Liquid discharge device and liquid discharge head

Abstract

To suppress an increase in the length of a unit period TU, which is a cycle for driving a discharge part D, when determining the state of the discharge part D.SOLUTION: An ink-jet printer 1 comprises: a drive signal generation unit 4 that generates a drive signal COM; a discharge part D that includes a nozzle N, a piezoelectric element PZ driven by the drive signal COM, and a cavity CV that discharges ink from the nozzle N in response to drive of the piezoelectric element PZ; a first inspection signal generation circuit 340 to which a residual vibration signal generated according to vibrations remaining in the discharge part D after the piezoelectric element PZ has been inputted, and which generates a pseudo residual vibration signal corresponding to the residual vibration signal; a second inspection signal generation circuit 350 to which the residual vibration signal is inputted, and which generates a detected residual vibration signal obtained by removing frequency components other than predetermined frequency components from the residual vibration signal; and an inspection unit 6 to which either of the pseudo residual vibration signal and the detected residual vibration signal is selectively inputted, and which determines the state of the discharge part D on the basis of the inputted signal.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a liquid ejection head. [Background technology]

[0002] A liquid ejection device such as an inkjet printer drives an ejection unit included in a liquid ejection head during each of a plurality of unit periods defined by a latch signal, thereby ejecting a liquid such as ink filled in the ejection unit and forming an image on a medium. However, this type of liquid ejection device may experience ejection abnormalities, in which the ejection unit is unable to eject liquid normally. For this reason, techniques for inspecting the ejection status of the ejection unit have been proposed. For example, Patent Document 1 discloses a technique for inspecting the ejection status of the ejection unit based on a detection signal that indicates vibrations remaining in the ejection unit after the ejection unit is driven by a drive signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-044771 Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to conventional technology, when inspecting the ejection state of an ejection unit, it was necessary to set the unit period, which is the cycle for driving the ejection unit, to a sufficiently long time length in order to both drive the ejection unit using a drive signal and detect any vibrations remaining in the driven ejection unit. [Means for solving the problem]

[0005] In order to solve the above problems, the liquid ejection device of the present invention comprises a drive signal generation unit that generates a drive signal, an ejection unit including a nozzle, a piezoelectric element driven by the drive signal, and a pressure chamber that ejects liquid from the nozzle in response to the driving of the piezoelectric element, a first signal generation unit that receives as input a residual vibration signal generated by vibration remaining in the ejection unit after the piezoelectric element is driven and generates a pseudo-residual vibration signal in response to the residual vibration signal, a second signal generation unit that receives as input the residual vibration signal and generates a detected residual vibration signal by removing frequency components other than predetermined frequency components from the residual vibration signal, and a judgment unit that selectively receives as input one of the pseudo-residual vibration signal and the detected residual vibration signal and judges the state of the ejection unit based on the input signal.

[0006] In addition, the liquid ejection head of the present invention comprises an ejection section including a nozzle, a piezoelectric element driven by a drive signal, and a pressure chamber that ejects liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generation section that receives as input a residual vibration signal generated by vibration remaining in the ejection section after the piezoelectric element is driven, and generates a pseudo-residual vibration signal in response to the residual vibration signal; a second signal generation section that receives as input the residual vibration signal, and generates a detected residual vibration signal by removing frequency components other than predetermined frequency components from the residual vibration signal; and a switching section that switches between supplying the pseudo-residual vibration signal to a judgment section that judges the state of the ejection section, or supplying the detected residual vibration signal to the judgment section. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram illustrating an example of the configuration of an inkjet printer according to an embodiment of the invention. [Figure 2] FIG. 1 is a perspective view illustrating an example of a schematic internal structure of an inkjet printer. [Figure 3] FIG. 4 is a cross-sectional view illustrating an example of the structure of a discharge portion. [Figure 4] 5A and 5B are explanatory diagrams for explaining the ink ejection operation in the ejection unit. [Figure 5]FIG. 2 is a plan view showing an example of the arrangement of nozzles in a head unit. [Figure 6] FIG. 2 is a block diagram showing an example of the configuration of a head unit. [Figure 7] FIG. 2 is a block diagram showing an example of the configuration of a detection circuit. [Figure 8] FIG. 2 is a circuit diagram showing an example of the configuration of a first selection circuit. [Figure 9] FIG. 2 is a circuit diagram showing an example of the configuration of a first inspection signal generating circuit. [Figure 10] FIG. 4 is a circuit diagram showing an example of the configuration of a second inspection signal generating circuit. [Figure 11] FIG. 4 is an explanatory diagram for explaining the characteristics of a first filter circuit. [Figure 12] FIG. 10 is a diagram showing a simulation result of the first filter circuit. [Figure 13] 10 is an explanatory diagram for explaining the operation of the low-pass filter circuit when the first input signal is switched from the detection signal to the first reference potential. FIG. [Figure 14] 5A and 5B are explanatory diagrams for explaining the effects of a first switching circuit and a low-pass filter circuit. [Figure 15] 10 is a timing chart showing an example of the operation of the inkjet printer in a unit period. [Figure 16] 4 is an explanatory diagram illustrating an example of a first test signal generated by a first test signal generating circuit. FIG. [Figure 17] 4 is an explanatory diagram illustrating an example of a second test signal generated by a second test signal generating circuit. FIG. [Figure 18] FIG. 10 is a block diagram showing an example of the configuration of a detection circuit according to a first modified example. [Figure 19] FIG. 10 is a circuit diagram showing an example of the configuration of a third filter circuit according to a first modified example. DETAILED DESCRIPTION OF THE INVENTION

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

[0009] [1. Embodiment] In this embodiment, a liquid ejection device will be described using an inkjet printer that ejects ink onto recording paper to form an image. Note that in this embodiment, ink is an example of a "liquid." First, the configuration of an inkjet printer 1 according to this embodiment will be described with reference to FIG. 1.

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

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

[0012] The inkjet printer 1 has a control unit 2 that controls each part of the inkjet printer 1, a head unit 3 that is provided with ejection units D that eject ink, and a drive signal generation unit 4 that generates drive signals COM for driving the ejection units D. The inkjet printer 1 also has a storage unit 5 that stores various information such as print data IMG and the control program PG of the inkjet printer 1, and an inspection unit 6 that determines the state of the ejection units D. The inkjet printer 1 also has a transport unit 7 that changes the relative position of the recording paper P with respect to the head unit 3, and a maintenance unit 8 that performs maintenance processing to maintain the ejection units D provided in the head unit 3. The head unit 3 is an example of a "liquid ejection head," the drive signal generation unit 4 is an example of a "drive signal generation unit," and the inspection unit 6 is an example of a "determination unit."

[0013] In this embodiment, it is assumed that the head units 3 and the drive signal generating units 4 correspond to each other, and that the head units 3 and the inspection units 6 correspond to each other. For example, the inkjet printer 1 may have a plurality of head units 3, a plurality of drive signal generating units 4 that correspond one-to-one to the plurality of head units 3, and a plurality of inspection units 6 that correspond one-to-one to the plurality of head units 3. Alternatively, the inkjet printer 1 may have one head unit 3, one drive signal generating unit 4 that corresponds to one head unit 3, and one inspection unit 6 that corresponds to one head unit 3. In this embodiment, it is assumed that the inkjet printer 1 has four head units 3, four drive signal generating units 4 that correspond one-to-one to the four head units 3, and four inspection units 6 that correspond one-to-one to the four head units 3. However, for the sake of convenience, the following description will focus on one head unit 3 out of the four head units 3, one drive signal generating unit 4 out of the four drive signal generating units 4 that corresponds to one head unit 3, and one inspection unit 6 out of the four inspection units 6 that corresponds to one head unit 3.

[0014] The control unit 2 is configured to include one or more CPUs (Central Processing Units). Note that the control unit 2 may be configured to include a programmable logic device such as an FPGA (field-programmable gate array) instead of or in addition to a CPU. The control unit 2 also functions as a drive control unit 22 by executing a control program PG stored in the storage unit 5.

[0015] The drive control unit 22 generates signals such as a print signal SI and a waveform designation signal dCOM to control the operation of each unit of the inkjet printer 1. Here, the waveform designation signal dCOM is a digital signal that defines the waveform of the drive signal COM. The drive signal COM is an analog signal for driving the discharge units D. The print signal SI is a digital signal for specifying the type of operation of the discharge units D. Specifically, the print signal SI is a signal that specifies the type of operation of the discharge units D by specifying whether or not to supply the drive signal COM to the discharge units D.

[0016] When a printing process is performed, for example, the drive control unit 22 controls the head unit 3 and the transport unit 7 to perform a printing process that prints an image indicated by the print data IMG on the recording paper P. Specifically, when a printing process is performed, the drive control unit 22 generates signals for controlling the head unit 3, such as a print signal SI, based on the print data IMG. When a printing process is performed, the drive control unit 22 also generates signals for controlling the drive signal generation unit 4, such as a waveform designation signal dCOM. When a printing process is performed, the drive control unit 22 also generates signals for controlling the transport unit 7. In this way, during the printing process, the drive control unit 22 controls the transport unit 7 to change the relative position of the recording paper P with respect to the head unit 3, while adjusting the presence or absence of ink ejection from the ejection unit D[m], the amount of ink ejection, the timing of ink ejection, and so on. In this way, the drive control unit 22 controls each part of the inkjet printer 1 so that an image corresponding to the print data IMG is formed on the recording paper P.

[0017] The drive signal generation unit 4 includes, for example, a DAC (Digital Analog Converter), and generates the drive signal COM based on the waveform designation signal dCOM supplied from the drive control unit 22. For example, the drive signal generation unit 4 generates the drive signal COM including a waveform defined by the waveform designation signal dCOM. The drive signal generation unit 4 outputs the drive signal COM generated based on the waveform designation signal dCOM to the switching circuit 31 included in the head unit 3.

[0018] The storage unit 5 includes one or both of a volatile memory such as a random access memory (RAM) and a non-volatile memory such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), or a programmable read-only memory (PROM). The storage unit 5 may be included in the control unit 2.

[0019] The head unit 3 includes a switching circuit 31 , a recording head 32 , and a detection circuit 33 .

[0020] The recording head 32 has M discharge sections D. The value M is a natural number greater than or equal to 1. Below, the mth discharge section D of the M discharge sections D provided in the recording head 32 may be referred to as discharge section D[m]. Here, the variable m is a natural number that satisfies "1≦m≦M." Also, below, when a component or signal of the inkjet printer 1 corresponds to a discharge section D[m] among the M discharge sections D, the subscript [m] may be added to the symbol representing the component or signal.

[0021] The switching circuit 31 switches whether or not to supply the drive signal COM to the discharge section D[m] based on the print signal SI. Note that, hereinafter, as shown in FIG. 6 and other figures described later, the drive signal COM supplied to the discharge section D[m] may be referred to as an individual drive signal Vin[m]. The drive signal COM and the individual drive signal Vin are examples of "drive signals."

[0022] The switching circuit 31 also switches whether to electrically connect the discharge section D[m] to the detection circuit 33 based on the print signal SI. When the discharge section D[m] is electrically connected to the detection circuit 33, for example, a detection signal Vout[m] detected from the discharge section D[m] is supplied to the detection circuit 33 via the switching circuit 31. The detection signal Vout[m] is, for example, an analog signal indicating a change in the potential of the upper electrode Zu[m] provided on the piezoelectric element PZ[m] of the discharge section D[m]. For example, the detection signal Vout[m] is a residual vibration signal generated by vibrations remaining in the discharge section D[m] after the piezoelectric element PZ[m] is driven by the individual drive signal Vin[m]. In this case, the waveform of the detection signal Vout[m] indicates, for example, the waveform of the residual vibrations remaining in the discharge section D[m] after the piezoelectric element PZ[m] is driven. The residual vibration of the discharge section D[m] after the piezoelectric element PZ[m] is driven corresponds to the residual vibration of the vibration plate 321 after the piezoelectric element PZ[m] is driven. The piezoelectric element PZ, the upper electrode Zu[m], and the vibration plate 321 will be described later with reference to FIG.

[0023] The detection circuit 33 generates an inspection signal VD[m] corresponding to the detection signal Vout[m] as a signal for determining the state of the discharge section D[m]. Details will be described later with reference to FIG. 7 and subsequent figures. For example, the detection circuit 33 generates the inspection signal VD[m] so as to mimic the attenuated wave of the detection signal Vout[m] indicating the residual vibration of the discharge section D[m]. Alternatively, the detection circuit 33 generates the inspection signal VD[m] by removing frequency components other than predetermined frequency components from the residual vibration signal. The detection circuit 33 then outputs the inspection signal VD[m] corresponding to the detection signal Vout[m] to the inspection unit 6.

[0024] The inspection unit 6, for example, determines the state of the ejection section D[m] based on the inspection signal VD[m]. For example, the inspection unit 6 determines the viscosity state of the ink in the ejection section D[m]. In this case, it is possible to prevent the printing process from being performed in a state where an abnormality due to viscosity increase in the ink in the ejection section D[m] has occurred. Hereinafter, the process of determining the state of the ejection section D[m] is also referred to as the ejection state determination process. Also, below, the ejection section D whose state is to be determined is also referred to as the ejection section D to be determined.

[0025] When the ejection state determination process is executed, the drive control unit 22 generates signals such as print signals SI for controlling the head unit 3. Furthermore, when the ejection state determination process is executed, the drive control unit 22 generates signals such as waveform designation signals dCOM for controlling the drive signal generation unit 4. As a result, the drive control unit 22 drives the ejection unit D[m] as the ejection unit D to be determined.

[0026] Furthermore, when the ejection state determination process is executed, the drive control unit 22 generates a print signal SI, thereby controlling the head unit 3 so that a detection signal Vout[m] corresponding to the ejection section D[m] driven as the ejection section D to be determined is supplied to the detection circuit 33. As a result, the detection circuit 33 generates an inspection signal VD[m] corresponding to the detection signal Vout[m] detected from the ejection section D[m] driven as the ejection section D to be determined. Then, the inspection unit 6 determines the state of the ejection section D[m] driven as the ejection section D to be determined based on the inspection signal VD[m] supplied from the detection circuit 33. Furthermore, the inspection unit 6 outputs state information Cinf including information indicating the determination result of the state of the ejection section D[m] to the control unit 2.

[0027] The inspection unit 6 may be included in the control unit 2. For example, the control unit 2 may function as the inspection unit 6 by operating in accordance with the control program PG stored in the storage unit 5.

[0028] As described above, in this embodiment, the inkjet printer 1 executes maintenance processes. For example, the maintenance processes include a flushing process that discharges ink from the ejection section D, a wiping process that uses a wiper to wipe off foreign matter such as ink adhering to the vicinity of the nozzles N of the ejection section D, and a pumping process that uses a tube pump or the like to suck ink from inside the ejection section D. The nozzles N will be described later with reference to FIG. 3.

[0029] For example, ink whose viscosity has increased is discharged from the discharge section D by a flushing process. This makes it possible to make the viscosity of the ink in the nozzle N equal to or lower than a predetermined viscosity at the start of the printing process. In this case, because the thickened ink is discharged from the discharge section D, it is possible to prevent a decrease in the quality of the image printed by the printing process.

[0030] The maintenance unit 8 has a discharged ink receiving section 80 for receiving the discharged ink when the ink is discharged from the discharge section D during the flushing process, a wiper for wiping off foreign matter such as ink adhering to the vicinity of the nozzles N of the discharge section D, and a tube pump for sucking ink, air bubbles, etc. from the discharge section D. The discharged ink receiving section 80 will be described later in FIG. 2. The wiper and tube pump are not shown in the drawings. Next, the general internal structure of the inkjet printer 1 will be described with reference to FIG. 2.

[0031] FIG. 2 is a perspective view showing an example of the general internal structure of the inkjet printer 1. As shown in FIG.

[0032] 2, this embodiment assumes that the inkjet printer 1 is a serial printer. Specifically, when performing a printing process, the inkjet printer 1 transports the recording paper P in the sub-scanning direction, while moving the head unit 3 back and forth in the main scanning direction that intersects the sub-scanning direction, and ejects ink from the ejection units D[m] to form dots on the recording paper P according to the print data IMG.

[0033] For ease of explanation, a three-axis Cartesian coordinate system having mutually orthogonal X, Y, and Z axes will be introduced as appropriate below. For example, in this embodiment, the Y1 direction along the Y axis is the sub-scanning direction, and the X1 and X2 directions along the X axis are the main scanning directions. Note that the X2 direction is the opposite direction to the X1 direction. Also, in this embodiment, as illustrated in FIG. 2, the Z1 direction along the Z axis is the ink ejection direction from the ejection section D[m]. Also, hereinafter, the X1 and X2 directions will be collectively referred to as the X-axis direction, the Y1 direction and the Y2 direction opposite to the Y1 direction will be collectively referred to as the Y-axis direction, and the Z1 direction and the Z2 direction opposite to the Z1 direction will be collectively referred to as the Z-axis direction. Note that, in this embodiment, as described above, it is assumed that the X, Y, and Z axes are orthogonal to each other, but the present invention is not limited to this configuration. For example, the X, Y, and Z axes may intersect with each other.

[0034] The inkjet printer 1 according to this embodiment has a housing 100 and a carriage 110 that is capable of reciprocating within the housing 100 in the X-axis direction and that has four head units 3 mounted thereon.

[0035] In this embodiment, it is assumed that the carriage 110 stores four ink cartridges 120 that correspond one-to-one to the four colors of ink: cyan, magenta, yellow, and black. As described above, it is also assumed in this embodiment that the inkjet printer 1 has four head units 3 that correspond one-to-one to the four ink cartridges 120. Each ejection section D[m] receives a supply of ink from the ink cartridge 120 that corresponds to the head unit 3 in which the ejection section D[m] is provided. This allows each ejection section D[m] to fill itself with the supplied ink and eject the filled ink from the nozzles N. Note that the ink cartridges 120 may also be provided outside the carriage 110.

[0036] As described with reference to FIG. 1 , the inkjet printer 1 according to this embodiment also includes a transport unit 7. The transport unit 7 includes a carriage transport mechanism 71 for reciprocating the carriage 110 in the X-axis direction and a carriage guide shaft 76 for supporting the carriage 110 so that it can reciprocate in the X-axis direction. The transport unit 7 also includes a medium transport mechanism 73 for transporting the recording paper P and a platen 75 disposed in the Z1 direction relative to the carriage 110. For example, during a printing process, the carriage transport mechanism 71 reciprocates the head unit 3 together with the carriage 110 along the carriage guide shaft 76 in the X-axis direction, and the medium transport mechanism 73 transports the recording paper P on the platen 75 in the Y1 direction. Therefore, during a printing process, the transport unit 7 causes the carriage transport mechanism 71 and the medium transport mechanism 73 to perform the above-described operations, thereby changing the relative position of the recording paper P with respect to the head unit 3 and enabling ink to land on the entire recording paper P.

[0037] Next, the general structure of the recording head 32 will be described with reference to FIG.

[0038] Fig. 3 is a cross-sectional view for explaining an example of the structure of the discharge portion D. Note that Fig. 3 schematically shows a cross section of a portion of the recording head 32 when the recording head 32 is cut so as to include the discharge portion D[m].

[0039] The ejection unit D[m] has a cavity CV filled with ink, a nozzle N communicating with the cavity CV, a piezoelectric element PZ[m] that generates pressure fluctuations in the ink in the cavity CV when an individual drive signal Vin[m] is supplied, and a vibration plate 321. The ejection unit D[m] ejects the ink in the cavity CV from the nozzle N when the piezoelectric element PZ[m] is driven by the individual drive signal Vin[m].

[0040] The cavity CV corresponds to a pressure chamber that communicates with the nozzle N. For example, the cavity CV is a space defined by a cavity plate 324, a nozzle plate 323 in which the nozzle N is formed, and a vibration plate 321. The cavity CV communicates with a reservoir 325 via an ink supply port 326. The reservoir 325 communicates with the ink cartridge 120 corresponding to the ejection section D[m] via an ink intake port 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric body Zb[m] provided between the upper electrode Zu[m] and the lower electrode Zd[m]. The piezoelectric body Zb[m] is formed of, for example, a ferroelectric piezoelectric material.

[0041] The upper electrode Zu[m] is electrically connected to the wiring Li to which the individual drive signal Vin[m] is supplied. The lower electrode Zd[m] is electrically connected to the wiring Ld to which the base potential signal VBS is supplied. When the individual drive signal Vin[m] is supplied to the upper electrode Zu[m], a voltage is applied between the upper electrode Zu[m] and the lower electrode Zd[m]. The piezoelectric element PZ[m] is displaced in the Z1 direction or the Z2 direction depending on the voltage applied between the upper electrode Zu[m] and the lower electrode Zd[m].

[0042] In this way, the piezoelectric element PZ[m] vibrates in response to the voltage applied between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is joined to the diaphragm 321. Therefore, when the piezoelectric element PZ[m] is driven to vibrate by the individual drive signal Vin[m], the diaphragm 321 also vibrates. The vibration of the diaphragm 321 changes the volume of the cavity CV and the pressure within the cavity CV, causing the ink filled in the cavity CV to be ejected from the nozzle N.

[0043] In this embodiment, as an example, it is assumed that the potential of the individual drive signal Vin[m] supplied to the discharge section D[m] changes from low to high, causing the piezoelectric element PZ to be displaced in the Z1 direction. That is, in this embodiment, it is assumed that when the potential of the individual drive signal Vin[m] supplied to the discharge section D[m] is high, the volume of the cavity CV provided in the discharge section D[m] becomes smaller than when the potential is low.

[0044] Next, the ink ejection operation in the ejection section D will be described with reference to FIG.

[0045] FIG. 4 is an explanatory diagram for explaining the ink ejection operation in the ejection section D.

[0046] For example, in the Phase-1 state, the drive control unit 22 changes the potential of the drive signal COM supplied to the piezoelectric element PZ of the ejection unit D, thereby generating distortion that displaces the piezoelectric element PZ in the Z2 direction. This causes the diaphragm 321 of the ejection unit D to bend in the Z2 direction. As a result, as shown in the Phase-2 state of FIG. 4, the volume of the cavity CV of the ejection unit D increases compared to the Phase-1 state. Next, for example, in the Phase-2 state, the drive control unit 22 changes the potential of the drive signal COM, thereby generating distortion that displaces the piezoelectric element PZ in the Z1 direction. This causes the diaphragm 321 of the ejection unit D to bend in the Z1 direction. As a result, as shown in the Phase-3 state of FIG. 4, the volume of the cavity CV suddenly contracts, and some of the ink filling the cavity CV is ejected as ink droplets from the nozzle N communicating with the cavity CV.

[0047] In this way, the piezoelectric element PZ and the vibration plate 321 of the discharge section D are displaced in the Z-axis direction when the piezoelectric element PZ of the discharge section D is driven by the drive signal COM. Therefore, residual vibration occurs in the discharge section D including the vibration plate 321 after the piezoelectric element PZ is driven by the drive signal COM.

[0048] Next, an example of the arrangement of the nozzles N will be described with reference to FIG.

[0049] Fig. 5 is a plan view showing an example of the arrangement of nozzles N in a head unit 3. Fig. 5 shows an example of the arrangement of four head units 3 mounted on a carriage 110 and a total of 4M nozzles N provided in the four head units 3 when the inkjet printer 1 is viewed from above in the Z1 direction.

[0050] Each head unit 3 provided on the carriage 110 is provided with a nozzle row NL. Here, the nozzle row NL is a plurality of nozzles N arranged so as to extend in a row in a predetermined direction. In this embodiment, it is assumed as an example that each nozzle row NL is composed of M nozzles N arranged so as to extend in the Y-axis direction.

[0051] Next, an overview of the head unit 3 will be described with reference to FIG.

[0052] FIG. 6 is a block diagram showing an example of the configuration of the head unit 3.

[0053] 1, the head unit 3 has a switching circuit 31, a recording head 32, and a detection circuit 33. The head unit 3 also has a wiring La to which a drive signal COM is supplied from the drive signal generation unit 4, a wiring Ls1 to which a potential signal Vzu is supplied to a high-pass filter circuit 312 (described later), and a wiring Ls2 to which a detection signal Vout is supplied to the detection circuit 33. The head unit 3 also has a wiring Li[m] to which an individual drive signal Vin[m] is supplied to the discharge section D[m], and a wiring Ld to which a base potential signal VBS is supplied.

[0054] The switching circuit 31 includes M switches SWa[1] to SWa[M] that correspond one-to-one to the M discharge units D[1] to D[M], M switches SWs[1] to SWs[M] that correspond one-to-one to the M discharge units D[1] to D[M], and a connection state specifying circuit 310. The switching circuit 31 also includes a high-pass filter circuit 312 that outputs a detection signal Vout[m] obtained by removing a DC component from a potential signal Vzu[m] that indicates the potential of the upper electrode Zu[m] provided on the piezoelectric element PZ[m] to the detection circuit 33. The potential signal Vzu[m] that is the source of the detection signal Vout[m] may also be considered a "residual vibration signal."

[0055] The high-pass filter circuit 312 includes, for example, a capacitor C10 having one end electrically connected to the line Ls1 and the other end electrically connected to the line Ls2. The switching circuit 31 also includes a resistor R10 having one end electrically connected to the line La and the other end electrically connected to the line Ls1. The resistor R10 functions as a bias resistor that supplies the voltage of the drive signal COM to the line Ls1. Hereinafter, the node to which one end of the resistor R10 is connected may be referred to as node N1, and the node to which the other end of the resistor R10 is connected may be referred to as node N2. For example, the resistor R10 and the capacitor C10 are connected to the node N2. For example, the detection circuit 33 is connected to the node N2 via the capacitor C10. Hereinafter, the node to which the capacitor C10 and the detection circuit 33 are connected may be referred to as node N3.

[0056] The connection state designation circuit 310 designates the connection states of the M switches SWa and the M switches SWs. For example, the connection state designation circuit 310 generates connection state designation signals Qa[m] and Qs[m] based on at least some of the signals of the print signal SI, latch signal LAT, and period definition signal Tsig supplied from the drive control unit 22. The connection state designation signal Qa[m] designates the on / off state of the switch SWa[m], and the connection state designation signal Qs[m] designates the on / off state of the switch SWs[m]. Furthermore, the connection state designation circuit 310 generates a selection signal SEL and a detection period signal Acut based on at least some of the signals of the print signal SI, latch signal LAT, and period definition signal Tsig. The selection signal SEL and the detection period signal Acut are supplied to the detection circuit 33.

[0057] In this embodiment, it is assumed that each of the M switches SWa and M switches SWs is configured with a transfer gate including a P-channel transistor and an N-channel transistor connected in parallel, although each of the M switches SWa and M switches SWs may be configured with either a P-channel transistor or an N-channel transistor.

[0058] The switch SWa[m] switches between conduction and non-conduction between the wiring La and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] based on the connection state designation signal Qa[m]. That is, the switch SWa[m] switches between conduction and non-conduction between the wiring La and the wiring Li[m] connected to the upper electrode Zu[m] based on the connection state designation signal Qa[m]. In this embodiment, the switch SWa[m] is turned on when the connection state designation signal Qa[m] is high level and turned off when the connection state designation signal Qa[m] is low level. When the switch SWa[m] is on, the drive signal COM supplied to the wiring La is supplied to the upper electrode Zu[m] of the discharge section D[m] via the wiring Li[m] as an individual drive signal Vin[m]. That is, the individual drive signal Vin[m] is the drive signal COM supplied to the piezoelectric element PZ[m] of the discharge section D[m] via the switch SWa[m].

[0059] The switch SWs[m] switches between conduction and non-conduction between the wiring Ls1 and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge portion D[m] based on the connection state designation signal Qs[m]. That is, the switch SWs[m] switches between conduction and non-conduction between the wiring Ls1 and the wiring Li[m] connected to the upper electrode Zu[m] based on the connection state designation signal Qs[m]. In this embodiment, the switch SWs[m] is turned on when the connection state designation signal Qs[m] is high level and turned off when it is low level.

[0060] For example, the connection state designation signal Qs[m] becomes high when detecting residual vibration of the discharge section D[m]. This detects residual vibration of the discharge section D being evaluated. When the switch SWs[m] is turned on, a potential signal Vzu[m] indicating the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] of the discharge section D[m] being evaluated is supplied to the high-pass filter circuit 312 via the wiring Li[m] and the wiring Ls1. The high-pass filter circuit 312 then supplies a detection signal Vout[m], which is obtained by removing the DC component of the potential signal Vzu[m], to the detection circuit 33 via the wiring Ls2. The detection circuit 33 generates an inspection signal VD[m] corresponding to the detection signal Vout[m].

[0061] While a large-amplitude drive signal COM is required to drive the piezoelectric element PZ, the detection circuit 33, being an analog signal processing circuit, does not require a large dynamic range. Therefore, in this embodiment, the high power supply potential of the detection circuit 33 is lower than the maximum potential of the drive signal COM. For example, the maximum potential of the drive signal COM is approximately 42 V, the high power supply potential of the detection circuit 33 is approximately 3.3 V, and the low power supply potential of the detection circuit 33 is approximately 0 V. Because the high power supply potential of the detection circuit 33 is lower than the maximum potential of the drive signal COM, DC coupling between the piezoelectric element PZ and the detection circuit 33 is not suitable. In this embodiment, the high-pass filter circuit 312 removes the DC component of the potential signal Vzu, allowing the detection circuit 33 to operate normally.

[0062] Next, an overview of the detection circuit 33 will be described with reference to FIG.

[0063] FIG. 7 is a block diagram showing an example of the configuration of the detection circuit 33. As shown in FIG.

[0064] The detection circuit 33 includes a first selection circuit 330 , a first inspection signal generation circuit 340 , a second inspection signal generation circuit 350 , and a second selection circuit 360 .

[0065] The first selection circuit 330 selects one of the detection signal Vout and the first reference potential Vref1 shown in Fig. 8 as the first input signal Vs1 based on the selection signal SEL and the detection period signal Acut. That is, the first selection circuit 330 supplies one of the detection signal Vout and the first reference potential Vref1 to the first inspection signal generation circuit 340 as the first input signal Vs1 based on the selection signal SEL and the detection period signal Acut.

[0066] 8 as the second input signal Vs2, based on the selection signal SEL and the detection period signal Acut. That is, the first selection circuit 330 supplies one of the detection signal Vout and the second reference potential Vref2 to the second inspection signal generation circuit 350 as the second input signal Vs2, based on the selection signal SEL and the detection period signal Acut.

[0067] The first inspection signal generating circuit 340 generates a first inspection signal Vd1 that imitates, for example, an attenuated wave of the detection signal Vout. As a result, the first inspection signal Vd1 is generated as a pseudo residual vibration signal that imitates the residual vibration of the discharge section D. Note that in this embodiment, it is assumed that the first inspection signal Vd1 is generated based on the residual vibration of the discharge section D that is equal to or greater than a quarter cycle and less than one cycle. For example, the first inspection signal generating circuit 340 generates a pseudo residual vibration signal based on the detection signal Vout that is equal to or greater than a quarter cycle and less than one cycle, and outputs the generated pseudo residual vibration signal as the first inspection signal Vd1. Note that the cycle of the first inspection signal Vd1 output from the first inspection signal generating circuit 340 is equal to or greater than one cycle, as shown in FIG. 16, which will be described later.

[0068] The first inspection signal generation circuit 340 includes, for example, a first gain adjustment circuit 342, a low-pass filter circuit 343, a first filter circuit 344, and a first buffer circuit 346. The first gain adjustment circuit 342 adjusts the amplitude of the first input signal Vs1. The low-pass filter circuit 343 attenuates high-frequency components of the first input signal Vs1. The high-frequency components are, for example, frequency components higher than the frequency band of residual vibration. The first filter circuit 344 is a multiple-feedback band-pass filter. The first buffer circuit 346 converts impedance and outputs a low-impedance first inspection signal Vd1. The first inspection signal generation circuit 340 is an example of a "first signal generation unit," the first filter circuit 344 is an example of a "filter circuit," and the low-pass filter circuit 343 is an example of a "low-pass filter." Details of the first inspection signal generation circuit 340 will be described later with reference to FIG. 9.

[0069] The second inspection signal generating circuit 350 generates the second inspection signal Vd2 by, for example, removing frequency components other than a predetermined frequency component from the detection signal Vout. As a result, the second inspection signal Vd2 is generated as a detected residual vibration signal corresponding to the signal of the predetermined frequency component of the detection signal Vout indicating the residual vibration of the discharge section D. The predetermined frequency component is, for example, a frequency component corresponding to the frequency band of the residual vibration. Note that in this embodiment, it is assumed that the second inspection signal Vd2 is generated based on one or more cycles of residual vibration of the discharge section D. For example, the second inspection signal generating circuit 350 generates a detected residual vibration signal based on one or more cycles of the detection signal Vout and outputs the generated detected residual vibration signal as the second inspection signal Vd2. The second inspection signal generating circuit 350 is an example of a "second signal generating section."

[0070] The second test signal generation circuit 350 includes, for example, a second gain adjustment circuit 352 configured similarly to the first gain adjustment circuit 342, a second filter circuit 354, and a second buffer circuit 356 configured similarly to the first buffer circuit 346. The second filter circuit 354 is a band-pass filter that passes signals of a predetermined frequency component. Details of the second test signal generation circuit 350 will be described later with reference to FIG. 10.

[0071] The second selection circuit 360 selects one of the first inspection signal Vd1 and the second inspection signal Vd2 as the inspection signal VD based on the selection signal SEL. That is, the second selection circuit 360 supplies one of the first inspection signal Vd1 and the second inspection signal Vd2 to the inspection unit 6 as the inspection signal VD based on the selection signal SEL. The second selection circuit 360 may, for example, exclusively switch between supplying the first inspection signal Vd1 to the inspection unit 6 or supplying the second inspection signal Vd2 to the inspection unit 6 based on the selection signal SEL. In this embodiment, when the selection signal SEL is at a high level, the second selection circuit 360 supplies the first inspection signal Vd1 to the inspection unit 6 as the inspection signal VD, and when the selection signal SEL is at a low level, the second selection circuit 360 supplies the second inspection signal Vd2 to the inspection unit 6 as the inspection signal VD. The second selection circuit 360 is an example of a "switching unit."

[0072] As described above, in this embodiment, the inspection unit 6 can switch between determining the state of the discharge portion D based on the first inspection signal Vd1 and determining the state of the discharge portion D based on the second inspection signal Vd2, based on the selection signal SEL. Note that the case where the inspection unit 6 determines the state of the discharge portion D based on the first inspection signal Vd1 and the case where the inspection unit 6 determines the state of the discharge portion D based on the second inspection signal Vd2 may each be considered as a mode for determining the state of the discharge portion D. Hereinafter, the case where the inspection unit 6 determines the state of the discharge portion D based on the first inspection signal Vd1 may be referred to as a first mode, and the case where the inspection unit 6 determines the state of the discharge portion D based on the second inspection signal Vd2 may be referred to as a second mode. In this case, the operation of the inspection unit 6 may also be described as follows. For example, the inspection unit 6 determines the state of the discharge portion D in a mode selected from a plurality of modes including the first mode and the second mode based on the selection signal SEL.

[0073] In this embodiment, as described above, the first inspection signal Vd1 is generated based on the residual vibration of less than one cycle of the discharge section D, and the second inspection signal Vd2 is generated based on the residual vibration of one cycle or more of the discharge section D. Therefore, when the state of the discharge section D is determined based on the first inspection signal Vd1, the time allocated to detecting the residual vibration of the discharge section D can be shortened compared to when the state of the discharge section D is determined based on the second inspection signal Vd2. As a result, in this embodiment, it is possible to prevent an increase in the time required to determine the state of multiple discharge sections D.

[0074] Next, an overview of the first selection circuit 330 will be described with reference to FIG.

[0075] FIG. 8 is a circuit diagram showing an example of the configuration of the first selection circuit 330. As shown in FIG.

[0076] The first selection circuit 330 has a reference potential generation circuit 332, a first reference potential generation circuit 334, a second reference potential generation circuit 336, a first switching circuit 335, a second switching circuit 337, an inverter INV1, and NOR circuits NOR1 and NOR2. The first switching circuit 335 is an example of a "first switching unit," and the second switching circuit 337 is an example of a "second switching unit."

[0077] The reference potential generating circuit 332 has resistors R30 and R31 connected in series between a wiring line to which the potential VPH is supplied and a wiring line to which the potential VPL is supplied. The potential VPH is the high power supply potential of the detection circuit 33, and the potential VPL is the low power supply potential of the detection circuit 33. One end of the resistor R30 is connected to the wiring line to which the potential VPH is supplied, and the other end of the resistor R30 is connected to the wiring line Ls2 to which the detection signal Vout is supplied. One end of the resistor R31 is connected to the wiring line Ls2, and the other end of the resistor R31 is connected to the wiring line to which the potential VPL is supplied. That is, the detection signal Vout is supplied to a node N3 to which the resistors R30 and R31 are electrically connected. The resistance values ​​of the resistors R30 and R31 are set, for example, so that a reference potential Vref0, which is the potential of the node N3 when the potential of the node N2 shown in FIG. 6 is maintained at a constant potential, becomes the center potential between the potentials VPH and VPL. For example, by setting the resistance value of each of the resistor elements R30 and R31 to 150 kΩ, the reference potential Vref0 is set to the center potential between the potentials VPH and VPL. Note that the node N3 is also the node to which the capacitor C10 is connected, as described in FIG.

[0078] The first reference potential generating circuit 334 has resistors R32 and R33 connected in series between a wiring line supplied with the potential VPH and a wiring line supplied with the potential VPL. One end of the resistor R32 is connected to the wiring line supplied with the potential VPH, and the other end of the resistor R33 is connected to one end of the resistor R33, and the other end of the resistor R33 is connected to the wiring line supplied with the potential VPL. Hereinafter, the node connecting the resistors R32 and R33 may be referred to as node N4. The resistance values ​​of the resistors R32 and R33 are set, for example, so that the first reference potential Vref1, which is the potential of node N4, is the center potential between the potentials VPH and VPL. The output impedance of the first reference potential generating circuit 334 is preferably smaller than the output impedance of the reference potential generating circuit 332 to minimize the effect of noise generated at node N4 on the first inspection signal generating circuit 340. For example, by setting the resistance value of each of the resistor elements R32 and R33 to 1.5 kΩ, the first reference potential Vref1 is set to the center potential between the potential VPH and the potential VPL.

[0079] The second reference potential generating circuit 336 has resistors R34 and R35 connected in series between a wiring line supplied with the potential VPH and a wiring line supplied with the potential VPL. One end of the resistor R34 is connected to the wiring line supplied with the potential VPH, and the other end of the resistor R34 is connected to one end of the resistor R35, and the other end of the resistor R35 is connected to the wiring line supplied with the potential VPL. Hereinafter, the node connecting the resistors R34 and R35 may be referred to as node N5. The resistance values ​​of the resistors R34 and R35 are set, for example, so that the second reference potential Vref2, which is the potential of node N5, is the center potential between the potentials VPH and VPL. The output impedance of the second reference potential generating circuit 336 is preferably smaller than the output impedance of the reference potential generating circuit 332 to minimize the effect of noise generated at node N5 on the second inspection signal generating circuit 350. For example, by setting the resistance value of each of the resistor elements R34 and R35 to 1.5 kΩ, the second reference potential Vref2 is set to the center potential between the potential VPH and the potential VPL.

[0080] Each of the first switching circuit 335 and the second switching circuit 337 has, for example, a first input terminal Pin1, a second input terminal Pin2, an output terminal Pout, and a control terminal Psel. Each of the first switching circuit 335 and the second switching circuit 337 switches between connecting the first input terminal Pin1 and the output terminal Pout or connecting the second input terminal Pin2 and the output terminal Pout in accordance with a signal supplied to the control terminal Psel. For example, when the level of the control terminal Psel is high, each of the first switching circuit 335 and the second switching circuit 337 connects the first input terminal Pin1 and the output terminal Pout and disconnects the second input terminal Pin2 and the output terminal Pout. Furthermore, when the level of the control terminal Psel is low, each of the first switching circuit 335 and the second switching circuit 337 brings the second input terminal Pin2 and the output terminal Pout into conduction and brings the first input terminal Pin1 and the output terminal Pout into non-conduction.

[0081] For example, the first input terminal Pin1 of the first switching circuit 335 is connected to node N3, the second input terminal Pin2 of the first switching circuit 335 is connected to node N4, and the output terminal Pout of the first switching circuit 335 is connected to the first inspection signal generation circuit 340. That is, the detection signal Vout is input to the first input terminal Pin1 of the first switching circuit 335, and a first reference potential Vref1 is supplied to the second input terminal Pin2 of the first switching circuit 335. In addition, an input selection signal SEL1 is supplied to the control terminal Psel of the first switching circuit 335. For example, after the first inspection signal generation circuit 340 switches from a state in which it is connected to the second input terminal Pin2 via the output terminal Pout to a state in which it is connected to the first input terminal Pin1 via the output terminal Pout, it starts outputting the first inspection signal Vd1 indicating the pseudo residual vibration signal.

[0082] Also, for example, the first input terminal Pin1 of the second switching circuit 337 is connected to node N3, the second input terminal Pin2 of the second switching circuit 337 is connected to node N5, and the output terminal Pout of the second switching circuit 337 is connected to the second inspection signal generation circuit 350. That is, the detection signal Vout is input to the first input terminal Pin1 of the second switching circuit 337, and a second reference potential Vref2 is supplied to the second input terminal Pin2 of the second switching circuit 337. Also, an input selection signal SEL2 is supplied to the control terminal Psel of the second switching circuit 337.

[0083] The inverter INV1 outputs an inverted signal of the selection signal SEL supplied from the connection state specifying circuit 310 to the NOR circuit NOR1. The inverted signal of the selection signal SEL is a signal obtained by inverting the level of the selection signal SEL. Specifically, the inverted signal of the selection signal SEL is a low-level signal when the selection signal SEL is high, and is a high-level signal when the selection signal SEL is low.

[0084] The NOR circuit NOR1 outputs the NOR operation result of the detection period signal Acut supplied from the connection state designation circuit 310 and the inverted signal of the selection signal SEL to the control terminal Psel of the first switching circuit 335 as the input selection signal SEL1.

[0085] The NOR circuit NOR2 outputs the NOR operation result of the selection signal SEL supplied from the connection state designation circuit 310 and the detection period signal Acut to the control terminal Psel of the second switching circuit 337 as the input selection signal SEL2.

[0086] 8, when the selection signal SEL is at a high level and the detection period signal Acut is at a low level, the first selection circuit 330 supplies the detection signal Vout as the first input signal Vs1 to the first inspection signal generation circuit 340. When the selection signal SEL is at a high level and the detection period signal Acut is at a high level, the first selection circuit 330 supplies the first reference potential Vref1 as the first input signal Vs1 to the first inspection signal generation circuit 340. When the selection signal SEL is at a low level, the first selection circuit 330 supplies the first reference potential Vref1 as the first input signal Vs1 to the first inspection signal generation circuit 340, regardless of the level of the detection period signal Acut.

[0087] Furthermore, when the selection signal SEL is at a low level and the detection period signal Acut is at a low level, the first selection circuit 330 supplies the detection signal Vout as the second input signal Vs2 to the second inspection signal generation circuit 350. When the selection signal SEL is at a low level and the detection period signal Acut is at a high level, the first selection circuit 330 supplies the second reference potential Vref2 as the second input signal Vs2 to the second inspection signal generation circuit 350. When the selection signal SEL is at a high level, the first selection circuit 330 supplies the second reference potential Vref2 as the second input signal Vs2 to the second inspection signal generation circuit 350 regardless of the level of the detection period signal Acut.

[0088] As described above, in this embodiment, when the selection signal SEL is at a high level, the first inspection signal generation circuit 340 is selected as the circuit that generates the inspection signal VD, and when the selection signal SEL is at a low level, the second inspection signal generation circuit 350 is selected as the circuit that generates the inspection signal VD. Furthermore, when the detection period signal Acut is at a low level, the detection signal Vout is input to the first inspection signal generation circuit 340 or the second inspection signal generation circuit 350. Hereinafter, the period when the detection period signal Acut is at a low level will also be referred to as a detection period Tdet1 or Tdet2, as shown in FIGS. 14 and 17, etc.

[0089] The configuration of the first selection circuit 330 is not limited to the example shown in Fig. 8. For example, the second reference potential generation circuit 336 may be omitted. In this case, the second input terminal Pin2 of the second switching circuit 337 is connected to, for example, node N4.

[0090] Next, an overview of the first inspection signal generating circuit 340 will be described with reference to FIG.

[0091] FIG. 9 is a circuit diagram showing an example of the configuration of the first inspection signal generating circuit 340. As shown in FIG.

[0092] As described with reference to FIG. 7, the first test signal generating circuit 340 includes a first gain adjusting circuit 342, a low-pass filter circuit 343, a first filter circuit 344, and a first buffer circuit 346.

[0093] The first gain adjustment circuit 342 is, for example, a negative feedback amplifier including an operational amplifier OP40 and a variable resistor RV1. For example, a first input signal Vs1 is supplied from the first switching circuit 335 to a non-inverting input terminal of the operational amplifier OP40, and a signal obtained by dividing the output signal of the operational amplifier OP40 using the variable resistor RV1 is fed back to the inverting input terminal of the operational amplifier OP40. For example, one end of the variable resistor RV1 is connected to the output terminal of the operational amplifier OP40, the other end of the variable resistor RV1 is connected to a line through which a first reference potential Vref1 is supplied, and a movable contact of the variable resistor RV1 is connected to the inverting input terminal of the operational amplifier OP40. The first gain adjustment circuit 342 can output a signal obtained by adjusting the amplitude of the first input signal Vs1 to the low-pass filter circuit 343 by, for example, adjusting the position of the movable contact of the variable resistor RV1.

[0094] The low-pass filter circuit 343 includes, for example, a resistor R40, a capacitor C40, and an operational amplifier OP41. One end of the resistor R40 is connected to the output terminal of the operational amplifier OP40 of the first gain adjustment circuit 342, and the other end of the resistor R40 is connected to a node N40. One end of the capacitor C40 is connected to the node N40, and the other end of the capacitor C40 is connected to a line to which a first reference potential Vref1 is supplied. The non-inverting input terminal of the operational amplifier OP42 is connected to the node N40, and the inverting input terminal of the operational amplifier OP42 is connected to the output terminal of the operational amplifier OP42. A first filter input signal INbpf1, which is a signal from the output terminal of the operational amplifier OP42, is input to the first filter circuit 344. That is, the first filter circuit 344 receives the first filter input signal INbpf1, which is a signal obtained by attenuating high-frequency components from the amplitude-adjusted first input signal Vs1.

[0095] The first filter circuit 344 is, for example, a multiple feedback band-pass filter including resistor elements R41, R42, and R43, capacitors C41 and C42, and an operational amplifier OP42.

[0096] One end of the resistor R41 is connected to the output terminal of the operational amplifier OP41 of the low-pass filter circuit 343, and the other end of the resistor R41 is connected to a node N41. One end of the capacitor C41 is connected to the node N41, and the other end of the capacitor C41 is connected to the inverting input terminal of the operational amplifier OP42. One end of the resistor R42 is connected to the inverting input terminal of the operational amplifier OP42, and the other end of the resistor R42 is connected to the output terminal of the operational amplifier OP42. The non-inverting input terminal of the operational amplifier OP42 is connected to a wiring line that supplies a first reference potential Vref1. One end of the resistor R43 is connected to the node N41, and the other end of the resistor R43 is connected to a wiring line that supplies the first reference potential Vref1. One end of the capacitor C42 is connected to the node N41, and the other end of the capacitor C42 is connected to the output terminal of the operational amplifier OP42.

[0097] For example, the first filter input signal INbpf1 is input to the inverting input terminal of the operational amplifier OP42 via a resistor R41 and a capacitor C41. That is, the first input signal Vs1 is input to the inverting input terminal of the operational amplifier OP42 via a first gain adjustment circuit 342, a low-pass filter circuit 343, a resistor R41, and a capacitor C41. The output signal of the operational amplifier OP42 is fed back to the inverting input terminal of the operational amplifier OP42 via a first feedback path FB1. The output signal of the operational amplifier OP42 is also fed back to the inverting input terminal of the operational amplifier OP42 via a second feedback path FB2 that is separate from the first feedback path FB1. The first feedback path FB1 is, for example, a feedback path that feeds back the output signal of the operational amplifier OP42 to the inverting input terminal of the operational amplifier OP42 via a resistor R42. The second feedback path FB2 is, for example, a feedback path that feeds back the output signal of the operational amplifier OP42 to the inverting input terminal of the operational amplifier OP42 via the capacitors C42 and C41. In this way, the first filter circuit 344 has the first feedback path FB1 and the second feedback path FB2 as feedback paths that feed back the output signal of the operational amplifier OP42 to the inverting input terminal of the operational amplifier OP42.

[0098] The output signal of the operational amplifier OP42 is supplied to the first buffer circuit 346 as the first filter output signal Obpf1.

[0099] The first buffer circuit 346 is a buffer that converts impedance and outputs the first inspection signal Vd1 with low impedance. For example, the first buffer circuit 346 is configured as a voltage follower using an operational amplifier OP43. As a result, the first filter output signal Obpf1 supplied to the first buffer circuit 346 is output from the first buffer circuit 346 as the first inspection signal Vd1 with low impedance.

[0100] Next, the calculation formulas for the gain, center frequency, and Q value of the first filter circuit 344 will be explained, assuming that the gain is H and the center frequency is f0. The Q value is a parameter obtained by dividing the center frequency f0 by the passband width. The passband width is, for example, a bandwidth defined by the frequency at which the gain H is -3 dB.

[0101] The general transfer function of a bandpass filter is expressed by equation (1), where the potential of the input signal is Vi, the potential of the output signal is Vo, and "2πf0" is "ω0". In the following equations, "·" is used as appropriate to indicate multiplication.

[0102]

number

[0103] Furthermore, the transfer function of the first buffer circuit 346 is expressed by equation (2) where the potential of the first filter input signal INbpf1 is Vi and the potential of the first filter output signal Obpf1 is Vo. In the following equations, the resistance value of the resistive element and the capacitance value of the capacitor are indicated by using a symbol in which the last digit of the symbol of the element is added as a subscript. For example, "R 41 ", "R 42 " and "R 43 " indicates the resistance values ​​of the resistive elements R41, R42, and R43, respectively, and "C 41 " and "C 42 " indicate the capacitance values ​​of the capacitors C41 and C42, respectively.

[0104]

number

[0105] From equations (1) and (2), the amplification factor H, center frequency f0, and Q value of the first filter circuit 344 are expressed by equations (3), (4), and (5), respectively.

[0106]

number

[0107] Here, “C=C 41 =C 42 " and "R=R 41 =R 42 When the first buffer circuit 346 is designed under the condition of ", the amplification factor H, the center frequency f0, and the Q value are expressed by equations (6), (7), and (8), respectively, based on equations (3), (4), and (5).

[0108]

number

[0109] From equations (6) and (7), it can be seen that the amplification factor H is determined by the resistance values ​​of resistor elements R41 and R42 and the resistance value of resistor element R43, and the Q value is proportional to the positive square root of the absolute value of the amplification factor.

[0110] The configuration of the first test signal generation circuit 340 is not limited to the examples shown in Fig. 7 and Fig. 9. For example, the first gain adjustment circuit 342 may be provided between the first filter circuit 344 and the first buffer circuit 346. Alternatively, some or all of the first gain adjustment circuit 342, the low-pass filter circuit 343, and the first buffer circuit 346 may be omitted from the first test signal generation circuit 340 shown in Fig. 9.

[0111] Next, an overview of the second inspection signal generating circuit 350 will be described with reference to FIG.

[0112] FIG. 10 is a circuit diagram showing an example of the configuration of the second inspection signal generating circuit 350. As shown in FIG.

[0113] The second test signal generating circuit 350 includes a second gain adjusting circuit 352, a second filter circuit 354, and a second buffer circuit 356, as described with reference to FIG.

[0114] The second gain adjustment circuit 352 is a negative feedback amplifier configured similarly to the first gain adjustment circuit 342 shown in FIG. 9 . For example, the second gain adjustment circuit 352 includes an operational amplifier OP50 that receives a second input signal Vs2 supplied from the second switching circuit 337 at its non-inverting input terminal, and a variable resistor RV2 that divides the output signal of the operational amplifier OP50 and feeds the divided signal back to the inverting input terminal of the operational amplifier OP50. One end of the variable resistor RV2 is connected to the output terminal of the operational amplifier OP50, the other end of the variable resistor RV2 is connected to a line that supplies a second reference potential Vref2, and a movable contact of the variable resistor RV2 is connected to the inverting input terminal of the operational amplifier OP50. The second gain adjustment circuit 352 can output a second filter input signal INbpf2, the amplitude of which is adjusted from the second input signal Vs2, to the second filter circuit 354, by, for example, adjusting the position of the movable contact of the variable resistor RV2.

[0115] The second filter circuit 354 is, for example, a band-pass filter including resistor elements R51 and R52, capacitors C51 and C52, and an operational amplifier OP51, and passes signals of a predetermined frequency component.

[0116] One end of the resistor R51 is connected to the output terminal of the operational amplifier OP50 of the second gain adjustment circuit 352, and the other end of the resistor R51 is connected to one end of a capacitor C51, the other end of which is connected to the inverting input terminal of the operational amplifier OP51. One end of the capacitor C52 is connected to the inverting input terminal of the operational amplifier OP51, and the other end of the capacitor C52 is connected to the output terminal of the operational amplifier OP51. One end of the resistor R52 is connected to the inverting input terminal of the operational amplifier OP51, and the other end of the resistor R52 is connected to the output terminal of the operational amplifier OP51. In addition, the non-inverting input terminal of the operational amplifier OP51 is connected to a wiring to which a second reference potential Vref2 is supplied.

[0117] For example, the second filter input signal INbpf2 is input to the inverting input terminal of the operational amplifier OP51 via a resistor R51 and a capacitor C51. That is, the second input signal Vs2 is input to the inverting input terminal of the operational amplifier OP51 via the second gain adjustment circuit 352, the resistor R51, and the capacitor C51. The output signal of the operational amplifier OP41 is fed back to the inverting input terminal of the operational amplifier OP41 via a feedback path in which a resistor R52 and a capacitor C52 are connected in parallel.

[0118] The output signal of the operational amplifier OP51 is supplied to the second buffer circuit 356 as the second filter output signal Obpf2.

[0119] The second buffer circuit 356 is a buffer that converts impedance and outputs the second inspection signal Vd2 of low impedance. For example, the second buffer circuit 356 is configured as a voltage follower using an operational amplifier OP52, similar to the first buffer circuit 346 shown in FIG. 9. As a result, the second filter output signal Obpf2 supplied to the second buffer circuit 356 is output from the second buffer circuit 356 as the second inspection signal Vd2 of low impedance.

[0120] Next, regarding the calculation formulas for the low-pass cutoff frequency, high-pass cutoff frequency, and amplification factor of the second filter circuit 354, the low-pass cutoff frequency is set to f LPF The high-frequency cutoff frequency is f HPF and the amplification factor is G.

[0121] The cutoff frequency f of the second filter circuit 354 LPF is the cutoff frequency of the low-pass filter including the capacitor C52 and the resistor R52, and is expressed by equation (9). HPF is the cutoff frequency of the high-pass filter including the capacitor C51 and the resistor R51, and is expressed by equation (10).

[0122]

number

[0123] The amplification factor G of the second filter circuit 354 is expressed by equations (11), (12), and (13). Note that the angular frequency ω [rad] in equations (12) and (13) indicates the angular frequency corresponding to the center frequency of the second filter circuit 354 that functions as a band-pass filter.

[0124]

number

[0125] The configuration of the second test signal generation circuit 350 is not limited to the examples shown in Fig. 7 and Fig. 10. For example, the second gain adjustment circuit 352 may be provided between the second filter circuit 354 and the second buffer circuit 356. Alternatively, the second gain adjustment circuit 352 and the second buffer circuit 356 may be partially or entirely omitted from the second test signal generation circuit 350 shown in Fig. 10.

[0126] Next, the characteristics of the first filter circuit 344 will be described with reference to FIG.

[0127] FIG. 11 is an explanatory diagram illustrating the characteristics of the first filter circuit 344. The upper diagram of FIG. 11 shows the relationship between the gain and group delay of the first filter circuit 344 and frequency. The lower diagram of FIG. 11 shows the response of the first filter circuit 344 when a signal that changes from high level to low level is input to the first filter circuit 344 having the characteristics shown in the upper diagram of FIG. 11. Note that in FIG. 11, the characteristics of the second filter circuit 354 are shown by dashed lines for comparison with the first filter circuit 344.

[0128] As described in FIG. 9, the first filter circuit 344 is a multiple feedback bandpass filter. As shown in the upper diagram of FIG. 11, a multiple feedback bandpass filter has a characteristic in which the group delay changes significantly near the center frequency f0. The occurrence of a delay near the center frequency f0 means that the phase rotates near the center frequency f0. For example, the group delay characteristic can be expressed as "Tdg(ω)=-dφ / dω" where Tdg is the group delay, φ [rad] is the phase, and ω [rad / sec] is the angular velocity.

[0129] In the first filter circuit 344, where the group delay changes significantly near the center frequency f0, an overshoot occurs at the center frequency f0. That is, a damped oscillatory waveform occurs at the center frequency f0. As a result, the first filter circuit 344 outputs a signal having a damped oscillatory waveform even when the input signal is maintained at a low-level potential, as shown in the lower diagram of FIG.

[0130] In contrast, the second filter circuit 354 does not have a characteristic in which the group delay changes significantly near the center frequency f0, as shown by the dashed line in the upper diagram of Fig. 11. In the second filter circuit 354, when the input signal is maintained at a low level potential, the output signal converges to a predetermined potential, as shown by the dashed line in the lower diagram of Fig. 11.

[0131] In this embodiment, by making the damped oscillation waveform generated at the center frequency f0 closer to a sine wave, the first filter output signal Obpf1, which is the output signal of the first filter circuit 344, can be treated as a pseudo residual vibration signal that imitates the residual vibration of the discharge section D. Here, the time ts shown in FIG. 11 is the time it takes for the potential of the first filter input signal INbpf1 input to the first filter circuit 344 to go from the maximum value to the minimum value. For example, in order to generate a damped oscillation waveform that is close to a sine wave, the center frequency f0 is designed to be equal to or less than "1 / (2ts)".

[0132] Next, with reference to FIG. 12, the simulation results of the first filter circuit 344 will be described.

[0133] Fig. 12 is a diagram showing the simulation results of the first filter circuit 344. Fig. 12 also shows the simulation results of the response of the first filter circuit 344 when a signal that changes from high level to low level is input. In the simulation shown in Fig. 12, the time ts required for the potential of the signal input to the first filter circuit 344 to change from the maximum value to the minimum value is 1 μsec, and "1 / (2ts)" is 500 kHz.

[0134] Furthermore, simulation result Sim1 shows the simulation result of the first filter circuit 344 when the Q value is 3.26 and the center frequency f0 is 186 kHz. Simulation result Sim2 shows the simulation result of the first filter circuit 344 when the Q value is 2.85 and the center frequency f0 is 162 kHz. Simulation result Sim3 shows the simulation result of the first filter circuit 344 when the Q value is 2.56 and the center frequency f0 is 146 kHz. Simulation result Sim4 shows the simulation result of the first filter circuit 344 when the Q value is 2.34 and the center frequency f0 is 134 kHz. Simulation result Sim5 shows the simulation result of the first filter circuit 344 when the Q value is 2.17 and the center frequency f0 is 124 kHz.

[0135] 12, when the center frequency f0 is equal to or less than "1 / (2ts)", the output signal of the first filter circuit 344 becomes close to a sine wave. Although not shown in FIG. 12, it has been confirmed that when the center frequency f0 is "1 / ts", distortion occurs in the output signal of the first filter circuit 344, resulting in a simulation result in which the output signal of the first filter circuit 344 cannot be regarded as a sine wave.

[0136] Next, with reference to FIG. 13, a brief description will be given of the operation of the low-pass filter circuit 343 when the first input signal Vs1 switches from the detection signal Vout to the first reference potential Vref1.

[0137] FIG. 13 is an explanatory diagram for explaining the operation of the low-pass filter circuit 343 when the first input signal Vs1 switches from the detection signal Vout to the first reference potential Vref1.

[0138] For example, at the end of detection when the first input signal Vs1 switches from the detection signal Vout to the first reference potential Vref1, the potential Vn40 of the node N40 is maintained at the potential of the output signal of the operational amplifier OP40 at the end of detection by the capacitor C40. The potential Vn40 of the node N40 then converges to the first reference potential Vref1 using the time constant of the low-pass filter circuit 343. For example, if the potential Vn40 of the node N40 at the end of detection is higher than the first reference potential Vref1, the capacitor C40 is discharged to the first gain adjustment circuit 342 via the first path PH1. Furthermore, if the potential Vn40 of the node N40 at the end of detection is lower than the first reference potential Vref1, the capacitor C40 is charged via the second path PH2 from the first gain adjustment circuit 342.

[0139] The potential Vn40 of node N40 after the end of detection is expressed by equation (14) using the first reference potential Vref1, the elapsed time t from the end of detection, the time constant τ, and the potential difference ΔVn40 between the potential Vn40 at the end of detection and the first reference potential Vref1.

[0140] Vn40=ΔVn40·exp(-t / τ)+Vref1 …(14)

[0141] Note that "exp()" in equation (14) represents an exponential function. The potential difference ΔVn40 in equation (14) is expressed by equation (15), for example, using the potential Vn40 at the end of detection and the first reference potential Vref1.

[0142] ΔVn40=Vn40-Vref1 …(15)

[0143] Furthermore, the time constant τ in equation (14) is expressed by equation (16) when the output impedance of the circuit preceding the low-pass filter circuit 343 is Rp. In this embodiment, the circuit preceding the low-pass filter circuit 343 is the first gain adjustment circuit 342, and therefore the output impedance Rp in equation (16) represents the output impedance of the first gain adjustment circuit 342.

[0144] τ=C 40 ·(R 40 +Rp) …(16)

[0145] If the output impedance of the operational amplifier OP40 is much smaller than the impedance of the variable resistor RV, the output impedance of the operational amplifier OP40 may be regarded as the output impedance of the first gain adjustment circuit 342.

[0146] Furthermore, for example, in a configuration in which the low-pass filter circuit 343 is connected to the first switching circuit 335 without passing through the first gain adjustment circuit 342, the output impedance Rp in equation (16) represents the output impedance of the first reference potential generation circuit 334. In this case, the output impedance Rp is expressed by equation (17).

[0147] Rp=(R 32 ·R 33 ) / (R 32 +R 33 ) …(17)

[0148] Furthermore, for example, it is preferable that the low-pass filter circuit 343 be designed so that the relationship between the time ts, which is the time it takes for the potential of the detection signal Vout input to the first inspection signal generation circuit 340 as the first input signal Vs1 to change from the maximum value to the minimum value, and the time constant τ satisfies equation (18).

[0149] ts / 2≒τ~4.6τ …(18)

[0150] "τ" in equation (18) corresponds to the time until the charge or discharge of capacitor C40 reaches approximately 63%, and "4.6τ" in equation (18) corresponds to the time until the charge or discharge of capacitor C40 reaches approximately 100%. Therefore, equation (18) means that half of the time ts is included in the range from the time until the charge or discharge of capacitor C40 reaches approximately 63% to the time until the charge or discharge of capacitor C40 reaches approximately 100%.

[0151] Here, in the first filter circuit 344 downstream of the low-pass filter circuit 343, a circuit including a capacitor C41, a resistor R42, and an operational amplifier OP42 functions as a differentiation circuit. Therefore, if noise is superimposed on the detection signal Vout input to the first inspection signal generation circuit 340 or if the detection signal Vout includes a steep potential change, distortion may occur in the first filter output signal Obpf1 output from the first filter circuit 344. If distortion occurs in the first filter output signal Obpf1, the amplitude value of the first inspection signal Vd1 generated as a pseudo residual vibration signal may vary greatly, potentially reducing the accuracy of determining the state of the ejection section D. Therefore, in this embodiment, distortion in the first filter output signal Obpf1 is suppressed by stabilizing the potential of the first input signal Vs1 during a non-detection period, which is a period during which the detection signal Vout is not input to the first inspection signal generation circuit 340. Specifically, in this embodiment, the first switching circuit 335 and the low-pass filter circuit 343 cause the potential of the first input signal Vs1 during the non-detection period to converge to the first reference potential Vref1, thereby suppressing distortion in the first filter output signal Obpf1.

[0152] Next, the effects of the first switching circuit 335 and the low-pass filter circuit 343 will be described with reference to FIG.

[0153] 14 is an explanatory diagram illustrating the effects of first switching circuit 335 and low-pass filter circuit 343. Note that "with distortion countermeasures" in FIG. 14 shows simulation results for first filter circuit 344 when first switching circuit 335 and low-pass filter circuit 343 are provided upstream of first filter circuit 344. Also, "comparison" in FIG. 14 shows simulation results for first filter circuit 344 when first switching circuit 335 and low-pass filter circuit 343 are not provided upstream of first filter circuit 344. However, in the comparison, a switch that simply switches whether or not switching circuit 31 and detection circuit 33 are electrically connected is provided instead of first switching circuit 335.

[0154] 14, in the comparative example in which the first switching circuit 335 and the low-pass filter circuit 343 are not provided, noise occurs in the first filter input signal INbpf1 in the period before the start of the detection period Tdet1. Also, in the comparative example, the potential of the first filter input signal INbpf1 changes suddenly at the end of the detection period Tdet1. Therefore, in the comparative example, distortion occurs in the first filter output signal Obpf1 in the period before the start of the detection period Tdet1 and at the end of the detection period Tdet1.

[0155] In contrast, in a configuration provided with the first switching circuit 335 and the low-pass filter circuit 343, the occurrence of noise in the first filter input signal INbpf1 and the sudden change in potential of the first filter input signal INbpf1 are suppressed. As a result, in a configuration provided with the first switching circuit 335 and the low-pass filter circuit 343, the occurrence of distortion in the first filter output signal Obpf1 is suppressed.

[0156] In this way, in this embodiment, distortion of the first filter output signal Obpf1 is suppressed, and therefore, it is possible to suppress variations in the amplitude value of the first inspection signal Vd1 generated as a pseudo residual vibration signal. As a result, in this embodiment, it is possible to accurately determine the state of the discharge section D.

[0157] As shown in FIG. 14, the first filter circuit 344 can output a first filter output signal Obpf1 having one or more periods based on a first filter input signal INbpf1 having one or more and less than one period.

[0158] Next, the operation of the inkjet printer 1 will be described with reference to FIG.

[0159] 15 is a timing chart showing an example of the operation of the inkjet printer 1 in a unit period TU. In this embodiment, when the inkjet printer 1 executes a printing process or a discharge state determination process, one or more unit periods TU are set as the operating period of the inkjet printer 1. The inkjet printer 1 according to this embodiment can drive each discharge section D[m] for the printing process or the discharge state determination process in each unit period TU. For example, when executing a discharge state determination process, the inkjet printer 1 can drive the discharge section D to be determined in each unit period TU and detect the detection signal Vout[m] from the discharge section D to be determined.

[0160] The control unit 2 outputs a latch signal LAT having a pulse PlsL, thereby defining a unit period TU as the period from the rising edge of one pulse PlsL to the rising edge of the next pulse PlsL.

[0161] The print signal SI includes, for example, M individual designation signals Sd[1] to Sd[M] that correspond one-to-one to the M discharge sections D[1] to D[M]. The individual designation signal Sd[m] specifies the drive mode of the discharge section D[m] during each unit period TU when the inkjet printer 1 executes a printing process or a discharge state determination process. For example, prior to each unit period TU, the control unit 2 supplies the print signal SI, including the individual designation signals Sd[1] to Sd[M], to the connection state designation circuit 310 in synchronization with the clock signal CL. The connection state designation circuit 310 then generates connection state designation signals Qa[m] and Qs[m] during that unit period TU based on the individual designation signal Sd[m]. The connection state designation circuit 310 also generates a selection signal SEL and a detection period signal Acut based on at least some of the print signal SI, the latch signal LAT, and the period definition signal Tsig.

[0162] For example, in a unit period TU in which a printing process is executed, an individual designation signal Sd[m] designates a discharge unit D[m] as either a discharge unit D that forms dots or a discharge unit D that does not form dots. Also, for example, in a unit period TU in which a discharge state determination process is executed, an individual designation signal Sd[m] designates whether or not the discharge unit D[m] is driven as a discharge unit D to be determined. Note that FIG. 15 shows connection state designation signals Qa[m] and Qs[m] when the discharge unit D[m] is designated as a discharge unit D to be determined by the individual designation signal Sd[m] in the unit period TU in which a discharge state determination process is executed. FIG. 15 will mainly describe the operation of the inkjet printer 1 when a discharge state determination process is executed.

[0163] When the ejection state determination process is executed, for example, the control unit 2 outputs a period definition signal Tsig having a pulse PlsT1 and a pulse PlsT2, thereby dividing the unit period TU into a control period TSS1 from the start of the pulse PlsL to the start of the pulse PlsT1, and a control period TSS2 from the start of the pulse PlsT1 to the start of the next pulse PlsL.

[0164] The connection state specification circuit 310 also controls the detection period signal Acut to define the detection period Tdet1 of the detection signal Vout[m]. For example, the connection state specification circuit 310 sets the detection period signal Acut to a low level when the pulse PlsT1 ends and sets the detection period signal Acut to a high level when the pulse PlsT2 starts. The time from the start to the end of the detection period Tdet1 corresponds to the time allocated to detecting the residual vibration of the discharge section D. Note that FIG. 15 shows the detection period Tdet1 when the detection signal Vout[m] is supplied to the first inspection signal generation circuit 340. When the detection signal Vout[m] is supplied to the first inspection signal generation circuit 340, a pseudo residual vibration signal that imitates the residual vibration of the discharge section D[m] is generated during the inspection period Tche. In FIG. 15, the selection signal SEL is maintained at a high level because it is assumed that the detection signal Vout[m] is supplied to the first inspection signal generation circuit 340.

[0165] Furthermore, the drive signal COM used in the ejection state determination process has, for example, a pulse PA that is supplied to the wiring La during the control period TSS1. The pulse PA used in the ejection state determination process may be a pulse that does not cause ink to be ejected from the nozzle N, or a pulse that causes ink to be ejected from the nozzle N, as long as it is a pulse that causes vibrations in the diaphragm 321. In this embodiment, it is assumed that the pulse PA is a pulse that does not cause ink to be ejected from the nozzle N. Note that in the printing process, instead of the pulse PA, a pulse that causes ink to be ejected from the nozzle N is supplied to the wiring La during the unit period TU.

[0166] The pulse PA has a waveform in which the potential of the drive signal COM changes from potential V0 to potential VLa, which is lower than potential V0, and then returns to potential V0. Potential V0 is the potential at the start and end of the pulse PA, and is the reference potential of the drive signal COM.

[0167] For example, the pulse PA has a waveform element Pa1 whose potential changes from potential V0 to potential VLa, a waveform element Pa2 whose potential is maintained at the potential VLa at the end of the waveform element Pa1, and a waveform element Pa3 whose potential changes from potential VLa to potential V0. Hereinafter, the waveform elements Pa1, Pa2, and Pa3 may be collectively referred to as waveform element Pa.

[0168] The waveform element Pa1 is an expansion element that displaces the piezoelectric body Zb in the Z2 direction. In the expansion element, the potential of the drive signal COM changes to drive the piezoelectric element PZ so as to expand the volume of the cavity CV. Therefore, in the waveform element Pa1, the potential of the drive signal COM changes to expand the volume of the cavity CV. When the volume of the cavity CV expands, the surface of the ink in the nozzle N is pulled in the Z2 direction, which is the opposite direction to the ejection direction, as in the state of Phase-2 shown in Figure 4. Hereinafter, pulling the surface of the ink in the nozzle N in the direction opposite to the ejection direction may be referred to as "pull."

[0169] The waveform element Pa2 is a maintaining element for maintaining the position of the piezoelectric body Zb in the Z-axis direction. For example, the waveform element Pa2 maintains the potential of the drive signal COM to drive the piezoelectric element PZ so as to maintain the volume of the cavity CV expanded by the waveform element Pa1.

[0170] Furthermore, the waveform element Pa3 is a contraction element for displacing the piezoelectric body Zb in the Z1 direction. In the contraction element, the potential of the drive signal COM changes to drive the piezoelectric element PZ so as to contract the volume of the cavity CV. Therefore, in the waveform element Pa3, the potential of the drive signal COM changes to contract the volume of the cavity CV. When the volume of the cavity CV contracts, the surface of the ink in the nozzle N is pushed in the Z1 direction, which is the ejection direction. In this embodiment, the waveform element Pa3 pushes the surface of the ink in the nozzle N in the Z1 direction to the extent that ink is not ejected from the nozzle N. Hereinafter, pushing the surface of the ink in the nozzle N in the ejection direction may be referred to as a push.

[0171] In this way, the pulse PA has a so-called pull-push waveform. However, the waveform of the drive signal COM that does not cause ink to be ejected from the nozzle N is not limited to a pull-push waveform.

[0172] Furthermore, for example, when the individual designation signal Sd[m] designates the discharge unit D[m] as the discharge unit D to be determined, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a high level and the connection state designation signal Qs[m] to a low level during the control period TSS1. Then, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a low level and the connection state designation signal Qs[m] to a high level during the control period TSS2.

[0173] When the control period TSS1 and the control period TSS2 switch, it is preferable that the states of the switches SWa[m] and SWs[m] switch between on and off via a state in which both the switches SWa[m] and SWs[m] are on. That is, it is preferable that the timing at which the connection state designation signal Qs[m] transitions from a low level to a high level occurs before the timing at which the connection state designation signal Qa[m] transitions from a high level to a low level. It is also preferable that the timing at which the connection state designation signal Qs[m] transitions from a high level to a low level occurs after the timing at which the connection state designation signal Qa[m] transitions from a low level to a high level. In this case, when the control period TSS1 and the control period TSS2 switch, a state in which both the switches SWa[m] and SWs[m] are off does not occur, so that it is possible to prevent the potential of the node N2 shown in FIG. 6 from changing due to switching noise, etc.

[0174] Furthermore, the timing at which the detection period signal Acut transitions from a high level to a low level is preferably later than the timing at which the connection state designation signal Qa[m] transitions from a high level to a low level and the timing at which the connection state designation signal Qs[m] transitions from a low level to a high level. Furthermore, the timing at which the detection period signal Acut transitions from a low level to a high level is preferably earlier than the timing at which the connection state designation signal Qa[m] transitions from a low level to a high level and the timing at which the connection state designation signal Qs[m] transitions from a high level to a low level. Therefore, in this embodiment, as described above, the connection state designation circuit 310 sets the detection period signal Acut to a low level upon the end of the pulse PlsT1 and sets the detection period signal Acut to a high level upon the start of the pulse PlsT2. In addition, if the above-mentioned transition timing is satisfied, the connection state specification circuit 310 may set the detection period signal Acut to a low level at the start of the pulse PlsT1, and may set the detection period signal Acut to a high level at the start of the next pulse PlsL.

[0175] By ensuring that the timing at which the level of the detection period signal Acut transitions satisfies the above-mentioned transition timing, it is possible to prevent noise and the like from occurring in the first input signal Vs1 and the second input signal Vs2. Note that, as long as noise and the like occurring in the first input signal Vs1 and the second input signal Vs2 is suppressed within an acceptable range, the timing at which the level of the detection period signal Acut transitions does not need to satisfy the above-mentioned transition timing.

[0176] The piezoelectric element PZ[m] of the ejection section D[m] to be determined is driven by the pulse PA of the drive signal COM during the control period TSS1. Specifically, the piezoelectric element PZ[m] of the ejection section D[m] to be determined is displaced by the pulse PA of the drive signal COM during the control period TSS1. As a result, vibration occurs in the ejection section D[m] to be determined. The vibration that occurred during the control period TSS1 remains in the control period TSS2. Then, during the control period TSS2, the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] of the ejection section D[m] to be determined changes depending on the residual vibration occurring in the ejection section D[m] to be determined. That is, during the control period TSS2, the potential of the upper electrode Zu of the piezoelectric element PZ of the ejection section D to be determined becomes a potential corresponding to the electromotive force of the piezoelectric element PZ caused by the residual vibration occurring in the ejection section D to be determined. Then, the potential of the upper electrode Zu is detected as a potential signal Vzu during the control period TSS2. As a result, a change in the potential of the upper electrode Zu is detected as a detection signal Vout during the control period TSS2. As a result, the detection signal Vout is input to the detection circuit 33 as a residual vibration signal generated in accordance with the vibration remaining in the ejection section D.

[0177] The detection signal Vout input to the detection circuit 33 is supplied as a first input signal Vs1 to the first inspection signal generation circuit 340 during a detection period Tdet1 of the control period TSS2. As a result, during a test period Tche following the detection period Tdet1, the first inspection signal Vd1 is generated by the first inspection signal generation circuit 340 as a pseudo residual vibration signal that imitates the residual vibration of the ejection section D[m].

[0178] Next, we will briefly explain the operation of the inkjet printer 1 when a printing process is performed. Note that in a printing process, the unit period TU does not have to be divided into a control period TSS1 and a control period TSS2. In this case, during the unit period TU, the period defining signal Tsig may be maintained at a low level, and the detection period signal Acut may be maintained at a high level.

[0179] The connection state designation signal Qs[m] is maintained at a low level during the unit period TU, regardless of whether the discharge unit D[m] is designated as the discharge unit D that forms dots. The connection state designation signal Qa[m] is set to a high level or a low level depending on whether the discharge unit D[m] is designated as the discharge unit D that forms dots.

[0180] For example, when the individual designation signal Sd[m] designates a discharge unit D[m] as a discharge unit D that forms dots, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to high level during the unit period TU. Note that the connection state designation signal Qa corresponding to a discharge unit D that does not form dots is set to low level during the unit period TU.

[0181] When the connection state designation signal Qa[m] is set to a high level, a drive signal COM including a pulse for ejecting ink from nozzle N is supplied from the drive signal generation unit 4 to the ejection section D that forms dots. For example, a pulse for ejecting ink from nozzle N is supplied to the wiring La for a unit period TU. The pulse for ejecting ink from nozzle N may have a pull-push waveform, similar to the pulse PA. In this case, the pulse for ejecting ink from nozzle N is determined so that the potential difference between the start and end of the contraction element, which is the waveform element for ejecting ink, is greater than the potential difference between the start and end of the waveform element Pa3 of the pulse PA. Note that the pulse for ejecting ink from nozzle N is not limited to a pull-push waveform. For example, the pulse for ejecting ink from nozzle N may have a pull-push-pull waveform.

[0182] Each waveform element of the pulse that ejects ink from the nozzle N is determined so that a predetermined amount of ink is ejected from the ejection section D[m] when an individual drive signal Vin[m] having that pulse is supplied to the ejection section D[m]. In this embodiment, it is assumed that when the potential of the individual drive signal Vin[m] is high, the volume of the cavity CV of the ejection section D[m] is smaller than when the potential is low. Therefore, when the ejection section D[m] is driven by the individual drive signal Vin[m] having a pulse that ejects ink, the ink in the ejection section D[m] is ejected from the nozzle N by the waveform element in which the potential of the individual drive signal Vin[m] changes from low to high.

[0183] For example, each waveform element of a pulse that ejects ink from a nozzle N is determined based on the ink ejection characteristics of the ejection unit D. The ink ejection characteristics include, for example, the amount of ink ejected as an ink droplet and the ejection speed of the ejected ink droplet. The ejection speed of an ink droplet varies depending on, for example, the viscosity of the ink. For example, the ejection speed of an ink droplet that has a viscosity higher than a predetermined viscosity is lower than the ejection speed of an ink droplet that has a viscosity lower than the predetermined viscosity. Details will be described later with reference to FIG. 16, but in this embodiment, the viscosity state of the ink in the ejection unit D can be determined based on the pseudo residual vibration signal.

[0184] In this embodiment, it is assumed that the pulse PA is a pulse that does not cause ink to be ejected from the nozzles N, and therefore the ejection state determination process can be executed even when the head unit 3 is not positioned above the discharged ink receiving unit 80. For example, when printing is performed pass by pass while moving the head unit 3 along the X-axis direction, the ejection state determination process may be executed between passes. Furthermore, the ejection state determination process may be executed between a print job based on one print data IMG and a print job based on another print data IMG. Alternatively, the ejection state determination process may be executed when a maintenance process is executed.

[0185] The operation of the inkjet printer 1 is not limited to the example shown in Figure 15. For example, the pulse PA may be a pulse that causes ink to be ejected from the nozzle N. In this case, the drive signal COM including the pulse PA may be used in both the printing process and the ejection state determination process. However, if the pulse PA used in the ejection state determination process is a pulse that causes ink to be ejected from the nozzle N, it is preferable that the ejection state determination process be performed with the head unit 3 positioned above the discharged ink receiver 80, for example.

[0186] Furthermore, for example, when the ejection state determination process is executed, the control unit 2 may output a period definition signal Tsig that includes only the pulse PlsT1 of the pulses PlsT1 and PlsT2. In this case, the connection state designation circuit 310 may set the detection period signal Acut to a low level when the pulse PlsT1 starts or ends, and may set the detection period signal Acut to a high level when the next pulse PlsL starts, so as to satisfy the transition timing described above.

[0187] 15 illustrates an example in which there is one drive signal COM, but the present invention is not limited to this. For example, multiple drive signals COM may be used, including a drive signal COM that does not cause ink to be ejected from nozzle N and a drive signal COM that causes ink to be ejected from nozzle N. In this case, the pulse PA that does not cause ink to be ejected may be used to prevent the ink from thickening during printing. Furthermore, the drive signal COM that causes ink to be ejected from nozzle N may have multiple pulses that cause ink to be ejected from nozzle N to form dots of different sizes.

[0188] Next, the first inspection signal Vd1 generated by the first inspection signal generating circuit 340 will be described with reference to FIG.

[0189] FIG. 16 is an explanatory diagram illustrating an example of the first inspection signal Vd1 generated by the first inspection signal generation circuit 340. In FIG. 16, for ease of understanding, the numerals 1, 2, and 3 are added to the end of each of the reference symbols of the multiple unit periods TU. Also, in FIG. 16, it is assumed that the ejection unit D[a] is designated as the ejection unit D to be determined in the unit period TU1, and the ejection unit D[b] is designated as the ejection unit D to be determined in the unit period TU2. The value a is a natural number that satisfies "1≦a≦M," and the value b is a natural number that satisfies "1≦b≦M" and is different from the value a. Furthermore, the time ts is the time during the detection period Tdet1 during which the potential of the detection signal Vout input to the first inspection signal generation circuit 340 changes from the maximum value to the minimum value, or the time during which the potential of the detection signal Vout changes from the minimum value to the maximum value.

[0190] During the detection period Tdet1, during which the detection period signal Acut is at a low level, the detection signal Vout is input as the first input signal Vs1 to the first inspection signal generation circuit 340. For example, during the detection period Tdet1[a] of the unit period TU1, the detection signal Vout indicating the residual vibration of the ejector D[a] driven by the individual drive signal Vin[a] is input as the first input signal Vs1 to the first inspection signal generation circuit 340. Then, upon the end of the detection period Tdet1[a], the first input signal Vs1 switches from the detection signal Vout to the first reference potential Vref1. As a result, the potential of the first input signal Vs1 converges to the first reference potential Vref1 during the inspection period Tche[a].

[0191] 16 , the detection signal Vout input to the first inspection signal generation circuit 340 as the first input signal Vs1 is a detection signal Vout with less than one cycle. Therefore, in the first inspection signal generation circuit 340, the length of the detection period Tdet1 can be made shorter than in the second inspection signal generation circuit 350, in which the detection signal Vout with one cycle or more is input as the second input signal Vs2. As a result, in this embodiment, the unit period TU when the inspection signal VD is generated by the first inspection signal generation circuit 340 can be made shorter than the unit period TU when the inspection signal VD is generated by the second inspection signal generation circuit 350.

[0192] Furthermore, during the inspection period Tche[a] following the detection period Tdet1[a], the wiring Ls2 connecting the switching circuit 31 and the detection circuit 33 is electrically disconnected from the first inspection signal generation circuit 340. Therefore, even if the individual drive signal Vin[b] is supplied to the ejection section D[b] during the inspection period Tche[a], the first inspection signal generation circuit 340 can generate the first inspection signal Vd1 that imitates the attenuated wave of the detection signal Vout that indicates the residual vibration of the ejection section D[a].

[0193] For example, as described in FIG. 11 , the first filter circuit 344 is a multiple-feedback bandpass filter having a characteristic in which the group delay changes significantly around the center frequency f0. Therefore, a damped oscillation waveform corresponding to the detection signal Vout is generated at the center frequency f0. After the input of the detection signal Vout to the first filter circuit 344 ends, that is, after the detection period Tdet1 ends, a first filter output signal Obpf1 having a damped oscillation waveform generated at the center frequency f0 is output from the first filter circuit 344. As a result, for example, during the inspection period Tche[a], a first inspection signal Vd1 having a damped oscillation waveform corresponding to the detection signal Vout indicating the residual vibration of the ejection section D[a] is output from the first inspection signal generation circuit 340 to the inspection unit 6. Furthermore, for example, during the inspection period Tche[b], a first inspection signal Vd1 having a damped oscillation waveform corresponding to the detection signal Vout indicating the residual vibration of the ejection section D[b] is output from the first inspection signal generation circuit 340 to the inspection unit 6.

[0194] The inspection unit 6 determines the state of the discharge portion D[a] based on the first inspection signal Vd1 output from the first inspection signal generation circuit 340 as the inspection signal VD[a] during the inspection period Tche[a]. The inspection unit 6 also determines the state of the discharge portion D[b] based on the first inspection signal Vd1 output from the first inspection signal generation circuit 340 as the inspection signal VD[b] during the inspection period Tche[b]. The inspection unit 6 may also determine the state of the discharge portion D based on the first inspection signal Vd1 output from the first inspection signal generation circuit 340 as the inspection signal VD during a period including the detection period Tdet1 and the inspection period Tche. That is, the inspection unit 6 may determine the state of the discharge portion D based on the first inspection signal Vd1 output from the first inspection signal generation circuit 340 during the inspection period Tche and the first inspection signal Vd1 output from the first inspection signal generation circuit 340 during the detection period Tdet1.

[0195] 16, the solid line waveform of the first input signal Vs1 indicates the waveform of the first input signal Vs1 when the state of the ejection section D is normal, and the dashed line waveform of the first input signal Vs1 indicates the waveform of the first input signal Vs1 when the ink in the ejection section D is in a viscous state. Similarly, the solid line waveform of the test signal VD indicates the waveform of the test signal VD when the state of the ejection section D is normal, and the dashed line waveform of the test signal VD indicates the waveform of the test signal VD when the ink in the ejection section D is in a viscous state. As shown in FIG. 16, the amplitude of the test signal VD differs between when the state of the ejection section D is normal and when the ink in the ejection section D is in a viscous state.

[0196] For example, the amplitude of the test signal VD when the ink in the discharge section D is in a thickened state is smaller than the amplitude of the test signal VD when the state of the discharge section D is normal. The difference dA11 in FIG. 16 indicates the difference between the amplitude of the first peak of the test signal VD during the test period Tche when the state of the discharge section D is normal and the amplitude of the first peak of the test signal VD during the test period Tche when the ink in the discharge section D is in a thickened state. Furthermore, the difference dA21 in FIG. 16 indicates the difference between the amplitude of the second peak of the test signal VD during the test period Tche when the state of the discharge section D is normal and the amplitude of the second peak of the test signal VD during the test period Tche when the ink in the discharge section D is in a thickened state.

[0197] The inventors have confirmed through simulations that the rate of change in the amplitude of the test signal VD when the ejection section D is in a normal state and when the ink in the ejection section D is in a thickened state is approximately the same as when the second test signal Vd2 is used as the test signal VD. For example, in a simulation using the first test signal Vd1 as the test signal VD, the rate of change calculated based on the difference dA11, i.e., the rate of change in the amplitude of the first peak of the test signal VD during the test period Tche, is 43%. Furthermore, the simulation result for the rate of change calculated based on the difference dA21, i.e., the rate of change in the amplitude of the second peak of the test signal VD during the test period Tche, is 54%. In contrast, in a simulation using the second test signal Vd2 as the test signal VD, the rate of change calculated based on the difference dA12 shown in FIG. 17 is 36%, and the rate of change calculated based on the difference dA22 shown in FIG. 17 is 50%. The first peak of the inspection signal VD in the inspection period Tche corresponds to the second peak of the inspection signal VD in the period including the detection period Tdet1 and the inspection period Tche. Therefore, the differences dA12 and dA22 shown in FIG. 17 correspond to the differences dA11 and dA21, respectively.

[0198] In this way, even when the first inspection signal Vd1 is used as the inspection signal VD, the state of the ejection section D can be determined based on the rate of change of the amplitude of the inspection signal VD relative to the reference amplitude value. The reference amplitude value is determined in advance based on, for example, the amplitude of the inspection signal VD when the state of the ejection section D is normal.

[0199] The method for determining the amplitude of the inspection signal VD is not particularly limited, and any known method can be used. For example, the inspection unit 6 may compare the potential of the inspection signal VD with multiple different thresholds, generate multiple pulses each indicating the comparison result between the multiple thresholds and the potential of the inspection signal VD, and determine the amplitude of the inspection signal VD based on the width of the generated multiple pulses. The pulse indicating the comparison result between the threshold and the potential of the inspection signal VD is, for example, a pulse that becomes high level while the potential of the inspection signal VD is equal to or higher than the threshold. For example, if the inspection unit 6 has a comparator that compares the potential of the inspection signal VD with multiple thresholds, the comparator may be provided within the head unit 3. In this case, the inspection unit 6 has a comparator provided within the head unit 3 and an element provided outside the head unit 3.

[0200] In this way, in this embodiment, part or all of the test period Tche[a], which generates the first test signal Vd1 corresponding to the residual vibration of the discharge section D[a], can be overlapped with the control period TSS1, which drives the discharge section D[b], which is different from the discharge section D[a]. Therefore, in this embodiment, by using the first test signal Vd1 as the test signal VD for determining the state of the discharge section D, it is possible to shorten the time required to determine the state of the multiple discharge sections D, including the discharge section D[a] and the discharge section D[b].

[0201] Next, the second test signal Vd2 generated by the second test signal generating circuit 350 will be described with reference to FIG.

[0202] FIG. 17 is an explanatory diagram illustrating an example of the second inspection signal Vd2 generated by the second inspection signal generation circuit 350. In FIG. 17, for ease of understanding, either the numeral 1 or 2 is added to the end of each of the reference symbols of the multiple unit periods TU. Also, in FIG. 17, it is assumed that the emission unit D[a] is designated as the emission unit D to be determined in the unit period TU1. The value a is a natural number satisfying "1≦a≦M". Also, in FIG. 17, the detection period Tdet1 when the first inspection signal Vd1 is used as the inspection signal VD is indicated by a dashed arrow.

[0203] During the detection period Tdet2, during which the detection period signal Acut is at a low level, the detection signal Vout is input as the second input signal Vs2 to the second inspection signal generation circuit 350. For example, during the detection period Tdet2[a] of the unit period TU1, the detection signal Vout indicating the residual vibration of the ejection section D[a] driven by the individual drive signal Vin[a] is input as the second input signal Vs2 to the second inspection signal generation circuit 350. Then, upon the end of the detection period Tdet2[a], the second input signal Vs2 switches from the detection signal Vout to the second reference potential Vref2. As a result, during the control period TSS1 of the unit period TU2, the potential of the second input signal Vs2 converges to the second reference potential Vref2.

[0204] 17, the detection signal Vout input to the second inspection signal generation circuit 350 as the second input signal Vs2 is a detection signal Vout with one or more cycles. Therefore, in the second inspection signal generation circuit 350, the length of the detection period Tdet2 is longer than the detection period Tdet1 when the first inspection signal Vd1 is used as the inspection signal VD.

[0205] 10, the second filter circuit 354 is a bandpass filter that passes signals of a predetermined frequency component. Therefore, a second filter output signal Obpf2, in which frequency components other than the predetermined frequency component have been removed from a second filter input signal INbpf2 obtained by adjusting the amplitude of the detection signal Vout, is output from the second filter circuit 354. As a result, for example, during the detection period Tdet2[a], a second inspection signal Vd2, in which frequency components other than the predetermined frequency component have been removed from a signal corresponding to the detection signal Vout indicating the residual vibration of the ejector D[a], is output from the second inspection signal generation circuit 350 to the inspection unit 6.

[0206] During the detection period Tdet2[a], the wiring Ls2 connecting the switching circuit 31 and the detection circuit 33 is electrically connected to the second inspection signal generation circuit 350. Therefore, when the state of the ejection unit D[a] is determined based on the second inspection signal Vd2, it is preferable not to drive the other ejection units D until the detection period Tdet2[a] ends, that is, until the generation of the second inspection signal Vd2 is completed.

[0207] As described above, the second inspection signal generation circuit 350 generates the second inspection signal Vd2 based on one or more cycles of the detection signal Vout during the detection period Tdet2[a]. Therefore, the inspection unit 6 determines the state of the ejection section D[a] based on the second inspection signal Vd2 output from the second inspection signal generation circuit 350 as the inspection signal VD[a] during the detection period Tdet2[a].

[0208] 17, the solid line waveform of the second input signal Vs2 indicates the waveform of the second input signal Vs2 when the state of the ejection section D is normal, and the dashed line waveform of the second input signal Vs2 indicates the waveform of the second input signal Vs2 when the ink in the ejection section D is in a viscous state. Similarly, the solid line waveform of the test signal VD indicates the waveform of the test signal VD when the state of the ejection section D is normal, and the dashed line waveform of the test signal VD indicates the waveform of the test signal VD when the ink in the ejection section D is in a viscous state. Even when the test signal VD is generated by the second test signal generation circuit 350, as shown in FIG. 17, the amplitude of the test signal VD differs between when the state of the ejection section D is normal and when the ink in the ejection section D is in a viscous state.

[0209] For example, the amplitude of the test signal VD when the ink in the discharge section D is in a thickened state is smaller than the amplitude of the test signal VD when the state of the discharge section D is normal. The difference dA12 in FIG. 17 indicates the difference between the amplitude of the second peak of the test signal VD in the detection period Tdet2 when the state of the discharge section D is normal and the amplitude of the second peak of the test signal VD in the detection period Tdet2 when the ink in the discharge section D is in a thickened state. Furthermore, the difference dA22 in FIG. 17 indicates the difference between the amplitude of the third peak of the test signal VD in the detection period Tdet2 when the state of the discharge section D is normal and the amplitude of the third peak of the test signal VD in the detection period Tdet2 when the ink in the discharge section D is in a thickened state.

[0210] The second peak of the inspection signal VD in the detection period Tdet2 shown in Fig. 17 corresponds to the first peak of the inspection signal VD in the inspection period Tche shown in Fig. 16. The third peak of the inspection signal VD in the detection period Tdet2 shown in Fig. 17 corresponds to the second peak of the inspection signal VD in the inspection period Tche shown in Fig. 16.

[0211] In this way, even when the second inspection signal Vd2 is used as the inspection signal VD, the state of the ejection section D can be determined based on the rate of change of the amplitude of the inspection signal VD relative to the reference amplitude value, just as when the first inspection signal Vd1 is used as the inspection signal VD.

[0212] Furthermore, as described above, the second inspection signal Vd2 is generated based on one or more cycles of the detection signal Vout. Therefore, in this embodiment, the state of the ejection section D may be determined based on some or all of the amplitude, cycle, and phase of the second inspection signal Vd2. Furthermore, in this embodiment, multiple abnormal states, including the thickened state of ink in the ejection section D, can be determined based on the second inspection signal Vd2 generated based on one or more cycles of the detection signal Vout. Examples of abnormal states other than the thickened state of ink in the ejection section D include a state in which an ejection abnormality occurs due to air bubbles entering the cavity CV of the ejection section D, and a state in which an ejection abnormality occurs due to foreign matter adhering near the nozzle N of the ejection section D. For example, determining the state of the ejection section D in the second mode, in which the state of the ejection section D is determined based on the second inspection signal Vd2, is effective when it is desired to accurately determine the cause of the ejection abnormality.

[0213] Note that determining the state of the ejection section D in the first mode, which determines the state of the ejection section D based on the first inspection signal Vd1, can shorten the unit period TU compared to the second mode, making it effective for determining the state of the ejection section D in a short time. For example, immediately after starting up the inkjet printer 1, the ink in the cavity CV is likely to be stagnant and thickened. For this reason, determining the state of the ejection section D in the first mode may be prioritized over determining the state of the ejection section D in the second mode after starting up the inkjet printer 1. In this case, it is possible to prevent an increase in the time required to determine the state of the ejection section D after starting up the inkjet printer 1. As such, in this embodiment, the mode for determining the state of the ejection section D can be switched depending on the purpose of determining the state of the ejection section D and the situation in which the determination is made. For example, the first mode may be a mode in which the viscosity of the ink in the ejection section D is determined based on the first inspection signal Vd1. Furthermore, the second mode may be a mode in which multiple abnormal conditions, including the viscosity of the ink in the ejection section D, are determined based on the second inspection signal Vd2.

[0214] As described above, in this embodiment, the inkjet printer 1 includes a head unit 3, a drive signal generation unit 4 that generates a drive signal COM, and an inspection unit 6 that selectively receives either a pseudo residual vibration signal or a detected residual vibration signal and determines the state of the ejection section D based on the received signal. The head unit 3 includes a nozzle N, a piezoelectric element PZ driven by the drive signal COM, and an ejection section D that includes a cavity CV that ejects ink from the nozzle N in response to the driving of the piezoelectric element PZ. The head unit 3 also includes a first inspection signal generation circuit 340 that receives a residual vibration signal generated by vibrations remaining in the ejection section D after the piezoelectric element PZ is driven and generates a pseudo residual vibration signal in response to the residual vibration signal. The second inspection signal generation circuit 350 receives the residual vibration signal and generates a detected residual vibration signal by removing frequency components other than predetermined frequency components from the residual vibration signal. In this embodiment, the head unit 3 also includes a second selection circuit 360 that switches between supplying the pseudo residual vibration signal to the inspection unit 6 that determines the state of the ejection section D or supplying the detected residual vibration signal to the inspection unit 6. In this embodiment, for example, the detection signal Vout is input as a residual vibration signal to the first inspection signal generation circuit 340, and the first inspection signal generation circuit 340 generates a first inspection signal Vd1 as a pseudo residual vibration signal. Also, for example, the detection signal Vout is input as a residual vibration signal to the second inspection signal generation circuit 350, and the second inspection signal generation circuit 350 generates a second inspection signal Vd2 as a detected residual vibration signal.

[0215] As described above, in the present embodiment, the pseudo residual vibration signal generated by the first inspection signal generating circuit 340 or the detected residual vibration signal generated by the second inspection signal generating circuit 350 is used as a signal for determining the state of the ejection unit D. For example, in the present embodiment, by determining the state of the ejection unit D using a pseudo residual vibration signal generated based on a residual vibration signal of less than one cycle, the time allocated to detecting the residual vibration signal can be shortened compared to when the state of the ejection unit D is determined using a detected residual vibration signal. Therefore, in the present embodiment, when determining the state of the ejection unit D, the pseudo residual vibration signal generated by the first inspection signal generating circuit 340 is used to determine the state of the ejection unit D, thereby preventing the length of the unit period TU, which is the cycle for driving the ejection unit D, from increasing. That is, in the present embodiment, by determining the state of the ejection unit D using the pseudo residual vibration signal generated by the first inspection signal generating circuit 340, the length of the unit period TU when determining the state of the ejection unit D can be shortened. Furthermore, in the present embodiment, the state of the ejection unit D can be determined, as necessary, using a detected residual vibration signal obtained by removing frequency components other than predetermined frequency components from the residual vibration signal. That is, in this embodiment, it is possible to appropriately switch between determining the state of the discharge section D using the pseudo residual vibration signal and determining the state of the discharge section D using the detected residual vibration signal.

[0216] Furthermore, in this embodiment, the head unit 3 further includes a first switching circuit 335 that switches whether to input the residual vibration signal to the first inspection signal generating circuit 340, and a second switching circuit 337 that switches whether to input the residual vibration signal to the second inspection signal generating circuit 350. As a result, in this embodiment, it is possible to easily switch between generating the signal for determining the state of the ejection section D in the first inspection signal generating circuit 340 or the second inspection signal generating circuit 350. That is, in this embodiment, it is possible to easily switch between determining the state of the ejection section D using the pseudo residual vibration signal or determining the state of the ejection section D using the detected residual vibration signal. Furthermore, in this embodiment, it is possible to prevent unnecessary operation of the circuits of the first inspection signal generating circuit 340 and the second inspection signal generating circuit 350 that do not generate signals for determining the state of the ejection section D. Therefore, in this embodiment, it is possible to prevent noise and the like from occurring in the signals for determining the state of the ejection section D.

[0217] Furthermore, in this embodiment, the second selection circuit 360 exclusively switches between supplying a pseudo residual vibration signal to the inspection unit 6 and supplying a detected residual vibration signal to the inspection unit 6 based on the selection signal SEL. As a result, in this embodiment, it is possible to prevent signals that are not used to determine the state of the discharge section D, out of the pseudo residual vibration signal and the detected residual vibration signal, from being supplied to the inspection unit 6 during the period in which the inspection unit 6 is determining the state of the discharge section D. Therefore, in this embodiment, it is possible to prevent noise and the like from occurring in the inspection unit 6 during the period in which the inspection unit 6 is determining the state of the discharge section D.

[0218] Furthermore, in this embodiment, the first inspection signal generating circuit 340 includes a low-pass filter circuit 343 and a first filter circuit 344 that receives the residual vibration signal via the low-pass filter circuit 343 and generates a pseudo residual vibration signal. As a result, in this embodiment, the first filter circuit 344 can generate a pseudo residual vibration signal based on the residual vibration signal from which noise and the like have been removed. As a result, in this embodiment, it is possible to suppress distortion from occurring in the pseudo residual vibration signal.

[0219] Furthermore, in this embodiment, the inspection unit 6 determines the viscosity state of the ink in the ejection section D based on the pseudo residual vibration signal. That is, the pseudo residual vibration signal is used to determine the viscosity state of the ink in the ejection section D. Therefore, in this embodiment, it is possible to suppress an increase in the time required to determine the viscosity state of the ink in the ejection section D. For example, in this embodiment, it is possible to shorten the time required to determine the viscosity state of the ink in multiple ejection sections D.

[0220] Furthermore, in this embodiment, the inspection unit 6 determines multiple abnormal conditions, including the thickened state of ink in the ejection section D, based on the detected residual vibration signal. That is, the detected residual vibration signal is used to determine multiple abnormal conditions, including the thickened state of ink in the ejection section D. In this way, in this embodiment, by using the detected residual vibration signal as a signal for determining the state of the ejection section D, it is possible to determine multiple abnormal conditions, including the thickened state of ink.

[0221] [2. Modifications] Each of the above embodiments can be modified in various ways. Specific modified embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within a range that does not contradict each other. In the modified examples exemplified below, elements whose actions and functions are equivalent to those of the embodiments will be designated by the same reference numerals as in the above description, and detailed descriptions of each will be omitted as appropriate.

[0222] [First Modification] In the above-described embodiment, some elements of the first filter circuit 344 may also be used as the second filter circuit 354 .

[0223] Fig. 18 is a block diagram showing an example of the configuration of a detection circuit 33A according to Modification 1. Elements similar to those described in Figs. 1 to 17 are given the same reference numerals, and detailed description thereof will be omitted.

[0224] The inkjet printer 1 according to this modification is similar to the inkjet printer 1 shown in Fig. 1, except that it has a detection circuit 33A shown in Fig. 18 instead of the detection circuit 33 shown in Fig. 1. The detection circuit 33A has, for example, a first selection circuit 330, a first gain adjustment circuit 342, a low-pass filter circuit 343, a second gain adjustment circuit 352, a third filter circuit 370, and a buffer circuit 372.

[0225] The first selection circuit 330, the first gain adjustment circuit 342, the low-pass filter circuit 343, and the second gain adjustment circuit 352 are respectively similar to the first gain adjustment circuit 342, the low-pass filter circuit 343, and the second gain adjustment circuit 352 shown in Fig. 7. However, a first filter input signal INbpf1 which is an output signal of the low-pass filter circuit 343, and a second filter input signal INbpf2 which is an output signal of the second gain adjustment circuit 352 are input to a third filter circuit 370.

[0226] The third filter circuit 370 is a filter circuit that switches between functioning as the first filter circuit 344 shown in Fig. 9 and functioning as the second filter circuit 354 shown in Fig. 10 based on a selection signal SEL. For example, the third filter circuit 370 functions as the first filter circuit 344 when the selection signal SEL is at a high level, and functions as the second filter circuit 354 when the selection signal SEL is at a low level. Note that, as will be described in detail later with reference to Fig. 19, in the third filter circuit 370, some of the elements of the first filter circuit 344 and the second filter circuit 354 are shared between the first filter circuit 344 and the second filter circuit 354.

[0227] The output signal of the third filter circuit 370 is supplied to a buffer circuit 372 as a filter output signal Obpf.

[0228] The buffer circuit 372 is a buffer that converts impedance and outputs a low-impedance inspection signal VD. For example, the buffer circuit 372 is configured as a voltage follower using an operational amplifier OP43, similar to the first buffer circuit 346 shown in FIG. 9. As a result, the filter output signal Obpf supplied to the buffer circuit 372 is output from the buffer circuit 372 as a low-impedance inspection signal VD.

[0229] Next, the third filter circuit 370 will be outlined with reference to FIG.

[0230] Fig. 19 is a circuit diagram showing an example of the configuration of a third filter circuit 370 according to the first modification. Elements similar to those described in Fig. 1 to Fig. 18 are given the same reference numerals, and detailed description thereof will be omitted.

[0231] 19 corresponds to the first filter circuit 344 shown in FIG. 9, and the second filter circuit 354A shown in FIG. 19 corresponds to the second filter circuit 354 shown in FIG. 10. As shown in FIG. 19, in the third filter circuit 370, the operational amplifier OP42 and the resistor element R42 are shared by the first filter circuit 344A and the second filter circuit 354A. When the third filter circuit 370 functions as the second filter circuit 354A, the operational amplifier OP42 and the resistor element R42 correspond to the operational amplifier OP51 and the resistor element R52 shown in FIG. 10, respectively.

[0232] The third filter circuit 370 includes, for example, resistors R41, R42, R43, and R51, capacitors C41, C42, and C52, an operational amplifier OP42, switches SW1, SW2, and SW3, and an inverter INV2.

[0233] One end of the resistor R41 is connected to the output terminal of the operational amplifier OP41 of the low-pass filter circuit 343, and the other end of the resistor R41 is connected to a node N41. One end of the capacitor C41 is connected to the node N41 via a switch SW1, and the other end of the capacitor C41 is connected to the inverting input terminal of the operational amplifier OP42. One end of the resistor R42 is connected to the inverting input terminal of the operational amplifier OP42, and the other end of the resistor R42 is connected to the output terminal of the operational amplifier OP42. One end of the resistor R43 is connected to the node N41, and the other end of the resistor R43 is connected to a line that supplies a first reference potential Vref1. One end of the capacitor C42 is connected to the node N41 via a switch SW2, and the other end of the capacitor C42 is connected to the output terminal of the operational amplifier OP42. The non-inverting input terminal of the operational amplifier OP42 is connected to a line that supplies the first reference potential Vref1.

[0234] One end of the resistor R51 is connected to the output terminal of the operational amplifier OP50 of the second gain adjustment circuit 352, and the other end of the resistor R51 is connected to one end of a capacitor C51, the other end of which is connected to the inverting input terminal of the operational amplifier OP42. One end of the capacitor C52 is connected to the inverting input terminal of the operational amplifier OP42 via the switch SW3, and the other end of the capacitor C52 is connected to the output terminal of the operational amplifier OP42.

[0235] The inverter INV2 outputs an inverted signal of the selection signal SEL supplied from the connection state specifying circuit 310 to the switch SW3.

[0236] The switch SW1 is turned on when the selection signal SEL is at a high level, electrically connecting the capacitor C41 and the node N41, and turned off when the selection signal SEL is at a low level, electrically disconnecting the capacitor C41 from the node N41. The switch SW2 is turned on when the selection signal SEL is at a high level, electrically connecting the capacitor C42 and the node N41, and turned off when the selection signal SEL is at a low level, electrically disconnecting the capacitor C42 from the node N41. The switch SW3 is turned on when the selection signal SEL is at a low level, electrically connecting the capacitor C52 and the inverting input terminal of the operational amplifier OP42, and turned off when the selection signal SEL is at a low level, electrically disconnecting the capacitor C52 from the inverting input terminal of the operational amplifier OP42.

[0237] For example, when the selection signal SEL is high, the second filter input signal INbpf2 is maintained at a constant potential, and the first filter input signal INbpf1 is input to the inverting input terminal of the operational amplifier OP42 via the resistor R41, the switch SW1, and the capacitor C41. The output signal of the operational amplifier OP42 is fed back to the inverting input terminal of the operational amplifier OP42 via the resistor R42. The output signal of the operational amplifier OP42 is also fed back to the inverting input terminal of the operational amplifier OP42 via the capacitor C42, the switch SW2, the switch SW1, and the capacitor C41. In this way, when the selection signal SEL is high, the third filter circuit 370 functions as a multiple feedback bandpass filter similar to the first filter circuit 344 shown in FIG. 9.

[0238] Furthermore, for example, when the selection signal SEL is at a low level, the first filter input signal INbpf1 is maintained at a constant potential, and the second filter input signal INbpf2 is input to the inverting input terminal of the operational amplifier OP42 via a resistor R51 and a capacitor C51. The output signal of the operational amplifier OP42 is fed back to the inverting input terminal of the operational amplifier OP42 via a resistor R42. The output signal of the operational amplifier OP42 is also fed back to the inverting input terminal of the operational amplifier OP42 via a capacitor C52 and a switch SW3. In this way, when the selection signal SEL is at a low level, the third filter circuit 370 functions as a band-pass filter similar to the second filter circuit 354 shown in FIG. 10. The group of switches including the switches SW1, SW2, and SW3 is another example of a "switching unit."

[0239] As described above, this modification also provides the same effects as the above-described embodiment. Furthermore, in this modification, the operational amplifier OP42 and the resistor element R42 are shared between the first filter circuit 344A and the second filter circuit 354A. This allows the circuit size of the detection circuit 33A to be reduced compared to the detection circuit 33.

[0240] [Second Modification] In the above-described embodiment, the first buffer circuit 346 may be omitted from the first testing signal generation circuit 340, the second buffer circuit 356 may be omitted from the second testing signal generation circuit 350, and the buffer circuit 372 may be provided subsequent to the second selection circuit 360. Alternatively, the first gain adjustment circuit 342, the first buffer circuit 346, the second gain adjustment circuit 352, and the second buffer circuit 356 may be omitted, and a gain adjustment circuit similar to the first gain adjustment circuit 342 and the buffer circuit 372 may be provided subsequent to the second selection circuit 360. Furthermore, in the above-described modified example, the first gain adjustment circuit 342 and the second gain adjustment circuit 352 may be omitted, and a gain adjustment circuit similar to the first gain adjustment circuit 342 may be provided between the second selection circuit 360 and the buffer circuit 372.

[0241] As described above, this modification can also achieve the same effects as the above-described embodiment and modification. Furthermore, in this modification, the first buffer circuit 346 and the like are omitted, so the circuit size of the detection circuit 33 or 33A can be reduced.

[0242] [Third Modification] In the above-described embodiment and modified examples, the first selection circuit 330 may be omitted. In this modified example, the same effects as those of the above-described embodiment and modified examples can be obtained, except for the effects obtained by the first selection circuit 330.

[0243] [Fourth Modification] In the above-described embodiment and modified examples, the number of times the state of the discharge section D is determined in the first mode during one printing operation may be greater than the number of times the state of the discharge section D is determined in the second mode. This modified example also provides the same effects as the above-described embodiment and modified examples. Note that, in the first mode, the time allocated to detecting residual vibrations of the discharge section D can be shortened, and therefore, even if the number of times the state of the discharge section D is determined in the first mode is large, this does not significantly affect the decrease in printing efficiency.

[0244] [Fifth Modification] In the above-described embodiment and modified example, the first inspection signal Vd1 indicating the pseudo residual vibration signal is generated based on residual vibration of at least one-quarter period and less than one period of the discharge portion D, but the present invention is not limited to such an embodiment. For example, the first inspection signal Vd1 may be generated based on residual vibration of one period of the discharge portion D, and the second inspection signal Vd2 may be generated based on residual vibration longer than one period of the discharge portion D. In this modified example, the same effects as those of the above-described embodiment and modified example can be obtained.

[0245] [Sixth Modification] In the above-described embodiment and modified example, the piezoelectric element PZ is displaced in the Z1 direction as the potential of the individual drive signal Vin[m] changes from low to high, but the present invention is not limited to this example. For example, a piezoelectric element PZ may be used that is displaced in the Z1 direction as the potential of the individual drive signal Vin[m] changes from high to low. In this case, for example, the potential of the drive signal COM changes from low to high in the portion corresponding to the expansion element, and from high to low in the portion corresponding to the contraction element. This modified example can also achieve the same effects as the above-described embodiment and modified example.

[0246] [Seventh Modification] In the above-described embodiment and modified example, each head unit 3 has one nozzle row NL, but the present invention is not limited to this. For example, each head unit 3 may have multiple nozzle rows NL. In this modified example, the same effects as those of the above-described embodiment and modified example can be obtained.

[0247] [Eighth Modification] In the above-described embodiment and modified example, the inkjet printer 1 has four head units 3, but the present invention is not limited to this. For example, the inkjet printer 1 may have one to three head units 3, or five or more head units 3. Alternatively, the inkjet printer 1 may have one to three head units 3A, or five or more head units 3A.

[0248] [Ninth Variation] In the above-described embodiment and modified example, the first filter circuit 344 is a multiple feedback bandpass filter, but the present invention is not limited to this. For example, a filter circuit with variable group delay characteristics, such as a Butterworth type or a Chebyshev type, may be used as the first filter circuit 344. This modified example also provides the same effects as the above-described embodiment and modified example.

[0249] [3. Notes] From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0250] A liquid ejection device according to aspect 1, which is a preferred aspect, comprises a drive signal generation unit that generates a drive signal, an ejection unit including a nozzle, a piezoelectric element driven by the drive signal, and a pressure chamber that ejects liquid from the nozzle in response to the driving of the piezoelectric element, a first signal generation unit that receives as input a residual vibration signal generated by vibration remaining in the ejection unit after the piezoelectric element is driven and generates a pseudo-residual vibration signal in response to the residual vibration signal, a second signal generation unit that receives as input the residual vibration signal and generates a detected residual vibration signal by removing frequency components other than predetermined frequency components from the residual vibration signal, and a determination unit that selectively receives as input one of the pseudo-residual vibration signal and the detected residual vibration signal and determines the state of the ejection unit based on the input signal. According to the first aspect, it is possible to prevent the length of the unit period, which is the cycle for driving the ejection section, from increasing. Furthermore, according to the first aspect, it is possible to appropriately switch between determining the state of the ejection section using the pseudo residual vibration signal and determining the state of the ejection section using the detected residual vibration signal.

[0251] A liquid ejection device according to aspect 2, which is a specific example of aspect 1, further includes a first switching unit that switches whether or not the residual vibration signal is input to a first signal generating unit, and a second switching unit that switches whether or not the residual vibration signal is input to a second signal generating unit. According to the second aspect, it is possible to easily switch between generating the signal for determining the state of the discharge portion by the first signal generating portion and generating it by the second signal generating portion.

[0252] A liquid ejection device according to aspect 3, which is a specific example of aspect 1 or 2, further has a switching unit that exclusively switches between supplying the pseudo residual vibration signal to the judgment unit and supplying the detected residual vibration signal to the judgment unit based on a switching signal. According to the third aspect, it is possible to prevent the pseudo residual vibration signal and the detected residual vibration signal, which are not used for determining the state of the ejection section, from being supplied to the determination section during the period when the determination section is determining the state of the ejection section. Therefore, according to the third aspect, it is possible to prevent the occurrence of determination section noise and the like during the period when the determination section is determining the state of the ejection section.

[0253] In a liquid ejection device according to aspect 4, which is a specific example of any one of aspects 1 to 3, the first signal generating unit includes a low-pass filter and a filter circuit that receives the residual vibration signal through the low-pass filter and generates the pseudo residual vibration signal. According to the fourth aspect, the filter circuit can generate a pseudo residual vibration signal based on the residual vibration signal from which noise, etc. has been removed. As a result, according to the fourth aspect, it is possible to suppress distortion from occurring in the pseudo residual vibration signal.

[0254] In the liquid ejection device according to Aspect 5, which is a specific example of any one of Aspects 1 to 4, the determination unit determines the viscosity state of the liquid in the ejection unit based on the pseudo residual vibration signal. According to the fifth aspect, it is possible to prevent an increase in the time required to determine the viscosity state of the liquid in the ejection portion.

[0255] In a liquid ejection device according to aspect 6, which is a specific example of any one of aspects 1 to 5, the determination unit determines multiple abnormal conditions, including an increased viscosity of the liquid in the ejection unit, based on the detected residual vibration signal. According to the sixth aspect, by using the detected residual vibration signal as a signal for determining the state of the ejection section, it is possible to determine a plurality of abnormal states, including an increased viscosity state of the ink.

[0256] Furthermore, a liquid ejection head according to aspect 7, which is a preferred aspect, comprises an ejection section including a nozzle, a piezoelectric element driven by a drive signal, and a pressure chamber that ejects liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generation section that receives as input a residual vibration signal generated by vibration remaining in the ejection section after the piezoelectric element is driven and generates a pseudo-residual vibration signal in response to the residual vibration signal; a second signal generation section that receives as input the residual vibration signal and generates a detected residual vibration signal by removing frequency components other than predetermined frequency components from the residual vibration signal; and a switching section that switches between supplying the pseudo-residual vibration signal to a judgment section that judges the state of the ejection section or supplying the detected residual vibration signal to the judgment section. According to the seventh aspect, the same effect as that of the first aspect can be obtained.

[0257] A liquid ejection head according to aspect 8, which is a specific example of aspect 7, further includes a first switching unit that switches whether or not the residual vibration signal is input to a first signal generating unit, and a second switching unit that switches whether or not the residual vibration signal is input to a second signal generating unit. According to the eighth aspect, the same effect as that of the second aspect can be obtained.

[0258] In a liquid ejection head according to aspect 9, which is a specific example of aspect 7 or 8, the switching unit exclusively switches between supplying the pseudo residual vibration signal to the judgment unit and supplying the detected residual vibration signal to the judgment unit based on a switching signal. According to the ninth aspect, the same effect as that of the third aspect can be obtained.

[0259] In a liquid ejection head according to aspect 10, which is a specific example of any one of aspects 7 to 9, the first signal generating unit includes a low-pass filter and a filter circuit that receives the residual vibration signal through the low-pass filter and generates the pseudo residual vibration signal. According to the tenth aspect, the same effect as that of the fourth aspect can be obtained.

[0260] In the liquid ejection head according to Aspect 11, which is a specific example of any one of Aspects 7 to 10, the pseudo residual vibration signal is used to determine the viscosity state of the liquid in the ejection section. According to the eleventh aspect, the same effect as that of the fifth aspect can be obtained.

[0261] In a liquid ejection head according to aspect 12, which is a specific example of any one of aspects 7 to 11, the detected residual vibration signal is used to determine multiple abnormal conditions, including an increased viscosity state of the liquid in the ejection section. According to the twelfth aspect, the same effect as that of the sixth aspect can be obtained. [Explanation of symbols]

[0262] 1...inkjet printer, 2...control unit, 3...head unit, 4...drive signal generation unit, 6...inspection unit, 7...transport unit, 8...maintenance unit, 22...drive control unit, 31...switching circuit, 32...recording head, 33...detection circuit, 312...high-pass filter circuit, 330...first selection circuit, 332...reference potential generation circuit, 334...first reference potential generation circuit, 335...first switching circuit, 336...second reference potential generation circuit, 337 ...second switching circuit, 340...first inspection signal generating circuit, 342...first gain adjustment circuit, 343...low-pass filter circuit, 344, 344A...first filter circuit, 346...first buffer circuit, 350...second inspection signal generating circuit, 352...second gain adjustment circuit, 354, 354A...second filter circuit, 356...second buffer circuit, 360...second selection circuit, 370...third filter circuit, 372...buffer circuit, D...ejection section, N...nozzle.

Claims

1. a drive signal generating unit that generates a drive signal; a discharge unit including a nozzle, a piezoelectric element driven by the drive signal, and a pressure chamber that discharges liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generating unit that receives a residual vibration signal generated in association with vibration remaining in the ejection unit after the piezoelectric element is driven, and generates a pseudo residual vibration signal corresponding to the residual vibration signal; a second signal generating unit that receives the residual vibration signal and generates a detected residual vibration signal by removing frequency components other than a predetermined frequency component from the residual vibration signal; a determination unit to which one of the pseudo residual vibration signal and the detected residual vibration signal is selectively input, and which determines the state of the discharge unit based on the input signal; Equipped with A liquid ejection device characterized by:

2. a first switching unit that switches whether or not the residual vibration signal is input to the first signal generating unit; a second switching unit that switches whether or not the residual vibration signal is input to the second signal generating unit; further comprising The liquid ejection device according to claim 1 .

3. a switching unit that exclusively switches between supplying the pseudo residual vibration signal to the determination unit and supplying the detected residual vibration signal to the determination unit based on a switching signal; The liquid ejection device according to claim 1 .

4. The first signal generation unit A low-pass filter and a filter circuit to which the residual vibration signal is input via the low-pass filter and which generates the pseudo residual vibration signal; Including, 4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

5. The determination unit determining a viscosity state of the liquid in the ejection portion based on the pseudo residual vibration signal; 4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

6. The determination unit determining a plurality of abnormal states including an increased viscosity state of the liquid in the ejection portion based on the detected residual vibration signal; 4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

7. a discharge unit including a nozzle, a piezoelectric element driven by a drive signal, and a pressure chamber that discharges liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generating unit that receives a residual vibration signal generated in association with vibration remaining in the ejection unit after the piezoelectric element is driven, and generates a pseudo residual vibration signal corresponding to the residual vibration signal; a second signal generating unit that receives the residual vibration signal and generates a detected residual vibration signal by removing frequency components other than a predetermined frequency component from the residual vibration signal; a switching unit that switches between supplying the pseudo residual vibration signal to a determination unit that determines the state of the ejection unit and supplying the detected residual vibration signal to the determination unit; Equipped with A liquid ejection head characterized by:

8. a first switching unit that switches whether or not the residual vibration signal is input to the first signal generating unit; a second switching unit that switches whether or not the residual vibration signal is input to the second signal generating unit; further comprising 8. The liquid ejection head according to claim 7.

9. The switching unit is switching exclusively between supplying the pseudo residual vibration signal to the determination unit and supplying the detected residual vibration signal to the determination unit based on a switching signal; 8. The liquid ejection head according to claim 7.

10. The first signal generation unit A low-pass filter and a filter circuit to which the residual vibration signal is input via the low-pass filter and which generates the pseudo residual vibration signal; Including, 10. The liquid ejection head according to claim 7, wherein the liquid ejection head is a liquid ejection head.

11. The pseudo residual vibration signal is used to determine the viscosity of the liquid in the ejection portion.

10. The liquid ejection head according to claim 7, wherein the liquid ejection head is a liquid ejection head.

12. the detected residual vibration signal is used to determine a plurality of abnormal states including an increased viscosity state of the liquid in the ejection portion; 10. The liquid ejection head according to claim 7, wherein the liquid ejection head is a liquid ejection head.

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