection head 1 in the main scanning direction is referred to as one pass. In unidirectional printing, the liquid ejection device 100 performs an X1-direction printing process in which the liquid ejection head 1 is moved in the X1 direction while ejecting ink to form a partial image corresponding to the first pass on the medium PP. Next, the liquid ejection device 100 transports the medium PP by one pass and performs a movement process in which the liquid ejection head 1 is moved to the end in the X2 direction. Thereafter, the liquid ejection device 100 repeats the X1-direction printing process and the movement process until an image is formed on the medium PP. The X1-direction printing process will be described with reference to FIG. 18 .

[0088] Fig. 18 is a flowchart showing a series of steps in the printing process. Although omitted in Fig. 18 to avoid complicating the drawing, after the liquid ejection device 100 is powered on, the oscillator circuit 4 supplies a clock signal CLK at a constant cycle to the control unit 7, the DA conversion circuit 3, and the liquid ejection head 1.

[0089] When a user of the liquid ejection device 100 instructs execution of a printing process, the control unit 7 assigns 0 to the variable i in step SC2, and executes a drive signal adjustment process in step SC4. The drive signal adjustment process will be described with reference to FIG.

[0090] 19 is a flowchart showing a series of steps in the drive signal adjustment process. In step SC102, the control unit 7 acquires the i-th pixel row from a set of pixels that make up a partial image for one pass of the image indicated by the print data Img. Here, the pixel row is a set of pixels in the direction along the nozzle row Ln. In the first embodiment, the pixel row is a set of M pixels in the direction along the Y axis.

[0091] After completing step SC102, the control unit 7 functions as the image signal output unit 71, and in step SC104 generates an image signal SI from the i-th pixel column. Specifically, for each integer m from 1 to M in the i-th pixel column, if the pixel is one where a dot should be formed, the control unit 7 generates an individual designation signal Sd[m] that indicates that ink should be ejected from the nozzle N[m], and if the pixel is one where a dot should not be formed, the control unit 7 generates an individual designation signal Sd[m] that indicates that ink should not be ejected from the nozzle N[m]. After completing step SC104, the control unit 7 functions as the image signal output unit 71, and in step SC106, outputs the image signal SI to the liquid ejection head 1.

[0092] After the process of step SC106 is completed, the control unit 7 functions as the acquisition unit 73 and acquires the number of simultaneous drives N based on the image signal SI in step SC108. PZ Specifically, the control unit 7 calculates the number of individual designation signals Sd that indicate ink ejection from the nozzle N[m] among the M individual designation signals Sd included in the image signal SI by the number N of simultaneously driven nozzles. PZ Alternatively, the control unit 7 obtains the number of individual designation signals Sd that indicate that ink is not to be ejected from the nozzle N[m] among the M individual designation signals Sd included in the image signal SI, and calculates the value obtained by subtracting the obtained number from M as the number of simultaneously driven nozzles N PZThe control unit 7 may execute the process of step SC108 after the process of step SC104 ends and before the process of step SC106.

[0093] After completing the process of step SC108, in step SC110, the control unit 7 copies the waveform information CI stored in the storage unit 5. Note that the control unit 7 may execute the process of step SC110 before completing the process of step SC108.

[0094] After the process of step SC110 is completed, the control unit 7 functions as the waveform designation signal output unit 75, and in step SC112, the number of simultaneous drives N PZ For example, the control unit 7 adjusts the duplicated waveform information CI so that the potential change timing is delayed based on the number of simultaneous drives N PZ In accordance with an increase in the number of simultaneously driven pulses N, the waveform information CI is adjusted so that one or both of the period of the first hold element PW1 and the period of the second hold element PW2 are extended. In this embodiment, the control unit 7 sets both the period of the first hold element PW1 and the period of the second hold element PW2 to be long. In the following description, the number of simultaneously driven pulses N PZ The period extended based on this may be referred to as the "extension period." Furthermore, the extension period of the first holding element PW1 may be referred to as the "pull extension period," and the extension period of the second holding element PW2 may be referred to as the "push extension period." Furthermore, the pull extension period and the push extension period may be collectively referred to as the extension period. In the first embodiment, the pull extension period and the push extension period are equal.

[0095] For example, the control unit 7 may set the number of simultaneous drives N PZ If is less than the first threshold, the extension period is set to 0, and the number of simultaneous drives N PZ If is greater than or equal to the first threshold and less than the second threshold, the extension period is adjusted to the adjustment period T CLK Set the number of simultaneous drives to N PZ If is greater than or equal to the second threshold, the adjustment period T CLKThe first threshold is an integer between 1 and M. The second threshold is an integer between 1 and M, and is greater than the first threshold. The first integer is 1 or more and is set to a second integer multiple of the number of clocks in a unit period N. CLK The second integer is an integer less than or equal to 1 and is the number of clocks in a unit period N CLK is an integer less than and greater than the first integer.

[0096] The i-th pixel row is an example of a "first pixel row." An integer equal to or greater than the first threshold and less than the second threshold is an example of a "first number," and an integer equal to or greater than the second threshold and less than M is an example of a "second number." Adjustment period T CLK The first integral multiple of the adjustment period T CLK The second integral multiple of is an example of the “second period” and the “fourth period.” That is, in the first embodiment, the “first period” is equal to the “third period,” and the “second period” is equal to the “fourth period.”

[0097] Adjustment cycle T CLK It is preferable that the second integral multiple of satisfies, for example, the following formula (7). T CLK × second integer ≥ 2.303RC unit N PZ (7)

[0098] The right-hand side of equation (7) is the same as the right-hand side of equation (6).

[0099] For example, the number of simultaneous drives N PZ is equal to or greater than the first threshold and less than the second threshold, the control unit 7 adjusts the end times included in the end information of the first hold element PW1 of the waveform information CI and the end information of the contraction element ET within the adjustment period T CLKThe termination times of the elements after the second hold element PW2 must be set to a first integer multiple later than the unit period Tu. The termination times of the elements after the second hold element PW2 must be set to a push extension period, which is the extension period of the second hold element PW2, plus a pull extension period, which is the extension period of the first hold element PW1. Therefore, the control unit 7 adjusts the termination times included in the termination information of the second hold element PW2 and the termination information of the second expansion element EF2 of the waveform information CI to a value later than the adjustment period T within a range not exceeding the unit period Tu. CLK A specific example of the process in step SC112 will be explained after the explanation of the series of processes shown in FIGS.

[0100] After the process of step SC112 is completed, the control unit 7 functions as the waveform designation signal output unit 75, and in step SC114 generates the waveform designation signal dCom based on the adjusted waveform information CI, and outputs the waveform designation signal dCom to the DA conversion circuit 3. Specifically, the control unit 7 refers to the adjusted waveform information CI and calculates the potential of the drive signal Com at the time of the 0th clock by multiplying the number of clocks N within the unit period by 1 / N. CLK The potential value of the drive signal Com at time -1 is generated as the waveform designation signal dCom. Then, the control unit 7 writes the generated waveform designation signal dCom into the lookup table of the DAC interface 21. After completing the process of step SC114, the control unit 7 ends the series of processes shown in Fig. 19 and executes the process of step SC6 shown in Fig. 18.

[0101] Returning to Fig. 18 for explanation, when the waveform designation signal dCom is output to the DA conversion circuit 3, the DA conversion circuit 3 generates the reference drive signal aA based on the waveform designation signal dCom and the clock signal CLK in step SD2. Specifically, the control unit 7 writes the waveform designation signal dCom to the lookup table of the DAC interface 21 in step SC114. This waveform designation signal dCom is generated based on waveform information CI in which the timing at which the potential is changed has been adjusted in step SC112. Therefore, the timing at which the potential is changed in the generated reference drive signal aA has been adjusted. After the processing of step SD2 is completed, the DA conversion circuit 3 outputs the reference drive signal aA to the drive signal generation circuit 2 in step SD4.

[0102] When the basic drive signal aA is output to the drive signal generation circuit 2, the drive signal generation circuit 2 generates the drive signal Com based on the basic drive signal aA in step SV2. Next, the drive signal generation circuit 2 outputs the drive signal Com to the liquid ejection head 1 in step SV4.

[0103] When the image signal SI and the drive signal Com are output to the liquid ejection head 1, the liquid ejection head 1 ejects ink onto the medium PP based on the image signal SI and the drive signal Com in step SH2.

[0104] After completing the process of step SC4, the control unit 7 determines in step SC6 whether the i-th pixel column is located at the end of the image indicated by the print data Img in the X1 direction. If the determination result of step SC6 is negative, the control unit 7 increments the value of the variable i by 1 in step SC8 and returns the process to step SC4. If the determination result of step SC6 is positive, the control unit 7 ends the series of processes shown in Figure 18. A specific example of the process of step SC112 will be described using Figure 20.

[0105] FIG. 20 is a diagram illustrating a specific example of the processing of step SC112. In FIG. 20, the explanation will be given on the assumption that the unit period Tu divided by the frequency of the clock signal CLK is 16, the number M of nozzles N of the liquid ejection head 1 is 8, and an image G1 represented by the print data Img shown in FIG. 20 is formed on a medium PP. The image G1 is composed of 24 pixels. In the image G1, 8 pixels are arranged in the direction along the Y axis, and 3 pixels are arranged in the direction along the X axis. Therefore, the image G1 has three pixel columns along the Y axis. Hereinafter, the pixel column located at the end of the image G1 in the X2 direction will be referred to as pixel column A, the pixel column located at the end of the image G1 in the X1 direction will be referred to as pixel column C, and the pixel column between pixel column A and pixel column C will be referred to as pixel column B. The liquid ejection device 100 forms pixel row A on the medium PP in the first unit period Tu[0], forms pixel row B on the medium PP in the second unit period Tu[1], and forms pixel row C on the medium PP in the third unit period Tu[2].

[0106] As shown in Figure 20, the liquid ejection device 100 forms dots for the fourth pixel counting from the end in the Y2 direction for pixel row A, forms dots for the second, fourth, fifth, and eighth pixels counting from the end in the Y2 direction for pixel row B, and forms dots for the first to fourth and sixth to eighth pixels counting from the end in the Y2 direction for pixel row C.

[0107] Table H1 shown in FIG. 20 shows the number of simultaneous drives N PZ As shown in Table H1, the control unit 7 determines the number of simultaneous drives N PZ If is less than M × 0.33, set the extension period to 0 and the number of simultaneous drives N PZ If M×0.33 or more and less than M×0.66, the extension period is adjusted to T CLK Set the number of simultaneous drives to N PZ If is M × 0.66 or more, the adjustment period T CLK Set it to twice the value.

[0108] In the unit period Tu[0], as can be seen from pixel column A, the number of simultaneously driven pixels N PZSince is 1, the number of simultaneous drives N PZ is less than M×0.33. Therefore, in step SC112, the control unit 7 sets the extension period to 0, that is, does not adjust the waveform information CI at all.

[0109] In the unit period Tu[1], as can be seen from pixel column B, the number of simultaneously driven pixels N PZ Since is 4, the number of simultaneous drives N PZ is equal to or greater than M×0.33 and less than M×0.66. Therefore, in step SC112, the control unit 7 sets the extension period to the adjustment period T CLK That is, the control unit 7 sets the end times included in the end information of the first holding element PW1 and the end information of the contraction element ET to 1 times the adjustment period T CLK , and the end times included in the end information of the second hold element PW2 of the waveform information CI and the end information of the second expansion element EF2 are set to be 1 time slower than the adjustment period T CLK Set it to twice as slow as the

[0110] In the unit period Tu[2], as can be seen from the pixel column C, the number of simultaneously driven pixels N PZ Since is 7, the number of simultaneous drives N PZ is equal to or greater than M×0.66. Therefore, in step SC112, the control unit 7 sets the extension period to the adjustment period T CLK That is, the control unit 7 sets the end times included in the end information of the first holding element PW1 and the end information of the contraction element ET to twice the adjustment period T CLK and the end times included in the end information of the second hold element PW2 of the waveform information CI and the end information of the second expansion element EF2 are set to twice as slow as the adjustment period T CLK Set it to four times slower.

[0111] 20, the duration of the first hold element PW1 and the duration of the second hold element PW2 are extended by extending the ending times of the first hold element PW1 and the second hold element PW2, but this is not limiting. For example, the control unit 7 may extend the duration of the first hold element PW1 and the duration of the second hold element PW2 by extending the starting times of the first hold element PW1 and the second hold element PW2 in the past, within a range that does not exceed the unit period Tu.

[0112] A8. Summary of the first embodiment Hereinafter, the i-th pixel row of the image formed on the medium PP is an example of a "first pixel row," an integer equal to or greater than the first threshold and less than the second threshold is an example of a "first number," an integer equal to or greater than the second threshold and less than M is an example of a "second number," and the adjustment period T CLK The first integral multiple of is an example of the "first period" and the "third period", and the adjustment period T CLK The first embodiment will be summarized as follows, with the second integral multiple of the above being an example of the "second period" and the "fourth period".

[0113] The liquid ejection device 100 includes a liquid ejection head 1, an acquisition unit 73, a determination unit 70, and a drive signal generation circuit 2. The liquid ejection head 1 is provided with a plurality of piezoelectric elements PZ that are driven to apply pressure to ink in pressure chambers CV. The acquisition unit 73 acquires a simultaneous drive number N, which is the number of piezoelectric elements PZ that are driven simultaneously among the plurality of piezoelectric elements PZ. PZ The determination unit 70 obtains the number of simultaneous drives N PZ The timing for changing the potential of the drive signal Com for driving the piezoelectric element PZ is set to the number of simultaneously driven N PZ The drive signal generating circuit 2 determines the drive signal Com by adjusting it based on the above. The drive signal generating circuit 2 outputs the drive signal Com determined by the determining unit . The first embodiment can also be defined as a method for driving a liquid ejection device having a liquid ejection head 1, a drive signal generation circuit 2 that outputs a drive signal Com for driving one or more of the plurality of piezoelectric elements PZ, and a control unit 7 that controls the liquid ejection head 1 and the drive signal generation circuit 2. Here, the control unit 7 controls the DA conversion circuit 3, and the DA conversion circuit 3 controls the drive signal generation circuit 2, so it can be said that the control unit 7 controls the drive signal generation circuit 2. In step SC102, the control unit 7 determines the number of simultaneously driven elements N PZ In step SC114, the waveform specification signal dCom is output, thereby determining the number of simultaneous drives N PZ The drive signal generating circuit 2 outputs the drive signal Com whose potential has been changed at the timing adjusted based on the above. As mentioned above, the number of simultaneous drives N PZ is proportional to the inversion period. Therefore, according to the first embodiment, the period during which the voltage supplied to the piezoelectric element PZ is needlessly maintained can be shortened compared to an embodiment in which the potential of the drive signal Com is varied assuming that the inversion period is sufficiently long. Furthermore, according to the first embodiment, compared to an embodiment in which the timing for changing the potential of the drive signal Com is not adjusted, contraction of the pressure chamber CV before the pressure chamber CV is sufficiently expanded can be suppressed, thereby making it possible to further utilize the characteristics of the piezoelectric element PZ. In other words, according to the first embodiment, an appropriate drive signal Com according to the length of the inversion period can be supplied to M piezoelectric elements PZ.

[0114] The liquid ejection device 100 further includes an oscillator circuit 4 that outputs a plurality of clock signals CLK at a constant frequency to adjust the timing for changing the potential of the drive signal Com, and the determining unit 70 determines the number of simultaneous drives N PZ and the clock signal CLK, at least one element of the drive signal Com is adjusted to adjust the potential change timing. According to the first embodiment, the potential change timing can be adjusted in synchronization with the clock signal CLK.

[0115] The drive signal Com includes at least a first expansion element EF1 that changes the potential to expand the pressure chamber CV, a first hold element PW1 that holds the potential constant after the first expansion element EF1, a contraction element ET that changes the potential to contract the pressure chamber CV after the first hold element PW1, and a second hold element PW2 that holds the potential constant after the contraction element ET. According to the first embodiment, whether a pull-push-pull waveform or a pull-push waveform is supplied to the piezoelectric elements PZ, an appropriate drive signal Com can be supplied to the M piezoelectric elements PZ.

[0116] The liquid ejection head 1 ejects ink onto the medium PP to form an image on the medium PP, and the determination unit 70 determines the number of simultaneously driven pixels N in the i-th pixel column. PZ is an integer equal to or greater than the first threshold and less than the second threshold, the period of the first hold element PW1 is the adjustment period T CLK The number of simultaneously driven pixels in the i-th pixel column is N PZ is an integer equal to or greater than the second threshold value M, the period of the first hold element PW1 is the adjustment period T CLK The potential change timing is adjusted by extending the period by a second integer multiple. According to the first embodiment, compared to an aspect in which the length of the period of the first holding element PW1 is fixed, it is possible to supply an appropriate drive signal Com to the M piezoelectric elements PZ. Specifically, the liquid ejection device 100 in the first embodiment can shorten the period in which the voltage supplied to the piezoelectric elements PZ is needlessly held when the pull reversal period is shorter than the fixed length, and can further bring out the characteristics of the piezoelectric elements PZ when the pull reversal period is longer than the fixed length.

[0117] The determination unit 70 determines the number of simultaneously driven pixels N in the i-th pixel column. PZ is an integer equal to or greater than the first threshold and less than the second threshold, the period of the second hold element PW2 is the adjustment period T CLK The number of simultaneously driven pixels in the i-th pixel column is N PZ is an integer equal to or greater than the second threshold value M, the period of the second hold element PW2 is the adjustment period T CLKThe potential change timing is adjusted by extending the period by a second integer multiple. According to the first embodiment, compared to the aspect in which the length of the period of the second holding element PW2 is fixed, if the push reversal period is shorter than the aforementioned fixed length, the period in which the voltage supplied to the piezoelectric element PZ is needlessly held can be shortened, and if the push reversal period is longer than the aforementioned fixed length, the characteristics of the piezoelectric element PZ can be further brought out.

[0118] The liquid ejection head 1 forms an image on the medium PP by ejecting ink onto the medium PP, and the liquid ejection device 100 further includes an image signal output unit 71 that outputs, for each pixel row included in the image, an image signal SI that indicates whether or not ink is to be ejected from a nozzle N that communicates with a pressure chamber CV to which each of the plurality of piezoelectric elements PZ applies pressure, and an acquisition unit 73 determines the number N of simultaneously driven pixels based on the image signal SI. PZ is obtained for each pixel column. As shown in FIG. 20, the number of simultaneously driven pixels N PZ According to the first embodiment, the number of simultaneously driven pixels per pixel column N PZ In response to this, an appropriate drive signal Com can be supplied to the M piezoelectric elements PZ.

[0119] B. Second embodiment As can be seen from the inversion period characteristics te_Pull and te_Push in FIG. 12, the same number of simultaneously driven N PZ Even if the pull inversion period is longer than the push inversion period, the pull extension period is set to be longer than the push extension period. The second embodiment will be described below.

[0120] 21 is a diagram for explaining a specific example of the process of step SC112 in the second embodiment. Table H2 shown in FIG. 20 shows the number of simultaneous drives N PZ As shown in Table H2, the control unit 7 determines the number of simultaneous drives N PZ If M is less than M×0.33, the extension period is set to 0. Furthermore, as shown in Table H2, the control unit 7 sets the number of simultaneously driven N PZIf M×0.33 or more and less than M×0.66, the pull extension period is adjusted to T CLK and set the push extension period to twice the adjustment period T CLK Furthermore, as shown in Table H2, the control unit 7 sets the number of simultaneously driven N PZ If M×0.66 or more, the pull extension period is adjusted to T CLK and set the push extension period to four times the period T CLK Set it to twice the value.

[0121] In the second embodiment, the number of simultaneous drives N PZ The adjustment period T set for the pull extension period when is M × 0.33 or more and less than M × 0.66 CLK The number of simultaneously driven N is an example of the "first period". PZ The adjustment period T to be set for the push extension period when M × 0.33 or more and less than M × 0.66 CLK is an example of the "third period." In other words, in the second embodiment, the "first period" is longer than the "third period." Similarly, when the number of simultaneously driven N PZ The adjustment period T to be set for the pull extension period when M × 0.66 or more CLK The number of simultaneous drives N is four times the number of simultaneous drives N. PZ The adjustment period T to be set for the push extension period when M × 0.66 or more CLK The "second period" is an example of the "fourth period." That is, in the second embodiment, the "second period" is longer than the "fourth period." Note that, although the "first period" and the "fourth period" are equal to each other in the second embodiment, they may be different.

[0122] The unit period Tu[0] is the same as that in FIG. 20, so the explanation will be omitted. The unit period Tu[1] is the number of simultaneously driven N PZ is equal to or greater than M×0.33 and less than M×0.66. The control unit 7 calculates the end times included in the end information of the first hold element PW1 and the end information of the contraction element ET in the adjustment period T CLKAs in the first embodiment, the termination times of the elements after the second hold element PW2 must be set twice as late as the adjustment period T. ...1 must be set twice as late as the adjustment period T. As in the first embodiment, the termination times of the elements after the second hold element PW1 must be set twice as late as the adjustment period T. As in the first embodiment, the termination times of the elements after the second hold element PW1 must be set twice as late as the adjustment period T CLK Set it to three times slower.

[0123] In the unit period Tu[2], the number of simultaneous drives N PZ is equal to or greater than M×0.66. The control unit 7 calculates the end times included in the end information of the first hold element PW1 and the end information of the contraction element ET by the adjustment period T CLK and the end times included in the end information of the second hold element PW2 of the waveform information CI and the end information of the second expansion element EF2 are set four times slower than the adjustment period T CLK Set it to 6 times slower.

[0124] As described above, according to the second embodiment, the first period is longer than the third period, and the second period is longer than the fourth period. In other words, the pull extension period is longer than the push extension period. According to the second embodiment, the same number of simultaneously driven N PZ Even in this case, since the pull inversion period is longer than the push inversion period, by setting the pull extension period longer than the push extension period, it is possible to supply appropriate drive signals Com to the M piezoelectric elements PZ, as compared to the first embodiment. The reason why the pull inversion period is longer than the push inversion period will be described with reference to FIG. 22.

[0125] 22 is a diagram showing a hysteresis curve showing the relationship between the voltage and polarization of the piezoelectric body Zm. The horizontal axis of the graph gh1 shown in FIG. 22 is voltage [V], and the vertical axis is polarization [μC / cm 2In order to increase the discharge rate, it is preferable to change the voltage from the coercive voltage -Vc to the saturated positive voltage. During the period of the first expansion element EF1, in other words, during the period when the voltage changes from the reference voltage V0 to the minimum voltage VL, the voltage decreases along the path Rcv1 of the hysteresis curve shown in Figure 22 toward the coercive voltage -Vc, which is the reference voltage V0 in the coercive electric field, and the polarization changes to the negative side. In other words, it changes as shown by the arrow a1.

[0126] During the contraction element ET, in other words, during the period when the voltage changes from the minimum voltage VL to the maximum voltage VH, the path changes from the path Rcv1 to the path Rcv2 of the graph gh1, and the polarization changes to the positive side by the potential difference ΔVh.

[0127] C in equation (6) unit becomes larger as the slope of the graph gh1 becomes steeper. During the pull inversion period, the polarization changes along the curve cp_Pull in the graph gh1, and during the push inversion period, the polarization changes along the curve cp_Push in the graph gh1. As can be seen from FIG. 22, the slope of the curve cp_Pull is steeper than the slope of the curve cp_Push. Therefore, from equation (6), it can be seen that for the same number of simultaneously driven electrodes N PZ Even so, the pull extension period is longer than the push extension period.

[0128] In the liquid ejection device 100 of the first embodiment, the pull extension period and the push extension period are the same, so the processing load on the control unit 7 can be reduced compared to the liquid ejection device 100 of the second embodiment.

[0129] C. Variations The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within the scope of not mutually contradictory.

[0130] C1. First modified example In step SC112 of each of the above-described embodiments, the control unit 7 determines the number of simultaneous drives N PZAlternatively, in step SC112, the control unit 7 may adjust the waveform information CI so that the period of the first hold element PW1 is extended in response to an increase in the number of simultaneously driven elements N PZ In response to an increase in , the waveform information CI may be adjusted so that the period of the second hold element PW2 is extended, and the period of the first hold element PW1 may remain unchanged.

[0131] C2. Second variant In each of the above-described embodiments, in order to respond to the reset inversion period, the control unit 7 sets the number of simultaneously driven N PZ The control unit 7 may adjust the waveform information CI so that the period of the end potential maintaining element ae is extended in response to the increase in the number of simultaneously driven pulses N PZ In response to an increase in , the waveform information CI may be adjusted so that the period of the end potential holding element ae is extended, and the periods of the first holding element PW1 and the second holding element PW2 may remain unchanged.

[0132] C3. Third variant In the above-described embodiments, a serial-type liquid ejection device in which the storage case 921 that houses the liquid ejection head 1 moves back and forth has been exemplified, but the present disclosure can also be applied to a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium PP. In the third modified example, when the nozzle row Ln is in a direction that intersects the Y axis, for example, a direction along the X axis, the pixel row of pixels formed on the medium PP is a collection of M pixels in a direction along the X axis.

[0133] C4. Fourth Variation The liquid ejection device 100 exemplified in each of the above-described embodiments can be employed in various devices, such as facsimile machines and copiers, as well as devices dedicated to printing. However, the uses of the liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Furthermore, a liquid ejection device that ejects a solution of an organic substance related to a living organism is used as a manufacturing device for manufacturing biochips, for example. [Explanation of symbols]

[0134] 1...liquid ejection head, 2...drive signal generation circuit, 3...DA conversion circuit, 4...oscillating circuit, 5...storage unit, 6, 7...control unit, 10...switching circuit, 10a...connection state designation circuit, 10b...selection circuit, 20...amplification control signal generation circuit, 21...DAC interface, 22...DAC unit, 23...modulation unit, 24...gate drive unit, 25...drive signal output circuit, 30...voltage generation unit, 32...flow path substrate, 34...pressure chamber substrate, 36...diaphragm, 42...casing unit, 44...sealing member, 46...nozzle plate, 48...vibration absorber, 70...determination unit, 71...image signal output unit, 73...acquisition unit, 75...waveform designation signal output unit, 91...movement mechanism, 92...transport mechanism, 93...liquid container, 100...liquid ejection device, 322...opening, 324...supply flow path, 326...communicating flow path, 328...relay flow path, 61...elastic film, 362...insulating film, 422...accommodating section, 424...inlet port, 442...sealed space, 921...accommodating case, 922...endless belt, 2501, 2502...transistor, 2503...coil, 2504...capacitor, A, B...pixel row, C...composite capacitance, C...pixel row, CI...waveform information, CLK...clock signal, CV...pressure chamber, Com...drive signal, E0...reference potential, EF1...first expansion element, EF2...second expansion element, EH...highest potential, EL...lowest potential, ET...contraction element, G1...image, GND...ground potential, GVDD...voltage, HD...recording head, Hgd...amplification control signal, Img...print data, LAT...latch signal, LHa, LHd...internal wiring, Lgd...amplification control signal, Ln...nozzle row, M...number, Ms...modulation signal, N CLK …number of clocks in unit period, N…nozzle, NPZ ...Number of simultaneous drives, PD...Ejection waveform, PP...Medium, PW1...First holding element, PW2...Second holding element, PZ...Piezoelectric element, R...Liquid storage chamber, Rcv1, Rcv2...Path, SI...Image signal, SL...Connection status designation signal, Sd...Individual designation signal, T...Adjustment cycle, Tu...Unit period, V0...Reference voltage, VH...Maximum voltage, VHV...Voltage, VL...Minimum voltage, Vbs...Reference potential, Vin...Drive signal, Zd...Lower electrode, Zm...Piezoelectric element, Zu...Upper electrode, a1...Arrow, aA...Base drive signal, ae...End potential maintenance element, as...Start potential maintenance element, ce_1...Charge amount characteristics, ce_Pull, ce_P ush,ce_Reset,ct_Push...polarization amount characteristics, dA...drive data, dCom...waveform specification signal, e...Napier's number, ge1,ge2,ge3,ge4,gh1,gt1,gt2,gt3,gt4...graph, te5_1,te10_1...pull inversion period, te5_2,te10_2...push inversion period, te5_3,te10_3...reset inversion period, te_5,te_10...current characteristics, te_Pull,te_Push,te_Reset...inversion period characteristics, tt_10,tt_5...current characteristics, tt_Push...inversion period characteristics, ΔEh,ΔVh...potential difference.

Claims

1. a liquid ejection head provided with a plurality of piezoelectric elements that are driven to apply pressure to liquid in a pressure chamber; an acquisition unit that acquires a number of simultaneously driven piezoelectric elements, which is the number of piezoelectric elements that are simultaneously driven among the plurality of piezoelectric elements; a determination unit that determines the drive signals by adjusting timings for changing potentials of drive signals for driving the simultaneously driven number of piezoelectric elements based on the simultaneously driven number; a drive signal output unit that outputs the drive signal determined by the determination unit; A liquid ejection device comprising:

2. further comprising an adjustment signal output unit that outputs a plurality of adjustment signals at a constant frequency for adjusting the timing; the determination unit determines the drive signal by adjusting at least one element of the drive signal based on the number of simultaneously driven devices and the adjustment signal. The liquid ejection device according to claim 1 .

3. A liquid ejection device as described in claim 2, characterized in that the drive signal includes at least an expansion element that changes the potential to expand the pressure chamber, a first holding element that holds the potential constant after the expansion element, a contraction element that changes the potential to contract the pressure chamber after the first holding element, and a second holding element that holds the potential constant after the contraction element.

4. The liquid ejection head ejects a liquid onto a medium to form an image on the medium; The liquid ejection device described in claim 3, characterized in that the determination unit adjusts the timing by extending the period of the first holding element by a first period when the number of simultaneously driven pixels in a first pixel column of the image is a first number, and by extending the period of the first holding element by a second period longer than the first period when the number of simultaneously driven pixels in the first pixel column is a second number greater than the first number.

5. The liquid ejection device described in claim 4, characterized in that the determination unit adjusts the timing by extending the period of the second holding element to a third period when the number of simultaneously driven pixels in the first pixel column is the first number, and by extending the period of the second holding element to a fourth period longer than the third period when the number of simultaneously driven pixels in the first pixel column is the second number.

6. the first period is equal to the third period; 6. The liquid ejection apparatus according to claim 5, wherein the second period is equal to the fourth period.

7. the first period is longer than the third period; The liquid ejection apparatus according to claim 5 , wherein the second period is longer than the fourth period.

8. The liquid ejection head ejects a liquid onto a medium to form an image on the medium; The liquid ejection device described in claim 3, characterized in that the determination unit adjusts the timing by extending the period of the second holding element by a third period when the number of simultaneously driven pixels in a first pixel column of the image is a first number, and by extending the period of the second holding element by a fourth period longer than the third period when the number of simultaneously driven pixels in the first pixel column is a second number greater than the first number.

9. The liquid ejection head ejects a liquid onto a medium to form an image on the medium; an image signal output unit that outputs, for each pixel row included in the image, an image signal that indicates whether or not liquid is to be ejected from a nozzle that communicates with a pressure chamber to which each of the plurality of piezoelectric elements applies pressure; The liquid ejection device according to claim 1 , wherein the acquisition unit acquires the number of simultaneously driven pixels for each pixel column based on the image signal.

10. a liquid ejection head provided with a plurality of piezoelectric elements that are driven to apply pressure to liquid in a pressure chamber; a drive signal output unit that outputs a drive signal for driving one or more of the plurality of piezoelectric elements; a control unit that controls the liquid ejection head and the drive signal output unit; A method for driving a liquid ejection device having The control unit A simultaneous drive number, which is the number of piezoelectric elements that are simultaneously driven among the plurality of piezoelectric elements, is obtained; outputting the drive signal, the potential of which has been changed at a timing adjusted based on the number of simultaneously driven devices, to the drive signal output unit; A method for driving a liquid ejection device.

Images