Liquid discharge apparatus and liquid discharge head

Abstract

The invention relates to a liquid ejecting apparatus and a liquid ejecting head. A potential of a piezoelectric element is accurately detected. A liquid ejecting apparatus includes: an ejecting portion including a piezoelectric element driven by a drive signal; a first wiring to which a first driving signal among the driving signals is supplied; a second wiring electrically connected to an element electrode of the piezoelectric element; and a detection circuit that detects a potential of the element electrode that varies in accordance with vibration remaining on the piezoelectric element after driving of the piezoelectric element, the detection circuit being provided with: a first amplifier that has a first input terminal, a second input terminal, and a first output terminal; a first resistor electrically connecting a first node electrically connected to the first input terminal and a second node electrically connected to the first output terminal; and a second resistor electrically connecting the first node and a second wiring, the first wiring being electrically connected to the second input terminal.

Description

Technical Field

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

[0002] Liquid ejection devices such as inkjet printers use a driving signal to drive a piezoelectric element provided in an ejection portion of a liquid ejection head so that liquid such as ink filled in a pressure chamber provided in the ejection portion is ejected from a nozzle to form an image on a medium. However, in a liquid ejection device, sometimes an abnormal ejection occurs in which the liquid cannot be ejected normally from the ejection portion. Therefore, a technology for checking the ejection state in the ejection portion has been proposed. For example, Patent Document 1 discloses the following technology: first, the piezoelectric element is driven by turning on a driving switch, and the driving switch switches the conduction and non-conduction between the driving signal supply wiring for supplying the driving signal and the piezoelectric element; second, the detection circuit detects the potential of the piezoelectric element by turning on a detection switch, and the detection switch switches the conduction and non-conduction between the detection circuit for detecting the potential of the piezoelectric element and the piezoelectric element; third, the ejection state in the ejection portion is checked based on the detection result of the detection circuit.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2015-039856

[0004] However, according to the conventional technology, when the detection circuit detects the potential of the piezoelectric element, the switching noise of the detection switch overlaps with the signal indicating the potential of the piezoelectric element due to the detection switch being turned on. Therefore, according to the conventional technology, there is a problem that the detection circuit cannot accurately detect the potential of the piezoelectric element. Summary of the invention

[0005] In order to solve the above technical problems, the liquid ejection device according to the present invention is characterized in that it comprises: an ejection portion, comprising a piezoelectric element driven by a driving signal, a pressure chamber filled with liquid and whose volume changes according to the driving of the piezoelectric element, and a nozzle that ejects the liquid in the pressure chamber according to the change in the volume of the pressure chamber; a first wiring to which a first driving signal in the driving signal is supplied; a second wiring electrically connected to an element electrode of the piezoelectric element; a detection circuit that detects the potential of the element electrode that changes according to the vibration remaining in the piezoelectric element after the driving of the piezoelectric element; and an inspection device that inspects the ejection state of the liquid in the ejection portion based on the detection result of the detection circuit, the detection circuit comprising a first amplifier circuit, the first amplifier circuit comprising: a first amplifier having a first input terminal, a second input terminal, and a first output terminal that outputs a signal based on an input to the first input terminal and an input to the second input terminal; a first resistor that electrically connects a first node electrically connected to the first input terminal and a second node electrically connected to the first output terminal; and a second resistor that electrically connects the first node and the second wiring, the first wiring being electrically connected to the second input terminal.

[0006] In addition, the liquid ejection head according to the present invention is characterized in that it comprises: a piezoelectric element driven by a driving signal; a pressure chamber filled with liquid and whose volume changes according to the driving of the piezoelectric element; a nozzle that ejects the liquid in the pressure chamber according to the change in the volume of the pressure chamber; a first wiring, from which a first driving signal in the driving signal reaches the first wiring; a second wiring electrically connected to an element electrode possessed by the piezoelectric element; and a detection circuit that detects the potential of the element electrode that changes according to the vibration remaining in the piezoelectric element after the driving of the piezoelectric element, the detection circuit comprising a first amplifier circuit, the first amplifier circuit comprising: a first amplifier having a first input terminal, a second input terminal, and a first output terminal that outputs a signal based on an input to the first input terminal and an input to the second input terminal; a first resistor that electrically connects a first node electrically connected to the first input terminal and a second node electrically connected to the first output terminal; and a second resistor that electrically connects the first node and the second wiring, the first wiring being electrically connected to the second input terminal. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0010] Figure 4 It is a block diagram showing an example of the configuration of the head unit 3 .

[0011] Figure 5 It is a timing chart for explaining an example of a signal supplied to the head unit 3 .

[0012] Figure 6 This is an explanatory diagram for explaining an example of the operation of the connection state specifying circuit 34.

[0013] Figure 7 SK[m] is a timing chart for explaining an example of the detection signal SK[m].

[0014] Figure 8 It is an explanatory diagram for explaining an example of the operation of the inspection unit 5 .

[0015] Fig. 9 2 is a block diagram showing an example of the configuration of the detection circuit 33 .

[0016] Fig.10 It is an explanatory diagram showing an example of the operation of the head unit 3 .

[0017] Fig.11 It is an explanatory diagram showing an example of the operation of the head unit 3 .

[0018] Fig.12 It is an explanatory diagram showing an example of the operation of the head unit 3 .

[0019] Description of Reference Numerals

[0020] 1: inkjet printer; 2: control unit; 3: head unit; 4: drive signal generating unit; 5: inspection unit; 6: storage unit; 7: conveying unit; 31: supply circuit; 32: recording head; 33: detection circuit; 331: amplifier circuit; 332: subtraction circuit; 333: amplifier circuit. DETAILED DESCRIPTION

[0021] The following is a description of the method for implementing the present invention with reference to the accompanying drawings. However, in each figure, the size and scale of each part are appropriately different from the actual one. In addition, the embodiments described below are suitable specific examples of the present invention, so various technically preferred limitations are added. However, as long as there is no special description in the following description to limit the meaning of the present invention, the scope of the present invention is not limited to these methods.

[0022] A. Implementation Method

[0023] In the present embodiment, an inkjet printer that ejects ink to form an image on recording paper PP is taken as an example and the liquid ejecting device is described.

[0024] 1. Overview of inkjet printers

[0025] Refer to the following Figures 1 to 3 An example of the configuration of the inkjet printer 1 according to the present embodiment will be described.

[0026] Figure 1 1 is a functional block diagram showing an example of the configuration of the inkjet printer 1 .

[0027] like Figure 1 As shown, print data Img representing an image to be formed by the inkjet printer 1 is supplied from a host computer such as a personal computer or a digital camera to the inkjet printer 1. The inkjet printer 1 executes a print process to form an image represented by the print data Img supplied from the host computer on recording paper PP.

[0028] like Figure 1 As shown, the inkjet printer 1 includes a control unit 2 for controlling each unit of the inkjet printer 1, a head unit 3 provided with a discharge unit D for discharging ink, a drive signal generating unit 4 for generating a drive signal Com for driving the discharge unit D, an inspection unit 5 for inspecting the discharge state of the ink in the discharge unit D, a storage unit 6 for storing various information, and a conveying unit 7 for changing the relative position of the recording paper PP and the head unit 3. It should be noted that ink is an example of "liquid", the inkjet printer 1 is an example of "liquid discharge device", the head unit 3 is an example of "liquid discharge head", and the inspection unit 5 is an example of "inspection device".

[0029] In this embodiment, it is assumed that the inkjet printer 1 has one or more head units 3, one or more drive signal generating units 4 corresponding to the one or more head units 3, and one or more inspection units 5 corresponding to the one or more head units 3. Specifically, in this embodiment, the inkjet printer 1 has four head units 3, four drive signal generating units 4 corresponding to the four head units 3, and four inspection units 5 corresponding to the four head units 3. However, in the following, for the sake of convenience, as Figure 1 As shown, the description will focus on one head unit 3 among the four head units 3, one of the four drive signal generating units 4 provided corresponding to the one head unit 3, and one of the four inspection units 5 provided corresponding to the one head unit 3.

[0030] The control unit 2 is configured to include one or more CPUs (Central Processing Units). However, the control unit 2 may also be a unit having a programmable logic device such as an FPGA (field-programmable gate array) instead of a CPU, or the control unit 2 may be a unit having a programmable logic device such as an FPGA in addition to a CPU. In addition, the control unit 2 includes a memory. The memory is configured to include a volatile memory such as a RAM (Random Access Memory) and one or both of a non-volatile memory such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory) or a PROM (Programmable ROM).

[0031] As will be described in detail later, the control unit 2 generates signals such as the designation signal SI and the waveform designation signal dCom for controlling the operation of each unit of the inkjet printer 1 .

[0032] Here, the waveform designation signal dCom is a digital signal that specifies the waveform of the drive signal Com. In the present embodiment, it is assumed that the waveform designation signal dCom includes a printing waveform designation signal dCom-A and an inspection waveform designation signal dCom-N.

[0033] In addition, the drive signal Com refers to an analog signal for driving the ejection unit D. In the present embodiment, it is assumed that the drive signal Com includes a printing drive signal Com-A and an inspection drive signal Com-N. It should be noted that, in the present embodiment, the inspection drive signal Com-N is an example of a "first drive signal", and the printing drive signal Com-A is an example of a "second drive signal".

[0034] The drive signal generating unit 4 generates the printing drive signal Com-A having the waveform specified by the printing waveform specifying signal dCom-A based on the printing waveform specifying signal dCom-A. In addition, the drive signal generating unit 4 generates the inspection drive signal Com-N having the waveform specified by the inspection waveform specifying signal dCom-N based on the inspection waveform specifying signal dCom-N.

[0035] The designation signal SI is a digital signal that designates the type of operation of the discharge unit D. Specifically, the designation signal SI designates whether the drive signal Com is supplied to the discharge unit D, thereby designating the type of operation of the discharge unit D, such as whether the discharge unit D discharges ink.

[0036] When executing the printing process, the control unit 2 generates a signal such as a designation signal SI for controlling the head unit 3 based on the printing data Img. In addition, the control unit 2 generates a signal such as a printing waveform designation signal dCom-A for controlling the drive signal generating unit 4 when executing the printing process. In addition, the control unit 2 generates a signal for controlling the conveying unit 7 when executing the printing process. Thus, during the printing process, the control unit 2 controls the conveying unit 7 to change the relative position between the recording paper PP and the head unit 3, adjusts the presence or absence of ink ejection from the ejection unit D and the timing of ink ejection, and controls each part of the inkjet printer 1 to form an image corresponding to the printing data Img on the recording paper PP.

[0037] like Figure 1 As shown, the head unit 3 includes a supply circuit 31 , a recording head 32 , and a detection circuit 33 .

[0038] The recording head 32 has M ejection parts D. Here, the value M is a natural number satisfying "M ≥ 1". It should be noted that, hereinafter, the m-th ejection part D among the M ejection parts D provided in the recording head 32 is sometimes referred to as ejection part D[m]. Here, the variable m is a natural number satisfying "1 ≤ m ≤ M". In addition, hereinafter, when a component or signal of the inkjet printer 1 corresponds to an ejection part D[m] among the M ejection parts D, a footnote [m] may be added to the reference numeral used to represent the component or signal.

[0039] The supply circuit 31 switches whether to supply the drive signal Com to the ejection unit D[m] based on the designation signal SI. Hereinafter, the drive signal Com supplied to the ejection unit D[m] among the drive signals Com may be referred to as a supply drive signal Vin[m].

[0040] In addition, the supply circuit 31 switches whether to supply the detection potential signal VX[m] to the detection circuit 33 based on the designated signal SI. Here, the detection potential signal VX[m] refers to a signal indicating the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the ejection part D[m]. In the following, when the detection potential signal VX[m] is supplied from the ejection part D[m] to the detection circuit 33, the ejection part D[m] is sometimes referred to as the inspection object ejection part DS. It should be noted that regarding the piezoelectric element PZ[m] and the upper electrode Zu[m], Figure 3 To be described later.

[0041] The detection circuit 33 generates a detection signal SK[m] based on the detection potential signal VX[m] supplied from the discharge portion D[m] serving as the inspection target discharge portion DS via the supply circuit 31 .

[0042] The inspection unit 5 checks whether the ink ejection state in the inspection object ejection unit DS is normal based on the detection signal SK[m]. In other words, the inspection unit 5 checks whether there is no ejection abnormality in the inspection object ejection unit DS based on the detection signal SK[m]. Then, the inspection unit 5 generates the inspection result information SH[m] indicating the result of the inspection. Here, the inspection result information SH[m] refers to information indicating whether an ejection abnormality has occurred in the ejection unit D[m] selected as the inspection object ejection unit DS. In addition, the ejection abnormality refers to a general term for the state in which the nozzle N[m] of the ejection unit D[m] cannot eject the ink normally. For example, the ejection abnormality includes a state in which the ejection unit D[m] cannot eject the ink, a state in which the ejection unit D[m] ejects an amount of ink different from the ejection amount of the ink specified by the drive signal Com, and a state in which the ejection unit D[m] ejects the ink at a speed different from the ejection speed of the ink specified by the drive signal Com.

[0043] Hereinafter, the process of checking the ink ejection state of the ejection unit D[m] by driving the ejection unit D[m] as the ejection unit DS to be checked is referred to as ejection state checking process. Also, the process of driving the ejection unit D[m] as the ejection unit DS to be checked in the ejection state checking process is referred to as check target driving process.

[0044] In addition, in the discharge state inspection process, the process of detecting the detection potential signal VX[m] from the discharge portion D[m] driven as the inspection target discharge portion DS is referred to as the residual vibration detection process.

[0045] When the inspection target drive process is executed, the control unit 2 generates a signal such as the designation signal SI for controlling the head unit 3. In addition, when the inspection target drive process is executed, the control unit 2 generates a signal such as the inspection waveform designation signal dCom-N for controlling the drive signal generation unit 4. Thus, the control unit 2 drives the discharge unit D[m] as the inspection target discharge unit DS in the inspection target drive process.

[0046] When the residual vibration detection process is executed, the control unit 2 controls the head unit 3 by generating a designated signal SI to supply the detection circuit 33 with a detection potential signal VX[m] corresponding to the ejection unit D[m] driven as the inspection target ejection unit DS. Then, when the residual vibration detection process is executed, the detection circuit 33 generates a detection signal SK[m] based on the detection potential signal VX[m] detected from the ejection unit D[m] driven as the inspection target ejection unit DS.

[0047] Figure 2 This is a perspective view showing an example of a schematic internal structure of the inkjet printer 1 .

[0048] like Figure 2 As shown, in this embodiment, it is assumed that the inkjet printer 1 is a serial printer. Specifically, when the inkjet printer 1 performs printing processing, the inkjet printer 1 ejects ink from the ejection portion D[m] while conveying the recording paper PP in the X1 direction and moving the head unit 3 back and forth in the Y1 direction intersecting the X1 direction and the Y2 direction which is the opposite direction of the Y1 direction, thereby forming dots Dt corresponding to the print data Img on the recording paper PP.

[0049] Hereinafter, the X1 direction and the X2 direction as its opposite direction are collectively referred to as the "X-axis direction", the Y1 direction intersecting the X-axis direction and the Y2 direction as its opposite direction are collectively referred to as the "Y-axis direction", and the Z1 direction intersecting the X-axis direction and the Y-axis direction and the Z2 direction as its opposite direction are collectively referred to as the "Z-axis direction". In the present embodiment, as an example, it is assumed that the X-axis direction, the Y-axis direction and the Z-axis direction are orthogonal to each other for illustration. However, the present invention is not limited to such a form. The X-axis direction, the Y-axis direction and the Z-axis direction only need to intersect each other. It should be noted that in the present embodiment, the Z1 direction is set as the direction in which ink is ejected from the ejection portion D[m].

[0050] like Figure 2 As shown, the inkjet printer 1 according to the present embodiment includes a housing 100 and a carriage 110 that can reciprocate in the Y-axis direction in the housing 100 and that carries four head units 3 .

[0051] In this embodiment, if Figure 2 As shown, it is assumed that the carriage 110 stores four ink cartridges 120 corresponding to the four colors of ink, cyan, magenta, yellow, and black. In addition, in the present embodiment, as described above, it is assumed that the inkjet printer 1 has 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 provided with the ejection portion D[m]. Thus, each ejection portion D[m] can fill the supplied ink inside and eject the ink filled inside the ejection portion D[m] from the nozzle N[m] provided in the ejection portion D[m]. It should be noted that the ink cartridge 120 may also be provided outside the carriage 110.

[0052] In addition, as described above, the inkjet printer 1 according to this embodiment includes the transport unit 7. Figure 2As shown, the conveying unit 7 includes a carriage conveying mechanism 71 for reciprocating the carriage 110 in the Y-axis direction, a carriage guide shaft 76 for supporting the carriage 110 so as to freely reciprocate in the Y-axis direction, a medium conveying mechanism 73 for conveying the recording paper PP, and a platen 75 provided in the Z1 direction of the carriage 110. Therefore, when performing the printing process, the conveying unit 7 causes the head unit 3 to reciprocate along the carriage guide shaft 76 in the Y-axis direction together with the carriage 110 through the carriage conveying mechanism 71, and conveys the recording paper PP on the platen 75 in the X1 direction through the medium conveying mechanism 73, thereby changing the relative position of the recording paper PP and the head unit 3, and making it possible to drop ink on the entire recording paper PP.

[0053] Figure 3 It is a partial schematic cross-sectional view of the recording head 32 obtained by cutting the recording head 32 in a state including the discharge portion D[m].

[0054] like Figure 3 As shown, the ejection unit D[m] includes a piezoelectric element PZ[m], a cavity CV[m] filled with ink, a nozzle N[m] connected to the cavity CV[m], and a vibration plate 321. The ejection unit D[m] is driven by the piezoelectric element PZ[m] by supplying a driving signal Vin[m], so that the ink in the cavity CV[m] is ejected from the nozzle N[m]. The cavity CV[m] is a space defined by a cavity plate 324, a nozzle plate 323 formed with the nozzle N[m], and a vibration plate 321. The cavity CV[m] is connected to the reservoir 325 through an ink supply port 326. The reservoir 325 is connected to the ink cartridge 120 corresponding to the ejection unit D[m] through an ink inlet 327. The piezoelectric element PZ[m] includes an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric body Zm[m] provided between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is electrically connected to a power supply line Ld set to a predetermined potential VBS. In addition, when a supply drive signal Vin[m] is supplied to the upper electrode Zu[m] to apply a voltage between the upper electrode Zu[m] and the lower electrode Zd[m], the piezoelectric element PZ[m] is displaced in the Z1 direction or the Z2 direction according to the applied voltage, and as a result, the piezoelectric element PZ[m] vibrates. The lower electrode Zd[m] is bonded to the vibration plate 321. Therefore, when the piezoelectric element PZ[m] is driven to vibrate by the supply drive signal Vin[m], the vibration plate 321 also vibrates. Then, due to the vibration of the vibration plate 321, the volume of the cavity CV[m] and the pressure in the cavity CV[m] change, and the ink filled in the cavity CV[m] is ejected from the nozzle N[m].

[0055] It should be noted that in the present embodiment, cavity CV[m] is an example of a “pressure chamber”.

[0056] 2. Overview of the head unit

[0057] Refer to the following Figures 4 to 6 The outline of the head unit 3 will be described.

[0058] Figure 4 It is a block diagram showing an example of the configuration of the head unit 3 .

[0059] like Figure 4 As shown, the head unit 3 includes a supply circuit 31, a recording head 32, and a detection circuit 33. In addition, the head unit 3 includes a wiring La, a wiring Ln, and a wiring Ls, wherein the wiring La is supplied with a printing drive signal Com-A from the drive signal generating unit 4, and the wiring Ln is supplied with a check drive signal Com-N from the drive signal generating unit 4, and the wiring Ls is used to supply a detection potential signal VX[m] to the detection circuit 33. In addition, the head unit 3 includes M wirings Lp[1] to Lp[M] corresponding to the M ejection parts D[1] to D[M]. Among them, the wiring Lp[m] is electrically connected to the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the ejection part D[m].

[0060] It should be noted that in this embodiment, wiring Ln is an example of “first wiring”, wiring Lp[m] is an example of “second wiring”, wiring La is an example of “third wiring”, and upper electrode Zu[m] is an example of “element electrode”.

[0061] The detection circuit 33 generates a detection signal SK[m] obtained by amplifying the detection potential signal VX[m] based on the detection potential signal VX[m] supplied from the wiring Ls. In addition, the detection circuit 33 amplifies the inspection drive signal Com-N supplied from the wiring Ln, and outputs the amplified inspection drive signal Com-N to the wiring Ls. It should be noted that, hereinafter, for the sake of convenience, the amplified inspection drive signal Com-N output by the detection circuit 33 is simply referred to as the inspection drive signal Com-N.

[0062] The supply circuit 31 includes M switches Wa[1] to Wa[M] corresponding one-to-one to the M ejection parts D[1] to D[M], M switches Ws[1] to Ws[M] corresponding one-to-one to the M ejection parts D[1] to D[M], and a connection state designation circuit 34 that designates the connection state of each switch.

[0063] The connection state designation circuit 34 generates a connection state designation signal Qa[m] for designating the on-off state of the switch Wa[m] and a connection state designation signal Qs[m] for designating the on-off state of the switch Ws[m] based on the designation signal SI and the latch signal LAT supplied from the control unit 2 .

[0064] The switch Wa[m] switches between the conduction and non-conduction of the wiring La and the wiring Lp[m] electrically connected to the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designation signal Qa[m]. In the present embodiment, the switch Wa[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 Wa[m] is turned on, the printing drive signal Com-A supplied to the wiring La is supplied as the supply drive signal Vin[m] to the upper electrode Zu[m] of the ejection unit D[m].

[0065] The switch Ws[m] switches the connection and non-conduction between the wiring Ls and the wiring Lp[m] electrically connected to the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designation signal Qs[m]. In the present embodiment, the switch Ws[m] is turned on when the connection state designation signal Qs[m] is at a high level, and is turned off when the connection state designation signal Qs[m] is at a low level. When the switch Ws[m] is turned on, the potential of the upper electrode Zu[m] provided at the ejection portion D[m] is supplied to the detection circuit 33 as a detection potential signal VX[m] via the wiring Lp[m] and the wiring Ls. In addition, when the switch Ws[m] is turned on, the inspection drive signal Com-N supplied to the wiring Ls is supplied to the upper electrode Zu[m] of the ejection portion D[m] as a supply drive signal Vin[m] via the wiring Lp[m].

[0066] It should be noted that, in the present embodiment, the switch Ws[m] is an example of a “first switch”, and the switch Wa[m] is an example of a “second switch”.

[0067] When the inkjet printer 1 executes printing or discharge state inspection, a plurality of unit periods TP are set as operation periods of the inkjet printer 1. The inkjet printer 1 can drive each discharge unit D for printing or discharge state inspection in each unit period TP.

[0068] Figure 5 1 is a timing chart showing an example of various signals such as the drive signal Com supplied to the head unit 3 within a plurality of unit periods TP.

[0069] like Figure 5 As shown, the control unit 2 outputs a latch signal LAT having a plurality of pulses PLL. Thus, the control unit 2 defines the unit period TP as a period from a rising edge of the pulse PLL to a rising edge of the next pulse PLL.

[0070] like Figure 5As shown, the designation signal SI includes 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 inspection process, the individual designation signal Sd[m] designates the driving form of the ejection unit D[m] within each unit period TP. Before each unit period TP, the control unit 2 synchronizes the designation signal SI including the M individual designation signals Sd[1] to Sd[M] with the clock signal CL and supplies it to the connection state designation circuit 34. Then, the connection state designation circuit 34 generates a connection state designation signal Qa[m] and a connection state designation signal Qs[m] based on the individual designation signal Sd[m] within the unit period TP.

[0071] In this embodiment, the individual designated signal Sd[m] can take any one of three values, namely, a value "1" which designates the ejection unit D[m] as the printing ejection unit DP, a value "2" which designates the ejection unit D[m] as the dot non-forming ejection unit DH, and a value "3" which designates the ejection unit D[m] as the inspection object ejection unit DS, within a unit period TP for executing the printing process or the ejection status inspection process.

[0072] Here, the printing ejection portion DP refers to an ejection portion D that ejects ink from the nozzle N[m] and forms a dot Dt on the recording paper PP within the unit period TP. In addition, the dot non-forming ejection portion DH refers to an ejection portion D that does not eject ink from the nozzle N[m] and does not form a dot Dt on the recording paper PP within the unit period TP. In addition, as described above, the inspection target ejection portion DS refers to an ejection portion D that becomes the object of the ejection state inspection process within the unit period TP.

[0073] like Figure 5 As shown, the printing drive signal Com-A has a waveform PA set in each unit period TP. Here, the waveform PA is a waveform that returns to the reference potential V0 from the reference potential V0 through the potential VL1 lower than the reference potential V0 and the potential VH1 higher than the reference potential V0 in each unit period TP. When the supply drive signal Vin[m] having the waveform PA is supplied to the ejection portion D[m], the waveform PA is determined so that ink corresponding to the dot Dt is ejected from the ejection portion D[m].

[0074] It should be noted that, in the present embodiment, as an example, it is assumed that when the potential of the supply drive signal Vin[m] supplied to the ejection portion D[m] is high, the volume of the cavity CV[m] provided in the ejection portion D[m] becomes smaller than when the potential of the supply drive signal Vin[m] supplied to the ejection portion D[m] is low. Therefore, when the ejection portion D[m] is driven by the supply drive signal Vin[m] having the waveform PA, the potential of the supply drive signal Vin[m] changes from low to high, and the ink in the ejection portion D[m] is ejected from the nozzle N[m].

[0075] like Figure 5 As shown, the inspection drive signal Com-N has a waveform PN set in each unit period TP. Here, the waveform PN is a waveform having elements PN1, element PN2, and element PN3, and returns from the reference potential V0 through the potential VN lower than the reference potential V0. Among them, the element PN1 is an element of the waveform PN, which is set in the period TS1 in the unit period TP, and the potential changes from the reference potential V0 to the potential VN lower than the reference potential V0. In addition, the element PN2 is an element of the waveform PN, which is set in the period TS2 following the period TS1 in the unit period TP, and maintains the potential VN. In addition, the element PN3 is an element of the waveform PN, which is set in the period TS3 following the period TS2 in the unit period TP, and the potential changes from the potential VN to the reference potential V0.

[0076] In the present embodiment, the waveform PN is determined so that ink is not discharged from the discharge portion D[m] even if the discharge portion D[m] is driven by the inspection drive signal Com-N.

[0077] It should be noted that, hereinafter, the signal of the part of the inspection drive signal Com-N corresponding to the element PN1 is sometimes referred to as the inspection drive signal Com-N1. Here, the inspection drive signal Com-N1 is an example of a "first inspection signal", the element PN1 is an example of a "first inspection waveform", and the period TS1 is an example of a "first inspection period".

[0078] In addition, hereinafter, the signal of the part corresponding to the element PN2 in the inspection drive signal Com-N is sometimes referred to as the inspection drive signal Com-N2. Here, the inspection drive signal Com-N2 is an example of the "second inspection signal", the potential VN is an example of the "detection potential", and the period TS2 is an example of the "second inspection period".

[0079] Figure 6 This is an explanatory diagram showing an example of the operation of the connection state specifying circuit 34.

[0080] like Figure 6As shown in FIG. 1 , when the individual designation signal Sd[m] indicates a value of "1" that designates the ejection unit D[m] as the printing ejection unit DP in the unit period TP, the connection state designation circuit 34 sets the connection state designation signal Qa[m] to a high level in the entire unit period TP. In this case, the switch Wa[m] is turned on in the entire unit period TP. Therefore, the ejection unit D[m] is driven by the supply drive signal Vin[m] having the waveform PA in the unit period TP, and ejects ink in an amount corresponding to the dot Dt.

[0081] In addition, when the individual designation signal Sd[m] indicates a value of "2" for designating the ejection unit D[m] as the dot non-forming ejection unit DH in the unit period TP, the connection state designation circuit 34 sets the connection state designation signal Qa[m] and the connection state designation signal Qs[m] to a low level in the entire unit period TP. In this case, the switch Wa[m] and the switch Ws[m] are disconnected in the entire unit period TP. Therefore, the ejection unit D[m] is not driven by the driving signal Vin[m] in the unit period TP, and does not eject ink.

[0082] In addition, when the individual designation signal Sd[m] indicates a value "3" for designating the ejection unit D[m] as the ejection unit DS to be inspected in the unit period TP, the connection state designation circuit 34 sets the connection state designation signal Qs[m] to a high level in the entire unit period TP. In this case, the switch Ws[m] is turned on in the entire unit period TP. Therefore, the ejection unit D[m] is driven by the supply drive signal Vin[m] having the waveform PN as the ejection unit DS to be inspected in the unit period TP.

[0083] When the ejection unit D[m] is driven as the ejection unit DS to be inspected, the inspection drive signal Com-N supplied to the ejection unit D[m] during the period TS1 is the inspection drive signal Com-N1 having the element PN1 that changes from the reference potential V0 to the potential VN. Therefore, during the period TS1, the ejection unit D[m] is driven by the inspection drive signal Com-N1 having the element PN1 and vibrates.

[0084] In addition, when the ejection unit D[m] is driven as the ejection unit DS to be inspected, the inspection drive signal Com-N supplied to the ejection unit D[m] during the period TS2 is the inspection drive signal Com-N2 having the element PN2 for maintaining a certain potential VN. Therefore, the potential of the upper electrode Zu[m] detected by the detection circuit 33 as the detection potential signal VX[m] through the switch Ws[m] during the period TS2 represents the waveform of the vibration remaining in the ejection unit D[m] during the period TS2. Then, the waveform of the detection signal SK[m] generated based on the detection potential signal VX[m] detected from the ejection unit D[m] during the period TS2 represents the waveform of the vibration remaining in the ejection unit D[m] during the period TS2.

[0085] It should be noted that, when the ejection unit D[m] is driven as the inspection target ejection unit DS, the unit period TP during which the ejection unit D[m] is driven as the inspection target ejection unit DS is referred to as the “inspection period”. Also, when the ejection unit D[m] is driven as the printing ejection unit DP, the unit period TP during which the ejection unit D[m] is driven as the printing ejection unit DP is referred to as the “printing period”.

[0086] 3. Inspection unit

[0087] Refer to the following Figure 7 and Figure 8 The outline of the inspection unit 5 will be described.

[0088] As described above, the inspection unit 5 inspects the ejection state of ink in the ejection portion D[m] designated as the inspection target ejection portion DS based on the detection signal SK[m] supplied from the detection circuit 33 .

[0089] Figure 7 1 is a timing chart for explaining an example of the detection signal SK[m] supplied by the detection circuit 33 to the inspection unit 5. It should be noted that the detection signal SK[m] output by the detection circuit 33 in the period TS2 represents a waveform based on the vibration remaining in the discharge portion D[m] in the period TS2.

[0090] like Figure 7 As shown, hereinafter, the period from the timing when the potential of the detection signal SK[m] matches the central potential VK0 set near the amplitude center of the detection signal SK[m] to the next timing when the potential matches the central potential VK0 is referred to as the cycle period NTC[m]. In addition, hereinafter, the time length of the cycle period NTC[m] is referred to as the cycle TC[m].

[0091] In this embodiment, the inspection unit 5 measures the period TC[m] of the detection signal SK[m]. Then, the inspection unit 5 inspects the ejection state of the ink in the ejection portion D[m] based on the period TC[m] and generates inspection result information SH[m] indicating the inspection result.

[0092] Figure 8 This is an explanatory diagram for explaining an example of generating the inspection result information SH[m] in the inspection unit 5.

[0093] like Figure 8 As shown, the inspection unit 5 inspects the ink ejection state in the ejection portion D[m] by comparing the period TC[m] with part or all of the thresholds Tth1, Tth2 and Tth3, and generates inspection result information SH[m] indicating the result of the inspection.

[0094] The threshold value Tth1 is a fixed value used to represent the boundary between the period TC[m] of the residual vibration occurring in the ejection part D[m] when the ejection state of the ejection part D[m] is normal and the period TC[m] of the residual vibration occurring in the ejection part D[m] when bubbles are mixed into the cavity CV[m] of the ejection part D[m].

[0095] Threshold value Tth2 is a value larger than threshold value Tth1, and is a fixed value used to represent the boundary between period TC[m] of residual vibration occurring in ejection portion D[m] when the ejection state of ejection portion D[m] is normal and period TC[m] of residual vibration occurring in ejection portion D[m] when foreign matter is attached near nozzle N[m] of ejection portion D[m].

[0096] Threshold value Tth3 is a value larger than threshold value Tth2, and is a fixed value used to represent the boundary between period TC[m] of residual vibration occurring in ejection portion D[m] when foreign matter adheres to the vicinity of nozzle N[m] of ejection portion D[m] and period TC[m] of residual vibration occurring in ejection portion D[m] after ink viscosity increases in cavity CV[m] of ejection portion D[m].

[0097] In this embodiment, when the period TC[m] satisfies "Tth1≤TC[m]≤Tth2", the inspection unit 5 regards the ejection state of the ink in the ejection section D[m] as normal, and sets the value "1" indicating that the ejection state of the ink in the ejection section D[m] is normal to the inspection result information SH[m].

[0098] In addition, when the period TC[m] satisfies "TC[m]<Tth1", the inspection unit 5 regards that a discharge abnormality caused by bubbles has occurred in the discharge section D[m], and sets the value "2" indicating that a discharge abnormality caused by bubbles has occurred in the discharge section D[m] to the inspection result information SH[m].

[0099] In addition, when the period TC[m] satisfies "Tth2<TC[m]≤Tth3", the inspection unit 5 regards that a discharge abnormality caused by foreign matter adhesion has occurred in the discharge section D[m], and sets the value "3" indicating that a discharge abnormality caused by foreign matter adhesion has occurred in the discharge section D[m] in the inspection result information SH[m].

[0100] In addition, when the period TC[m] satisfies "Tth3<TC[m]", the inspection unit 5 regards that a discharge abnormality caused by thickening has occurred in the discharge portion D[m], and sets the value "4" indicating that a discharge abnormality caused by thickening has occurred in the discharge portion D[m] to the inspection result information SH[m].

[0101] 4. Inspection unit

[0102] Refer to the following Figures 9 to 12 The outline of the detection circuit 33 will be described.

[0103] Fig. 9 2 is a circuit diagram showing an example of the configuration of the detection circuit 33 .

[0104] like Fig. 9 As shown, the detection circuit 33 includes an amplifier circuit 331, a subtraction circuit 332, and an amplifier circuit 333. It should be noted that the amplifier circuit 331 is an example of a "first amplifier circuit", and the amplifier circuit 333 is an example of a "second amplifier circuit".

[0105] like Fig. 9 As shown, the amplifier circuit 331 includes an operational amplifier OP1, a resistor RS1, a resistor RS2, a node Nd1, and a node Nd2.

[0106] The operational amplifier OP1 includes an inverting input terminal (-) electrically connected to the node Nd1, a non-inverting input terminal (+) electrically connected to the wiring Ln, and an output terminal electrically connected to the node Nd2. A signal having a potential determined based on the potential of the signal input to the inverting input terminal of the operational amplifier OP1 and the potential of the signal input to the non-inverting input terminal of the operational amplifier OP1 is output from the output terminal of the operational amplifier OP1.

[0107] One end of the resistor RS1 is electrically connected to the node Nd1 , and the other end is electrically connected to the node Nd2 .

[0108] One end of the resistor RS2 is electrically connected to the wiring Ls via the switch Ws[m], and the other end is electrically connected to the node Nd1 .

[0109] As can be seen from the above, in the present embodiment, the amplifier circuit 331 is configured to include no switch element except for various elements provided inside the operational amplifier OP1 .

[0110] It should be noted that, in the present embodiment, the operational amplifier OP1 is an example of a “first amplifier”, the inverting input terminal of the operational amplifier OP1 is an example of a “first input terminal”, the non-inverting input terminal of the operational amplifier OP1 is an example of a “second input terminal”, and the output terminal of the operational amplifier OP1 is an example of a “first output terminal”. In addition, in the present embodiment, the resistor RS1 is an example of a “first resistor”, the resistor RS2 is an example of a “second resistor”, the node Nd1 is an example of a “first node”, and the node Nd2 is an example of a “second node”. The node Nd3 is an example of a “third node”, the node Nd4 is an example of a “fourth node”, and the node Nd5 is an example of a “fifth node”.

[0111] like Fig. 9 As shown, the subtraction circuit 332 includes an operational amplifier OP2, a resistor RS3, a resistor RS4, a resistor RS5, a resistor RS6, a node Nd3, a node Nd4, and a node Nd5.

[0112] The operational amplifier OP2 includes an inverting input terminal (-) electrically connected to the node Nd3, a non-inverting input terminal (+) electrically connected to the node Nd5, and an output terminal electrically connected to the node Nd4. A signal having a potential determined based on the potential of the signal input to the inverting input terminal of the operational amplifier OP2 and the potential of the signal input to the non-inverting input terminal of the operational amplifier OP2 is output from the output terminal of the operational amplifier OP2.

[0113] One end of the resistor RS3 is electrically connected to the node Nd3 , and the other end thereof is electrically connected to the node Nd4 .

[0114] One end of the resistor RS4 is electrically connected to the node Nd2 , and the other end thereof is electrically connected to the node Nd3 .

[0115] One end of the resistor RS5 is electrically connected to the node Nd5 , and the other end thereof is electrically connected to the wiring Ln.

[0116] One end of the resistor RS6 is electrically connected to the node Nd5 , and the other end is electrically connected to the power supply line Lf1 set to a predetermined reference potential Vref1 .

[0117] As can be seen from the above, in the present embodiment, the subtraction circuit 332 is configured to include no switch element except for various elements provided inside the operational amplifier OP2.

[0118] It should be noted that, in the present embodiment, the operational amplifier OP2 is an example of a "second amplifier", the inverting input terminal of the operational amplifier OP2 is an example of a "third input terminal", the non-inverting input terminal of the operational amplifier OP2 is an example of a "fourth input terminal", and the output terminal of the operational amplifier OP2 is an example of a "second output terminal". In addition, in the present embodiment, the resistor RS3 is an example of a "third resistor", the resistor RS4 is an example of a "fourth resistor", the resistor RS5 is an example of a "fifth resistor", and the resistor RS6 is an example of a "sixth resistor". In addition, in the present embodiment, the node Nd3 is an example of a "third node", the node Nd4 is an example of a "fourth node", and the node Nd5 is an example of a "fifth node". In addition, in the present embodiment, the power supply line Lf1 is an example of a "first power supply line", and the reference potential Vref1 is an example of a "first reference potential".

[0119] like Fig. 9 As shown, the amplifier circuit 333 includes an operational amplifier OP3, a resistor RS7, a resistor RS8, a node Nd6, and a node Nd7.

[0120] The operational amplifier OP3 includes an inverting input terminal (-) electrically connected to the node Nd6, a non-inverting input terminal (+) electrically connected to the power supply line Lf2 set to a predetermined reference potential Vref2, and an output terminal electrically connected to the node Nd7. A signal having a potential determined based on the potential of the signal input to the inverting input terminal of the operational amplifier OP3 and the potential of the signal input to the non-inverting input terminal of the operational amplifier OP3 is output from the output terminal of the operational amplifier OP3.

[0121] One end of the resistor RS7 is electrically connected to the node Nd6 , and the other end is electrically connected to the node Nd7 .

[0122] One end of the resistor RS8 is electrically connected to the node Nd4 , and the other end is electrically connected to the node Nd6 .

[0123] As can be seen from the above, in the present embodiment, the amplifier circuit 333 is configured to include no switch element except for various elements provided inside the operational amplifier OP3.

[0124] It should be noted that, in the present embodiment, the operational amplifier OP3 is an example of a “third amplifier”, the inverting input terminal of the operational amplifier OP3 is an example of a “fifth input terminal”, the non-inverting input terminal of the operational amplifier OP3 is an example of a “sixth input terminal”, and the output terminal of the operational amplifier OP3 is an example of a “third output terminal”. In addition, in the present embodiment, the resistor RS7 is an example of a “seventh resistor”, the resistor RS8 is an example of an “eighth resistor”, the node Nd6 is an example of a “sixth node”, and the node Nd7 is an example of a “seventh node”. In addition, in the present embodiment, the power supply line Lf2 is an example of a “second power supply line”, and the reference potential Vref2 is an example of a “second reference potential”.

[0125] Fig.10 and Fig.11 1 is a diagram showing an example of the operation of the head unit 3 when the discharge state inspection process is executed for the discharge portion D[m].

[0126] like Fig.10 As shown, when the ejection state inspection process is performed on the ejection unit D[m], the connection state designation signal Qs[m] becomes high level, and the switch Ws[m] is turned on. Therefore, the inspection drive signal Com-N supplied to the wiring Ln is supplied from the non-inverting input terminal of the operational amplifier OP2 via the output terminal of the operational amplifier OP2, the resistor RS1, the resistor RS2, the wiring Ls, the switch Ws[m], and the wiring Lp[m] to the upper electrode Zu[m] of the piezoelectric element PZ[m]. As a result, the ejection unit D[m] is driven by the inspection drive signal Com-N1 having the element PN1 in the inspection drive signal Com-N to vibrate during the period TS1 of the unit period TP in which the ejection state inspection process is performed on the ejection unit D[m].

[0127] like Fig.11 As shown in FIG. 1 , when the ejection state inspection process for the ejection unit D[m] is executed, the switch Ws[m] is turned on, so that the detection potential signal VX[m] indicating the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] is supplied from the upper electrode Zu[m] to the amplifier circuit 331 via the wiring Lp[m], the switch Ws[m], and the wiring Ls. The detection potential signal VX[m] supplied to the amplifier circuit 331 is amplified in the detection circuit 33 and then output as the detection signal SK[m] from the amplifier circuit 333. Thus, the detection circuit 33 outputs the detection signal SK[m] having a waveform corresponding to the vibration remaining in the ejection unit D[m] during the period TS2 after the ejection unit D[m] is driven.

[0128] Fig.12This is a diagram showing an example of the operation of the head unit 3 when the discharge unit D[m] is driven as the print discharge unit DP during the execution of the printing process.

[0129] like Fig.12 As shown in FIG. 1 , when the ejection unit D[m] is driven as the printing ejection unit DP, the connection state designation signal Qa[m] becomes high level, and the switch Wa[m] is turned on. Therefore, the printing drive signal Com-A supplied to the wiring La is supplied from the wiring La to the upper electrode Zu[m] of the piezoelectric element PZ[m] via the switch Wa[m] and the wiring Lp[m]. As a result, the ejection unit D[m] is driven as the printing ejection unit DP and ejects ink.

[0130] 5. Summary of implementation methods

[0131] In summary, the inkjet printer 1 involved in this embodiment is characterized by comprising: an ejection portion D[m], comprising a piezoelectric element PZ[m] driven by a drive signal Com, a cavity CV[m] filled with ink and whose volume changes according to the driving of the piezoelectric element PZ[m], and a nozzle N[m] that ejects the ink in the cavity CV[m] according to the change in the volume of the cavity CV[m]; a wiring Ln, to which a check drive signal Com-N in the drive signal Com is supplied; a wiring Lp[m] electrically connected to an upper electrode Zu[m] of the piezoelectric element PZ[m]; and a detection circuit 33 that detects the upper electrode Zu[m] that changes according to the vibration remaining in the piezoelectric element PZ[m] after the driving of the piezoelectric element PZ[m]. [m]; and an inspection unit 5, which determines the ejection state of the ink in the ejection portion D[m] based on the detection result of the detection circuit 33, the detection circuit 33 has an amplifier circuit 331, and the amplifier circuit 331 has: an operational amplifier OP1, having an inverting input terminal, a non-inverting input terminal, and an output terminal that outputs a signal based on an input to the inverting input terminal and an input to the non-inverting input terminal; a resistor RS1, which electrically connects a node Nd1 electrically connected to the inverting input terminal of the operational amplifier OP1 and a node Nd2 electrically connected to the output terminal of the operational amplifier OP1; and a resistor RS2, which electrically connects the node Nd1 and the wiring Lp[m], and the wiring Ln is electrically connected to the non-inverting input terminal of the operational amplifier OP1.

[0132] According to the present embodiment, the inspection drive signal Com-N can be supplied to the piezoelectric element PZ[m] via the wiring Ln, the operational amplifier OP1, the resistor RS1, the resistor RS2, and the wiring Lp[m]. That is, according to the present embodiment, the supply of the inspection drive signal Com-N to the piezoelectric element PZ[m] and the acquisition of the detection potential signal VX[m] from the piezoelectric element PZ[m] can be performed together through the path through the amplifier circuit 331. Therefore, according to the present embodiment, there is no need to switch the conduction and non-conduction of the switch between the piezoelectric element PZ[m] and the detection circuit 33, such as occurs in a form where the path for supplying the inspection drive signal Com-N to the piezoelectric element PZ[m] and the path for acquiring the detection potential signal VX[m] from the piezoelectric element PZ[m] are different. Therefore, according to this embodiment, compared with a form in which the path for supplying the inspection drive signal Com-N to the piezoelectric element PZ[m] and the path for obtaining the detection potential signal VX[m] from the piezoelectric element PZ[m] are different, the detection circuit 33 can accurately detect the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m].

[0133] The inkjet printer 1 according to the present embodiment is characterized in that the inkjet printer 1 includes a switch Ws[m] for switching between conduction and non-conduction between the wiring Lp[m] and the resistor RS2.

[0134] According to the present embodiment, it is not necessary to switch the switch Ws[m] between the period when the inspection drive signal Com-N is supplied to the piezoelectric element PZ[m] and the period when the detection potential signal VX[m] is obtained from the piezoelectric element PZ[m]. Therefore, according to the present embodiment, the detection circuit 33 can accurately detect the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m], compared with a form in which the path for supplying the inspection drive signal Com-N to the piezoelectric element PZ[m] and the path for obtaining the detection potential signal VX[m] from the piezoelectric element PZ[m] are different.

[0135] In addition, in the inkjet printer 1 involved in this embodiment, it is characterized in that the inspection drive signal Com-N includes an inspection drive signal Com-N1 set in the period TS1 of the unit period TP and having an element PN1 for driving the piezoelectric element PZ[m], and an inspection drive signal Com-N2 set in the period TS2 following the period TS1 in the unit period TP and having an element PN2 for maintaining the potential VN, and the switch Ws[m] is maintained in the on state during the period TS1 and the period TS2.

[0136] According to the present embodiment, the switch Ws[m] is not switched between the conduction and non-conduction between the period TS1 during which the inspection drive signal Com-N is supplied to the piezoelectric element PZ[m] and the period TS2 during which the detection potential signal VX[m] is obtained from the piezoelectric element PZ[m]. Therefore, according to the present embodiment, the detection circuit 33 can accurately detect the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m], compared with a form in which the path for supplying the inspection drive signal Com-N to the piezoelectric element PZ[m] and the path for obtaining the detection potential signal VX[m] from the piezoelectric element PZ[m] are different.

[0137] Furthermore, in the inkjet printer 1 according to the present embodiment, a feature of the amplifier circuit 331 is that it does not include a switching element outside the operational amplifier OP1.

[0138] Therefore, according to the present embodiment, compared with a configuration in which the amplifier circuit 331 and the operational amplifier OP1 each include a switch element, the detection circuit 33 can accurately detect the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m].

[0139] In addition, in the inkjet printer 1 involved in the present embodiment, it is characterized in that the detection circuit 33 has a subtraction circuit 332, and the subtraction circuit 332 has: an operational amplifier OP2, having an inverting input terminal, a non-inverting input terminal, and an output terminal that outputs a signal based on an input to the inverting input terminal and an input to the non-inverting input terminal; a resistor RS3, electrically connecting a node Nd3 electrically connected to the inverting input terminal of the operational amplifier OP2 and a node Nd4 electrically connected to the output terminal of the operational amplifier OP2; a resistor RS4, electrically connecting the node Nd2 and the node Nd3; a resistor RS5, electrically connecting a node Nd5 electrically connected to the non-inverting input terminal of the operational amplifier OP2 and the wiring Ln; and a resistor RS6, electrically connecting the node Nd5 and the power supply line Lf1 set to a reference potential Vref1.

[0140] In addition, in the inkjet printer 1 according to the present embodiment, a feature is that the subtraction circuit 332 does not include a switching element outside the operational amplifier OP2.

[0141] Therefore, according to the present embodiment, compared with a configuration in which the subtraction circuit 332 and the operational amplifier OP2 each include a switch element separately, the detection circuit 33 can accurately detect the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m].

[0142] In addition, in the inkjet printer 1 involved in the present embodiment, it is characterized in that the detection circuit 33 includes an amplifier circuit 333, and the amplifier circuit 333 includes: an operational amplifier OP3 having an inverting input terminal, a non-inverting input terminal electrically connected to the power supply line Lf2 set to a reference potential Vref2, and an output terminal that outputs a signal based on an input to the inverting input terminal and an input to the non-inverting input terminal; a resistor RS7 that electrically connects a node Nd6 electrically connected to the inverting input terminal of the operational amplifier OP3 and a node Nd7 electrically connected to the output terminal of the operational amplifier OP3; and a resistor RS8 that electrically connects the node Nd4 and the node Nd6.

[0143] In the inkjet printer 1 according to the present embodiment, a feature of the amplifier circuit 333 is that it does not include a switching element outside the operational amplifier OP3.

[0144] Therefore, according to the present embodiment, compared with a configuration in which the amplifier circuit 333 and the operational amplifier OP3 each include a switch element separately, the detection circuit 33 can accurately detect the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m].

[0145] In addition, in the inkjet printer 1 involved in the present embodiment, it is characterized in that the inkjet printer 1 comprises: wiring La, to which the printing drive signal Com-A in the drive signal Com is supplied; and switch Wa[m], which switches the conduction and non-conduction between the wiring Lp[m] and the wiring La, and the switch Wa[m] maintains an off state during a unit period TP in which the ejection part D[m] is driven as the inspection object ejection part DS, and the switch Wa[m] maintains an on state during a unit period TP in which the ejection part D[m] is driven as the printing ejection part DP, and the switch Ws[m] maintains an off state during a unit period TP in which the ejection part D[m] is driven as the printing ejection part DP.

[0146] B. Modification

[0147] The above methods can be modified in many ways. The specific modification methods are illustrated below. Two or more forms 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 illustrated below, the elements with the same effects and functions as the implementation methods will be marked with the reference numerals in the above description to appropriately omit their detailed descriptions.

[0148] Modification 1

[0149] In the above embodiment, the following form is illustrated for explanation, that is, during the unit period TP in which all the ejection units D[m] are driven as printing ejection units DP, the switch Wa[m] remains in the on state, and during the entire unit period TP, the printing drive signal Com-A is supplied to the upper electrode Zu[m], but the present invention is not limited to such a form.

[0150] For example, the switch Wa[m] may be turned on during a portion of the unit period TP in which the ejection unit D[m] is driven as the printing ejection unit DP, and the printing drive signal Com-A may be supplied to the upper electrode Zu[m] during a portion of the period.

[0151] Modification 2

[0152] In the above-mentioned embodiment and modification 1, the case where the inspection unit 5 is provided separately from the head unit 3 is illustrated for explanation, but the present invention is not limited to such a form. The inspection unit 5 may also be provided in the head unit 3. In this case, compared with the form where the inspection unit 5 is provided outside the head unit 3, the possibility of noise mixing into the detection signal SK[m] supplied to the inspection unit 5 by the detection circuit 33 can be suppressed, thereby improving the accuracy of the inspection in the inspection unit 5.

[0153] Modification 3

[0154] In the above-mentioned embodiment and modified examples 1 and 2, it is assumed that the inkjet printer 1 has four head units 3, but the present invention is not limited to such a form. The inkjet printer 1 may be a printer having more than one and less than three head units 3, or a printer having more than five head units 3. In addition, in the above-mentioned embodiment and modified examples 1 and 2, it is assumed that the inkjet printer 1 has four inspection units 5, but the present invention is not limited to such a form. The inkjet printer 1 may also have more than one inspection unit 5. For example, the inkjet printer 1 may have more inspection units 5 than the head units 3, or may have fewer inspection units 5 than the head units 3.

[0155] Modification 4

[0156] In the above-described embodiment and Modifications 1 to 3, the inkjet printer 1 is exemplified as a serial printer, but the present invention is not limited to such a form. The inkjet printer 1 may also be a so-called line printer in which a plurality of nozzles N[1] to N[M] are provided in a head unit 3 so as to extend in a range wider than the width of the recording paper PP.

Claims

1. A liquid ejection device, characterized in that: have: A discharge unit including a piezoelectric element driven by a driving signal, a pressure chamber filled with a liquid and having a volume changed according to the driving of the piezoelectric element, and a nozzle for discharging the liquid in the pressure chamber according to the change in the volume of the pressure chamber; a first wiring to which a first drive signal among the drive signals is supplied; A second wiring electrically connected to an element electrode of the piezoelectric element; a detection circuit for detecting a potential of the element electrode that changes according to vibration remaining in the piezoelectric element after the piezoelectric element is driven; as well as an inspection device for inspecting the ejection state of the liquid in the ejection portion based on the detection result of the detection circuit, The detection circuit comprises a first amplification circuit, The first amplifier circuit comprises: A first amplifier having a first input terminal, a second input terminal, and a first output terminal that outputs a signal based on an input to the first input terminal and an input to the second input terminal; a first resistor electrically connecting a first node electrically connected to the first input terminal and a second node electrically connected to the first output terminal; as well as a second resistor electrically connecting the first node and the second wiring, The first wiring is electrically connected to the second input terminal.

2. The liquid ejection device according to claim 1, characterized in that: The liquid ejection device includes a first switch that switches between conduction and non-conduction between the second wiring and the second resistor.

3. The liquid ejection device according to claim 2, characterized in that: The first driving signal includes: a first inspection signal provided in a first inspection period of the inspection period and having a first inspection waveform for driving the piezoelectric element; and The second inspection signal is set in a second inspection period following the first inspection period in the inspection period and maintains a certain detection potential. The first switch is maintained in an on state during the first inspection period and the second inspection period.

4. The liquid ejection device according to claim 1, characterized in that: The first amplification circuit does not include a switching element outside the first amplifier.

5. The liquid ejection device according to claim 1, characterized in that: The detection circuit includes a subtraction circuit, The subtraction circuit comprises: a second amplifier having a third input terminal, a fourth input terminal, and a second output terminal that outputs a signal based on an input to the third input terminal and an input to the fourth input terminal; a third resistor electrically connecting a third node electrically connected to the third input terminal and a fourth node electrically connected to the second output terminal; a fourth resistor, electrically connecting the second node and the third node; a fifth resistor electrically connecting a fifth node electrically connected to the fourth input terminal and the first wiring; as well as The sixth resistor electrically connects the fifth node and the first power supply line set to a first reference potential.

6. The liquid ejection device according to claim 5, characterized in that: The subtraction circuit does not include a switching element outside the second amplifier.

7. The liquid ejection device according to claim 1, characterized in that: The detection circuit includes a second amplification circuit. The second amplifier circuit comprises: a third amplifier having a fifth input terminal, a sixth input terminal electrically connected to a second power supply line set to a second reference potential, and a third output terminal outputting a signal based on an input to the fifth input terminal and an input to the sixth input terminal; a seventh resistor electrically connecting a sixth node electrically connected to the fifth input terminal and a seventh node electrically connected to the third output terminal; as well as An eighth resistor electrically connects the fourth node and the sixth node.

8. The liquid ejection device according to claim 7, characterized in that: The second amplifier circuit does not include a switching element outside the third amplifier.

9. The liquid ejection device according to claim 3, characterized in that: The liquid ejection device comprises: a third wiring to which a second drive signal among the drive signals is supplied; and a second switch for switching conduction and non-conduction between the second wiring and the third wiring, During the inspection period, the second switch remains in an off state. During a part or all of a printing period different from the inspection period, the second switch is kept in the on state. During the printing period, the first switch is maintained in an off state.

10. A liquid ejection head, characterized in that: have: A piezoelectric element driven by a driving signal; a pressure chamber filled with liquid and having a volume that changes according to the driving of the piezoelectric element; a nozzle for ejecting liquid in the pressure chamber according to a change in the volume of the pressure chamber; a first wiring to which a first drive signal among the drive signals is supplied; A second wiring electrically connected to an element electrode of the piezoelectric element; as well as a detection circuit for detecting the potential of the element electrode that changes according to the vibration remaining in the piezoelectric element after the piezoelectric element is driven, The detection circuit comprises a first amplification circuit, The first amplifier circuit comprises: A first amplifier having a first input terminal, a second input terminal, and a first output terminal that outputs a signal based on an input to the first input terminal and an input to the second input terminal; a first resistor electrically connecting a first node electrically connected to the first input terminal and a second node electrically connected to the first output terminal; as well as a second resistor electrically connecting the first node and the second wiring, The first wiring is electrically connected to the second input terminal.

11. The liquid ejection head according to claim 10, wherein: The liquid ejection head includes a first switch that switches between conduction and non-conduction between the second wiring and the second resistor.

12. The liquid ejection head according to claim 11, wherein: The first driving signal includes: a first inspection signal provided in a first inspection period of the inspection period and having a first inspection waveform for driving the piezoelectric element; and The second inspection signal is set in a second inspection period following the first inspection period in the inspection period and maintains a certain detection potential. The first switch is maintained in an on state during the first inspection period and the second inspection period.

13. The liquid ejection head according to claim 10, wherein: The first amplification circuit does not include a switching element outside the first amplifier.

14. The liquid ejection head according to claim 10, wherein: The detection circuit includes a subtraction circuit, The subtraction circuit comprises: a second amplifier having a third input terminal, a fourth input terminal, and a second output terminal that outputs a signal based on an input to the third input terminal and an input to the fourth input terminal; a third resistor electrically connecting a third node electrically connected to the third input terminal and a fourth node electrically connected to the second output terminal; a fourth resistor, electrically connecting the second node and the third node; a fifth resistor electrically connecting a fifth node electrically connected to the fourth input terminal and the first wiring; as well as The sixth resistor electrically connects the fifth node and the first power supply line set to a first reference potential.

15. The liquid ejection head according to claim 14, wherein: The subtraction circuit does not include a switching element outside the second amplifier.

16. The liquid ejection head according to claim 10, wherein: The detection circuit includes a second amplification circuit. The second amplifier circuit comprises: a third amplifier having a fifth input terminal, a sixth input terminal electrically connected to a second power supply line set to a second reference potential, and a third output terminal outputting a signal based on an input to the fifth input terminal and an input to the sixth input terminal; a seventh resistor electrically connecting a sixth node electrically connected to the fifth input terminal and a seventh node electrically connected to the third output terminal; as well as An eighth resistor electrically connects the fourth node and the sixth node.

17. The liquid ejection head according to claim 16, wherein: The second amplifier circuit does not include a switching element outside the third amplifier.

18. The liquid ejection head according to claim 12, wherein: The liquid ejection head comprises: a third wiring to which a second drive signal among the drive signals is supplied; and a second switch for switching conduction and non-conduction between the second wiring and the third wiring, During the inspection period, the second switch remains in an off state. During a part or all of a printing period different from the inspection period, the second switch is kept in the on state. During the printing period, the first switch is maintained in an off state.

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