Liquid ejection device and head unit

Abstract

The present application provides a liquid ejection device and a head unit that determine whether or not a foreign matter is attached to an inner wall of a nozzle opening. The liquid ejection device is characterized by including: a supply unit that can selectively supply a first drive signal and a second drive signal to a piezoelectric element, the first drive signal being a signal that drives the piezoelectric element to eject a liquid from a nozzle opening to form an image on a medium, the second drive signal being a signal that drives the piezoelectric element to determine whether or not a foreign matter is attached to an inner wall of the nozzle opening; and a determination unit that determines whether or not a foreign matter is attached to the inner wall, the second drive signal including: a first partial signal that changes from a first potential to a second potential; and a second partial signal that changes from the second potential to the first potential, the determination unit determining whether or not a foreign matter is attached to the inner wall based on a vibration generated in the piezoelectric element after the first partial signal is supplied to the piezoelectric element and the second partial signal is supplied.

Description

TECHNICAL FIELD

[0001] The present application relates to a liquid ejecting apparatus and a head unit. BACKGROUND

[0002] A liquid ejecting apparatus such as an inkjet printer forms an image on a medium such as a recording sheet by ejecting a liquid such as ink filled in an ejecting portion from a nozzle opening provided in the ejecting portion, using a piezoelectric element provided in the ejecting portion, which is driven by a drive signal. In such a liquid ejecting apparatus, the nozzle opening is sometimes clogged due to thickening of the liquid filled in the ejecting portion, and the like, resulting in an ejection abnormality in which the liquid cannot be normally ejected from the nozzle opening. Also, when the ejection abnormality occurs, a predetermined dot formed on the medium by the liquid ejected from the ejecting portion cannot be normally formed, resulting in a decrease in the quality of the image formed on the medium. In Patent Literature 1, a technique is proposed in which it is determined whether or not there is an ejection abnormality in the ejecting portion, based on a characteristic of a vibration generated in the piezoelectric element driven by the drive signal, in order to prevent a decrease in the quality accompanying the ejection abnormality.

[0003] Patent Literature 1: Japanese Patent Application Publication No. 2015-058540 SUMMARY

[0004] However, in the case where the ejection abnormality occurs due to the foreign matter adhering to the inner wall of the nozzle opening in the related art, the influence on the characteristic of the vibration generated in the piezoelectric element driven by the drive signal is slight, and thus there is a problem in that it is not possible to determine whether or not there is an ejection abnormality in the ejecting portion.

[0005] To solve the above technical problem, the liquid ejecting apparatus according to the present application is characterized by including: a supply portion that can selectively supply a first drive signal and a second drive signal to a piezoelectric element, the first drive signal being a signal that drives the piezoelectric element to eject a liquid from a nozzle opening to form an image on a medium, the second drive signal being a signal that drives the piezoelectric element to determine whether or not there is a foreign matter adhering to an inner wall of the nozzle opening; and a determination portion that determines whether or not there is the foreign matter adhering to the inner wall, the second drive signal including: a first partial signal that changes from a first potential to a second potential; and a second partial signal that changes from the second potential to the first potential, the determination portion determining whether or not there is the foreign matter adhering to the inner wall, based on a vibration generated in the piezoelectric element after the first partial signal is supplied to the piezoelectric element and then the second partial signal is supplied.

[0006] Further, the head unit according to the present application is characterized by including: a supply unit that is capable of selectively supplying a first drive signal and a second drive signal to a piezoelectric element, the first drive signal being a signal that drives the piezoelectric element to eject liquid from a nozzle opening to form an image on a medium, the second drive signal being a signal that drives the piezoelectric element to determine whether or not a foreign matter is attached to an inner wall of the nozzle opening; and a determination unit that determines whether or not a foreign matter is attached to the inner wall, the second drive signal including: a first partial signal that changes from a first potential to a second potential; and a second partial signal that changes from the second potential to the first potential, the determination unit determining whether or not a foreign matter is attached to the inner wall based on a vibration generated in the piezoelectric element after the first partial signal is supplied to the piezoelectric element and the second partial signal is supplied to the piezoelectric element. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a block diagram showing an example of the configuration of the inkjet printer 1 to which the embodiment of the present application relates.

[0008] Figure 2 is a perspective view showing an example of the schematic internal structure of the inkjet printer 1.

[0009] Figure 3 is a sectional view for explaining an example of the structure of the ejection section D[m].

[0010] Figure 4 is a block diagram showing an example of the configuration of the drive signal generation circuit 4R.

[0011] Figure 5 is a block diagram showing an example of the configuration of the head unit 3.

[0012] Figure 6 is a timing chart for explaining an example of the signals supplied to the head unit 3.

[0013] Figure 7 is a timing chart for explaining an example of the drive signal Com-B.

[0014] Figure 8 is an explanatory diagram for explaining an example of the individually designated signal Sd[m].

[0015] Figure 9 is a timing chart for explaining an example of the drive signal Com-Bw.

[0016] Figure 10 is a timing chart for explaining an example of the drive signal Com-Bz.

[0017] Figure 11 is a sectional view for explaining an example of the ejection abnormality of the first mode.

[0018] Figure 12 is a cross-sectional view for explaining one example of the ejection abnormality of the second mode.

[0019] Figure 13 is a cross-sectional view for explaining the period TC detected in the verification example 1.

[0020] Figure 14 is a cross-sectional view for explaining the period TC detected in the verification example 1.

[0021] Figure 15 is a cross-sectional view for explaining the period TC detected in the verification example 2.

[0022] Figure 16 is a cross-sectional view for explaining the period TC detected in the verification example 2.

[0023] Figure 17 is a timing chart for explaining one example of the drive signal Com-B involved in the modification example 1.

[0024] Figure 18 is a timing chart for explaining one example of the drive signal Com-B involved in the modification example 2.

[0025] Figure 19 is a block diagram showing one example of the configuration of the inkjet printer 1A involved in the modification example 3.

[0026] Explanation of Reference Numerals

[0027] 1... inkjet printer, 2... control unit, 3... head unit, 4... drive signal generation unit, 7... conveyance unit, 8... determination unit, 31... supply circuit, 32... recording head, 33... detection circuit, D... ejection portion, N... nozzle opening, NH... inner wall. DETAILED DESCRIPTION

[0028] Embodiments for carrying out the present application will be explained below with reference to the drawings. In each drawing, the size and the scale of each portion are appropriately made different from the actual size and scale. In addition, the embodiments explained below are preferred specific examples of the present application, and various limitations that are technically preferred are added, but the scope of the present application is not limited to these embodiments as long as the present application is not particularly limited in the following explanation.

[0029] A. Embodiments

[0030] In the present embodiment, an inkjet printer that forms an image on a recording sheet PP by ejecting ink is shown, and a liquid ejection device is explained.

[0031] 1. Outline of Inkjet Printer

[0032] The following explanation will be made with reference toFigures 1 to 3 An example of the configuration of the inkjet printer 1 according to the present embodiment will be described.

[0033] Figure 1 is a functional block diagram showing an example of the configuration of the inkjet printer 1.

[0034] As shown in Figure 1 , print data Img indicating an image to be formed by the inkjet printer 1 is supplied from a host computer such as a personal computer or a digital camera to the inkjet printer 1. The inkjet printer 1 performs a printing process of forming the image indicated by the print data Img supplied from the host computer on a recording sheet PP.

[0035] As shown in Figure 1 , the inkjet printer 1 includes a control unit 2 that controls each unit of the inkjet printer 1, a head unit 3 that is provided with a discharge portion D that discharges ink, a drive signal generation unit 4 that generates a drive signal Com for driving the discharge portion D, a conveyance unit 7 that changes a relative position of the recording sheet PP with respect to the head unit 3, and a determination unit 8 that determines a discharge state of the ink in the discharge portion D. Further, the inkjet printer 1 is an example of a "liquid discharge apparatus", the ink is an example of a "liquid", the recording sheet PP is an example of a "medium", the drive signal generation unit 4 is an example of a "generation unit", and the determination unit 8 is an example of a "determination unit".

[0036] In the present embodiment, it is assumed that the inkjet printer 1 includes one or a plurality of head units 3, one or a plurality of drive signal generation units 4 corresponding to the one or a plurality of head units 3, and one or a plurality of determination units 8 corresponding to the one or a plurality of head units 3. Specifically, in the present embodiment, it is assumed that the inkjet printer 1 includes four head units 3, four drive signal generation units 4 corresponding to the four head units 3, and four determination units 8 corresponding to the four head units 3. However, for convenience of explanation, as shown in Figure 1 , an explanation will be given below focusing on one of the four head units 3, one of the four drive signal generation units 4 corresponding to the one head unit 3, and one of the four determination units 8 corresponding to the one head unit 3.

[0037] The control unit 2 is configured to include one or more CPUs. However, the control unit 2 can also have a programmable logic device such as an FPGA in place of or in addition to the CPU. Here, CPU is an abbreviation for Central Processing Unit, and FPGA is an abbreviation for field-programmable gate array. In addition, the control unit 2 includes a memory. The memory 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).

[0038] The control unit 2 generates a print signal SI and a waveform designation signal dCom and the like for controlling the operation of each part of the inkjet printer 1, the details of which are described later.

[0039] Here, the waveform designation signal dCom is a digital signal that specifies the waveform of the drive signal Com. In addition, the drive signal Com is an analog signal for driving the ejection section D.

[0040] In the present embodiment, it is assumed that the drive signal Com includes a drive signal Com-A and a drive signal Com-B. In the present embodiment, the drive signal Com-A is an example of a "first drive signal", and the drive signal Com-B is an example of a "second drive signal".

[0041] In addition, in the present embodiment, it is assumed that the waveform designation signal dCom includes a waveform designation signal dCom-A that specifies the waveform of the drive signal Com-A and a waveform designation signal dCom-B that specifies the waveform of the drive signal Com-B.

[0042] The drive signal generation unit 4 includes a DA conversion circuit and generates a drive signal Com having a waveform specified by the waveform designation signal dCom. Specifically, the drive signal generation unit 4 has a drive signal generation circuit 4A that generates a drive signal Com-A in accordance with the waveform designation signal dCom-A and a drive signal generation circuit 4B that generates a drive signal Com-B in accordance with the waveform designation signal dCom-B.

[0043] Furthermore, in the following text, drive signal Com-A and drive signal Com-B are sometimes collectively referred to as drive signal Com-R. Additionally, in the following text, drive signal generation circuit 4A and drive signal generation circuit 4B are sometimes collectively referred to as drive signal generation circuit 4R. That is, in this embodiment, drive signal generation unit 4 includes two drive signal generation circuits 4R: drive signal generation circuit 4A and drive signal generation circuit 4B. Furthermore, in the following text, waveform specification signal dCom-A and waveform specification signal dCom-B are sometimes collectively referred to as waveform specification signal dCom-R. Waveform specification signal dCom-R defines the waveform of drive signal Com-R. That is, drive signal generation circuit 4R generates drive signal Com-R based on waveform specification signal dCom-R.

[0044] Furthermore, the printing signal SI is a digital signal that specifies the type of operation of the ejector section D. Specifically, the printing signal SI specifies the type of operation of the ejector section D by indicating whether or not a drive signal Com is supplied to the ejector section D.

[0045] like Figure 1 As shown, the head unit 3 includes a supply circuit 31, a recording head 32, and a detection circuit 33.

[0046] The recording head 32 has M ejector sections D. Here, the value M is a natural number satisfying "M≥1". Furthermore, in the following text, the m-th ejector section D among the M ejector sections D provided in the recording head 32 is sometimes referred to as ejector section D[m]. Here, the variable m is a natural number satisfying "1≤m≤M". Additionally, when a component or signal of the inkjet printer 1 corresponds to an ejector section D[m] among the M ejector sections D, the reference numeral [m] used to represent that component or signal is sometimes marked with a footnote in the accompanying drawings.

[0047] The supply circuit 31 switches whether to supply the drive signal Com to the ejector section D[m] according to the printing signal SI. Furthermore, the supply circuit 31 is an example of a "supply section". In the following text, the drive signal Com supplied to the ejector section D[m] is sometimes referred to as the supply drive signal Vin[m].

[0048] Furthermore, the supply circuit 31 switches between supplying a detection potential signal VX[m] to the detection circuit 33 based on the printing signal SI. This detection potential signal VX[m] represents the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] provided on the ejector section D[m]. In the following text, when the detection potential signal VX[m] is supplied to the detection circuit 33 from the ejector section D[m], the ejector section D[m] is sometimes referred to as the target ejector section DH. Furthermore, regarding the piezoelectric element PZ[m] and the upper electrode Zu[m], further details will follow... Figure 3 The description is in the middle.

[0049] The detection circuit 33 generates the detection signal SK[m] based on the detection potential signal VX[m] supplied from the discharge portion D[m] as the determination target discharge portion DH via the supply circuit 31. Specifically, the detection circuit 33 generates the detection signal SK[m] by, for example, amplifying the detection potential signal VX[m] and removing noise components.

[0050] The determination unit 8 determines whether the discharge state of the ink in the discharge portion D is normal based on the detection signal SK[m]. In other words, the determination unit 8 determines whether it is a state in which no discharge abnormality occurs in the discharge portion D based on the detection signal SK[m]. Then, the determination unit 8 generates determination information JH[m] indicating the result of the determination. Here, the discharge abnormality is a general term for a state in which the ink cannot be normally discharged from the nozzle opening N provided in the discharge portion D. For example, the discharge abnormality includes a state in which the ink cannot be discharged from the discharge portion D[m], a state in which the discharge portion D[m] discharges the ink in an amount different from the discharge amount of the ink specified by the drive signal Com, and a state in which the discharge portion D[m] discharges the ink at a speed different from the discharge speed of the ink specified by the drive signal Com, and the like. Hereinafter, the process of determining the discharge state of the discharge portion D[m] based on the detection signal SK[m] will be referred to as a discharge state determination process.

[0051] In addition, hereinafter, the process of driving the discharge portion D[m] as the determination target discharge portion DH and detecting the detection potential signal VX[m] from the discharge portion D[m], and generating the detection signal SK[m] based on the detected detection potential signal VX[m] will be referred to as a determination target drive process.

[0052] When the determination target drive process is executed, the control unit 2 generates a signal for controlling the head unit 3 such as the print signal SI. In addition, when the determination target drive process is executed, the control unit 2 generates a signal for controlling the drive signal generation unit 4 such as the waveform designation signal dCom. Thus, in the determination target drive process, the control unit 2 drives the discharge portion D[m] as the determination target discharge portion DH. Also, in the determination target drive process, the detection circuit 33 generates the detection signal SK[m] based on the detection potential signal VX[m] detected from the discharge portion D[m] driven as the determination target discharge portion DH.

[0053] Further, as described above, the inkjet printer 1 executes a print process. At the time of executing the print process, the control unit 2 generates a signal for controlling the head unit 3, such as a print signal SI, in accordance with print data Img. In addition, at the time of executing the print process, the control unit 2 generates a signal for controlling the drive signal generation unit 4, such as a waveform designation signal dCom. In addition, at the time of executing the print process, the control unit 2 generates a signal for controlling the conveyance unit 7. Thereby, in the print process, the control unit 2 controls the conveyance unit 7 to change the relative position of the recording paper PP with respect to the head unit 3, and controls each part of the inkjet printer 1 to adjust whether or not to eject ink from the ejection portion D[m], the amount of ink to be ejected, and the timing of ejection of ink, and so on, thereby forming an image corresponding to the print data Img on the recording paper PP.

[0054] Figure 2 is a perspective view showing an example of the schematic internal structure of the inkjet printer 1.

[0055] As shown in Figure 2 , in the present embodiment, it is assumed that the inkjet printer 1 is a serial printer. Specifically, at the time of executing the print process, the inkjet printer 1 conveys the recording paper PP in the X1 direction while reciprocating the head unit 3 in the Y1 direction intersecting the X1 direction and the Y2 direction which is the opposite direction of the Y1 direction, and ejects ink from the ejection portion D[m], thereby forming a dot Dt corresponding to the print data Img on the recording paper PP.

[0056] Hereinafter, the X1 direction and the X2 direction which is the opposite direction thereof will be collectively referred to as the "X-axis direction", the Y1 direction and the Y2 direction which is the opposite direction thereof will be collectively referred to as the "Y-axis direction", and the Z1 direction and the Z2 direction which is the opposite direction thereof will be collectively referred to as the "Z-axis direction". In the present embodiment, as an example, it is assumed that the X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other. However, the present application is not limited to such a mode. The X-axis direction, the Y-axis direction, and the Z-axis direction can be merely intersected with each other. Further, in the present embodiment, it is assumed that the Z1 direction is the direction in which ink is ejected from the ejection portion D[m].

[0057] As shown in Figure 2 , the inkjet printer 1 related to the present embodiment is provided with a housing 100 and a carriage 110 which is capable of reciprocating in the Y-axis direction within the housing 100, and mounts four head units 3.

[0058] In the present embodiment, as shown in Figure 2As shown, it is assumed that the carriage 110 houses four ink cartridges 120, each corresponding to one of the four colors of ink: cyan, magenta, yellow, and black. In this embodiment, as described above, it is assumed that the inkjet printer 1 has four head units 3, each corresponding to one of the four ink cartridges 120. Each ejector section D[m] receives ink from the ink cartridge 120 corresponding to the head unit 3 on which the ejector section D[m] is located. Thus, each ejector section D[m] can fill its interior with the supplied ink and eject the filled ink from the nozzle opening N. Furthermore, the ink cartridges 120 may also be located outside the carriage 110.

[0059] Furthermore, as described above, the inkjet printer 1 according to this embodiment includes a transport unit 7. For example... Figure 2 As shown, the transport unit 7 includes: a carriage transport mechanism 71 for reciprocating the carriage 110 in the Y-axis direction; a carriage guide shaft 76 for supporting the carriage 110 to reciprocate freely in the Y-axis direction; a media transport mechanism 73 for transporting recording paper PP; and an impression plate 75 disposed in the Z1 direction of the carriage 110. Therefore, during printing, the transport unit 7 uses the carriage transport mechanism 71 to cause the head unit 3 and the carriage 110 to reciprocate together along the carriage guide shaft 76 in the Y-axis direction, and uses the media transport mechanism 73 to transport the recording paper PP on the impression plate 75 in the X1 direction, thereby changing the relative position of the recording paper PP with respect to the head unit 3, so that the ink can be applied to the entire recording paper PP.

[0060] Figure 3 This is a schematic partial cross-sectional view of the recording head 32 obtained by cutting the recording head 32 in a manner including the ejection part D[m].

[0061] like Figure 3As shown, the ejector section D[m] includes a piezoelectric element PZ[m], a chamber CV filled with ink, a nozzle opening N communicating with the chamber CV, and a vibrating plate 321. The ejector section D[m] drives the piezoelectric element PZ[m] using a supply drive signal Vin[m], thereby ejecting the ink in the chamber CV from the nozzle opening N. The chamber CV is a space divided by a chamber plate 324, a nozzle plate 323 forming the nozzle opening N, and a vibrating plate 321. The chamber CV is connected to a storage tank 325 via an ink supply port 326. The storage tank 325 is connected to an ink cartridge 120 corresponding to the ejector section D[m] via an ink inlet 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric element Zm[m] disposed between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is electrically connected to the power supply line LD, which is set to a predetermined potential VBS. Furthermore, when a supply drive signal Vin[m] is supplied to the upper electrode Zu[m], applying a voltage between the upper electrode Zu[m] and the lower electrode Zd[m], the piezoelectric element PZ[m] is displaced in the Z1 or Z2 direction according to the applied voltage, resulting in the piezoelectric element PZ[m] vibrating. The vibrating plate 321 engages with the lower electrode Zd[m]. Therefore, when the piezoelectric element PZ[m] vibrates under the drive of the supply drive signal Vin[m], the vibrating plate 321 also vibrates. Then, the vibration of the vibrating plate 321 causes changes in the volume and pressure within the chamber CV, thereby causing the ink filled in the chamber CV to be ejected from the nozzle opening N.

[0062] 2. Drive signal generation unit

[0063] As described above, the drive signal generation unit 4 includes two drive signal generation circuits 4R: a drive signal generation circuit 4A and a drive signal generation circuit 4B. Referring below... Figure 4 A brief description of the drive signal generation circuit 4R in the drive signal generation unit 4 is provided.

[0064] Figure 4 This is a diagram illustrating an example of the circuit configuration of the drive signal generation circuit 4R.

[0065] like Figure 4 As shown, the drive signal generation circuit 4R includes an integrated circuit 40, an amplifier circuit 41, a smoothing circuit 42, a pull-up circuit 43, and a filter circuit 44, and generates a drive signal Com-R based on the waveform specified signal dCom-R.

[0066] The integrated circuit 40, which is, for example, an LSI, that is, a Large Scale Integration, generates the gate signal SGH and the gate signal SGL from the waveform designation signal dCom-R. The integrated circuit 40 includes an analog conversion circuit 402, a subtracter 404, an adder 406, an attenuator 408, an integral attenuator 412, a comparator 420, and a gate driver 430.

[0067] The analog conversion circuit 402 is a DAC, that is, a digital to analog converter, which converts the digital waveform designation signal dCom-R into an analog signal Aa. Further, the voltage amplitude of the signal Aa is, for example, about 0 to 2 volts, and a signal amplified to about 20 times the voltage becomes the drive signal Com-R. That is, the signal Aa is a signal before the drive signal Com-R is amplified. The integral attenuator 412 outputs a signal Ax which is an integral of an attenuation of a signal SN1 input to a terminal Tn1 described later.

[0068] The subtracter 404 outputs a signal Ab which indicates a potential obtained by subtracting the potential of the signal Aa from the potential of the signal Ax.

[0069] The attenuator 408 outputs a signal Ay which is an attenuation of a high frequency component of a signal SN2 input to a terminal Tn2 described later.

[0070] The adder 406 outputs a signal As which indicates a potential obtained by adding the potential of the signal Ab to the potential of the signal Ay.

[0071] The comparator 420 outputs a modulation signal Ms which is a pulse modulation of the signal As. Specifically, the comparator 420 outputs a modulation signal Ms in which the signal As becomes an H level when the signal As reaches a threshold voltage Vthl or more in a voltage rise, and the signal As becomes an L level when the signal As is lower than a threshold voltage Vth2 in a voltage fall. Further, the threshold voltage Vthl and the threshold voltage Vth2 are set to a relationship of "Vthl > Vth2".

[0072] Further, the power supply voltage of the circuit from the analog conversion circuit 402 to the comparator 420 is, for example, a low voltage of 3.3 volts or the like. In contrast, the drive signal Com-R is a large amplitude, and, for example, sometimes exceeds 40 volts. Therefore, in the integral attenuator 412, the signal SN1 having an amplitude corresponding to the drive signal Com-R is attenuated, so that the amplitude range of the signal Ax is matched to the amplitude range of the signal in the circuit from the analog conversion circuit 402 to the comparator 420.

[0073] Further, in the present embodiment, a digital signal is exemplified as the waveform designation signal dCom-R, but the waveform designation signal dCom-R can be, for example, an analog signal Aa as long as it is a signal that specifies a target value when generating the drive signal Com-R. In the case where the signal Aa is the waveform designation signal dCom-R, the integrated circuit 40 can be configured not to include the analog conversion circuit 402.

[0074] The gate driver 430 outputs, to the terminal TnH, a gate signal SGH that is a signal obtained by converting the modulation signal Ms into a specific amplitude. Further, the gate driver 430 outputs, to the terminal TnL, a gate signal SGL that is a signal obtained by converting, into a specific amplitude, a signal that inverts the logic level of the modulation signal Ms.

[0075] The amplification circuit 41 includes, for example, a transistor TrH and a transistor TrL, and generates, from the gate signal SGH and the gate signal SGL output from the integrated circuit 40, an amplification signal Az that is a signal obtained by amplifying the modulation signal Ms. Further, in the present embodiment, it is assumed, as an example, that the transistor TrH and the transistor TrL are N-channel type field effect transistors (FETs).

[0076] The gate signal SGH output from the gate driver 430 is input to the gate electrode of the transistor TrH via the terminal TnH and a resistor RGH.

[0077] The gate signal SGL output from the gate driver 430 is input to the gate electrode of the transistor TrL via the terminal TnL and a resistor RGL. The logic levels of the gate signal SGH and the gate signal SGL are in an exclusive relationship with each other.

[0078] Here, the "exclusive relationship" means that the signal level of the gate signal SGH supplied to the gate electrode of the transistor TrH and the signal level of the gate signal SGL supplied to the gate electrode of the transistor TrL do not become high at the same time, in other words, the transistor TrH and the transistor TrL do not conduct at the same time. Further, the transistor TrH conducts when the gate electrode of the transistor TrH is high, and turns off when the gate electrode of the transistor TrH is low. Further, the transistor TrL conducts when the gate electrode of the transistor TrL is high, and turns off when the gate electrode of the transistor TrL is low.

[0079] The drain electrode of the transistor TrH is electrically connected to a power supply line set to a high potential side power supply potential VHH, and the source electrode is electrically connected to the node Nd.

[0080] The source electrode of the transistor TrL is electrically connected to a power supply line set to a low potential side power supply potential VLL, and the drain electrode is electrically connected to the node Nd. Further, the potential VLL is a potential lower than the potential VHH. The potential VLL can be, for example, a ground potential, or can be the same potential as the potential VBS.

[0081] As described above, the transistor TrH is turned on when the gate signal SGH supplied to the gate electrode is at a high level, and is turned off when the gate signal SGH is at a low level. Further, the transistor TrL is turned on when the gate signal SGL supplied to the gate electrode is at a high level, and is turned off when the gate signal SGL is at a low level. Therefore, the node Nd, at which the source electrode of the transistor TrH and the drain electrode of the transistor TrL are electrically connected, outputs an amplified signal Az in which the modulated signal Ms is amplified.

[0082] The smoothing circuit 42 is an LPF (Low Pass Filter), and smoothes the amplified signal Az to generate the drive signal Com-R. The smoothing circuit 42 includes an inductor L0 and a capacitor C0. One end of the inductor L0 is electrically connected to the node Nd, and the other end is electrically connected to the output terminal Tn-out. One end of the capacitor C0 is electrically connected to the output terminal Tn-out, and the other end is electrically connected to a power supply line set to the potential VLL. The drive signal Com-R in which the amplified signal Az is smoothed is output from the output terminal Tn-out.

[0083] The pull-up circuit 43 feeds back a signal SN1, which is a signal in which the drive signal Com-R output to the output terminal Tn-out is pulled up, to the terminal Tn1. The pull-up circuit 43 includes a resistor R1 and a resistor R2. One end of the resistor R1 is electrically connected to the output terminal Tn-out, and the other end is electrically connected to the terminal Tn1. One end of the resistor R2 is electrically connected to the terminal Tn1, and the other end is electrically connected to a power supply line set to the potential VHH.

[0084] The filter circuit 44 is a BPF (Band Pass Filter), and feeds back a signal SN2, which is a signal in which a direct current component is removed from a frequency component of a predetermined bandwidth in the drive signal Com-R, to the terminal Tn2. The filter circuit 44 includes a resistor R3, a capacitor C1 having one end electrically connected to the output terminal Tn-out and the other end electrically connected to one end of the resistor R3, a resistor R4 having one end electrically connected to one end of the resistor R3 and the other end electrically connected to a power supply line set to the potential VLL, a control unit 2 having one end electrically connected to the other end of the resistor R3 and the other end electrically connected to a power supply line set to the potential VLL, and a capacitor C3 having one end electrically connected to the other end of the resistor R3 and the other end electrically connected to the terminal Tn2.

[0085] The capacitor Cl and the resistor R4 function as an HPF (High Pass Filter) that passes high frequency components above a cutoff frequency in the drive signal Com-R. The resistor R3 and the capacitor C2 function as an LPF (Low Pass Filter) that passes low frequency components below a cutoff frequency in the drive signal Com-R. In this embodiment, the cutoff frequency of the HPF is set lower than the cutoff frequency of the LPF in the filter circuit 44. Therefore, the filter circuit 44 passes frequency components of a predetermined bandwidth above the cutoff frequency of the HPF and below the cutoff frequency of the LPF in the drive signal Com-R. In addition, since the filter circuit 44 includes the capacitor C3, a signal in which a direct current component is removed from the signal passing through the predetermined bandwidth of the HPF and the LPF in the drive signal Com-R is fed back to the terminal Tn2.

[0086] Thus, the drive signal generation circuit 4R generates the drive signal Com-R by smoothing the amplified signal Az in the node Nd by the smoothing circuit 42. The drive signal Com-R is fed back to the subtracter 404 after being integrated and subjected to a subtraction operation by the integration attenuator 412. Therefore, self-oscillation is performed at a frequency determined by the transfer functions of the delay in the smoothing circuit 42, the delay in the integration attenuator 412, and the feedback. However, since the amount of delay in the feedback path via the terminal Tnl is large, the frequency of the self-oscillation cannot be increased to a degree at which the accuracy of the waveform of the drive signal Com-R can be sufficiently ensured in the case of feedback via only the terminal Tnl. In contrast, in this embodiment, since the path for feeding back the high frequency components of the drive signal Com-R via the terminal Tn2 is provided independently of the path via the terminal Tnl, the delay of the feedback in the entire drive signal generation circuit 4R can be reduced. That is, in this embodiment, the frequency of the signal As, which is the signal Ab to which the signal Ay, which is the high frequency component of the drive signal Com-R, is added, can be increased compared to the case where the path via the terminal Tn2 is not present, and thus the accuracy of the drive signal Com-R can be sufficiently ensured.

[0087] 3. Outline of head unit

[0088] The following description will be given with reference to Figures 5 to 8 An outline of the head unit 3 will be described.

[0089] Figure 5 is a block diagram showing an example of the configuration of the head unit 3.

[0090] As Figure 5As shown, the head unit 3 includes a supply circuit 31, a recording head 32, and a detection circuit 33. In addition, the head unit 3 includes a wiring LA supplied with a drive signal Com-A from a drive signal generation circuit 4A provided in the drive signal generation unit 4, a wiring LB supplied with a drive signal Com-B from a drive signal generation circuit 4B provided in the drive signal generation unit 4, and a wiring LS for supplying a detection potential signal VX[m] to the detection circuit 33.

[0091] As shown, the supply circuit 31 includes M switches Wa[l]-Wa[M] corresponding to the M ejection portions D[l]-D[M], M switches Wb[l]-Wb[M] corresponding to the M ejection portions D[l]-D[M], M switches Ws[l]-Ws[M] corresponding to the M ejection portions D[l]-D[M], and a connection state designating circuit 310 that designates the connection state of each switch. Figure 5

[0092] The connection state designating circuit 310 generates a connection state designating signal Qa[m] that designates the on-off of the switch Wa[m], a connection state designating signal Qb[m] that designates the on-off of the switch Wb[m], and a connection state designating signal Qs[m] that designates the on-off of the switch Ws[m], based on a print signal SI, a latch signal LAT, a conversion signal CH, and a period designating signal Tsig supplied from the control unit 2.

[0093] The switch Wa[m] switches the on-off of the wiring LA and the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designating signal Qa[m]. In the present embodiment, the switch Wa[m] is on when the connection state designating signal Qa[m] is high, and is off when the connection state designating signal Qa[m] is low. When the switch Wa[m] is on, the drive signal Com-A supplied to the wiring LA is supplied as a supply drive signal Vin[m] to the upper electrode Zu[m] of the ejection portion D[m].

[0094] The switch Wb[m] switches the on-off of the wiring LB and the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designating signal Qb[m]. In the present embodiment, the switch Wb[m] is on when the connection state designating signal Qb[m] is high, and is off when the connection state designating signal Qb[m] is low. When the switch Wb[m] is on, the drive signal Com-B supplied to the wiring LB is supplied as a supply drive signal Vin[m] to the upper electrode Zu[m] of the ejection portion D[m].

[0095] ​The switch Ws[m] switches the conduction and non-conduction of the wiring LS and the upper electrode Zu[m] of the piezoelectric element PZ[m] according to the connection state designation signal Qs[m]. In the present embodiment, the switch Ws[m] is conducted when the connection state designation signal Qs[m] is at a high level, and is shut off when the connection state designation signal Qs[m] is at a low level. When the switch Ws[m] is conducted, the potential of the upper electrode Zu[m] provided to the ejection section D[m] is supplied as a detection potential signal VX[m] to the detection circuit 33 via the wiring LS.

[0096] In the present embodiment, the detection circuit 33 generates a detection signal SK[m] having a waveform corresponding to the waveform of the detection potential signal VX[m] according to the detection potential signal VX[m] supplied from the wiring LS. Specifically, the detection circuit 33 generates a signal in which the detection potential signal VX[m] is amplified and a noise component is removed from the detection potential signal VX[m], and outputs the generated signal as the detection signal SK[m].

[0097] When the inkjet printer 1 performs a printing process or a determination target drive process, one or a plurality of unit periods TP are set as a period during which the inkjet printer 1 operates. In each unit period TP, the inkjet printer 1 can drive each ejection section D[m] for the printing process or the determination target drive process.

[0098] Figure 6 is a timing chart showing various signals such as the drive signal Com supplied to the head unit 3 in the unit period TP. In addition, Figure 7 is a timing chart showing the drive signal Com-B in the unit period TP.

[0099] As shown in Figure 6 , the control unit 2 outputs a latch signal LAT having a pulse PLL. Thereby, the control unit 2 defines the unit period TP as a period from the rising edge of the pulse PLL to the rising edge of the next pulse PLL.

[0100] In addition, the control unit 2 outputs a changeover signal CH having a pulse PLC in the unit period TP. Also, the control unit 2 divides the unit period TP into a drive period TQ1 from the rising edge of the pulse PLL to the rising edge of the pulse PLC and a drive period TQ2 from the rising edge of the pulse PLC to the rising edge of the pulse PLL.

[0101] In addition, the control unit 2 outputs a period specification signal Tsig with pulses PLT1 and PLT2 during the unit period TP. Furthermore, the control unit 2 divides the unit period TP into a control period TSS1 from the rising edge of pulse PLL to the rising edge of pulse PLT1, a control period TSS2 from the rising edge of pulse PLT1 to the rising edge of pulse PLT2, and a control period TSS3 from the rising edge of pulse PLT2 to the rising edge of pulse PLL.

[0102] like Figure 6 As shown, the printing signal SI includes M individually specified signals Sd[1] to Sd[M], each corresponding to one of the M ejector sections D[1] to D[M]. When the inkjet printer 1 performs printing processing or object determination driving processing, the individually specified signal Sd[m] specifies the driving mode of the ejector section D[m] in each unit period TP. Before each unit period TP, the control unit 2 synchronizes the printing signal SI, which includes the M individually specified signals Sd[1] to Sd[M], with the clock signal CL and supplies it to the connection state specifying circuit 310. Then, the connection state specifying circuit 310 generates connection state specifying signals Qa[m], Qb[m], and Qs[m] based on the individually specified signals Sd[m] in that unit period TP.

[0103] Furthermore, in this embodiment, it is assumed that when the inkjet printer 1 performs printing processing, the ejector section D[m] can form any one of the following points Dt: a large dot composed of ink amount ξ1, a midpoint composed of ink amount ξ2 less than ink amount ξ1, and a small dot composed of ink amount ξ3 less than ink amount ξ2. Additionally, in this embodiment, it is assumed that when the inkjet printer 1 performs determination object driving processing, the ejector section D[m] designated as the determination object ejector section DH ejects ink amount ξ0 more than ink amount ξ1.

[0104] Figure 8 This is an explanatory diagram used to illustrate a single specified signal Sd[m].

[0105] like Figure 8As shown, in this embodiment, the individually designated signal Sd[m] can take any one of the following five values ​​within the unit period TP during which the printing process or the object determination driving process is performed: "1" for designating the ejector D[m] as the large dot forming ejector DP-1, "2" for designating the ejector D[m] as the midpoint forming ejector DP-2, "3" for designating the ejector D[m] as the small dot forming ejector DP-3, "4" for designating the ejector D[m] as the non-dot forming ejector DP-4, and "5" for designating the ejector D[m] as the object determination ejector DH. Here, the large dot forming ejector DP-1 is the ejector D that forms large dots within the unit period TP. The midpoint forming ejector DP-2 is the ejector D that forms midpoints within the unit period TP. The small dot forming ejector DP-3 is the ejector D that forms small dots within the unit period TP. In addition, the non-point-forming ejection section DP-4 is the ejection section D that does not form a point within a unit period TP.

[0106] return Figure 6 and Figure 7 Please provide an explanation.

[0107] like Figure 6 As shown, in this embodiment, the drive signal Com-A has a waveform PA1 set during drive period TQ1 and a waveform PA2 set during drive period TQ2.

[0108] Here, waveform PA1 is the waveform that returns from reference potential V0 to reference potential V0 after passing through a potential VLA1 that is lower than reference potential V0 and a potential VHA1 that is higher than reference potential V0. Waveform PA1 is defined as the amount of ink equivalent to ink quantity φ1 being ejected from ejection section D[m] when a supply drive signal Vin[m] with waveform PA1 is supplied to ejection section D[m].

[0109] Furthermore, waveform PA2 is the waveform that returns from reference potential V0 to reference potential V0 after passing through a potential VLA2 (lower than reference potential V0) and a potential VHA2 (higher than reference potential V0). Waveform PA2 is defined as the amount of ink equivalent to ink quantity φ2 being ejected from ejection section D[m] when a supply drive signal Vin[m] with waveform PA2 is supplied to ejection section D[m].

[0110] Furthermore, in this embodiment, it is assumed that ink quantity ξ1 is equivalent to the sum of ink quantity φ1 and ink quantity φ2, ink quantity ξ2 is equivalent to ink quantity φ1, and ink quantity ξ3 is equivalent to ink quantity φ2.

[0111] In addition, in this embodiment, as an example, it is assumed that the potential VHA1 is higher than the potential VHA2 and the potential VLA1 is lower than the potential VLA2.

[0112] In addition, in the present embodiment, it is assumed, as an example, that the volume of the chamber CV provided in the ejection section D[m] becomes smaller when the potential of the supply drive signal Vin[m] supplied to the ejection section D[m] is a high potential than when it is a low potential. Therefore, when the ejection section D[m] is driven by the supply drive signal Vin[m] having the waveform PA1 or the like, the ink in the ejection section D[m] is ejected from the nozzle opening N by changing the potential of the supply drive signal Vin[m] from a low potential to a high potential.

[0113] As shown in FIG. 6, in the present embodiment, the drive signal Com-B has the waveform PS provided within the unit period TP. Figure 6 Figure 7 As shown in FIG. 6, in the present embodiment, the drive signal Com-B has the waveform PS provided within the unit period TP.

[0114] Here, the waveform PS is a waveform that changes from the reference potential V0 to a potential V1 higher than the reference potential V0 and a potential V2 lower than the reference potential V0 in the control period TSS1, maintains the potential V3 higher than the reference potential V0 in the control period TSS2, and changes from the potential V3 to the reference potential V0 in the control period TSS3.

[0115] In addition, in the present embodiment, it is assumed that the potential V1 is substantially the same as the potential VCH, the potential V2 is substantially the same as the potential VCL, and the potential V3 is substantially the same as the potential VCH. That is, in the present embodiment, it is assumed, as an example, that the potential V1 and the potential V3 are substantially the same.

[0116] Here, "substantially the same" means a concept that includes a case where it can be considered to be the same taking into account an error in addition to a case where it is completely the same. For example, "substantially the same" can also be a case where it is the same in design. In the present specification, for example, in a case where there is an error of 5% or less between two elements, the two elements are considered to be the same, and the two elements are set to be substantially the same.

[0117] ​Further, the potential VCH refers to a highest potential that the drive signal generation circuit 4R can supply to the upper electrode Zu[m] as the drive signal Com-R, and the potential VCL refers to a lowest potential that the drive signal generation circuit 4R can supply to the upper electrode Zu[m] as the drive signal Com-R. For example, the potential VCH can also be substantially the same potential as the potential VHH, and the potential VCL can also be substantially the same potential as the potential VLL. Further, for example, the potential VCH can also be a potential obtained by subtracting a voltage lowered due to the transistor TrH and a voltage lowered due to a transistor that configures the switch Wa[m] or the switch Wb[m] or the like from the potential VHH. Specifically, the potential VCH can also be, for example, a potential obtained by subtracting a voltage caused by an on-resistance of the transistor TrH and a voltage applied between a gate and a source of a transistor that configures the switch Wa[m] or the switch Wb[m] or the like in order to maintain an on state of the transistor from the potential VHH. Further, for example, the potential VCL can also be a potential obtained by adding a voltage lowered due to the transistor TrL and a voltage lowered due to a transistor that configures the switch Wa[m] or the switch Wb[m] or the like to the potential VLL. Further, for example, the potential VCL can also be a potential obtained by adding a voltage caused by an on-resistance of the transistor TrL and a voltage applied between a gate and a source of a transistor that configures the switch Wa[m] or the switch Wb[m] or the like in order to maintain an on state of the transistor to the potential VLL. Here, the potential VCH is an example of the "first potential", and the potential VCL is an example of the "second potential".

[0118] Further, hereinafter, a portion of the waveform PS in which the potential changes from the potential V1 to the potential V2 is referred to as a partial waveform PS1, and a portion of the waveform PS in which the potential changes from the potential V2 to the potential V3 is referred to as a partial waveform PS2. Further, hereinafter, a potential difference between the potential V1 and the potential V2 is referred to as a potential difference VD1, and a potential difference between the potential V3 and the potential V2 is referred to as a potential difference VD2. Further, hereinafter, a potential difference between the potential VCH and the potential VCL is referred to as a potential difference VDH. In the waveform PS related to the present embodiment, the potential difference VD1 and the potential difference VD2 are set to be substantially the same potential difference as the potential difference VDH.

[0119] Further, hereinafter, a portion of the drive signal Com-B that coincides with the partial waveform PS1 is referred to as a partial signal Com-PS1, and a portion of the drive signal Com-B that coincides with the partial waveform PS2 is referred to as a partial signal Com-PS2. That is, in the present embodiment, the drive signal Com-B includes the partial signal Com-PS1 having the partial waveform PS1 and the partial signal Com-PS2 having the partial waveform PS2. Here, the partial signal Com-PS1 is an example of the "first partial signal", and the partial signal Com-PS2 is an example of the "second partial signal".

[0120] Furthermore, in the following text, the period during which the potential of the drive signal Com-B in control period TSS1 is maintained at potential V1 is referred to as period Tv1; the period during which a partial waveform PS1 is set in control period TSS1 and the potential of the drive signal Com-B changes from potential V1 to potential V2 is referred to as period Td1; the period during which the potential of the drive signal Com-B in control period TSS1 is maintained at potential V2 is referred to as period Tv2; and the period during which a partial waveform PS2 is set in control period TSS1 and the potential of the drive signal Com-B changes from potential V2 to potential V3 is referred to as period Td2. Additionally, in the following text, the period during which the potential of the drive signal Com-B in unit period TP is maintained at potential V3 is referred to as period Tv3.

[0121] In this embodiment, as described above, it is assumed that in the drive signal Com-A, potential VHA1 is higher than potential VHA2 and potential VLA1 is lower than potential VLA2. That is, in this embodiment, as an example, it is assumed that the potential of the drive signal Com-A varies within the range of potential VLA1 to potential VHA1. Here, potential VLA1 is an example of a "third potential", and potential VHA1 is an example of a "fourth potential".

[0122] Furthermore, in this embodiment, it is assumed that potential VCH is higher than potentials VHA1 and VHA2 of the driving signal Com-A, and potential VLL is lower than potentials VLA1 and VLA2 of the driving signal Com-A. That is, in this embodiment, potential VCH is not included in the range of potentials VLA1 to VHA1 of the driving signal Com-A, and potential VLL is also not included in the range of potentials VLA1 to VHA1 of the driving signal Com-A. In other words, in this embodiment, the highest potential of the driving signal Com-A is lower than the highest potential of the driving signal Com-B, i.e., potential VCH, and the lowest potential of the driving signal Com-A is higher than the lowest potential of the driving signal Com-B, i.e., potential VCL. That is, in this embodiment, the range of potential variation of the driving signal Com-A is included within the range of potential variation of the driving signal Com-B.

[0123] Next, refer to Figure 8 The operation of the ejector D[m], specified by a single signal Sd[m], is explained.

[0124] like Figure 8As shown, in a case where the individual designation signal Sd[m] indicates a value "1" that designates the ejection section D[m] as the large dot forming ejection section DP-1 for the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a high level for the drive period TQ1 and the drive period TQ2. In this case, the switch Wa[m] is turned on for the drive period TQ1 and the drive period TQ2. Therefore, the ejection section D[m] is driven by the supply drive signal Vin[m] having the waveform PA1 and the waveform PA2 for the unit period TP, and ejects ink in an amount ξ1 corresponding to a large dot.

[0125] In addition, in a case where the individual designation signal Sd[m] indicates a value "2" that designates the ejection section D[m] as the medium dot forming ejection section DP-2 for the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a high level for the drive period TQ1. In this case, the switch Wa[m] is turned on for the drive period TQ1. Therefore, the ejection section D[m] is driven by the supply drive signal Vin[m] having the waveform PA1 for the unit period TP, and ejects ink in an amount ξ2 corresponding to a medium dot.

[0126] In addition, in a case where the individual designation signal Sd[m] indicates a value "3" that designates the ejection section D[m] as the small dot forming ejection section DP-3 for the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a high level for the drive period TQ2. In this case, the switch Wa[m] is turned on for the drive period TQ2. Therefore, the ejection section D[m] is driven by the supply drive signal Vin[m] having the waveform PA2 for the unit period TP, and ejects ink in an amount ξ3 corresponding to a small dot.

[0127] In addition, in a case where the individual designation signal Sd[m] indicates a value "4" that designates the ejection section D[m] as the non-dot forming ejection section DP-4 for the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qa[m], the connection state designation signal Qb[m], and the connection state designation signal Qs[m] to a low level for the entire unit period TP. In this case, the switch Wa[m], the switch Wb[m], and the switch Ws[m] are all turned off for the entire unit period TP. Therefore, the ejection section D[m] is not driven by the supply drive signal Vin[m] for the unit period TP, and does not eject ink.

[0128] In addition, in a case where the signal Sd[m] alone indicates the value "5" that specifies the ejection section D[m] as the determination target ejection section DH for the unit period TP, the connection state specifying circuit 310 sets the connection state specifying signal Qb[m] to the high level during the control period TSS1 and the control period TSS3, and sets the connection state specifying signal Qs[m] to the high level during the control period TSS2. In this case, the switch Wb[m] is turned on during the control period TSS1 and the control period TSS3, and the switch Ws[m] is turned on during the control period TSS2. Therefore, the ejection section D[m] that is specified as the determination target ejection section DH is driven by the supply drive signal Vin[m] having the partial waveform PS1 and the partial waveform PS2 during the control period TSS1, as a result of which the vibration generated in the ejection section D[m] also remains during the control period TSS2. Also, during the control period TSS2, in a case where the vibration remains in the ejection section D[m], the potential of the upper electrode Zu[m] provided to the ejection section D[m] changes. Also, the detection circuit 33 detects the potential of the upper electrode Zu[m] that changes in correspondence with the vibration remaining in the ejection section D[m] as the detection potential signal VX[m] via the switch Ws[m] during the control period TSS2.

[0129] That is, the waveform of the detection potential signal VX[m] detected from the ejection section D[m] during the control period TSS2 indicates the waveform of the vibration remaining in the ejection section D[m] during the control period TSS2. Also, the waveform of the detection signal SK[m] generated in accordance with the detection potential signal VX[m] detected from the ejection section D[m] during the control period TSS2 indicates the waveform of the vibration remaining in the ejection section D[m] during the control period TSS2.

[0130] 4. Verification Example

[0131] The following describes the drive signal Com-Bw and the drive signal Com-Bz related to the verification example with reference to Figure 9 and Figure 16 The drive signal Com-Bw and the drive signal Com-Bz related to the verification example are described below.

[0132] Figure 9 is a timing chart for explaining the drive signal Com-Bw related to the verification example 1.

[0133] As shown in Figure 9 , the drive signal Com-Bw has the waveform PS-W provided within the unit period TP.

[0134] Here, the waveform PS-W is a waveform that changes from the reference potential Vo to a potential Vlw that is higher than the reference potential Vo and a potential V2 that is lower than the reference potential Vo to a potential V3w that is higher than the reference potential Vo in the control period TSS1, maintains the potential V3w in the control period TSS2, and changes from the potential V3w to the reference potential Vo in the control period TSS3.

[0135] Further, in the verification example 1, the potential Vlw is a potential that satisfies "Vo ≤ Vlw < VCH". Specifically, in the verification example 1, the potential Vlw is set to be a potential closer to the reference potential Vo than the potential VCH, in other words, the potential Vlw is set to be a potential that satisfies "(Vlw - Vo) < (VCH - Vlw)". In addition, in the verification example 1, the potential V3w is a potential that satisfies "Vlw ≤ V3w ≤ VCH".

[0136] Further, in the verification example 1, a portion of the waveform PS-W in which the potential changes from the potential Vlw to the potential V2 is referred to as a partial waveform PS1w, and a portion of the waveform PS-W in which the potential changes from the potential V2 to the potential V3w is referred to as a partial waveform PS2w. In addition, hereinafter, the potential difference between the potential Vlw and the potential V2 is referred to as a potential difference VD1w, and the potential difference between the potential V3w and the potential V2 is referred to as a potential difference VD2w. In addition, hereinafter, the potential difference between the reference potential Vo and the potential VCL is referred to as a potential difference VDL.

[0137] Further, in the verification example 1, a portion of the drive signal Com-Bw that coincides with the partial waveform PS1w is referred to as a partial signal Com-PS1w, and a portion of the drive signal Com-Bw that coincides with the partial waveform PS2w is referred to as a partial signal Com-PS2w. That is, in the verification example 1, the drive signal Com-Bw includes the partial signal Com-PS1w having the partial waveform PS1w and the partial signal Com-PS2w having the partial waveform PS2w.

[0138] Further, in the verification example 1, the potential of the drive signal Com-Bw is maintained at the potential Vlw within the period Tv1 in the control period TSS1, the partial waveform PS1w in which the potential of the drive signal Com-Bw changes from the potential Vlw to the potential V2 is provided within the period Td1 in the control period TSS1, the potential of the drive signal Com-Bw is maintained at the potential V2 within the period Tv2 in the control period TSS1, the partial waveform PS2w in which the potential of the drive signal Com-Bw changes from the potential V2 to the potential V3w is provided within the period Td2 in the control period TSS1, and the potential of the drive signal Com-Bw is maintained at the potential V3w within the period Tv3 in the unit period TP.

[0139] Figure 10is a timing chart for explaining the drive signal Com-Bz involved in Verification Example 2.

[0140] As shown in Figure 10 , the drive signal Com-Bz has the waveform PS-Z provided within the unit period TP.

[0141] Here, the waveform PS-Z is a waveform that changes from the reference potential Vo to a potential Vlz higher than the reference potential Vo and a potential V2 lower than the reference potential Vo in the control period TSS1, maintains the potential V3 in the control period TSS2, and changes from the potential V3 to the reference potential Vo in the control period TSS3. Further, in Verification Example 2, the potential Vlz is a potential satisfying "Vo ≤ Vlz ≤ VCH".

[0142] Further, in Verification Example 2, a portion in which the waveform PS-Z changes from the potential Vlz to the potential V2 is referred to as a partial waveform PSlz, and a portion in which the waveform PS-Z changes from the potential V2 to the potential V3 is referred to as a partial waveform PS2 as in the embodiments. Further, hereinafter, a potential difference between the potential Vlw and the potential V2 is referred to as a potential difference VDlz.

[0143] Further, in Verification Example 2, a portion in the drive signal Com-Bz coinciding with the partial waveform PSlz is referred to as a partial signal Com-PSlz. That is, in Verification Example 2, the drive signal Com-Bz includes the partial signal Com-PSlz having the partial waveform PSlz and a partial signal Com-PS2 having the partial waveform PS2.

[0144] Further, in Verification Example 2, the potential of the drive signal Com-Bz is maintained at the potential Vlz within the period Tv1 in the control period TSS1, the partial waveform PSlz in which the potential of the drive signal Com-Bz changes from the potential Vlz to the potential V2 is provided within the period Tdl in the control period TSS1, the potential of the drive signal Com-Bz is maintained at the potential V2 within the period Tv2 in the control period TSS1, the partial waveform PS2 in which the potential of the drive signal Com-Bz changes from the potential V2 to the potential V3 is provided within the period Td2 in the control period TSS1, and the potential of the drive signal Com-Bz is maintained at the potential V3 within the period Tv3 in the unit period TP.

[0145] Next, an ejection abnormality assumed in the verification example will be described.

[0146] Figure 11 is a diagram for explaining a first mode of the ejection abnormality assumed in the verification example. Further, Figure 12 is a diagram for explaining a second mode of the ejection abnormality assumed in the verification example.

[0147] Here, the first mode of ejection abnormality is an ejection abnormality that occurs because a foreign matter GP of paper powder or thickened ink and the like adheres to and accumulates on the inner wall NH of the nozzle opening N provided in the ejection section D[m] as shown in FIG. 6A. Figure 11 When the first mode of ejection abnormality occurs in the ejection section D[m], the droplets of ink ejected from the nozzle opening N provided in the ejection section D[m] fly on a different trajectory than when the ejection state is normal due to the influence of the foreign matter GP adhering to the inner wall NH of the nozzle opening N. Therefore, when the first mode of ejection abnormality occurs in the ejection section D[m], the droplets of ink ejected from the ejection section D[m] land at a position different from the desired position of the recording paper sheet PP in the printing process.

[0148] Further, when the first mode of ejection abnormality occurs in the ejection section D[m], the flow resistance of the inner wall NH of the nozzle opening N becomes larger than when the ejection state of ink in the ejection section D[m] is normal, the position of the liquid surface at which the droplets of ink ejected from the nozzle opening N separate from the ink in the chamber CV provided in the ejection section D[m] changes in the Z2 direction, and therefore, the period of the vibration occurring in the ejection section D[m] becomes shorter.

[0149] In addition, the second mode of ejection abnormality is an ejection abnormality that occurs because a foreign matter GT of paper powder or thickened ink and the like adheres to and accumulates on the inner wall NH of the nozzle opening N provided in the ejection section D[m] as shown in FIG. 6B. Here, the foreign matter GT is a foreign matter that, like the foreign matter GP, accumulates on the inner wall NH but is smaller than the foreign matter GP.

[0150] Figure 12 When the second mode of ejection abnormality occurs in the ejection section D[m], the droplets of ink ejected from the nozzle opening N provided in the ejection section D[m] fly on a different trajectory than when the ejection state is normal due to the influence of the foreign matter GT adhering to the inner wall NH of the nozzle opening N. Therefore, when the second mode of ejection abnormality occurs in the ejection section D[m], the droplets of ink ejected from the ejection section D[m] land at a position different from the desired position of the recording paper sheet PP in the printing process. Further, the size of the deviation of the landing position when the second mode of ejection abnormality occurs is smaller than the deviation of the landing position when the first mode of ejection abnormality occurs.

[0151]

[0152] ​​Further, when the second type of ejection abnormality occurs in the ejection section D[m], the flow resistance of the inner wall NH of the nozzle opening N becomes larger than when the ejection state of the ink in the ejection section D[m] is normal, the position of the liquid surface at which the ink droplets ejected from the nozzle opening N separate from the ink in the chamber CV provided in the ejection section D[m] changes in the Z2 direction, and thus the period of the vibration occurring in the ejection section D[m] becomes shorter. Further, as described above, the foreign matter GP is larger than the foreign matter GT. Therefore, the period of the vibration occurring in the ejection section D[m] when the first type of ejection abnormality occurs is shorter than the period of the vibration occurring in the ejection section D[m] when the second type of ejection abnormality occurs.

[0153] Next, the detection of the ejection abnormality in the verification example will be described.

[0154] Figure 13 is a graph showing the period TC of the detection potential signal VX[m] detected from the ejection section D[m] when the drive signal Com-Bw involved in the verification example 1 is supplied to the ejection section D[m] as a determination target and the ejection section D[m] is driven. Further, in the graph Figure 13 In the graph, the horizontal axis represents the potential difference VD2w of the drive signal Com-Bw, and the vertical axis represents the period TC of the detection potential signal VX[m] detected from the ejection section D[m] driven by the drive signal Com-Bw. Specifically, in the graph Figure 13 In the graph, the horizontal axis represents the potential difference VD2w of the drive signal Com-Bw, and the vertical axis represents the period TC of the detection potential signal VX[m] detected from the ejection section D[m] driven by the drive signal Com-Bw. Specifically, in the graph

[0155] In addition, in the graph Figure 13In the diagram, line LW0 represents the relationship between the potential difference VD2w of the drive signal Com-Bw supplied to the ejection section D[m] and the period TC of the detection potential signal VX[m] when the ink ejection state in the ejection section D[m] is normal. Similarly, line LW1 represents the relationship between the potential difference VD2w of the drive signal Com-Bw supplied to the ejection section D[m] and the period TC of the detection potential signal VX[m] when a first-type ejection anomaly occurs in the ejection section D[m]. Furthermore, the difference dTW1 is the difference between the period TC of the detection potential signal VX[m] detected by the ejection section D[m] driven by the drive signal Com-Bw when a first-type ejection anomaly occurs in the ejection section D[m], and the period TC of the detection potential signal VX[m] detected by the ejection section D[m] driven by the drive signal Com-Bw when the ink ejection state in the ejection section D[m] is normal.

[0156] like Figure 13 As shown, in Verification Example 1, when a first-mode ejection anomaly occurs in the ejection section D[m], causing a change in the potential difference VD2w, the amplitude of the period TC shown in the detection potential signal VX[m] is larger than the amplitude of the period TC shown in the detection potential signal VX[m] when the ink ejection state in the ejection section D[m] is normal. Furthermore, in Verification Example 1, when the potential difference VD2w is close to the potential difference VDH, the difference dTW1 becomes larger compared to when the potential difference VD2 is close to the potential difference VDL. Therefore, in order to accurately detect the first-mode ejection anomaly using the drive signal Com-Bw involved in Verification Example 1, it is sufficient to set the potential difference VD2w to a value close to the potential difference VDH.

[0157] Figure 14 This is a graph showing the period TC of the detection potential signal VX[m] detected from the ejector D[m] when the driving signal Com-Bw involved in Verification Example 1 is supplied to the ejector D[m], which is driven as the ejector DH being judged. Furthermore, in Figure 14 In, with Figure 13 Similarly, in the driving signal Com-Bw involved in Verification Example 1, the potential difference VD2w is varied within the range of potential difference VDL to potential difference VDH, and the period TC of the detection potential signal VX[m] detected from the ejector D[m] driven by the driving signal Com-Bw is plotted.

[0158] In addition, Figure 14In the diagram, the relationship line LW2 represents the relationship between the potential difference VD2w of the drive signal Com-Bw supplied to the ejection section D[m] and the period TC of the detection potential signal VX[m] when a second type of ejection anomaly occurs in the ejection section D[m]. Furthermore, the difference dTW2 is the difference between the period TC of the detection potential signal VX[m] detected by the ejection section D[m] driven by the drive signal Com-Bw when a second type of ejection anomaly occurs in the ejection section D[m], and the period TC of the detection potential signal VX[m] detected by the ejection section D[m] driven by the drive signal Com-Bw when the ink ejection state in the ejection section D[m] is normal.

[0159] like Figure 14 As shown, in Verification Example 1, when a second type of ejection anomaly occurs in the ejection section D[m], the change amplitude of the period TC shown in the detection potential signal VX[m] when the potential difference VD2w changes is approximately the same as the change amplitude of the period TC shown in the detection potential signal VX[m] when the ink ejection state in the ejection section D[m] is normal. Specifically, in Verification Example 1, the difference dTW2 when the potential difference VD2w is close to the potential difference VDH is approximately the same as the difference dTW2 when the potential difference VD2 is close to the potential difference VDL. Therefore, even if the potential difference VD2w is set to a value close to the potential difference VDH, it is difficult to use the drive signal Com-Bw involved in Verification Example 1 to detect the second type of ejection anomaly with high precision.

[0160] Figure 15 This is a graph showing the period TC of the detection potential signal VX[m] detected from the ejector D[m] when the driving signal Com-Bz involved in Verification Example 2 is supplied to the ejector D[m], which is driven as the ejector DH being judged. Furthermore, in Figure 15 In the driving signal Com-Bz involved in Verification Example 2, by varying the potential V1z within the range of the reference potential V0 to the potential VCH, the potential difference VD1z is varied within the range of the potential difference VDL to the potential difference VDH, and the period TC of the detection potential signal VX[m] detected from the ejector D[m] driven by this driving signal Com-Bz is plotted. Specifically, in Figure 15 In the chart shown, the horizontal axis represents the potential difference VD1z of the driving signal Com-Bz, and the vertical axis represents the period TC of the detection potential signal VX[m] detected from the ejector D[m] driven by the driving signal Com-Bz.

[0161] In addition, Figure 15In the diagram, line LZ0 represents the relationship between the potential difference VD1z of the drive signal Com-Bz supplied to the ejection section D[m] and the period TC of the detection potential signal VX[m] when the ink ejection state in the ejection section D[m] is normal. Similarly, line LZ1 represents the relationship between the potential difference VD1z of the drive signal Com-Bz supplied to the ejection section D[m] and the period TC of the detection potential signal VX[m] when a first-type ejection anomaly occurs in the ejection section D[m]. Furthermore, the difference dTZ1 is the difference between the period TC of the detection potential signal VX[m] detected by the ejection section D[m] driven by the drive signal Com-Bz when a first-type ejection anomaly occurs in the ejection section D[m], and the period TC of the detection potential signal VX[m] detected by the ejection section D[m] driven by the drive signal Com-Bz when the ink ejection state in the ejection section D[m] is normal.

[0162] like Figure 15 As shown, in Verification Example 2, when a first-mode ejection anomaly occurs in the ejection section D[m], the change amplitude of the period TC shown in the detection potential signal VX[m] when the potential difference VD1z changes is approximately the same as the change amplitude of the period TC shown in the detection potential signal VX[m] when the ink ejection state in the ejection section D[m] is normal. However, in Verification Example 2, when the potential difference VD1z is close to the potential difference VDH, the difference dTZ1 is larger compared to when the potential difference VD2 is close to the potential difference VDL. Therefore, in order to detect the first-mode ejection anomaly with high precision using the drive signal Com-Bz involved in Verification Example 2, it is preferable to set the potential difference VD1z to a value close to the potential difference VDH. Furthermore, in Verification Example 2, the difference dTZ1 is a large value regardless of the potential difference VD1z. Therefore, if the drive signal Com-Bz involved in Verification Example 2 is used, the first-mode ejection anomaly can be detected regardless of the potential difference VD1z.

[0163] Figure 16 This is a graph showing the period TC of the detection potential signal VX[m] detected from the ejector D[m] when the driving signal Com-Bz involved in Verification Example 2 is supplied to the ejector D[m], which is driven as the ejector DH being judged. Furthermore, in Figure 16 In, with Figure 15 Similarly, in the driving signal Com-Bz involved in Verification Example 2, the potential difference VD1z is varied within the range of potential difference VDL to potential difference VDH, and the period TC of the detection potential signal VX[m] detected from the ejector D[m] driven by the driving signal Com-Bz is plotted.

[0164] In addition, Figure 16In the diagram, line LZ2 represents the relationship between the potential difference VD1z of the drive signal Com-Bz supplied to the ejection section D[m] and the period TC of the detection potential signal VX[m] when a second type of ejection anomaly occurs in the ejection section D[m]. Furthermore, the difference dTZ2 is the difference between the period TC of the detection potential signal VX[m] detected by the ejection section D[m] driven by the drive signal Com-Bz when a second type of ejection anomaly occurs in the ejection section D[m], and the period TC of the detection potential signal VX[m] detected by the ejection section D[m] driven by the drive signal Com-Bz when the ink ejection state in the ejection section D[m] is normal.

[0165] like Figure 16 As shown, in Verification Example 2, when a second type of ejection anomaly occurs in the ejection section D[m], the change amplitude of the period TC shown in the detection potential signal VX[m] when the potential difference VD1z changes is greater than the change amplitude of the period TC shown in the detection potential signal VX[m] when the ink ejection state in the ejection section D[m] is normal. Specifically, in Verification Example 2, the difference dTZ1 when the potential difference VD1z is close to the potential difference VDH is greater than the difference dTZ1 when the potential difference VD1z is close to the potential difference VDL. Therefore, in order to use the drive signal Com-Bz involved in Verification Example 2 to detect the second type of ejection anomaly with high precision, it is only necessary to set the potential difference VD1z to a value close to the potential difference VDH.

[0166] Further, the driving signal Com-B according to the present embodiment is a signal in which the potential V1z is set to the potential VCH and the potential difference VD1z is set to the potential difference VDH in the driving signal Com-Bz according to the verification example 2. That is, the driving signal Com-B according to the present embodiment has the partial waveform PS1 in which the potential difference VDH is changed from the potential VCH to the potential V2. On the other hand, the driving signal Com-Bw according to the verification example 1 has the partial waveform PS1w in which the potential difference VD1w is changed from the potential V1w closer to the reference potential V0 than the potential VCH to the potential V2. That is, the partial waveform PS1 according to the present embodiment has the potential difference VDH larger than the potential difference VD1w of the partial waveform PS1w according to the verification example 1. Therefore, the partial waveform PS1 according to the present embodiment can more strongly introduce the meniscus MN in the Z2 direction than the partial waveform PS1w according to the verification example 1. Thus, the driving signal Com-B according to the present embodiment can generate a larger vibration in the discharge portion D[m] driven as the determination target discharge portion DH than the driving signal Com-Bw according to the verification example 1. Therefore, by using the driving signal Com-B according to the present embodiment, it is possible to accurately detect both the first type of discharge abnormality and the second type of discharge abnormality.

[0167] Further, in the determination target driving process according to the present embodiment, the control unit 2 drives the discharge portion D[m] as the determination target discharge portion DH by the driving signal Com-B so that the detection potential signal VX[m] is output from the discharge portion D[m] to the detection circuit 33. Then, in the determination target driving process, the detection circuit 33 generates the detection signal SK[m] based on the detection potential signal VX[m] detected from the discharge portion D[m].

[0168] Then, in the ejection state determination processing, the determination unit 8 determines whether the period TC indicated by the detection potential signal VX[m] is equal to or greater than a threshold value TC-thl which is a non-negative real number, based on the detection signal SK[m] output from the detection circuit 33. Also, when the period TC of the detection potential signal VX[m] is equal to or greater than the threshold value TC-thl, the determination unit 8 generates determination information JH[m] indicating that the ejection state of the ink in the ejection section D[m] is normal, and supplies the determination information JH[m] to the control unit 2. In addition, when the period TC of the detection potential signal VX[m] is less than the threshold value TC-thl, the determination unit 8 determines whether the period TC indicated by the detection potential signal VX[m] is equal to or greater than a threshold value TC-th2 which is a real number smaller than the threshold value TC-thl. Also, when the period TC of the detection potential signal VX[m] is equal to or greater than the threshold value TC-th2, the determination unit 8 generates determination information JH[m] indicating that the second type of ejection abnormality has occurred in the ejection section D[m], and supplies the determination information JH[m] to the control unit 2. On the other hand, when the period TC of the detection potential signal VX[m] is less than the threshold value TC-th2, the determination unit 8 generates determination information JH[m] indicating that the first type of ejection abnormality has occurred in the ejection section D[m], and supplies the determination information JH[m] to the control unit 2.

[0169] Thus, in the present embodiment, by driving the ejection section D[m] with the drive signal Com-B, it is possible to determine whether the ejection state of the ink in the ejection section D[m] is normal, and when an ejection abnormality has occurred in the ejection section D[m], it is possible to determine whether the ejection abnormality is the first type of ejection abnormality or the second type of ejection abnormality.

[0170] 5. Summary of Embodiments

[0171] As described above, the inkjet printer 1 according to the present embodiment is characterized by including the supply circuit 31 which is capable of selectively supplying the drive signal Com-A and the drive signal Com-B to the piezoelectric element PZ[m], the drive signal Com-A being a signal which drives the piezoelectric element PZ[m] to eject the ink from the nozzle opening N to form an image on the recording paper sheet PP, the drive signal Com-B being a signal which drives the piezoelectric element PZ[m] to determine whether the foreign matter GT is attached to the inner wall NH of the nozzle opening N, and the determination unit 8 which determines whether the foreign matter GT is attached to the inner wall NH, the drive signal Com-B including the partial signal Com-PSl which changes from the potential VCH to the potential VCL and the partial signal Com-PS2 which changes from the potential VCL to the potential VCH, the partial signal Com-PS2 being supplied after the partial signal Com-PSl is supplied to the piezoelectric element PZ[m], so that the determination unit 8 determines whether the foreign matter GT is attached to the inner wall NH based on the vibration generated in the piezoelectric element PZ[m].

[0172] According to the present embodiment, therefore, the potential of the partial signal Com-PS1 can be greatly changed, and the potential of the partial signal Com-PS2 can be greatly changed. Thus, according to the present embodiment, the piezoelectric element PZ[m] can be greatly driven by the drive signal Com-B. As a result, according to the present embodiment, the ejection abnormality caused by the foreign matter GT attached to the inner wall NH of the nozzle opening N can be detected with high precision.

[0173] According to the present embodiment, therefore, the potential of the partial signal Com-PS1 can be greatly changed, and the potential of the partial signal Com-PS2 can be greatly changed. Thus, according to the present embodiment, the piezoelectric element PZ[m] can be greatly driven by the drive signal Com-B. As a result, according to the present embodiment, the ejection abnormality caused by the foreign matter GT attached to the inner wall NH of the nozzle opening N can be detected with high precision.

[0174] According to the present embodiment, therefore, the potential of the partial signal Com-PS1 can be greatly changed, and the potential of the partial signal Com-PS2 can be greatly changed. Thus, according to the present embodiment, the piezoelectric element PZ[m] can be greatly driven by the drive signal Com-B. As a result, according to the present embodiment, the ejection abnormality caused by the foreign matter GT attached to the inner wall NH of the nozzle opening N can be detected with high precision.

[0175] According to the present embodiment, therefore, the potential of the partial signal Com-PS1 can be greatly changed, and the potential of the partial signal Com-PS2 can be greatly changed. Thus, according to the present embodiment, the piezoelectric element PZ[m] can be greatly driven by the drive signal Com-B. As a result, according to the present embodiment, the ejection abnormality caused by the foreign matter GT attached to the inner wall NH of the nozzle opening N can be detected with high precision.

[0176] According to the present embodiment, therefore, the potential of the partial signal Com-PS1 can be greatly changed, and the potential of the partial signal Com-PS2 can be greatly changed. Thus, according to the present embodiment, the piezoelectric element PZ[m] can be greatly driven by the drive signal Com-B. As a result, according to the present embodiment, the ejection abnormality caused by the foreign matter GT attached to the inner wall NH of the nozzle opening N can be detected with high precision.

[0177] According to the present embodiment, therefore, the potential of the partial signal Com-PS1 can be greatly changed, and the potential of the partial signal Com-PS2 can be greatly changed. Thus, according to the present embodiment, the piezoelectric element PZ[m] can be greatly driven by the drive signal Com-B. As a result, according to the present embodiment, the ejection abnormality caused by the foreign matter GT attached to the inner wall NH of the nozzle opening N can be detected with high precision.

[0178] B. Modified Example

[0179] The above-described modes can be modified in various ways. Specific modification modes are exemplified below. Two or more modes selected arbitrarily from the following examples can be appropriately combined within a range where they do not contradict each other. Furthermore, for elements having the same function and effect as the embodiments exemplified below, the reference numerals referred to in the above description are used, and detailed description thereof is appropriately omitted.

[0180] Modification Example 1

[0181] In the above-described embodiments, the case where the potential of the drive signal Com-B is maintained at the potential V3 during the period from the end of the period Td2 in which the partial waveform PS2 is provided to the start of the control period TSS2 is exemplified, but the present application is not limited to such a mode. For example, the drive signal Com-B can also be caused to fluctuate in potential during the period from the end of the period Td2 in which the partial waveform PS2 is provided to the start of the control period TSS2.

[0182] Figure 17 is a timing chart showing the drive signal Com-B related to Modification Example 1.

[0183] As shown in Figure 17 , the drive signal Com-B related to Modification Example 1 has the waveform PS-H1 provided to the unit period TP.

[0184] Here, the waveform PS-H1 is a waveform that changes from the reference potential V0 to the potential V1 higher than the reference potential V0, the potential V2 lower than the reference potential V0, and the potential V3 higher than the reference potential V0 in the control period TSS1, maintains the potential V4 higher than the reference potential V0 in the control period TSS2, and changes from the potential V4 to the reference potential V0 in the control period TSS3.

[0185] Furthermore, in the present modification example, it is assumed that the potential V1 is a potential substantially the same as the potential VCH, the potential V2 is a potential substantially the same as the potential VCL, and the potential V3 is a potential substantially the same as the potential VCH. In addition, in the present modification example, it is assumed that the potential V4 is a potential between the reference potential V0 and the potential VCH. However, the present application is not limited to such a mode. The potential V4 may, for example, be a potential between the potential VLA1 and the potential VHA1. Furthermore, in the present modification example, the potential V4 is an example of a "specific potential".

[0186] In addition, in the present modification example, a portion of the waveform PS-H1 in which the potential V3 changes to the potential V4 is referred to as a partial waveform PS3. In addition, in the present modification example, a portion of the drive signal Com-B that coincides with the partial waveform PS3 is referred to as a partial signal Com-PS3. That is, in the present modification example, the drive signal Com-B includes the partial signal Com-PS1 having the partial waveform PS1, the partial signal Com-PS2 having the partial waveform PS2, and the partial signal Com-PS3 having the partial waveform PS3. Here, the partial signal Com-PS3 is an example of a "third partial signal".

[0187] In addition, in the present modification example, in the period Tv1 in the control period TSS1, the potential of the drive signal Com-B is maintained at the potential V1, in the period Td1 in the control period TSS1, the partial waveform PS1 in which the potential of the drive signal Com-B changes from the potential V1 to the potential V2 is provided, in the period Tv2 in the control period TSS1, the potential of the drive signal Com-B is maintained at the potential V2, in the period Td2 in the control period TSS1, the partial waveform PS2 in which the potential of the drive signal Com-B changes from the potential V2 to the potential V3 is provided, in the period Tv3 in the control period TSS1, the potential of the drive signal Com-B is maintained at the potential V3, in the period Td3 in the control period TSS1, the partial waveform PS3 in which the potential of the drive signal Com-B changes from the potential V3 to the potential V4 is provided, and in the period Tv4 in the unit period TP, the potential of the drive signal Com-B is maintained at the potential V4.

[0188] In the present modification example, the total of the time length of the period Td2 and the time length of the period Tv3 is adjusted to be substantially the same as the time length of the α times the period TC of the vibration generated in the discharge portion D[m]. In other words, in the present modification example, the time length from the start of the partial waveform PS2 to the start of the partial waveform PS3 is adjusted to be the time length of the α times the period TC. Here, the value α is a natural number that satisfies "α ≥ 2". In the present modification example, the value α is set to "2". In addition, the time from the start of the partial waveform PS2 to the start of the partial waveform PS3 is an example of a "limitation time".

[0189] In the present modification example, the partial waveform PS3 starts after the restriction time of the time length of 2 times the period TC elapses after the start of the partial waveform PS2. Therefore, according to the present modification example, the phase difference between the vibration generated in the ejection section D[m] when the ejection state of the ink in the ejection section D[m] is normal and the vibration generated in the ejection section D[m] when the ejection abnormality occurs in the ejection section D[m] becomes larger than in the case where the restriction time shorter than 2 times the period TC is provided. In addition, according to the present modification example, the phase difference between the vibration generated in the ejection section D[m] when the ejection state of the ink in the ejection section D[m] is normal and the vibration generated in the ejection section D[m] when the ejection abnormality occurs in the ejection section D[m] becomes larger than in the case where the partial waveform PS3 is not provided. Therefore, according to the present modification example, it is possible to determine the ejection state of the ejection section D[m] not only from the period TC of the vibration generated in the ejection section D[m] driven as the determination target ejection section DH but also from the phase of the vibration generated in the ejection section D[m] driven as the determination target ejection section DH.

[0190] Further, in the present modification example, in the drive signal Com-B having the waveform PS-H1, the partial waveform PS3 starts after the restriction time of the time length of a times the period TC elapses after the start of the partial waveform PS2, but the present application is not limited to this manner. For example, it is also possible that, in the drive signal Com-B having the waveform PS, the control period TSS2 starts after the restriction time of the time length of a times the period TC elapses after the start of the partial waveform PS2.

[0191] As described above, the inkjet printer 1 according to the present modification example is characterized in that the drive signal Com-B includes the partial signal Com-PS3 which changes from the potential VCH to the potential V4, and the determination unit 8 determines whether or not the foreign matter GT is attached to the inner wall NH of the nozzle opening N on the basis of the vibration generated in the piezoelectric element PZ[m] when the partial signal Com-PS3 is supplied to the piezoelectric element PZ[m] after the partial signal Com-PS1 and the partial signal Com-PS2 are supplied to the piezoelectric element PZ[m].

[0192] Further, the inkjet printer 1 according to the present modified example can be characterized in that the drive signal Com-A is a signal that causes the piezoelectric element PZ[m] to eject ink from the nozzle opening N by varying the potential in the range from the potential VLA1 to the potential VHA1, the drive signal Com-B includes the partial signal Com-PS3 that varies from the potential VCH to the potential V4, the determination unit 8 determines whether or not the foreign matter GT is attached to the inner wall NH of the nozzle opening N based on the vibration generated in the piezoelectric element PZ[m] when the partial signal Com-PS1 and the partial signal Com-PS2 are supplied to the piezoelectric element PZ[m] and the partial signal Com-PS3 is supplied to the piezoelectric element PZ[m], and the potential VCH and the potential VCL are not included in the range from the potential VLA1 to the potential VHA1, and the potential V4 is included in the range from the potential VLA1 to the potential VHA1.

[0193] Further, the inkjet printer 1 according to the present modified example can be characterized in that the drive signal Com-A is a signal that causes the piezoelectric element PZ[m] to eject ink from the nozzle opening N by varying the potential in the range from the potential VLA1 to the potential VHA1, the drive signal Com-B includes the partial signal Com-PS3 that varies from the potential VCH to the potential V4, the determination unit 8 determines whether or not the foreign matter GT is attached to the inner wall NH of the nozzle opening N based on the vibration generated in the piezoelectric element PZ[m] when the partial signal Com-PS1 and the partial signal Com-PS2 are supplied to the piezoelectric element PZ[m] and the partial signal Com-PS3 is supplied to the piezoelectric element PZ[m], and the potential VCH and the potential VCL are not included in the range from the potential VLA1 to the potential VHA1, and the potential V4 is included in the range from the potential VLA1 to the potential VHA1.

[0194] According to the present modified example, therefore, the ejection abnormality caused by the foreign matter GT attached to the inner wall NH of the nozzle opening N can be detected with high accuracy based on the phase of the vibration generated in the piezoelectric element PZ[m].

[0195] Modified Example 2

[0196] In the above-described embodiment and modified example 1, the case where the potential V1 is substantially the same as the potential VCH, the potential V2 is substantially the same as the potential VCL, and the potential V3 is substantially the same as the potential VCH in the drive signal Com-B is exemplified, but the present application is not limited to such a mode. For example, in the drive signal Com-B, the potential V1 can be substantially the same as the potential VCL, the potential V2 can be substantially the same as the potential VCH, and the potential V3 can be substantially the same as the potential VCL.

[0197] Figure 18 is a timing chart showing the drive signal Com-B according to modified example 2.

[0198] As shown in Figure 18 , the drive signal Com-B according to modified example 2 has the waveform PS-H2 provided within the unit period TP.

[0199] Here, the waveform PS-H2 is a waveform in which, in the control period TSS1, the potential is changed from the reference potential Vo to a potential VI lower than the reference potential Vo and a potential V2 higher than the reference potential Vo, and is changed to a potential V3 lower than the reference potential Vo, in the control period TSS2, the potential V3 is maintained, and in the control period TSS3, the potential is changed from the potential V3 to the reference potential Vo. Further, in the present modification example, it is assumed that the potential VI is the potential VCL, the potential V2 is the potential VCH, and the potential V3 is the potential VCL.

[0200] Specifically, in the modification example 2, in the period Tv1 in the control period TSS1, the potential of the drive signal Com-B is maintained at the potential VCL, in the period Td1 in the control period TSS1, the partial waveform PS1H in which the potential of the drive signal Com-B is changed from the potential VCL to the potential VCH is provided, in the period Tv2 in the control period TSS1, the potential of the drive signal Com-B is maintained at the potential VCH, in the period Td2 in the control period TSS1, the partial waveform PS2H in which the potential of the drive signal Com-B is changed from the potential VCH to the potential VCL is provided, in the period Tv3 in the unit period TP, the potential of the drive signal Com-B is maintained at the potential VCL, and after the period Tv3 in the unit period TP ends, the potential of the drive signal Com-B is changed from the potential VCL to the reference potential Vo.

[0201] According to the present modification example, the potential can be greatly changed in the partial waveform PS1H possessed by the drive signal Com-B, and the potential can be greatly changed in the partial waveform PS2H possessed by the drive signal Com-B. Therefore, according to the present modification example, the piezoelectric element PZ[m] can be greatly driven by the drive signal Com-B. Thus, according to the present modification example, the ejection abnormality caused by the foreign matter GT attached to the inner wall NH of the nozzle opening N can be detected with high accuracy.

[0202] Modification example 3

[0203] In the above-described embodiment and the modification examples 1 and 2, the case where the determination unit 8 is provided separately from the head unit 3 is exemplified and described, but the present application is not limited to such a mode.

[0204] Figure 19 is a block diagram showing an example of the configuration of the inkjet printer 1A to which the present modification example is applied.

[0205] As shown in Figure 19 , the inkjet printer 1A is different from the inkjet printer 1 to which the embodiment is applied in that the head unit 3A is provided instead of the head unit 3. In addition, the head unit 3A is different from the head unit 3 to which the embodiment is applied in that the determination unit 8 is provided.

[0206] According to the present modification example, since the determination unit 8 is provided to the head unit 3A, compared to a case where the determination unit 8 is provided outside the head unit 3A, it is possible to suppress the possibility of noise mixing into the detection signal SK[m] supplied from the detection circuit 33 to the determination unit 8, and thus it is possible to improve the accuracy of determination in the determination unit 8.

[0207] Modification Example 4

[0208] In the above-described embodiment and Modification Examples 1 to 3, a case where the inkjet printer 1 is provided with four head units 3 is assumed, but the present application is not limited to such a manner. The inkjet printer 1 can be provided with one or more head units 3 and three or fewer head units 3, and in addition, the inkjet printer 1 can be provided with five or more head units 3.

[0209] Modification Example 5

[0210] In the above-described embodiment and Modification Examples 1 to 4, a case where the inkjet printer 1 is a serial printer is exemplified, but the present application is not limited to such a manner. The inkjet printer 1 can also be a so-called line printer in which a plurality of nozzle openings N are provided in the head unit 3 in a manner so as to extend wider than the width of the recording paper PP.

Claims

1. A liquid discharge apparatus characterized by comprising: Possessing: a supply section that is capable of selectively supplying a first drive signal and a second drive signal to a piezoelectric element, the first drive signal being a signal that drives the piezoelectric element to eject liquid from a nozzle opening to form an image on a medium, the second drive signal being a signal that drives the piezoelectric element to determine whether or not a foreign substance is attached to an inner wall of the nozzle opening; and a determination section that determines whether or not a foreign substance is attached to the inner wall, the second drive signal includes: a partial signal that changes from a reference potential to a first potential; a first partial signal that changes from the first potential to a second potential; a second partial signal that changes from the second potential to the first potential; and a third partial signal that changes from the first potential to a specific potential, the determination section determines whether or not a foreign substance is attached to the inner wall based on a vibration that occurs in the piezoelectric element when the third partial signal is supplied after the partial signal, the first partial signal, and the second partial signal are supplied to the piezoelectric element.

2. The liquid ejecting apparatus according to claim 1, wherein the first drive signal is a signal that drives the piezoelectric element to eject liquid from the nozzle opening by changing a potential within a range of a third potential to a fourth potential, the first potential and the second potential are not included in the range of the third potential to the fourth potential.

3. The liquid ejecting apparatus according to claim 1 or 2, wherein the first potential is one of a highest potential and a lowest potential that can be supplied to the piezoelectric element via the supply section among potentials that a generation section can generate, the generation section generating the first drive signal and the second drive signal, the second potential is the other of the highest potential and the lowest potential that can be supplied to the piezoelectric element via the supply section among the potentials that the generation section can generate.

4. The liquid ejecting apparatus according to claim 1, wherein the first drive signal is a signal that drives the piezoelectric element to eject liquid from the nozzle opening by changing a potential within a range of a third potential to a fourth potential, the first potential and the second potential are not included in the range of the third potential to the fourth potential, the specific potential is included in the range of the third potential to the fourth potential.

5. The liquid ejecting apparatus according to claim 1, wherein the supply section starts to supply the third partial signal to the piezoelectric element after a lapse of a limit time from a start of the supply of the second partial signal to the piezoelectric element, the limit time having a time length that is twice a period of a vibration that occurs in the piezoelectric element.

6. The liquid ejecting apparatus according to claim 1 or 2, wherein a displacement amount of a liquid surface at the nozzle opening when the piezoelectric element is driven by the supply of the second drive signal is larger than a displacement amount of the liquid surface at the nozzle opening when the piezoelectric element is driven by the supply of the first drive signal.

7. A head unit characterized by comprising: Possessing: a supply section that selectively supplies a first drive signal and a second drive signal to the piezoelectric element, the first drive signal being a signal that drives the piezoelectric element to eject liquid from a nozzle opening to form an image on a medium, the second drive signal being a signal that drives the piezoelectric element to determine whether a foreign matter is attached to an inner wall of the nozzle opening; and a determination section that determines whether a foreign matter is attached to the inner wall, the second drive signal includes: a partial signal that changes from a reference potential to a first potential; a first partial signal that changes from the first potential to a second potential; a second partial signal that changes from the second potential to the first potential; and a third partial signal that changes from the first potential to a specific potential, the determination section determines whether a foreign matter is attached to the inner wall based on a vibration generated in the piezoelectric element when the third partial signal is supplied after the partial signal, the first partial signal, and the second partial signal are supplied to the piezoelectric element.

8. The head unit according to claim 7, wherein the first drive signal is a signal that drives the piezoelectric element to eject liquid from the nozzle opening by changing a potential in a range of a third potential to a fourth potential, the first potential and the second potential are not included in the range of the third potential to the fourth potential.

9. The head unit according to claim 7 or 8, wherein the first potential is one of a highest potential and a lowest potential that can be supplied to the piezoelectric element via the supply section among potentials that a generation section can generate, the generation section generating the first drive signal and the second drive signal, the second potential is the other of the highest potential and the lowest potential that can be supplied to the piezoelectric element via the supply section among the potentials that the generation section can generate.

10. The head unit according to claim 7, wherein the first drive signal is a signal that drives the piezoelectric element to eject liquid from the nozzle opening by changing a potential in a range of a third potential to a fourth potential, the first potential and the second potential are not included in the range of the third potential to the fourth potential, the specific potential is included in the range of the third potential to the fourth potential.

11. The head unit according to claim 7, wherein the supply section starts to supply the third partial signal to the piezoelectric element after a lapse of a limit time from a start of the supply of the second partial signal to the piezoelectric element, the limit time having a length of time that is twice a period of a vibration generated in the piezoelectric element.

12. The head unit according to claim 7 or 8, wherein a displacement amount of a liquid surface at the nozzle opening when the piezoelectric element is driven by the supply of the second drive signal is larger than a displacement amount of the liquid surface at the nozzle opening when the piezoelectric element is driven by the supply of the first drive signal.

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