Liquid dispensing device

Abstract

To suppress influence of noise generated due to a potential change of a driving signal on a signal different from the driving signal.SOLUTION: A liquid discharge head comprises a first piezoelectric element that is driven in response to supply of a first driving signal and a second piezoelectric element that is driven in response to supply of a second driving signal. The first driving signal is transferred from a first potential to a second potential in a first period of time, is maintained at the second potential in a second period of time following the first period of time, and is transferred from the second potential to the first potential in a third period of time following the second period of time. The second driving signal is transferred from a third potential to a fourth potential in a fourth period of time, is maintained at the fourth potential in a fifth period of time following the fourth period of time, and is transferred from the fourth potential to the third potential in a sixth period of time following the fifth period of time. Portions or whole of the first period of time and the fourth period of time overlap with each other, and portions or whole of the third period of time and the sixth period of time overlap with each other, where the second potential is higher than the first potential and the fourth potential is lower than the third potential.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a liquid ejection device and a capacitive load drive circuit. [Background technology]

[0002] Conventionally, liquid ejection devices that eject liquid such as ink have been known. For example, Patent Document 1 discloses a liquid ejection device that has a head unit including a plurality of piezoelectric elements and ejects liquid by supplying a drive signal to each of the plurality of piezoelectric elements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-36938 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional techniques, there is a risk that noise generated due to a change in potential of the drive signal supplied to the head unit may affect the signal supplied to the head unit or the signal obtained from the head unit. [Means for solving the problem]

[0005] In order to solve the above problems, a liquid ejection device according to a preferred embodiment of the present invention comprises a first piezoelectric element that is driven in response to the supply of a first drive signal, and a second piezoelectric element that is driven in response to the supply of a second drive signal, wherein the first drive signal transitions from a first potential to a second potential in a first period, maintains the second potential in a second period following the first period, transitions from the second potential to the first potential in a third period following the second period, the second drive signal transitions from a third potential to a fourth potential in a fourth period, maintains the fourth potential in a fifth period following the fourth period, and transitions from the fourth potential to the third potential in a sixth period following the fifth period, the first period and the fourth period overlap each other partially or completely, the third period and the sixth period overlap each other partially or completely, the second potential is higher than the first potential, and the fourth potential is lower than the third potential.

[0006] In order to solve the above problems, a capacitive load drive circuit according to a preferred embodiment of the present invention comprises a first piezoelectric element that drives in response to the supply of a first drive signal and a second piezoelectric element that drives in response to the supply of a second drive signal, wherein the first drive signal transitions from a first potential to a second potential in a first period, maintains the second potential in a second period following the first period, transitions from the second potential to the first potential in a third period following the second period, the second drive signal transitions from a third potential to a fourth potential in a fourth period, maintains the fourth potential in a fifth period following the fourth period, and transitions from the fourth potential to the third potential in a sixth period following the fifth period, the first period and the fourth period overlap each other partially or completely, the third period and the sixth period overlap each other partially or completely, the second potential is higher than the first potential, and the fourth potential is lower than the third potential. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a functional block diagram showing an example of the configuration of an inkjet printer 1 according to an embodiment of the present invention [Diagram 2]1 is a schematic diagram illustrating an inkjet printer 1. FIG. [Diagram 3] 2 is a schematic partial cross-sectional view of the recording head HD, in which the recording head HD is cut so as to include a discharge portion D. FIG. [Figure 4] 11 is an explanatory diagram for explaining an example of the ink ejection operation in the ejection section D. FIG. [Diagram 5] 11 is an explanatory diagram for explaining an example of the ink ejection operation in the ejection section D. FIG. [Figure 6] 11 is an explanatory diagram for explaining an example of the ink ejection operation in the ejection section D. FIG. [Figure 7] A diagram showing the wiring arrangement of FFC19. [Figure 8] FIG. 2 is a block diagram showing an example of the configuration of a head unit HU[q]. [Figure 9] 4 is a timing chart illustrating the operation of the inkjet printer 1 in a unit period Tu. FIG. [Figure 10] FIG. 4 is an explanatory diagram showing a first micro-vibration waveform WHb and a second micro-vibration waveform WLb. [Figure 11] 4 is an explanatory diagram for explaining the operation of the switching circuit 10 in a unit period Tu. [Figure 12] FIG. 2 is a diagram showing an example of the configuration of a connection state designation circuit 11[q] according to the present embodiment. [Figure 13] FIG. 13 is an explanatory diagram for explaining generation of a connection state designation signal in a decoder DC[q1][m]. [Figure 14] FIG. 13 is an explanatory diagram for explaining generation of a connection state designation signal in a decoder DC[q2][m]. [Figure 15] 5 is an explanatory diagram for explaining generation of determination information Stt in the discharge state determination circuit 64. FIG. [Figure 16] 5 is an explanatory diagram showing the influence of noise on a residual vibration signal NSAS due to a micro-vibration waveform in the present embodiment. [Figure 17] 11 is an explanatory diagram showing the influence of noise on a residual vibration signal NSAS due to a micro-vibration waveform in a reference example. [Figure 18] FIG. 11 is an explanatory diagram showing a first micro-vibration waveform WHb and a second micro-vibration waveform WLba in a first modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0009] 1. Embodiment In this embodiment, the liquid ejection device will be described by taking as an example an inkjet printer 1 that ejects ink to form an image on recording paper P. The inkjet printer 1 is an example of a "liquid ejection device." Ink is an example of a "liquid." Recording paper P is an example of a "medium."

[0010] 1.1. Overview of Inkjet Printers 1 The configuration of an inkjet printer 1 according to this embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a functional block diagram showing an example of the configuration of an inkjet printer 1 according to this embodiment. Fig. 2 is a schematic diagram illustrating the inkjet printer 1.

[0011] The inkjet printer 1 receives print data Img indicating the image to be formed by the inkjet printer 1, and information indicating the number of copies of the image to be formed by the inkjet printer 1, from a host computer such as a personal computer or digital camera. The inkjet printer 1 executes a printing process to form on recording paper P the image indicated by the print data Img supplied from the host computer.

[0012] As shown in FIG. 1, the inkjet printer 1 includes a head module HM having Q head units HU with ejection units D for ejecting ink, a maintenance unit 4, a control module 6 for controlling the operation of each unit of the inkjet printer 1, a transport mechanism 7 for transporting recording paper P, and a movement mechanism 8 for moving the head module HM. Q is an even number equal to or greater than 2. In the following, the Q head units HU may be referred to in order as 1st stage, 2nd stage, ..., Qth stage in order to distinguish them from one another. The head unit HU in the qth stage may be referred to as head unit HU[q]. The variable q is an integer equal to or greater than 1 and equal to or less than Q. In addition, when a component or signal of the inkjet printer 1 corresponds to the variable q of the head unit HU[q], the subscript [q] indicating that the component or signal corresponds to the number of stages q may be added to the symbol for the component or signal.

[0013] The control module 6 has a control unit 60, a memory unit 61, Q drive signal generation circuits 62 in one-to-one correspondence with the Q head units HU, an ejection state determination circuit 64 that determines the ejection state of the nozzles N included in the head units HU, and a constant voltage generation circuit 66. The control unit 60 is configured to include a CPU. CPU is an abbreviation for Central Processing Unit. However, the control unit 60 may include a programmable logic device such as an FPGA instead of the CPU. CPU is an abbreviation for Field Programmable Gate Array. The memory unit 61 stores the control program for the inkjet printer 1 and other information.

[0014] In this embodiment, each head unit HU includes a recording head HD having M ejection sections D, a switching circuit 10, and a detection circuit 20. In this embodiment, M is an integer of 2 or more. In the following, in order to distinguish between the M discharge sections D provided in the head unit HU[q], they may be referred to in order as 1st stage, 2nd stage, ..., Mth stage. Also, the mth stage of discharge sections D provided in the head unit HU[q] may be referred to as discharge section D[q][m]. The variable m is an integer between 1 and M. Also, when a component or signal of the inkjet printer 1 corresponds to the stage number m of the discharge sections D[q][m], the subscript [m] indicating that the component or signal corresponds to the stage number m may be added to the symbol representing the component or signal.

[0015] The control unit 60 generates a designation signal SI for controlling the head module HM, a waveform designation signal dCom[q] for controlling the drive signal generation circuit 62[q], a signal for controlling the transport mechanism 7, and a signal for controlling the movement mechanism 8. The waveform designation signal dCom[q] is a digital signal that defines the waveform of the drive signal Com[q]. In addition, the drive signal Com[q] is an analog signal for driving the discharge section D[q][m].

[0016] The drive signal generating circuit 62[q] includes a DA conversion circuit and generates a drive signal Com[q] having a waveform specified by a waveform designation signal dCom[q]. In this embodiment, it is assumed that the drive signal Com[q] includes a drive signal ComA[q] and a drive signal ComB[q]. For example, the drive signal generating circuit 62[q] generates the drive signal ComA[q] and the drive signal ComB[q] by two internally independent circuits.

[0017] The discharge state determination circuit 64 generates determination information Stt[q][m] indicating the result of the discharge state determination of the discharge section D[q][m] based on the residual vibration signal NSAS[q][m]. The residual vibration signal NSAS[q][m] is an example of a "detection signal." In the following, the discharge section D that is the subject of the discharge state determination by the discharge state determination circuit 64 may be referred to as the "discharge section DH to be determined." In addition, the discharge section DH to be determined in the head unit HU[q] may be referred to as the "discharge section D[q]-H to be determined." In addition, a series of processes performed in the inkjet printer 1, including the discharge state determination performed by the discharge state determination circuit 64 and the preparation process for the discharge state determination by the discharge state determination circuit 64, is referred to as the discharge state determination process.

[0018] The constant voltage generating circuit 66 generates a constant potential signal SVbs as shown in FIG. 7. The constant potential signal SVbs has a constant potential Vbs. The constant voltage generating circuit 66 generates Q constant potential signals SVbs corresponding to each head unit HU. Although omitted in FIG. 1 to avoid complication of the drawing, the constant voltage generating circuit 66 supplies the Q constant potential signals SVbs to each of the head units HU.

[0019] The switching circuit 10[q] switches whether or not to supply the drive signal Com[q] output from the drive signal generating circuit 62[q] to each discharge section D[q][m]. The switching circuit 10[q] also switches whether or not to electrically connect each discharge section D to the detection circuit 20.

[0020] The detection circuit 20[q] generates a residual vibration signal NSAS[q][m] indicating the residual vibration remaining in the ejection section D[q][m] after the ejection section D[q][m] is driven, based on the detection signal Vout[q][m] detected from the ejection section D[q][m] driven by the drive signal Com[q].

[0021] In this embodiment, it is assumed that the inkjet printer 1 is a serial printer. Specifically, as shown in Fig. 2, the inkjet printer 1 executes a printing process by ejecting ink from the ejection units D while transporting the recording paper P in the sub-scanning direction and moving the head module HM in the main scanning direction. In this embodiment, as shown in Fig. 2, the +X direction and the -X direction opposite the +X direction are the main scanning direction, and the +Y direction is the sub-scanning direction. Hereinafter, the +X direction and the -X direction are collectively referred to as the "X-axis direction", and the +Y direction and the -Y direction opposite the +Y direction are collectively referred to as the "Y-axis direction".

[0022] The transport mechanism 7 transports the recording paper P in the +Y direction. Specifically, the transport mechanism 7 includes a transport roller (not shown) whose rotation axis is parallel to the X-axis direction, and a motor (not shown) that rotates the transport roller under the control of the control module 6.

[0023] The movement mechanism 8 reciprocates the head module HM along the X-axis under the control of the control module 6. As illustrated in Fig. 2, the movement mechanism 8 includes a substantially box-shaped conveyor 82 that houses the head module HM, and an endless belt 81 to which the conveyor 82 is fixed.

[0024] The maintenance unit 4 executes a maintenance process for restoring the ink ejection state of the ejection portion D to normal when the ink ejection state of the ejection portion D becomes abnormal. The maintenance unit 4 includes a cap (not shown) for covering each head unit HU so that the nozzle N of the ejection portion D is sealed, a wiper (not shown) for wiping off foreign matter such as paper dust adhering to the vicinity of the nozzle N of the ejection portion D, a tube pump (not shown) for sucking ink, air bubbles, etc. in the ejection portion D, and a discharged ink receiving portion (not shown) for receiving the ink discharged when discharging the ink in the ejection portion D.

[0025] 2, the inkjet printer 1 is equipped with a liquid container 14 that stores ink. The liquid container 14 may be, for example, a cartridge that is detachable from the inkjet printer 1, a bag-shaped ink pack made of a flexible film, or an ink tank that can be refilled with ink. The liquid container 14 stores multiple types of ink with different colors.

[0026] The storage unit 61 includes a volatile memory such as RAM, and a non-volatile memory such as ROM, EEPROM, or PROM, and stores various information such as the print data Img supplied from the host computer and the control program for the inkjet printer 1. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. PROM is an abbreviation for Programmable ROM.

[0027] 1 and 2, the head unit HU is connected to the FFC 19. FFC is an abbreviation for Flexible Flat Cable. The FFC 19 includes wiring for supplying signals to each head unit HU, and wiring for supplying the residual vibration signal NSAS[q][m] supplied from each head unit HU to the ejection state determination circuit 64. The wiring for supplying signals to each head unit HU is, for example, a plurality of wirings for supplying a drive signal Com[q], a constant potential signal SVbs, and a designation signal SI to each head unit HU.

[0028] The designation signal SI is a digital signal for designating the type of operation of the ejection section D. Specifically, the designation signal SI designates whether or not to supply the drive signal Com to the ejection section D, thereby designating the type of operation of the ejection section D. Here, designating the type of operation of the ejection section D means, for example, designating whether or not to drive the ejection section D, designating whether or not ink is ejected from the ejection section D when the ejection section D is driven, and designating the amount of ink ejected from the ejection section D when the ejection section D is driven.

[0029] When the printing process is executed, the control unit 60 first stores the print data Img supplied from the host computer in the storage unit 61. Next, the control unit 60 generates various control signals such as a designation signal SI, a waveform designation signal dCom, a signal for controlling the transport mechanism 7, and a signal for controlling the movement mechanism 8 based on various data such as the print data Img stored in the storage unit 61. Then, the control unit 60 controls the head module HM to drive the ejection unit D while controlling the transport mechanism 7 and the movement mechanism 8 to change the relative position of the recording paper P with respect to the head module HM based on the various control signals. As a result, the control unit 60 adjusts the presence or absence of ink ejection from the ejection unit D, the amount of ink ejection, the timing of ink ejection, and the like, and controls the execution of the printing process to form an image corresponding to the print data Img on the recording paper P.

[0030] As described above, the inkjet printer 1 according to this embodiment executes an ejection state determination process to determine whether the ink ejection state from each ejection section D is normal, i.e., whether any ejection abnormalities have occurred in each ejection section D. An ejection abnormality is a state in which ink cannot be ejected in the manner defined by the drive signal Com even when the ejection unit D is driven by the drive signal Com to eject ink from the ejection unit D. Here, the ink ejection manner defined by the drive signal Com means that the ejection unit D ejects an amount of ink defined by the waveform of the drive signal Com, and the ejection unit D ejects ink at an ejection speed defined by the waveform of the drive signal Com. In other words, a state in which ink cannot be ejected in the ink ejection manner defined by the drive signal Com includes, in addition to a state in which ink cannot be ejected from the ejection unit D, a state in which an amount of ink smaller than the ink ejection amount defined by the drive signal Com is ejected from the ejection unit D, a state in which an amount of ink larger than the ink ejection amount defined by the drive signal Com is ejected from the ejection unit D, or a state in which ink cannot be landed at a desired landing position on the recording paper P because ink is ejected at a speed different from the ink ejection speed defined by the drive signal Com.

[0031] In the ejection state determination process, the inkjet printer 1 executes a series of processes, namely, a first process, a second process, a third process, a fourth process, and a fifth process, which are described below. In the first process, the control unit 60 selects an ejection section DH to be determined from among M ejection sections D provided in each head unit HU. In the second process, the control unit 60 drives the ejection section DH to be determined, thereby causing residual vibration in the ejection section DH to be determined. In the third process, the detection circuit 20 generates a residual vibration signal NSAS based on the detection signal Vout detected from the ejection section DH to be determined. In the fourth process, the ejection state determination circuit 64 performs an ejection state determination for the ejection section DH to be determined based on the residual vibration signal NSAS, and generates determination information Stt indicating the result of the determination. In the fifth process, the control unit 60 stores the determination information Stt in the storage unit 61.

[0032] As described above, the inkjet printer 1 according to this embodiment executes a maintenance process to restore the ink ejection state of an ejection unit D that has experienced an ejection abnormality to normal. Specifically, the maintenance process is a general term for processes such as a flushing process, a wiping process, and a pumping process, which are used to restore the ink ejection state of the ejection unit D to normal. The flushing process is a process for discharging ink from the ejection unit D. The wiping process is a process for wiping off foreign matter such as paper dust that has adhered to the vicinity of the nozzle N of the ejection unit D with a wiper. The pumping process is a process for sucking ink, air bubbles, etc., from within the ejection unit D with a tube pump.

[0033] Furthermore, as a printing process, the inkjet printer 1 according to this embodiment may execute a complementary printing process in which ink is ejected from an ejection section D that is in a normal ejection state instead of from an ejection section D that has become abnormal, thereby forming an image on recording paper P in accordance with the print data Img.

[0034] More specifically, the complementary printing process is a printing process in which, when an ejection abnormality occurs in one ejection unit D, instead of ejecting ink from the one ejection unit D, the amount of ink ejected from another ejection unit D different from the one ejection unit D is increased, thereby causing the other ejection unit D to complement the role of the one ejection unit D. Note that, hereinafter, printing processes other than the complementary printing process, i.e., printing processes that are executed without any ejection unit D complementing the other ejection units D, may be referred to as normal printing processes.

[0035] 1.2. Overview of the recording head HD and ejection section D The print head HD and the ejection sections D provided in the print head HD will be described with reference to FIGS.

[0036] FIG. 3 is a schematic partial cross-sectional view of the recording head HD, in which the recording head HD is cut so as to include a discharge portion D. As shown in FIG. 3, the ejection section D includes a piezoelectric element PZ, a cavity 320 filled with ink, a nozzle N communicating with the cavity 320, and a vibration plate 310. The cavity 320 is an example of a "pressure chamber." In the ejection section D, a drive signal Com is supplied to the piezoelectric element PZ, and the piezoelectric element PZ is driven by the drive signal Com, thereby ejecting ink in the cavity 320 from the nozzle N. The cavity 320 is a space defined by a cavity plate 340, a nozzle plate 330 in which the nozzle N is formed, and the vibration plate 310. The cavity 320 communicates with a reservoir 350 via an ink supply port 360. The reservoir 350 communicates with a liquid container 14 corresponding to the ejection section D via an ink intake port 370.

[0037] In this embodiment, the piezoelectric element PZ is of a unimorph type as shown in Fig. 3. Note that the piezoelectric element PZ is not limited to the unimorph type, and a bimorph type, a laminated type, or the like may also be used.

[0038] The piezoelectric element PZ has an upper electrode Zu, a lower electrode Zd, and a piezoelectric body Zm provided between the upper electrode Zu and the lower electrode Zd. When the lower electrode Zd is set to a constant potential Vbs and a drive signal Com is supplied to the upper electrode Zu, a voltage is applied between the upper electrode Zu and the lower electrode Zd, and the piezoelectric element PZ is displaced in the +Z direction or the -Z direction according to the applied voltage, and as a result of this displacement, the piezoelectric element PZ vibrates. The lower electrode Zd is an example of "one end of the piezoelectric element."

[0039] A vibration plate 310 is placed at the opening on the top surface of the cavity plate 340. A lower electrode Zd is bonded to the vibration plate 310. Therefore, when the piezoelectric element PZ is driven to vibrate by the drive signal Com, the vibration plate 310 also vibrates. The volume of the cavity 320 changes due to the vibration of the vibration plate 310, and the ink filled in the cavity 320 is ejected from the nozzle N. When the ink in the cavity 320 decreases due to the ejection of the ink, ink is supplied from the reservoir 350.

[0040] 4 to 6 are explanatory diagrams for explaining an example of the ink ejection operation in the ejection section D. As illustrated in Fig. 4, the control section 60 changes the potential of the drive signal Com supplied to the piezoelectric element PZ included in the ejection section D to generate a distortion that displaces the piezoelectric element PZ in the +Z direction, thereby bending the vibration plate 310 of the ejection section D in the +Z direction. As a result, as illustrated in Fig. 5, the volume of the cavity 320 of the ejection section D is expanded compared to the state illustrated in Fig. 4.

[0041] Next, the control unit 60 generates a distortion that displaces the piezoelectric element PZ in the -Z direction by changing the potential indicated by the drive signal Com, and deflects the vibration plate 310 of the ejection unit D in the -Z direction. As a result, as shown in Fig. 6, the volume of the cavity 320 contracts suddenly, and a part of the ink filling the cavity 320 is ejected as an ink droplet from the nozzle N communicating with the cavity 320. After the piezoelectric element PZ and the vibration plate 310 are driven by the drive signal Com and displaced in the Z-axis direction, residual vibration is generated in the ejection unit D including the vibration plate 310.

[0042] 1.3.FFC19 7 is a diagram showing the wiring arrangement of the FFC 19. The FFC 19 has two shield layers 193 and 194, a plurality of wirings 191, and an insulating layer 192. The two shield layers 193 and 194 are formed containing a conductive material such as aluminum or gold. The plurality of wirings 191 are provided between the shield layers 193 and 194, are formed containing a conductive material, and are provided for transmitting various signals. The insulating layer 192 is made of an insulating material and is provided between the shield layers 193 and 194 so as to cover the plurality of wirings 191.

[0043] In the example of FIG. 7, among the multiple wirings 191, a wiring 191-SI that transmits a designation signal SI, a wiring 191 that transmits a signal related to the head unit HU[q1], and a wiring 191 that transmits a signal related to the head unit HU[q2] are displayed. The signal related to the head unit HU[q] means a signal supplied to the head unit HU[q] and a signal acquired from the head unit HU[q]. The variable q1 can be an odd number from 1 to Q-1. The variable q2 is an integer obtained by adding 1 to the variable q1. Since the variable q1 is an odd number, the variable q2 can be an even number from 2 to Q.

[0044] The wiring 191 for transmitting signals related to the head unit HU[q1] includes a wiring 191-N[q1] for transmitting the residual vibration signal NSAS[q1], a wiring 191-V1[q1] for transmitting the constant voltage signal SVbs1[q1], a wiring 191-CA[q1] for transmitting the drive signal ComA[q1], a wiring 191-ComB[q1] for transmitting the drive signal ComB[q1], and a wiring 191-V2[q1] for transmitting the constant voltage signal SVbs2[q1]. The constant voltage signals SVbs1[q] and SVbs2[q] are supplied to the lower electrode Zd[q][m].

[0045] The wiring 191 transmitting signals related to the head unit HU[q2] includes wiring 191-N[q2] transmitting a residual vibration signal NSAS[q2], wiring 191-V1[q2] transmitting a constant voltage signal SVbs1[q2], wiring 191-CA[q2] transmitting a drive signal ComA[q2], wiring 191-CB[q2] transmitting a drive signal ComB[q2], and wiring 191-V2[q2] transmitting a constant voltage signal SVbs2[q2]. Note that wiring 191-CA[q] is an example of a "first wiring." Wiring 191-CB[q] is an example of a "second wiring." Wiring 191-V1[q] is an example of a "third wiring." Wiring 191-V2[q] is an example of a "fourth wiring." Wiring 191-SI is an example of a "control wiring." Wiring 191-N[q] is an example of a "detection wiring."

[0046] As illustrated in Fig. 7, the wiring 191-CA[q1] and the wiring 191-CB[q1] are arranged between the wiring 191-V1[q1] and the wiring 191-V2[q1]. Furthermore, in the example of Fig. 7, the wiring 191-SI and the wiring 191-N[q1] are arranged on the opposite side of the wiring 191-V2[q1] with respect to the wiring 191-V1[q1], and the wiring 191-N[q2] is arranged on the opposite side of the wiring 191-CB[q1] with respect to the wiring 191-V2[q1]. The multiple wirings 191 illustrated in Fig. 7 are arranged in the following order when described using the names of the signals transmitted by the wirings 191. SI-…-NSAS[q1]-SVbs1[q1]-ComA[q1]-ComB[q1]-SVbs2[q1]-NSAS[q2]-SVbs1[q2]-ComA[q2]-ComB[q2]-SVbs2[q2]

[0047] 1.4. Head unit HU configuration The configuration of each head unit HU will be described below with reference to FIG.

[0048] 8 is a block diagram showing an example of the configuration of the head unit HU[q]. As described above, the head unit HU[q] includes a recording head HD[q], a switching circuit 10[q], and a detection circuit 20[q]. The head unit HU[q] also includes an internal wiring LHa to which a drive signal ComA[q] is supplied from the drive signal generating circuit 62[q], an internal wiring LHb to which a drive signal ComB[q] is supplied from the drive signal generating circuit 62[q], and an internal wiring LHs for supplying a detection signal Vout detected from the discharge section D to the detection circuit 20[q].

[0049] 8, the switching circuit 10[q] includes M switches SWa[q][1] to SWa[q][M], M switches SWb[q][1] to SWb[q][M], M switches SWs[q][1] to SWs[q][M], and a connection state designation circuit 11 that designates the connection state of each switch. Each switch may be, for example, a transmission gate. Based on at least some of the signals of the designation signal SI, the latch signal LAT, the change signal CH, and the period designation signal Tsig[q] supplied from the control unit 60, the connection state designation circuit 11 generates, for each of the possible values ​​of variable m from 1 to M, a connection state designation signal SLa[q][m] that specifies the on / off state of switch SWa[q][m], a connection state designation signal SLb[q][m] that specifies the on / off state of switch SWb[q][m], and a connection state designation signal SLs[q][m] that specifies the on / off state of switch SWs[m].

[0050] The switch SWa[q][m] switches whether or not to electrically connect the internal wiring LHa to the upper electrode Zu[q][m] of the piezoelectric element PZ[q][m] provided in the discharge section D[q][m] in response to the connection state designation signal SLa[q][m]. For example, the switch SWa[q][m] is turned on when the connection state designation signal SLa[q][m] is at a high level, and turned off when the connection state designation signal SLa[q][m] is at a low level. The switch SWb[q][m] switches whether or not to electrically connect the internal wiring LHb to the upper electrode Zu[q][m] of the piezoelectric element PZ[q][m] provided in the discharge section D[q][m] according to the connection state designation signal SLb[q][m]. For example, the switch SWb[q][m] is turned on when the connection state designation signal SLb[q][m] is at a high level, and turned off when the connection state designation signal SLb[q][m] is at a low level. Of the drive signals ComA[q] and ComB[q], the signal that is actually supplied to the piezoelectric element PZ[q][m] of the ejection section D[q][m] via the switch SWa[q][m] or SWb[q][m] may be referred to as the supplied drive signal Vin[q][m].

[0051] The switch SWs[q][m] switches between electrically connecting or not connecting the internal wiring LHs and the upper electrode Zu[q][m] of the piezoelectric element PZ[q][m] provided in the discharge section D[q][m] according to the connection state designation signal SLs[q][m]. For example, the switch SWs[q][m] is turned on when the connection state designation signal SLs[q][m] is at a high level, and turned off when the connection state designation signal SLs[q][m] is at a low level.

[0052] The detection circuit 20[q] is supplied with a detection signal Vout[q][m] output from the piezoelectric element PZ[q][m] of the ejection section D[q][m] driven as the ejection section D[q]-H to be judged via the internal wiring LHs. The detection circuit 20[q] then generates a residual vibration signal NSAS based on the detection signal Vout[q][m].

[0053] 1.5. Operation of Head Unit HU Hereinafter, the operation of each head unit HU will be described with reference to FIGS.

[0054] In this embodiment, the operating period of the inkjet printer 1 includes one or more unit periods Tu. It is assumed that the inkjet printer 1 according to this embodiment performs either driving of each ejection section D in the printing process or driving of the ejection section DH to be judged in the ejection state judgment process and detecting residual vibration in each unit period Tu. However, this embodiment is not limited to this aspect, and it may be possible to perform both driving of each ejection section D in the printing process and driving of the ejection section DH to be judged in the ejection state judgment process and detecting residual vibration in each unit period Tu. Generally, an inkjet printer 1 forms an image represented by print data Img by repeatedly executing a printing process over a number of continuous or intermittent unit periods Tu to eject ink one or multiple times from each ejection section D. The inkjet printer 1 according to this embodiment also executes an ejection state determination process M times in M ​​continuous or intermittent unit periods Tu, thereby executing an ejection state determination process with each of the M ejection sections D[q][1] to D[q][M] as the ejection section DH to be determined.

[0055] Fig. 9 is a timing chart for explaining the operation in a unit period Tu of the inkjet printer 1. The example in Fig. 9 illustrates the drive signal ComA[q1], drive signal ComB[q1], and period designation signal Tsig[q1] supplied to the head unit HU[q1], and the drive signal ComA[q2], drive signal ComB[q2], and period designation signal Tsig[q2] supplied to the head unit HU[q2].

[0056] 9, the control unit 60 outputs a latch signal LAT having a pulse PlsL and a change signal CH having a pulse PlsC. As a result, the control unit 60 defines a unit period Tu as a period from the rising edge of the pulse PlsL to the rising edge of the next pulse PlsL. In addition, the control unit 60 divides the unit period Tu into three control periods Tu1, Tu2, and Tu3 by the pulse PlsC.

[0057] The designation signal SI includes individual designation signals Sd[q1][1] to Sd[q1][M] that designate the driving mode of the discharge sections D[q1][1] to D[q1][M] in each unit period Tu, and individual designation signals Sd[q2][1] to Sd[q2][M] that designate the driving mode of the discharge sections D[q2][1] to D[q2][M] in each unit period Tu. When at least one of the printing process and the discharge state determination process is executed in the unit period Tu, the control unit 60 supplies the designation signal SI including the individual designation signals Sd[q1][1] to Sd[q1][M] to the connection state designation circuit 11[q1] in synchronization with the clock signal CL prior to the start of the unit period Tu, as shown in FIG. In this case, the connection state designation circuit 11[q1] generates the connection state designation signals SLa[q1][m], SLb[q1][m], and SLs[q1][m] based on the individual designation signal Sd[q1][m] during the unit period Tu. Similarly, when at least one of the printing process and the discharge state determination process is executed during the unit period Tu, the control unit 60 supplies the designation signal SI including the individual designation signals Sd[q2][1] to Sd[q2][M] to the connection state designation circuit 11[q2] in synchronization with the clock signal CL prior to the start of the unit period Tu, as shown in FIG. In this case, the connection state designation circuit 11[q2] generates the connection state designation signals SLa[q2][m], SLb[q2][m], and SLs[q2][m] during the unit period Tu based on the individual designation signal Sd[q2][m].

[0058] The individual designation signal Sd[q][m] according to the present embodiment is a signal that designates one of four drive modes for the discharge section D[m] in each unit period Tu: discharge of an amount of ink corresponding to a large dot, discharge of an amount of ink corresponding to a small dot, non-discharge of ink, and drive as a determination target in the discharge state determination process. Hereinafter, the amount corresponding to a large dot may be referred to as a "large amount". Discharge of an amount of ink corresponding to a large dot may be referred to as "formation of a large dot". An amount corresponding to a small dot may be referred to as a "small amount". Discharge of an amount of ink corresponding to a small dot may be referred to as "formation of a small dot". Drive as a determination target in the discharge state determination process may be referred to as "drive as a determination target discharge section DH" or "drive as a determination target discharge section D[q]-H".

[0059] First, the driving signal Com[q1] will be described. As shown in FIG. 9, the driving signal generating circuit 62[q1] outputs a driving signal ComA[q1] having a large dot waveform Wd provided in the control period Tu1, a first micro vibration waveform WHb provided in the control period Tu2, and a judgment waveform Wk provided in the control period Tu3. Furthermore, the driving signal generating circuit 62[q1] outputs a driving signal ComB[q1] having a small dot waveform Ws provided in the control period Tu1, a second micro vibration waveform WLb provided in the control period Tu2, and a waveform W0 provided in the control period Tu3. The large dot waveform Wd, the first micro vibration waveform WHb, the judgment waveform Wk, the small dot waveform Ws, the second micro vibration waveform WLb, and the waveform W0 are set to the reference potential V0 at the start and end. In this embodiment, as an example, it is assumed that the individual designation signal Sd[q][m] is a 3-bit digital signal.

[0060] The large dot waveform Wd and the small dot waveform Ws will be described. The large dot waveform Wd is a waveform for forming a large dot. The small dot waveform Ws is a waveform for forming a small dot. In this embodiment, the designer of the inkjet printer 1 determines the large dot waveform Wd and the small dot waveform Ws so that the potential difference between the maximum potential VHd and the minimum potential VLd of the large dot waveform Wd is greater than the potential difference between the maximum potential VHs and the minimum potential VLs of the small dot waveform Ws. Specifically, when the discharge section D[q1][m] is driven by the drive signal ComA[q1] having the large dot waveform Wd, the large dot waveform Wd is determined so that an amount of ink equivalent to a large dot is discharged from the discharge section D[q1][m]. In addition, when the discharge section D[q1][m] is driven by the drive signal ComB[q1] having the small dot waveform Ws, the small dot waveform Ws is determined so that an amount of ink equivalent to a small dot is discharged from the discharge section D[q1][m].

[0061] When the individual designation signal Sd[q1][m] designates the formation of a large dot to the discharge section D[q1][m], the connection state designation circuit 11[q1] sets the connection state designation signal SLa[q1][m] to a high level in the control period Tu1, sets it to a low level in the control periods Tu2 and Tu3, and sets the connection state designation signals SLb[q1][m] and SLs[q1][m] to a low level in the unit period Tu. In this case, the discharge section D[q1][m] is driven by the drive signal ComA[q1] of the large dot waveform Wd in the control period Tu1 to discharge an amount of ink equivalent to a large dot. As a result, the discharge section D[q1][m] discharges an amount of ink equivalent to a large dot, and a large dot is formed on the recording paper P.

[0062] When the individual designation signal Sd[q1][m] designates the formation of a small dot to the discharge section D[q1][m], the connection state designation circuit 11[q1] sets the connection state designation signals SLa[q1][m] and SLs[q1][m] to a low level in the unit period Tu, sets the connection state designation signal SLb[q1][m] to a high level in the control period Tu1, and sets it to a low level in the control periods Tu2 and Tu3. In this case, the discharge section D[q1][m] is driven by the drive signal ComB[q1] of the small dot waveform Ws in the control period Tu1 to discharge an amount of ink corresponding to a small dot. As a result, the discharge section D[q1][m] discharges a small amount of ink, and a small dot is formed on the recording paper P.

[0063] The first micro vibration waveform WHb and the second micro vibration waveform WLb will be described. The first micro vibration waveform WHb and the second micro vibration waveform WLb are waveforms that drive the piezoelectric element PZ so that ink is not ejected from the ejection section D[q1][m]. Hereinafter, the first micro vibration waveform WHb and the second micro vibration waveform WLb are collectively referred to as "micro vibration waveforms". When the micro vibration waveform is supplied to the upper electrode Zu of the piezoelectric element PZ, the ink near the nozzle N vibrates and the increase in the viscosity of the ink can be suppressed. Even if the first micro vibration waveform WHb or the second micro vibration waveform WLb is supplied to the upper electrode Zu of the piezoelectric element PZ, ink is not ejected from the nozzle N corresponding to the piezoelectric element PZ. As shown in FIG. 9, the absolute value of the potential difference dVH obtained by subtracting the reference potential V0 from the maximum potential VHb of the first micro vibration waveform WHb is approximately the same as the absolute value of the potential difference dVL obtained by subtracting the reference potential V0 from the minimum potential VLb of the second micro vibration waveform WLb. The term "substantially the same" includes not only being completely the same, but also being considered to be the same when at least one of manufacturing errors and errors due to noise is taken into consideration.

[0064] When the individual designation signal Sd[q1][m] designates the discharge section D[q1][m] to not discharge ink, the connection state designation circuit 11[q1] selects one of the first and second setting modes shown below, and vibrates the ink near the nozzle N. In the first setting mode, the connection state designation circuit 11[q1] sets the connection state designation signal SLa[q1][m] to a high level in the control period Tu2, sets it to a low level in the control periods Tu1 and Tu3, and sets the connection state designation signals SLb[q1][m] and SLs[q1][m] to a low level in the unit period Tu. As a result, the discharge section D[q1][m] is driven by the drive signal ComB[q1] of the first vibration waveform WHb in the control period Tu2, and vibrates the ink near the nozzle N. In the second setting mode, the connection state designation circuit 11[q1] sets the connection state designation signal Slb[q1][m] to a high level in the control period Tu2, sets it to a low level in the control periods Tu1 and Tu3, and sets the connection state designation signals Sla[q1][m] and Sls[q1][m] to a low level in the unit period Tu. As a result, the ejection section D[q1][m] is driven by the drive signal ComB[q1] of the second micro-vibration waveform WLb in the control period Tu2, and micro-vibrates the ink near the nozzle N.

[0065] Regarding the selection of the first setting mode or the setting mode, the connection state designation circuit 11[q1] sets the connection state designation signals SLa[q1][m], SLb[q1][m], and SLs[q1][m] based on the individual designation signal Sd[q1][m], for example, so that the number of ejection units D for which the first setting mode is selected approaches the same number as the number of ejection units D for which the second setting mode is selected. Specifically, it is assumed that non-ejection of ink is designated for all ejection units D[q1][1] to D[q1][M] in a certain unit period Tu. The connection state designation circuit 11[q1] sets connection state designation signals SLa[q1][m], SLb[q1][m], and SLs[q1][m] in a first setting mode for discharge sections D[q1][m] where the variable m is an odd number, and sets connection state designation signals SLa[q1][m], SLb[q1][m], and SLs[q1][m] in a second setting mode for discharge sections D[q1][m] where the variable m is an even number.

[0066] The determination waveform Wk will be described. The determination waveform Wk is a waveform that drives the piezoelectric element PZ as a determination target in the discharge state determination process. When a drive signal ComB[q1] having the determination waveform Wk is supplied to the discharge section D[q1][m], the designer of the inkjet printer 1 determines the waveform of the determination waveform Wk so that the discharge section D[q1][m] is driven to such an extent that ink is not discharged from the discharge section D[q1][m]. Specifically, the designer of the inkjet printer 1 determines the determination waveform Wk so that the potential difference between the maximum potential VHk and the minimum potential VLk of the determination waveform Wk is smaller than the potential difference between the maximum potential VHs and the minimum potential VLs of the small dot waveform Ws. Furthermore, the control unit 60 outputs a period designation signal Tsig[q1] having a pulse PlsT1 and a pulse PlsT2 in the control period Tu3. As a result, the control unit 60 divides the control period Tu3 into a control period TSS1 from the start of the pulse PlsC to the start of the pulse PlsT1, a control period TSS2 from the start of the pulse PlsT1 to the start of the pulse PlsT2, and a control period TSS3 from the start of the pulse PlsT2 to the start of the pulse PlsL.

[0067] When the individual designation signal Sd[q1][m] designates the emission section D[q1][m] as the emission section Dh to be judged, the connection state designation circuit 11[q1] sets the connection state designation signal Sla[q1][m] to a low level during control periods Tu1, Tu2, and TSS2, and to a high level during control periods TSS1 and TSS3, sets the connection state designation signal SLb[q1][m] to a low level during the unit period Tu, and sets the connection state designation signal SLs[q1][m] to a low level during control periods TSS1 and TSS3, and to a high level during control period TSS2. In this case, the ejection section D[q1]-H to be judged is driven by the drive signal ComA[q1] of the judgment waveform Wk during the control period TSS1. Specifically, the piezoelectric element PZ of the ejection section D[q1]-H to be judged is displaced by the drive signal ComA[q1] of the judgment waveform Wk during the control period TSS1. As a result, vibration occurs in the ejection section DH to be judged, and this vibration remains in the control period TSS2. Then, during the control period TSS2, the upper electrode Zu of the piezoelectric element PZ of the ejection section D[q1]-H to be judged changes its potential according to the residual vibration occurring in the ejection section D[q1]-H to be judged. In other words, during the control period TSS2, the upper electrode Zu of the piezoelectric element PZ of the ejection section D[q1]-H to be judged shows a potential according to the electromotive force of the piezoelectric element PZ caused by the residual vibration occurring in the ejection section D[q1]-H to be judged. The potential of the upper electrode Zu can be detected as a detection signal Vout during the control period TSS2.

[0068] The potential of the waveform W0 does not fluctuate from the reference potential V0 from the start to the end. By providing the waveform W0 at the same timing as the determination waveform Wk, it is possible to suppress noise caused by the drive signal ComB[q1] from occurring in the detection signal Vout detected during the control period TSS2.

[0069] Next, the driving signal Com[q2] will be described. As shown in Fig. 9, the driving signal generating circuit 62[q2] outputs a driving signal ComA[q2] having a large dot waveform Wd provided in the control period Tu1, a determination waveform Wk provided in the control period Tu2, and a first minute vibration waveform WHb provided in the control period Tu3. Furthermore, the driving signal generating circuit 62[q2] outputs a driving signal ComB[q2] having a small dot waveform Ws provided in the control period Tu1, a waveform W0 provided in the control period Tu2, and a second minute vibration waveform WLb provided in the control period Tu3.

[0070] When the individual designation signal Sd[q2][m] designates the formation of a large dot to the discharge section D[q2][m], the connection state designation circuit 11[q2] sets the connection state designation signal SLa[q2][m] to a high level in the control period Tu1, sets it to a low level in the control periods Tu2 and Tu3, and sets the connection state designation signals SLb[q2][m] and SLs[q2][m] to a low level in the unit period Tu. In this case, the discharge section D[q2][m] is driven by the drive signal ComA[q2] of the large dot waveform Wd in the control period Tu1 to discharge an amount of ink equivalent to a large dot. As a result, the discharge section D[q2][m] discharges an amount of ink equivalent to a large dot, and a large dot is formed on the recording paper P.

[0071] When the individual designation signal Sd[q2][m] designates the formation of a small dot to the discharge section D[q2][m], the connection state designation circuit 11[q2] sets the connection state designation signals SLa[q2][m] and SLs[q2][m] to a low level in the unit period Tu, sets the connection state designation signal SLb[q2][m] to a high level in the control period Tu1, and sets it to a low level in the control periods Tu2 and Tu3. In this case, the discharge section D[q2][m] is driven by the drive signal ComB[q2] of the small dot waveform Ws in the control period Tu1 to discharge an amount of ink corresponding to a small dot. As a result, the discharge section D[q2][m] discharges a small amount of ink, and a small dot is formed on the recording paper P.

[0072] When the individual designation signal Sd[q2][m] designates the discharge section D[q2][m] to not discharge ink, the connection state designation circuit 11[q2] selects one of the third and fourth setting modes shown below, and vibrates the ink near the nozzle N. In the third setting mode, the connection state designation circuit 11[q2] sets the connection state designation signal SLa[q2][m] to a high level in the control period Tu3, sets it to a low level in the control periods Tu1 and Tu2, and sets the connection state designation signals SLb[q2][m] and SLs[q2][m] to a low level in the unit period Tu. As a result, the discharge section D[q2][m] is driven by the drive signal ComA[q2] of the first vibration waveform WHb in the control period Tu3, and vibrates the ink near the nozzle N. In the fourth setting mode, the connection state designation circuit 11[q2] sets the connection state designation signal Slb[q2][m] to a high level in the control period Tu3, sets it to a low level in the control periods Tu1 and Tu3, and sets the connection state designation signals Sla[q2][m] and Sls[q2][m] to a low level in the unit period Tu. As a result, the ejection section D[q2][m] is driven by the drive signal ComB[q2] of the second micro-vibration waveform WLb in the control period Tu3, and micro-vibrates the ink near the nozzle N.

[0073] The control unit 60 outputs a period designation signal Tsig[q2] having a pulse PlsT1 and a pulse PlsT2 in the control period Tu2. As a result, the control unit 60 divides the control period Tu2 into a control period TSS4 from the start of the pulse PlsC to the start of the pulse PlsT1, a control period TSS5 from the start of the pulse PlsT1 to the start of the pulse PlsT2, and a control period TSS6 from the start of the pulse PlsT2 to the start of the next pulse PlsC. When the individual designation signal Sd[q2][m] designates the emission section D[q2][m] as the emission section Dh to be judged, the connection state designation circuit 11[q2] sets the connection state designation signal Sla[q2][m] to a low level in the control periods Tu1, Tu3, and TSS5, and to a high level in the control periods TSS4 and TSS6, sets the connection state designation signal SLb[q2][m] to a low level in the unit period Tu, and sets the connection state designation signal SLs[q2][m] to a low level in the control periods TSS4 and TSS6, and to a high level in the control period TSS5. In this case, the ejection section D[q2]-H to be judged is driven by the drive signal ComA[q2] of the judgment waveform Wk during the control period TSS4. Specifically, the piezoelectric element PZ of the ejection section D[q2]-H to be judged is displaced by the drive signal ComA[q2] of the waveform WS during the control period TSS4. As a result, vibration occurs in the ejection section D[q2]-H to be judged, and this vibration remains in the control period TSS5. Then, during the control period TSS5, the upper electrode Zu of the piezoelectric element PZ of the ejection section D[q2]-H to be judged changes its potential according to the residual vibration occurring in the ejection section D[q2]-H to be judged. Then, the potential of the upper electrode Zu can be detected as a detection signal Vout during the control period TSS5.

[0074] The first micro-vibration waveform WHb and the second micro-vibration waveform WLb will be described in more detail with reference to FIG.

[0075] FIG. 10 is an explanatory diagram showing the first micro vibration waveform WHb and the second micro vibration waveform WLb. In the example of FIG. 10, the first micro vibration waveform WHb of the driving signal ComA[q1] in the control period Tu2 and the second micro vibration waveform WLb of the driving signal ComB[q1] in the control period Tu2 are shown. The control period Tu2 is divided into a period T1, a period T2 following the period T1, a period T3 following the period T2, a period T4 following the period T3, and a period T5 following the period T4. In the period T1, the driving signal ComA[q1] is held at the reference potential V0. In the period T2, the driving signal ComA[q1] transitions from the reference potential V0 to the highest potential VHb. The highest potential VHb is higher than the reference potential V0. In the period T3, the driving signal ComA[q1] is held at the highest potential VHb. In a period T4, the driving signal ComA[q1] transitions from the highest electric potential VHb to the reference electric potential V0. In a period T5, the driving signal ComA[q1] is held at the reference electric potential V0. Similarly, in the period T1, the driving signal ComB[q1] is held at the reference potential V0. In the period T2, the driving signal ComB[q1] transitions from the reference potential V0 to the minimum potential VLb. The minimum potential VLb is lower than the reference potential V0. In the period T3, the driving signal ComB[q1] is held at the minimum potential VLb. In the period T4, the driving signal ComB[q1] transitions from the minimum potential VLb to the reference potential V0. In the period T5, the driving signal ComB[q1] is held at the reference potential V0. That is, in this embodiment, the timing of the potential change in the first micro-vibration waveform WHb and the timing of the potential change in the second micro-vibration waveform WLb are substantially the same. The driving signal ComA[q1] is an example of a "first driving signal." The driving signal ComB[q1] is an example of a "second driving signal." The piezoelectric element PZ[q1][m1] driven in response to the supply of the driving signal ComA[q1] is an example of a "first piezoelectric element," and the piezoelectric element PZ[q1][m2] driven in response to the supply of the driving signal ComB[q1] is an example of a "second piezoelectric element." The variable m1 is an integer from 1 to M. The variable m2 is an integer from 1 to M and is different from the variable m1. The discharge section D[q1][m1] having the piezoelectric element PZ[q1][m1] is an example of a "first discharge section," the cavity 320 of the discharge section D[q1][m1] is an example of a "first pressure chamber," and the nozzle N of the discharge section D[q1][m1] is an example of a "first nozzle." The switch SWa[q1][m1] that switches whether or not the wiring 191-CA[q1] and the discharge section D[q1][m1] are electrically connected is an example of a "first switch". The switch SWb[q1][m2] that switches whether or not the wiring 191-CB[q1] and the discharge section D[q1][m2] are electrically connected is an example of a "second switch". The discharge section D[q1][m2] having the piezoelectric element PZ[q1][m2] is an example of a "second discharge section", the cavity 320 of the discharge section D[q1][m2] is an example of a "second pressure chamber", and the nozzle N of the discharge section D[q1][m2] is an example of a "second nozzle". Furthermore, the head unit HU[q1] is an example of a "first head unit", and the head unit HU[q2] is an example of a "second head unit". The drive signals ComA[q2] and ComB[q2] are an example of a "third drive signal," and the piezoelectric element PZ[q2][m] driven in response to the supply of the drive signal ComA[q2] or ComB[q2] is an example of a "third piezoelectric element." The detection circuit 20[q2] detects vibrations generated in the piezoelectric element [q2][m3] as the piezoelectric element PZ[q2][m3] is driven by the drive signal ComA[q2] or the drive signal ComB[q2], and outputs the detection result as a residual vibration signal NSAS[q2][m3], and is an example of a "detection unit." The period T2 is an example of a “first period” and a “fourth period”, the period T3 is an example of a “second period” and a “fifth period”, and the period T4 is an example of a “third period” and a “sixth period”. The reference potential V0 is an example of a “first potential” and a “third potential”, the highest potential VHb is an example of a “second potential”, and the lowest potential VLb is an example of a “fourth potential”. In addition, the drive signal ComA[q2] is also an example of a "first drive signal." When the drive signal ComA[q2] is an example of a "first drive signal," the drive signal ComB[q2] is an example of a "second drive signal," the piezoelectric element PZ[q2][m3] driven in response to the supply of the drive signal ComA[q2] is an example of a "first piezoelectric element," and the piezoelectric element PZ[q2][m4] driven in response to the supply of the drive signal ComB[q2] is an example of a "second piezoelectric element." The variable m3 is an integer from 1 to M. The variable m4 is an integer from 1 to M, and is an integer different from the variable m3. Furthermore, the discharge section D[q2][m3] having the piezoelectric element PZ[q2][m3] is an example of a "first discharge section," the cavity 320 of the discharge section D[q2][m3] is an example of a "first pressure chamber," and the nozzle N of the discharge section D[q2][m3] is an example of a "first nozzle." The switch SWa[q2][m3], which switches whether or not the wiring 191-CA[q2] and the discharge section D[q2][m3] are electrically connected, is an example of a "first switch". The switch SWb[q2][m4], which switches whether or not the wiring 191-CB[q2] and the discharge section D[q2][m4] are electrically connected, is an example of a "second switch". The discharge section D[q2][m4] having the piezoelectric element PZ[q2][m4] is an example of a "second discharge section", the cavity 320 of this discharge section D[q2][m4] is an example of a "second pressure chamber", and the nozzle N of this discharge section D[q2][m4] is an example of a "second nozzle". Furthermore, the head unit HU[q2] is an example of a "first head unit", and the head unit HU[q1] is an example of a "second head unit". The drive signals ComA[q1] and ComB[q1] are an example of a “third drive signal”, and the piezoelectric element PZ[q1][m] driven in response to the supply of the drive signal ComA[q1] or ComB[q1] is an example of a “third piezoelectric element”. The detection circuit 20[q1] detects vibrations generated in the piezoelectric element [q1][m1] as the piezoelectric element PZ[q1][m1] is driven by the drive signal ComA[q1] or the drive signal ComB[q1], and outputs the detection result as a residual vibration signal NSAS[q1][m1], and is an example of a “detection unit”.

[0076] 11 is an explanatory diagram for explaining the operation of the switching circuit 10 in the unit period Tu. In the following, the switches SWa, SWb, and SWs provided corresponding to the judgment target discharge section D[q]-H may be referred to as switches SWa[q]-H, SWb[q]-H, and SWs[q]-H, respectively. In the following, the discharge section D[q][m] driven in the printing process may be referred to as the print driving discharge section D[q]-P, and the switches SWa, SWb, and SWs provided corresponding to the print driving discharge section D[q]-P may be referred to as switches SWa[q]-P, SWb[q]-P, and SWs[q]-P, respectively.

[0077] First, the head unit HU[q1] will be described. As shown in Fig. 11, when the discharge section D[q1][m] operates as the print driving discharge section D[q1]-P in the unit period Tu, the discharge section D[q1][m] is driven according to the individual designation signal Sd[q1][m] and is used for the printing process. 11, when the discharge unit D[q1][m] operates as the discharge unit D[q1]-H to be judged in the unit period Tu, the switch SWa[q1][m], which is the switch SWa[q1]-H, is turned on in the control periods TSS1 and TSS3, the switch SWb[q1][m], which is the switch SWb[q1]-H, is turned off over the unit period Tu, and the switch SWs[q1][m], which is the switch SWs[q1]-H, is turned on in the control period TSS2. In this case, the piezoelectric element PZ[q1][m] of the discharge unit D[q1][m], which is the discharge unit D[q1]-H to be judged, is driven and displaced by the drive signal ComA[q1] in the control period TSS1, and a state in which residual vibration occurs in the discharge unit D[q1][m] in the control period TSS2 is created. During the control period TSS2, a detection signal Vout[q1][m] based on the residual vibration in the discharge section D[q1][m] is supplied to the detection circuit 20[q1] via the internal wiring LHs.

[0078] Next, the head unit HU[q2] will be described. As shown in Fig. 11, when the discharge section D[q2][m] operates as the print driving discharge section D[q2]-P in the unit period Tu, the discharge section D[q2][m] is driven according to the individual designation signal Sd[q2][m] and is used for the printing process. 11, when the discharge unit D[q2][m] operates as the discharge unit D[q2]-H to be judged in the unit period Tu, the switch SWa[q2][m], which is the switch SWa[q2]-H, is turned on in the control periods TSS4 and TSS6, the switch SWb[q2][m], which is the switch SWb[q2]-H, is turned off over the unit period Tu, and the switch SWs[q2][m], which is the switch SWs[q2]-H, is turned on in the control period TSS5. In this case, the piezoelectric element PZ[q2][m] of the discharge unit D[q2][m], which is the discharge unit D[q2]-H to be judged, is driven and displaced by the drive signal ComA[q2] in the control period TSS4, and a state in which residual vibration occurs in the discharge unit D[q2][m] in the control period TSS5 is created. During the control period TSS5, a detection signal Vout[q2][m] based on the residual vibration in the discharge section D[q2][m] is supplied to the detection circuit 20[q2] via the internal wiring LHs.

[0079] Fig. 12 is a diagram showing an example of the configuration of the connection state designation circuit 11[q] according to this embodiment. As shown in Fig. 10, the connection state designation circuit 11[q] generates connection state designation signals SLa[q][1] to SLa[q][M], SLb[q][1] to SLb[q][M], and SLs[q][1] to SLs[q][M]. Specifically, the connection state designation circuit 11 has transfer circuits SR[q][1] to SR[q][M], latch circuits LT[q][1] to LT[q][M], and decoders DC[q][1] to DC[q][M] in one-to-one correspondence with the discharge sections D[q][1] to D[q][M]. Among these, an individual designation signal Sd[q][m] is supplied to the transfer circuit SR[q][m]. Note that FIG. 12 illustrates a case in which the individual designation signals Sd[q][1] to Sd[q][M] are supplied serially, and for example, the individual designation signal Sd[q][m] corresponding to the mth stage is transferred in sequence from the transfer circuit SR[q][1] to the transfer circuit SR[q][m] in synchronization with the clock signal CL. The latch circuit LT[q][m] latches the individual designation signal Sd[q][m] supplied to the transfer circuit SR[q][m] at the timing when the pulse PlsL of the latch signal LAT rises to a high level. The decoder DC[q][m] generates the connection state designation signals SLa[q][m], SLb[q][m], and SLs[q][m] based on the individual designation signal Sd[q][m], the latch signal LAT, the change signal CH, and the period designation signal Tsig[q].

[0080] 13 is an explanatory diagram for explaining the generation of the connection state designation signals SLa[q1][m], SLb[q1][m], and SLs[q1][m] in the decoder DC[q1][m]. The decoder DC[q1][m] decodes the individual designation signal Sd[q1][m] according to FIG. 13, and generates the connection state designation signals SLa[q1][m], SLb[q1][m], and SLs[q1][m].

[0081] As shown in Figure 13, the individual designation signal Sd[q1][m] in this embodiment indicates any one of the following values: a value (1,1,0) that specifies the formation of a large dot, a value (1,0,0) that specifies the formation of a small dot, a value (0,1,1) that specifies the first micro-vibration waveform WHb, a value (0,0,1) that specifies the second micro-vibration waveform WLb, or a value (1,1,1) that specifies driving of the ejection section D[q1]-H to be judged. Then, when the individual designation signal Sd[q1][m] is (1,1,0), the decoder DC[q1][m] sets the connection state designation signal SLa[q1][m] to a high level in the control period Tu1. When the individual designation signal Sd[q1][m] indicates (1,0,0), the decoder DC[q1][m] sets the connection state designation signal SLb[q1][m] to a high level in the control period Tu1. When the individual designation signal Sd[q1][m] indicates (0,1,1), the decoder DC[q1][m] sets the connection state designation signal SLa[q1][m] to a high level in the control period Tu2. When the individual designation signal Sd[q1][m] indicates (0,0,1), the decoder DC[q1][m] sets the connection state designation signal SLb[q1][m] to a high level in the control period Tu2. When the individual designation signal Sd[q1][m] indicates (1,1,1), the decoder DC[q1][m] sets the connection state designation signal SLa[m] to a high level in the control periods TSS1 and TSS3, and sets the connection state designation signal SLs[q1][m] to a high level in the control period TSS2. When the above does not apply, the decoder DC[q1][m] sets each signal to a low level.

[0082] Fig. 14 is an explanatory diagram for explaining the generation of the connection state designation signals SLa[q2][m], SLb[q2][m], and SLs[q2][m] in the decoder DC[q2][m]. The decoder DC[q2][m] decodes the individual designation signal Sd[q2][m] according to Fig. 14, and generates the connection state designation signals SLa[q2][m], SLb[q2][m], and SLs[q2][m].

[0083] As shown in Figure 14, the individual designation signal Sd[q2][m] in this embodiment indicates any one of the following values: a value (1,1,0) that specifies the formation of a large dot, a value (1,0,0) that specifies the formation of a small dot, a value (0,1,1) that specifies the first micro-vibration waveform WHb, a value (0,0,1) that specifies the second micro-vibration waveform WLb, or a value (1,1,1) that specifies driving of the ejection section D[q2]-H to be judged. Then, when the individual designation signal Sd[q2][m] is (1,1,0), the decoder DC[q2][m] sets the connection state designation signal SLa[q2][m] to a high level in the control period Tu1. When the individual designation signal Sd[q2][m] indicates (1,0,0), the decoder DC[q2][m] sets the connection state designation signal SLb[q2][m] to a high level in the control period Tu1. When the individual designation signal Sd[q2][m] indicates (0,1,1), the decoder DC[q2][m] sets the connection state designation signal SLa[q2][m] to a high level in the control period Tu3. When the individual designation signal Sd[q2][m] indicates (0,0,1), the decoder DC[q2][m] sets the connection state designation signal SLb[q2][m] to a high level in the control period Tu3. When the individual designation signal Sd[q2][m] indicates (1,1,1), the decoder DC[q2][m] sets the connection state designation signal SLa[m] to a high level in the control periods TSS4 and TSS6, and sets the connection state designation signal SLs[q2][m] to a high level in the control period TSS5. When the above does not apply, the decoder DC[q2][m] sets each signal to a low level.

[0084] As described above, the detection circuit 20[q] generates a residual vibration signal NSAS based on the detection signal Vout. The residual vibration signal NSAS is a signal obtained by amplifying the amplitude of the detection signal Vout and removing noise components from the detection signal Vout, thereby shaping the detection signal Vout into a waveform suitable for processing in the discharge state determination circuit 64. The detection circuit 20[q] may be configured to include, for example, a negative feedback amplifier for amplifying the detection signal Vout, a low-pass filter for attenuating high frequency components of the detection signal Vout, and a voltage follower for converting impedance and outputting a low impedance residual vibration signal NSAS.

[0085] 1.6. Discharge state determination circuit 64 Next, the ejection state determination circuit 64 will be described.

[0086] Generally, the residual vibration occurring in the ejection section D has a natural vibration frequency determined by the shape of the nozzle N, the weight of the ink filled in the cavity 320, the viscosity of the ink filled in the cavity 320, and the like. In addition, in general, when an ejection abnormality occurs in the ejection part D because air bubbles are mixed in the cavity 320 of the ejection part D, the frequency of the residual vibration is higher than when air bubbles are not mixed in the cavity 320. In general, when an ejection abnormality occurs in the ejection part D because a foreign object such as paper powder adheres to the vicinity of the nozzle N of the ejection part D, the frequency of the residual vibration is lower than when no foreign object adheres. In general, when an ejection abnormality occurs in the ejection part D because the ink filled in the cavity 320 of the ejection part D is thickened, the frequency of the residual vibration is lower than when the ink is not thickened. In general, when an ejection abnormality occurs in the ejection part D because the ink filled in the cavity 320 of the ejection part D is thickened, the frequency of the residual vibration is lower than when a foreign object such as paper powder adheres to the vicinity of the nozzle N of the ejection part D. In general, when an ejection abnormality occurs in the ejection section D because the cavity 320 of the ejection section D is not filled with ink, or when an ejection abnormality occurs in the ejection section D because the piezoelectric element PZ has broken down and cannot be displaced, the amplitude of the residual vibration becomes smaller.

[0087] As described above, the residual vibration signal NSAS shows a waveform corresponding to the residual vibration occurring in the ejection section DH to be judged. Specifically, the residual vibration signal NSAS shows a frequency corresponding to the frequency of the residual vibration occurring in the ejection section DH to be judged, and shows a frequency corresponding to the amplitude of the residual vibration occurring in the ejection section DH to be judged. Therefore, the ejection state judgment circuit 64 can perform an ejection state judgment that judges the ejection state of the ink in the ejection section DH to be judged based on the residual vibration signal NSAS.

[0088] In judging the ejection state, the ejection state judgment circuit 64 measures the time length NTc of one period of the residual vibration signal NSAS, and generates period information Info-T indicating the measurement result. In addition, the discharge state determination circuit 64 generates amplitude information Info-S indicating whether the residual vibration signal NSAS has a predetermined amplitude in the discharge state determination. Specifically, the discharge state determination circuit 64 determines whether the potential of the residual vibration signal NSAS is equal to or higher than a threshold potential Vth-O that is higher than the potential Vth-C of the amplitude center level of the residual vibration signal NSAS and is equal to or lower than a threshold potential Vth-U that is lower than the potential Vth-C during the period in which the time length NTc of one cycle of the residual vibration signal NSAS is measured. If the result of the determination is positive, the amplitude information Info-S is set to a value indicating that the residual vibration signal NSAS has a predetermined amplitude, for example, "1", and if the result of the determination is negative, the amplitude information Info-S is set to a value indicating that the residual vibration signal NSAS does not have a predetermined amplitude, for example, "0". Then, the ejection state determination circuit 64 generates determination information Stt that indicates the determination result of the ink ejection state in the ejection section DH to be determined, based on the period information Info-T and the amplitude information Info-S.

[0089] FIG. 15 is an explanatory diagram for explaining the generation of the determination information Stt in the discharge state determination circuit 64. As shown in FIG. As shown in Figure 15, the ejection state judgment circuit 64 judges the ejection state in the ejection section DH to be judged by comparing the time length NTc indicated by the period information Info-T with some or all of the threshold values ​​Tth1, Tth2, and Tth3, and generates judgment information Stt indicating the result of the judgment. Here, the threshold value Tth1 is a value for indicating the boundary between the time length of one cycle of the residual vibration when the ejection state of the ejection unit D-H to be determined is normal and the time length of one cycle of the residual vibration when bubbles are mixed into the cavity 320. Further, the threshold value Tth2 is a value for indicating the boundary between the time length of one cycle of the residual vibration when the ejection state of the ejection unit D-H to be determined is normal and the time length of one cycle of the residual vibration when foreign matter adheres near the nozzle N. Further, the threshold value Tth3 is a value for indicating the boundary between the time length of one cycle of the residual vibration when foreign matter adheres near the nozzle N of the ejection unit D-H to be determined and the time length of one cycle of the residual vibration when the ink in the cavity 320 thickens. Note that the threshold values Tth1 to Tth3 are to satisfy "Tth1 < Tth2 < Tth3".

[0090] As shown in FIG. 15, in the present embodiment, when the value of the amplitude information Info-S is "1" and the time length NTc indicated by the period information Info-T satisfies "Tth1 ≦ NTc ≦ Tth2", it is regarded that the ink ejection state in the ejection unit D-H to be determined is normal. And in this case, the ejection state determination circuit 64 sets a value "1" indicating that the ejection state of the ejection unit D-H to be determined is normal in the determination information Stt. Further, when the value of the amplitude information Info-S is "1" and the time length NTc indicated by the period information Info-T satisfies "NTc < Tth1", it is regarded that ejection abnormality due to bubbles has occurred in the ejection unit D-H to be determined. And in this case, the ejection state determination circuit 64 sets a value "2" indicating that ejection abnormality due to bubbles has occurred in the ejection unit D-H to be determined in the determination information Stt. Further, when the value of the amplitude information Info-S is "1" and the time length NTc indicated by the period information Info-T satisfies "Tth2 < NTc ≦ Tth3", it is regarded that ejection abnormality due to foreign matter adhesion has occurred in the ejection unit D-H to be determined. And in this case, the ejection state determination circuit 64 sets a value "3" indicating that ejection abnormality due to foreign matter adhesion has occurred in the ejection unit D-H to be determined in the determination information Stt. Also, when the value of the amplitude information Info-S is "1" and the time length NTc indicated by the period information Info-T satisfies "Tth3 < NTc", it is considered that a discharge abnormality due to thickening has occurred in the discharge unit D-H to be determined. And in this case, the discharge state determination circuit 64 sets a value "4", which indicates that a discharge abnormality due to thickening has occurred in the discharge unit D-H to be determined, in the determination information Stt. Also, even when the value of the amplitude information Info-S is "0", it is considered that a discharge abnormality has occurred in the discharge unit D-H to be determined. And in this case, the discharge state determination circuit 64 sets a value "5", which indicates that a discharge abnormality has occurred in the discharge unit D-H to be determined, in the determination information Stt. As described above, the discharge state determination circuit 64 generates the determination information Stt based on the period information Info-T and the amplitude information Info-S.

[0091] Then, the control unit 60 associates the determination information Stt generated by the discharge state determination circuit 64 with the stage number q and the stage number m of the discharge unit D[q]-H corresponding to the determination information Stt, and stores it in the storage unit 61. Thereby, the control unit 60 manages the determination information Stt[q][1] to Stt[q][M] corresponding to the discharge units D[q][1] to D[q][M]. Note that, in the present embodiment, a case where the determination information Stt is 5-value information from "1" to "5" is illustrated. However, the determination information Stt may be 2-value information indicating whether the time length NTc satisfies "Tth1 ≦ NTc ≦ Tth2". At least, the determination information Stt may include information indicating whether the ink discharge state in the discharge unit D-H to be determined is normal.

[0092] 1.8. Summary of the Embodiment As described above, the inkjet printer 1 in this embodiment has a piezoelectric element PZ[q1][m1] that is driven in response to the supply of a drive signal ComA[q1], and a piezoelectric element PZ[q1][m2] that is driven in response to the supply of a drive signal ComB[q1]. The drive signal ComA[q1] in the control period Tu2 transitions from the reference potential V0 to the highest potential VHb in the period T2, maintains the highest potential VHb in the period T3 following the period T2, and transitions from the highest potential VHb to the reference potential V0 in the period T4 following the period T3. The drive signal ComB[q1] in the control period Tu2 transitions from the reference potential V0 to the lowest potential VLb in the period T2, maintains the lowest potential VLb in the period T3 following the period T2, and transitions from the lowest potential VLb to the reference potential V0 in the period T4 following the period T3. The highest potential VHb is a higher potential than the reference potential V0, and the lowest potential VLb is a lower potential than the reference potential V0. Generally, a change in the potential inside a conductor changes the magnetic field around the conductor, and an induced current due to electromagnetic induction is generated in other conductors placed in this magnetic field. This induced current may become noise and affect the signals transmitted by other conductors. According to this embodiment, during the period T2, the potential change of the wiring 191-CA[q1] transmitting the drive signal ComA[q1] is in the positive direction, while the potential change of the wiring 191-CB[q1] transmitting the drive signal ComB[q1] is in the negative direction. Therefore, the change in the magnetic field generated around the wiring 191-CA[q1] due to the potential change in the positive direction and the change in the magnetic field generated around the wiring 191-CB[q1] due to the potential change in the negative direction cancel each other out. Since these two magnetic field changes cancel each other out, the influence on the signal transmitted by the wiring 191 arranged around the wiring 191-CA[q1] and the wiring 191-CB[q1] can be suppressed.

[0093] Moreover, the absolute value of the potential difference dVH obtained by subtracting the reference potential V0 from the highest potential VHb is substantially the same as the absolute value of the potential difference dVL obtained by subtracting the reference potential V0 from the lowest potential VLb. In this embodiment, the magnitude of the change in the magnetic field generated around the wiring 191-CA[q1] is approximately the same as the magnitude of the change in the magnetic field generated around the wiring 191-CB[q1]. Therefore, according to this embodiment, compared to a mode in which the absolute value of the potential difference dVH and the absolute value of the potential difference dVL are different, it is possible to suppress the influence on the signal transmitted by the wiring 191 arranged around the wiring 191-CA[q1] and the wiring 191-CB[q1].

[0094] The inkjet printer 1 also includes a head unit HU[q1] provided with a piezoelectric element PZ[q1][m1] and a piezoelectric element [q1][m2], and an FFC 19 including a wiring 191-CA[q1] for supplying a drive signal ComA[q1] to the head unit HU[q1] and a wiring 191-CB[q1] for supplying a drive signal ComB[q1] to the head unit HU[q1]. The head unit HU[q1] includes a switch SWa[q1][m1] for switching whether or not the wiring 191-CA[q1] and the piezoelectric element PZ[q1][m1] are electrically connected, and a switch SWb[q1][m2] for switching whether or not the wiring 191-CB[q1] and the piezoelectric element PZ[q1][m2] are electrically connected. The FFC 19 includes a line 191-SI that transmits a designation signal SI that designates the operation of the switch SWa[q1][m1] and the switch SWa[q1][m2]. According to this embodiment, the influence of the micro vibration waveform on the designation signal SI can be suppressed. If noise due to the micro vibration waveform affects the designation signal SI, there is a risk of ejection defects occurring. In this embodiment, the influence of the micro vibration waveform on the designation signal SI can be suppressed, so ejection defects can be reduced. Since the designation signal SI is a digital signal, it is less affected by noise compared to an analog signal. However, when the number M of nozzles increases, the current flowing through the wiring 191 that transmits the drive signal Com increases, so the change in the magnetic field due to the potential change of the wiring 191 also increases, and the magnitude of the induced current also increases. As a result of the increased induced current, there is a risk that the signal level indicated by the potential of the original signal and the signal level indicated by the potential obtained by adding noise to the potential of the original signal may differ from each other among the two signal levels, high level and low level. In this embodiment, the noise due to the micro vibration waveform can be reduced, so the influence of the micro vibration waveform on the designation signal SI can be suppressed.

[0095] The inkjet printer 1 also includes a discharge unit D[q1][m1] and a discharge unit D[q1][m2]. The discharge unit D[q1][m1] includes a piezoelectric element PZ[q1][m1], a cavity 320 whose volume changes as the piezoelectric element PZ[q1][m1] is driven, and a nozzle N that communicates with the cavity 320 and can discharge ink filled in the cavity 320 according to the change in the volume inside the cavity 320. The discharge unit D[q1][m2] includes a piezoelectric element PZ[q1][m2], a cavity 320 whose volume changes as the piezoelectric element PZ[q1][m2] is driven, and a nozzle N that communicates with the cavity 320 and can discharge ink filled in the cavity 320 according to the change in the volume inside the cavity 320. The driving signal ComA[q1] drives the piezoelectric element PZ[q1][m1] so that ink is not ejected from the ejection section D[q1][m1] from the start of the period T2 to the end of the period T4. The driving signal ComA[q2] drives the piezoelectric element PZ[q1][m2] so that ink is not ejected from the ejection section D[q1][m2] from the start of the period T7 to the end of the period T9. According to this embodiment, it is possible to suppress an increase in the viscosity of the ink by the micro-vibration waveform, while suppressing noise generated by the micro-vibration waveform.

[0096] The designer of the inkjet printer 1 also provided a head unit HU[q1] provided with the piezoelectric element PZ[q1][m1] and the piezoelectric element PZ[q1][m2], a head unit HU[q2] provided with the piezoelectric element PZ[q2][m3] that drives in response to the supply of the drive signal ComA[q2] or the drive signal ComB[q2], and an FFC19 including a wiring 191-CA[q1] and a wiring 191-CB[q1]. The head unit HU[q2] is provided with a detection circuit 20[q2] that detects vibrations that occur in the piezoelectric element [q2][m3] when the piezoelectric element PZ[q2][m3] is driven by the drive signal ComA[q2] or the drive signal ComB[q2], and outputs the detection result as a residual vibration signal NSAS[q2][m3]. The FFC19 has a wiring 191-N[q2] that transmits the residual vibration signal NSAS[q2][m3]. According to this embodiment, the influence of the micro vibration waveform on the residual vibration signal NSAS can be suppressed. When noise affects the residual vibration signal NSAS, there is a risk of a judgment error in the ejection state occurring. Specifically, the judgment error is when the ejection state is judged to be abnormal even though it is normal, when the ejection state is judged to be normal even though it is abnormal, or when the cause of the ejection abnormality is judged to be different from the actual cause. When the ejection state is judged to be abnormal even though it is actually normal, unnecessary maintenance processing is executed. When the ejection state is judged to be normal even though it is actually abnormal, the maintenance processing is not executed, so the ejection state cannot be restored. When the cause of the ejection abnormality is judged to be different from the actual cause, the maintenance processing according to the actual cause is not executed, so the ejection state cannot be restored.

[0097] The influence of noise on the residual vibration signal NSAS due to the micro-vibration waveform will be described with reference to FIGS.

[0098] Fig. 16 is an explanatory diagram showing the influence of noise on the residual vibration signal NSAS due to the micro vibration waveform in this embodiment. In the control period Tu2, when the discharge section D[q1][m1] is driven by the drive signal ComA[q1] having the first micro vibration waveform WHb and the discharge section D[q1][m2] is driven by the drive signal ComB[q1] having the second micro vibration waveform WLb, the residual vibration signal NSAS[q2][m3] has a waveform as shown in Fig. 16. In this embodiment, the potential difference between the maximum potential and the minimum potential of the residual vibration signal NSAS[q2][m3] is a potential difference dV1. The potential difference dV1 is, for example, 130 mV.

[0099] FIG. 17 is an explanatory diagram showing the influence of noise on the residual vibration signal NSAS due to the micro-vibration waveform in the reference example. In the reference example, in the control period Tu2, the drive signal ComA[q1] has the first micro-vibration waveform WHb, and the drive signal ComBa[q1] in the reference example does not have the second micro-vibration waveform WLb, and there is no change in the potential difference. In the control period Tu2, when the discharge section D[q1][m1] is driven by the drive signal ComA[q1] having the first micro-vibration waveform WHb, the residual vibration signal NSAS[q2][m3] has a waveform exemplified in FIG. 16. The potential difference between the maximum potential and the minimum potential of the residual vibration signal NSAS[q2][m3] in the reference example is the potential difference dV2. The potential difference dV2 is, for example, 450 mV.

[0100] As can be seen from FIG. 16 and FIG. 17, the potential difference dV1 is smaller than the potential difference dV2. The reason why the potential difference dV1 is smaller than the potential difference dV2 will be described. In this embodiment, a magnetic field due to the first micro-vibration waveform WHb and a magnetic field due to the second micro-vibration waveform WLb are generated near the wiring 191-N[q2] that transmits the residual vibration signal NSAS[q2]. The directions of these two magnetic fields are inverted near the wiring 191-N[q2]. Therefore, the two inverted magnetic fields cancel out the change in the magnetic field, and the change in the magnetic field near the wiring 191-N[q2] becomes smaller. As a result of the change in the magnetic field becoming smaller, the induced current also becomes smaller, so the potential difference dV1 becomes smaller than the potential difference dV2 where the magnetic field does not cancel out. In addition, as shown in FIG. 16 and FIG. 17, since the residual vibration signal NSAS is an analog signal, it is more affected by noise than a digital signal. 8 to 10, the period from the start of period T2 having the micro-vibration waveform to the end of period T4 in head unit HU[q1] and the period from the start of period T7 to the end of period T9 overlap with the control period TSS5 in head unit HU[q2], so that noise generated by the micro-vibration waveform is included in the detection signal Vout[q2][m]. Therefore, according to this embodiment, the noise is smaller than in the reference example, so that the ejection state judgment failure can be reduced.

[0101] The inkjet printer 1 also has a wiring 191-CA[q1], a wiring 191-CB[q1], a wiring 191-V1[q1] that is electrically connected to one end of the piezoelectric element PZ[q1][m1] and maintains one end of the piezoelectric element PZ[q1][m1] at a constant potential Vbs, and a wiring 191-V2[q1] that is electrically connected to one end of the piezoelectric element PZ[q1][m2] and maintains one end of the second piezoelectric element at a constant potential Vbs. The wiring 191-CA[q1] and the wiring 191-CB[q1] are disposed between the wiring 191-V1[q1] and the wiring 191-V2[q1]. According to the first embodiment, the wiring 191-CA[q1] and the wiring 191-CB[q1] are arranged between the wiring 191-V1[q1] and the wiring 191-V2[q1], so that it is possible to suppress the influence of the micro-vibration waveform on the signal transmitted by the wiring 191 arranged other than between the wiring 191-V1[q1] and the wiring 191-V2[q1]. In the example of FIG. 7, the wiring 191 arranged other than between the wiring 191-V1[q1] and the wiring 191-V2[q1] is the wiring 191-SI and 191-N[q1].

[0102] 2. Variations The above-mentioned embodiments can be modified in various ways. Specific modified embodiments are exemplified below. Two or more embodiments selected from the following examples can be combined as long as they are not mutually contradictory.

[0103] 2.1. First modified example In the embodiment, the timing of the potential change in the first micro-vibration waveform WHb and the timing of the potential change in the second micro-vibration waveform WLb are substantially the same, but this is not limited thereto.

[0104] FIG. 18 is an explanatory diagram showing the first micro vibration waveform WHb and the second micro vibration waveform WLbb in the first modified example. The driving signal ComBb[q1] in the first modified example has the second micro vibration waveform WLbb in the control period Tu2. The control period Tu2 is divided into a period T6, a period T7 following the period T6, a period T8 following the period T7, a period T9 following the period T8, and a period T10 following the period T9. In the period T6, the driving signal ComBb[q1] is held at the reference potential V0. In the period T7, the driving signal ComBb[q1] transitions from the reference potential V0 to the minimum potential VLb. In the period T8, the driving signal ComBb[q1] is held at the minimum potential VLb. In the period T8, the driving signal ComBb[q1] transitions from the minimum potential VLb to the reference potential V0. In a period T10, the drive signal ComBb[q1] is held at the reference potential V0. 18, periods T1 and T6 partially overlap, periods T2 and T7 partially overlap, periods T3 and T8 partially overlap, periods T4 and T9 partially overlap, and periods T5 and T10 partially overlap. For example, overlapping period T27 shown in FIG 18 is a period in which periods T2 and T7 overlap, and overlapping period T49 is a period in which periods T4 and T9 overlap. It should be noted that the period T7 is an example of a "fourth period", the period T8 is an example of a "fifth period", and the period T9 is an example of a "sixth period".

[0105] In the overlapping period T27 and the overlapping period T49, as in the embodiment, the change in the magnetic field generated around the wiring 191-CA[q1] due to the potential change in the positive direction and the change in the magnetic field generated around the wiring 191-CB[q1] due to the potential change in the negative direction cancel each other out. Since the changes in the two magnetic fields cancel each other out, the influence on the signal transmitted by the wiring arranged around the wiring 191-CA[q1] and the wiring 191-CB[q1] can be suppressed. Here, as the period during which the period T2 and the period T7 overlap increases, the period during which the two magnetic fields cancel each other out becomes longer. Therefore, it is preferable that the period during which the period T2 and the period T7 overlap is long, and the most preferable embodiment is one in which the period T2 and the period T7 are approximately the same. As for the period T4 and the period T9, as in the case of the period T2 and the period T7, it is preferable that the period during which the period T4 and the period T9 overlap is long, and the most preferable embodiment is one in which the period T4 and the period T9 are approximately the same.

[0106] 2.2. Second variant In the embodiment, the absolute value of the potential difference dVH obtained by subtracting the reference potential V0 from the highest potential VHb is approximately the same as the absolute value of the potential difference dVL obtained by subtracting the reference potential V0 from the lowest potential VLb, but they may be different. However, as the absolute values ​​of the two potential differences approach each other, the magnitude of the change in the magnetic field generated around the wiring 191-CA[q1] and the magnitude of the change in the magnetic field generated around the wiring 191-CB[q1] approach each other. Therefore, it is preferable that the absolute value of the potential difference dVH is close to the absolute value of the potential difference dVL, and an embodiment in which they are approximately the same is most preferable.

[0107] 2.3.Third Modification In the embodiment, the reference potential V0 is described as being the "first potential" and the "third potential", in other words, the reference potential of the drive signal ComA[q1] is the same as the reference potential of the drive signal ComB[q1], but this is not limited thereto. For example, the reference potential of the drive signal ComA[q1] may be different from the reference potential of the drive signal ComB[q1].

[0108] 2.4. Fourth Variation In the embodiment, it has been described that the piezoelectric element PZ[q1][m1] is an example of a "first piezoelectric element" and the piezoelectric element PZ[q1][m2] is an example of a "second piezoelectric element". That is, in the embodiment, the first piezoelectric element and the second piezoelectric element are included in the same head unit HU, but the first piezoelectric element and the second piezoelectric element may be included in different head units HU. For example, the piezoelectric element PZ[q1][m1] may be an example of a "first piezoelectric element", and the piezoelectric element PZ[q3][m5] may be an example of a "second piezoelectric element". The variable q3 is an integer from 1 to Q and is different from the variable q1. The variable m5 is an integer from 1 to M. Furthermore, since the drive signal ComA[q1] supplied to the piezoelectric element PZ[q1][m1] has the first micro-vibration waveform WHb during the control period Tu2, and the drive signal ComA[q3] supplied to the piezoelectric element PZ[q3][m5] has the second micro-vibration waveform WLb during the control period Tu2, the influence on the signals transmitted by wiring arranged near the wiring 191 transmitting the drive signal ComA[q1] and the wiring 191 transmitting the drive signal ComA[q3] can be suppressed.

[0109] 2.5. Fifth Variant In the embodiment, it has been described that the influence of the micro vibration waveform on the designation signal SI and the influence of the micro vibration waveform on the residual vibration signal NSAS can be suppressed, but the signals that can be suppressed from the influence of the micro vibration waveform are not limited to the designation signal SI and the residual vibration signal NSAS. Specifically, the influence of the micro vibration waveform can also be suppressed on the clock signal CL, the latch signal LAT, the change signal CH, and the period designation signal Tsig.

[0110] 2.6. Sixth Modification In the embodiment, the number Q of head units HU is described as an even number of 2 or more, but it may be an odd number of 3 or more. For example, when the number Q is 3, the drive signal generation circuits 62[1] and 62[3] may generate the drive signal Com[q1] shown in Fig. 9, and the drive signal generation circuit 62[2] may generate the drive signal Com[q2] shown in Fig. 9.

[0111] 2.7. Seventh Variation In each of the above-described embodiments, a serial inkjet printer 1 in which the transport body 82 housing the head module HM is moved back and forth in the X-axis direction has been exemplified, but the present invention is not limited to such embodiments. The inkjet printer may be a line-type inkjet printer in which a plurality of nozzles N are distributed across the entire width of the recording paper P. In a line-type inkjet printer, the head module HM does not move, so the FFC 19 may not be included. For example, instead of the FFC 19, a line-type inkjet printer has a rigid board on which wiring 191-CA[q] for transmitting the drive signal ComA[q] and wiring 191-CA[q] for transmitting the drive signal ComB[q] are arranged.

[0112] 2.8. Eighth Variation The inkjet printers exemplified in the above-mentioned embodiments can be used in various devices such as facsimile machines and copy machines, in addition to devices dedicated to printing. However, the use of the liquid ejection device of the present invention is not limited to printing. For example, a liquid ejection device that ejects a solution of a coloring material is used as a manufacturing device for forming a color filter of a liquid crystal display device. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes of a wiring board.

[0113] 2.9. Ninth Variation In the above-mentioned embodiments, an inkjet printer 1 having two piezoelectric elements PZ has been described as an example. Furthermore, the above-mentioned embodiments can also be applied to a capacitive load driving circuit having two piezoelectric elements. Examples of capacitive load driving circuits include fingerprint sensors, echo systems, and mammography systems.

[0114] As in the inkjet printer 1, the capacitive load drive circuit drives one of the two piezoelectric elements, the first piezoelectric element, in response to the supply of a first drive signal. The other piezoelectric element is driven in response to the supply of a second drive signal. The first drive signal transitions from a first potential to a second potential in a first period, maintains the second potential in a second period following the first period, and transitions from the second potential to the first potential in a third period following the second period. The second drive signal transitions from a third potential to a fourth potential in a fourth period, maintains the fourth potential in a fifth period following the fourth period, and transitions from the fourth potential to the third potential in a sixth period following the fifth period. The first period and the fourth period overlap each other partially or entirely, the third period and the sixth period overlap each other partially or entirely, the second potential is higher than the first potential, and the fourth potential is lower than the third potential.

[0115] The capacitive load drive circuit includes a head unit provided with a first piezoelectric element and a second piezoelectric element, and a flexible flat cable including a first wiring for supplying a first drive signal to the head unit and a second wiring for supplying a second drive signal to the head unit. The head unit includes a first switch for switching whether or not the first wiring and the first piezoelectric element are electrically connected, and a second switch for switching whether or not the second wiring and the second piezoelectric element are electrically connected. The flexible flat cable includes a control wiring for transmitting a designation signal that designates the operation of the first switch and the second switch.

[0116] The flexible flat cable of the capacitive load drive circuit has a third wiring electrically connected to one end of the first piezoelectric element for holding the one end of the first piezoelectric element at a constant potential, and a fourth wiring electrically connected to one end of the second piezoelectric element for holding the one end of the second piezoelectric element at a constant potential. The first wiring and the second wiring are disposed between the third wiring and the fourth wiring. [Explanation of symbols]

[0117] 1...inkjet printer, 4...maintenance unit, 6...control module, 7...transport mechanism, 8...movement mechanism, 10...switching circuit, 11...connection state designation circuit, 14...liquid container, 19...FFC, 20...detection circuit, 60...control unit, 61...storage unit, 62...drive signal generation circuit, 64...ejection state determination circuit, 66...constant voltage generation circuit, 81...endless belt, 82...transport body, 191...wiring, 192...insulating layer, 193...shield layer, 310...diaphragm, 320...cavity, 330...nozzle plate, 340...cavity plate, 350...ribbon Reservoir, 360...ink supply port, 370...ink intake port, CH...change signal, CL...clock signal, Com...drive signal, ComA, ComB, ComBa, ComBb...drive signal, D...ejection section, ejection section to be judged, print drive ejection section, DC...decoder, HD...recording head, HM...head module, HU...head unit, Img...print data, LAT...latch signal, LHa, LHb, LHs...internal wiring, LT...latch circuit, M...number, N...nozzle, NSAS...residual vibration signal, NTc...time length, P...recording paper, PZ...piezoelectric element Child, PlsC, PlsL, PlsT1, PlsT2...pulse, SI...designation signal, SLa, SLb, SLs...connection state designation signal, SR...transfer circuit, SVbs, SVbs1, SVbs2...constant potential signal, SWa, SWb, SWs...switch, Sd...individual designation signal, Sla, Slb, Stt...connection state designation signal, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10...period, T27, T49...overlap period, TSS1, TSS2, TSS3, TSS4, TSS5, TSS6...control period, Tsig...period designation signal, Tth1, Tth2, Tth3...threshold value, Tu...unit period, Tu1, Tu2, Tu3...control period, V0...reference potential, VHb, VHd, VHk, VHs...highest potential, VLb, VLd, VLk, VLs...lowest potential, Vbs...constant potential, Vin...supply drive signal, Vout...detection signal, W0...waveform, WHb...first micro-vibration waveform, WLb, WLbb...second micro-vibration waveform, Wd...large dot waveform, Wk...judgment waveform, Ws...small dot waveform, Zd...lower electrode, Zm...piezoelectric body, Zu...upper electrode, dCom...waveform designation signal, dV1, dV2, dVH, dVL...potential difference.

Claims

1. a first piezoelectric element that is driven in response to a first drive signal; a second piezoelectric element that is driven in response to a second drive signal; a first head unit provided with the first piezoelectric element and the second piezoelectric element; a second head unit provided with a third piezoelectric element that is driven in response to a supply of a third drive signal; a flexible flat cable including a first wiring for supplying the first drive signal to the first head unit and a second wiring for supplying the second drive signal to the first head unit; Equipped with The first drive signal is In a first period, a transition from a first potential to a second potential occurs, maintaining the second potential in a second period following the first period; In a third period following the second period, a transition is made from the second potential to the first potential, The second drive signal is In a fourth period, the potential transitions from the third potential to the fourth potential, In a fifth period following the fourth period, the fourth potential is maintained; In a sixth period following the fifth period, the fourth potential transitions to the third potential, The first period and the fourth period overlap each other partially or completely, The third period and the sixth period overlap each other partially or completely, the second potential is higher than the first potential, the fourth potential is lower than the third potential, The second head unit is a detection unit that detects vibrations generated in the third piezoelectric element in response to the driving of the third piezoelectric element by the third drive signal and outputs a result of the detection as a detection signal; The flexible flat cable is A detection wiring for transmitting the detection signal is provided. A liquid ejection device comprising:

2. an absolute value of a potential difference obtained by subtracting the first potential from the second potential is substantially equal to an absolute value of a potential difference obtained by subtracting the third potential from the fourth potential; The liquid ejection device according to claim 1 .

3. the first period and the fourth period are substantially the same period, The third period and the sixth period are substantially the same period.

3. The liquid ejection device according to claim 1, wherein the liquid ejection device is a liquid ejection device.

4. The first head unit, a first switch that switches between electrically connecting the first wiring and the first piezoelectric element; a second switch that switches whether or not the second wiring and the second piezoelectric element are electrically connected, The flexible flat cable is a control line for transmitting a designation signal for designating an operation of the first switch and the second switch; 4. The liquid ejection device according to claim 1, wherein the liquid ejection device is a liquid ejection device.

5. a first ejection unit including the first piezoelectric element, a first pressure chamber whose volume changes in response to the driving of the first piezoelectric element, and a first nozzle that communicates with the first pressure chamber and is capable of ejecting liquid filled in the first pressure chamber in response to a change in the volume inside the first pressure chamber; a second ejection unit including the second piezoelectric element, a second pressure chamber whose volume changes in response to the driving of the second piezoelectric element, and a second nozzle that is in communication with the second pressure chamber and is capable of ejecting liquid filled in the second pressure chamber in response to the change in volume inside the second pressure chamber; Equipped with the first drive signal drives the first piezoelectric element so as not to eject liquid from the first ejection section from a start of the first period to an end of the third period; the second drive signal drives the second piezoelectric element so as not to eject liquid from the second ejection portion from the start of the third period to the end of the sixth period.

5. The liquid ejection device according to claim 1, wherein the liquid ejection device is a liquid ejection device.

6. The flexible flat cable a third wiring electrically connected to one end of the first piezoelectric element and configured to hold the one end of the first piezoelectric element at a constant potential; a fourth wiring electrically connected to one end of the second piezoelectric element and configured to hold the one end of the second piezoelectric element at a constant potential; The first wiring and the second wiring are disposed between the third wiring and the fourth wiring.

4. The liquid ejection device according to claim 1, wherein the liquid ejection device is a liquid ejection device.

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