Liquid discharge apparatus and liquid discharge head

Abstract

The invention provides a liquid ejecting apparatus and a liquid ejecting head, which can inhibit the length of a unit period, which is a period for driving an ejecting portion, from increasing when the state of the ejecting portion is determined. An inkjet printer includes: a drive signal generation unit that generates a drive signal; an ejection section including a nozzle, a piezoelectric element driven by the driving signal, and a chamber ejecting ink from the nozzle in response to driving of the piezoelectric element; a first inspection signal generation circuit to which a residual vibration signal generated in accordance with vibration remaining in the ejection unit after the piezoelectric element is driven is input, and which generates a pseudo residual vibration signal corresponding to the residual vibration signal; a second test signal generation circuit to which the residual vibration signal is input and which generates a detection residual vibration signal in which a frequency component other than the predetermined frequency component is removed from the residual vibration signal; and an inspection unit to which one of the pseudo residual vibration signal and the detection residual vibration signal is selectively input, and which determines the state of the ejection unit on the basis of the input signal.

Description

Technical Field

[0001] The present invention relates to a liquid ejecting device and a liquid ejecting head. Background Art

[0002] Liquid ejection devices such as inkjet printers form an image on a medium by driving an ejection portion of a liquid ejection head during each of a plurality of unit periods specified by a latch signal, thereby ejecting a liquid such as ink filled in the ejection portion. However, in such liquid ejection devices, ejection abnormalities may sometimes occur in which the liquid cannot be ejected normally from the ejection portion. For this reason, a technology for checking the ejection state in the ejection portion has been proposed. For example, Patent Document 1 discloses a technology for checking the ejection state in the ejection portion based on a detection signal, which indicates the vibration remaining in the ejection portion after the ejection portion is driven by a drive signal.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-044771

[0004] However, according to the prior art, when checking the ejection state in the ejection portion, both driving the ejection portion by a drive signal and detecting the residual vibration in the driven ejection portion are performed within a unit period which is a cycle of driving the ejection portion. Therefore, it is necessary to set the unit period to a sufficiently long time length. Summary of the Invention

[0005] In order to solve the above technical problems, the liquid ejection device disclosed by the present invention comprises: a drive signal generating unit that generates a drive signal; a ejection unit that includes 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 generating unit to which a residual vibration signal is input, the first signal generating unit generating a pseudo residual vibration signal corresponding to the residual vibration signal, the residual vibration signal being generated by the vibration remaining in the ejection unit after driving the piezoelectric element; a second signal generating unit to which the residual vibration signal is input, the second signal generating unit generating a detection residual vibration signal, the detection residual vibration signal being a signal obtained by removing frequency components other than a specified frequency component from the residual vibration signal; and a determination unit to which one of the pseudo residual vibration signal and the detection residual vibration signal is selectively input, and the determination unit determines the state of the ejection unit based on the input signal.

[0006] In addition, the liquid ejection head according to the present invention comprises: an ejection part, including a nozzle, a piezoelectric element driven by the driving signal, and a pressure chamber for ejecting liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generating part, to which a residual vibration signal is input, and the first signal generating part generates a pseudo residual vibration signal corresponding to the residual vibration signal, and the residual vibration signal is generated by the vibration remaining in the ejection part after driving the piezoelectric element; a second signal generating part, to which the residual vibration signal is input, and the second signal generating part generates a detection residual vibration signal, and the detection residual vibration signal is a signal obtained by removing frequency components other than a specified frequency component from the residual vibration signal; and a switching part, which switches whether to supply the pseudo residual vibration signal to a determination part for determining the state of the ejection part, or to supply the detection residual vibration signal to the determination part. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a block diagram showing an example of the configuration of an inkjet printer according to an embodiment of the present invention.

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

[0009] Figure 3 It is a cross-sectional view for explaining an example of the structure of the ejection portion.

[0010] Figure 4 This is an explanatory diagram for explaining the ink ejection operation in the ejection section.

[0011] Figure 5 This is a plan view showing an example of the arrangement of nozzles in the head unit.

[0012] Figure 6 This is a block diagram showing an example of the configuration of a head unit.

[0013] Figure 7 This is a block diagram showing an example of the configuration of a detection circuit.

[0014] Figure 8 This is a circuit diagram showing an example of the configuration of the first selection circuit.

[0015] Figure 9 : is a circuit diagram showing an example of the configuration of the first inspection signal generating circuit.

[0016] Figure 10 2 is a circuit diagram showing an example of the configuration of the second inspection signal generating circuit.

[0017] Figure 11 It is an explanatory diagram for explaining the characteristics of the first filter circuit.

[0018] Figure 12 : is a graph showing the simulation results of the first filter circuit.

[0019] Figure 13 This 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.

[0020] Figure 14 It is an explanatory diagram for explaining the effects of the first switching circuit and the low-pass filter circuit.

[0021] Figure 15 This is a timing chart showing an example of the operation of the inkjet printer in a unit period.

[0022] Figure 16 This is an explanatory diagram for explaining an example of a first inspection signal generated by the first inspection signal generating circuit.

[0023] Figure 17 This is an explanatory diagram for explaining an example of the second inspection signal generated by the second inspection signal generating circuit.

[0024] Figure 18 This is a block diagram showing an example of the configuration of a detection circuit according to the first modification.

[0025] Figure 19 This is a circuit diagram showing an example of the configuration of a third filter circuit according to the first modification.

[0026] Description of Reference Numerals

[0027] 1: Inkjet printer, 2: Control unit, 3: Head unit, 4: Drive signal generating 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 generating circuit, 334: First reference potential generating circuit, 335: First switching circuit, 336: Second reference potential generating 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: Ejector part, N: Nozzle. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention with reference to the accompanying drawings. However, in the drawings, the dimensions and scales of the various components may differ from the actual dimensions as appropriate. Furthermore, the embodiments described below are intended to be specific examples of the present invention, and thus include various technically preferred limitations. However, unless otherwise specified in the following description, the scope of the present invention is not limited to these embodiments.

[0029] 1. Implementation Method

[0030] In this embodiment, an inkjet printer that ejects ink onto a recording paper to form an image is used as an example to describe the liquid ejecting device. It should be noted that in this embodiment, ink is an example of "liquid". First, refer to Figure 1 The configuration of the inkjet printer 1 according to the embodiment will be described.

[0031] Figure 1 This is a block diagram showing an example of the configuration of the inkjet printer 1 according to the embodiment of the present invention.

[0032] For example, a host computer such as a personal computer or a digital camera supplies print data IMG representing an image to be formed by the inkjet printer 1 to the inkjet printer 1. The inkjet printer 1 performs a printing process to form the image represented by the print data IMG supplied from the host computer on a medium. In this embodiment, the medium is assumed to be Figure 2 The recording paper P is shown.

[0033] The inkjet printer 1 includes a control unit 2 for controlling the various components of the inkjet printer 1 ; a head unit 3 equipped with an ejection unit D for ejecting ink; and a drive signal generating unit 4 for generating a drive signal COM for driving the ejection unit D. The inkjet printer 1 also includes a storage unit 5 that stores various information, such as print data IMG and a control program PG for the inkjet printer 1 ; and a check unit 6 that determines the status of the ejection unit D. Furthermore, the inkjet printer 1 includes a transport unit 7 for changing the relative position of the recording paper P with respect to the head unit 3 ; and a maintenance unit 8 for performing maintenance on the ejection unit D provided in the head unit 3 . It should be noted that the head unit 3 is an example of a "liquid ejection head," the drive signal generating unit 4 is an example of a "drive signal generating unit," and the check unit 6 is an example of a "determination unit."

[0034] Here, in this embodiment, it is assumed that the head unit 3 and the drive signal generating unit 4 correspond to each other, and the head unit 3 and the inspection unit 6 correspond to each other. For example, the inkjet printer 1 may include multiple head units 3, multiple drive signal generating units 4 corresponding one-to-one with the multiple head units 3, and multiple inspection units 6 corresponding one-to-one with the multiple head units 3. Alternatively, the inkjet printer 1 may include one head unit 3, one drive signal generating unit 4 corresponding to each head unit 3, and one inspection unit 6 corresponding to each head unit 3. In this embodiment, it is assumed that the inkjet printer 1 includes four head units 3, four drive signal generating units 4 corresponding one-to-one with each head unit 3, and four inspection units 6 corresponding one-to-one with each head unit 3. However, for the sake of convenience, the following description focuses on one head unit 3 among the four head units 3, one drive signal generating unit 4 provided corresponding to each head unit 3 among the four drive signal generating units 4, and one inspection unit 6 provided corresponding to each head unit 3 among the four inspection units 6.

[0035] The control unit 2 is composed of one or more CPUs (Central Processing Units). Note that the control unit 2 can also include a programmable logic device such as an FPGA (Field-Programmable Gate Array) in place of or in addition to the CPU. Furthermore, the control unit 2 functions as the drive control unit 22 by executing a control program PG stored in the storage unit 5.

[0036] The drive control unit 22 generates signals such as the print signal SI and the waveform designation signal dCOM for controlling the operation of various components of the inkjet printer 1. The waveform designation signal dCOM is a digital signal that specifies the waveform of the drive signal COM. The drive signal COM is an analog signal for driving the ejection unit D. Furthermore, the print signal SI is a digital signal that specifies the type of operation of the ejection unit D. Specifically, the print signal SI specifies the type of operation of the ejection unit D by specifying whether or not the drive signal COM is supplied to the ejection unit D.

[0037] When executing a print process, for example, the drive control unit 22 controls the head unit 3 and the transport unit 7 to print an image represented by the print data IMG on the recording paper P. Specifically, when executing a print process, the drive control unit 22 generates signals such as the print signal SI based on the print data IMG for controlling the head unit 3. Furthermore, when executing a print process, the drive control unit 22 generates signals such as the waveform designation signal dCOM for controlling the drive signal generation unit 4. Furthermore, when executing a print process, the drive control unit 22 generates signals for controlling the transport unit 7. Thus, during the print 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 and adjusts whether ink is ejected from the ejection unit D[m], the amount of ink ejected, and the timing of ink ejection. In this way, the drive control unit 22 controls various components of the inkjet printer 1 to form an image corresponding to the print data IMG on the recording paper P.

[0038] The drive signal generating unit 4 includes, for example, a DAC (Digital Analog Converter) and generates a drive signal COM based on the waveform designation signal dCOM supplied from the drive control unit 22. For example, the drive signal generating unit 4 generates the drive signal COM having a waveform specified by the waveform designation signal dCOM. The drive signal generating 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.

[0039] Storage unit 5 includes one or both of volatile memory such as RAM (Random Access Memory) and nonvolatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable Read-Only Memory). Note that storage unit 5 may also be included in control unit 2.

[0040] The head unit 3 includes a switching circuit 31 , a recording head 32 , and a detection circuit 33 .

[0041] The recording head 32 has M ejection units D. Note that the value M is a natural number greater than or equal to 1. Hereinafter, the mth ejection unit D among the M ejection units D provided in the recording head 32 may be referred to as ejection unit D[m]. Here, the variable m is a natural number satisfying "1 ≤ m ≤ M." Furthermore, when a component or signal of the inkjet printer 1 corresponds to an ejection unit D[m] among the M ejection units D, the reference numerals representing such component or signal may be suffixed with [m].

[0042] The switching circuit 31 switches whether to supply the driving signal COM to the ejection unit D[m] based on the printing signal SI. Figure 6 As shown in FIG, etc., the drive signal COM supplied to the discharge portion 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 a “drive signal”.

[0043] In addition, the switching circuit 31 switches whether to electrically connect the ejection unit D[m] to the detection circuit 33 based on the printing signal SI. When the ejection unit D[m] is electrically connected to the detection circuit 33, for example, the detection signal Vout[m] detected from the ejection unit 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 representing a change in the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the ejection unit D[m]. For example, the detection signal Vout[m] is a residual vibration signal generated by the vibration remaining in the ejection unit D[m] after the piezoelectric element PZ[m] is driven by the separate drive signal Vin[m]. In this case, the waveform of the detection signal Vout[m] represents, for example, the waveform of the vibration remaining in the ejection unit D[m] after the piezoelectric element PZ[m] is driven. The residual vibration of the ejection part 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. It should be noted that the piezoelectric element PZ, the upper electrode Zu[m] and the vibration plate 321 will be described later. Figure 3 Narrating in.

[0044] The detection circuit 33 generates a check signal VD[m] corresponding to the detection signal Vout[m] as a signal for determining the state of the ejection portion D[m]. For example, the detection circuit 33 generates the check signal VD[m] in a manner that simulates the decay wave of the detection signal Vout[m] indicating the residual vibration of the ejection portion D[m]. Details will be discussed later. Figure 7Alternatively, the detection circuit 33 generates a test signal VD[m] by removing frequency components other than the specified frequency component from the residual vibration signal. The detection circuit 33 then outputs the test signal VD[m] corresponding to the detection signal Vout[m] to the inspection unit 6.

[0045] For example, the inspection unit 6 determines the state of the ejection unit D[m] based on the inspection signal VD[m]. For example, the inspection unit 6 determines the viscosity of the ink within the ejection unit D[m]. In this case, it is possible to prevent printing from occurring in an abnormal state caused by the viscosity of the ink within the ejection unit D[m]. Hereinafter, the process of determining the state of the ejection unit D[m] is also referred to as the ejection state determination process. Furthermore, the ejection unit D whose state is being determined is also referred to as the ejection unit D to be determined.

[0046] When the ejection state determination process is executed, the drive control unit 22 generates signals such as the print signal 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 the waveform designation signal dCOM for controlling the drive signal generation unit 4. Consequently, the drive control unit 22 drives the ejection unit D[m] as the ejection unit D to be determined.

[0047] Furthermore, when executing the ejection state determination process, the drive control unit 22 controls the head unit 3 by generating a print signal SI to supply a detection signal Vout[m] corresponding to the ejection unit D[m] being driven as the ejection unit D to be determined to the detection circuit 33. Consequently, the detection circuit 33 generates a check signal VD[m] corresponding to the detection signal Vout[m] detected from the ejection unit D[m] being driven as the ejection unit D to be determined. The inspection unit 6 then determines the state of the ejection unit D[m] being driven as the ejection unit D to be determined based on the check signal VD[m] supplied from the detection circuit 33. Furthermore, the inspection unit 6 outputs state information Cinf to the control unit 2, which includes information indicating the determination result of the state of the ejection unit D[m].

[0048] Note that 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 according to the control program PG stored in the storage unit 5 .

[0049] In addition, as described above, in this embodiment, the inkjet printer 1 performs maintenance processing. For example, the maintenance processing includes flushing processing to discharge ink from the ejection part D, wiping processing to remove foreign matter such as ink adhering to the nozzle N of the ejection part D by a wiper, and pumping processing to suck the ink in the ejection part D by a tube pump or the like. Figure 3Narrating in.

[0050] For example, the flushing process discharges thickened and heavy ink with increased viscosity from the discharge portion D. This allows the viscosity of the ink in the nozzle N to be below a predetermined viscosity at the start of the printing process. In this case, since the thickened ink is discharged from the discharge portion D, degradation in the quality of the image printed by the printing process can be suppressed.

[0051] The maintenance unit 8 includes: a discharged ink receiving portion 80 for receiving the discharged ink when the ink in the ejection portion D is discharged during the flushing process; a wiper for wiping off foreign matter such as ink adhering to the vicinity of the nozzle N of the ejection portion D; and a tube pump for sucking out ink, bubbles, etc. in the ejection portion D. It should be noted that the discharged ink receiving portion 80 will be described later. Figure 2 In addition, the wiper and the tube pump are omitted from the illustration. Figure 2 The schematic internal structure of the inkjet printer 1 will be described.

[0052] Figure 2 This is a perspective view showing an example of a schematic internal structure of the inkjet printer 1 .

[0053] like Figure 2 As shown, in this embodiment, the inkjet printer 1 is assumed to be a serial printer. Specifically, when executing a print process, the inkjet printer 1 transports the recording paper P in the sub-scanning direction while reciprocating the head unit 3 in the main scanning direction intersecting the sub-scanning direction, ejecting ink from the ejection portion D[m], thereby forming dots corresponding to the print data IMG on the recording paper P.

[0054] For the sake of convenience, a three-axis orthogonal coordinate system with mutually orthogonal X-axis, Y-axis, and Z-axis is introduced below. For example, in this embodiment, the Y1 direction along the Y-axis is set as the secondary scanning direction, and the X1 direction and X2 direction along the X-axis are set as the main scanning direction. It should be noted that the X2 direction is the opposite direction to the X1 direction. In addition, in this embodiment, Figure 2 In the example shown, the Z1 direction along the Z axis is used as the ejection direction of ink from the ejection portion D[m]. Hereinafter, the X1 and X2 directions are collectively referred to as the X-axis direction, the Y1 direction and the Y2 direction opposite to the Y1 direction are collectively referred to as the Y-axis direction, and the Z1 direction and the Z2 direction opposite to the Z1 direction are collectively referred to as the Z-axis direction. It should be noted that although the X-axis, Y-axis, and Z-axis are assumed to be orthogonal to each other in this embodiment, the present invention is not limited to this configuration. For example, the X-axis, Y-axis, and Z-axis may intersect with each other.

[0055] The inkjet printer 1 according to this embodiment includes a housing 100 and a carriage 110 . The carriage 110 is reciprocatingly movable in the X-axis direction within the housing 100 and carries four head units 3 .

[0056] In this embodiment, the carriage 110 is assumed to contain four ink cartridges 120 corresponding to the four colors of ink: cyan, magenta, yellow, and black. Furthermore, in this embodiment, as described above, the inkjet printer 1 is assumed to have four head units 3 corresponding to the four ink cartridges 120. Each ejection portion D[m] receives a supply of ink from the ink cartridge 120 corresponding to the head unit 3 in which the ejection portion D[m] is located. Consequently, each ejection portion D[m] is internally filled with the supplied ink and ejects the filled ink from the nozzles N. Note that the ink cartridges 120 may also be located external to the carriage 110.

[0057] In addition, as in Figure 1 As described in [ 15 ], the inkjet printer 1 according to this embodiment includes a transport unit 7. The transport unit 7 includes a carriage transport mechanism 71 and a carriage guide shaft 76. The carriage transport mechanism 71 reciprocates the carriage 110 in the X-axis direction, while the carriage guide shaft 76 supports the carriage 110 for reciprocal movement in the X-axis direction. Furthermore, the transport unit 7 includes a medium transport mechanism 73 for transporting the recording paper P and a platen 75 positioned in the Z1 direction relative to the carriage 110. For example, during printing, the carriage transport mechanism 71 reciprocates the head unit 3 and the carriage 110 along the carriage guide shaft 76 in the X-axis direction, while the medium transport mechanism 73 transports the recording paper P on the platen 75 in the Y1 direction. Therefore, the transport unit 7 changes the relative position of the recording paper P with respect to the head unit 3 by operating the carriage transport mechanism 71 and the medium transport mechanism 73 during printing, enabling ink to be deposited on the entire recording paper P.

[0058] Next, refer to Figure 3 The schematic structure of the recording head 32 will be described.

[0059] Figure 3 This is a cross-sectional view for explaining an example of the structure of the ejection portion D. Figure 3 , a partial cross section of the recording head 32 when the recording head 32 is cut so as to include the ejection portion D[m] is schematically shown.

[0060] The ejection unit D[m] includes 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 within the cavity CV when supplied with a separate drive signal Vin[m], and a vibration plate 321. In the ejection unit D[m], the piezoelectric element PZ[m] is driven by the separate drive signal Vin[m], causing the ink within the cavity CV to be ejected from the nozzle N.

[0061] The chamber CV corresponds to a pressure chamber connected to the nozzle N. For example, the chamber CV is a space defined by the chamber plate 324, the nozzle plate 323 on which the nozzle N is formed, and the vibration plate 321. The chamber CV is connected to the reservoir 325 via the ink supply port 326. The reservoir 325 is connected to the ink cartridge 120 corresponding to the ejection portion D[m] via the ink inlet 327. The piezoelectric element PZ[m] includes an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric body Zb[m] disposed between the upper electrode Zu[m] and the lower electrode Zd[m]. The piezoelectric body Zb[m] is formed, for example, of a ferroelectric piezoelectric material.

[0062] The upper electrode Zu[m] is electrically connected to a wiring Li to which a separate drive signal Vin[m] is supplied. The lower electrode Zd[m] is electrically connected to a wiring Ld to which a base potential signal VBS is supplied. Thus, by supplying the separate drive signal Vin[m] 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] displaces 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].

[0063] 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 bonded to the vibration plate 321. Therefore, the piezoelectric element PZ[m] is driven and vibrated by the individual drive signal Vin[m], thereby vibrating the vibration plate 321. The vibration of the vibration plate 321 then changes the volume of the cavity CV and the pressure within the cavity CV, causing the ink filling the cavity CV to be ejected from the nozzle N.

[0064] In this embodiment, as an example, a case is assumed where the piezoelectric element PZ is displaced in the Z1 direction by changing the potential of the individual drive signal Vin[m] supplied to the ejection unit D[m] from a low potential to a high potential. Specifically, in this embodiment, a case is assumed where the volume of the cavity CV included in the ejection unit D[m] decreases when the potential of the individual drive signal Vin[m] supplied to the ejection unit D[m] is high compared to when the potential is low.

[0065] Next, refer to Figure 4 The ink ejection operation in the ejection section D will be described.

[0066] Figure 4 It is an explanatory diagram for explaining the ink ejection operation in the ejection section D.

[0067] For example, in the state of phase-1, 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 such that the piezoelectric element PZ is displaced in the Z2 direction. As a result, the vibration plate 321 of the ejection unit D is bent in the Z2 direction. As a result, Figure 4 As shown in the state of stage-2, the volume of the cavity CV of the ejection part D is expanded compared to the state of stage-1. Then, for example, in the state of stage-2, the drive control unit 22 changes the potential of the drive signal COM, thereby generating distortion such that the piezoelectric element PZ is displaced in the Z1 direction. As a result, the vibration plate 321 of the ejection part D is bent in the Z1 direction. As a result, Figure 4 As in the state of stage-3 shown, the volume of the cavity CV shrinks rapidly, and a portion of the ink filling the cavity CV is ejected as ink droplets from the nozzle N communicating with the cavity CV.

[0068] In this manner, by driving the piezoelectric element PZ of the ejection portion D using the drive signal COM, the piezoelectric element PZ of the ejection portion D and the vibration plate 321 are displaced in the Z-axis direction. Consequently, residual vibration is generated in the ejection portion D including the vibration plate 321 after the piezoelectric element PZ is driven using the drive signal COM.

[0069] Next, refer to Figure 5 An example of arrangement of the nozzles N will be described.

[0070] Figure 5 3 is a top view showing an example of the arrangement of the nozzles N in the head unit 3. Figure 5 , an example of the arrangement of four head units 3 mounted on the carriage 110 and a total of 4M nozzles N provided in the four head units 3 when the inkjet printer 1 is viewed from the Z1 direction in a plan view is shown.

[0071] Each head unit 3 provided on the carriage 110 is provided with a nozzle row NL. Here, the nozzle row NL is a plurality of nozzles N arranged to extend in a row in a predetermined direction. In this embodiment, as an example, it is assumed that each nozzle row NL is composed of M nozzles N arranged to extend in the Y-axis direction.

[0072] Next, refer to Figure 6 The outline of the head unit 3 will be described.

[0073] Figure 6 It is a block diagram showing an example of the configuration of the head unit 3 .

[0074] As in Figure 1 As described in [ 1 ], the head unit 3 includes a switching circuit 31, a recording head 32, and a detection circuit 33. Furthermore, the head unit 3 includes a wiring La, which receives a drive signal COM from the drive signal generating unit 4; a wiring Ls1, which supplies a potential signal Vzu to a high-pass filter circuit 312 described below; and a wiring Ls2, which supplies a detection signal Vout to the detection circuit 33. Furthermore, the head unit 3 includes wiring Li[m] and wiring Ld. Wiring Li[m] supplies an individual drive signal Vin[m] to the ejection unit D[m], while wiring Ld receives a base potential signal VBS.

[0075] The switching circuit 31 includes M switches SWa[1] to SWa[M] corresponding one-to-one to the M ejection units D[1] to D[M], M switches SWs[1] to SWs[M] corresponding one-to-one to the M ejection units D[1] to D[M], and a connection state designation circuit 310. Furthermore, the switching circuit 31 includes a high-pass filter circuit 312 that outputs a detection signal Vout[m] to the detection circuit 33. This detection signal Vout[m] is a signal obtained by removing the DC component from a potential signal Vzu[m] indicating the potential of the upper electrode Zu[m] provided on the piezoelectric element PZ[m]. It should be noted that the potential signal Vzu[m], which is the basis for the detection signal Vout[m], can also be understood as a "residual vibration signal."

[0076] The high-pass filter circuit 312 includes, for example, a capacitor C10, one end of which is electrically connected to the wiring Ls1 and the other end of which is electrically connected to the wiring Ls2. Furthermore, the switching circuit 31 includes a resistor R10, one end of which is electrically connected to the wiring La and the other end of which is electrically connected to the wiring Ls1. The resistor R10 functions as a bias resistor for supplying the voltage of the drive signal COM to the wiring Ls1. Hereinafter, the node connected to one end of the resistor R10 may be referred to as node N1, and the node connected to the other end of the resistor R10 may be referred to as node N2. For example, the resistor R10 and the capacitor C10 are connected to the node N2. Furthermore, for example, the detection circuit 33 is connected to the node N2 via the capacitor C10. Hereinafter, the node connected to the capacitor C10 and the detection circuit 33 may be referred to as node N3.

[0077] The connection state designation circuit 310 designates the connection state of each 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 a portion of the print signal SI, latch signal LAT, and period specification signal Tsig supplied from the drive control unit 22. The connection state designation signal Qa[m] is a signal that designates whether the switch SWa[m] is on or off, and the connection state designation signal Qs[m] is a signal that designates whether the switch SWs[m] is on or off. Furthermore, the connection state designation circuit 310 generates a selection signal SEL and a detection period signal Acut based on at least a portion of the print signal SI, latch signal LAT, and period specification signal Tsig. The selection signal SEL and the detection period signal Acut are supplied to the detection circuit 33.

[0078] In this embodiment, the M switches SWa and the M switches SWs are each configured as a transmission gate including a P-channel transistor and an N-channel transistor connected in parallel. However, the M switches SWa and the M switches SWs may each be configured as either a P-channel transistor or an N-channel transistor.

[0079] Based on the connection state designation signal Qa[m], the switch SWa[m] switches between the conductive and non-conductive state of the wiring La and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the ejection unit D[m]. That is, based on the connection state designation signal Qa[m], the switch SWa[m] switches between the conductive and non-conductive state of the wiring La and the wiring Li[m] connected to the upper electrode Zu[m]. In this embodiment, the switch SWa[m] is turned on when the connection state designation signal Qa[m] is at a high level, and is turned off when the connection state designation signal Qa[m] is at a low level. When the switch SWa[m] is turned on, the drive signal COM supplied to the wiring La is supplied to the upper electrode Zu[m] of the ejection unit D[m] via the wiring Li[m] as the 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 ejection unit D[m] via the switch SWa[m].

[0080] Switch SWs[m] switches between conducting and non-conducting between wiring Ls1 and the upper electrode Zu[m] of piezoelectric element PZ[m] provided in ejection section D[m] based on connection state designation signal Qs[m]. Specifically, switch SWs[m] switches between conducting and non-conducting between wiring Ls1 and wiring Li[m] connected to upper electrode Zu[m] based on connection state designation signal Qs[m]. In this embodiment, switch SWs[m] is turned on when connection state designation signal Qs[m] is at a high level and is turned off when connection state designation signal Qs[m] is at a low level.

[0081] For example, the connection state designation signal Qs[m] becomes high when detecting the residual vibration of the ejection unit D[m]. Thus, the residual vibration of the ejection unit D to be determined is detected. When the switch SWs[m] is turned on, the potential signal Vzu[m] representing the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] of the ejection unit D[m] to be determined 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 the detection circuit 33 with a detection signal Vout[m] from which the DC component of the potential signal Vzu[m] has been removed, via the wiring Ls2. The detection circuit 33 generates a check signal VD[m] corresponding to the detection signal Vout[m].

[0082] However, although a large-amplitude driving signal COM is required to drive the piezoelectric element PZ, the detection circuit 33 does not require a large dynamic range because it is an analog signal processing circuit. For this reason, in this embodiment, the high power supply potential of the detection circuit 33 is smaller than the maximum potential of the driving signal COM. For example, the maximum potential of the driving signal COM is about 42V, the high power supply potential of the detection circuit 33 is about 3.3V, and the low power supply potential of the detection circuit 33 is about 0V. In this way, since the high power supply potential of the detection circuit 33 is lower than the maximum potential of the driving signal COM, the coupling between the piezoelectric element PZ and the detection circuit 33 is not suitable for DC coupling. In this embodiment, the DC component of the potential signal Vzu is removed by the high-pass filter circuit 312, so that the detection circuit 33 can operate normally.

[0083] Next, refer to Figure 7 The outline of the detection circuit 33 will be described.

[0084] Figure 7 3 is a block diagram showing an example of the configuration of the detection circuit 33 .

[0085] 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 .

[0086] The first selection circuit 330 selects the detection signal Vout and the detection period signal Acut based on the selection signal SEL and the detection period signal Acut. Figure 8 That is, the first selection circuit 330 supplies one of the detection signal Vout and the first reference potential Vref1 as the first input signal Vs1 to the first inspection signal generation circuit 340 based on the selection signal SEL and the detection period signal Acut.

[0087] In addition, the first selection circuit 330 selects the detection signal Vout and the detection period signal Acut based on the selection signal SEL and the detection period signal Acut. Figure 8 That is, the first selection circuit 330 supplies one of the detection signal Vout and the second reference potential Vref2 as the second input signal Vs2 to the second inspection signal generation circuit 350 based on the selection signal SEL and the detection period signal Acut.

[0088] For example, the first inspection signal generating circuit 340 generates a first inspection signal Vd1 that simulates the attenuation wave of the detection signal Vout. Thus, the first inspection signal Vd1 is generated as a pseudo residual vibration signal that simulates the residual vibration of the ejection portion D. It should be noted that in this embodiment, it is assumed that the first inspection signal Vd1 is generated based on the residual vibration of the ejection portion D that is 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 greater than a quarter cycle and less than one cycle, and outputs the generated pseudo residual vibration signal as the first inspection signal Vd1. It should be noted that, as described below Figure 16 As shown, the period of the first inspection signal Vd1 output from the first inspection signal generating circuit 340 is longer than one period.

[0089] The first inspection signal generating circuit 340 has, 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 the high-frequency component of the first input signal Vs1. The high-frequency component is, for example, a frequency component higher than the frequency band of the residual vibration. The first filter circuit 344 is a multiple feedback type bandpass filter. The first buffer circuit 346 converts the impedance and outputs a low-impedance first inspection signal Vd1. The first inspection signal generating circuit 340 is an example of a "first signal generating 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". It should be noted that the details of the first inspection signal generating circuit 340 will be described later. Figure 9 Narrating in.

[0090] The second inspection signal generating circuit 350, for example, generates a second inspection signal Vd2 after removing frequency components other than a specified frequency component from the detection signal Vout. Thus, the second inspection signal Vd2 is generated as a detection residual vibration signal corresponding to a signal of a specified frequency component in the detection signal Vout representing the residual vibration of the ejection portion D. The specified frequency component is, for example, a frequency component corresponding to the frequency band of the residual vibration. It should be noted that in this embodiment, it is envisaged that the second inspection signal Vd2 is generated based on residual vibrations of more than one cycle of the ejection portion D. For example, the second inspection signal generating circuit 350 generates a detection residual vibration signal based on a detection signal Vout of more than one cycle, and outputs the generated detection residual vibration signal as the second inspection signal Vd2. The second inspection signal generating circuit 350 is an example of a "second signal generating unit".

[0091] The second inspection signal generating circuit 350 includes, for example, a second gain adjustment circuit 352 having the same configuration as the first gain adjustment circuit 342, a second filter circuit 354, and a second buffer circuit 356 having the same configuration as the first buffer circuit 346. The second filter circuit 354 is a bandpass filter that passes a signal having a predetermined frequency component. The details of the second inspection signal generating circuit 350 will be discussed later. Figure 10 Narrating in.

[0092] 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. It should be noted that the second selection circuit 360 can also, for example, exclusively switch between supplying the first inspection signal Vd1 or supplying the second inspection signal Vd2 to the inspection unit 6 based on the selection signal SEL. In this embodiment, the second selection circuit 360 supplies the first inspection signal Vd1 as the inspection signal VD to the inspection unit 6 when the selection signal SEL is at a high level, and supplies the second inspection signal Vd2 as the inspection signal VD to the inspection unit 6 when the selection signal SEL is at a low level. It should be noted that the second selection circuit 360 is an example of a "switching unit."

[0093] Thus, in this embodiment, the selection signal SEL can be used to switch whether the inspection unit 6 determines the state of the ejection portion D based on the first inspection signal Vd1 or the second inspection signal Vd2. It should be noted that the case where the inspection unit 6 determines the state of the ejection portion D based on the first inspection signal Vd1 and the case where the inspection unit 6 determines the state of the ejection portion D based on the second inspection signal Vd2 can each be understood as a mode for determining the state of the ejection portion D. Hereinafter, the case where the inspection unit 6 determines the state of the ejection portion D based on the first inspection signal Vd1 will sometimes be referred to as the first mode, and the case where the inspection unit 6 determines the state of the ejection portion D based on the second inspection signal Vd2 will sometimes be referred to as the second mode. In this case, the operation of the inspection unit 6 is also described as follows. For example, the inspection unit 6 determines the state of the ejection portion D using a mode selected from a plurality of modes, including the first mode and the second mode, based on the selection signal SEL.

[0094] In this embodiment, as described above, the first inspection signal Vd1 is generated based on the residual vibration of the discharge portion D having a period of less than one, and the second inspection signal Vd2 is generated based on the residual vibration of the discharge portion D having a period of more than one. Therefore, when the state of the discharge portion D is determined based on the first inspection signal Vd1, the time allocated to detecting the residual vibration of the discharge portion D can be shortened compared to when the state of the discharge portion D is determined based on the second inspection signal Vd2. Consequently, in this embodiment, the time required to determine the states of multiple discharge portions D can be suppressed.

[0095] Next, refer to Figure 8 The outline of the first selection circuit 330 will be described.

[0096] Figure 8 : is a circuit diagram showing an example of the configuration of the first selection circuit 330 .

[0097] The first selection circuit 330 includes a reference potential generating circuit 332, a first reference potential generating circuit 334, a second reference potential generating circuit 336, a first switching circuit 335, a second switching circuit 337, an inverter INV1, and NOR circuits NOR1 and NOR2. It should be noted that 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."

[0098] The reference potential generating circuit 332 has resistor elements R30 and R31 connected in series between a wiring supplied with a potential VPH and a wiring supplied with a potential VPL. The potential VPH is a high power supply potential of the detection circuit 33, and the potential VPL is a low power supply potential of the detection circuit 33. One end of the resistor element R30 is connected to the wiring supplied with the potential VPH, and the other end of the resistor element R30 is connected to the wiring Ls2 supplied with the detection signal Vout. In addition, one end of the resistor element R31 is connected to the wiring Ls2, and the other end of the resistor element R31 is connected to the wiring supplied with the potential VPL. That is, the detection signal Vout is supplied to the node N3 electrically connected to the resistor element R30 and the resistor element R31. The resistance values ​​of the resistor elements R30 and R31 are set, for example, so that Figure 6 When the potential of the node N2 shown in FIG. 1 is maintained at a constant potential, the potential of the node N3, i.e., the reference potential Vref0, becomes the center potential between the potentials VPH and VPL. For example, by setting the resistance values ​​of the resistors R30 and R31 to 150 kΩ, the reference potential Vref0 is set to the center potential between the potentials VPH and VPL. Figure 6 As described in , the node N3 is also a node connected to the capacitor C10.

[0099] The first reference potential generating circuit 334 includes resistors R32 and R33 connected in series between a wiring supplying the potential VPH and a wiring supplying the potential VPL. One end of resistor R32 is connected to the wiring supplying the potential VPH, while the other end of resistor R32 is connected to one end of resistor R33, and the other end of resistor R33 is connected to the wiring supplying the potential VPL. Hereinafter, the node where resistors R32 and R33 are connected will sometimes be referred to as node N4. The resistance values ​​of resistors R32 and R33 are set, for example, so that the potential at node N4, namely, the first reference potential Vref1, is the center potential between the potentials VPH and VPL. It should be noted that the output impedance of first reference potential generating circuit 334 is preferably smaller than the output impedance of reference potential generating circuit 332 to minimize the impact of noise generated at node N4 on first inspection signal generating circuit 340. For example, by setting the resistance values ​​of resistors R32 and R33 to 1.5 kΩ, first reference potential Vref1 is set to the center potential between the potentials VPH and VPL.

[0100] Second reference potential generating circuit 336 includes resistors R34 and R35 connected in series between a wiring supplying potential VPH and a wiring supplying potential VPL. One end of resistor R34 is connected to the wiring supplying potential VPH, while the other end of resistor R34 is connected to one end of resistor R35, and the other end of resistor R35 is connected to the wiring supplying potential VPL. Hereinafter, the node where resistors R34 and R35 are connected will sometimes be referred to as node N5. The resistance values ​​of resistors R34 and R35 are set, for example, so that the potential at node N5, i.e., the second reference potential Vref2, is the center potential between potentials VPH and VPL. It should be noted that the output impedance of second reference potential generating circuit 336 is preferably smaller than the output impedance of reference potential generating circuit 332 to minimize the impact of noise generated at node N5 on second inspection signal generating circuit 350. For example, by setting the resistance values ​​of resistors R34 and R35 to 1.5 kΩ, second reference potential Vref2 is set to the center potential between potentials VPH and VPL.

[0101] Each of the first switching circuit 335 and the second switching circuit 337 includes, for example, a first input terminal Pin1, a second input terminal Pin2, an output terminal Pout, and a control terminal Psel. The first switching circuit 335 and the second switching circuit 337 each switch, based on a signal supplied to the control terminal Psel, between conducting the first input terminal Pin1 with the output terminal Pout and conducting the second input terminal Pin2 with the output terminal Pout. For example, when the level of the control terminal Psel is high, the first switching circuit 335 and the second switching circuit 337 each conduct the first input terminal Pin1 with the output terminal Pout and disconnect the second input terminal Pin2 from the output terminal Pout. Alternatively, when the level of the control terminal Psel is low, the first switching circuit 335 and the second switching circuit 337 each conduct the second input terminal Pin2 with the output terminal Pout and disconnect the first input terminal Pin1 from the output terminal Pout.

[0102] For example, the first input terminal Pin1 of the first switching circuit 335 is connected to the node N3, the second input terminal Pin2 of the first switching circuit 335 is connected to the node N4, and the output terminal Pout of the first switching circuit 335 is connected to the first inspection signal generating circuit 340. Specifically, the detection signal Vout is input to the first input terminal Pin1 of the first switching circuit 335, and the first reference potential Vref1 is supplied to the second input terminal Pin2 of the first switching circuit 335. Furthermore, the input selection signal SEL1 is supplied to the control terminal Psel of the first switching circuit 335. For example, after the first inspection signal generating circuit 340 switches from being connected to the second input terminal Pin2 via the output terminal Pout to being connected to the first input terminal Pin1 via the output terminal Pout, it begins outputting the first inspection signal Vd1 representing the pseudo residual vibration signal.

[0103] Furthermore, for example, the first input terminal Pin1 of the second switching circuit 337 is connected to the node N3, the second input terminal Pin2 of the second switching circuit 337 is connected to the node N5, and the output terminal Pout of the second switching circuit 337 is connected to the second inspection signal generating circuit 350. Specifically, the detection signal Vout is input to the first input terminal Pin1 of the second switching circuit 337, and the second reference potential Vref2 is supplied to the second input terminal Pin2 of the second switching circuit 337. Furthermore, the input selection signal SEL2 is supplied to the control terminal Psel of the second switching circuit 337.

[0104] Inverter INV1 outputs an inverted signal of the selection signal SEL supplied from the connection state designation circuit 310 to 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.

[0105] The NOR circuit NOR1 outputs a 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 .

[0106] The NOR circuit NOR2 outputs a 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 an input selection signal SEL2 .

[0107] Figure 8The first selection circuit 330 shown in the figure 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 low level. Furthermore, 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 high level and the detection period signal Acut is at a high level. It should be noted that 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.

[0108] 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. Furthermore, 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. It should be noted that 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.

[0109] Thus, in this embodiment, when the selection signal SEL is at a high level, the first inspection signal generating circuit 340 is selected as the circuit for generating the inspection signal VD, and when the selection signal SEL is at a low level, the second inspection signal generating circuit 350 is selected as the circuit for generating the inspection signal VD. In addition, while the detection period signal Acut is at a low level, the detection signal Vout is input to the first inspection signal generating circuit 340 or the second inspection signal generating circuit 350. Figure 14 and Figure 17 As shown in FIG. 1 and FIG. 2 , the period during which the detection period signal Acut is at a low level is also referred to as a detection period Tdet1 or Tdet2 .

[0110] It should be noted that the configuration of the first selection circuit 330 is not limited to Figure 8 For example, the second reference potential generating circuit 336 may be omitted. In this case, the second input terminal Pin2 of the second switching circuit 337 is connected to the node N4, for example.

[0111] Next, refer to Figure 9 The outline of the first inspection signal generating circuit 340 will be described.

[0112] Figure 9 2 is a circuit diagram showing an example of the configuration of the first inspection signal generating circuit 340 .

[0113] As in Figure 7 As described in , the first inspection signal generating circuit 340 includes a first gain adjustment circuit 342 , a low-pass filter circuit 343 , a first filter circuit 344 , and a first buffer circuit 346 .

[0114] 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, the first input signal Vs1 is supplied to the non-inverting input terminal of the operational amplifier OP40 from the first switching circuit 335, and a signal obtained by dividing the output signal of the operational amplifier OP40 by 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 wiring line supplied with a first reference potential Vref1, and the movable contact of the variable resistor RV1 is connected to the inverting input terminal of the operational amplifier OP40. For example, by adjusting the position of the movable contact of the variable resistor RV1, the first gain adjustment circuit 342 can output a signal whose amplitude is adjusted for the first input signal Vs1 to the low-pass filter circuit 343.

[0115] 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 wiring line supplied with a first reference potential Vref1. Furthermore, the non-inverting input terminal of the operational amplifier OP41 is connected to the node N40, and the inverting input terminal of the operational amplifier OP41 is connected to the output terminal of the operational amplifier OP41. The signal at the output terminal of the operational amplifier OP41, namely, the first filtered input signal INbpf1, is input to the first filter circuit 344. Specifically, the first filtered input signal INbpf1, obtained by attenuating the high-frequency components of the signal obtained by adjusting the amplitude of the first input signal Vs1, is input to the first filter circuit 344.

[0116] The first filter circuit 344 is, for example, a multi-feedback bandpass filter including resistor elements R41 , R42 , and R43 , capacitors C41 and C42 , and an operational amplifier OP42 .

[0117] One end of resistor R41 is connected to the output terminal of operational amplifier OP41 of low-pass filter circuit 343, and the other end of resistor R41 is connected to node N41. One end of capacitor C41 is connected to node N41, and the other end of capacitor C41 is connected to the inverting input terminal of operational amplifier OP42. One end of resistor R42 is connected to the inverting input terminal of operational amplifier OP42, and the other end of resistor R42 is connected to the output terminal of operational amplifier OP42. The non-inverting input terminal of operational amplifier OP42 is connected to a wiring supplied with a first reference potential Vref1. One end of resistor R43 is connected to node N41, and the other end of resistor R43 is connected to a wiring supplied with a first reference potential Vref1. In addition, one end of capacitor C42 is connected to node N41, and the other end of capacitor C42 is connected to the output terminal of operational amplifier OP42.

[0118] For example, the first filtered input signal INbpf1 is input to the inverting input terminal of the operational amplifier OP42 via the resistor R41 and the capacitor C41. Specifically, the first input signal Vs1 is input to the inverting input terminal of the operational amplifier OP42 via the first gain adjustment circuit 342, the low-pass filter circuit 343, the resistor R41, and the capacitor C41. The output signal of the operational amplifier OP42 is then fed back to the inverting input terminal of the operational amplifier OP42 via the first feedback path FB1. Furthermore, the output signal of the operational amplifier OP42 is fed back to the inverting input terminal of the operational amplifier OP42 via a second feedback path FB2, which is different from the first feedback path FB1. It should be noted that 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 the resistor R42. Furthermore, 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 capacitor C42 and the capacitor C41. In this way, the first filter circuit 344 has a first feedback path FB1 and a second feedback path FB2 as feedback paths for feeding back the output signal of the operational amplifier OP42 to the inverting input terminal of the operational amplifier OP42 .

[0119] In addition, the output signal of the operational amplifier OP42 is supplied to the first buffer circuit 346 as the first filtered output signal Obpf1 .

[0120] First buffer circuit 346 is a buffer that converts impedance and outputs a low-impedance first inspection signal Vd1. For example, first buffer circuit 346 is configured as a voltage follower using an operational amplifier OP43. Consequently, the first filtered output signal Obpf1 supplied to first buffer circuit 346 is output from first buffer circuit 346 as a low-impedance first inspection signal Vd1.

[0121] Next, the calculation formulas for the amplification factor, center frequency, and Q value of first filter circuit 344 will be described, assuming the amplification factor is H and the center frequency is f0. It should be noted that the Q value is a parameter obtained by dividing the center frequency f0 by the passband width. The passband width is, for example, the bandwidth defined by the frequency at which the amplification factor H reaches -3dB.

[0122] When the potential of the input signal is Vi, the potential of the output signal is Vo, and “2πf0” is “ω0”, a general transfer function of a bandpass filter is represented by equation (1). In the following equation, “·” representing multiplication is used as appropriate.

[0123]

[0124] In addition, when the potential of the first filter input signal INbpf1 is set to Vi and the potential of the first filter output signal Obpf1 is set to Vo, the transfer function of the first buffer circuit 346 is expressed by equation (2). It should be noted that in the following equation, the resistance value of the resistor element and the capacitance value of the capacitor are expressed using symbols with the number at the end of the symbol of the element as a subscript. For example, "R 41 ”, “R 42 ” and “R 43 ” represent the resistance values ​​of the resistor elements R41, R42 and R43 respectively. “C 41 ” and “C 42 ” represent the capacitance values ​​of capacitors C41 and C42 respectively.

[0125]

[0126] Based on equations (1) and (2), the amplification factor H, the center frequency f0, and the Q value of the first filter circuit 344 are expressed by equations (3), (4), and (5), respectively.

[0127]

[0128] Here, in the 41 =C 42 ” and “R=R 41 =R 42When 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) based on equations (3), (4), and (5), respectively.

[0129]

[0130] As can be seen from equations (6) and (7), the amplification factor H is determined by the resistance values ​​of the resistor elements R41 and R42 and the resistance value of the resistor element R43, and the Q value is proportional to the positive square root of the absolute value of the amplification factor.

[0131] It should be noted that the configuration of the first inspection signal generating circuit 340 is not limited to Figure 7 and Figure 9 For example, the first gain adjustment circuit 342 may also be provided between the first filter circuit 344 and the first buffer circuit 346. Alternatively, Figure 9 The illustrated first inspection signal generating circuit 340 omits part or all of the first gain adjustment circuit 342 , the low-pass filter circuit 343 , and the first buffer circuit 346 .

[0132] Next, refer to Figure 10 The outline of the second inspection signal generating circuit 350 will be described.

[0133] Figure 10 2 is a circuit diagram showing an example of the configuration of the second inspection signal generating circuit 350 .

[0134] As in Figure 7 As described in , the second inspection signal generating circuit 350 includes a second gain adjustment circuit 352 , a second filter circuit 354 , and a second buffer circuit 356 .

[0135] The second gain adjustment circuit 352 is Figure 9The first gain adjustment circuit 342 shown is similarly configured as a negative feedback amplifier. For example, the second gain adjustment circuit 352 includes an operational amplifier OP50 and a variable resistor RV2. The operational amplifier OP50 receives the second input signal Vs2 supplied from the second switching circuit 337 at its non-inverting input terminal. The variable resistor RV2 divides the output signal of the operational amplifier OP50 and feeds it 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 wiring line supplied with a second reference potential Vref2, and the movable contact of the variable resistor RV2 is connected to the inverting input terminal of the operational amplifier OP50. For example, by adjusting the position of the movable contact of the variable resistor RV2, the second gain adjustment circuit 352 can output a second filtered input signal INbpf2, whose amplitude is adjusted for the second input signal Vs2, to the second filter circuit 354.

[0136] The second filter circuit 354 is a bandpass filter including, for example, resistors R51 and R52 , capacitors C51 and C52 , and an operational amplifier OP51 , and passes a signal having a predetermined frequency component.

[0137] One end of the resistor element R51 is connected to the output terminal of the operational amplifier OP50 of the second gain adjustment circuit 352. The other end of the resistor element R51 is connected to one end of the capacitor C51, and the other end of the capacitor C51 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 element R52 is connected to the inverting input terminal of the operational amplifier OP51, and the other end of the resistor element R52 is connected to the output terminal of the operational amplifier OP51. Furthermore, the non-inverting input terminal of the operational amplifier OP51 is connected to a wiring line supplied with the second reference potential Vref2.

[0138] For example, the second filtered input signal INbpf2 is input to the inverting input terminal of the operational amplifier OP51 via the resistor R51 and the 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 OP51 is then fed back to the inverting input terminal of the operational amplifier OP51 via a feedback path in which the resistor R52 and the capacitor C52 are connected in parallel.

[0139] In addition, the output signal of the operational amplifier OP51 is supplied to the second buffer circuit 356 as the second filter output signal Obpf2.

[0140] The second buffer circuit 356 is a buffer that converts the impedance and outputs the second inspection signal Vd2 with low impedance. Figure 9 The first buffer circuit 346 shown is similarly configured as a voltage follower using the operational amplifier OP52. Thus, the second filter output signal Obpf2 supplied to the second buffer circuit 356 is output from the second buffer circuit 356 as the low-impedance second inspection signal Vd2.

[0141] Next, regarding the calculation formulas for the low-frequency cutoff frequency, high-frequency cutoff frequency, and amplification factor of the second filter circuit 354, let the low-frequency cutoff frequency be f LPF , set the high frequency cutoff frequency to f HPF , the magnification is set to G for explanation.

[0142] The cut-off frequency f of the second filter circuit 354 LPF is the cutoff frequency of the low-pass filter composed of the capacitor C52 and the resistor R52, and is expressed by equation (9). In addition, the cutoff frequency f of the second filter circuit 354 is HPF is the cutoff frequency of the high-pass filter composed of the capacitor C51 and the resistor R51, and is expressed by equation (10).

[0143]

[0144] 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) represents the angular frequency corresponding to the center frequency of the second filter circuit 354 functioning as a bandpass filter.

[0145]

[0146] It should be noted that the configuration of the second inspection signal generating circuit 350 is not limited to Figure 7 and Figure 10 For example, the second gain adjustment circuit 352 may also be provided between the second filter circuit 354 and the second buffer circuit 356. Alternatively, Figure 10 The second inspection signal generating circuit 350 shown in the figure omits part or all of the second gain adjustment circuit 352 and the second buffer circuit 356 .

[0147] Next, refer to Figure 11 The characteristics of the first filter circuit 344 will be described.

[0148] Figure 11 It is an explanatory diagram for explaining the characteristics of the first filter circuit 344 . Figure 11The figure above shows the relationship between the gain and group delay of the first filter circuit 344 and the frequency. Figure 11 The following figure shows the Figure 11 The first filter circuit 344 of the characteristic shown in the figure above responds to the signal that changes from high level to low level when inputted to the first filter circuit 344. Figure 11 In FIG. 3 , the characteristics of the second filter circuit 354 and the like are shown by a dotted line as a comparison target of the first filter circuit 344 .

[0149] As in Figure 9 As described in , the first filter circuit 344 is a multiple feedback type bandpass filter. Figure 11 As shown in the figure above, a multiple-feedback bandpass filter has a characteristic in which the group delay varies significantly around the center frequency f0. The delay occurring around the center frequency f0 means that the phase rotates around the center frequency f0. For example, if the group delay is Tdg, the phase is φ [rad], and the angular velocity is ω [rad / sec], the group delay characteristic is expressed as "Tdg(ω) = -dφ / dω."

[0150] In the first filter circuit 344, where the group delay varies greatly around the center frequency f0, an overshoot occurs at the center frequency f0. That is, an attenuated vibration waveform occurs at the center frequency f0. Figure 11 As shown in the figure below, even if the input signal maintains a low-level potential, a signal with a decaying vibration waveform is output.

[0151] In contrast, Figure 11 As shown by the dotted line in the upper figure, the second filter circuit 354 does not have the characteristic that the group delay changes significantly around the center frequency f0. In the second filter circuit 354, as shown in FIG. Figure 11 As shown by the dotted line in the lower figure, when the input signal is maintained at a low level potential, the output signal converges to a predetermined potential.

[0152] In this embodiment, by making the decaying vibration waveform generated at the center frequency f0 close to a sine wave, the output signal of the first filter circuit 344, namely the first filtered output signal Obpf1, can be processed as a pseudo residual vibration signal that simulates the residual vibration of the ejection portion D. Figure 11 The time ts shown is the time it takes for the potential of the first filter input signal INbpf1 input to the first filter circuit 344 to change from the maximum value to the minimum value. For example, to generate a decaying vibration waveform close to a sine wave, the center frequency f0 is designed to be less than "1 / (2ts)".

[0153] Next, refer to Figure 12 The simulation results of the first filter circuit 344 will be described.

[0154] Figure 12 is a diagram showing the simulation results of the first filter circuit 344. It should be noted that Figure 12 The simulation results of the response of the first filter circuit 344 when a signal changing from a high level to a low level is input are shown. Figure 12 In the simulation shown, the time ts from when the potential of the signal input to the first filter circuit 344 changes from the maximum value to the minimum value is 1 μsec, and “1 / (2ts)” is 500 kHz.

[0155] 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.

[0156] like Figure 12 As shown in FIG, when the center frequency f0 is below "1 / (2ts)", the output signal of the first filter circuit 344 becomes close to a sine wave. Figure 12 Although not shown in the figure, it was confirmed from simulation results that when the center frequency f0 is "1 / ts", the output signal of the first filter circuit 344 is distorted, and the output signal of the first filter circuit 344 cannot be regarded as a sine wave.

[0157] Next, refer to Figure 13 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 will be briefly described.

[0158] Figure 13 This 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 .

[0159] For example, at the detection end time point when the first input signal Vs1 switches from the detection signal Vout to the first reference potential Vref1, the potential Vn40 at the node N40 is maintained at the potential of the output signal of the operational amplifier OP40 at the detection end time point via the capacitor C40. Consequently, the potential Vn40 at the node N40 converges to the first reference potential Vref1 using the time constant of the low-pass filter circuit 343. For example, if the potential Vn40 at the node N40 at the detection end time point is higher than the first reference potential Vref1, the capacitor C40 discharges to the first gain adjustment circuit 342 via the first path PH1. Alternatively, if the potential Vn40 at the node N40 at the detection end time point is lower than the first reference potential Vref1, the capacitor C40 is charged from the first gain adjustment circuit 342 via the second path PH2.

[0160] The potential Vn40 of the node N40 after the detection end time is expressed by equation (14) using the first reference potential Vref1 , the elapsed time t from the detection end time, the time constant τ, and the potential difference ΔVn40 between the potential Vn40 at the detection end time and the first reference potential Vref1 .

[0161] Vn40=ΔVn40·exp(-t / τ)+Vref1…(14)

[0162] Note that “exp( )” in equation (14) represents an exponential function. The potential difference ΔVn40 in equation (14) is expressed by equation (15) using, for example, the potential Vn40 at the detection end time point and the first reference potential Vref1 .

[0163] ΔVn40=Vn40-Vref1…(15)

[0164] Furthermore, when the output impedance of the circuit preceding the low-pass filter circuit 343 is set to Rp, the time constant τ in equation (14) is expressed by equation (16). It should be noted that in this embodiment, since the circuit preceding the low-pass filter circuit 343 is the first gain adjustment circuit 342, the output impedance Rp in equation (16) represents the output impedance of the first gain adjustment circuit 342.

[0165] τ=C 40 ·(R 40 +Rp) …(16)

[0166] It should be noted that, when the output impedance of the operational amplifier OP40 is very small compared to the impedance of the variable resistor RV, the output impedance of the operational amplifier OP40 may also be regarded as the output impedance of the first gain adjustment circuit 342 .

[0167] Furthermore, for example, in a configuration where 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 generating circuit 334. In this case, the output impedance Rp is represented by equation (17).

[0168] Rp=(R 32 ·R 33 ) / (R 32 +R 33 ) …(17)

[0169] For example, the low-pass filter circuit 343 is preferably designed so that the relationship between the time ts until the potential of the detection signal Vout input as the first input signal Vs1 to the first inspection signal generating circuit 340 changes from the maximum value to the minimum value and the time constant τ satisfies the equation (18).

[0170] ts / 2≈τ~4.6τ …(18)

[0171] "τ" in equation (18) corresponds to the time it takes for capacitor C40 to reach approximately 63% charge or discharge, and "4.6τ" in equation (18) corresponds to the time it takes for capacitor C40 to reach approximately 100% charge or discharge. Therefore, equation (18) means that half of time ts is included in the range from the time it takes for capacitor C40 to reach approximately 63% charge or discharge to the time it takes for capacitor C40 to reach approximately 100% charge or discharge.

[0172] Here, in the first filter circuit 344, following the low-pass filter circuit 343, a circuit comprising a capacitor C41, a resistor R42, and an operational amplifier OP42 functions as a differentiating 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 abrupt potential changes, the first filtered output signal Obpf1 output from the first filter circuit 344 may be distorted. Distortion of the first filtered output signal Obpf1 increases the amplitude and other variations of the first inspection signal Vd1 generated as a pseudo-residual vibration signal, potentially reducing the accuracy of determining the state of the ejection portion D. Therefore, in this embodiment, the potential of the first input signal Vs1 is stabilized during the non-detection period, when the detection signal Vout is not input to the first inspection signal generation circuit 340, thereby suppressing distortion of the first filtered output signal Obpf1. Specifically, in this embodiment, the first switching circuit 335 and the low-pass filter circuit 343 allow the potential of the first input signal Vs1 during the non-detection period to converge to the first reference potential Vref1 , thereby suppressing distortion of the first filter output signal Obpf1 .

[0173] Next, refer to Figure 14 The effects of the first switching circuit 335 and the low-pass filter circuit 343 will be described.

[0174] Figure 14 3 is an explanatory diagram for explaining the effects of the first switching circuit 335 and the low-pass filter circuit 343. It should be noted that Figure 14 The “with distortion countermeasures” shows the simulation results of the first filter circuit 344 when the first switching circuit 335 and the low-pass filter circuit 343 are provided in the upstream stage of the first filter circuit 344. Figure 14 The "Comparative Example" shows simulation results for first filter circuit 344 when first switching circuit 335 and low-pass filter circuit 343 are not provided in the upstream stage of first filter circuit 344. However, in the comparative example, a switch is provided instead of first switching circuit 335 to simply switch whether switching circuit 31 and detection circuit 33 are electrically connected.

[0175] like Figure 14 As shown, in the comparative example without the first switching circuit 335 and the low-pass filter circuit 343, noise is generated in the first filter input signal INbpf1 before the start of the detection period Tdet1. Furthermore, in the comparative example, the potential of the first filter input signal INbpf1 changes dramatically at the end of the detection period Tdet1. Consequently, in the comparative example, distortion occurs in the first filter output signal Obpf1 between the period before the start of the detection period Tdet1 and the end of the detection period Tdet1.

[0176] In contrast, in the configuration including the first switching circuit 335 and the low-pass filter circuit 343, the generation of noise in the first filter input signal INbpf1 and the sudden change in the potential of the first filter input signal INbpf1 are suppressed. As a result, in the configuration including the first switching circuit 335 and the low-pass filter circuit 343, the generation of distortion in the first filter output signal Obpf1 is suppressed.

[0177] Thus, in this embodiment, since distortion of the first filter output signal Obpf1 is suppressed, variations in the amplitude value of the first inspection signal Vd1 generated as a pseudo residual vibration signal can be suppressed. As a result, in this embodiment, the state of the discharge portion D can be determined with high accuracy.

[0178] In addition, if Figure 14 As shown, the first filtering circuit 344 can output a first filtering output signal Obpf1 having a period of more than one cycle based on a first filtering input signal INbpf1 having a period of more than one quarter cycle and less than one cycle.

[0179] Next, refer to Figure 15The operation of the inkjet printer 1 will be described.

[0180] Figure 15 This is a timing diagram illustrating an example of the operation of the inkjet printer 1 during a unit period TU. In this embodiment, when the inkjet printer 1 is performing printing or ejection status determination, one or more unit periods TU are set as the operation period of the inkjet printer 1. The inkjet printer 1 according to this embodiment is capable of driving each ejection unit D[m] during each unit period TU to perform printing or ejection status determination. For example, when performing ejection status determination, the inkjet printer 1 is capable of driving the ejection unit D to be determined during each unit period TU and detecting the detection signal Vout[m] from the ejection unit D to be determined.

[0181] The control unit 2 outputs the latch signal LAT having the pulse PlsL. Thus, the control unit 2 defines the unit period TU as the period from the rising edge of the pulse PlsL to the rising edge of the next pulse PlsL.

[0182] The printing signal SI includes, for example, M individual designation signals Sd[1] to Sd[M] corresponding one-to-one to the M ejection units D[1] to D[M]. When the inkjet printer 1 performs a printing process or an ejection state determination process, the individual designation signal Sd[m] specifies the driving method of the ejection unit D[m] in each unit period TU. For example, before each unit period TU, the control unit 2 supplies the printing 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. Then, the connection state designation circuit 310 generates the connection state designation signals Qa[m] and Qs[m] based on the individual designation signals Sd[m] in the unit period TU. In addition, the connection state designation circuit 310 generates the selection signal SEL and the detection period signal Acut based on at least a portion of the printing signal SI, the latch signal LAT, and the period specification signal Tsig.

[0183] For example, in the unit period TU during which the printing process is executed, the ejection unit D[m] is designated as either the ejection unit D that forms dots or the ejection unit D that does not form dots by the individual designation signal Sd[m]. In addition, for example, in the unit period TU during which the ejection state determination process is executed, the ejection unit D[m] is designated as whether to be driven as the ejection unit D to be determined by the individual designation signal Sd[m]. It should be noted that Figure 15 In FIG. 1 , the connection state designation signals Qa[m] and Qs[m] are shown when the ejection unit D[m] is designated as the ejection unit D to be determined by the individual designation signal Sd[m] during the unit period TU of the ejection state determination process. Figure 15In the following, the operation of the inkjet printer 1 when the discharge state determination process is executed will be described.

[0184] When executing the ejection state determination process, for example, the control unit 2 outputs a period specifying signal Tsig having a pulse PlsT1 and a pulse PlsT2. Thus, the control unit 2 divides 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.

[0185] Furthermore, the connection state designation circuit 310 controls the detection period signal Acut to define the detection period Tdet1 of the detection signal Vout[m]. For example, 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. The time from the start to the end of the detection period Tdet1 corresponds to the time allocated for detecting the residual vibration of the ejection portion D. It should be noted that Figure 15 FIG shows a detection period Tdet1 when the detection signal Vout[m] is supplied to the first inspection signal generating circuit 340. When the detection signal Vout[m] is supplied to the first inspection signal generating circuit 340, a pseudo residual vibration signal that simulates the residual vibration of the ejection portion D[m] is generated during the inspection period Tche. Figure 15 In FIG. 3 , since it is assumed that the detection signal Vout[m] is supplied to the first inspection signal generating circuit 340 , the selection signal SEL is maintained at a high level.

[0186] Furthermore, the drive signal COM used for the ejection state determination process includes, for example, a pulse PA supplied to the wiring La during the control period TSS1. The pulse PA used for the ejection state determination process may be a pulse that does not eject ink from the nozzle N, or a pulse that does so, as long as it vibrates the vibration plate 321. In this embodiment, the pulse PA is assumed to be a pulse that does not eject ink from the nozzle N. It should be noted that during the printing process, a pulse that causes ink to be ejected from the nozzle N is supplied to the wiring La during the unit period TU, instead of the pulse PA.

[0187] The pulse PA is 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.

[0188] For example, pulse PA includes waveform element Pa1, in which the potential changes from potential V0 to potential VLa; waveform element Pa2, in which the potential is maintained at potential VLa at the end of waveform element Pa1; and waveform element Pa3, in which the potential changes from potential VLa to potential V0. Hereinafter, waveform elements Pa1, Pa2, and Pa3 may be collectively referred to as waveform element Pa.

[0189] The waveform element Pa1 is an expansion element for displacing the piezoelectric element Zb in the Z2 direction. If it is an expansion element, the potential of the drive signal COM changes in order to drive the piezoelectric element PZ to expand the volume of the cavity CV. Therefore, in the waveform element Pa1, the potential of the drive signal COM changes in such a way that the volume of the cavity CV expands. When the volume of the cavity CV expands, as shown in FIG. Figure 4 As in the state of stage-2 shown, the surface of the ink in the nozzle N is pulled in the Z2 direction, which is opposite to the ejection direction. Hereinafter, the surface of the ink in the nozzle N pulled in the direction opposite to the ejection direction may be referred to as "pull".

[0190] The waveform element Pa2 is a maintaining element for maintaining the position of the piezoelectric body Zb in the Z-axis direction. For example, in the waveform element Pa2, the potential of the driving signal COM is maintained to drive the piezoelectric element PZ to maintain the volume of the cavity CV expanded by the waveform element Pa1.

[0191] In addition, the waveform element Pa3 is a contraction element for displacing the piezoelectric body Zb in the Z1 direction. If it is a contraction element, the potential of the drive signal COM changes in order to drive the piezoelectric element PZ to shrink the volume of the cavity CV. Therefore, in the waveform element Pa3, the potential of the drive signal COM changes in such a way as to shrink the volume of the cavity CV. When the volume of the cavity CV shrinks, the surface of the ink in the nozzle N is pushed in the ejection direction, that is, in the Z1 direction. In this embodiment, the waveform element Pa3 pushes the surface of the ink in the nozzle N in the Z1 direction to such an extent that the ink is not ejected from the nozzle N. Hereinafter, the surface of the ink in the nozzle N that is pushed in the ejection direction may be referred to as a push.

[0192] Thus, 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 the pull-push waveform.

[0193] For example, when the discharge unit D[m] is designated as the discharge unit D to be determined by the individual designation signal Sd[m], 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. The connection state designation circuit 310 then 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.

[0194] It should be noted that, in the case of switching between the control period TSS1 and the control period TSS2, it is preferred that the states of the switches SWa[m] and SWs[m] are switched between on and off via the state in which both switches SWa[m] and SWs[m] are on. That is, it is preferred that the timing when the connection state designation signal Qs[m] changes from a low level to a high level is earlier than the timing when the connection state designation signal Qa[m] changes from a high level to a low level. In addition, it is preferred that the timing when the connection state designation signal Qs[m] changes from a high level to a low level is later than the timing when the connection state designation signal Qa[m] changes from a low level to a high level. In this case, when switching between the control period TSS1 and the control period TSS2, the state in which both switches SWa[m] and SWs[m] are off does not occur, and therefore, it is possible to suppress Figure 6 The potential of the node N2 shown changes due to switching noise or the like.

[0195] In addition, it is preferred that the timing at which the detection period signal Acut transitions from a high level to a low level is 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. In addition, it is preferred that the timing at which the detection period signal Acut transitions from a low level to a high level is 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. To this end, 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. It should be noted that, as long as the above-mentioned transition timing is met, the connection state designation circuit 310 may also set the detection period signal Acut to a low level upon the start of the pulse PlsT1 and set the detection period signal Acut to a high level upon the start of the next pulse PlsL.

[0196] By ensuring that the timing of the level transition of the detection period signal Acut satisfies the aforementioned transition timing, the generation of noise and the like in the first input signal Vs1 and the second input signal Vs2 can be suppressed. It should be noted that the timing of the level transition of the detection period signal Acut does not need to satisfy the aforementioned transition timing as long as the noise and the like generated in the first input signal Vs1 and the second input signal Vs2 are suppressed within an allowable range.

[0197] During the control period TSS1, the piezoelectric element PZ[m] of the ejection part D[m] to be determined is driven by the pulse PA of the drive signal COM. Specifically, during the control period TSS1, the piezoelectric element PZ[m] of the ejection part D[m] to be determined is displaced by the pulse PA of the drive signal COM. As a result, vibrations are generated in the ejection part D[m] to be determined. The vibrations generated during the control period TSS1 also remain during the control period TSS2. Therefore, during the control period TSS2, the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] of the ejection part D[m] to be determined changes according to the residual vibrations generated in the ejection part 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 part D to be determined is a potential corresponding to the electromotive force of the piezoelectric element PZ caused by the residual vibrations generated in the ejection part D to be determined. The potential of the upper electrode Zu is then detected as the potential signal Vzu during the control period TSS2. Consequently, changes in the potential of the upper electrode Zu are detected as the detection signal Vout during the control period TSS2. Consequently, the detection signal Vout is input to the detection circuit 33 as a residual vibration signal generated by the vibration remaining in the ejection portion D.

[0198] The detection signal Vout input to the detection circuit 33 is supplied as the first input signal Vs1 to the first inspection signal generating circuit 340 during the detection period Tdet1 within the control period TSS2. Consequently, during the inspection period Tche following the detection period Tdet1, the first inspection signal generating circuit 340 generates the first inspection signal Vd1 as a pseudo residual vibration signal that mimics the residual vibration of the discharge portion D[m].

[0199] Next, the operation of the inkjet printer 1 during printing will be briefly described. It should be noted that during printing, the unit period TU may not be divided into the control period TSS1 and the control period TSS2. In this case, during the unit period TU, the period specifying signal Tsig may be maintained at a low level, and the detection period signal Acut may be maintained at a high level.

[0200] For example, regardless of whether the ejection unit D[m] is designated as the ejection unit D for forming a dot, the connection state designation signal Qs[m] is maintained at a low level during the unit period TU. Furthermore, the connection state designation signal Qa[m] is set to a high level or a low level depending on whether the ejection unit D[m] is designated as the ejection unit D for forming a dot.

[0201] For example, when the individual designation signal Sd[m] designates the ejection portion D[m] as the ejection portion D that forms a dot, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a high level during the unit period TU. Note that the connection state designation signal Qa corresponding to the ejection portion D that does not form a dot is set to a low level during the unit period TU.

[0202] By setting the connection state designation signal Qa[m] to a high level, the drive signal COM including a pulse for ejecting ink from the nozzle N is supplied from the drive signal generating unit 4 to the ejection portion D for forming the dot. For example, the pulse for ejecting ink from the nozzle N is supplied to the wiring La in the unit period TU. The pulse for ejecting ink from the nozzle N may also be a pull-push waveform like the pulse PA. In this case, the pulse for ejecting ink from the nozzle N is defined as follows: the potential difference at the start and end of the waveform element, i.e., the contraction element, which is the waveform element for ejecting ink, is greater than the potential difference at the start and end of the waveform element Pa3 of the pulse PA. It should be noted that the pulse for ejecting ink from the nozzle N is not limited to a pull-push waveform. For example, the pulse for ejecting ink from the nozzle N may also be a pull-push-pull waveform.

[0203] Each waveform element of the pulse that causes ink to be ejected from the nozzle N is defined so that, when the individual drive signal Vin[m] containing the pulse is supplied to the ejection portion D[m], a predetermined amount of ink is ejected from the ejection portion 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 included in the ejection portion D[m] decreases compared to when the potential is low. Therefore, when the ejection portion D[m] is driven by the individual drive signal Vin[m] containing the pulse that causes ink to be ejected, the ink within the ejection portion D[m] is ejected from the nozzle N using the waveform element in which the potential of the individual drive signal Vin[m] changes from low to high.

[0204] For example, each waveform element of the pulse that causes ink to be ejected from the nozzle N is determined based on the ejection characteristics of the ink ejected from the ejection portion D. The ejection characteristics of the ink include, for example, the amount of ink ejected in the form of ink droplets and the ejection speed of the ejected ink droplets. It should be noted that the ejection speed of the ink droplets varies, for example, according to the viscosity of the ink. For example, the ejection speed of the ink droplets having a viscosity greater than the prescribed viscosity decreases compared to the ejection speed of the ink droplets having a viscosity below the prescribed viscosity. In this embodiment, the thickening state of the ink in the ejection portion D can be determined based on the pseudo residual vibration signal, and details will be given later. Figure 16 Narrating in.

[0205] In this embodiment, since the pulse PA is assumed to not cause ink to be ejected from the nozzles N, the ejection status determination process can be executed even when the head unit 3 is not positioned over the ejected ink receiving portion 80. For example, when printing is performed on a pass-by-pass basis while the head unit 3 is moving in the X-axis direction, the ejection status determination process can be executed between passes. Furthermore, the ejection status determination process can 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 status determination process can be executed while maintenance is being performed.

[0206] It should be noted that the operation of the inkjet printer 1 is not limited to 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, the ejection state determination process is preferably performed with the head unit 3 positioned above the ejection ink receiving portion 80, for example.

[0207] Furthermore, for example, when executing the ejection state determination process, the control unit 2 may output a period specifying signal Tsig having only the pulse PlsT1 of the pulses PlsT1 and PlsT2. In this case, the connection state specifying circuit 310 may set the detection period signal Acut to a low level upon the start or end of the pulse PlsT1, and set the detection period signal Acut to a high level upon the start of the next pulse PlsL, so as to meet the above-mentioned transition timing.

[0208] In addition, for example, Figure 15While the example in FIG. 1 illustrates a case where there is only one drive signal COM, the present invention is not limited to this embodiment. For example, multiple drive signals COM may be used, including a drive signal COM that prevents ink from being ejected from the nozzle N and a drive signal COM that causes ink to be ejected from the nozzle N. In this case, the pulse PA that prevents ink from being ejected can also be used to prevent ink thickening during printing. Furthermore, the drive signal COM that causes ink to be ejected from the nozzle N may include multiple pulses that cause ink to be ejected from the nozzle N to form dots of varying sizes.

[0209] Next, refer to Figure 16 The first inspection signal Vd1 generated by the first inspection signal generating circuit 340 will be described.

[0210] Figure 16 3 is an explanatory diagram for explaining an example of the first inspection signal Vd1 generated by the first inspection signal generating circuit 340. Figure 16 In order to facilitate the understanding of the description, the end of each symbol of the plurality of unit periods TU is marked with any of the numbers 1, 2, and 3. Figure 16 In this example, assume that during unit period TU1, discharge unit D[a] is designated as the discharge unit D to be determined, and during unit period TU2, discharge unit D[b] is designated as the discharge unit D to be determined. Note that value a is a natural number satisfying "1 ≤ a ≤ M," and value b is a natural number different from value a that satisfies "1 ≤ b ≤ M." Furthermore, time ts is the time from when the potential of detection signal Vout input to first inspection signal generation circuit 340 changes from its maximum value to its minimum value, or the time from when the potential of detection signal Vout changes from its minimum value to its maximum value, during detection period Tdet1.

[0211] During detection period Tdet1, when detection period signal Acut is at a low level, detection signal Vout is input as first input signal Vs1 to first inspection signal generation circuit 340. For example, during detection period Tdet1[a] of unit period TU1, detection signal Vout representing the residual vibration of ejection unit D[a] driven by independent drive signal Vin[a] is input as first input signal Vs1 to first inspection signal generation circuit 340. Then, upon completion of detection period Tdet1[a], first input signal Vs1 switches from detection signal Vout to first reference potential Vref1. Consequently, during inspection period Tche[a], the potential of first input signal Vs1 converges to first reference potential Vref1.

[0212] It should be noted that if Figure 16As shown, the detection signal Vout input to first inspection signal generation circuit 340 as first input signal Vs1 is a detection signal Vout with a duration of less than one cycle. Therefore, in first inspection signal generation circuit 340, the length of detection period Tdet1 can be shortened compared to second inspection signal generation circuit 350, which receives detection signal Vout with a duration of more than one cycle as second input signal Vs2. Consequently, in this embodiment, the unit period TU when first inspection signal generation circuit 340 generates inspection signal VD can be shortened compared to the unit period TU when second inspection signal generation circuit 350 generates inspection signal VD.

[0213] 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 generating circuit 340. Therefore, even when the individual drive signal Vin[b] is supplied to the ejection unit D[b] during the inspection period Tche[a], the first inspection signal generating circuit 340 can generate the first inspection signal Vd1 that mimics the decaying wave of the detection signal Vout indicating the residual vibration of the ejection unit D[a].

[0214] For example, Figure 11 As described in [ ], the first filter circuit 344 is a multi-feedback bandpass filter with a characteristic in which the group delay varies 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 detection signal Vout is input to the first filter circuit 344, that is, after the detection period Tdet1 ends, the first filter circuit 344 outputs a first filtered output signal Obpf1 having a damped oscillation waveform generated at the center frequency f0. Thus, for example, during the inspection period Tche[a], the first inspection signal generation circuit 340 outputs a first inspection signal Vd1 to the inspection unit 6. This first inspection signal Vd1 has a damped oscillation waveform corresponding to the detection signal Vout representing the residual vibration of the ejection portion D[a]. Furthermore, for example, during the inspection period Tche[b], the first inspection signal generation circuit 340 outputs a first inspection signal Vd1 to the inspection unit 6. This first inspection signal Vd1 has a damped oscillation waveform corresponding to the detection signal Vout representing the residual vibration of the ejection portion D[b].

[0215] The inspection unit 6 determines the state of the ejection unit 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]. Furthermore, the inspection unit 6 determines the state of the ejection unit 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]. Note that the inspection unit 6 may also determine the state of the ejection unit 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 ejection unit D based on both 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.

[0216] exist Figure 16 In the example shown, the solid line waveform of the first input signal Vs1 represents the waveform of the first input signal Vs1 when the state of the ejection portion D is normal, and the dotted line waveform of the first input signal Vs1 represents the waveform of the first input signal Vs1 when the ink in the ejection portion D is in a thickened state. Similarly, the solid line waveform of the inspection signal VD represents the waveform of the inspection signal VD when the state of the ejection portion D is normal, and the dotted line waveform of the inspection signal VD represents the waveform of the inspection signal VD when the ink in the ejection portion D is in a thickened state. Figure 16 As shown, the amplitude of the inspection signal VD is different when the state of the ejection portion D is normal and when the ink in the ejection portion D is in a thickened state.

[0217] For example, the amplitude of the inspection signal VD when the ink in the discharge portion D is in a thickened state is smaller than the amplitude of the inspection signal VD when the state of the discharge portion D is normal. Figure 16 The difference dA11 represents the difference between the amplitude of the first peak of the inspection signal VD in the inspection period Tche when the state of the ejection portion D is normal and the amplitude of the first peak of the inspection signal VD in the inspection period Tche when the ink in the ejection portion D is in a thickened state. Figure 16 The difference dA21 represents the difference between the amplitude of the second peak of the inspection signal VD in the inspection period Tche when the state of the ejection portion D is normal and the amplitude of the second peak of the inspection signal VD in the inspection period Tche when the ink in the ejection portion D is in a thickened state.

[0218] The inventors have confirmed through simulation that the rate of change of the amplitude of the inspection signal VD when the state of the ejection portion D is normal and when the ink in the ejection portion D is in a thickened state is approximately the same as when the second inspection signal Vd2 is used as the inspection signal VD. For example, in the simulation when the first inspection signal Vd1 is used as the inspection signal VD, the rate of change calculated based on the difference dA11, that is, the rate of change of the amplitude of the first peak of the inspection signal VD during the inspection period Tche, is 43%. In addition, the simulation result of the rate of change calculated based on the difference dA21, that is, the rate of change of the amplitude of the second peak of the inspection signal VD during the inspection period Tche, is 54%. In contrast, in the simulation when the second inspection signal Vd2 is used as the inspection signal VD, the rate of change calculated based on the difference dA21, that is, the rate of change of the amplitude of the second peak of the inspection signal VD during the inspection period Tche, is 54%. Figure 17 The differential dA12 shown calculates a rate of change of 36%, based on Figure 17 The calculated rate of change of the difference dA22 shown is 50%. It should be noted that 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. Figure 17 The differences dA12 and dA22 shown correspond to the differences dA11 and dA21, respectively.

[0219] In this manner, even when the first inspection signal Vd1 is used as the inspection signal VD, the state of the discharge portion D can be determined based on the rate of change of the amplitude of the inspection signal VD relative to a reference amplitude value. The reference amplitude value is predetermined based on, for example, the amplitude of the inspection signal VD when the state of the discharge portion D is normal.

[0220] It should be noted that the method for determining the amplitude of the inspection signal VD is not particularly limited, and a known method can be used. For example, the inspection unit 6 may compare a plurality of different threshold values ​​with the potential of the inspection signal VD, generate a plurality of pulses each representing the comparison results of the plurality of threshold values ​​with the potential of the inspection signal VD, and determine the amplitude of the inspection signal VD based on the width of the plurality of generated pulses. The pulse representing the comparison result of the threshold value with the potential of the inspection signal VD is, for example, a pulse that becomes high while the potential of the inspection signal VD is above the threshold value. It should be noted that, if the inspection unit 6 includes, for example, a comparator that compares the plurality of threshold values ​​with the potential of the inspection signal VD, the comparator may also be provided within the head unit 3. In this case, the inspection unit 6 includes a comparator provided within the head unit 3 and an element provided outside the head unit 3.

[0221] Thus, in this embodiment, part or all of the inspection period Tche[a], which generates the first inspection signal Vd1 corresponding to the residual vibration of the discharge unit D[a], can overlap with the control period TSS1 for driving the discharge unit D[b], which is different from the discharge unit D[a]. Therefore, in this embodiment, by using the first inspection signal Vd1 as the inspection signal VD for determining the status of the discharge unit D, the time required to determine the status of the multiple discharge units D, including the discharge unit D[a] and the discharge unit D[b], can be shortened.

[0222] Next, refer to Figure 17 The second inspection signal Vd2 generated by the second inspection signal generating circuit 350 will be described.

[0223] Figure 17 3 is an explanatory diagram for explaining an example of the second inspection signal Vd2 generated by the second inspection signal generating circuit 350. Figure 17 In order to facilitate the understanding of the description, the end of each symbol of the plurality of unit periods TU is marked with either a number 1 or a number 2. Figure 17 In the example, it is assumed that the ejection unit D[a] is designated as the ejection unit D to be determined in the unit period TU1. It should be noted that the value a is a natural number that satisfies "1≤a≤M". Figure 17 In FIG. 1 , a detection period Tdet1 when the first inspection signal Vd1 is used as the inspection signal VD is indicated by a dotted arrow.

[0224] During detection period Tdet2, when detection period signal Acut is at a low level, detection signal Vout is input to second inspection signal generation circuit 350 as second input signal Vs2. For example, during detection period Tdet2[a] of unit period TU1, detection signal Vout representing the residual vibration of ejection unit D[a] driven by independent drive signal Vin[a] is input to second inspection signal generation circuit 350 as second input signal Vs2. Subsequently, upon completion of detection period Tdet2[a], second input signal Vs2 switches from detection signal Vout to second reference potential Vref2. Consequently, during control period TSS1 of unit period TU2, the potential of second input signal Vs2 converges to second reference potential Vref2.

[0225] It should be noted that if Figure 17 As shown, the detection signal Vout input to the second inspection signal generating circuit 350 as the second input signal Vs2 is a detection signal Vout having a period of more than one cycle. Therefore, in the second inspection signal generating circuit 350, the detection period Tdet2 is longer than the detection period Tdet1 when the first inspection signal Vd1 is used as the inspection signal VD.

[0226] In addition, as in Figure 10 As described in [ ], second filter circuit 354 is a bandpass filter that passes signals with predetermined frequency components. To this end, second filter circuit 354 outputs a second filtered output signal Obpf2, which is a signal obtained by removing frequency components other than the predetermined frequency component from the second filtered input signal INbpf2, after adjusting the amplitude of detection signal Vout. Thus, for example, during detection period Tdet2[a], second inspection signal generation circuit 350 outputs a second inspection signal Vd2 to inspection unit 6. This second inspection signal Vd2 is a signal obtained by removing frequency components other than the predetermined frequency component from the signal corresponding to detection signal Vout representing the residual vibration of ejection portion D[a].

[0227] It should be noted that 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 generating circuit 350. Therefore, when the state of the ejection unit D[a] is determined based on the second inspection signal Vd2, it is preferable that the other ejection units D are not driven until the detection period Tdet2[a] ends, that is, until the generation of the second inspection signal Vd2 is completed.

[0228] As described above, the second inspection signal generating circuit 350 generates the second inspection signal Vd2 based on the detection signal Vout for one or more cycles during the detection period Tdet2[a]. Therefore, the inspection unit 6 determines the state of the discharge portion D[a] based on the second inspection signal Vd2 output as the inspection signal VD[a] from the second inspection signal generating circuit 350 during the detection period Tdet2[a].

[0229] exist Figure 17 In the example shown, the solid line waveform of the second input signal Vs2 represents the waveform of the second input signal Vs2 when the state of the ejection portion D is normal, and the dotted line waveform of the second input signal Vs2 represents the waveform of the second input signal Vs2 when the ink in the ejection portion D is in a thickened state. Similarly, the solid line waveform of the inspection signal VD represents the waveform of the inspection signal VD when the state of the ejection portion D is normal, and the dotted line waveform of the inspection signal VD represents the waveform of the inspection signal VD when the ink in the ejection portion D is in a thickened state. Even in the case where the inspection signal VD is generated by the second inspection signal generating circuit 350, as shown in FIG. Figure 17 As shown, the amplitude of the inspection signal VD also differs when the state of the ejection portion D is normal and when the ink in the ejection portion D is in a thickened state.

[0230] For example, the amplitude of the inspection signal VD when the ink in the discharge portion D is in a thickened state is smaller than the amplitude of the inspection signal VD when the state of the discharge portion D is normal. Figure 17The difference dA12 represents the difference between the amplitude of the second peak of the inspection signal VD during the detection period Tdet2 when the state of the ejection portion D is normal and the amplitude of the second peak of the inspection signal VD during the detection period Tdet2 when the ink in the ejection portion D is in a thickened state. Figure 17 The difference dA22 represents the difference between the amplitude of the third peak of the inspection signal VD in the detection period Tdet2 when the state of the ejection portion D is normal and the amplitude of the third peak of the inspection signal VD in the detection period Tdet2 when the ink in the ejection portion D is in a thickened state.

[0231] It should be noted that Figure 17 The second peak of the inspection signal VD in the detection period Tdet2 shown is Figure 16 The first peak of the inspection signal VD in the inspection period Tche shown corresponds to the first peak of the inspection signal VD. Figure 17 The third peak of the inspection signal VD in the detection period Tdet2 shown is Figure 16 The shown inspection period Tche corresponds to the second peak of the inspection signal VD.

[0232] Thus, even when the second inspection signal Vd2 is used as the inspection signal VD, the state of the ejection portion D can be determined based on the rate of change of the amplitude of the inspection signal VD relative to the reference amplitude value, similar to the case of using the first inspection signal Vd1 as the inspection signal VD.

[0233] In addition, as described above, the second check signal Vd2 is generated based on the detection signal Vout having one or more cycles. For this reason, in this embodiment, the state of the ejection unit D can also be determined based on part or all of the amplitude, cycle, and phase of the second check signal Vd2. In addition, in this embodiment, multiple abnormal states, including the thickening state of the ink in the ejection unit D, can be determined based on the second check signal Vd2, which is generated based on the detection signal Vout having one or more cycles. Examples of abnormal states other than the thickening state of the ink in the ejection unit D include a state in which an abnormal ejection occurs due to bubbles mixed in the cavity CV of the ejection unit D, and a state in which an abnormal ejection occurs due to foreign matter adhering to the nozzle N of the ejection unit D. For example, the state determination of the ejection unit D in the second mode in which the state of the ejection unit D is determined based on the second check signal Vd2 is effective when the cause of the abnormal ejection occurs is to be accurately determined.

[0234] It should be noted that since the first mode of determining the state of the ejection unit D based on the first check signal Vd1 can shorten the unit period TU compared to the second mode, it is effective for determining the state of the ejection unit D in a shorter time. For example, immediately after the inkjet printer 1 is started, the ink in the chamber CV is stagnant and likely thickened. Therefore, the first mode of determining the state of the ejection unit D can be performed after the inkjet printer 1 is started, prioritizing the second mode. This prevents the time required to determine the state of the ejection unit D after the inkjet printer 1 is started. Thus, in this embodiment, the mode for determining the state of the ejection unit D can be switched based on the purpose of the determination and the scenario in which the determination is performed. For example, the first mode can determine the thickening state of the ink in the ejection unit D based on the first check signal Vd1. Alternatively, the second mode can determine multiple abnormalities, including the thickening state of the ink in the ejection unit D, based on the second check signal Vd2.

[0235] As described above, in this embodiment, the inkjet printer 1 includes a head unit 3, a drive signal generating 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 unit D based on the received signal. The head unit 3 includes an ejection unit D comprising a nozzle N, a piezoelectric element PZ driven by the drive signal COM, and a cavity CV that ejects ink from the nozzle N in response to the driving of the piezoelectric element PZ; a first inspection signal generating circuit 340 that receives a residual vibration signal resulting from the vibration remaining in the ejection unit D after the piezoelectric element PZ is driven and generates a pseudo residual vibration signal corresponding to the residual vibration signal; and a second inspection signal generating circuit 350 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. Furthermore, in this embodiment, the head unit 3 further includes a second selection circuit 360 that switches between supplying the pseudo residual vibration signal or the detected residual vibration signal to the inspection unit 6 that determines the state of the ejection unit D. Note that in this embodiment, for example, the detection signal Vout is input as the 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. Alternatively, for example, the detection signal Vout is input as the 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.

[0236] Thus, in this embodiment, the pseudo residual vibration signal generated by the first inspection signal generation circuit 340 or the detected residual vibration signal generated by the second inspection signal generation circuit 350 is used as a signal for determining the state of the ejector D. For example, in this embodiment, by using a pseudo residual vibration signal generated based on a residual vibration signal having a period less than one to determine the state of the ejector D, the time allocated for detecting the residual vibration signal can be shortened compared to when using the detected residual vibration signal to determine the state of the ejector D. Therefore, in this embodiment, when determining the state of the ejector D, by using the pseudo residual vibration signal generated by the first inspection signal generation circuit 340 to determine the state of the ejector D, it is possible to suppress the length of the unit period TU, the cycle for driving the ejector D, from increasing. In other words, in this embodiment, by using the pseudo residual vibration signal generated by the first inspection signal generation circuit 340 to determine the state of the ejector D, the length of the unit period TU used for determining the state of the ejector D can be shortened. Furthermore, in this embodiment, the state of the ejector D can be determined using the detected residual vibration signal after removing frequency components other than a predetermined frequency component from the residual vibration signal, as needed. That is, in the present embodiment, it is possible to switch appropriately whether to determine the state of the discharge portion D using the pseudo residual vibration signal or to determine the state of the discharge portion D using the detected residual vibration signal.

[0237] In addition, in this embodiment, the head unit 3 further includes a first switching circuit 335 and a second switching circuit 337. The first switching circuit 335 switches whether the residual vibration signal is input to the first inspection signal generating circuit 340, and the second switching circuit 337 switches whether the residual vibration signal is input to the second inspection signal generating circuit 350. Thus, in this embodiment, it is possible to easily switch between whether the first inspection signal generating circuit 340 or the second inspection signal generating circuit 350 generates the signal used to determine the state of the ejection unit D. In other words, in this embodiment, it is possible to easily switch between using the pseudo residual vibration signal or the detected residual vibration signal to determine the state of the ejection unit D. Furthermore, in this embodiment, it is possible to suppress unnecessary operation of circuits in the first inspection signal generating circuit 340 and the second inspection signal generating circuit 350 that do not generate the signal used to determine the state of the ejection unit D. Consequently, in this embodiment, it is possible to suppress the generation of noise and the like in the signal used to determine the state of the ejection unit D.

[0238] Furthermore, in this embodiment, the second selection circuit 360 exclusively switches, based on the selection signal SEL, between supplying the pseudo residual vibration signal and supplying the detection residual vibration signal to the inspection unit 6. Thus, in this embodiment, it is possible to suppress the supply of signals, either the pseudo residual vibration signal or the detection residual vibration signal, that are not used for determining the state of the discharge unit D to the inspection unit 6 while the inspection unit 6 is determining the state of the discharge unit D. Consequently, in this embodiment, it is possible to suppress the generation of noise, etc., in the inspection unit 6 while the inspection unit 6 is determining the state of the discharge unit D.

[0239] Furthermore, in this embodiment, first inspection signal generating circuit 340 includes a low-pass filter circuit 343 and a first filter circuit 344. The residual vibration signal is input to first filter circuit 344 via low-pass filter circuit 343, and first filter circuit 344 generates a pseudo residual vibration signal. Thus, in this embodiment, first filter circuit 344 can generate a pseudo residual vibration signal based on the residual vibration signal from which noise and other factors have been removed. As a result, in this embodiment, distortion of the pseudo residual vibration signal can be suppressed.

[0240] Furthermore, in this embodiment, the inspection unit 6 determines the viscosity of the ink within the ejection portion D based on the pseudo residual vibration signal. In other words, the pseudo residual vibration signal is used to determine the viscosity of the ink within the ejection portion D. Therefore, in this embodiment, it is possible to suppress an increase in the time required to determine the viscosity of the ink within the ejection portion D. For example, in this embodiment, it is possible to shorten the time required to determine the viscosity of the ink within multiple ejection portions D.

[0241] Furthermore, in this embodiment, the inspection unit 6 determines multiple abnormal conditions, including the viscosity of the ink within the ejection portion D, based on the detected residual vibration signal. Specifically, the detected residual vibration signal is used to determine multiple abnormal conditions, including the viscosity of the ink within the ejection portion D. Thus, in this embodiment, by using the detected residual vibration signal as a signal for determining the state of the ejection portion D, it is possible to determine multiple abnormal conditions, including the viscosity of the ink.

[0242] 2. Modification

[0243] Each of the above methods can be modified in many ways. The following examples illustrate specific modification methods. Two or more methods arbitrarily selected from the following examples can be appropriately combined within the scope of non-contradiction. It should be noted that in the modification examples shown below, for elements with the same effects and functions as those in the implementation method, the reference numerals in the above description are used, and the detailed descriptions of each are appropriately omitted.

[0244] First Modification

[0245] In the above embodiment, some elements of the first filter circuit 344 may also serve as the second filter circuit 354 .

[0246] Figure 18 FIG. 1 is a block diagram showing an example of the configuration of the detection circuit 33A according to the first modification. Figures 1 to 17 The same elements as those described in are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0247] In addition to replacing Figure 1 The detection circuit 33 shown has Figure 18 In addition to the detection circuit 33A shown in FIG, the inkjet printer 1 according to this modification is Figure 1 The detection circuit 33A includes, 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 .

[0248] 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 connected to Figure 7 The first gain adjustment circuit 342, low-pass filter circuit 343, and second gain adjustment circuit 352 are identical. However, the output signal of the low-pass filter circuit 343, i.e., the first filtered input signal INbpf1, and the output signal of the second gain adjustment circuit 352, i.e., the second filtered input signal INbpf2, are input to the third filter circuit 370.

[0249] The third filter circuit 370 is, for example, switched based on the selection signal SEL. Figure 9 The first filter circuit 344 shown functions as Figure 10 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. It should be noted that in the third filter circuit 370, some of the elements of the first filter circuit 344 and the elements of the second filter circuit 354 are shared by the first filter circuit 344 and the second filter circuit 354. Details will be discussed later. Figure 19 Narrating in.

[0250] The output signal of the third filter circuit 370 is supplied to the buffer circuit 372 as the filter output signal Obpf.

[0251] The buffer circuit 372 is a buffer that converts the impedance and outputs the low-impedance test signal VD. Figure 9The first buffer circuit 346 shown is similarly configured as a voltage follower using the operational amplifier OP43. Thus, the filtered output signal Obpf supplied to the buffer circuit 372 is output from the buffer circuit 372 as a low-impedance inspection signal VD.

[0252] Next, refer to Figure 19 The outline of the third filter circuit 370 will be described.

[0253] Figure 19 : is a circuit diagram showing an example of the configuration of the third filter circuit 370 according to the first modification. Figures 1 to 18 The same elements as those described in are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0254] Figure 19 The first filter circuit 344A shown corresponds to Figure 9 The first filtering circuit 344 shown, Figure 19 The second filter circuit 354A shown corresponds to Figure 10 The second filter circuit 354 is shown. Figure 19 As shown, in the third filter circuit 370, the first filter circuit 344A and the second filter circuit 354A share the operational amplifier OP42 and the resistor R42. When the third filter circuit 370 functions as the second filter circuit 354A, the operational amplifier OP42 and the resistor R42 correspond to Figure 10 The operational amplifier OP51 and the resistor element R52 are shown.

[0255] 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 .

[0256] One end of resistor R41 is connected to the output terminal of operational amplifier OP41 of low-pass filter circuit 343, and the other end of resistor R41 is connected to node N41. One end of capacitor C41 is connected to node N41 via switch SW1, and the other end of capacitor C41 is connected to the inverting input terminal of operational amplifier OP42. One end of resistor R42 is connected to the inverting input terminal of operational amplifier OP42, and the other end of resistor R42 is connected to the output terminal of operational amplifier OP42. One end of resistor R43 is connected to node N41, and the other end of resistor R43 is connected to a wiring line supplied with a first reference potential Vref1. One end of capacitor C42 is connected to node N41 via switch SW2, and the other end of capacitor C42 is connected to the output terminal of operational amplifier OP42. Furthermore, the non-inverting input terminal of operational amplifier OP42 is connected to a wiring line supplied with the first reference potential Vref1.

[0257] Furthermore, one end of the resistor R51 is connected to the output terminal of the operational amplifier OP50 of the second gain adjustment circuit 352. The other end of the resistor R51 is connected to one end of a capacitor C51. The other end of the capacitor C51 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.

[0258] The inverter INV2 outputs an inverted signal of the selection signal SEL supplied from the connection state designation circuit 310 to the switch SW3 .

[0259] The switch SW1 is turned on when the selection signal SEL is at a high level, electrically connecting the capacitor C41 to the node N41. It is turned off when the selection signal SEL is at a low level, 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 to the node N41. It is turned off when the selection signal SEL is at a low level, disconnecting the capacitor C42 from the node N41. The switch SW3 is turned on when the selection signal SEL is at a high level, electrically connecting the capacitor C52 to the inverting input terminal of the operational amplifier OP42. It is turned off when the selection signal SEL is at a low level, disconnecting the capacitor C52 from the inverting input terminal of the operational amplifier OP42.

[0260] For example, when the selection signal SEL is at a high level, 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 element R41, the switch SW1, and the capacitor C41. Then, the output signal of the operational amplifier OP42 is fed back to the inverting input terminal of the operational amplifier OP42 via the resistor element R42. In addition, the output signal of the operational amplifier OP42 is 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 at a high level, the third filter circuit 370 acts as a Figure 9 The first filter circuit 344 shown functions as a similar multiple feedback type bandpass filter.

[0261] 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 the resistor element R51 and the capacitor C51. Then, the output signal of the operational amplifier OP42 is fed back to the inverting input terminal of the operational amplifier OP42 via the resistor element R42. Furthermore, the output signal of the operational amplifier OP42 is fed back to the inverting input terminal of the operational amplifier OP42 via the capacitor C52 and the switch SW3. Thus, when the selection signal SEL is at a low level, the third filter circuit 370 functions as a Figure 10 The second filter circuit 354 shown functions as a similar bandpass filter. Note that the switch group including the switches SW1, SW2, and SW3 is another example of a "switching unit."

[0262] As described above, this modification also achieves the same effects as the above-described embodiment. Furthermore, in this modification, operational amplifier OP42 and resistor R42 are shared between first filter circuit 344A and second filter circuit 354A. Consequently, in this modification, the circuit scale of detection circuit 33A can be reduced compared to detection circuit 33.

[0263] Second Modification

[0264] In the above embodiment, the first buffer circuit 346 can be omitted from the first inspection signal generating circuit 340, and the second buffer circuit 356 can be omitted from the second inspection signal generating circuit 350, with the buffer circuit 372 being provided after 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 can be omitted, with a gain adjustment circuit and buffer circuit 372 similar to the first gain adjustment circuit 342 provided after the second selection circuit 360. Furthermore, in the above variation, the first gain adjustment circuit 342 and the second gain adjustment circuit 352 can be omitted, with a gain adjustment circuit similar to the first gain adjustment circuit 342 provided between the second selection circuit 360 and the buffer circuit 372.

[0265] As described above, this modification also achieves the same effects as those of the above-described embodiment and modification. In addition, in this modification, since the first buffer circuit 346 and the like are omitted, the circuit scale of the detection circuit 33 or 33A can be reduced.

[0266] Third Modification

[0267] In the above embodiment and modification, the first selection circuit 330 may be omitted. In this modification, in addition to the effects obtained by the first selection circuit 330, the same effects as those of the above embodiment and modification can be obtained.

[0268] Fourth Modification

[0269] In the above-described embodiment and modified examples, the number of times the state of the ejection unit D is determined in the first mode may be greater than the number of times the state of the ejection unit D is determined in the second mode during a single printing operation. This modified example also achieves the same effects as the above-described embodiment and modified examples. It should be noted that because the time allocated for detecting the residual vibration of the ejection unit D can be shortened in the first mode, even if the number of times the state of the ejection unit D is determined in the first mode is greater, printing efficiency will not be significantly reduced.

[0270] Fifth Modification

[0271] While the above-described embodiment and modified examples illustrate the case where the first inspection signal Vd1 representing a pseudo residual vibration signal is generated based on residual vibration of the ejection portion D that is greater than one-quarter of a period and less than one period, the present invention is not limited to this embodiment. For example, the first inspection signal Vd1 may be generated based on residual vibration of the ejection portion D that is one period, and the second inspection signal Vd2 may be generated based on residual vibration of the ejection portion D that is longer than one period. This modified example also achieves the same effects as the above-described embodiment and modified examples.

[0272] Sixth Modification

[0273] While the above-described embodiment and variations illustrate a case where the piezoelectric element PZ is displaced in the Z1 direction by changing the potential of a single drive signal Vin[m] from a low potential to a high potential, the present invention is not limited to this embodiment. For example, a piezoelectric element PZ can be displaced in the Z1 direction by changing the potential of a single drive signal Vin[m] from a high potential to a low potential. In this case, for example, the potential of the drive signal COM changes from a low potential to a high potential in the portion corresponding to the expansion element, and changes from a high potential to a low potential in the portion corresponding to the contraction element. This variation also achieves the same effects as the above-described embodiment and variations.

[0274] Seventh Modification

[0275] While the above-described embodiment and modified examples illustrate a case where each head unit 3 has one nozzle row NL, the present invention is not limited to this embodiment. For example, each head unit 3 may have multiple nozzle rows NL. This modified example also achieves the same effects as the above-described embodiment and modified examples.

[0276] Eighth Modification

[0277] While the above embodiments and variations illustrate an inkjet printer 1 having four head units 3, the present invention is not limited to this embodiment. For example, the inkjet printer 1 may have one or more and three or fewer head units 3, or five or more head units 3. Alternatively, the inkjet printer 1 may have one or more and three or fewer head units 3A, or five or more head units 3A.

[0278] Ninth Modification

[0279] While the above-described embodiment and modified examples illustrate a case where first filter circuit 344 is a multiple-feedback bandpass filter, the present invention is not limited to this embodiment. For example, a filter circuit with a variable group delay characteristic, such as a Butterworth or Chebyshev filter, may also be used as first filter circuit 344. This modified example also achieves the same effects as the above-described embodiment and modified examples.

[0280] 3. Appendix

[0281] From the above-exemplified embodiments, the following configurations can be understood, for example.

[0282] The liquid ejection device involved in method 1 as a preferred method includes: a drive signal generating unit that generates a drive signal; a ejection unit including a nozzle, a piezoelectric element and a pressure chamber, the piezoelectric element is driven by the drive signal, and the pressure chamber ejects liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generating unit, to which a residual vibration signal is input, the first signal generating unit generates a pseudo residual vibration signal corresponding to the residual vibration signal, the residual vibration signal being generated by the vibration remaining in the ejection unit after driving the piezoelectric element; a second signal generating unit, to which the residual vibration signal is input, the second signal generating unit generates a detection residual vibration signal, the detection residual vibration signal being a signal obtained by removing frequency components other than a specified frequency component from the residual vibration signal; and a determination unit, to which one of the pseudo residual vibration signal and the detection residual vibration signal is selectively input, and the determination unit determines the state of the ejection unit based on the input signal.

[0283] According to the first embodiment, the cycle of driving the ejection unit, i.e., the length of the unit period, can be prevented from increasing. In addition, according to the first embodiment, it is possible to appropriately switch between using the pseudo residual vibration signal or the detected residual vibration signal to determine the state of the ejection unit.

[0284] The liquid ejection device involved in method 2 as a specific example of method 1 further includes: a first switching unit that switches whether the residual vibration signal is input to the first signal generating unit; and a second switching unit that switches whether the residual vibration signal is input to the second signal generating unit.

[0285] According to aspect 2, it is possible to easily switch whether the first signal generating unit generates the signal for determining the state of the ejection unit or the second signal generating unit generates the signal for determining the state of the ejection unit.

[0286] The liquid ejection device according to aspect 3 as a specific example of aspect 1 or aspect 2 further includes a switching unit that exclusively switches, based on a switching signal, whether to supply the pseudo residual vibration signal to the determination unit or to supply the detected residual vibration signal to the determination unit.

[0287] According to the third embodiment, the pseudo residual vibration signal and the signal not used for determining the state of the ejection unit in the residual vibration signal can be suppressed from being supplied to the determination unit while the determination unit is determining the state of the ejection unit. Therefore, according to the third embodiment, the generation of noise and the like in the determination unit during the determination unit's determination of the state of the ejection unit can be suppressed.

[0288] In the liquid ejection device involved in method 4 which is a specific example of any one of methods 1 to 3, the first signal generating unit includes: a low-pass filter; and a filter circuit, the residual vibration signal is input into the filter circuit via the low-pass filter, and the filter circuit generates the pseudo residual vibration signal.

[0289] According to aspect 4, the filter circuit can generate a pseudo residual vibration signal based on the residual vibration signal after noise etc. As a result, according to aspect 4, it is possible to suppress the pseudo residual vibration signal from being distorted.

[0290] 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 thickening state of the liquid in the ejection unit based on the pseudo residual vibration signal.

[0291] According to aspect 5, it is possible to suppress an increase in the time required to determine the thickening state of the liquid in the discharge portion.

[0292] In the liquid ejection device according to aspect 6 which is a specific example of any one of aspects 1 to 5, the determination unit determines a plurality of abnormal states including a thickening state of the liquid in the ejection unit based on the detected residual vibration signal.

[0293] According to aspect 6, by using the detected residual vibration signal as a signal for determining the state of the ejection unit, it is possible to determine a plurality of abnormal states including the viscosity state of the ink.

[0294] In addition, the liquid ejection head involved in method 7 as a preferred method comprises: a ejection part, including a nozzle, a piezoelectric element and a pressure chamber, the piezoelectric element is driven by a driving signal, and the pressure chamber ejects liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generating part, to which a residual vibration signal is input, the first signal generating part generates a pseudo residual vibration signal corresponding to the residual vibration signal, and the residual vibration signal is generated by the vibration remaining in the ejection part after driving the piezoelectric element; a second signal generating part, to which the residual vibration signal is input, the second signal generating part generates a detection residual vibration signal, and the detection residual vibration signal is a signal obtained by removing frequency components other than a specified frequency component from the residual vibration signal; and a switching part, which switches whether to supply the pseudo residual vibration signal to a determination part that determines the state of the ejection part, or to supply the detection residual vibration signal to the determination part.

[0295] According to the seventh aspect, the same effects as those of the first aspect can be obtained.

[0296] The liquid ejection head according to aspect 8 as a specific example of aspect 7 further includes: a first switching unit that switches whether the residual vibration signal is input to the first signal generating unit; and a second switching unit that switches whether the residual vibration signal is input to the second signal generating unit.

[0297] According to the eighth aspect, the same effects as those of the second aspect can be obtained.

[0298] In the liquid ejection head according to aspect 9 as a specific example of aspect 7 or aspect 8, the switching unit exclusively switches whether to supply the pseudo residual vibration signal or the detected residual vibration signal to the determination unit based on a switching signal.

[0299] According to the ninth embodiment, the same effects as those of the third embodiment can be obtained.

[0300] In the liquid ejection head involved in method 10 which is a specific example of any one of methods 7 to 9, the first signal generating unit includes: a low-pass filter; and a filter circuit, the residual vibration signal is input into the filter circuit via the low-pass filter, and the filter circuit generates the pseudo residual vibration signal.

[0301] According to the tenth aspect, the same effects as those of the fourth aspect can be obtained.

[0302] 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 a thickening state of the liquid in the ejection portion.

[0303] According to the eleventh aspect, the same effects as those of the fifth aspect can be obtained.

[0304] In the 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 a plurality of abnormal states including a thickening state of the liquid in the ejection portion.

[0305] According to the twelfth embodiment, the same effects as those of the sixth embodiment can be obtained.

Claims

1. A liquid ejection device, characterized in that: have: A driving signal generating unit, generating a driving signal; a discharge portion including a nozzle, a piezoelectric element, and a pressure chamber, wherein the piezoelectric element is driven by the drive signal, and the pressure chamber discharges liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generating unit to which a residual vibration signal is input, the first signal generating unit generating a pseudo residual vibration signal corresponding to the residual vibration signal, the residual vibration signal being generated by vibration remaining in the ejection unit after the piezoelectric element is driven; a second signal generating unit, into which the residual vibration signal is input, and the second signal generating unit generates a detected residual vibration signal, the detected residual vibration signal being a signal obtained by removing frequency components other than a predetermined frequency component from the residual vibration signal; as well as A determination unit is configured to selectively receive one of the pseudo residual vibration signal and the detected residual vibration signal, and to determine the state of the ejection unit based on the input signal.

2. The liquid ejection device according to claim 1, wherein The liquid ejection device further comprises: a first switching unit configured to switch whether to input the residual vibration signal to the first signal generating unit; and The second switching unit switches whether to input the residual vibration signal to the second signal generating unit.

3. The liquid ejection device according to claim 1, wherein The liquid ejection device further includes a switching unit that exclusively switches, based on a switching signal, whether to supply the pseudo residual vibration signal to the determination unit or to supply the detected residual vibration signal to the determination unit.

4. The liquid ejection device according to any one of claims 1 to 3, wherein: The first signal generating unit includes: low-pass filter; and A filter circuit, wherein the residual vibration signal is input into the filter circuit via the low-pass filter, and the filter circuit generates the pseudo residual vibration signal.

5. The liquid ejection device according to any one of claims 1 to 3, wherein: The determination unit determines a thickening state of the liquid in the discharge unit based on the pseudo residual vibration signal.

6. The liquid ejection device according to any one of claims 1 to 3, wherein: The determination unit determines a plurality of abnormal states including a thickening state of the liquid in the discharge unit based on the detected residual vibration signal.

7. A liquid ejection head, characterized in that: have: a discharge portion including a nozzle, a piezoelectric element, and a pressure chamber, wherein the piezoelectric element is driven by a drive signal, and the pressure chamber discharges liquid from the nozzle in response to the driving of the piezoelectric element; a first signal generating unit to which a residual vibration signal is input, the first signal generating unit generating a pseudo residual vibration signal corresponding to the residual vibration signal, the residual vibration signal being generated by vibration remaining in the ejection unit after the piezoelectric element is driven; a second signal generating unit to which the residual vibration signal is input, and the second signal generating unit generates a detected residual vibration signal, the detected residual vibration signal being a signal obtained by removing frequency components other than a predetermined frequency component from the residual vibration signal; and The switching unit switches whether to supply the pseudo residual vibration signal to a determination unit that determines a state of the ejection unit or to supply the detected residual vibration signal to the determination unit.

8. The liquid ejection head according to claim 7, wherein The liquid ejection head further comprises: a first switching unit configured to switch whether to input the residual vibration signal to the first signal generating unit; and The second switching unit switches whether to input the residual vibration signal to the second signal generating unit.

9. The liquid ejection head according to claim 7, wherein The switching section exclusively switches, based on a switching signal, whether to supply the pseudo residual vibration signal to the determination section or to supply the detected residual vibration signal to the determination section.

10. The liquid ejection head according to any one of claims 7 to 9, wherein: The first signal generating unit includes: low-pass filter; and A filter circuit, wherein the residual vibration signal is input into the filter circuit via the low-pass filter, and the filter circuit generates the pseudo residual vibration signal.

11. The liquid ejection head according to any one of claims 7 to 9, wherein: The pseudo residual vibration signal is used to determine a thickening state of the liquid in the ejection portion.

12. The liquid ejection head according to any one of claims 7 to 9, wherein: The detected residual vibration signal is used to determine a plurality of abnormal conditions including a thickening condition of the liquid in the ejection portion.

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