Liquid discharge device and control method for liquid discharge device

Abstract

To appropriately and easily evaluate the stability of liquid discharge from a nozzle without requiring external elements such as an imaging environment.SOLUTION: A liquid discharge device 100 comprises: a liquid discharge head 1 that includes a nozzle N that discharges ink, a piezoelectric element PZ corresponding to the nozzle N, a vibration plate 14 that vibrates by driving of the piezoelectric element PZ, and a detection circuit 19 that detects residual vibration of the vibration plate 14 caused by driving of the piezoelectric element PZ; and an evaluation control unit 40 that executes a first evaluation for evaluating stability of ink discharge from the nozzle N. In the first evaluation, the evaluation control unit 40 causes the detection circuit 19 to detect, as the first residual vibration, the residual vibration resulting from continuous execution of discharge driving in which the piezoelectric element PZ is driven by a drive signal COM for discharging ink from the nozzle N, and evaluates the stability of ink discharge from the nozzle N on the basis of the first residual vibration detected by the detection circuit 19.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Liquid ejection devices are known that print images by ejecting liquid such as ink from nozzles using piezoelectric elements. For example, a liquid ejection device has a liquid ejection head that ejects liquid filled in a pressure chamber from a nozzle by vibrating a diaphragm that constitutes part of the pressure chamber using a piezoelectric element. For this type of liquid ejection device, a method for detecting nozzle ejection defects has been proposed as an evaluation method for the liquid ejection head. For example, Patent Document 1 discloses an ejection image analysis device that analyzes multiple ejection images taken at a regular interval to show the flight state of droplets ejected from the nozzles of a droplet ejection device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-172053 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a method of analyzing multiple ejection images taken at a fixed timing to show the flight state of droplets ejected from a nozzle, it is necessary to prepare an evaluation environment for detecting nozzle ejection defects, and therefore, the burden of preparing the evaluation environment is heavy when analyzing multiple ejection images.

[0005] As a method for detecting nozzle ejection defects without requiring external elements such as a photographing environment, for example, a method is known in which residual vibrations generated in a vibration plate after a piezoelectric element is driven are detected, and ejection defects such as increased viscosity and non-ejection of the liquid are detected based on the detected residual vibrations. With a method that uses residual vibrations, there is no need to prepare a special evaluation environment, and therefore an increase in the load required to detect nozzle ejection defects is suppressed.

[0006] Here, in a liquid ejection device, it is desirable to determine the waveform of the drive signal that drives the piezoelectric element so that the ejection of liquid from the nozzle is stable. Therefore, when evaluating a liquid ejection head, it is considered that the ejection stability is evaluated instead of or in addition to the above-mentioned detection of ejection defects. For this reason, it is desirable to be able to appropriately and easily evaluate the stability of liquid ejection from the nozzle and determine the waveform of the drive signal that drives the piezoelectric element without requiring external factors such as a shooting environment. In particular, it is desirable to appropriately and easily evaluate the stability of liquid ejection from the nozzle without requiring external factors such as a shooting environment. [Means for solving the problem]

[0007] In order to solve the above problems, the liquid ejection device of the present invention comprises a liquid ejection head including a nozzle that ejects liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when the piezoelectric element is driven, and a detection unit that detects residual vibration of the vibration plate caused by driving the piezoelectric element, and a control unit that performs a first evaluation that evaluates the stability of liquid ejection from the nozzle, wherein in the first evaluation, the control unit causes the detection unit to detect the residual vibration caused by continuously executing an ejection drive that drives the piezoelectric element with a drive signal that ejects liquid from the nozzle as a first residual vibration, and evaluates the stability of liquid ejection from the nozzle based on the first residual vibration detected by the detection unit.

[0008] Another liquid ejection device according to the present invention comprises a liquid ejection head including a nozzle for ejecting liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when the piezoelectric element is driven, and a detection unit that detects residual vibration of the vibration plate caused by driving the piezoelectric element, and a control unit, wherein the control unit causes the detection unit to detect the residual vibration caused by multiple repetitions of an ejection drive that drives the piezoelectric element with a drive signal that ejects liquid from the nozzle as a first residual vibration, and determines the waveform of the drive signal based on the first residual vibration detected by the detection unit.

[0009] In addition, a control method for a liquid ejection device according to the present invention is a control method for a liquid ejection device having a liquid ejection head including a nozzle that ejects liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when the piezoelectric element is driven, and a detection unit that detects residual vibration of the vibration plate caused by driving the piezoelectric element, wherein the detection unit detects the residual vibration caused by repeated ejection drive of driving the piezoelectric element with a drive signal that ejects liquid from the nozzle as a first residual vibration, and evaluates the stability of ejection of liquid from the nozzle based on the first residual vibration detected by the detection unit. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an example of a configuration of a liquid ejection apparatus according to an embodiment of the present invention. [Figure 2] FIG. 1 is a configuration diagram schematically illustrating a liquid ejection device. [Figure 3] FIG. 2 is an exploded perspective view of the liquid ejection head. [Figure 4] FIG. 4 is a cross-sectional view taken along the line III-III shown in FIG. [Figure 5] FIG. 2 is a block diagram showing an example of the configuration of a liquid ejection head. [Figure 6] 10 is a timing chart showing an example of an operation of the liquid ejection device in a unit period. [Figure 7] FIG. 10 is a diagram showing an example of a waveform of a residual vibration signal. [Figure 8]10 is a flowchart showing an example of the operation of the liquid ejection device when evaluating the stability of ink ejection from the nozzles. [Figure 9] 9 is a flowchart showing an example of the evaluation of stability shown in FIG. 8. [Figure 10] FIG. 10 is a block diagram showing an example of the configuration of a liquid ejection head according to a first modified example. [Figure 11] 10 is a timing chart showing an example of the operation of the liquid ejection device according to the first modified example. [Figure 12] 10 is a flowchart showing an example of the operation of a liquid ejection device according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] [1. Embodiment] First, an overview of a liquid ejection device 100 according to this embodiment will be described with reference to Fig. 1. In this embodiment, it is assumed as an example that the liquid ejection device 100 is an inkjet printer that forms an image by ejecting ink onto a medium PP. In this embodiment, it is assumed that the medium PP is recording paper shown in Fig. 2, which will be described later. Ink is an example of a "liquid."

[0013] FIG. 1 is a block diagram showing an example of the configuration of a liquid ejection device 100 according to an embodiment of the present invention.

[0014] Print data IMG indicating an image to be formed by the liquid ejection device 100 is supplied from a host computer such as a personal computer or a digital camera to the liquid ejection device 100. The liquid ejection device 100 executes a printing process to form, on a medium PP, an image indicated by the print data IMG supplied from the host computer.

[0015] The liquid ejection device 100 includes a liquid ejection head 1 provided with an ejection section D including nozzles N that eject ink, a drive signal generation unit 2 that generates a drive signal COM for driving the ejection section D, and an analysis unit 3 that analyzes residual vibrations (described later). The nozzles N will be described later with reference to FIGS. 3 and 4. The liquid ejection device 100 also includes a control unit 4 that controls each section of the liquid ejection device 100, and a storage unit 5 that stores various information such as print data IMG and a control program PG for the liquid ejection device 100. The liquid ejection device 100 also includes a maintenance unit 7 that performs maintenance processing for the liquid ejection head 1, a medium transport mechanism 8 that transports a medium PP, a carriage transport mechanism 9 that reciprocates a carriage 91, and an ink container 60 that stores ink. The carriage 91 will be described later with reference to FIG. 2.

[0016] In this embodiment, it is assumed that the liquid ejection head 1 and the drive signal generation unit 2 correspond to each other, and that the liquid ejection head 1 and the analysis unit 3 correspond to each other. For example, the liquid ejection device 100 may have a plurality of liquid ejection heads 1, a plurality of drive signal generation units 2, and a plurality of analysis units 3. In this case, for example, the plurality of drive signal generation units 2 correspond to the plurality of liquid ejection heads 1 one-to-one, and the plurality of analysis units 3 correspond to the plurality of liquid ejection heads 1 one-to-one. Alternatively, the liquid ejection device 100 may have one liquid ejection head 1, one drive signal generation unit 2 corresponding to the liquid ejection head 1, and one analysis unit 3 corresponding to the liquid ejection head 1.

[0017] In this embodiment, it is assumed that the liquid ejection device 100 has four liquid ejection heads 1 corresponding to four types of ink: cyan, magenta, yellow, and black. That is, in this embodiment, it is assumed that the liquid ejection device 100 has four liquid ejection heads 1, four drive signal generation units 2, and four analysis units 3. However, for convenience of explanation, the following description may focus on one of the four liquid ejection heads 1 and one drive signal generation unit 2 corresponding to that one liquid ejection head 1, as exemplified in FIG.

[0018] First, before describing the liquid ejection head 1, the control unit 4, the drive signal generating unit 2, and the storage unit 5 will be described.

[0019] The control unit 4 is configured to include one or more CPUs (Central Processing Units). Note that the control unit 4 may be configured to include a programmable logic device such as an FPGA (field-programmable gate array) instead of or in addition to a CPU. Also, for example, the control unit 4 operates in accordance with a control program PG stored in the storage unit 5 to generate signals for controlling the operation of each part of the liquid ejection device 100, such as a print signal SI and a waveform designation signal dCOM.

[0020] Here, the waveform designation signal dCOM is a digital signal that defines the waveform of the drive signal COM. Furthermore, the drive signal COM is an analog signal for driving the discharge section D. In this embodiment, it is assumed that one drive signal COM is output from the drive signal generation unit 2 to the liquid discharge head 1, but multiple drive signals COM may be output from the drive signal generation unit 2 to the liquid discharge head 1. Furthermore, the print signal SI is a digital signal for designating the type of operation of the discharge section D. Specifically, the print signal SI is a signal that designates whether or not to supply the drive signal COM to the discharge section D, thereby designating the type of operation of the discharge section D.

[0021] In this embodiment, the control unit 4 functions as an evaluation control unit 40 by operating in accordance with a control program PG stored in the storage unit 5. Details of the operation of the evaluation control unit 40 are described in FIGS. 8 and 9 . For example, the evaluation control unit 40 evaluates the stability of ink ejection from the nozzle N based on the residual vibration analyzed by the analysis unit 3. Hereinafter, the stability of ink ejection from the nozzle N will also be simply referred to as ejection stability. Ejection stability means, for example, that ink ejection is stable in each ejection operation even when an ejection operation of ejecting ink from the nozzle N is repeated multiple times. In this embodiment, the evaluation control unit 40 evaluates the ejection state of the nozzle N in addition to evaluating the ejection stability. In evaluating the ejection state, the evaluation control unit 40 determines, for example, whether the ejection state of the nozzle N is normal.

[0022] In this manner, in this embodiment, the stability of ink ejection from the nozzles N is evaluated by the evaluation control unit 40. The evaluation control unit 40 is an example of the "control unit."

[0023] The drive signal generation unit 2 includes, for example, a DAC (Digital Analog Converter), and generates the drive signal COM based on the waveform designation signal dCOM supplied from the control unit 4. For example, the drive signal COM generated by the drive signal generation unit 2 includes a waveform defined by the waveform designation signal dCOM. The drive signal generation unit 2 outputs the drive signal COM generated based on the waveform designation signal dCOM to a switching circuit 18 included in the liquid ejection head 1.

[0024] The storage unit 5 includes one or both of a volatile memory such as a RAM (Random Access Memory) and a non-volatile memory such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a PROM (Programmable ROM). The storage unit 5 may be included in the control unit 4.

[0025] The liquid ejection head 1 includes a switching circuit 18, a recording head 10, and a detection circuit 19. The detection circuit 19 is an example of a "detection section."

[0026] The print head 10 has M ejection sections D. In this embodiment, it is assumed that the value M is an even number equal to or greater than 2. Hereinafter, the m-th ejection section D of the M ejection sections D provided in the print head 10 may be referred to as ejection section D[m]. Here, the variable m is a natural number that satisfies "1≦m≦M." Furthermore, hereinafter, when a component or signal of the liquid ejection device 100 corresponds to a ejection section D[m] of the M ejection sections D, the subscript [m] may be added to the symbol representing the component or signal.

[0027] The switching circuit 18 switches whether to supply the drive signal COM to the discharge section D[m] based on the print signal SI. Note that, hereinafter, as shown in FIG. 5 and other figures, the drive signal COM supplied to the discharge section D[m] may be referred to as the individual drive signal Vin[m]. The switching circuit 18 also switches whether to electrically connect the discharge section D[m] to the detection circuit 19 based on the print signal SI. When the discharge section D[m] is electrically connected to the detection circuit 19, for example, a detection signal Vout[m] detected from the discharge section D[m] is supplied to the detection circuit 19 via the switching circuit 18. The detection signal Vout[m] is, for example, an analog signal indicating the waveform of residual vibration, which is vibration remaining in the discharge section D[m] after the discharge section D[m] is driven by the individual drive signal Vin[m]. Specifically, for example, the detection signal Vout[m] indicates the waveform of the residual vibration of the diaphragm 14 after the piezoelectric element PZ[m] is driven. The piezoelectric element PZ and the diaphragm 14 will be described later with reference to FIGS.

[0028] The detection circuit 19 generates the residual vibration signal VR[m] based on the detection signal Vout[m]. For example, the detection circuit 19 amplifies the amplitude of the detection signal Vout[m] or removes noise components contained in the detection signal Vout[m], thereby shaping the detection signal Vout[m] into a waveform suitable for processing in the analysis unit 3. In this way, the residual vibration signal VR[m] is generated. For example, the detection circuit 19 may be configured to include a negative feedback amplifier for amplifying the detection signal Vout[m], a low-pass filter for attenuating high frequency components of the detection signal Vout[m], and a voltage follower for converting impedance and outputting a low-impedance residual vibration signal VR[m].

[0029] For example, the residual vibration signal VR[m] generated based on the detection signal Vout[m] is an analog signal that indicates the waveform of the residual vibration of the diaphragm 14 after the piezoelectric element PZ[m] is driven by the individual drive signal Vin[m]. The detection circuit 19 outputs the residual vibration signal VR[m] generated based on the detection signal Vout[m] to the analysis unit 3. In this way, the detection circuit 19 detects the residual vibration of the diaphragm 14 caused by driving the piezoelectric element PZ[m] based on the detection signal Vout[m].

[0030] The analysis unit 3 includes, for example, an ADC (Analog to Digital Converter) and converts the analog residual vibration signal VR[m] into a digital signal. The analysis unit 3 then analyzes the residual vibration detected by, for example, the detection circuit 19 using the digitally converted residual vibration signal VR[m]. The analysis unit 3 also generates residual vibration information Vinf indicating the analysis results of the residual vibration and outputs the generated residual vibration information Vinf to the control unit 4. The residual vibration information Vinf indicates, for example, the period, amplitude, and phase of the residual vibration. However, the residual vibration information Vinf may indicate only part of the period, amplitude, and phase of the residual vibration. Alternatively, the residual vibration information Vinf may include information other than the period, amplitude, and phase of the residual vibration. The evaluation control unit 40 described above evaluates the ejection state and ejection stability of the nozzle N based on, for example, the residual vibration information Vinf. The analysis unit 3 may be included in the control unit 4. For example, the control unit 4 may function as the analysis unit 3 by operating in accordance with the control program PG stored in the storage unit 5. Also, a part of the analysis unit 3 may be included in the control unit 4. Specifically, an ADC may be provided outside the control unit 4, and the control unit 4 may include a function of analyzing the residual vibration using the residual vibration signal VR converted into a digital signal.

[0031] Furthermore, in this embodiment, as described above, the maintenance process is performed by the maintenance unit 7. For example, the maintenance unit 7 performs the maintenance process under the control of the control unit 4. The maintenance process includes, for example, a flushing process that discharges ink from the ejection section D, a wiping process that wipes off foreign matter such as ink adhering to the vicinity of the nozzle N of the ejection section D with a wiper, and a pumping process that sucks ink from inside the ejection section D with a tube pump or the like.

[0032] The maintenance unit 7 has a discharged ink receiving section for receiving the discharged ink when the ink in the discharge section D is discharged during the flushing process, a wiper for wiping off foreign matter such as ink adhering to the vicinity of the nozzle N of the discharge section D, and a tube pump for sucking ink, air bubbles, etc. from the discharge section D. The discharged ink receiving section, wiper, and tube pump are not shown in the drawings.

[0033] Next, the overall configuration of the liquid ejection device 100 will be described with reference to FIG.

[0034] Fig. 2 is a schematic diagram showing the configuration of the liquid ejection device 100. In Fig. 2, the ink container 60, the medium transport mechanism 8, and the carriage transport mechanism 9 will be mainly described.

[0035] The ink container 60 stores ink. Examples of the ink container 60 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. The type of ink stored in the ink container 60 is not particularly limited and can be any type. As described above, this embodiment assumes that the liquid ejection device 100 has four liquid ejection heads 1, each corresponding to one of four types of ink: cyan, magenta, yellow, and black. Therefore, in this embodiment, the ink container 60 stores the four types of ink: cyan, magenta, yellow, and black. The ink container 60 supplies the stored ink to the liquid ejection head 1.

[0036] The medium conveying mechanism 8 conveys the medium PP in the Y1 direction along the Y axis under the control of the control unit 4. 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 one another. However, the present invention is not limited to this example. It is sufficient that the X axis, Y axis, and Z axis intersect with one another.

[0037] The carriage transport mechanism 9 reciprocates the plurality of liquid ejection heads 1 in the X1 and X2 directions under the control of the control unit 4. As shown in Fig. 2, the carriage transport mechanism 9 has a substantially box-shaped carriage 91 that houses the plurality of liquid ejection heads 1, and an endless belt 92 to which the carriage 91 is fixed. Note that the ink containers 60 may be housed in the carriage 91 together with the liquid ejection heads 1.

[0038] The liquid ejection head 1 is driven by a drive signal COM under the control of a print signal SI, and ejects ink in the Z1 direction from some or all of the multiple nozzles N provided in the liquid ejection head 1. That is, the liquid ejection head 1 ejects ink from some or all of the multiple nozzles N in conjunction with the transport of the medium PP by the medium transport mechanism 8 and the reciprocating movement of the liquid ejection head 1 by the carriage transport mechanism 9, and forms a desired image on the surface of the medium PP by causing the ejected ink to land on the surface of the medium PP. In this embodiment, as described above, the Z1 direction is the direction in which ink is ejected from the nozzles N.

[0039] Next, the general structure of the liquid ejection head 1 will be described with reference to FIGS.

[0040] FIG. 3 is an exploded perspective view of the liquid ejection head 1. FIG. 4 is a cross-sectional view taken along line III-III in FIG. 3. The cross section taken along line III-III is parallel to the XZ plane and passes through inlets HL1 and HL2, which will be described later. In FIGS. 3 and 4, the numerals "1" and "2" are added to the end of the reference numerals of the nozzle rows Ln to distinguish between the two nozzle rows Ln, which will be described later. In addition, in FIGS. 3 and 4, for ease of explanation, the numeral "1" is added to the end of the reference numeral of the nozzle N included in the nozzle row Ln1, and the numeral "2" is added to the end of the reference numeral of the nozzle N included in the nozzle row Ln2.

[0041] 3 and 4, the liquid ejection head 1 has a nozzle substrate 11, compliance sheets CS1 and CS2, a communication plate 12, a pressure chamber substrate 13, a vibration plate 14, a sealing substrate 15, a flow path forming substrate 16, and a wiring board 17 on which electronic components EC are mounted. The electronic components EC include, for example, electrical circuits such as a switching circuit 18 and a detection circuit 19. For example, the recording head 10 is electrically connected to the switching circuit 18, the detection circuit 19, etc. via the wiring board 17.

[0042] As shown in FIG. 3, the recording head 10 includes, for example, a nozzle substrate 11, compliance sheets CS1 and CS2, a communication plate 12, a pressure chamber substrate 13, a vibration plate 14, a sealing substrate 15, and a flow path forming substrate 16.

[0043] The nozzle substrate 11 is a plate-like member that is elongated in the Y-axis direction and extends approximately parallel to the XY plane. Here, "approximately parallel" is a concept that includes not only completely parallel but also a case where it can be considered to be parallel when an error is taken into consideration. In this embodiment, "approximately parallel" is a concept that includes a case where it can be considered to be parallel when an error of about 10% is taken into consideration. Like "approximately parallel," the term "approximately perpendicular," which will be described later, is a concept that includes not only completely perpendicular but also perpendicular when an error is taken into consideration. The nozzle substrate 11 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing techniques such as etching, for example, but known materials and manufacturing methods may be arbitrarily adopted for manufacturing the nozzle substrate 11.

[0044] M nozzles N are formed on the nozzle substrate 11. Here, the nozzles N are through-holes formed in the nozzle substrate 11. In this embodiment, it is assumed that the multiple nozzles N formed on the nozzle substrate 11 include multiple nozzles N1 arranged to extend in the Y-axis direction and multiple nozzles N2 arranged to extend in the Y-axis direction at positions in the X2 direction as viewed from the multiple nozzles N1. Hereinafter, the multiple nozzles N1 arranged to extend in the Y-axis direction will be referred to as a nozzle row Ln1, and the multiple nozzles N2 arranged to extend in the Y-axis direction will be referred to as a nozzle row Ln2. For example, the number of nozzles N included in each of the nozzle rows LN1 and Ln2 is half the value M. Hereinafter, the nozzle row Ln1 and the nozzle row Ln2 may be collectively referred to as the nozzle row Ln. Also, in Figures 3 and 4, to make the explanation easier to understand, the numeral "1" is added to the end of the reference numeral of the component of the liquid ejection head 1 that corresponds to nozzle row Ln1, and the numeral "2" is added to the end of the reference numeral of the component that corresponds to nozzle row Ln2.

[0045] 3 and 4, a communicating plate 12 is provided at a position in the Z2 direction as viewed from the nozzle substrate 11. The communicating plate 12 is a plate-shaped member that is long in the Y-axis direction and extends approximately parallel to the XY plane. The communicating plate 12 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology, but the communicating plate 12 may be manufactured using any known material and method.

[0046] Ink flow paths are formed in the communicating plate 12. Specifically, the communicating plate 12 is formed with one supply flow path BA1 extending in the Y-axis direction and one supply flow path BA2 extending in the Y-axis direction at a position in the X2 direction as viewed from the supply flow path BA1. The communicating plate 12 also is formed with a plurality of connection flow paths BK1 corresponding to the plurality of nozzles N1, a plurality of connection flow paths BK2 corresponding to the plurality of nozzles N2, a plurality of communication flow paths BR1 corresponding to the plurality of nozzles N1, and a plurality of communication flow paths BR2 corresponding to the plurality of nozzles N2.

[0047] As shown in FIG. 4, the connection flow path BK1 communicates with the supply flow path BA1 and is provided so as to extend in the Z-axis direction at a position in the X2 direction as viewed from the supply flow path BA1. The communication flow path BR1 is provided so as to extend in the Z-axis direction at a position in the X2 direction as viewed from the connection flow path BK1. The communication flow path BR1 communicates with the nozzle N1 corresponding to the communication flow path BR1. The connection flow path BK2 communicates with the supply flow path BA2 and is provided so as to extend in the Z-axis direction at a position in the X1 direction as viewed from the supply flow path BA2. The communication flow path BR2 is provided so as to extend in the Z-axis direction at a position in the X1 direction as viewed from the connection flow path BK2 and at a position in the X2 direction as viewed from the communication flow path BR1. The communication flow path BR2 communicates with the nozzle N2 corresponding to the communication flow path BR2.

[0048] The supply flow paths BA1 and BA2 are also referred to as supply flow paths BA without any particular distinction, the connection flow paths BK1 and BK2 are also referred to as connection flow paths BK without any particular distinction, and the communicating flow paths BR1 and BR2 are also referred to as communicating flow paths BR without any particular distinction.

[0049] 3 and 4, a pressure chamber substrate 13 is provided at a position in the Z2 direction as viewed from the communication plate 12. The pressure chamber substrate 13 is a plate-shaped member that is long in the Y-axis direction and extends approximately parallel to the XY plane. The pressure chamber substrate 13 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology, but the pressure chamber substrate 13 may be manufactured using any known material and manufacturing method.

[0050] Ink flow paths are formed in the pressure chamber substrate 13. Specifically, the pressure chamber substrate 13 is formed with a plurality of pressure chambers CV1 corresponding to the plurality of nozzles N1 and a plurality of pressure chambers CV2 corresponding to the plurality of nozzles N2. Of these, the pressure chamber CV1 is provided so as to connect the X2-direction end of the connection flow path BK1 and the X1-direction end of the communication flow path BR1 and extend in the X-axis direction when viewed in the Z-axis direction. The pressure chamber CV2 is provided so as to connect the X1-direction end of the connection flow path BK2 and the X2-direction end of the communication flow path BR2 when viewed in the Z-axis direction and extend in the X-axis direction. The pressure chambers CV1 and CV2 are also referred to as pressure chambers CV without any particular distinction being made.

[0051] As shown in FIGS. 3 and 4 , a diaphragm 14 is provided at a position in the Z2 direction as viewed from the pressure chamber substrate 13. The diaphragm 14 is a plate-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and is capable of elastically vibrating. In this embodiment, the diaphragm 14 has, for example, an elastic layer made of silicon oxide and an insulating layer made of zirconium oxide provided at a position in the Z2 direction as viewed from the elastic layer. That is, in this embodiment, the Z2-direction surface of the diaphragm 14 is formed of a non-conductive material. Here, the first-direction surface of element A is a surface of element A that is substantially perpendicular to the first direction and is the surface that is visible when element A is viewed from the first direction to the second direction. The second direction is the direction opposite to the first direction. Note that the elastic layer of the diaphragm 14 is not limited to an elastic layer made of silicon oxide. Similarly, the insulating layer of the diaphragm 14 is not limited to an insulating layer made of zirconium oxide.

[0052] 3 and 4, a plurality of piezoelectric elements PZ1 corresponding to the plurality of pressure chambers CV1 and a plurality of piezoelectric elements PZ2 corresponding to the plurality of pressure chambers CV2 are provided in positions in the Z2 direction as viewed from the vibration plate 14. Note that the piezoelectric elements PZ1 and PZ2 are also referred to as piezoelectric elements PZ without any particular distinction. The piezoelectric elements PZ are driven by the supply of a drive signal COM.

[0053] Although not shown in FIGS. 3 and 4 , the piezoelectric element PZ includes a common electrode Zc to which a predetermined bias potential VBS is supplied, an individual electrode Za to which an individual drive signal Vin is supplied, and a piezoelectric body Zb disposed between the individual electrode Za and the common electrode Zc, as shown in FIG. 5 . For example, the individual electrode Za, the piezoelectric body Zb, and the common electrode Zc are disposed in this order on the Z2-direction surface of the diaphragm 14 along the Z2 direction. Here, the expression “element B is formed on the surface of element A” in this specification does not intend to limit the configuration to one in which element A and element B are in direct contact with each other. In other words, even if element C is formed on the surface of element A and element B is formed on the surface of element C, the concept of “element B is formed on the surface of element A” is encompassed as long as at least a portion of element A and element B overlap in a planar view. Note that in this embodiment, the common electrode Zc is a so-called upper electrode and the individual electrode Za is a so-called lower electrode. However, the common electrode Zc may be a lower electrode and the individual electrode Za may be an upper electrode.

[0054] The piezoelectric element PZ is a passive element that deforms in response to changes in the potential of the drive signal COM supplied to the individual electrode Za as the individual drive signal Vin. In other words, the piezoelectric element PZ is an example of an energy conversion element that converts the electrical energy of the drive signal COM into kinetic energy. Specifically, the piezoelectric element PZ is driven and deforms in response to changes in the potential of the drive signal COM.

[0055] As shown in FIGS. 3 and 4, a piezoelectric element PZ is provided on the Z2-direction surface of the vibration plate 14, and the vibration plate 14 vibrates in response to the deformation of the piezoelectric element PZ. That is, the vibration plate 14 vibrates when the piezoelectric element PZ is driven. When the vibration plate 14 vibrates, the pressure in the pressure chamber CV fluctuates. Then, as the pressure in the pressure chamber CV fluctuates, ink filled in the pressure chamber CV is ejected from the nozzle N via the communication channel BR. In this way, the pressure chamber CV is filled with ink, and pressure for ejecting ink from the nozzle N is applied by the vibration of the vibration plate 14. Furthermore, the vibration remaining in the ejection portion D[m] described in FIG. 1 can also be considered, for example, as vibration remaining in the ink in the pressure chamber CV of the ejection portion D. Therefore, the residual vibration of the vibration plate 14, i.e., the residual vibration of the ejection portion D[m], indicates the behavior of the ink in the pressure chamber CV of the ejection portion D.

[0056] 3 and 4, a sealing substrate 15 for protecting the plurality of piezoelectric elements PZ1 and the plurality of piezoelectric elements PZ2 is provided at a position in the Z2 direction as viewed from the pressure chamber substrate 13. The sealing substrate 15 is a plate-like member that is elongated in the Y-axis direction and extends approximately parallel to the XY plane. The sealing substrate 15 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology, but the sealing substrate 15 may be manufactured using any known material and manufacturing method.

[0057] 4, the surface of the sealing substrate 15 in the Z1 direction is provided with recesses for covering the plurality of piezoelectric elements PZ1 and recesses for covering the plurality of piezoelectric elements PZ2. Hereinafter, the sealed space covering the plurality of piezoelectric elements PZ1 and formed between the vibration plate 14 and the sealing substrate 15 will be referred to as the sealed space SP1, and the sealed space covering the plurality of piezoelectric elements PZ2 and formed between the vibration plate 14 and the sealing substrate 15 will be referred to as the sealed space SP2. The sealed spaces SP1 and SP2 will also be referred to as the sealed space SP without any particular distinction. The sealed space SP is a space for sealing the piezoelectric elements PZ and preventing the piezoelectric elements PZ from being altered by the influence of moisture, etc.

[0058] A through hole 15h is provided in the sealing substrate 15. When the sealing substrate 15 is viewed in the Z1 direction, the through hole 15h is located between the sealed space SP1 and the sealed space SP2, and is a hole that penetrates from the surface of the sealing substrate 15 in the Z1 direction to the surface of the sealing substrate 15 in the Z2 direction. The wiring substrate 17 is inserted into the through hole 15h.

[0059] 3 and 4, a flow path forming substrate 16 is provided at a position in the Z2 direction as viewed from the communication plate 12. The flow path forming substrate 16 is a plate-like member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane. The flow path forming substrate 16 is formed, for example, by injection molding of a resin material, but the flow path forming substrate 16 may be manufactured using any known material and method.

[0060] As shown in FIG. 4, ink flow paths are formed in the flow path forming substrate 16. Specifically, one supply flow path BB1 and one supply flow path BB2 are formed in the flow path forming substrate 16. Of these, supply flow path BB1 communicates with supply flow path BA1 and is provided so as to extend in the Y-axis direction at a position in the Z2 direction as viewed from supply flow path BA1. Supply flow path BB2 communicates with supply flow path BA2 and is provided so as to extend in the Y-axis direction at a position in the Z2 direction as viewed from supply flow path BA2 and at a position in the X2 direction as viewed from supply flow path BB1. Note that supply flow paths BB1 and BB2 are also referred to as supply flow paths BB without any particular distinction being made.

[0061] The flow channel forming substrate 16 is provided with an inlet HL1 that communicates with the supply channel BB1 and an inlet HL2 that communicates with the supply channel BB2. Ink is supplied to the supply channel BB1 from the ink container 60 via the inlet HL1. The ink supplied to the supply channel BB1 from the ink container 60 via the inlet HL1 flows into the supply channel BA1. Some of the ink that flows into the supply channel BA1 passes through the connecting channel BK1 and fills the pressure chamber CV1. When the piezoelectric element PZ1 is driven by the drive signal COM, some of the ink that has filled the pressure chamber CV1 is ejected from the nozzle N1 via the communicating channel BR1.

[0062] Furthermore, ink is supplied to supply flow path BB2 from the ink container 60 via inlet HL2. The ink supplied from the ink container 60 to supply flow path BB2 via inlet HL2 flows into supply flow path BA2. Some of the ink that flows into supply flow path BA2 passes through connecting flow path BK2 and fills pressure chamber CV2. When piezoelectric element PZ2 is driven by drive signal COM, some of the ink that has filled pressure chamber CV2 is ejected from nozzle N2 via communicating flow path BR2.

[0063] A through hole 16h is provided in the flow path forming substrate 16. When the flow path forming substrate 16 is viewed in the Z1 direction, the through hole 16h is located between the supply flow path BB1 and the supply flow path BB2, and is a hole that penetrates from the surface of the flow path forming substrate 16 in the Z1 direction to the surface of the flow path forming substrate 16 in the Z2 direction. The wiring substrate 17 is inserted into the through hole 16h.

[0064] 3 and 4, a wiring board 17 is mounted on the Z2 direction surface of the diaphragm 14. The wiring board 17 is a component for electrically connecting the liquid ejection head 1 to the control unit 4. For example, a flexible wiring board such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably used as the wiring board 17. As described above, electronic components EC including the switching circuit 18 and the detection circuit 19 are mounted on the wiring board 17.

[0065] 3 and 4, a compliance sheet CS1 is provided in a position in the Z1 direction as viewed from the communicating plate 12 so as to block the supply flow path BA1 and the connecting flow path BK1, and a compliance sheet CS2 is provided so as to block the supply flow path BA2 and the connecting flow path BK2. The compliance sheets CS1 and CS2 are also referred to as the compliance sheet CS without any particular distinction. The compliance sheet CS is a plate-like member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane. The compliance sheet CS is made of an elastic material and absorbs pressure fluctuations of the ink in the supply flow path BA and the connecting flow path BK.

[0066] 4, the ejection section D1 has a piezoelectric element PZ1, a pressure chamber CV1, a nozzle N1 communicating with the pressure chamber CV1, and a portion of the vibration plate 14 that contacts the piezoelectric element PZ1. Similarly, the ejection section D2 has a piezoelectric element PZ2, a pressure chamber CV2, a nozzle N2 communicating with the pressure chamber CV2, and a portion of the vibration plate 14 that contacts the piezoelectric element PZ2. The ejection sections D1 and D2 are also referred to as ejection section D without any particular distinction. In the following, the second element of the first element and second element included in one ejection section D will also be referred to as the second element corresponding to the first element. Specifically, for example, the piezoelectric element PZ included in the ejection section D that has one nozzle N will also be referred to as the piezoelectric element PZ corresponding to the one nozzle N.

[0067] Although not shown, the liquid ejection head 1 also has a cap for sealing the nozzle surface, which is the surface in the Z1 direction of the nozzle substrate 11. The cap seals the nozzle surface of the nozzle substrate 11 on which the nozzles N are formed, during periods when ink is not ejected from the nozzles N.

[0068] Next, an overview of the liquid ejection head 1 will be described with reference to FIG.

[0069] FIG. 5 is a block diagram showing an example of the configuration of the liquid ejection head 1. As shown in FIG.

[0070] 1, the liquid ejection head 1 has a recording head 10, a switching circuit 18, and a detection circuit 19. The liquid ejection head 1 also has a wiring La to which a drive signal COM is supplied from the drive signal generating unit 2, and a wiring Ls that supplies a detection signal Vout to the detection circuit 19. The liquid ejection head 1 also has a wiring Li[m] that supplies an individual drive signal Vin[m] to the ejection section D[m], and a wiring Ld that is supplied with a bias potential VBS. In this embodiment, it is assumed that the drive signal COM supplied to the wiring La is the drive signal COM that causes ink to be ejected from the nozzle N.

[0071] The switching circuit 18 has M switches SWa[1] to SWa[M] that correspond one-to-one to the M discharge units D[1] to D[M], and M switches SWs[1] to SWs[M] that correspond one-to-one to the M discharge units D[1] to D[M].

[0072] The switching circuit 18 also includes a connection state designation circuit CSC. The connection state designation circuit CSC designates the connection state of each of the M switches SWa and the M switches SWs. For example, the connection state designation circuit CSC generates connection state designation signals Qa[m] and Qs[m] based on at least a portion of the print signal SI and the latch signal LAT supplied from the control unit 4.

[0073] For example, the connection state designation signal Qa[m] is a signal that designates whether the switch SWa[m] is on or off, and the connection state designation signal Qs[m] is a signal that designates whether the switch SWs[m] is on or off.

[0074] The switch SWa[m] switches between conduction and non-conduction between the wiring La and the individual electrode Za[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] based on the connection state designation signal Qa[m]. That is, the switch SWa[m] switches between conduction and non-conduction between the wiring La and the wiring Li[m] connected to the individual electrode Za[m] based on the connection state designation signal Qa[m]. In this embodiment, the switch SWa[m] is turned on when the connection state designation signal Qa[m] is high level and turned off when the connection state designation signal Qa[m] is low level. When the switch SWa[m] is on, the drive signal COM supplied to the wiring La is supplied as an individual drive signal Vin[m] to the individual electrode Za[m] of the discharge section D[m] via the wiring Li[m]. That is, the individual drive signal Vin[m] is the drive signal COM supplied to the piezoelectric element PZ[m] of the discharge section D[m] via the switch SWa[m].

[0075] The switch SWs[m] switches between electrical continuity and non-conduction between the wiring Ls and the individual electrode Za[m] of the piezoelectric element PZ[m] provided in the discharge portion D[m] based on the connection state designation signal Qs[m]. That is, the switch SWs[m] switches between electrical continuity and non-conduction between the wiring Ls and the wiring Li[m] connected to the individual electrode Za[m] based on the connection state designation signal Qs[m]. In this embodiment, the switch SWs[m] is turned on when the connection state designation signal Qs[m] is high level and turned off when the connection state designation signal Qs[m] is low level.

[0076] For example, the connection state designation signal Qs[m] becomes high level when residual vibration of a discharge section D[m] is detected. Hereinafter, the discharge section D from which residual vibration is detected may be referred to as the discharge section D of the detection target. Also, below, the nozzle N of the discharge section D of the detection target may be referred to as the nozzle N of the detection target. When the switch SWs[m] is turned on, a detection signal Vout[m] indicating the potential of the individual electrode Za[m] of the piezoelectric element PZ[m] of the discharge section D[m] of the detection target is supplied to the detection circuit 19 via the wiring Li[m] and the wiring Ls. The detection circuit 19 generates a residual vibration signal VR[m] based on the detection signal Vout[m].

[0077] As described above, the residual vibration signal VR[m] is used to evaluate the ejection state of the nozzle N and to evaluate the ejection stability. Specifically, in evaluating the ejection state of the nozzle N, for example, the residual vibration signal VR[m] is used, which indicates the residual vibration of the diaphragm 14 resulting from performing only one ejection drive in which the piezoelectric element PZ is driven by the drive signal COM that ejects ink from the nozzle N. For example, if the residual vibration of the diaphragm 14 resulting from one ejection drive can be considered to match the residual vibration under normal conditions that is assumed in advance, the ejection state of the nozzle N is determined to be normal.

[0078] However, even if the ejection state of nozzle N is determined to be normal, if the ejection operation is performed multiple times in succession, the meniscus vibration increases, and there is a risk that the ink ejection will become unstable due to the entrainment of air bubbles caused by the meniscus vibration. For this reason, a method of evaluating the ejection stability based on the residual vibration signal VR[m] indicating the residual vibration of the diaphragm 14 resulting from a single ejection drive may not be able to accurately evaluate the ejection stability. Therefore, in this embodiment, the residual vibration signal VR[m] indicating the residual vibration of the diaphragm 14 resulting from multiple executions of the ejection drive is used to evaluate the ejection stability. As a result, in this embodiment, the ejection stability can be accurately evaluated.

[0079] Next, the operation of the liquid ejection device 100 in the unit period TU will be described with reference to FIG.

[0080] FIG. 6 is a timing chart showing an example of the operation of the liquid ejection device 100 in a unit period TU. In this embodiment, when the liquid ejection device 100 executes a printing process, a printing process period including one or more unit periods TU is set as the operating period of the liquid ejection device 100. A unit period TU is, for example, the drive cycle of M ejection sections D. For example, the liquid ejection device 100 according to this embodiment can drive each ejection section D for the printing process in each unit period TU. Furthermore, the liquid ejection device 100 according to this embodiment can drive the ejection section D to be detected and detect the detection signal Vout[m] from the ejection section D to be detected in each unit period TU.

[0081] The control unit 4 outputs a latch signal LAT having a pulse PlsL, thereby defining a unit period TU as the period from the rising edge of one pulse PlsL to the rising edge of the next pulse PlsL.

[0082] The print signal SI includes, for example, M individual designation signals Sd[1] to Sd[M] that correspond one-to-one to the M discharge sections D[1] to D[M]. The individual designation signal Sd[m] designates the driving mode of the discharge section D[m] in each unit period TU when the liquid discharger 100 executes a printing process.

[0083] Prior to each unit period TU during which printing is performed, the control unit 4 supplies a print signal SI, including individual designation signals Sd[1] to Sd[M], to the connection state designation circuit CSC in synchronization with the clock signal CL. Then, during that unit period TU, the connection state designation circuit CSC generates connection state designation signals Qa[m] and Qs[m] based on the individual designation signal Sd[m].

[0084] For example, in a unit period TP during which the printing process is executed, a discharge unit D[m] is designated by the individual designation signal Sd[m] as either a discharge unit D that forms dots, a discharge unit D that does not form dots, or a discharge unit D that is the detection target. A discharge unit D that forms dots is a discharge unit D that is driven so that the piezoelectric element PZ of that discharge unit D is ejected from the nozzle N of that discharge unit D. In other words, it is a discharge unit D that is the target of ejection drive that drives the piezoelectric element PZ with a drive signal COM that ejects ink from the nozzle N. Furthermore, a discharge unit D that does not form dots is a discharge unit D that is driven so that the piezoelectric element PZ of that discharge unit D is not ejected from the nozzle N of that discharge unit D.

[0085] First, we will explain the operation of the connection state specification circuit CSC and other components when the drive mode of the discharge unit D that forms dots is specified by the individual specification signal Sd[m]. When the drive mode of the discharge unit D that forms dots is specified by the individual specification signal Sd[m], for example, the connection state specification circuit CSC sets the connection state specification signal Qa[m] to a high level and the connection state specification signal Qs[m] to a low level during the unit period TU. This causes the drive signal COM to be supplied from the drive signal generation unit 2 to the discharge unit D that forms dots.

[0086] For example, the drive signal generating unit 2 outputs a drive signal COM having a pulse PA. The pulse PA is, for example, a pulse that causes ink to be ejected from the nozzle N. The pulse PA has a waveform in which the potential of the drive signal COM changes from a potential V0 (intermediate potential, reference potential), through a potential VLa (minimum potential, expansion potential) lower than the potential V0, and a potential VHa (maximum potential, contraction potential) higher than the potential V0, before returning to the potential V0. The potential V0 is the potential at the start and end of the pulse PA, and is the reference potential of the drive signal COM.

[0087] For example, the pulse PA has a waveform element Pa1 whose potential changes from potential V0 to potential VLa, a waveform element Pa2 whose potential is maintained at the potential VLa at the end of the waveform element Pa1, and a waveform element Pa3 whose potential changes from potential VLa to potential VHa. The pulse PA further includes a waveform element Pa4 whose potential is maintained at the potential VHa at the end of the waveform element Pa3, and a waveform element Pa5 whose potential changes from potential VHa to potential V0.

[0088] The waveform elements Pa1 and Pa5 are expansion elements for displacing the piezoelectric body Zb in the Z2 direction. In the expansion elements, the potential of the drive signal COM changes to drive the piezoelectric element PZ so as to expand the volume of the pressure chamber CV. Therefore, in the waveform elements Pa1 and Pa5, the potential of the drive signal COM changes so as to expand the volume of the pressure chamber CV. When the volume of the pressure chamber CV expands, the surface of the ink in the nozzle N is pulled in the Z2 direction, which is the opposite direction to the ejection direction. Hereinafter, pulling the surface of the ink in the nozzle N in the direction opposite to the ejection direction may be referred to as "pull."

[0089] Furthermore, the waveform element Pa3 is a contraction element for displacing the piezoelectric body Zb in the Z1 direction. In the contraction element, the potential of the drive signal COM changes to drive the piezoelectric element PZ so as to contract the volume of the pressure chamber CV. Therefore, in the waveform element Pa3, the potential of the drive signal COM changes so as to contract the volume of the pressure chamber CV. When the volume of the pressure chamber CV contracts, the surface of the ink in the nozzle N is pushed in the Z1 direction, which is the ejection direction. Hereinafter, pushing the surface of the ink in the nozzle N in the ejection direction may be referred to as a push.

[0090] Furthermore, waveform elements Pa2 and Pa4 are maintaining elements for maintaining the position of the piezoelectric body Zb in the Z-axis direction. For example, waveform element Pa2 maintains the potential of the drive signal COM in order to drive the piezoelectric element PZ so as to maintain the volume of the pressure chamber CV expanded by waveform element Pa1. For example, waveform element Pa4 maintains the potential of the drive signal COM in order to drive the piezoelectric element PZ so as to maintain the volume of the pressure chamber CV contracted by waveform element Pa3.

[0091] In this way, the pulse PA has a so-called pull-push-pull waveform. However, the waveform of the drive signal COM that causes ink to be ejected from the nozzle N is not limited to the pull-push-pull waveform.

[0092] The pulse PA is determined so that a predetermined amount of ink is ejected from the ejection section D[m] when an individual drive signal Vin[m] having the pulse PA is supplied to the ejection section D[m]. Note that in this embodiment, it is assumed that when the potential of the individual drive signal Vin[m] is high, the volume of the pressure chamber CV of the ejection section D[m] is smaller than when the potential is low. Therefore, when the ejection section D[m] is driven by the individual drive signal Vin[m] having the pulse PA, the ink in the ejection section D[m] is ejected from the nozzle N by the waveform element Pa3, in which the potential of the individual drive signal Vin[m] changes from low to high.

[0093] For example, the waveform elements Pa1, Pa2, Pa3, Pa4, and Pa5 included in the pulse PA are determined based on the ink ejection characteristics and ejection stability of the ejection unit D. The ink ejection characteristics include, for example, the amount of ink ejected as an ink droplet and the ejection speed of the ejected ink droplet. In this embodiment, it is assumed that, among the waveform elements Pa1, Pa2, Pa3, Pa4, and Pa5 determined based on the ink ejection characteristics, the length TA of the waveform element Pa4 and the length TB of the waveform element Pa5 are adjusted to improve ejection stability. Furthermore, it is assumed that the start timing of the waveform element Pa4 does not change before and after adjusting the length TA, and the end timing of the waveform element Pa5 does not change before and after adjusting the length TB. In other words, in this embodiment, the sum of the length TA of the waveform element Pa4 and the length TB of the waveform element Pa5 does not change before and after adjustment.

[0094] Therefore, for example, when the length TB is short, the potential change per unit time of the waveform element Pa5, i.e., the slope of the waveform element Pa5, is larger than when the length TB is long. When the slope of the waveform element Pa5 is large, the vibration-damping ability to attenuate the residual vibration of the ejection section D is higher than when the slope of the waveform element Pa5 is small. Therefore, when the slope of the waveform element Pa5 is large, the vibration-damping ability to attenuate the vibration of the meniscus is higher than when the slope of the waveform element Pa5 is small, which tends to improve ejection stability. On the other hand, if the length TB is increased, it is necessary to either lengthen the entire pulse PA or shorten any of the waveform elements Pa1, Pa2, Pa3, and Pa4. The former may lead to a decrease in the drive frequency, and the lengths of the waveform elements Pa1, Pa2, and Pa3 of the latter may affect the ejection itself. Therefore, in this embodiment, when the length TB of the waveform element Pa5 is increased, the length TA of the waveform element Pa4 is shortened instead. However, the method for determining the waveform of the pulse PA to improve ejection stability is not limited to adjusting the length TA of the waveform element Pa4 or the length T5 of the waveform element Pa5. The waveform elements Pa1, Pa2, Pa3, Pa4, and Pa5 included in the pulse PA may be adjusted as appropriate to improve ejection stability within a range in which the ink ejection characteristics become the desired ejection characteristics.

[0095] Next, we will explain the operation of the connection state designation circuit CSC and other components when the individual designation signal Sd[m] designates the drive mode of a discharge unit D that does not form dots. When the individual designation signal Sd[m] designates the drive mode of a discharge unit D that does not form dots, for example, the connection state designation circuit CSC sets the connection state designation signals Qa[m] and Qs[m] to a low level during the unit period TU. As a result, if no leakage current occurs, the potential of the individual electrode Za of the piezoelectric element PZ of the discharge unit D that does not form dots is maintained at the potential before the connection state designation signal Qa[m] was set to a low level, for example, potential V0.

[0096] Next, the operation of the connection state specification circuit CSC and other circuits when the drive mode of the ejection unit D to be detected is specified by the individual specification signal Sd[m] will be described. Hereinafter, the operation of the connection state specification circuit CSC and other circuits when the drive mode of the ejection unit D to be detected is specified by the individual specification signal Sd[m] will be described using the case of evaluating ejection stability as an example. Hereinafter, the unit period TU in which residual vibrations for evaluating ejection stability are detected may be referred to as the detection unit period TU. When evaluating ejection stability, for example, the ejection unit D to be detected operates as an ejection unit D that forms dots in each of K unit periods TU from the unit period TU K before the detection unit period TU to the unit period TU immediately before the detection unit period TU. That is, the piezoelectric element PZ of the ejection unit D to be detected is driven by a drive signal COM that ejects ink from the nozzle N in each of K consecutive unit periods TU before the detection unit period TU. Note that, in this embodiment, the value K is assumed to be a natural number of 10 or greater, but the value K is not particularly limited as long as it is a natural number of 2 or greater.

[0097] For example, when the drive mode of the discharge section D to be detected is specified by the individual specification signal Sd[m], the connection state specification circuit CSC sets the connection state specification signal Qs[m] to a high level during the detection unit period TU, and also sets the connection state specification signal Qa[m] to a low level during the detection unit period TU.

[0098] In this case, the piezoelectric element PZ[m] of the discharge section D[m] to be detected is driven by the drive signal COM during each of the K consecutive unit periods TU before the detection unit period TU. As a result, the piezoelectric element PZ[m] is displaced by the pulse PA of the drive signal COM during each of the K consecutive unit periods TU before the detection unit period TU. As a result, vibrations occur in the discharge section D[m] to be detected before the detection unit period TU. The vibrations that occurred before the detection unit period TU remain during the detection unit period TU. During the detection unit period TU, the potential of the individual electrode Za[m] of the piezoelectric element PZ[m] of the discharge section D[m] to be detected changes depending on the residual vibrations occurring in the discharge section D[m]. That is, during the detection unit period TU, the potential of the individual electrode Za of the piezoelectric element PZ of the discharge section D to be detected becomes a potential corresponding to the electromotive force of the piezoelectric element PZ caused by the residual vibrations occurring in the discharge section D to be detected. The potential of the individual electrode Za is detected as a detection signal Vout during a unit period TU for detection.

[0099] The connection state designation circuit CSC may set the connection state designation signal Qs[m] to a high level during the first half of the detection unit period TU, and set the connection state designation signal Qs[m] to a low level during the second half of the detection unit period TU. The connection state designation signals Qa and Qs corresponding to the discharge units D other than the discharge unit D[m] to be detected are set to a low level during the detection unit period TU.

[0100] In this manner, in this embodiment, the stability of ejection is evaluated by using, for example, the residual vibration signal VR[m] that indicates the residual vibration of the diaphragm 14 resulting from continuous execution of ejection driving, which drives the piezoelectric element PZ with the drive signal COM that ejects ink from the nozzle N. Continuous execution of ejection driving means, for example, that ejection driving is performed in each of a plurality of continuous unit periods TU.

[0101] The operation of the liquid ejection device 100 is not limited to the example shown in FIG. 6 . For example, FIG. 6 illustrates a drive signal COM including one pulse PA that ejects ink from the nozzle N, but the present invention is not limited to this embodiment. For example, the drive signal COM may include multiple pulses that eject ink from the nozzle N to form dots of different sizes. Also, for example, FIG. 6 illustrates a case in which there is one drive signal COM that ejects ink from the nozzle N, but the present invention is not limited to this embodiment. For example, multiple drive signals COM corresponding to the sizes of the dots may be used as the drive signal COM that ejects ink from the nozzle N. Also, the multiple drive signals COM may include one or both of a drive signal COM having a micro-vibration waveform that prevents ink from thickening and a drive signal COM having a micro-vibration waveform that generates residual vibrations for evaluating the ejection state.

[0102] Next, the operation of the analysis unit 3 will be described with reference to FIG.

[0103] Fig. 7 is a diagram showing an example of the waveform of the residual vibration signal VR. Fig. 7 schematically shows an example of the waveform of the residual vibration signal VR indicating the residual vibration detected in a detection unit period TU. The vertical axis of the diagram represents the potential of the residual vibration signal VR, and the horizontal axis represents time.

[0104] Furthermore, potential VC0 indicates the reference potential of residual vibration signal VR. For example, potential VC0 may be the potential of residual vibration signal VR when the residual vibration of diaphragm 14 has attenuated and subsided, or may be an intermediate potential between the peak potential where the waveform of residual vibration signal VR becomes a crest and the peak potential where the waveform of residual vibration signal VR becomes a trough. The peak where the waveform of residual vibration signal VR becomes a crest is the peak where the potential of residual vibration signal VR becomes a maximum value, and the peak where the waveform of residual vibration signal VR becomes a trough is the peak where the potential of residual vibration signal VR becomes a minimum value.

[0105] Each of the residual vibration signals VRca and VRcb is a residual vibration signal VR indicating the residual vibration of the diaphragm 14 resulting from, for example, ten consecutive ejection drives. The residual vibration signal VRca is an example of the residual vibration signal VR when ejection is stable, and the residual vibration signal VRcb is an example of the residual vibration signal VR when ejection is unstable. Hereinafter, the residual vibration signals VRca and VRcb will also be referred to as the residual vibration signal VRc without any particular distinction. For example, the residual vibration signal VRs is a residual vibration signal VR indicating the residual vibration of the diaphragm 14 resulting from only one ejection drive. The residual vibration signal VRs is used, for example, to calculate a threshold value to be compared with the residual vibration signal VRc. The waveforms shown in FIG. 7 are waveforms for explaining the operation of the analysis unit 3, and do not accurately represent the relationship between the residual vibration of the diaphragm 14 resulting from ten consecutive ejection drives and the residual vibration of the diaphragm 14 resulting from only one ejection drive.

[0106] As described above, the residual vibration signal VR indicates a waveform corresponding to the residual vibration occurring in the ejection portion D to be detected, i.e., the residual vibration of the diaphragm 14. Specifically, the residual vibration signal VR indicates an amplitude corresponding to the amplitude of the residual vibration of the diaphragm 14, a period corresponding to the period of the residual vibration of the diaphragm 14, and a phase corresponding to the phase of the residual vibration of the diaphragm 14.

[0107] 7, for example, the analysis unit 3 identifies the amplitude λS1 of the first peak of the multiple peaks at which the potential of the residual vibration signal VRs becomes a local maximum or minimum value as the amplitude of the first peak of the residual vibration of the diaphragm 14 resulting from executing the ejection drive only once. The analysis unit 3 also identifies the amplitude λS2 of the second peak and the amplitude λS3 of the third peak of the residual vibration signal VRs as the amplitude of the second peak and the amplitude λS3 of the third peak of the residual vibration of the diaphragm 14 resulting from executing the ejection drive only once, respectively. Hereinafter, the amplitudes λS1, λS2, and λS3 of the residual vibration signal VRs may be collectively referred to as amplitude λS.

[0108] Similarly, the analysis unit 3 identifies the amplitude λC1 of the first peak of the residual vibration signal VRc as the amplitude of the first peak of the residual vibration of the diaphragm 14 resulting from ten consecutive executions of the ejection drive. The analysis unit 3 also identifies the amplitude λC2 of the second peak and the amplitude λC3 of the third peak of the residual vibration signal VRc as the amplitude of the second peak and the amplitude of the third peak of the residual vibration of the diaphragm 14 resulting from ten consecutive executions of the ejection drive. Hereinafter, the amplitudes λC1, λC2, and λC3 of the residual vibration signal VRc may be collectively referred to as amplitude λC.

[0109] 7, to distinguish the amplitude λC of the residual vibration signal VRca from the amplitude λC of the residual vibration signal VRcb, the letters "a" or "b" are added to the end of each of the symbols for the amplitudes λC1, λC2, and λC3. For example, amplitudes λC1a, λC2a, and λC3a represent the amplitude λC1 of the first peak, the amplitude λC2 of the second peak, and the amplitude λC3 of the third peak of the residual vibration signal VRca, respectively. Furthermore, amplitudes λC1b, λC2b, and λC3b represent the amplitude λC1 of the first peak, the amplitude λC2 of the second peak, and the amplitude λC3 of the third peak of the residual vibration signal VRcb, respectively.

[0110] When ejection is stable, the waveform of the residual vibration signal VRc is similar to that of the residual vibration signal VRs, as shown by the residual vibration signals VRs and VRca. In other words, when ejection is unstable, the waveform of the residual vibration signal VRc is dissimilar to that of the residual vibration signal VRs, as shown by the residual vibration signals VRs and VRcb. Experiments conducted by the inventors have shown that when ejection is unstable, the difference between the amplitude λC of the residual vibration signal VRc and the amplitude λS of the residual vibration signal VRs increases. Therefore, in this embodiment, when at least one of the difference between the amplitude λS1 and the amplitude λC1, the difference between the amplitude λS2 and the amplitude λC2, and the difference between the amplitude λS3 and the amplitude λC3 is equal to or greater than a predetermined value, the waveform of the residual vibration signal VRc is deemed dissimilar to that of the residual vibration signal VRs. The predetermined value is determined, for example, for each peak of the residual vibration signal VR.

[0111] The amplitude λC1 is an example of the “amplitude of the first peak,” and the amplitude λC2 is an example of the “amplitude of the second peak.” Furthermore, the amplitude λS1 is an example of the “amplitude of the third peak,” and the amplitude λS2 is an example of the “amplitude of the fourth peak.”

[0112] Furthermore, for example, the analysis unit 3 identifies the period of the residual vibration signal VR as the period of the residual vibration of the diaphragm 14, and identifies the phase of the residual vibration signal VR as the phase of the residual vibration of the diaphragm 14. Here, in this embodiment, it is assumed that, of the amplitude, period, and phase of the residual vibration of the diaphragm 14, the amplitude is used to evaluate the ejection stability. In this case, the analysis unit 3 does not need to identify the period and phase of the residual vibration signal VRc. Also, in this embodiment, it is assumed that, of the amplitude, period, and phase of the residual vibration of the diaphragm 14, the period is used to evaluate the ejection state of the nozzle N. In this case, the analysis unit 3 does not need to identify the phase of the residual vibration signal VRs.

[0113] The method for analyzing residual vibration is not limited to the above example, and any known method can be used.

[0114] The analysis unit 3 outputs, for example, residual vibration information Vinf indicating the analysis result of the residual vibration, i.e., the analysis result of the residual vibration signal VR, to the control unit 4. For example, the analysis unit 3 outputs, to the control unit 4, residual vibration information Vinf indicating the amplitudes λC1, λC2, and λC3 of the residual vibration signal VRc as the analysis result of the residual vibration of the diaphragm 14 resulting from ten consecutive ejection drives. Furthermore, for example, the analysis unit 3 outputs, to the control unit 4, residual vibration information Vinf indicating the amplitudes λS1, λS2, and λS3 and period of the residual vibration signal VRs as the analysis result of the residual vibration of the diaphragm 14 resulting from only one ejection drive.

[0115] Next, with reference to FIG. 8, the operation of the liquid ejection device 100 when evaluating ejection stability will be described.

[0116] FIG. 8 is a flowchart showing an example of the operation of the liquid ejection device 100 when evaluating the stability of ink ejection from the nozzles N. The timing of executing the operation shown in FIG. 8 is not particularly limited, but it is preferable that the operation be executed when the liquid ejection device 100 is used for the first time, or when the operating conditions of the liquid ejection device 100 are changed due to a change in the type of ink used, etc. The operating conditions of the liquid ejection device 100 also include the operating conditions of the liquid ejection head 1. The operation shown in FIG. 8 is executed for each of the multiple liquid ejection heads 1, for example. The operation shown in FIG. 8 also assumes a case where the ejection state of the nozzles N is evaluated before evaluating the ejection stability.

[0117] The control unit 4 functions as the evaluation control unit 40 in each of steps S100 to S250 shown in Fig. 8. The process of step S100 is executed, for example, in a state where the pressure chambers CV are filled with ink to be used by a user of the liquid ejection device 100. That is, the process of step S100 is executed after the pressure chambers CV are filled with ink to be used by the user. The process of filling the pressure chambers CV with ink may be executed by the evaluation control unit 40, or may be executed by a processing unit other than the evaluation control unit 40. The user is, for example, a user of the liquid ejection device 100. Furthermore, if the manufacturer and the user of the liquid ejection device 100 are the same, the manufacturer of the liquid ejection device 100 may be regarded as the user.

[0118] First, in step S100, the evaluation control unit 40 executes ejection driving once. For example, the evaluation control unit 40 controls the liquid ejection head 1 so that the piezoelectric element PZ of the ejection portion D to be detected is driven by a drive signal COM that ejects ink from the nozzle N. As a result, the piezoelectric element PZ of the ejection portion D to be detected is driven so that ink is ejected from the nozzle N of the ejection portion D to be detected.

[0119] Next, in step S110, the evaluation control unit 40 detects residual vibrations of the ejection unit D to be detected. For example, the evaluation control unit 40 causes the detection circuit 19 to detect residual vibrations from the piezoelectric elements PZ of the ejection unit D to be detected in the unit period TU following the unit period TU in which the ejection drive was performed. As a result, the residual vibrations of the diaphragm 14 resulting from performing the ejection drive only once are detected by the detection circuit 19. The residual vibrations detected by the detection circuit 19 are then analyzed by the analysis unit 3. As a result, for example, the amplitudes λS1, λS2, and λS3 and the period of the residual vibration signal VRs are identified as the analysis results of the residual vibrations of the diaphragm 14 resulting from performing the ejection drive only once. The evaluation control unit 40 then acquires residual vibration information Vinf from the analysis unit 3, which indicates the analysis results of the residual vibrations detected by the detection circuit 19. The residual vibrations detected in step S110 are an example of a "second residual vibration."

[0120] Next, in step S120, the evaluation control unit 40 evaluates the ejection state of the nozzle N. For example, if the amplitude λS1 of the residual vibration signal VRs is equal to or greater than a predetermined amplitude and the period of the residual vibration signal VRs is equal to or greater than a first predetermined value and equal to or less than a second predetermined value, the evaluation control unit 40 evaluates that the ejection state of the nozzle N of the ejection unit D being detected is normal. In other words, if the amplitude λS1 of the residual vibration signal VRs is less than a predetermined amplitude, or if the period of the residual vibration signal VRs is outside the range of equal to or greater than the first predetermined value and equal to or less than a second predetermined value, the evaluation control unit 40 evaluates that the ejection state of the nozzle N is abnormal.

[0121] Here, the first predetermined value is a value that indicates the boundary between the time length of one cycle of residual vibration when the ejection state of nozzle N is normal and the time length of one cycle of residual vibration when an air bubble has entered the pressure chamber CV. The second predetermined value is a value that indicates the boundary between the time length of one cycle of residual vibration when the ejection state of nozzle N is normal and the time length of one cycle of residual vibration when foreign matter has adhered near the nozzle N. The third predetermined value, which will be described later, is a value that indicates the boundary between the time length of one cycle of residual vibration when foreign matter has adhered near the nozzle N and the time length of one cycle of residual vibration when the ink in the pressure chamber CV has thickened. Note that, for example, the second predetermined value is greater than the first predetermined value and smaller than the third predetermined value.

[0122] For example, if the amplitude λS1 of the residual vibration signal VRs is equal to or greater than a predetermined amplitude and the period of the residual vibration signal VRs is less than a first predetermined value, the evaluation control unit 40 determines that the ejection state of the nozzle N is abnormal due to the inclusion of air bubbles in the nozzle N. Furthermore, if the amplitude λS1 of the residual vibration signal VRs is equal to or greater than a predetermined amplitude and the period of the residual vibration signal VRs is greater than a second predetermined value and less than a third predetermined value, the evaluation control unit 40 determines that the ejection state of the nozzle N is abnormal due to ink leakage from the nozzle N. Furthermore, if the amplitude λS1 of the residual vibration signal VRs is equal to or greater than a predetermined amplitude and the period of the residual vibration signal VRs is greater than a third predetermined value, the evaluation control unit 40 determines that the ejection state of the nozzle N is abnormal due to increased viscosity of the ink in the nozzle N. Furthermore, if the amplitude λS1 of the residual vibration signal VRs is less than a predetermined amplitude, the evaluation control unit 40 determines that the ejection state of the nozzle N is abnormal other than the above-mentioned abnormalities.

[0123] The method for determining the discharge state is not limited to the above example, and any known method can be used. After executing the process of step S120, the evaluation control unit 40 moves the process to step S130.

[0124] In step S130, the evaluation control unit 40 determines whether the ejection state of nozzle N is normal. For example, if the evaluation control unit 40 evaluates that the ejection state of nozzle N is normal in step S120, it determines that the ejection state of nozzle N is normal. Also, for example, if the evaluation control unit 40 evaluates that the ejection state of nozzle N is abnormal in step S120, it determines that the ejection state of nozzle N is abnormal.

[0125] If the result of the determination in step S130 is negative, the evaluation control unit 40 executes a recovery process for the ejection state in step S140, and then returns to step S100 after a predetermined time has elapsed, and the same process is performed again. For example, the evaluation control unit 40 executes a recovery process for restoring the ejection state of nozzle N to a normal state based on the type of abnormality identified in step S120. Note that a known process can be used as the ejection state recovery process. Here, a case is shown in which the series of processes from step S100 to step S140 are repeated until it is determined that the ejection state is normal in step S130. However, if the ejection state continues to be determined to be abnormal in step S130 even after this repetition has been performed a predetermined number of times, the operation of the liquid ejection device 100 may be stopped and a notification may be given to the user.

[0126] On the other hand, if the result of the determination in step S130 is positive, the evaluation control unit 40 moves the process to step S200.

[0127] In step S200, the evaluation control unit 40 sets the waveform of the drive signal COM to be used in step S210. For example, the evaluation control unit 40 sets the waveform of the drive signal COM used in step S100 as the waveform of the drive signal COM to be used in step S210. Note that, for example, when a series of processes from step S200 to step S250 are repeated, in the first step S200, the evaluation control unit 40 sets the waveform of the drive signal COM used in step S100 as the waveform of the drive signal COM to be used in step S210. Then, in the second or subsequent step S200, the evaluation control unit 40 sets a waveform different from the waveform set in the previous step S200 as the waveform of the drive signal COM to be used in step S210. For example, the evaluation control unit 40 sets the length TA of waveform element Pa4 to a length different from the length set in the previous step S200.

[0128] The drive signal COM whose waveform is set in step S200 is an example of a “drive signal candidate.” After executing the process of step S200, the evaluation control unit 40 moves the process to step S210.

[0129] In step S210, the evaluation control unit 40 executes the ejection drive 10 times in succession. For example, the evaluation control unit 40 controls the liquid ejection head 1 so that, in each of 10 consecutive unit periods TU, the piezoelectric element PZ of the ejection unit D to be detected is driven by the drive signal COM having the waveform set in step S200. As a result, the ejection drive that ejects ink from the nozzle N of the ejection unit D to be detected is executed 10 times in succession.

[0130] Next, in step S220, the evaluation control unit 40 detects the residual vibration of the discharge unit D to be detected immediately after the 10 consecutive discharge drives of step S210 are performed. For example, the evaluation control unit 40 causes the detection circuit 19 to detect the residual vibration from the piezoelectric element PZ of the discharge unit D to be detected in the unit period TU next to the 10 consecutive unit periods TU in which the discharge drives were performed. As a result, the residual vibration of the diaphragm 14 resulting from the 10 consecutive discharge drives is detected by the detection circuit 19. The residual vibration detected by the detection circuit 19 is then analyzed by the analysis unit 3. As a result, for example, the amplitudes λC1, λC2, and λC3 of the residual vibration signal VRc are identified as the analysis result of the residual vibration of the diaphragm 14 resulting from the 10 consecutive discharge drives. The evaluation control unit 40 then acquires residual vibration information Vinf from the analysis unit 3, which indicates the analysis result of the residual vibration detected by the detection circuit 19. The residual vibration detected in step S220 is an example of a “first residual vibration.”

[0131] Next, in step S230, the evaluation control unit 40 evaluates the ejection stability. The process of step S230, i.e., the stability evaluation, determines whether the ejection of ink from the nozzle N when the piezoelectric element PZ is driven by the drive signal COM having the waveform set in step S200 is stable or unstable. Details of the stability evaluation will be explained later with reference to FIG. 9.

[0132] Next, in step S240, the evaluation control unit 40 stores the evaluation result of the ejection stability. For example, the evaluation control unit 40 stores the evaluation result of the ejection stability in the storage unit 5 in association with the driving signal COM having the waveform set in step S200.

[0133] Next, in step S250, the evaluation control unit 40 determines whether or not to change the waveform of the drive signal COM. That is, the evaluation control unit 40 determines whether or not to change the waveform of the drive signal COM and execute the series of processes from step S210 to step S230 again.

[0134] For example, the evaluation control unit 40 may determine to change the waveform of the drive signal COM if the result of the stability evaluation performed in step S230 indicates that the ink ejection is unstable. Alternatively, the evaluation control unit 40 may determine to change the waveform of the drive signal COM if there is a drive signal candidate that is not used in step S210 among the multiple drive signal candidates including the drive signal COM used in step S100. For example, the waveforms of the multiple drive signal candidates are determined based on the ink ejection characteristics of the ejection unit D, and are similar to each other except for the length TA of the waveform element Pa4 and the length TB of the waveform element Pa5.

[0135] If the result of the determination in step S250 is positive, the evaluation control unit 40 returns the process to step S200. On the other hand, if the result of the determination in step S250 is negative, the evaluation control unit 40 ends the operation shown in FIG.

[0136] 8 illustrates an example in which the length TA of waveform element Pa4 is changed by repeating the series of processes from step S200 to step S250, but the present invention is not limited to this example. For example, by repeating the series of processes from step S200 to step S250, parameters other than the length TA of waveform element Pa4 may be changed instead of or in addition to the length TA of waveform element Pa4. Parameters other than the length TA of waveform element Pa4 include, for example, the slope of waveform element Pa1, the length of waveform element Pa2, the slope of waveform element Pa3, the slope of waveform element Pa5, the potential VHa, and the potential VLa.

[0137] The series of processes from step S100 to step S120 is an example of a "second evaluation", and the series of processes from step S210 to step S230 is an example of a "first evaluation".

[0138] Next, an example of the stability evaluation performed in step S230 will be described with reference to FIG.

[0139] Fig. 9 is a flowchart showing an example of the stability evaluation shown in Fig. 8. A series of processes from step S232 to step S239 shown in Fig. 9 corresponds to the process of step S230 shown in Fig. 8. For example, the process of step S232 is executed after the process of step S220 shown in Fig. 8 is executed, and after the process of step S238 or step S239 is executed, the process of step S240 shown in Fig. 8 is executed. The control unit 4 functions as the evaluation control unit 40 in each of steps S232 to S239 shown in Fig. 9.

[0140] In the operation shown in Figure 9, the amplitudes λS1, λS2 and λS3 of the residual vibration signal VRs determined by the processing of step S110 shown in Figure 8, and the amplitudes λC1, λC2 and λC3 of the residual vibration signal VRc determined by the processing of step S220 shown in Figure 8 are used.

[0141] First, in step S232, the evaluation control unit 40 determines whether the amplitude λC1 is 1.3 times or less than the amplitude λS1. That is, the evaluation control unit 40 determines whether the amplitude of the first peak of the residual vibration of the diaphragm 14 resulting from ten consecutive ejection drives is 1.3 times or less than the amplitude of the first peak of the residual vibration of the diaphragm 14 resulting from a single ejection drive. Note that the value obtained by multiplying the amplitude λS1 by 1.3, i.e., the value obtained by multiplying the amplitude λS1 by the coefficient "1.3", is an example of a "first threshold value". Also, the coefficient "1.3" by which the amplitude λS1 is multiplied is an example of a "first coefficient". Note that the "first coefficient" is not limited to "1.3".

[0142] If the result of the determination in step S232 is negative, the evaluation control unit 40 determines in step S239 that the ink ejection is unstable, and then proceeds to step S240 shown in Fig. 8. That is, after executing the process of step S239, the evaluation control unit 40 ends the operation shown in Fig. 9. In this way, the evaluation control unit 40 determines that the ink ejection is unstable when the amplitude λC1 of the first peak of the residual vibration signal VRc is greater than 1.3 times the amplitude λS1 of the first peak of the residual vibration signal VRs.

[0143] On the other hand, if the result of the determination in step S232 is positive, the evaluation control unit 40 moves the process to step S234.

[0144] In step S234, the evaluation control unit 40 determines whether the amplitude λC2 is equal to or less than 1.2 times the amplitude λS2. That is, the evaluation control unit 40 determines whether the amplitude of the second peak of the residual vibration of the diaphragm 14 resulting from ten consecutive ejection drives is equal to or less than 1.2 times the amplitude of the second peak of the residual vibration of the diaphragm 14 resulting from a single ejection drive. Note that the value obtained by multiplying the amplitude λS2 by 1.2, i.e., the value obtained by multiplying the amplitude λS2 by the coefficient "1.2", is an example of a "second threshold value". Also, the coefficient "1.2" by which the amplitude λS2 is multiplied is an example of a "second coefficient". Note that the "second coefficient" is not limited to "1.2".

[0145] If the result of the determination in step S234 is negative, the evaluation control unit 40 determines in step S239 that the ink ejection is unstable, and then proceeds to step S240 shown in Fig. 8. In this way, the evaluation control unit 40 determines that the ink ejection is unstable if the amplitude λC2 of the second peak of the residual vibration signal VRc is greater than 1.2 times the amplitude λS2 of the second peak of the residual vibration signal VRs.

[0146] On the other hand, if the result of the determination in step S234 is positive, the evaluation control unit 40 moves the process to step S236.

[0147] In step S236, the evaluation control unit 40 determines whether the amplitude λC3 is 1.1 times or less the amplitude λS3. That is, the evaluation control unit 40 determines whether the amplitude of the third peak of the residual vibration of the diaphragm 14 resulting from performing the ejection drive ten times in succession is 1.1 times or less the amplitude of the third peak of the residual vibration of the diaphragm 14 resulting from performing the ejection drive only once. Note that the coefficient by which the amplitude λS3 is multiplied is not limited to "1.1".

[0148] If the result of the determination in step S236 is negative, the evaluation control unit 40 determines in step S239 that the ink ejection is unstable, and then proceeds to step S240 shown in Fig. 8. In this way, the evaluation control unit 40 determines that the ink ejection is unstable when the amplitude λC3 of the third peak of the residual vibration signal VRc is greater than 1.1 times the amplitude λS2 of the third peak of the residual vibration signal VRs.

[0149] On the other hand, if the result of the determination in step S238 is positive, the evaluation control unit 40 moves the process to step S238.

[0150] In step S238, the evaluation control unit 40 determines that the ink ejection is stable. That is, if the results of the determinations in steps S232, S234, and S236 are all positive, the evaluation control unit 40 determines that the ink ejection is stable. Then, after executing the process of step S238, the control unit 4 proceeds to step S240 shown in Fig. 8. That is, after executing the process of step S238, the evaluation control unit 40 ends the operation shown in Fig. 9.

[0151] In this way, the stability evaluation shown in FIG. 9 identifies the drive signals COM that result in stable ink ejection and the drive signals COM that result in unstable ink ejection.

[0152] 9, a value based on the amplitude λS of the residual vibration signal VRs is used as the threshold value to be compared with the amplitude λC of the residual vibration signal VRc. Specifically, the first threshold value to be compared with the amplitude λC1 is a value based on the amplitude λS1, the second threshold value to be compared with the amplitude λC2 is a value based on the amplitude λS2, and the third threshold value to be compared with the amplitude λC3 is a value based on the amplitude λS3. In this embodiment, by using a value based on the amplitude λS of the residual vibration signal VRs as the threshold value to be compared with the amplitude λC of the residual vibration signal VRc, it is possible to use a threshold value that corresponds to the operating conditions of the liquid ejection head 1, such as the type of ink used. This makes it possible to accurately evaluate the ejection stability in this embodiment.

[0153] In the stability evaluation shown in FIG. 9 , the first threshold is the value obtained by multiplying the amplitude λS1 by the first coefficient “1.3,” the second threshold is the value obtained by multiplying the amplitude λS2 by the second coefficient “1.2,” and the third threshold is the value obtained by multiplying the amplitude λS3 by the third coefficient “1.1.” The second coefficient is smaller than the first coefficient, and the third coefficient is smaller than the second coefficient. Here, because the residual vibration decays, the amplitude of the latter peaks of the residual vibration signal VR tends to be smaller than the amplitude of the first peaks. The larger the actual data value (peak amplitude), the greater the deviation in the measured value when a measurement error occurs. Therefore, by making the first coefficient larger than the second coefficient and the second coefficient larger than the third coefficient and allowing for deviation in the first peaks where the amplitude is larger, the ejection stability can be accurately evaluated. However, the relationship between the first coefficient, the second coefficient, and the third coefficient is not limited to the example described above. For example, the first coefficient, the second coefficient, and the third coefficient may be the same value.

[0154] The operation of the liquid ejection device 100 when evaluating ejection stability is not limited to the examples shown in FIGS. 8 and 9. For example, in the operation shown in FIG. 9, the evaluation control unit 40 may also determine the lower limit of the amplitude λC of the residual vibration signal VRc. Specifically, before executing the process of step S232, the evaluation control unit 40 may determine whether the amplitude λC1 is 0.7 times the amplitude λS1 or more. If the amplitude λC1 is less than 0.7 times the amplitude λS1, the evaluation control unit 40 may determine in step S239 that the ink ejection is unstable, and then proceed to step S240 shown in FIG. 8. That is, in this embodiment, the process of step S232 is executed if the amplitude λC1 is 0.7 times the amplitude λS1 or more. The threshold indicating the lower limit of the amplitude λC is not limited to 0.7 times the amplitude λS1. Furthermore, for example, a lower limit of the amplitude λC may be set in each of steps S232, S234, and S236.

[0155] 9, one of the processes of step S232, step S234, and step S236 may be omitted. For example, in an aspect in which the process of step S236 is omitted, the evaluation control unit 40 determines that the ejection is stable when the amplitude λC1 is 1.3 times or less the amplitude λS1 and the amplitude λC2 is 1.2 times or less the amplitude λS2.

[0156] 9, two of the processes of step S232, step S234, and step S236 may be omitted. That is, the evaluation control unit 40 may evaluate the stability of ink ejection from the nozzle N based on the amplitude of at least one peak among multiple peaks of the residual vibration of the diaphragm 14 resulting from performing the ejection drive ten times in succession.

[0157] Also, for example, the threshold value compared with the amplitude λC of the residual vibration signal VRc may be a predetermined amplitude value. That is, the first threshold value compared with the amplitude λC1, the second threshold value compared with the amplitude λC2, and the third threshold value compared with the amplitude λC3 may each be a predetermined fixed value. In this embodiment, it is preferable that the second threshold value is smaller than the first threshold value, and the third threshold value is smaller than the second threshold value. Also, in this embodiment, the series of processes from step S100 to step S140 shown in FIG. 8 may be omitted or may be performed after the ejection stability has been evaluated.

[0158] 9, instead of or in addition to the amplitude λC of the residual vibration signal VRc, one or both of the period and phase of the residual vibration signal VRc may be used to evaluate the stability of ejection. For example, the evaluation control unit 40 may determine that ejection is unstable when the period of the residual vibration signal VRc is outside the range of 0.8 to 1.2 times the period of the residual vibration signal VRs. Similarly, the evaluation control unit 40 may determine that ejection is unstable when the phase of the residual vibration signal VRc is outside the range of 0.8 to 1.2 times the phase of the residual vibration signal VRs. Note that the lower and upper limits of the period compared with the period of the residual vibration signal VRc and the lower and upper limits of the phase compared with the phase of the residual vibration signal VRc are not limited to the above examples.

[0159] Furthermore, for example, the evaluation control unit 40 may determine the waveform of the drive signal COM based on the results of the evaluation of the ejection stability. For example, the evaluation control unit 40 may adopt the drive signal COM determined to have stable ejection in the stability evaluation shown in FIG. 9 as the drive signal COM to be used in the actual printing process. That is, the evaluation control unit 40 may determine the waveform of the drive signal COM based on the first residual vibration detected by the detection circuit 19 as the residual vibration of the diaphragm 14 resulting from continuous execution of ejection driving. In this manner, in this embodiment, the waveform of the drive signal COM can be easily determined to be an appropriate waveform that stabilizes ink ejection based on the first residual vibration. Furthermore, for example, when there are multiple candidates for the drive signal COM determined to have stable ejection, the evaluation control unit 40 may adopt, as the drive signal COM, the candidate whose waveform of the residual vibration signal VRc matches or is most similar to the waveform of the residual vibration signal VRs. In this embodiment, determining the waveform of the drive signal COM based on the results of the evaluation of the ejection stability makes it easy to prevent the ink ejection from the nozzles N from becoming unstable.

[0160] As described above, in this embodiment, the liquid ejection device 100 includes a liquid ejection head 1 including a nozzle N that ejects ink, a piezoelectric element PZ corresponding to the nozzle N, a vibration plate 14 that vibrates when the piezoelectric element PZ is driven, and a detection circuit 19 that detects residual vibration of the vibration plate 14 caused by driving the piezoelectric element PZ, and an evaluation control unit 40 that performs a first evaluation to evaluate the stability of ink ejection from the nozzle N. In the first evaluation, the evaluation control unit 40 causes the detection circuit 19 to detect, as first residual vibration, residual vibration caused by continuously executing ejection driving to drive the piezoelectric element PZ with a drive signal COM that ejects ink from the nozzle N, and evaluates the stability of ink ejection from the nozzle N based on the first residual vibration detected by the detection circuit 19. The evaluation control unit 40 may also determine the waveform of the drive signal COM based on the first residual vibration detected by the detection circuit 19.

[0161] As described above, in this embodiment, the evaluation control unit 40 evaluates the stability of ink ejection based on the first residual vibration caused by continuously executing ejection driving that drives the piezoelectric element PZ with the drive signal COM that ejects ink from the nozzle N. Therefore, in this embodiment, it is possible to appropriately and easily evaluate the stability of ink ejection from the nozzle N without requiring external elements such as an imaging environment. Furthermore, in this embodiment, the evaluation control unit 40 determines the waveform of the drive signal COM that drives the piezoelectric element PZ based on the first residual vibration, thereby appropriately and easily determining the waveform of the drive signal COM that drives the piezoelectric element PZ.

[0162] Furthermore, in this embodiment, the evaluation control unit 40 may evaluate the stability of ink ejection from the nozzle N in the first evaluation based on the amplitude of at least one peak among the multiple peaks of the first residual vibration. In this case, it is possible to appropriately and easily evaluate the stability of ink ejection from the nozzle N without specifying the period and phase of the first residual vibration.

[0163] Furthermore, in this embodiment, the evaluation control unit 40 may determine that the stability of ink ejection from the nozzle N is unstable if, in the first evaluation, the amplitude of the first peak, which is the first of the multiple peaks of the first residual vibration, is greater than the first threshold value. In this case, too, it is possible to appropriately and easily evaluate the stability of ink ejection from the nozzle N. Furthermore, when it is determined that ink ejection is unstable based on the amplitude of the first peak of the multiple peaks of the first residual vibration, there is no need to refer to the amplitudes of the other peaks, and therefore it is possible to suppress an increase in the load involved in evaluating the ejection stability.

[0164] Furthermore, in this embodiment, if the amplitude of the second peak among the multiple peaks of the first residual vibration is greater than a second threshold value in the first evaluation, the evaluation control unit 40 may determine that the ink ejection from the nozzle N is unstable. In this case, the ejection stability is evaluated based on the multiple peaks of the first residual vibration, and therefore the ejection stability can be evaluated with high accuracy.

[0165] Furthermore, in this embodiment, the evaluation control unit 40 may determine that the ink ejection from the nozzle N is stable if, in the first evaluation, the amplitude of the first peak is equal to or less than a first threshold value and the amplitude of the second peak is equal to or less than a second threshold value. In this case as well, the ejection stability can be evaluated with high accuracy.

[0166] Furthermore, in this embodiment, the evaluation control unit 40 may cause the detection circuit 19 to detect the residual vibration resulting from executing the ejection drive only once as the second residual vibration, and may use a value based on the amplitude of the first, third peak of the multiple peaks of the second residual vibration as the first threshold value. Thus, in this aspect, a value based on the amplitude of the first peak of the second residual vibration resulting from executing the ejection drive only once is used as the first threshold value to be compared with the amplitude of the first peak of the first residual vibration. That is, in this aspect, a threshold value according to the usage conditions of the liquid ejection head 1 is used as the first threshold value. As a result, in this aspect, the ejection stability can be accurately evaluated in accordance with the usage conditions of the liquid ejection head 1.

[0167] In this embodiment, the evaluation control unit 40 causes the detection circuit 19 to detect the residual vibration resulting from a single execution of the ejection drive as the second residual vibration in the first evaluation, and uses the value obtained by multiplying the amplitude of the first, third peak of the multiple peaks of the second residual vibration by a first coefficient as the first threshold value, and uses the value obtained by multiplying the amplitude of the second, fourth peak of the multiple peaks of the second residual vibration by a second coefficient smaller than the first coefficient as the second threshold value. This embodiment also allows for accurate evaluation of ejection stability in accordance with the usage conditions of the liquid ejection head 1. This embodiment also allows for accurate evaluation of ejection stability compared to evaluating ejection stability based only on the amplitude of the first, first peak of the first residual vibration.

[0168] Furthermore, in this embodiment, the evaluation control unit 40 may cause the detection circuit 19 to detect the residual vibration resulting from executing the ejection drive only once as the second residual vibration, and may further perform a second evaluation to evaluate the ejection state of the nozzle N based on the second residual vibration detected by the detection circuit 19. In this way, in this aspect, the ejection state of the nozzle N can be appropriately and easily evaluated using the second residual vibration.

[0169] Furthermore, in this embodiment, the evaluation control unit 40 may select one of a plurality of drive signal candidates having different waveforms for ejecting ink from the nozzle N as the drive signal COM, perform a first evaluation on each of the plurality of drive signal candidates, and identify, from the plurality of drive signal candidates, a drive signal candidate that stabilizes the ejection of ink from the nozzle N and a drive signal candidate that stabilizes the ejection of ink from the nozzle N. In this aspect, by determining the waveform of the drive signal COM to be the waveform of the drive signal candidate that stabilizes the ejection of ink from the nozzle N, it is possible to appropriately and easily determine the waveform of the drive signal COM that drives the piezoelectric element PZ.

[0170] Furthermore, in this embodiment, the evaluation control unit 40 may cause the detection circuit 19 to detect, as the first residual vibration, the residual vibration resulting from performing the ejection drive 10 or more times in succession in the first evaluation. In this mode as well, the stability of ink ejection from the nozzles N can be appropriately and easily evaluated.

[0171] [2. Modifications] Each of the above embodiments can be modified in various ways. Specific modified embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within a range that does not contradict each other. In the modified examples exemplified below, elements whose actions and functions are equivalent to those of the embodiments will be designated by the same reference numerals as in the above description, and detailed descriptions of each will be omitted as appropriate.

[0172] [First Modification] In the above-described embodiment, a drive signal COM for detecting an ejection abnormality in the nozzle N may be supplied from the drive signal generation unit 2 to the liquid ejection head 1. In this modification, the ejection state of the nozzle N can be evaluated by driving the piezoelectric element PZ with the drive signal COM for detecting an ejection abnormality in the nozzle N.

[0173] Fig. 10 is a block diagram showing an example of the configuration of a liquid ejection head 1 according to a first modified example. The liquid ejection head 1 shown in Fig. 10 is similar to the liquid ejection head 1 shown in Fig. 5, except that a drive signal COMb for detecting ejection abnormalities in the nozzles N is supplied from a drive signal generation unit 2. Specifically, the liquid ejection head 1 shown in Fig. 10 is similar to the liquid ejection head 1 shown in Fig. 5, except that it has a switching circuit 18A instead of the switching circuit 18 shown in Fig. 5. The drive signal COMa shown in Fig. 10 is similar to the drive signal COM shown in Fig. 6.

[0174] 5, except that a wiring Lb to which a drive signal COMb is supplied from the drive signal generating unit 2 and M switches SWb[1] to SWb[M] corresponding one-to-one to the M discharge sections D[1] to D[M] are added to the switching circuit 18. However, the connection state specifying circuit CSC generates connection state specifying signals Qa[m], Qb[m], and Qs[m] based on at least some of the print signal SI, latch signal LAT, and period specifying signal Tsig supplied from the control unit 4.

[0175] The switch SWb[m] switches between conduction and non-conduction between the wiring Lb and the individual electrode Za[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] based on the connection state designation signal Qb[m]. That is, the switch SWb[m] switches between conduction and non-conduction between the wiring Lb and the wiring Li[m] connected to the individual electrode Za[m] based on the connection state designation signal Qb[m]. In this modified example, the switch SWb[m] is turned on when the connection state designation signal Qb[m] is at a high level and turned off when it is at a low level. When the switch SWb[m] is turned on, the drive signal COMb supplied to the wiring Lb is supplied as an individual drive signal Vin[m] to the individual electrode Za[m] of the discharge section D[m] via the wiring Li[m].

[0176] Next, the operation of the liquid ejection device 100 according to the first modified example will be described with reference to FIG.

[0177] Fig. 11 is a timing chart showing an example of the operation of the liquid ejection device 100 according to the first modified example. The operation of the connection state specification circuit CSC and the like when the drive mode of the ejection unit D that forms dots, the ejection unit D that does not form dots, and the ejection unit D that is the detection target when evaluating the ejection stability is specified by the individual specification signal Sd[m] is the same as the operation described in Fig. 6. For this reason, Fig. 11 describes the operation of the connection state specification circuit CSC and the like when the drive mode of the ejection unit D that is the detection target for ejection abnormalities in the nozzle N is specified by the individual specification signal Sd[m].

[0178] For example, the drive signal generating unit 2 outputs a drive signal COMb having a pulse PS. The pulse PS has a waveform in which the potential of the drive signal COMb changes from potential V0 to potential VLs, which is lower than potential V0, through potential VHs, which is higher than potential V0, and back to potential V0. In this modification, the pulse PS is determined so that the potential difference between potential VHs, which is the highest potential of the pulse PS, and potential VLs, which is the lowest potential, is smaller than the potential difference between potential VHa, which is the highest potential of the pulse PA, and potential VLa, which is the lowest potential. Specifically, when the drive signal COMb having the pulse PS is supplied to the ejection section D[m], the waveform of the pulse PS is determined so that the ejection section D[m] is driven to such an extent that ink is not ejected from the ejection section D[m]. As described above, the start and end potentials of the pulse PS are set to potential V0.

[0179] The control unit 4 also outputs a period defining signal Tsig having a pulse PLSt1 and a pulse PLSt2, thereby dividing the unit period TU into a control period TSS1 from the start of the pulse PlsL to the start of the pulse PLSt1, a control period TSS2 from the start of the pulse PLSt1 to the start of the pulse PLSt2, and a control period TSS3 from the start of the pulse PLSt2 to the start of the next pulse PlsL.

[0180] For example, when the individual designation signal Sd[m] designates the discharge section D[m] as the discharge section D for which discharge abnormalities are to be detected, the connection state designation circuit CSC sets the connection state designation signal Qa[m] to a low level during the unit period TU. The connection state designation circuit CSC also sets the connection state designation signal Qb[m] to a high level during the control periods TSS1 and TSS3, and to a low level during the control period TSS2. The connection state designation circuit CSC also sets the connection state designation signal Qs[m] to a low level during the control periods TSS1 and TSS3, and to a high level during the control period TSS2.

[0181] In this case, the piezoelectric element PZ[m] of the discharge section D[m] to be detected for discharge abnormalities is driven by the pulse PS of the drive signal COMb during the control period TSS1. Specifically, the piezoelectric element PZ[m] is displaced by the pulse PS of the drive signal COMb during the control period TSS1. As a result, vibration occurs in the discharge section D[m] to be detected. The vibration generated during the control period TSS1 remains during the control period TSS2. Then, during the control period TSS2, the potential of the individual electrode Za[m] of the piezoelectric element PZ[m] of the discharge section D[m] to be detected changes depending on the residual vibration generated in the discharge section D[m]. That is, during the control period TSS2, the potential of the individual electrode Za of the piezoelectric element PZ of the discharge section D to be detected becomes a potential corresponding to the electromotive force of the piezoelectric element PZ caused by the residual vibration generated in the discharge section D to be detected. Then, the potential of the individual electrode Za is detected as the detection signal Vout during the control period TSS2.

[0182] 11 illustrates an example in which the detection signal Vout indicating the residual vibration of the ejection section D that is the target of ejection abnormality detection is generated during the printing process period, but the detection signal Vout may be generated during a period other than the printing process period. In other words, the process of detecting the residual vibration of the ejection section D that is the target of ejection abnormality detection may be executed during a period other than the printing process period.

[0183] In this manner, in this modified example, it is possible to detect an ejection abnormality in the nozzle N based on the residual vibration detected using the drive signal COMb. The detection of an ejection abnormality using the drive signal COMb may be performed before or after the ejection stability is evaluated. Note that in this modified example, when evaluating the ejection stability, the series of processes from step S100 to step S140 shown in FIG. 8 may be omitted.

[0184] As described above, this modified example also provides the same effects as the above-described embodiment. Furthermore, this modified example makes it possible to detect ejection abnormalities in the nozzle N based on the residual vibration detected using the drive signal COMb. In other words, this modified example makes it possible to evaluate the ejection state of the nozzle N based on the residual vibration detected using the drive signal COMb.

[0185] [Second Modification] In the above-described embodiment and modified examples, each time the waveform of the drive signal COM used to evaluate the ejection stability is changed, the residual vibration of the diaphragm 14 resulting from performing ejection driving only once using the drive signal COM with the changed waveform may be detected.

[0186] Fig. 12 is a flowchart showing an example of the operation of the liquid ejection device 100 according to the second modified example. The operation shown in Fig. 12 is the same as the operation shown in Fig. 8, except that a series of processes in steps S202 and S204 are executed between steps S200 and S210. The control unit 4 functions as the evaluation control unit 40 in each of steps S202 and S204.

[0187] For example, after executing the process of step S200, the evaluation control unit 40 moves the process to step S202.

[0188] In step S202, the evaluation control unit 40 executes ejection driving once using the driving signal COM having the waveform set in step S200.

[0189] Next, in step S204, the evaluation control unit 40 detects the residual vibration of the ejection unit D to be detected, similarly to step S110. As a result, for example, the amplitudes λS1, λS2, and λS3 of the residual vibration signal VRs are identified as the analysis result of the residual vibration of the diaphragm 14 resulting from a single execution of ejection driving using the drive signal COM having the waveform set in step S200. In step S204, the period and phase of the residual vibration signal VRs do not need to be identified. The evaluation control unit 40 acquires residual vibration information Vinf from the analysis unit 3, which indicates the analysis result of the residual vibration detected by the detection circuit 19. The residual vibration detected in step S204 is an example of a "second residual vibration."

[0190] After executing the process of step S204, the evaluation control unit 40 moves the process to step S210.

[0191] In this manner, in this modified example, the same drive signal COM is used to detect the residual vibration of the diaphragm 14 resulting from performing the ejection drive only once and to detect the residual vibration of the diaphragm 14 resulting from performing the ejection drive ten consecutive times. Therefore, in this modified example, a threshold value corresponding to the waveform of the drive signal COM used in step S210 is used as the threshold value to be compared with the amplitude λC of the residual vibration signal VRc.

[0192] The operation of the liquid ejection device 100 according to this modified example is not limited to the example shown in Fig. 12. For example, the series of processes from step S100 to step S140 shown in Fig. 12 may be omitted. Also, for example, the series of processes from step S100 to step S120 may involve detecting an ejection abnormality using the drive signal COMb described in Fig. 11.

[0193] As described above, this modification can also achieve the same effects as the above-described embodiment. Furthermore, in this modification, a threshold value corresponding to the waveform of the drive signal COM is used as the threshold value to be compared with the amplitude λC of the residual vibration signal VRc, so that the ejection stability can be evaluated with high accuracy.

[0194] [Third Modification] In the above-described embodiment and modified examples, waveform information indicating candidates for the drive signal COM used in evaluating the ejection stability may be stored in advance in a storage unit (not shown) of the liquid ejection head 1 at the time the head manufacturer manufactures the liquid ejection head 1. Alternatively, waveform information indicating candidates for the drive signal COM may be stored in a storage unit 5 or the like from the head manufacturer via a network (not shown) after shipping of the liquid ejection head 1. For example, waveform information indicating candidates for the drive signal COM prepared by the head manufacturer is read from a storage unit 5 or the like in which waveform information indicating candidates for the drive signal COM is stored when the operation shown in FIG. 8 is performed.

[0195] As described above, in this modified example, the same effects as those of the above-described embodiment can be obtained.

[0196] [Fourth Modification] In the above-described embodiment and modified example, the piezoelectric element Zb is displaced in the Z1 direction as the potential of the individual drive signal Vin[m] changes from low to high, but the present invention is not limited to this example. For example, a piezoelectric element Zb may be used that is displaced in the Z1 direction as the potential of the individual drive signal Vin[m] changes from high to low. In this case, for example, the potential of the drive signal COM changes from low to high in the portion corresponding to the expansion element, and from high to low in the portion corresponding to the contraction element. This modified example can also achieve the same effects as the above-described embodiment and modified example.

[0197] [Fifth Modification] In the above-described embodiment and modified example, one piezoelectric element PZ, one pressure chamber CV, and one nozzle N are provided for one discharge portion D, but the present invention is not limited to this. For example, one discharge portion D may have two piezoelectric elements PZ, two pressure chambers CV, and one nozzle N. As described above, in this modified example, the same effects as those of the above-described embodiment and modified example can be obtained.

[0198] [Sixth Modification] In the above-described embodiment and modified example, a serial-type liquid ejection device 100 in which a carriage 91 carrying a liquid ejection head 1 is reciprocated in the X-axis direction is illustrated, but the present invention is not limited to such an embodiment. For example, the liquid ejection device 100 may be a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium PP. As described above, this modified example can also achieve the same effects as the above-described embodiment and modified example.

[0199] [Seventh Modification] The liquid ejection device 100 exemplified in the above-described embodiment and modified example can be employed in various devices such as facsimile machines and copiers, as well as devices dedicated to printing. However, the use of the liquid ejection device of the present invention is 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 liquid crystal display devices. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes for wiring boards. As described above, this modified example can also achieve the same effects as the above-described embodiment and modified example.

[0200] [3. Notes] From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0201] A liquid ejection device according to a preferred aspect 1 comprises a liquid ejection head including a nozzle for ejecting liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when the piezoelectric element is driven, and a detection unit that detects residual vibration of the vibration plate caused by driving the piezoelectric element, and a control unit that performs a first evaluation to evaluate the stability of liquid ejection from the nozzle, wherein in the first evaluation, the control unit causes the detection unit to detect the residual vibration caused by continuously executing an ejection drive that drives the piezoelectric element with a drive signal that ejects liquid from the nozzle as a first residual vibration, and evaluates the stability of liquid ejection from the nozzle based on the first residual vibration detected by the detection unit. According to the first aspect, it is possible to appropriately and easily evaluate the stability of liquid ejection from a nozzle without requiring external factors such as an imaging environment.

[0202] In a liquid ejection device according to aspect 2, which is a specific example of aspect 1, the control unit evaluates the stability of ejection of liquid from the nozzle in the first evaluation based on the amplitude of at least one peak among the multiple peaks of the first residual vibration. According to the second aspect, it is possible to appropriately and easily evaluate the stability of the ejection of liquid from the nozzle without specifying the period and phase of the first residual vibration.

[0203] In a liquid ejection device according to aspect 3, which is a specific example of aspect 2, the control unit determines that the ejection of liquid from the nozzle is unstable if, in the first evaluation, the amplitude of the first peak among the multiple peaks of the first residual vibration is greater than a first threshold value. In the third aspect as well, the stability of the liquid ejection from the nozzle can be appropriately and easily evaluated.

[0204] In a liquid ejection device according to aspect 4, which is a specific example of aspect 3, the control unit determines that the ejection of liquid from the nozzle is unstable if, in the first evaluation, the amplitude of the second peak among the multiple peaks of the first residual vibration is greater than a second threshold value. According to the fourth aspect, the ejection stability is evaluated based on a plurality of peaks of the first residual vibration, and therefore the ejection stability can be evaluated with high accuracy.

[0205] In a liquid ejection device according to aspect 5, which is a specific example of aspect 4, the control unit determines that the ejection of liquid from the nozzle is stable if, in the first evaluation, the amplitude of the first peak is less than or equal to the first threshold value and the amplitude of the second peak is less than or equal to the second threshold value. In the fifth aspect as well, the ejection stability can be evaluated with high accuracy.

[0206] In a liquid ejection device according to aspect 6, which is a specific example of any one of aspects 3 to 5, the control unit causes the detection unit to detect the residual vibration resulting from performing the ejection drive only once as a second residual vibration, and uses a value based on the amplitude of a third peak, which is the first of the multiple peaks of the second residual vibration, as the first threshold value. According to the sixth aspect, the ejection stability can be evaluated with high accuracy in accordance with the conditions under which the liquid ejection head is used.

[0207] In the liquid ejection device according to aspect 7, which is a specific example of aspect 4 or aspect 5, the control unit causes the detection unit to detect the residual vibration resulting from executing the ejection drive only once as a second residual vibration, and uses as the first threshold a value obtained by multiplying the amplitude of the third peak, which is the first of the multiple peaks of the second residual vibration, by a first coefficient, and uses as the second threshold a value obtained by multiplying the amplitude of the fourth peak, which is the second of the multiple peaks of the second residual vibration, by a second coefficient smaller than the first coefficient. In aspect 7 as well, the ejection stability can be evaluated with high accuracy in accordance with the conditions of use of the liquid ejection head. Furthermore, according to aspect 7, the ejection stability can be evaluated with high accuracy compared to when the ejection stability is evaluated based only on the amplitude of the first peak of the first residual vibration.

[0208] In a liquid ejection device according to aspect 8, which is a specific example of any one of aspects 1 to 7, the control unit causes the detection unit to detect the residual vibration resulting from performing the ejection drive only once as a second residual vibration, and further performs a second evaluation to evaluate the ejection state of the nozzle based on the second residual vibration detected by the detection unit. According to the eighth aspect, the ejection state of the nozzle can be appropriately and easily evaluated using the second residual vibration.

[0209] In a liquid ejection device according to aspect 9, which is a specific example of any one of aspects 1 to 8, the control unit uses one of a plurality of drive signal candidates having different waveforms for ejecting liquid from the nozzle as the drive signal, performs the first evaluation on each of the plurality of drive signal candidates, and identifies, from among the plurality of drive signal candidates, a drive signal candidate that will result in stable ejection of liquid from the nozzle and a drive signal candidate that will result in unstable ejection of liquid from the nozzle. According to the ninth aspect, by determining the waveform of the drive signal as a candidate waveform of the drive signal that stabilizes the ejection of liquid from the nozzle, the waveform of the drive signal that drives the piezoelectric element can be determined appropriately and easily.

[0210] In a liquid ejection device according to aspect 10, which is a specific example of any one of aspects 1 to 9, the control unit causes the detection unit to detect the residual vibration resulting from performing the ejection drive 10 or more times in succession in the first evaluation as the first residual vibration. In the tenth aspect as well, the stability of the liquid ejection from the nozzle can be appropriately and easily evaluated.

[0211] Furthermore, a liquid ejection device according to aspect 11, which is another preferred aspect, comprises a liquid ejection head including a nozzle for ejecting liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when driven by the piezoelectric element, and a detection unit that detects residual vibration of the vibration plate caused by driving the piezoelectric element, and a control unit, wherein the control unit causes the detection unit to detect the residual vibration caused by multiple repetitions of an ejection drive that drives the piezoelectric element with a drive signal that ejects liquid from the nozzle as a first residual vibration, and determines the waveform of the drive signal based on the first residual vibration detected by the detection unit. According to the eleventh aspect, the waveform of the drive signal for driving the piezoelectric element can be determined appropriately and easily.

[0212] Furthermore, a control method for a liquid ejection device according to a preferred aspect 12 is a control method for a liquid ejection device having a liquid ejection head including a nozzle for ejecting liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when driven by the piezoelectric element, and a detection unit that detects residual vibration of the vibration plate caused by driving the piezoelectric element, wherein the detection unit detects the residual vibration caused by multiple repetitions of an ejection drive that drives the piezoelectric element with a drive signal to eject liquid from the nozzle as a first residual vibration, and evaluates the stability of the ejection of liquid from the nozzle based on the first residual vibration detected by the detection unit. According to the twelfth aspect, the stability of the liquid ejection from the nozzle can be appropriately and easily evaluated without requiring external factors such as an imaging environment.

[0213] Furthermore, a control method for a liquid ejection device according to aspect 13, which is another preferred aspect, is a control method for a liquid ejection device having a liquid ejection head including a nozzle for ejecting liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when driven by the piezoelectric element, and a detection unit that detects residual vibration of the vibration plate caused by driving the piezoelectric element, wherein the detection unit detects the residual vibration caused by repeated ejection drive of driving the piezoelectric element with a drive signal that ejects liquid from the nozzle as a first residual vibration, and determines the waveform of the drive signal based on the first residual vibration detected by the detection unit. According to the thirteenth aspect, the waveform of the drive signal for driving the piezoelectric element can be determined appropriately and easily. [Explanation of symbols]

[0214] 1...liquid ejection head, 2...drive signal generation unit, 3...analysis unit, 4...control unit, 5...storage unit, 7...maintenance unit, 8...medium transport mechanism, 9...carriage transport mechanism, 10...recording head, 18...switching circuit, 19...detection circuit, 40...evaluation control unit, 60...ink container, 100...liquid ejection device, CV...pressure chamber, D...ejection unit, N...nozzle, PP...medium, PZ...piezoelectric element.

Claims

1. a liquid ejection head including a nozzle for ejecting a liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when the piezoelectric element is driven, and a detection unit that detects residual vibration of the vibration plate caused by the driving of the piezoelectric element; a control unit that performs a first evaluation that evaluates the stability of ejection of liquid from the nozzle; Equipped with The control unit In the first evaluation, the residual vibration caused by continuously executing an ejection drive that drives the piezoelectric element with a drive signal that ejects liquid from the nozzle is detected by the detection unit as a first residual vibration, and the stability of the ejection of liquid from the nozzle is evaluated based on the first residual vibration detected by the detection unit. A liquid ejection device characterized by:

2. The control unit In the first evaluation, stability of ejection of liquid from the nozzle is evaluated based on the amplitude of at least one peak among the plurality of peaks of the first residual vibration. The liquid ejection device according to claim 1 .

3. The control unit If, in the first evaluation, the amplitude of a first peak among the plurality of peaks of the first residual vibration is greater than a first threshold value, it is determined that the ejection of liquid from the nozzle is unstable.

3. The liquid ejection device according to claim 2.

4. The control unit If, in the first evaluation, the amplitude of a second peak among the plurality of peaks of the first residual vibration is greater than a second threshold value, it is determined that the ejection of liquid from the nozzle is unstable.

4. The liquid ejection device according to claim 3.

5. The control unit In the first evaluation, if the amplitude of the first peak is equal to or less than the first threshold value and the amplitude of the second peak is equal to or less than the second threshold value, it is determined that the ejection of liquid from the nozzle is stable.

5. The liquid ejection device according to claim 4.

6. The control unit causing the detection unit to detect the residual vibration resulting from executing the ejection driving only once as a second residual vibration; a value based on the amplitude of a first third peak among the plurality of peaks of the second residual vibration is used as the first threshold value; 4. The liquid ejection device according to claim 3.

7. The control unit causing the detection unit to detect the residual vibration resulting from executing the ejection driving only once as a second residual vibration; a value obtained by multiplying the amplitude of a third peak, which is a first peak among the plurality of peaks of the second residual vibration, by a first coefficient is used as the first threshold value; a value obtained by multiplying the amplitude of a second, fourth peak among the plurality of peaks of the second residual vibration by a second coefficient smaller than the first coefficient is used as the second threshold value; 5. The liquid ejection device according to claim 4.

8. The control unit causing the detection unit to detect the residual vibration resulting from executing the ejection drive only once as a second residual vibration, and further performing a second evaluation to evaluate the ejection state of the nozzle based on the second residual vibration detected by the detection unit. The liquid ejection device according to claim 1 .

9. The control unit one drive signal candidate among a plurality of drive signal candidates having different waveforms for ejecting liquid from the nozzle is used as the drive signal, and the first evaluation is performed for each of the plurality of drive signal candidates; identifying, from the plurality of drive signal candidates, drive signal candidates that will stabilize the ejection of liquid from the nozzles and drive signal candidates that will unstable the ejection of liquid from the nozzles; The liquid ejection device according to claim 1 .

10. The control unit In the first evaluation, the residual vibration resulting from the ejection driving being performed 10 or more times in succession is detected by the detection unit as the first residual vibration. The liquid ejection device according to claim 1 .

11. a liquid ejection head including a nozzle for ejecting a liquid, a piezoelectric element corresponding to the nozzle, a vibration plate that vibrates when the piezoelectric element is driven, and a detection unit that detects residual vibration of the vibration plate caused by the driving of the piezoelectric element; A control unit; Equipped with The control unit causing the detection unit to detect, as a first residual vibration, the residual vibration resulting from a plurality of repetitions of ejection driving in which the piezoelectric element is driven by a drive signal that ejects liquid from the nozzle; determining a waveform of the drive signal based on the first residual vibration detected by the detection unit; A liquid ejection device characterized by:

12. A control method for a liquid ejection device having a liquid ejection head including nozzles that eject liquid, piezoelectric elements corresponding to the nozzles, a vibration plate that vibrates when the piezoelectric elements are driven, and a detection unit that detects residual vibration of the vibration plate caused by the driving of the piezoelectric elements, causing the detection unit to detect, as a first residual vibration, the residual vibration resulting from a plurality of repetitions of ejection driving in which the piezoelectric element is driven by a drive signal that ejects liquid from the nozzle; evaluating the stability of the ejection of the liquid from the nozzle based on the first residual vibration detected by the detection unit; A method for controlling a liquid ejection device.

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