Liquid dispensing device

Abstract

To provide a liquid dispensing device that can reduce the risk of degrading the image quality formed on the medium and the risk of impairing convenience. [Solution] A liquid ejection device in which, when a state determination circuit that determines the state of multiple ejection units determines that an abnormality has occurred in the first ejection unit, the first switch circuit corresponding to the first piezoelectric element that ejects liquid from the first ejection unit does not supply a drive signal to the first piezoelectric element during the ejection period in which liquid is ejected from the print head, and when a state determination circuit that determines the state of multiple ejection units determines that an abnormality has occurred in the second ejection unit, the second switch circuit corresponding to the second piezoelectric element that ejects liquid from the second ejection unit does not supply a drive signal to the second piezoelectric element during the ejection period.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device.

Background Art

[0002] There is known a liquid ejection device (liquid injection device) that ejects a liquid by driving a piezoelectric element and forms an image on a medium when the ejected liquid lands on the medium. In such a liquid ejection device, the piezoelectric element is driven by generating a potential difference between both ends of the piezoelectric element, and the liquid is ejected toward the medium by the driving of the piezoelectric element.

[0003] In a liquid ejection device having such a configuration, when an abnormality occurs in the piezoelectric element, the ejection characteristics of the liquid may deteriorate, and the image quality formed on the medium may deteriorate. In response to such a problem, Patent Document 1 discloses a liquid ejection device (liquid injection device) provided with a piezoelectric element in which the risk of an abnormality occurring in the piezoelectric element that drives the liquid to be ejected is reduced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with only the technology described in Patent Document 1, the risk of an abnormality occurring in the piezoelectric element cannot be completely suppressed. Therefore, from the viewpoint of reducing the risk of deterioration of the image quality formed on the medium when an abnormality occurs in the piezoelectric element and reducing the risk of impairing the convenience of the liquid ejection device, only the technology described in Patent Document 1 is not sufficient, and there is room for further improvement.

Means for Solving the Problems

[0006] One embodiment of the liquid dispensing device according to the present invention is: A print head having a plurality of discharge sections, including a first discharge section that discharges liquid by driving a first piezoelectric element, and a second discharge section that discharges liquid by driving a second piezoelectric element, A drive circuit that outputs a drive signal supplied to one end of the first piezoelectric element and one end of the second piezoelectric element, A reference voltage circuit that outputs a reference voltage signal supplied to the other end of the first piezoelectric element and the other end of the second piezoelectric element, A first switch circuit that switches whether or not to supply the drive signal to one end of the first piezoelectric element, A second switch circuit for switching whether or not to supply the drive signal to one end of the second piezoelectric element, A state determination circuit for determining the state of the plurality of discharge units, A sink circuit that switches the impedance value between a first wiring through which the reference voltage signal propagates and a second wiring through which a signal with a lower potential than the reference voltage signal propagates. Equipped with, If the state determination circuit determines that an abnormality has occurred in the first ejection unit, the first switch circuit will not supply the drive signal to the first piezoelectric element during the ejection period in which liquid is ejected from the print head. If the state determination circuit determines that an abnormality has occurred in the second discharge unit, the second switch circuit will not supply the drive signal to the second piezoelectric element during the discharge period. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows an example of the functional configuration of a liquid dispensing device. [Figure 2] This figure shows an example of a schematic internal structure of a liquid dispensing device. [Figure 3] This is a diagram showing the schematic structure of the discharge section. [Figure 4] This is a diagram showing an example of nozzle arrangement. [Figure 5] This figure shows an example of the configuration of a drive circuit. [Figure 6]It is a diagram showing an example of the configuration of a reference voltage circuit. [Figure 7] It is a diagram showing an example of the configuration of a sink circuit. [Figure 8] It is a diagram showing an example of the functional configuration of a head unit. [Figure 9] It is a diagram for explaining an example of various signals input to a connection state specifying circuit. [Figure 10] It is a diagram showing an example of the configuration of a waveform shaping circuit. [Figure 11] It is a diagram for explaining an example of various signals output by a control unit during a period when ejection processing is being executed. [Figure 12] It is a diagram showing an example of the relationship between an individual specification signal Sd[m] and connection state specification signals Qc[m], Qs[m] during a period when ejection processing is being executed. [Figure 13] It is a diagram for explaining an example of various signals input to a supply switching circuit of a head unit during a period when determination processing is being executed. [Figure 14] It is a diagram showing an example of the relationship between an individual specification signal Sd[m] and connection state specification signals Qc[m], Qs[m] during a period when determination processing is being executed. [Figure 15] It is a diagram showing an example of the relationship between an individual specification signal Sd[m] and connection state specification signals Qf, Q1, Q2 during a period when determination processing is being executed. [Figure 16] It is a diagram for explaining an example of the acquisition operation of a detection potential signal VX based on a signal corresponding to residual vibration generated in a discharge part D[m] to be inspected. [Figure 17] It is a diagram showing an example of pump suction processing. [Figure 18] It is a diagram showing an example of wiping processing. [Figure 19] It is a diagram for explaining the operation of a liquid ejection device.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The drawings used are for convenience of explanation. Note that the embodiments described below do not unduly limit the content of the present invention described in the claims. Also, not all of the configurations described below are essential constituent elements of the present invention.

[0009] 1. Overview of the liquid ejection device The liquid ejection device 1 of the present embodiment will be described by exemplifying an inkjet printer that ejects ink as an example of a liquid onto a medium such as recording paper and forms an image on the medium. Note that the liquid ejection device 1 is not limited to an inkjet printer, and may be a colorant ejection device used for manufacturing color filters such as liquid crystal displays, an electrode material ejection device used for forming electrodes such as organic EL displays and FEDs (surface emission displays), a biological organic matter ejection device used for manufacturing biochips, a three-dimensional modeling device, a printing device, and the like.

[0010] FIG. 1 is a diagram showing an example of the functional configuration of the liquid ejection device 1. The liquid ejection device 1 of the present embodiment forms an image corresponding to an image data signal IMG input from an external device such as a computer on a medium. As shown in FIG. 1, the liquid ejection device has a control unit 2, a head unit 3, a sink unit 4, a drive circuit unit 5, a determination unit 7, a conveyance unit 8, a carriage movement unit 9, and a maintenance unit 10.

[0011] The control unit 2 controls each component of the liquid ejection device 1 including the head unit 3, the sink unit 4, the drive circuit unit 5, the determination unit 7, the conveyance unit 8, the carriage movement unit 9, and the maintenance unit 1 0. Such a control unit 2 is configured to include one or more CPUs (Central Processing Unit) and a storage circuit. Note that the control unit 2 may be configured to include a programmable logic device such as an FPGA (Field Programmable Gate Array) instead of or in addition to the CPU.

[0012] The image data signal IMG is input to the control unit 2. In response to the input image data signal IMG, the control unit 2 generates signals to control the operation of each part of the liquid dispensing device 1, such as the transport control signal Ctrl-T, carriage control signal Ctrl-C, maintenance control signal Ctrl-M, clock signal CL, print data signal SI, latch signal LAT, change signal CH, period specification signal Tsig, and drive waveform specification signal dCOM, and outputs them to the corresponding configuration.

[0013] The drive circuit unit 5 includes a drive circuit 50. A drive waveform specification signal dCOM is input to the drive circuit 50. The drive circuit 50 generates a drive signal COM by amplifying the signal waveform defined by the input drive waveform specification signal dCOM. The drive circuit 50 also generates a reference voltage signal VBS along with the drive signal COM. The drive signal COM and reference voltage signal VBS generated by the drive circuit 50 are then output from the drive circuit unit 5.

[0014] The sink unit 4 includes a sink circuit 40. The sink circuit 40 is connected to the wiring through which the reference voltage signal VBS propagates and to the wiring with ground potential. The sink circuit 40 then discharges the charge from the wiring through which the reference voltage signal VBS propagates to the wiring through which the ground potential propagates, according to the voltage value of the reference voltage signal VBS.

[0015] The clock signal CL, print data signal SI, latch signal LAT, change signal CH, and period specification signal Tsig are input to the head unit 3. The head unit 3 also receives the drive signal COM and reference voltage signal VBS output by the drive circuit unit 5. The head unit 3 controls the supply of the drive signal COM to the multiple ejector units D included in the recording head 32 (described later) for each period defined by the latch signal LAT, change signal CH, and period specification signal Tsig, in accordance with the print data signal SI propagated in sync with the clock signal CL. This allows for individual control of the operation of the multiple ejector units D during each period defined by the latch signal LAT, change signal CH, and period specification signal Tsig, specifically controlling the ejection of ink from each of the multiple ejector units D.

[0016] Specifically, the head unit 3 includes a supply switching circuit 31, a recording head 32, and a detection circuit 33. The recording head 32 also has multiple discharge sections D. Here, in the following description, the recording head 32 will be described as having M discharge sections D. When the M discharge sections D of the recording head 32 are specified and described individually, they may be referred to as discharge sections D[1] to D[M]. In this case, when any m-th discharge section D among the M discharge sections D of the recording head 32 is specified and described, it may be referred to as discharge section D[m]. M is a natural number satisfying "M≧1", and m is any natural number satisfying "1≦m≦M". Furthermore, in the following description, when indicating that a component of the liquid discharge device 1 or a signal etc. corresponds to discharge section D[m] among the M discharge sections D, the subscript [m] may be added to the symbol representing the component or signal etc.

[0017] The clock signal CL, print data signal SI, latch signal LAT, change signal CH, period specification signal Tsig, and drive signal COM are input to the supply switching circuit 31. At each of the timings defined by the latch signal LAT, change signal CH, and period specification signal Tsig, the supply switching circuit 31 switches whether or not to supply the drive signal COM as a supply drive signal VIN to the corresponding ejection unit D based on the print data signal SI. This supply drive signal VIN is supplied to the piezoelectric element PZ, which will be described later, located in the ejection unit D, and the piezoelectric element PZ The piezoelectric element PZ is driven. Then, an amount of ink corresponding to the amount the piezoelectric element PZ is driven is ejected from the ejection unit D.

[0018] Furthermore, the supply switching circuit 31, at each of the timings defined by the latch signal LAT, the change signal CH, and the period specification signal Tsig, acquires a signal corresponding to the residual vibration generated in the ejection unit D to be inspected, based on the print data signal SI, and switches whether or not to supply it to the detection circuit 33 as a detection potential signal VX.

[0019] The detection circuit 33 generates a detection signal SK based on the detection potential signal VX supplied via the supply switching circuit 31 and outputs it from the head unit 3. Specifically, the detection circuit 33 amplifies the input detection potential signal VX, removes noise components, and then converts the signal into a digital signal to generate the detection signal SK, which is then output from the head unit 3.

[0020] The detection signal SK output from the head unit 3 is input to the determination unit 7. Based on the input detection signal SK, the determination unit 7 determines whether the ink ejection state at the ejection unit D under inspection is normal, and whether the ejection unit D under inspection is in a normal ejection state. Specifically, the determination unit 7 reads predetermined determination threshold information and correction value information from a storage circuit (not shown) including non-volatile memory such as ROM (Read Only Memory) or flash memory. The determination unit 7 corrects the input detection signal SK according to the read correction value information and compares the corrected signal with the predetermined determination threshold information. Then, based on the comparison result, the determination unit 7 determines whether an ejection abnormality has occurred at the ejection unit D under inspection, and whether the ejection unit D under inspection is in a normal ejection state. After that, the determination unit 7 generates a state determination signal JH indicating the determination result and outputs it to the control unit 2.

[0021] In the following explanation, determining whether or not an ejection abnormality has occurred in the ejection unit D under inspection, and determining whether or not the ejection unit D under inspection is in a normal ejection state, may be simply referred to as determining the state of the ejection unit D under inspection. Furthermore, an ejection abnormality is a general term for a state in which there is an abnormality in the ink ejection state from the ejection unit D under inspection, and in which ink cannot be accurately ejected from the ejection unit D under inspection. Such ejection abnormalities include, for example, a state in which ink cannot be ejected from the ejection unit D, a state in which an amount of ink different from the amount of ink ejection specified by the drive signal COM is ejected from the ejection unit D, and a state in which ink is ejected from the ejection unit D at a speed different from the ink ejection speed specified by the drive signal COM.

[0022] The transport control signal Ctrl-T is input to the transport unit 8. The transport unit 8 controls the transport of the medium to which the ink lands, according to the input transport control signal Ctrl-T. The carriage control signal Ctrl-C is input to the carriage movement unit 9. The carriage movement unit 9 controls the movement of the carriage, which will be described later, on which the head unit 3 is mounted. As a result, the control unit 2 controls the relative position between the head unit 3, which ejects the ink, and the medium to which the ink lands.

[0023] The maintenance control signal Ctrl-M is input to the maintenance unit 10. The maintenance unit 10 attempts to restore the state of the discharge unit D where the discharge abnormality occurred by executing maintenance processing corresponding to the input maintenance control signal Ctrl-M.

[0024] In the liquid ejection device 1 described above, when an ejection process is performed to form an image on a medium according to the image data signal IMG by ejecting ink, the control unit 2 generates a signal such as a print data signal SI to control the head unit 3 so that ink is ejected based on the input image data signal IMG, and outputs it to the head unit 3. The control unit 2 generates a drive waveform specification signal dCOM to control the drive circuit unit 5, which outputs a drive signal COM to drive the ejection unit D so that ink is ejected, and outputs it to the drive circuit unit 5. At the same time, the control unit 2 generates and outputs a transport control signal Ctrl-T to control the transport unit 8 and a carriage control signal Ctrl-C to control the carriage movement unit 9. As a result, the ink ejected from the ejection unit D lands at the desired position on the medium, and an image corresponding to the image data signal IMG is formed on the medium.

[0025] Furthermore, when a determination process is performed to determine the state of the ejection unit D, the control unit 2 generates a signal such as a print data signal SI to determine the state of the ejection unit D to be inspected and outputs it to the head unit 3. It also generates a drive waveform specification signal dCOM to control the drive circuit unit 5 to output a drive signal COM to determine the state of the ejection unit D and outputs it to the drive circuit unit 5. As a result, the detection circuit 33 receives a detection potential signal VX corresponding to the ejection unit D to be inspected via the supply switching circuit 31. The detection circuit 33 acquires the input detection potential signal VX, generates a detection signal SK corresponding to the acquired detection potential signal VX, and outputs it to the determination unit 7. Based on the input detection signal SK, the determination unit 7 determines whether the ink ejection state at the ejection unit D to be inspected is normal, and whether the ejection unit D to be inspected is in a normal ejection state. The determination unit 7 then generates a state determination signal JH according to the determination result of the state of the ejection unit D to be inspected and outputs it to the control unit 2. This allows the control unit 2 to acquire the state of the ejection unit D of the object being inspected and correct various signals to be output according to the acquired state of the ejection unit D of the object being inspected. As a result, the quality of the image formed on the medium is improved.

[0026] Furthermore, the control unit 2 outputs a maintenance control signal Ctrl-M to the maintenance unit 10 to perform maintenance processing. The maintenance unit 10 attempts to restore the state of the ejection unit D where the ejection abnormality occurred by performing maintenance processing in accordance with the input maintenance control signal Ctrl-M. This makes it possible to restore the state of the ejection unit D where the ejection abnormality occurred, and as a result, the quality of the image formed on the medium is improved.

[0027] As described above, the liquid dispensing device 1 of this embodiment performs various processes, including a dispensing process that forms an image on a medium corresponding to the image data signal IMG, a determination process that determines the state of the dispensing unit D that dispenses ink onto the medium, and a maintenance process that attempts to restore the state of the dispensing unit D.

[0028] Although Figure 1 illustrates a case where the liquid dispensing device 1 has one head unit 3, the liquid dispensing device 1 may have multiple head units 3. In this case, the liquid dispensing device 1 may have a control unit 2, a sink unit 4, a drive circuit unit 5, and a determination unit 7 corresponding to each of the multiple head units 3.

[0029] Next, an overview of the structure of the liquid ejection device 1 will be described. Figure 2 is a diagram showing an example of the schematic internal structure of the liquid ejection device 1. As shown in Figure 2, the liquid ejection device 1 of this embodiment is assumed to be a serial inkjet printer. That is, when the liquid ejection device 1 performs the ejection process, it transports a medium P such as recording paper along the sub-scanning direction, and while reciprocating a carriage 91 equipped with a head unit 3 along the main scanning direction intersecting the sub-scanning direction, it ejects ink from the head unit 3. At this time, the ink ejected from the head unit 3 lands at a desired position on the medium P, forming dots on the medium P corresponding to the image data signal IMG. Note that the liquid ejection device 1 is not limited to a serial inkjet printer, but may also be a line-type inkjet printer.

[0030] In the following explanation, we will use mutually orthogonal X, Y, and Z axes. In some cases, the starting point of an arrow indicating the direction along the X-axis is referred to as the -X side and the tip as the +X side; the starting point of an arrow indicating the direction along the Y-axis is referred to as the -Y side and the tip as the +Y side; and the starting point of an arrow indicating the direction along the Z-axis is referred to as the -Z side and the tip as the +Z side. In this embodiment, as illustrated in Figure 2, the liquid dispensing device 1 has a sub-scanning direction along the X-axis and a main scanning direction along the Y-axis, and the medium P is transported along the X-axis with the -X side being the upstream side and the +X side being the downstream side, and the carriage 91 is provided to reciprocate along the Y-axis.

[0031] As shown in Figure 2, the liquid ejection device 1 comprises a housing 100 and a carriage 91 that is reciprocally movable in the Y-axis direction within the housing 100 and is equipped with one or more head units 3. The carriage 91 is also equipped with four ink cartridges 120 that correspond one-to-one with four colors of ink: cyan, magenta, yellow, and black. In this embodiment, as an example, the liquid ejection device 1 is assumed to be equipped with four head units 3 that correspond one-to-one with four ink cartridges 120.

[0032] Each of the four head units 3 has M ejection ports D, which are supplied with ink from the corresponding ink cartridge 120. As a result, the inside of the 4M ejection ports D of each of the four head units 3 are filled with ink supplied from the corresponding ink cartridge 120. Each of the 4M ejection ports D of each of the four head units 3 then ejects the filled ink toward the medium P. Note that the ink cartridge 120 may not be mounted on the carriage 91, but may be provided outside the carriage 91.

[0033] Furthermore, the liquid dispensing device 1 of this embodiment includes, as the carriage movement unit 9 described above, a carriage transport mechanism 92 for reciprocating the carriage 91 along the Y axis, and a carriage guide shaft 93 for supporting the carriage 91 so that it can reciprocate in the direction along the Y axis. The transport unit 8 includes a medium transport mechanism 81 for transporting the medium P, and a platen 82 provided on the -Z side of the carriage 91. When the dispensing process is performed, the carriage transport mechanism 92 causes the carriage 91, on which the head unit 3 is mounted, to reciprocate along the Y axis along the carriage guide shaft 93, and the medium transport mechanism 81 transports the medium P on the platen 82 along the X axis from the -X side to the +X side. As a result, the relative position of the medium P with respect to the head unit 3 changes, making it possible for ink to land on the entire medium P.

[0034] Here, we will describe an example of the structure of one of the multiple ejection units D that eject ink onto the medium P. Figure 3 is a schematic diagram of the ejection unit D. As shown in Figure 3, the ejection unit D includes a piezoelectric element PZ, a cavity 322 filled with ink, a nozzle N communicating with the cavity 322, and a diaphragm 321. The ejection unit D is activated when a supply drive signal VIN is supplied to the piezoelectric element PZ, which drives the piezoelectric element PZ, causing the ink stored inside the cavity 322 to be ejected from the nozzle N.

[0035] The cavity 322 is a space partitioned by a cavity plate 324, a nozzle plate 323 on which the nozzle N is formed, and a diaphragm 321. The cavity 322 communicates with a reservoir 325 via an ink supply port 326, and the reservoir 325 communicates with an ink cartridge 120 corresponding to the ejection section D via an ink intake port 327. As a result, ink is supplied to the inside of the cavity 322 from the corresponding ink cartridge 120 via the ink intake port 327, the reservoir 325, and the ink supply port 326. Therefore, the inside of the cavity 322 is filled with ink supplied from the corresponding ink cartridge 120.

[0036] The piezoelectric element PZ has an upper electrode Zu, a lower electrode Zd, and a piezoelectric body Zm. The piezoelectric body Zm is located between the upper electrode Zu and the lower electrode Zd. The upper electrode Zu is supplied with a supply drive signal VIN output by the supply switching circuit 31. The lower electrode Zd is supplied with a reference voltage signal VBS propagating through the wiring Lb. The piezoelectric body Zm is displaced along the Z-axis to the +Z side or the -Z side according to the potential difference between the upper electrode Zu and the lower electrode Zd, which is the potential difference between the voltage value of the supply drive signal VIN supplied to the upper electrode Zu and the voltage value of the reference voltage signal VBS supplied to the lower electrode Zd. In other words, the piezoelectric element PZ is driven to be displaced along the Z-axis to the +Z side or the -Z side according to the potential difference between the voltage value of the supply drive signal VIN and the voltage value of the reference voltage signal VBS. Here, the reference voltage signal VBS supplied to the lower electrode Zd is a signal that serves as the reference potential for driving the piezoelectric element PZ, and its potential is constant, such as 5.5V, 6V, or ground potential.

[0037] The lower electrode Zd is joined to the diaphragm 321. Therefore, when the piezoelectric element PZ is driven to displace along the Z-axis by the supply drive signal VIN, the diaphragm 321 also displaces along the Z-axis. This displacement of the diaphragm 321 changes the internal volume and internal pressure of the cavity 322. Then, in accordance with the changes in the internal volume and internal pressure of the cavity 322, the ink filled inside the cavity 322 is ejected from the nozzle N. That is, an amount of ink corresponding to the amount of drive of the piezoelectric element PZ is ejected from the nozzle N of the ejection unit D. In other words, the piezoelectric element PZ ejects an amount of ink from the ejection unit D corresponding to the displacement caused by the supply drive signal VIN corresponding to the drive signal COM. That is, the ejection unit D includes a piezoelectric element PZ driven by the drive signal COM, and ejects ink by driving the piezoelectric element PZ. In other words, the liquid ejection device 1 has an ejection unit D that ejects ink, which is an example of a liquid.

[0038] Figure 4 shows an example of the arrangement of a total of 4M discharge units D and 4M nozzles N, which are provided on four head units 3. As shown in Figure 4, the four head units 3 are positioned side by side along the Y-axis on the carriage 91. At this time, the M discharge units D and nozzles N of each of the four head units 3 are arranged side by side along the X-axis. Specifically, the M discharge units D[1] to D[M] of the head unit 3 are positioned adjacent to each other along the X-axis from the -X side to the +X side in the order of discharge unit D[1], discharge unit D[2], discharge unit D[3], ..., discharge unit D[M]. That is, the head unit 3 includes a nozzle row NL formed by the arrangement of M nozzles N, which are provided on each of the M discharge units D, side by side along the X-axis from the -X side to the +X side. Therefore, the carriage 91 has four rows of nozzles NL, each containing one of the four head units 3, formed along the Y-axis. Ink is ejected from each of the nozzles N that form the nozzle rows NL contained in each of the four head units 3. Hereinafter, in the following description, the surface on which multiple nozzle rows NL are formed by the multiple head units 3 mounted on the carriage 91, which is located facing the medium P and from which ink is ejected toward the medium P, may be referred to as the ejection surface 115.

[0039] In other words, the liquid ejection device 1 of this embodiment includes a recording head 32 having a plurality of ejection units D, including an ejection unit D[1] that ejects ink by driving a piezoelectric element PZ[1] and an ejection unit D[m] that ejects ink by driving a piezoelectric element PZ[m], and a head unit 3.

[0040] 2. Configuration and Operation of the Drive Circuit Next, the configuration and operation of the drive circuit 50 in the drive circuit unit 5 will be described. As described above, the drive circuit 50 generates and outputs the drive signal COM by amplifying the signal waveform defined by the drive waveform specification signal dCOM.

[0041] Figure 5 shows an example of the configuration of the drive circuit 50. As shown in Figure 5, the drive circuit 50 has an integrated circuit 500, an amplification circuit 550, a demodulation circuit 560, feedback circuits 570, 572, and several other circuit elements. The integrated circuit 500 generates gate signals Hgd and Lgd based on the drive waveform specification signal dCOM and outputs them to the amplification circuit 550. The amplification circuit 550 has transistors M1 and M2, and when transistors M1 and M2 are driven based on the gate signals Hgd and Lgd, it generates amplified modulation signals AMs and outputs them to the demodulation circuit 560. The demodulation circuit 560 demodulates the amplified modulation signals AMs by smoothing them. The signal demodulated by this demodulation circuit 560 is output as a drive signal COM from the drive circuit 50 and the drive circuit unit 5.

[0042] The integrated circuit 500 has multiple terminals, including terminals In, Bst, Hdr, Sw, Gvd, Ldr, Gnd, Ifb, Vfb, and Vbs. The integrated circuit 500 is electrically connected to an external circuit through these multiple terminals. The integrated circuit 500 also includes a DAC (Digital to Analog Converter) 511, a modulation circuit 510, and a gate drive circuit 520.

[0043] The DAC511 converts the drive waveform specification signal dCOM, which is a digital signal that defines the signal waveform of the drive signal COM, into an analog signal, the base drive waveform signal aO, and outputs it to the modulation circuit 510. The amplified signal of the base drive waveform signal aO output by the DAC511 corresponds to the drive signal COM. In other words, the base drive waveform signal aO is the target analog signal before amplification of the drive signal COM, and the drive waveform specification signal dCOM is the target digital signal before amplification of the drive signal COM, and is a digital signal that defines the shape of the signal waveform of the drive signal COM. The voltage amplitude of the base drive waveform signal aO output by the DAC511 is set to, for example, 1V to 2V.

[0044] The modulation circuit 510 generates a modulated signal Ms by modulating the base drive waveform signal aO and outputs it to the gate drive circuit 520. The modulation circuit 510 includes adders 512, 513, a comparator 514, an inverter 515, an integral attenuator 516, and an attenuator 517.

[0045] The integrating attenuator 516 attenuates and integrates the voltage value of the drive signal COM input via terminal Vfb, and outputs the integrated signal to the negative input terminal of adder 512. The base drive waveform signal aO is input to the positive input terminal of adder 512. Adder 512 generates a signal with a voltage value obtained by subtracting the voltage value of the signal input to the negative input terminal from the voltage value of the signal input to the positive input terminal and integrating it, and outputs this signal to the positive input terminal of adder 513. Here, as mentioned above, the maximum voltage amplitude of the base drive waveform signal aO is about 2V, while the voltage value of the drive signal COM can exceed 40V at its maximum value. In order to determine the deviation, the integrating attenuator 516 attenuates the drive signal COM input via terminal Vfb in order to match the range of the voltage amplitude of the base drive waveform signal aO with the range of the voltage value amplitude of the drive signal COM.

[0046] The attenuator 517 supplies a voltage obtained by attenuating the high-frequency component of the drive signal COM input via terminal Ifb to the negative input terminal of the adder 513. The signal output by adder 512 is input to the positive input terminal of adder 513. Adder 513 generates a voltage signal As by subtracting the voltage value of the signal input to the negative input terminal from the voltage value of the signal input to the positive input terminal, and outputs it to comparator 514. The voltage signal As is obtained by subtracting the voltage value of the signal supplied to terminal Vfb from the voltage value of the base drive waveform signal aO, and then further subtracting the voltage value of the signal supplied to terminal Ifb. Therefore, the voltage signal As is a signal in which the deviation obtained by subtracting the attenuated voltage of the drive signal COM from the voltage value of the target base drive waveform signal aO is corrected by the high-frequency component of the drive signal COM.

[0047] Comparator 514 pulse-modulates the voltage signal As and outputs it as the modulated signal Ms. Specifically, the comparator 514 outputs a modulated signal Ms that becomes H level when the voltage value of the voltage signal As rises to or above a predetermined threshold Vth1, and L level when the voltage value of the voltage signal As falls below a predetermined threshold Vth2, during the period when the voltage value of the voltage signal As is falling. Here, the thresholds Vth1 and Vth2 are set such that threshold Vth1 > threshold Vth2. The frequency and duty cycle of this modulated signal Ms change in accordance with the drive waveform specification signal dCOM and the base drive waveform signal aO. That is, the amount of change in the frequency and duty cycle of the modulated signal Ms can be adjusted by adjusting the modulation gain, which corresponds to the sensitivity of the attenuator 517.

[0048] The modulated signal Ms is input to the gate driver 521 included in the gate drive circuit 520. Furthermore, the modulated signal Ms is inverted at a logic level by the inverter 515 and then input to the gate driver 522 also included in the gate drive circuit 520. In other words, signals with mutually exclusive logic levels are input to gate driver 521 and gate driver 522.

[0049] Here, the timing of the signals input to gate drivers 521 and 522 may be controlled so that their logic levels are not simultaneously at a high level. In other words, the "mutually exclusive relationship of logic levels" mentioned above means that the logic level of the signal input to gate driver 521 and the logic level of the signal input to gate driver 522 are not simultaneously at a high level, and this includes the case where the logic level of the signal input to gate driver 521 and the logic level of the signal input to gate driver 522 are simultaneously at a low level.

[0050] The gate drive circuit 520 includes gate driver 521 and gate driver 522.

[0051] The gate driver 521 generates a gate signal Hgd by level-shifting the modulated signal Ms output by the comparator 514, and outputs it from the integrated circuit 500 via terminal Hdr. Of the power supply voltage of the gate driver 521, the high-potential side is supplied via terminal Bst, and the low-potential side is supplied via terminal Sw. Terminal Bst is electrically connected to one end of capacitor C5 and the cathode of diode D1. The other end of capacitor C5 is electrically connected to terminal Sw. The anode of diode D1 is electrically connected to terminal Gvd. In addition, a voltage signal VM, which is a DC voltage of, for example, 7.5V generated by a power supply circuit (not shown), is supplied to terminal Gvd. As a result, the potential difference between terminal Bst and terminal Sw is the potential difference across capacitor C5, which is approximately equal to the voltage value of the voltage signal VM. Therefore, the gate driver 521 generates a gate signal Hgd, which, according to the logic level of the input modulation signal Ms, has a high-level voltage value that is greater than the voltage value of terminal Sw by the voltage value of voltage signal VM, and a low-level voltage value that is the voltage value of terminal Sw, and outputs this signal from terminal Hdr.

[0052] The gate driver 522 operates at a lower potential than the gate driver 521. The gate driver 522 generates a gate signal Lgd by level-shifting the signal obtained by inverting the logic level of the modulated signal Ms output by the comparator 514 with the inverter 515, and outputs it from the integrated circuit 500 via terminal Ldr. Of the power supply voltage of the gate driver 522, the voltage signal VM is supplied to the high potential side, and the ground potential is supplied to the low potential side via terminal Gnd. The gate driver 522 then generates a gate signal Lgd at ground potential, where the H level voltage value is greater than the voltage value of the voltage signal VM relative to terminal Gnd, and the L level voltage value is the voltage value of terminal Gnd, and outputs it from terminal Ldr.

[0053] As described above, the gate signal Hgd is a signal obtained by level-shifting the voltage value of the modulated signal Ms, and the gate signal Lgd is a signal obtained by level-shifting the voltage value of the inverted signal after inverting the logic level of the modulated signal Ms. In light of this, the gate signals Hgd and Lgd output by the gate drive circuit 520 can also be considered to be signals obtained by modulating the drive waveform specification signal dCOM and the base drive waveform signal aO.

[0054] The amplification circuit 550 includes a pair of transistors M1 and M2, which are semiconductor elements such as N-type FETs (Field Effect Transistors).

[0055] A voltage signal VHV, for example, a DC voltage of 42V, is supplied to the drain terminal of transistor M1. The voltage value of the voltage signal VHV is not limited to 42V and only needs to be greater than the maximum voltage value of the drive signal COM output by the drive circuit 50 and the drive circuit unit 5. The gate terminal of transistor M1 is electrically connected to one end of resistor R1. The other end of resistor R1 is electrically connected to terminal Hdr of integrated circuit 500. That is, the gate signal Hgd output by integrated circuit 500 is input to the gate terminal of transistor M1. The source terminal of transistor M1 is electrically connected to terminal Sw of integrated circuit 500. The conduction state between the drain terminal and the source terminal of transistor M1 is controlled by the gate signal Hgd input to the gate terminal.

[0056] The drain terminal of transistor M2 is electrically connected to terminal Sw of integrated circuit 500. That is, the drain terminal of transistor M2 and the source terminal of transistor M1 are electrically connected to each other. The gate terminal of transistor M2 is electrically connected to one end of resistor R2. The other end of resistor R2 is electrically connected to terminal Ldr of integrated circuit 500. That is, the gate signal Lgd output by integrated circuit 500 is input to the gate terminal of transistor M2. Ground potential is supplied to the source terminal of transistor M2. The conduction state between the drain terminal and the source terminal of transistor M2 is controlled by the gate signal Lgd input to the gate terminal.

[0057] In the following explanation, the state in which the drain and source terminals of transistors M1 and M2 are controlled to conduct is referred to as "on," and the state in which the drain and source terminals of transistors M1 and M2 are controlled to not conduct is referred to as "off."

[0058] In the amplifier circuit 550 configured as described above, when transistor M1 is controlled to be off and transistor M2 is controlled to be on, the node to which terminal Sw is connected becomes ground potential. At this time, the voltage signal VM is supplied to terminal Bst. On the other hand, when transistor M1 is controlled to be on and transistor M2 is controlled to be off, the node to which terminal Sw is connected becomes the voltage signal VHV. Therefore, the terminal Bst is supplied with a voltage signal that is the sum of the voltage value of the voltage signal VHV and the voltage value of the voltage signal VM. In other words, the gate driver 521 that drives transistor M1 uses capacitor C5 as a floating power supply, and the potential of terminal Sw at the other end of capacitor C5 changes to ground potential or the voltage value of voltage signal VHV in accordance with the operation of transistors M1 and M2. As a result, the gate driver 521 generates a gate signal Hgd where the L level is the voltage value of voltage signal VHV and the H level is the sum of the voltage value of voltage signal VHV and the voltage value of voltage signal VM, and supplies this to the gate terminal of transistor M1.

[0059] On the other hand, the gate driver 522 that drives transistor M2 generates a gate signal Lgd where the L level is ground potential and the H level is the voltage value of the voltage signal VM, regardless of the operation of transistors M1 and M2, and supplies it to the gate terminal of transistor M2.

[0060] As described above, the amplifier circuit 550 operates transistors M1 and M2 in accordance with the gate signals Hgd and Lgd, thereby amplifying the modulated signal Ms, which is a modulated version of the drive waveform specification signal dCOM and the base drive waveform signal aO, based on the voltage signal VHV. The amplifier circuit 550 then outputs the amplified signal as the amplified modulated signal AMs from the connection point where the source terminal of transistor M1 and the drain terminal of transistor M2 are commonly connected.

[0061] The demodulation circuit 560 demodulates the amplified modulation signal AMs by smoothing them and generates a drive signal COM. The demodulation circuit 560 then outputs the generated drive signal COM from the drive circuit 50.

[0062] The demodulation circuit 560 includes a coil L1 and a capacitor C1. One end of coil L1 is electrically connected to the source terminal of transistor M1 and the drain terminal of transistor M2. As a result, the amplified modulation signal AMs is input to one end of coil L1. The other end of coil L1 is also connected to one end of capacitor C1. The other end of capacitor C1 is supplied with ground potential. In other words, coil L1 and capacitor C1 constitute a low-pass filter. The amplified modulation signal AMs is smoothed by the low-pass filter configured in the demodulation circuit 560, and a drive signal COM is generated at the connection point where the other end of coil L1 and one end of capacitor C1 are electrically connected.

[0063] The feedback circuit 570 includes resistors R3 and R4. A drive signal COM is supplied to one end of resistor R3, and the other end of resistor R3 is connected to terminal Vfb and one end of resistor R4. A voltage signal VHV is supplied to the other end of resistor R4. As a result, the drive signal COM, which has passed through the feedback circuit 570, is fed back to terminal Vfb in a pulled-up state.

[0064] The feedback circuit 572 includes capacitors C2, C3, and C4, and resistors R5 and R6. One end of capacitor C2 is supplied with the drive signal COM, and the other end of capacitor C2 is connected to one end of resistor R5 and one end of resistor R6. The other end of resistor R5 is supplied with ground potential. As a result, capacitor C2 and resistor R5 function as a high-pass filter.

[0065] Furthermore, the other end of resistor R6 is connected to one end of capacitor C4 and one end of capacitor C3. The other end of capacitor C3 is supplied with ground potential. As a result, resistor R6 and capacitor C3 function as a low-pass filter.

[0066] As described above, the feedback circuit 572 is configured with a high-pass filter and a low-pass filter. As a result, the feedback circuit 572 functions as a band-pass filter that allows a predetermined frequency range of the drive signal COM to pass through. The other end of capacitor C4 included in the feedback circuit 572 is connected to terminal Ifb of the integrated circuit 500. As a result, the signal that is fed back to terminal Ifb is the drive signal COM that has passed through the feedback circuit 572, which functions as a band-pass filter that allows predetermined frequency components to pass through, with the DC component of the high-frequency components removed.

[0067] As described above, the drive signal COM output by the drive circuit 50 is a demodulated signal obtained by the demodulation circuit 560 smoothing the amplified modulation signal AMs based on the drive waveform specification signal dCOM. The drive signal COM output by the demodulation circuit 560 is then integrated and attenuated via the feedback circuit 570 and terminal Vfb before being fed back to the adder 512. As a result, the drive circuit 50 self-oscillates at a frequency determined by the feedback delay and the feedback transfer function. However, the delay is large if only the feedback path via terminal Vfb is used, and therefore, the feedback via terminal Vfb However, in some cases, the self-oscillation frequency cannot be increased to a level that sufficiently ensures the accuracy of the drive signal COM.

[0068] In this embodiment, the drive circuit 50 has a separate path for feeding back the high-frequency components of the drive signal COM via the feedback circuit 572 and terminal Ifb, in addition to the path via terminal Vfb. As a result, in the drive circuit 50 of this embodiment, the overall delay of the circuit can be reduced, and the frequency of the voltage signal As can be increased to a level that sufficiently ensures the accuracy of the drive signal COM, compared to the case where there is no path via terminal Ifb. Consequently, the waveform accuracy of the drive signal COM is improved.

[0069] In other words, the drive circuit 50 includes a Class D amplifier circuit and outputs a drive signal COM that is supplied to the upper electrode Zu[1] which is one end of the piezoelectric element PZ[1] and the upper electrode Zu[m] which is one end of the piezoelectric element PZ[m].

[0070] Furthermore, as shown in Figure 5, the integrated circuit 500 of the drive circuit 50 has a reference voltage circuit 530. The reference voltage circuit 530 generates a reference voltage signal VBS by stepping down the voltage value of the voltage signal VM, and outputs it from the drive circuit 50 and the drive circuit unit 5 via the terminal Vbs of the integrated circuit 500.

[0071] Figure 6 shows an example of the configuration of the reference voltage circuit 530. The reference voltage circuit 530 includes a comparator 531, a transistor 532, and resistors 534 and 535. Note that transistor 532 is assumed to be a PMOS transistor for this explanation.

[0072] A reference voltage Vref is supplied to the negative input terminal of comparator 531. The reference voltage Vref can be generated, for example, based on the bandgap reference voltage of integrated circuit 500. The positive input terminal of comparator 531 is electrically connected to one end of resistor 534 and one end of resistor 535. The output terminal of comparator 531 is electrically connected to the gate terminal of transistor 532. A voltage signal VM is supplied to the source terminal of transistor 532. The drain terminal of transistor 532 is electrically connected to the other end of resistor 534. Ground potential is supplied to the other end of resistor 535. The reference voltage circuit 530 outputs a reference voltage signal VBS from the connection point where the drain terminal of transistor 532 and the other end of resistor 534 are electrically connected.

[0073] In the reference voltage circuit 530 configured as described above, if the voltage value supplied to the + input terminal of comparator 531 is greater than the voltage value of the reference voltage Vref supplied to the - input terminal of comparator 531, comparator 531 outputs a high-level signal. At this time, transistor 532 is controlled to be off. Therefore, no voltage signal VM is supplied to the connection point where the drain terminal of transistor 532 and the other end of resistor 534 are electrically connected. On the other hand, if the voltage value supplied to the - input terminal of comparator 531 is less than the voltage value of the reference voltage Vref supplied to the - input terminal of comparator 531, comparator 531 outputs a low-level signal. At this time, transistor 532 is controlled to be on. Therefore, a voltage signal VM is supplied to the connection point where the drain terminal of transistor 532 and the other end of resistor 534 are electrically connected.

[0074] In other words, in the reference voltage circuit 530, the comparator 531 and transistor 532 operate so that the voltage value obtained by dividing the voltage value of the reference voltage signal VBS, which is the voltage value at the connection point where the drain terminal of transistor 532 and the other end of resistor 534 are electrically connected, by resistors 534 and 535, is equal to the voltage value of the reference voltage Vref. In this way, the reference voltage circuit 530 generates and outputs a reference voltage signal VBS with a constant voltage value. In other words, the reference voltage circuit 530 generates and outputs a reference voltage signal VBS with a constant voltage value by stepping down the voltage value of the voltage signal VM. The VBS signal is generated and output from the drive circuit 50 and the drive circuit unit 5 via the Vbs terminal of the integrated circuit 500.

[0075] In other words, the drive circuit unit 5 has a reference voltage circuit 530 that outputs a reference voltage signal VBS supplied to the lower electrode Zd[1], which is the other end of the piezoelectric element PZ[1], and to the lower electrode Zd[m], which is the other end of the piezoelectric element PZ[m].

[0076] The reference voltage circuit 530 may be configured separately from the drive circuit unit 5, and in this case, some or all of the circuit elements that make up the reference voltage circuit 530 may be composed of discrete components outside the integrated circuit 500. However, as shown in Figure 5, it is preferable that all of the circuit elements that make up the reference voltage circuit 530 are configured inside the integrated circuit 500. This makes it possible to miniaturize the drive circuit unit 5, which includes the drive circuit 50 and the reference voltage circuit 530, and the liquid dispensing device 1 having the drive circuit unit 5.

[0077] 3. Configuration and Operation of the Sink Circuit Next, the configuration and operation of the sink circuit 40 of the sink unit 4 will be described. Figure 7 shows an example of the configuration of the sink circuit 40. As described above, the sink circuit 40 releases the charge from the wiring Lb through which the reference voltage signal VBS propagates to the wiring Lg through which the ground potential propagates, in accordance with the voltage value of the reference voltage signal VBS.

[0078] If a short circuit occurs in one of the piezoelectric elements PZ[1] to PZ[M], which are located in each of the discharge sections D[1] to D[M], for example, in piezoelectric element PZ[m], the amount of current flowing into the wiring Lb through the short-circuited piezoelectric element PZ[m] increases. As the amount of current propagating through the wiring Lb increases, the voltage value of the signal propagating through the wiring Lb, which is the voltage value of the reference voltage signal VBS, rises. Subsequently, when this voltage value exceeds a predetermined detection threshold that activates the overvoltage protection function (not shown) of the liquid discharge device 1, the liquid discharge device 1 stops operating.

[0079] On the other hand, the liquid ejection device 1 has a so-called complementary function in which, if ink is not ejected from ejection section D[m], the dots that would normally be formed on the medium P by the ink ejected from ejection section D[m] are filled in with dots formed by the ink ejected from at least one of ejection sections D[m+1] and D[m-1], which are located adjacent to ejection section D[m]. In a liquid ejection device 1 having such a complementary function, if the liquid ejection device 1 immediately stops operating due to a short-circuit abnormality occurring in a small number of piezoelectric elements PZ among the piezoelectric elements PZ[1] to PZ[M], the liquid ejection device 1 will stop operating even though it is possible to form an image on the medium P corresponding to the image data signal IMG, and as a result, the productivity of the liquid ejection device 1 may decrease.

[0080] The sink circuit 40 has a sink function that, in response to the aforementioned problem, releases the charge from the wiring Lb to the wiring Lg through which ground potential propagates when the voltage value of the signal propagating through the wiring Lb exceeds a predetermined voltage value, thereby reducing the risk of the voltage value of the reference voltage signal VBS rising, and reducing the risk of the liquid dispensing device 1 stopping due to a short-circuit abnormality occurring in a small number of piezoelectric elements PZ[1] to PZ[M] among the piezoelectric elements PZ[1] to PZ[M]. As a result, even if a short-circuit abnormality occurs in a small number of piezoelectric elements PZ[m] among the piezoelectric elements PZ[1] to PZ[M] in each of the dispensing sections D[1] to D[M], the risk of a decrease in productivity in the liquid dispensing device 1 can be reduced.

[0081] An example of the configuration and operation of such a sink circuit 40 will be described. Figure 7 shows the sink This figure shows an example of the configuration of circuit 40. As shown in Figure 7, the sink circuit 40 has a resistor 401, a constant voltage diode 402, a transistor 403, and a resistor 410.

[0082] Transistor 403 is a PNP bipolar transistor. The emitter terminal of transistor 403 is electrically connected to the wiring Lb through which the reference voltage signal VBS propagates. The collector terminal of transistor 403 is electrically connected to one end of resistor 410. The base terminal of transistor 403 is electrically connected to one end of resistor 401 and the cathode terminal of voltage regulator diode 402. The other end of resistor 401 is electrically connected to the wiring Lb through which the reference voltage signal VBS propagates, and the anode terminal of voltage regulator diode 402 and the other end of resistor 410 are electrically connected to the ground potential wiring Lg. In other words, one end of the sink circuit 40 is electrically connected to the wiring Lb through which the reference voltage signal VBS propagates, and the other end is electrically connected to the ground potential wiring Lg.

[0083] In the sink circuit 40 configured as described above, if the voltage value of the reference voltage signal VBS propagating through the wiring Lb is smaller than the breakdown voltage vz of the constant voltage diode 402, the voltage value at the cathode terminal of the constant voltage diode 402 is maintained at the voltage value of the reference voltage signal VBS. Therefore, the voltage value at the emitter terminal and the base terminal of the transistor 403 are approximately equal. Consequently, if the voltage value of the reference voltage signal VBS propagating through the wiring Lb is smaller than the breakdown voltage vz of the constant voltage diode 402, the connection between the emitter terminal and the collector terminal of the transistor 403 is controlled to be non-conductive. In this case, the charge on the wiring Lb through which the reference voltage signal VBS propagates is not released to the wiring Lg through which the ground potential propagates. In other words, if the voltage value of the reference voltage signal VBS propagating through the wiring Lb is smaller than the breakdown voltage vz of the constant voltage diode 402, the sink circuit 40 does not release the charge on the wiring Lb.

[0084] On the other hand, if the voltage value of the reference voltage signal VBS propagating through the wiring Lb is greater than the breakdown voltage vz of the constant voltage diode 402, the voltage value at the cathode terminal of the constant voltage diode 402 is held at the breakdown voltage vz. Therefore, a potential difference is generated between the emitter terminal and the base terminal of the transistor 403, corresponding to the difference between the voltage value of the reference voltage signal VBS and the breakdown voltage vz of the constant voltage diode 402. If this potential difference is greater than the threshold voltage of the transistor 403, the connection between the emitter terminal and the collector terminal of the transistor 403 is controlled to conduct. As a result, the charge in the wiring Lb propagating the reference voltage signal VBS is discharged towards the wiring Lg, which is at ground potential, via the transistor 403 and the resistor 410. That is, at least a portion of the current propagating through the wiring Lb flows towards the wiring Lg via the transistor 403 and the resistor 410. At this time, the amount of charge released from wiring Lb to wiring Lg, which is the amount of current flowing from wiring Lb to wiring Lg, is controlled by the resistance value of resistor 410. In other words, the sinking capacity of sink circuit 40 is controlled by the resistance value of resistor 410.

[0085] As described above, the sink circuit 40 of this embodiment includes a transistor 403 and a resistor 410. One end of the transistor 403, the emitter terminal, is electrically connected to the wiring Lb, the other end of the transistor 403, the collector terminal, is electrically connected to one end of the resistor 410, and the other end of the resistor 410 is electrically connected to the wiring Lg. The sink circuit 40 switches the impedance value between the wiring Lb, through which the reference voltage signal VBS propagates, and the wiring Lg, through which a ground potential signal, which is a signal at a lower potential than the voltage value of the reference voltage signal VBS, propagates, by controlling the conduction state of the transistor 403.

[0086] As a result, the sink circuit 40 releases the charge from the wiring Lb through which the reference voltage signal VBS propagates to the wiring Lg through which the ground potential propagates, in accordance with the voltage value of the reference voltage signal VBS.

[0087] Such a sink circuit 40 is preferably composed of discrete components. This makes it possible to optimally select the component sizes of transistor 403 and resistor 410 according to the amount of current discharged from wiring Lb by the sink circuit 40 and the sink capacity of the sink circuit 40, thereby increasing the versatility of the sink circuit 40 and reducing the amount of heat generated in transistor 403 and resistor 410.

[0088] Furthermore, the sink circuit 40 may have a resistive element connected between the anode terminal of the constant voltage diode 402 and the wiring Lg. This makes it possible to control the voltage value held at the cathode terminal of the constant voltage diode 402 and the amount of current flowing through the constant voltage diode 402, and to precisely control the voltage value of the wiring Lb when the transistor 403 is controlled to conduct.

[0089] Furthermore, the sink circuit 40 can achieve a similar effect if it is located between the wiring Lb through which the reference voltage signal VBS propagates and the wiring through which a signal with a lower potential than the voltage value of the reference voltage signal VBS propagates. However, as shown in this embodiment, it is preferable that the sink circuit 40 is located between the wiring Lb through which the reference voltage signal VBS propagates and the wiring Lg at ground potential. This allows the sink circuit 40 to efficiently discharge charge from the wiring Lb.

[0090] 4. Head Unit Configuration Next, the functional configuration of the head unit 3 will be described. Figure 8 is a diagram showing an example of the functional configuration of the head unit 3. As described above, the head unit 3 has a supply switching circuit 31, a recording head 32, and a detection circuit 33. Figure 8 also illustrates the wiring Lc through which the drive signal COM propagates, the wiring Lb through which the reference voltage signal VBS propagates, and the wiring Ls through which the detection potential signal VX propagates to the detection circuit 33 in the head unit 3.

[0091] The supply switching circuit 31 includes switches Wc[1] to Wc[M], switches Ws[1] to Ws[M], switch Wf, resistor Rf, and a connection state specification circuit 310. Switches Wc[1] to Wc[M] and switches Ws[1] to Ws[M] are provided in the supply switching circuit 31 corresponding to the discharge sections D[1] to D[M]. Specifically, in the supply switching circuit 31, switches Wc[m] and Ws[m] are provided corresponding to the discharge section D[m].

[0092] The connection state specification circuit 310 receives a clock signal CL, a print data signal SI, a latch signal LAT, a change signal CH, and a period specification signal Tsig. The connection state specification circuit 310 generates signals that specify the conduction state of switches Wc[1]~Wc[M], switches Ws[1]~Ws[M], and switch Wf, respectively, in accordance with the print data signal SI which propagates in synchronization with the clock signal CL, for a period defined by the input latch signal LAT, change signal CH, and period specification signal Tsig. Subsequently, the connection state designation circuit 310 outputs connection state designation signals Qc[1] to Qc[M] by level-shifting the signals that specify the conduction state of switches Wc[1] to Wc[M] into high-amplitude logic signals, outputs connection state designation signals Qs[1] to Qs[M] by level-shifting the signals that specify the conduction state of switches Ws[1] to Ws[M] into high-amplitude logic signals, and outputs connection state designation signals Qf by level-shifting the signal that specifies the conduction state of switch Wf into a high-amplitude logic signal.

[0093] The connection status designation signals Qc[1]~Qc[M] output by the connection status designation circuit 310 are input to the control terminals of switches Wc[1]~Wc[M], the connection status designation signals Qs[1]~Qs[M] output by the connection status designation circuit 310 are input to the control terminals of switches Ws[1]~Ws[M], and the connection status designation signal Qf output by the connection status designation circuit 310 is input to the control terminal of switch Wf. This controls the conduction state of switches Wc[1]~Wc[M], Ws[1]~Ws[M], and Wf, respectively.

[0094] Such a connection state specification circuit 310 includes, for example, a register that holds print data signals SI propagated in synchronization with a clock signal CL corresponding to the ejection units D[1] to D[M], a decoder that decodes the print data signals SI held in the register to generate signals that specify the conduction state of switches Wc[1] to Wc[M], Ws[1] to Ws[M], and Wf, and a level shift circuit that outputs connection state specification signals Qc[1] to Qc[M], Qs[1] to Qs[M], Qf, etc., obtained by level shifting the logic of the signals generated by the decoder into high-amplitude logic signals.

[0095] Switch Wc[m], one of the switches Wc[1] to Wc[M], has one end electrically connected to the wiring Lc and the other end electrically connected to the upper electrode Zu[m] of the piezoelectric element PZ[m] included in the discharge section D[m]. The connection state designation signal Qc[m], one of the connection state designation signals Qc[1] to Qc[M], is input to the control terminal of switch Wc[m]. Switch Wc[m] switches the conduction state between one end and the other according to the logic level of the connection state designation signal Qc[m] input to the control terminal. As a result, switch Wc[m] switches whether or not to supply the drive signal COM propagating through the wiring Lc as the supply drive signal VIN[m] to the upper electrode Zu[m] of the discharge section D[m], according to the connection state designation signal Qc[m].

[0096] In other words, switch Wc[1] switches whether or not to supply a drive signal COM to the upper electrode Zu[1] which is one end of the piezoelectric element PZ[1], and switch Wc[m] switches whether or not to supply a drive signal COM to the upper electrode Zu[m] which is one end of the piezoelectric element PZ[m].

[0097] Switch Ws[m], one of the switches Ws[1] to Ws[M], has one end electrically connected to the wiring Ls and the other end electrically connected to the upper electrode Zu[m] of the piezoelectric element PZ[m] included in the discharge section D[m]. The connection state designation signal Qs[m], one of the connection state designation signals Qs[1] to Qs[M], is input to the control terminal of switch Ws[m]. Switch Ws[m] switches the conduction state between one end and the other according to the logic level of the connection state designation signal Qs[m] input to the control terminal. As a result, switch Ws[m] switches whether or not to supply the signal generated at the upper electrode Zu[m] of the piezoelectric element PZ[m] in response to residual vibrations generated in the discharge section D[m] to the wiring Ls, according to the connection state designation signal Qs[m].

[0098] In other words, switch Ws[1] switches whether or not to supply a signal to the wiring Ls corresponding to the residual vibration generated at the upper electrode Zu[1], which is one end of the piezoelectric element PZ[1], and switch Ws[m] switches whether or not to supply a signal to the wiring Ls corresponding to the residual vibration generated at the upper electrode Zu[m], which is one end of the piezoelectric element PZ[m].

[0099] Switch Wf has one end electrically connected to wiring Lc and the other end electrically connected to one end of resistor Rf. The other end of resistor Rf is electrically connected to wiring Ls. In other words, switch Wf has one end electrically connected to wiring Lc and the other end electrically connected to wiring Ls via resistor Rf. A connection state specification signal Qf is input to the control terminal of switch Wf. The conduction state between one end and the other end of switch Wf is switched according to the logic level of the connection state specification signal Qf input to the control terminal.

[0100] Each of the switches Wc[1]~Wc[M], Ws[1]~Ws[M], and Wf described above can be configured, for example, as a transmission gate.

[0101] Here, an example of various signals input to the connection state specification circuit 310 will be described. Figure 9 is a diagram illustrating an example of various signals input to the connection state specification circuit 310. As shown in Figure 9, the liquid dispensing device 1 of this embodiment operates for one or more unit periods. The TP is defined, and the operation of the discharge unit D[m] and the operation of the detection circuit 33 are controlled for each defined unit period TP.

[0102] Specifically, the control unit 2 generates a latch signal LAT including a pulse PLL and outputs it to the connection state specification circuit 310. For example, the control unit 2 may generate a latch signal LAT including a pulse PLL by setting the logic level of the latch signal LAT to a high level for a short time at a timing based on at least one of the transport position of the medium P transported along the sub-scanning direction and the scanning position of the carriage 91 that reciprocates along the main scanning direction, and output it to the connection state specification circuit 310. Alternatively, for example, the control unit 2 may generate a latch signal LAT including a pulse PLL by setting the logic level of the latch signal LAT to a high level for a short time at predetermined time intervals, and output it to the connection state specification circuit 310. The period from the rising edge of the pulse PLL included in this latch signal LAT until the next rising edge of the pulse PLL corresponds to the unit period TP described above.

[0103] Furthermore, the control unit 2 generates a change signal CH that includes a pulse PLC and outputs it to the connection state specification circuit 310. For example, the control unit 2 generates a change signal CH that includes a pulse PLC by setting the logic level of the change signal CH to a high level for a short time after a predetermined time has elapsed from the rising edge of the pulse PLL, and outputs it to the connection state specification circuit 310. The pulse PLC included in this change signal CH divides the unit period TP into a control period TQ1 and a control period TQ2. Specifically, the change signal CH divides the unit period TP into a control period TQ1, which is the period from the rising edge of the pulse PLL to the rising edge of the pulse PLC, and a control period TQ2, which is the period from the rising edge of the pulse PLC to the rising edge of the pulse PLL. Note that the number of divisions of the unit period TP by the change signal CH is not limited to two.

[0104] Furthermore, the control unit 2 generates a period specification signal Tsig, which includes pulses PLT1 and PLT2, and outputs it to the connection state specification circuit 310. For example, the control unit 2 generates pulse PLT1 by setting the logic level of the period specification signal Tsig to H level after a predetermined time has elapsed from the rising edge of the pulse PLL, and then setting the logic level of the period specification signal Tsig to L level, and outputs it to the connection state specification circuit 310. After generating pulse PLT1, the control unit 2 generates pulse PLT2 by setting the logic level of the period specification signal Tsig to H level after a predetermined time has elapsed, and then setting the logic level of the period specification signal Tsig to L level, and outputs it to the connection state specification circuit 310. The pulses PLT1 and PLT2 included in this period specification signal Tsig divide the unit period TP into control periods TT1 to TT5. Specifically, the period specification signal Tsig divides the unit period TP into control periods TT1 (from the rising edge of the pulse PLL to the rising edge of pulse PLT1), TT2 (from the rising edge of pulse PLT1 to the falling edge of pulse PLT1), TT3 (from the falling edge of pulse PLT1 to the rising edge of pulse PLT2), TT4 (from the rising edge of pulse PLT2 to the falling edge of pulse PLT2), and TT5 (from the falling edge of pulse PLT2 to the rising edge of the pulse PLL). Note that the number of divisions of the unit period TP by the period specification signal Tsig is not limited to five.

[0105] Furthermore, the control unit 2 generates a print data signal SI that serially includes the individual designation signals Sd[1] to Sd[M] and outputs it to the connection status designation circuit 310. Each of the individual designation signals Sd[1] to Sd[M] is a signal containing 2 bits of information and defines the driving mode of each of the ejection units D[1] to D[M]. Hereinafter, the 2 bits of information contained in the individual designation signal Sd[m] will be referred to as bits S1 and S2, and the individual designation signal Sd[m] = [S1, S2] will be used.

[0106] Specifically, the control unit 2 generates a print data signal SI that includes individual designation signals Sd[1] to Sd[M] that define the driving mode of the ejection units D[1] to D[M] and the operation of the detection circuit 33 during the unit period TP to be controlled, prior to the unit period TP to be controlled, and outputs it to the connection state designation circuit 310. The print data signal SI is held in a register (not shown) in the connection state designation circuit 310, with the individual designation signals Sd[1] to Sd[M] corresponding to each of the ejection units D[1] to D[M]. Then, when it becomes the unit period TP to be controlled, the connection state designation circuit 310 simultaneously latches the 2 bits of information contained in each of the individual designation signals Sd[1] to Sd[M] that it holds, and decodes the latched 2 bits of information to generate connection state designation signals Qc[1] to Qc[M], Qs[m] to Qs[M], Qf, Q1, and Q2 at a logic level corresponding to the decoded content for each of the control periods TQ1 and TQ2, or each of the control periods TT1 to TT5, within the unit period TP to be controlled, and outputs them to the respective control terminals of the switches Wc[1] to Wc[M], Ws[1] to Ws[M], Wf, W1, and W2.

[0107] This controls the conduction state of switches Wc[1]~Wc[M], Ws[1]~Ws[M], Wf, W1, and W2 during each of the control periods TQ1 and TQ2, or each of the control periods TT1 to TT5. As a result, the driving mode of the discharge units D[1]~D[M] and the operation of the detection circuit 33 are controlled during each of the control periods TQ1 and TQ2, or each of the control periods TT1 to TT5.

[0108] Returning to Figure 8, the detection circuit 33 receives the detection potential signal VX propagating through the wiring Ls and the connection status specification signals Q1 and Q2 output by the connection status specification circuit 310. The detection circuit 33 also includes a waveform shaping circuit 330 and an AD conversion circuit 331. The waveform shaping circuit 330 acquires the detection potential signal VX according to the connection status specification signals Q1 and Q2. The waveform shaping circuit 330 then removes noise from the acquired detection potential signal VX and amplifies it to shape the signal waveform of the detection potential signal VX, outputting it as the detection signal aSK. The AD conversion circuit 331 converts the analog signal of the detection signal aSK output by the waveform shaping circuit 330 into a digital signal and outputs it as the detection signal SK. This detection signal SK is output from the detection circuit 33 and the head unit 3. In other words, the detection circuit 33 converts the signal corresponding to the residual vibration generated in the ejection section D into a digital signal and outputs it as the detection signal SK.

[0109] Here, an example of the configuration of the waveform shaping circuit 330 included in the detection circuit 33 will be described. Figure 10 is a diagram showing an example of the configuration of the waveform shaping circuit 330. As shown in Figure 10, the waveform shaping circuit 330 includes a capacitor C1, operational amplifiers OP1 and OP2, switches W1 and W2, and resistors R1 to R3.

[0110] A detection potential signal VX output by the supply switching circuit 31 is input to one end of capacitor C1. The other end of capacitor C1 is electrically connected to one end of resistor R1 and one end of switch W1. Analog ground AG, fixed at a constant potential, is supplied to the other end of resistor R1 and the other end of switch W1. In other words, resistor R1 and switch W1 are connected in parallel. A connection state specification signal Q1 is input to the control terminal of switch W1. When a high-level connection state specification signal Q1 is input to the control terminal of switch W1, the connection between one end and the other becomes conductive, and when a low-level connection state specification signal Q1 is input to the control terminal, the connection between one end and the other becomes non-conductive. In other words, switch W1 switches the conduction state between one end of resistor R1 and analog ground AG. The capacitor C1, resistor R1, and switch W1 configured as described above function as a high-pass filter, extracting and outputting a predetermined high-frequency component signal from the detected potential signal VX input during the period when switch W1 is controlled to be non-conductive. Here, switch W1 may be configured as, for example, a transmission gate. Also, the analog ground AG may be, for example, the center potential between the high-potential power supply potential and the low-potential power supply potential supplied to the head unit 3.

[0111] The positive input terminal of operational amplifier OP1 is electrically connected to the connection point where the other end of capacitor C1, one end of resistor R1, and one end of switch W1 are electrically connected. In other words, the signal output by the high-pass filter composed of capacitor C1, resistor R1, and switch W1 is input to the positive input terminal of operational amplifier OP1. The negative input terminal of operational amplifier OP1 is electrically connected to the connection point where one end of resistor R2 and one end of resistor R3 are electrically connected. The output terminal of operational amplifier OP1 is electrically connected to the other end of resistor R2. In addition, analog ground AG is supplied to the other end of resistor R3. In other words, operational amplifier OP1 and resistors R2 and R3 function as a non-inverting amplifier circuit that amplifies the signal input to the positive input terminal of operational amplifier OP1 according to the resistance values ​​of resistors R2 and R3 and outputs it from the output terminal of operational amplifier OP1. Here, the non-inverting amplifier circuit, which includes the operational amplifier OP1 and resistors R2 and R3, may be configured to output an amplified signal after superimposing a predetermined offset voltage onto the signal output by a high-pass filter consisting of capacitor C1, resistor R1, and switch W1.

[0112] The positive input terminal of op-amp OP2 is electrically connected to the output terminal of op-amp OP1. In other words, the signal output by the non-inverting amplifier circuit, which consists of op-amp OP1 and resistors R2 and R3, is input to the positive input terminal of op-amp OP2. The negative input terminal of op-amp OP2 is electrically connected to the output terminal of op-amp OP2. In other words, op-amp OP2 constitutes a voltage follower circuit. As a result, op-amp OP2 converts the impedance of the signal output by the non-inverting amplifier circuit, which consists of op-amp OP1 and resistors R2 and R3, and outputs it.

[0113] One end of switch W2 is electrically connected to the output terminal of operational amplifier OP2. The signal from the other end of switch W2 is output from the waveform shaping circuit 330 as a detection signal aSK. A connection status specification signal Q2 is input to the control end of switch W2. When a high-level connection status specification signal Q2 is input to the control end of switch W2, the two ends become conductive. When a low-level connection status specification signal Q2 is input to the control end of switch W2, the two ends become non-conductive. Switch W2 switches whether or not to output the signal output by operational amplifier OP2 as a detection signal aSK from the waveform shaping circuit 330, depending on the logic level of the connection status specification signal Q2 input to the control end of switch W2.

[0114] As described above, the waveform shaping circuit 330 removes noise components from the detected potential signal VX using a high-pass filter consisting of a capacitor C1, a resistor R1, and a switch W1. The signal from which the noise components have been removed is then amplified by a non-inverting amplifier circuit consisting of an operational amplifier OP1 and resistors R2 and R3. The waveform shaping circuit 330 then performs impedance conversion using a voltage follower circuit consisting of an operational amplifier OP2, and outputs the signal as the detected signal aSK. At this time, switches W1 and W2 switch whether or not the waveform shaping circuit 330 acquires the detected potential signal VX and outputs it as the detected signal aSK.

[0115] The detection signal aSK output by the waveform shaping circuit 330 is then input to the AD conversion circuit 331. The AD conversion circuit 331 converts the detection signal aSK into a digital signal. The signal converted to digital by the AD conversion circuit 331 is then output as the detection signal SK from the detection circuit 33 and the head unit 3.

[0116] In the head unit 3 of this embodiment, configured as described above, the supply switching circuit 31 controls the conduction state of the switch Wc[m] in accordance with the print data signal SI propagated based on the clock signal CL during each of the control periods TQ1, TQ2, or TT1 to TT5, which are defined by the latch signal LAT, the change signal CH, and the period designation signal Tsig. This switches whether or not to supply the drive signal COM, which propagates through the wiring Lc, as the supply drive signal VIN[m] to the piezoelectric element PZ[m] of the discharge unit D[m]. This controls the mode of operation of the discharge unit D[m].

[0117] Furthermore, in this embodiment, the head unit 3 has a supply switching circuit 31 that controls the conduction state of switch Ws[m] in accordance with the print data signal SI propagated based on the clock signal CL during each of the control periods TQ1, TQ2 or control periods TT1 to TT5 defined by the latch signal LAT, the change signal CH, and the period specification signal Tsig. This switches whether or not to acquire a signal corresponding to the residual vibration generated in the ejection section D[m] and output it to the detection circuit 33 as a detected potential signal VX. At this time, the detection circuit 33 amplifies and shapes the signal waveform of the input detected potential signal VX according to the conduction state of switches W1 and W2 and outputs it as a detected signal SK. In other words, the detection circuit 33 acquires the electromotive force generated in the piezoelectric element PZ as a detected potential signal VX when the piezoelectric element PZ is displaced in accordance with the residual vibration generated in the ejection section D, amplifies and shapes the signal waveform of the acquired detected potential signal VX and outputs it as a detected signal SK.

[0118] The detection signal SK output by the detection circuit 33 is then input to the determination unit 7. Based on the input detection signal SK, the determination unit 7 determines the state of the target discharge section D[m].

[0119] As described above, the liquid dispensing device 1 of this embodiment includes a detection circuit 33 that detects signals corresponding to the state of multiple dispensing sections D, and a determination unit 7 that determines the state of multiple dispensing sections D based on the detection signal SK output by the detection circuit 33. The determination unit 7 determines the state of dispensing section D[1] according to the residual vibration generated in dispensing section D[1], and determines the state of dispensing section D[m] according to the residual vibration generated in dispensing section D[m].

[0120] 5. Operation of the liquid dispensing device The operation of the liquid dispensing device 1 configured as described above will now be explained. As previously stated, the liquid dispensing device 1 of this embodiment performs a dispensing process in which ink is dispensed onto the medium P to form an image corresponding to the image data signal IMG, a determination process in which the state of the dispensing unit D that dispenses ink onto the medium P is determined, and a maintenance process in which an attempt is made to restore the dispensing state of the dispensing unit D in which a dispensing abnormality occurred during the determination process. The operation of each of the dispensing process, determination process, and maintenance process performed by the liquid dispensing device 1 will be explained below.

[0121] 5.1 Discharge process Figure 11 is a diagram illustrating an example of various signals output by the control unit 2 during the period in which the dispensing process is being performed.

[0122] The control unit 2 generates a drive waveform specification signal dCOM that defines the signal waveform of the drive signal COM output by the drive circuit unit 5 during the period in which the ejection process is being performed, and outputs it to the drive circuit unit 5. The drive circuit 50 of the drive circuit unit 5 generates a drive signal COM with a continuous signal waveform, consisting of a drive waveform PP1 placed in the control period TQ1 and a drive waveform PP2 placed in the control period TQ2, as shown in Figure 11, in response to the input drive waveform specification signal dCOM, and supplies it to the head unit 3.

[0123] The drive waveform PP1 is a signal waveform in which the voltage value starts at a reference potential V0, changes to a potential VL1 which is lower than the reference potential V0, then becomes a potential VH1 which is higher than the reference potential V0, and then ends at the reference potential V0. When this drive waveform PP1 is supplied to the piezoelectric element PZ[m], the piezoelectric element PZ[m] is driven so that a predetermined amount of ink is ejected from the nozzle N[m]. In other words, the drive waveform PP1 is used to eject ink from the nozzle N[m]. This is a signal waveform.

[0124] The drive waveform PP2 is a signal waveform in which the voltage value starts at a reference potential V0, changes to a potential VH2 which is higher than the reference potential V0 and lower than the potential VH1, and then ends at the reference potential V0. When this drive waveform PP2 is supplied to the piezoelectric element PZ[m], the ink near the opening vibrates to the extent that ink is not ejected from the nozzle N[m]. This reduces the risk of an increase in the viscosity of the ink stored in the ejection section D[m] including the nozzle N[m]. Hereinafter, in the following explanation, the operation of supplying the drive waveform PP2 to the piezoelectric element PZ[m] and vibrating the ink near the opening of the nozzle N[m] is referred to as micro-vibration. In other words, the drive waveform PP2 is a signal waveform for performing micro-vibration.

[0125] Furthermore, the liquid dispensing device 1 of this embodiment controls whether to dispense ink from the dispensing device D[m], whether to dispense a drive waveform PP1, whether to dispense a drive waveform PP2, or whether to not dispense either a drive waveform PP1 or a drive waveform PP2 to the dispensing device D[m] for each unit period TP during the period in which the dispensing process is being performed. In doing so, for each unit period TP during the period in which the dispensing process is being performed, the device controls whether to dispense ink from the dispensing device D[m], whether to dispense ink from the dispensing device D[m] and perform micro-vibrations, or whether to dispense ink from the dispensing device D[m] and not perform micro-vibrations.

[0126] Specifically, during the period in which the liquid dispensing device 1 of this embodiment is performing dispensing processing, the connection state specification circuit 310 defines the conduction state of switch Wc[m] in each of the control periods TQ1 and TQ2 according to the individual specification signal Sd[m] included in the input print data signal SI. This controls whether, for each unit period TP during the period in which the liquid dispensing device 1 is performing dispensing processing, the drive waveform PP1 located in the control period TQ1 is supplied to the dispensing unit D[m] as a supply drive signal VIN[m], the drive waveform PP2 located in the control period TQ2 is supplied to the dispensing unit D[m] as a supply drive signal VIN[m], or neither the drive waveform PP1 located in the control period TQ1 nor the drive waveform PP2 located in the control period TQ2 is supplied to the dispensing unit D[m] as a supply drive signal VIN[m]. In other words, for each unit period TP, it is controlled whether ink is ejected from the ejection unit D[m], whether micro-vibrations are performed without ejecting ink from the ejection unit D[m], or whether neither ink is ejected from the ejection unit D[m] nor micro-vibrations are performed.

[0127] Here, we will explain an example of the relationship between the individual designation signals Sd[1]~Sd[M] included in the print data signal SI input to the connection status designation circuit 310 during the period when the liquid discharge device 1 is performing the discharge process, and the connection status designation signals Qc[1]~Qc[M], Qs[1]~Qs[M] output by the connection status designation circuit 310, specifically the decoding content of the individual designation signals Sd[1]~Sd[M] performed by the connection status designation circuit 310.

[0128] Figure 12 shows an example of the relationship between the individual designation signal Sd[m] and the connection status designation signals Qc[m] and Qs[m] during the period in which the discharge process is being performed.

[0129] As shown in Figure 12, when the individual specification signal Sd[m]=[1,0] is input to the connection state specification circuit 310, the connection state specification circuit 310 generates a connection state specification signal Qc[m] which is at an H level during control period TQ1 and at an L level during control period TQ2, and outputs it to the control terminal of the switch Wc[m]. As a result, the switch Wc[m] is controlled to conduct during control period TQ1 and to non-conduct during control period TQ2. Therefore, the piezoelectric element PZ[m] is supplied with a supply drive signal VIN[m] including the drive waveform PP1 during control period TQ1, and is not supplied with a supply drive signal VIN[m] including the drive waveform PP2 during control period TQ2. Here, during control period TQ2, when the piezoelectric element PZ[m] is not supplied with a supply drive signal VIN[m] including the drive waveform PP2, the upper electrode Zu[m] is directly The voltage value of the signal previously supplied to the upper electrode Zu[m], with the reference potential V0, is maintained by the capacitive component of the piezoelectric element PZ[m]. That is, during the control period TQ2, when the supply drive signal VIN[m], which includes the drive waveform PP2, is not supplied to the piezoelectric element PZ[m], a constant signal with reference potential V0 is supplied to the upper electrode Zu[m]. As a result, ink is ejected from the nozzle N[m] during the control period TQ1, and not ejected during the control period TQ2. Then, the ink ejected during the control period TQ1 lands on the medium P, forming a dot on the medium P during the unit period TP.

[0130] Furthermore, when the individual designation signal Sd[m]=[0,1] is input to the connection state designation circuit 310, the connection state designation circuit 310 generates a connection state designation signal Qc[m] that is L level during control period TQ1 and H level during control period TQ2, and outputs it to the control terminal of switch Wc[m]. As a result, switch Wc[m] is controlled to be non-conductive during control period TQ1 and conductive during control period TQ2. Therefore, the piezoelectric element PZ[m] is not supplied with a supply drive signal VIN[m] including the drive waveform PP1 during control period TQ1, but is supplied with a supply drive signal VIN[m] including the drive waveform PP2 during control period TQ2. Here, during the control period TQ1 in which the supply drive signal VIN[m] including the drive waveform PP1 is not supplied to the piezoelectric element PZ[m], the upper electrode Zu[m] maintains a reference potential V0, which is the voltage value of the signal that was supplied to the upper electrode Zu[m] immediately before, due to the capacitive component of the piezoelectric element PZ[m]. That is, during the control period TQ1 in which the supply drive signal VIN[m] including the drive waveform PP1 is not supplied to the piezoelectric element PZ[m], a constant signal with a reference potential V0 is supplied to the upper electrode Zu[m]. As a result, no ink is ejected from the nozzle N[m] during the control periods TQ1 and TQ2, and micro-vibrations are performed during the control period TQ2. Therefore, no dots are formed on the medium P during the unit period TP.

[0131] Furthermore, when the individual designation signal Sd[m]=[0,0] is input to the connection state designation circuit 310, the connection state designation circuit 310 generates a connection state designation signal Qc[m] that is L level during control period TQ1 and L level during control period TQ2, and outputs it to the control terminal of switch Wc[m]. As a result, switch Wc[m] is controlled to be non-conductive during control period TQ1 and non-conductive during control period TQ2. Therefore, the piezoelectric element PZ[m] is not supplied with the supply drive signal VIN[m] including the drive waveform PP1 during control period TQ1, and is not supplied with the supply drive signal VIN[m] including the drive waveform PP2 during control period TQ2. In other words, when the individual designation signal Sd[m]=[0,0] is input to the connection state designation circuit 310, switch Wc[m] remains non-conductive during the unit period TP. Here, during control period TQ1, when the supply drive signal VIN[m] including the drive waveform PP1 is not supplied to the piezoelectric element PZ[m], the upper electrode Zu[m] has a reference potential V0, which is the voltage value of the signal that was supplied to the upper electrode Zu[m] immediately before, held by the capacitive component of the piezoelectric element PZ[m]. During control period TQ2, when the supply drive signal VIN[m] including the drive waveform PP2 is not supplied, the upper electrode Zu[m] has a reference potential V0, which is the voltage value of the signal that was supplied to the upper electrode Zu[m] immediately before, held by the capacitive component of the piezoelectric element PZ[m]. In other words, during unit period TP, a constant signal with a reference potential V0 is supplied to the upper electrode Zu[m]. As a result, ink is not ejected from the nozzle N[m] during control periods TQ1 and TQ2, and no micro-vibrations are performed. Therefore, no dots are formed on the medium P during unit period TP.

[0132] As described above, when the liquid dispensing device 1 performs dispensing, the connection state specification circuit 310 outputs logic-level connection state specification signals Qs[1] to Qs[M] based on individual specification signals Sd[1] to Sd[M] during each of the control periods TQ1 and TQ2 within the unit period TP. This controls the conduction state of switches Wc[1] to Wc[m] during each of the control periods TQ1 and TQ2 within the unit period TP, and ink is dispensed from each of the dispensing units D[1] to D[M] during each of the control periods TQ1 and TQ2 within the unit period TP. Whether or not this occurs is controlled. This allows the liquid dispensing device 1 to form an image on the medium P corresponding to the image data signal IMG during the period in which the dispensing process is being performed.

[0133] Here, as shown in Figure 11, during the period when the liquid dispensing device 1 is performing the dispensing process, the connection state designation circuit 310 continues to output a connection state designation signal Qs[m] at an L level, regardless of the input individual designation signal Sd[m]. Therefore, during the period when the dispensing process is being performed, the switch Ws[m] is controlled to be non-conductive. As a result, during the period when the liquid dispensing device 1 is performing the dispensing process, the upper electrode Zu[m] and the wiring Ls are not electrically connected, and therefore, the signal corresponding to the residual vibration generated in the dispensing section D[m] is not supplied to the detection circuit 33. Therefore, the detection circuit 33 does not acquire the detection potential signal VX during the period when the liquid dispensing device 1 is performing the dispensing process. For this reason, although not shown in the figure, during the period when the liquid dispensing device 1 is performing the dispensing process, the connection state designation circuit 310 continues to output connection state designation signals Qf, Q1, and Q2 at an L level.

[0134] 5.2 Judgment Processing Next, we will explain the determination process for determining the state of the ejection unit D that ejects ink onto the medium P. It is known that residual vibration occurs in an ejection unit that ejects liquid such as ink by being driven by a driving element such as a piezoelectric element after the driving element has been driven. This residual vibration that occurs in the ejection unit is a so-called damped vibration in which the amplitude decreases over time, and the waveform information such as the amplitude, the rate of amplitude damping, the period, and the frequency of the damped vibration changes depending on the state of the ejection unit. For example, if the viscosity of the liquid stored in the ejection unit changes, the amplitude and the rate of amplitude damping of the residual vibration that occurs in the ejection unit will change, and if air bubbles are mixed inside the ejection unit, for example, the frequency of the residual vibration that occurs in the ejection unit will increase.

[0135] In the liquid dispensing device 1 of this embodiment, in the determination process for determining the state of the dispensing unit D that dispenses ink onto the medium P, the supply switching circuit 31 of the head unit 3 acquires a signal corresponding to the residual vibration generated in the dispensing unit D[m] to be inspected and outputs it to the detection circuit 33 as a detected potential signal VX. The detection circuit 33 generates a detected signal SK by shaping the signal waveform of the input detected potential signal VX. Then, the determination unit 7 calculates waveform information such as the amplitude, period, and frequency of the residual vibration generated in the dispensing unit D[m] to be inspected, which is the waveform information of the detected potential signal VX based on the input detected signal SK, and determines the state of the dispensing unit D[m] to be inspected based on the calculated waveform information. After that, the determination unit 7 generates a state determination signal JH indicating the determination result and outputs it to the control unit 2. As a result, the control unit 2 acquires the state of the dispensing unit D[m] to be inspected, corrects various signals to be output according to the acquired state of the dispensing unit D[m] to be inspected, or informs the user of the state of the dispensing unit D[m] to be inspected.

[0136] Figure 13 is a diagram illustrating an example of various signals input to the supply switching circuit 31 of the head unit 3 during the period in which the determination process is being executed.

[0137] The control unit 2 generates a drive waveform specification signal dCOM, which defines the signal waveform of the drive signal COM output by the drive circuit unit 5 during the period in which the determination process is being executed, and outputs it to the drive circuit unit 5. The drive circuit 50 of the drive circuit unit 5 generates a drive signal COM, including the drive waveform PS, for each unit period TP as shown in Figure 13, in response to the input drive waveform specification signal dCOM, and supplies it to the head unit 3.

[0138] The drive waveform PS is a signal waveform in which the voltage value starts at the reference potential V0 during the control period TT1, changes to a potential VS1 which is lower than the reference potential V0, then becomes a potential VS2 which is higher than the reference potential V0, maintains the potential VS2 during the control periods TT2, TT3, and TT4, and ends at the reference potential V0 during the control period TT5. This drive waveform PS is a piezoelectric element When supplied to the child PZ[m], the piezoelectric element PZ[m] is driven to prevent ink from being ejected from the nozzle N[m]. After the piezoelectric element PZ[m] is driven, a predetermined residual vibration occurs in the ejection unit D[m] at the timing when the voltage value of the drive signal COM becomes potential VS2. In other words, the drive waveform PS is a signal waveform that drives the piezoelectric element PZ[m] to prevent ink from being ejected from the nozzle N[m] and generates a predetermined residual vibration in the ejection unit D[m]. Therefore, when the drive waveform PS is supplied to the piezoelectric element PZ[m], the ejection unit D[m] operates in such a way that it does not eject ink and generates residual vibration.

[0139] The liquid dispensing device 1 controls the conduction state of switches Wc[1]~Wc[M], Ws[1]~Ws[M], Wf, W1, and W2 during each control period TT1~TT5 for each unit period TP in the period during which the judgment process is executed. This controls the supply drive signal VIN[m] including the drive waveform PS to the dispensing section D[m] to be inspected, and acquires a signal corresponding to the residual vibration generated in the dispensing section D[m] as a result of the supply drive signal VIN[m] including the drive waveform PS being supplied, and outputs this signal to the detection circuit 33 as a detected potential signal VX. The detection circuit 33 then generates a detected signal SK by shaping the signal waveform of the input detected potential signal VX, and the judgment unit 7 determines the state of the dispensing section D[m] to be inspected based on the detected signal SK.

[0140] Here, we will explain an example of the relationship between the individual designation signals Sd[1]~Sd[M] included in the print data signal SI input to the connection status designation circuit 310 during the period when the liquid discharge device 1 performs a determination process, and the connection status designation signals Qc[1]~Qc[M], Qs[1]~Qs[M], Qf, Q1, Q2 output by the connection status designation circuit 310, specifically the decoding content of the individual designation signals Sd[1]~Sd[M] performed by the connection status designation circuit 310 during the period when the determination process is being executed.

[0141] Figure 14 shows an example of the relationship between the individual designation signal Sd[m] and the connection status designation signals Qc[m] and Qs[m] during the period in which the judgment process is being executed. Here, in the liquid dispensing device 1 of this embodiment, the control unit 2 outputs the individual designation signal Sd[m]=[0,0] to the connection status designation circuit 310 when the dispensing unit D[m] is not the object of inspection during the period in which the judgment process is being executed, and outputs the individual designation signal Sd[m]=[1,1] to the connection status designation circuit 310 when the dispensing unit D[m] is the object of inspection.

[0142] As described above, when the individual designation signal Sd[m]=[0,0] is input to the connection state designation circuit 310, the connection state designation circuit 310 will keep switch Wc[m] non-conductive during the unit period TP. Therefore, as shown in Figure 14, when the individual designation signal Sd[m]=[0,0] is input to the connection state designation circuit 310, the connection state designation circuit 310 generates a connection state designation signal Qc[m] that is at an L level during the control period TT1 to TT5 and outputs it to the control terminal of switch Wc[m], and generates a connection state designation signal Qs[m] that is at an L level during the control period TT1 to TT5 and outputs it to the control terminal of switch Ws[m]. As a result, switch Wc[m] is controlled to be non-conductive and switch Ws[m] is controlled to be non-conductive during the control period TT1 to TT5. At this time, the piezoelectric element PZ[m] of the discharge section D[m], which is not the subject of inspection, is not supplied with the supply drive signal VIN[m] corresponding to the drive signal COM. Therefore, no residual vibration occurs in the discharge section D[m] that is not being inspected. Even if the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] included in the discharge section D[m] that is not being inspected changes, the signal associated with this change in potential is not supplied to the wiring Ls. In other words, the state of the discharge section D[m] that is not being inspected is not determined.

[0143] Furthermore, when the individual designation signal Sd[m]=[1,1] is input to the connection state designation circuit 310, the connection state designation circuit 310 generates a connection state designation signal Qc[m] that is at an H level during control periods TT1, TT2, and TT5, and at an L level during control periods TT3 and TT4. A connection status specification signal Qs[m] is generated and output to the control terminal of switch Wc[m], which is at a high level during control periods TT2~TT4 and at a low level during control periods TT1 and TT5, and is output to the control terminal of switch Ws[m]. As a result, switch Wc[m] is controlled to conduct during control periods TT1, TT2, and TT5 and to non-conductive during control periods TT3 and TT4, and switch Ws[m] is controlled to conduct during control periods TT2~TT4 and to non-conductive during control periods TT1 and TT5.

[0144] Figure 15 shows an example of the relationship between the individual designation signal Sd[m] and the connection status designation signals Qf, Q1, and Q2 during the period in which the determination process is being executed. Here, during the period in which the determination process is being executed, if at least one of the individual designation signals Sd[1] to Sd[M] included in the input print data signal SI is [1,1], the connection status designation circuit 310 generates a connection status designation signal Qf that is at an H level during control periods TT2 to TT4 and at an L level during control periods TT1 and TT5, and outputs it to the control terminal of switch Wf. It also generates a connection status designation signal Q1 that is at an H level during control periods TT1, TT2, TT4, and TT5 and at an L level during control period TT3, and outputs it to the control terminal of switch W1. Finally, it generates a connection status designation signal Q2 that is at an H level during control period TT3 and at an L level during control periods TT1, TT2, TT4, and TT5, and outputs it to the control terminal of switch W2. As a result, switch Wf is controlled to conduct during control periods TT2 to TT4 and to not conduct during control periods TT1 and TT5; switch W1 is controlled to conduct during control periods TT1, TT2, TT4, and TT5 and to not conduct during control period TT3; and switch W2 is controlled to conduct during control period TT3 and to not conduct during control periods TT1, TT2, TT4, and TT5.

[0145] Here, we will describe an example of the operation of the liquid dispensing device 1 when an individual designation signal Sd[m]=[1,1] corresponding to the dispensing section D[m] to be inspected is input to the connection state designation circuit 310, in which the detection circuit 33 acquires a detection potential signal VX based on a signal corresponding to the residual vibration generated in the dispensing section D[m] to be inspected.

[0146] Figure 16 is a diagram illustrating an example of the operation for acquiring a detection potential signal VX based on a signal corresponding to residual vibration generated in the discharge section D [m] of the object to be inspected. As shown in Figure 16, for each unit period TP during the period in which the determination process is being executed, the connection state designation circuit 310 is supplied with a drive signal COM including a drive waveform PS, the voltage value of which starts at a reference potential V0 in the control period TT1, changes to a potential VS1 which is lower than the reference potential V0, becomes a potential VS2 which is higher than the reference potential V0, maintains the potential VS2 in the control periods TT2 to TT4, and ends at the reference potential V0 in the control period TT5.

[0147] During the period in which the judgment process is being executed, the control unit 2 outputs an individual designation signal Sd[m]=[1,1] corresponding to the discharge section D[m] to be inspected to the connection state designation circuit 310. At this time, discharge sections D[1]~D[m-1] and D[m+1]~D[M] are excluded from inspection. That is, the control unit 2 outputs individual designation signals Sd[1]~Sd[m-1] and Sd[m+1]~Sd[M]=[0,0] to the connection state designation circuit 310.

[0148] When the connection state specification circuit 310 receives a print data signal SI including the individual specification signal Sd[m]=[1,1] and the individual specification signals Sd[1]~Sd[m-1],Sd[m+1]~Sd[M]=[0,0], during the control periods TT1 and TT2, switch Wc[m] is controlled to conduct, and switches Wc[1]~Wc[m-1],Wc[m+1]~Wc[M] are controlled to not conduct. Therefore, during the control periods TT1 and TT2, the upper electrode Zu[m] receives a supply drive signal VIN[m] whose voltage value starts at the reference potential V0, changes to a potential VS1 lower than the reference potential V0, then becomes a potential VS2 higher than the reference potential V0, and maintains the potential VS2. The reference potential V0 is maintained at Zu[M]. At this time, residual vibration occurs in the discharge section D[m] under inspection when the voltage value of the supplied supply drive signal VIN[m] becomes constant at potential VS2. Then, the piezoelectric element Zm[m] deforms in response to the residual vibration generated in the discharge section D[m] under inspection, and an electromotive force corresponding to the deformation of the piezoelectric element Zm[m] is generated at the upper electrode Zu[m]. In other words, a signal corresponding to the residual vibration generated in the discharge section D[m] under inspection is generated at the upper electrode Zu[m] of the piezoelectric element PZ[m] included in the discharge section D[m] under inspection.

[0149] During the control period TT2, switch Ws[m] is controlled to conduct, switches Ws[1]~Ws[m-1] and Ws[m+1]~Ws[M] are controlled to be non-conductive, and switch Wf is controlled to conduct. As a result, a signal corresponding to the residual vibration generated in the discharge section D[m] of the object being inspected propagates through the wiring Ls as a detected potential signal VX. At this time, switch W1 is controlled to conduct and switch W2 is controlled to be non-conductive. Therefore, during the control period TT2, the waveform shaping circuit 330 of the detection circuit 33 does not acquire the detected potential signal VX propagating through the wiring Ls, and therefore does not output a detected signal aSK corresponding to the detected potential signal VX.

[0150] Then, during the control period TT3, switch W1 is controlled to be non-conductive and switch W2 is controlled to be conductive, so the waveform shaping circuit 330 of the detection circuit 33 acquires a detection potential signal VX that corresponds to the residual vibration generated in the discharge section D[m] of the object to be inspected and propagates through the wiring Ls, and shapes the signal waveform of the acquired detection potential signal VX and outputs it as a detection signal aSK. This detection signal aSK output by the waveform shaping circuit 330 is converted into a digital signal by the AD conversion circuit 331 and then input to the judgment unit 7 as a detection signal SK.

[0151] The determination unit 7 calculates waveform information such as amplitude, period, and frequency of the detected potential signal VX, which is the waveform information of the residual vibration generated in the discharge section D[m] under inspection, based on the input detection signal SK. Then, the determination unit 7 determines the state of the discharge section D[m] under inspection based on the calculated waveform information and outputs a state determination signal JH indicating the determination result to the control unit 2.

[0152] Specifically, the determination unit 7 determines that there is an abnormality in the viscosity of the liquid stored in the discharge unit D under inspection if the amplitude and amplitude attenuation rate of the residual vibration included in the calculated waveform information differ from the amplitude and amplitude attenuation rate of the residual vibration that occurs in a normal discharge unit D. Furthermore, if the frequency of the residual vibration included in the calculated waveform information differs from the frequency of the residual vibration that occurs in a normal discharge unit D, it determines that air bubbles are mixed inside the discharge unit D under inspection. Also, if a short-circuit abnormality occurs in the piezoelectric element PZ included in the discharge unit D under inspection, the piezoelectric element PZ will not output a signal corresponding to the residual vibration, even if residual vibration occurs in the discharge unit D. The determination unit 7 determines that a short-circuit abnormality occurs in the piezoelectric element PZ included in the discharge unit D under inspection if no residual vibration is detected in the calculated waveform information. In other words, the determination unit 7 determines the state of the discharge unit D[m] under inspection based on the input detection signal SK and outputs a state determination signal JH indicating the determination result to the control unit 2.

[0153] During the subsequent control period TT4, switch W1 is controlled to conduct and switch W2 is controlled to deconduct, causing the waveform shaping circuit 330 to stop acquiring the detection potential signal VX propagating through the wiring Ls and to stop outputting the detection signal aSK. Then, during the control period TT5, switch Wc[m] is controlled to conduct and switch Ws[m] is controlled to deconduct, stopping the supply of the signal generated at the upper electrode Zu[m] to the wiring Ls, and simultaneously supplying a reference potential V0 drive signal VIN[m] to the upper electrode Zu[m] of the piezoelectric element PZ[m] of the discharge unit D[m] under inspection. As a result, the piezoelectric element of the discharge unit D[m] under inspection The potential of the upper electrode Zu[m] of element PZ[m] is controlled to the reference potential V0.

[0154] 5.3 Maintenance Procedures Next, an example of maintenance processing to attempt to restore the discharge state of the discharge unit D, where a discharge abnormality occurred during the judgment process, will be described. The maintenance processing in this embodiment includes pump suction processing, flushing processing, and wiping processing. However, the maintenance processing is not limited to these and includes various processing to restore the discharge state of the discharge unit D.

[0155] Figure 17 shows an example of a pump suction process. As shown in Figure 17, the pump suction process is performed using a cap 351, a tube 352, a pump 353, and a waste liquid tank 354.

[0156] The cap 351 is positioned to cover the multiple head units 3 mounted on the carriage 91 from the discharge surface 115 side. One end of the tube 352 is attached to the cap 351. The other end of the tube 352 is connected to the waste liquid tank 354 via the pump 353.

[0157] Then, when the pump 353 operates, air inside the cap 351 is drawn in. This causes the ink stored in the multiple ejection nozzles D of the head unit 3 to be introduced into the waste liquid tank 354. At this time, ink that has solidified near the nozzles N of the ejection nozzles D and air bubbles that have entered inside the ejection nozzles D are removed.

[0158] Furthermore, as shown in Figure 17, the cap 351 may have an ink absorber 359 inside. The ink absorber 359 absorbs the ink sucked from the nozzle N during the pump suction process and temporarily stores it. This reduces the risk of the sucked ink splashing back and adhering to the discharge surface 115 during the period in which the pump suction process is being performed.

[0159] Figure 18 shows an example of a wiping process. As shown in Figure 18, the wiping process is performed by a wiper 360 including a wiping member 361. As shown in Figure 18(a), the wiper 360 is provided so as to be movable in the vertical direction of Figure 18, including a range in which the wiping member 361 can contact the discharge surface 115. When the wiping process is performed, the wiper 360 moves so that at least a portion of the wiping member 361 is above the discharge surface 115 in Figure 18. Subsequently, the carriage 91 on which the head unit 3 is mounted moves in the direction along the arrow shown in Figure 18 due to the operation of the carriage movement unit 9. As a result, the wiping member 361 contacts the discharge surface 115, as shown in Figure 18(b).

[0160] Here, the wiping member 361 is made of a plastic rubber or the like. Therefore, when the wiping member 361 comes into contact with the dispensing surface 115, the tip of the wiping member 361 flexes. This allows the wiping member 361 to wipe the surface of the dispensing surface 115, removing any paper fragments or other materials adhering to the dispensing surface 115.

[0161] The flushing process involves simultaneously ejecting ink from multiple nozzles N included in the multiple ejection sections D of the target head unit 3, for example, with the cap 351 shown in Figure 17 attached. This flushing process refreshes the ink stored in the multiple ejection sections D of the head unit 3. As a result, the viscosity of the ink stored in the multiple ejection sections D of the head unit 3 is maintained within an appropriate range, and the viscosity of the ink is restored to an appropriate range. Note that the flushing process only requires a configuration that allows ink to be simultaneously ejected from multiple nozzles N included in the multiple ejection sections D of the head unit 3. Therefore, the flushing process may be configured such that, with the cap 351 attached to the head unit 3, a predetermined print data signal SI is input to the head unit 3, supplying a drive signal COM containing a predetermined signal waveform to a plurality of ejection units D, and simultaneously ejecting ink from a plurality of nozzles N included in the plurality of ejection units D.

[0162] Here, the control unit 2 may, based on the status determination signal JH output by the determination unit 7 described above, select one of the pump suction process, flushing process, or wiping process described above as a maintenance process and have the maintenance unit 10 execute it. For example, if the control unit 2 determines, based on the status determination signal JH, that the cause of the discharge abnormality occurring in the discharge unit D is the incorporation of air bubbles into the discharge unit D, it will have the maintenance unit 10 execute the pump suction process. If the control unit 2 determines, based on the status determination signal JH, that the cause of the discharge abnormality occurring in the discharge unit D is increased ink viscosity, it will have the maintenance unit 10 execute either the flushing process or the pump suction process. If the control unit 2 determines, based on the status determination signal JH, that the cause of the discharge abnormality occurring in the discharge unit D is the adhesion of paper fragments to the discharge surface 115, it will have the maintenance unit 10 execute the wiping process. In this way, the maintenance unit 10 attempts to restore the state of the discharge unit D where the discharge abnormality occurred.

[0163] Furthermore, if a discharge abnormality occurs in any of the multiple discharge sections D of the head unit 3, the maintenance unit 10 may perform all of the following: pump suction, flushing, and wiping.

[0164] In other words, the liquid dispensing device 1 of this embodiment includes a maintenance unit 10 that performs maintenance on the dispensing unit D in order to attempt to restore the state of the dispensing unit D. The maintenance unit 10 performs a wiping process to wipe the dispensing surface 115 from which ink is dispensed from the head unit 3 and the recording head 32, and a flushing process to dispense liquid from multiple dispensing units D in order to restore the viscosity of the stored ink.

[0165] 6. Operation of the liquid dispensing device The operation of the liquid dispensing device 1, which performs various processes including the dispensing process, judgment process, and maintenance process described above, will now be explained.

[0166] Figure 19 is a diagram illustrating the operation of the liquid dispensing device 1. As shown in Figure 19, when the liquid dispensing device 1 starts operating, the control unit 2 reads out dispensing unit status information from a memory circuit (not shown) (step S10) and holds it. Here, the dispensing unit status information read out and held by the control unit 2 is information regarding the dispensing status of dispensing units D[1] to D[M] stored in the memory circuit of the control unit 2 in accordance with the status determination signal JH input to the control unit 2 in the determination process. This information includes, for example, whether or not a dispensing abnormality has occurred in each of the dispensing units D[1] to D[M], information regarding the type of dispensing abnormality in the dispensing unit D where a dispensing abnormality has occurred, and information regarding the number of dispensing units D[1] to D[M] where a dispensing abnormality has occurred.

[0167] Subsequently, the liquid dispensing device 1 performs the determination process described using Figures 13 to 16 (step S20). Specifically, when the determination process starts, the control unit 2 generates a clock signal CL, a print data signal SI, a latch signal LAT, a change signal CH, a period specification signal Tsig, and a drive waveform specification signal dCOM, designating the dispensing unit D[1] as the dispensing unit D to be inspected, and outputs them to the corresponding configuration. As a result, the control unit 2 receives a state determination signal JH corresponding to the dispensing unit D[1]. As a result, the control unit 2 obtains information on the determination result of whether or not a dispensing abnormality has occurred in the dispensing unit D[1], and, if a dispensing abnormality has occurred in the dispensing unit D[1], information on the type of dispensing abnormality.

[0168] Similarly, the control unit 2 generates a clock signal CL, a print data signal SI, a latch signal LAT, a change signal CH, a period specification signal Tsig, and a drive waveform specification signal dCOM, which sequentially designate the ejection units D[2] to D[M] as the ejection units D to be inspected, and outputs them to the corresponding configurations. As a result, the control unit 2 receives sequential status determination signals JH corresponding to each of the ejection units D[2] to D[M]. That is, the control unit 2 sequentially acquires information on the determination result of whether or not an ejection abnormality has occurred in each of the ejection units D[2] to D[M], and, if an ejection abnormality has occurred, information on the type of ejection abnormality.

[0169] In the following explanation, we will assume that the control unit 2 obtains all the determination results regarding whether or not a discharge abnormality has occurred in each of the discharge sections D[1] to D[M] in a single determination process. However, the control unit 2 may be configured to perform the determination of whether or not a discharge abnormality has occurred in each of the discharge sections D[1] to D[M] in multiple determination processes. For example, the control unit 2 may obtain the determination results regarding whether or not a discharge abnormality has occurred in each of the discharge sections D[1] to D[m] within the discharge sections D[1] to D[M] in the first determination process, and then obtain the determination results regarding whether or not a discharge abnormality has occurred in each of the discharge sections D[m+1] to D[M] within the discharge sections D[1] to D[M] in the second determination process.

[0170] Then, after the determination process in step S20 is completed, the control unit 2 updates the stored discharge unit status information according to the determination result of whether or not a discharge abnormality has occurred in each of the acquired discharge units D[1] to D[M] (step S30). Specifically, the control unit 2 updates information on whether or not a discharge abnormality has occurred in each of the stored discharge units D[1] to D[M], information on the type of discharge abnormality if one has occurred, and information on the number of discharge units D[1] to D[M] in which a discharge abnormality has occurred, based on the determination result of the determination process in step S20.

[0171] Then, the control unit 2 determines whether or not the discharge process can be executed based on the updated discharge unit status information it holds (step S40). Specifically, the control unit 2 determines whether or not a discharge abnormality has occurred in each of the discharge units D[1] to D[M] included in the discharge unit status information it holds, and whether or not it is possible to compensate for the discharge unit D experiencing a discharge abnormality through a compensation process. The control unit 2 may then determine that the discharge process can be executed if a compensation process is possible, and that the discharge process cannot be executed if a compensation process is not possible. The control unit 2 also determines whether or not the number of discharge units D[1] to D[M] included in the discharge unit status information it holds that are experiencing a discharge abnormality exceeds a predetermined number. The control unit 2 may then determine that the discharge process can be executed if the number of discharge units D experiencing a discharge abnormality is less than or equal to the predetermined number, and that the discharge process cannot be executed if the number of discharge units D experiencing a discharge abnormality exceeds the predetermined number. If the control unit 2 determines that it is not possible to perform the dispensing process (N in step S40), the control unit 2 terminates the process and the liquid dispensing device 1 stops operating. At this time, the control unit 2 may notify the user that it is not possible to perform the dispensing process via a notification function (not shown).

[0172] If the control unit 2 determines that it is possible to perform the ejection process (step S40, Y), the control unit 2 determines whether or not an image data signal IMG has been input (step S50). If an image data signal IMG has not been input (step S50, N), the control unit 2 waits until an image data signal IMG is input.

[0173] Subsequently, when the image data signal IMG is input to the control unit 2 (Y in step S50), the liquid dispensing device 1 executes the dispensing process described using Figures 11 and 12 (step S60). Specifically, when the dispensing process starts, the control unit 2 generates individual designation signals Sd[1] to Sd[M] corresponding to the input image data signal IMG. Then, control Based on the stored ejection unit status information, unit 2 generates a print data signal SI by setting the individual designation signal Sd=[0,0] for ejection unit D where a short circuit abnormality of the piezoelectric element PZ has occurred, and the individual designation signal Sd=[0,1] for ejection unit D where ejection abnormalities other than the short circuit abnormality of the piezoelectric element PZ have occurred, and by performing a compensation process to compensate for the ejection of ink from ejection unit D where ejection abnormalities including the short circuit abnormality have occurred. Subsequently, control unit 2 outputs the generated print data signal SI, clock signal CL, latch signal LAT, change signal CH, period designation signal Tsig, and drive waveform designation signal dCOM in the corresponding configuration. As a result, head unit 3 ejects ink according to the print data signal SI, clock signal CL, latch signal LAT, change signal CH, period designation signal Tsig, and drive waveform designation signal dCOM. As a result, dots are formed at predetermined positions on the medium P.

[0174] In other words, if the determination unit 7 determines that a short circuit abnormality has occurred in the ejection section D[1], the switch Wc[1] does not supply the drive signal COM to the piezoelectric element PZ[1] during the unit period TP in which the ejection process in which ink is ejected from the head unit 3 is performed. If the determination unit 7 determines that a short circuit abnormality has occurred in the ejection section D[m], the switch Wc[m] does not supply the drive signal COM to the piezoelectric element PZ[m] during the unit period TP in which the ejection process in which ink is ejected from the head unit 3 is performed. Furthermore, if the determination unit 7 determines that a discharge abnormality, including a short circuit abnormality, has occurred in the discharge section D[1], the switch Wc[1] does not supply the drive signal COM to the piezoelectric element PZ[1] during the unit period TP in which the discharge process in which ink is discharged from the head unit 3 is performed. Similarly, if the determination unit 7 determines that a discharge abnormality, including a short circuit abnormality, has occurred in the discharge section D[m], the switch Wc[m] does not need to supply the drive signal COM to the piezoelectric element PZ[m] during the unit period TP in which the discharge process in which ink is discharged from the head unit 3 is performed.

[0175] If the determination unit 7 determines that a short circuit abnormality or an ejection abnormality including a short circuit abnormality has occurred in ejection unit D[1], ejection unit D[2], which is located adjacent to ejection unit D[1] and which the determination unit 7 has determined does not have an ejection abnormality including a short circuit abnormality, will eject ink to complement ejection unit D[1] during the unit period TP of the period in which the ejection process in which ink is ejected from the head unit 3 is performed. If the determination unit 7 determines that a short circuit abnormality or an ejection abnormality including a short circuit abnormality has occurred in ejection unit D[m], at least one of ejection unit D[m-1] and ejection unit D[m+1], which is located adjacent to ejection unit D[m] and which the determination unit 7 has determined does not have an ejection abnormality including a short circuit abnormality, will eject ink to complement ejection unit D[m] during the unit period TP of the period in which the ejection process in which ink is ejected from the head unit 3 is performed.

[0176] Furthermore, the control unit 2 determines whether or not a request to execute a judgment process has occurred (step S70). Such a request to execute a judgment process may occur, for example, when the operating direction of the carriage 91 on which the head unit 3 is mounted changes, or between sheets of paper of the conveyed medium P.

[0177] Then, if the control unit 2 determines that a request to execute a determination process has arisen (Y in step S70), the liquid dispensing device 1 executes the same determination process as in step S20 (step S71), and the control unit 2 updates the stored dispensing unit state information according to the determination result in the determination process in step S71, as in step S30 (step S72). Then, as in step S40, the control unit 2 determines whether or not it is possible to execute the dispensing process based on the updated stored dispensing unit state information updated in step S72 (step S73). If the control unit 2 determines that it is not possible to execute the dispensing process (N in step S73), the control unit 2 terminates the process, and the liquid dispensing device 1 stops operating.

[0178] Then, if the control unit 2 determines that the ejection process can be performed (Y in step S73), or if the control unit 2 determines that no request for execution of the determination process has occurred (N in step S70), the control unit 2 determines whether or not a request for execution of the maintenance process has occurred (step S80). Such a request for execution of the maintenance process may occur, for example, after the determination process determines that a new ejection abnormality has occurred in the ejection units D[1] to D[M], at the timing when the operating direction of the carriage 91 equipped with the head unit 3 is switched, or between sheets of paper of the transported medium P. Alternatively, it may occur after the cumulative operating time or continuous operating time of the liquid ejection device 1, or the number of sheets of medium P from which ink has been ejected has reached a predetermined threshold, at the timing when the operating direction of the carriage 91 equipped with the head unit 3 is switched, between sheets of paper of the transported medium P, or at the timing when the formation of an image corresponding to the image data signal IMG is completed.

[0179] If the control unit 2 determines that a request to perform maintenance processing has occurred (Y in step S80), the control unit 2 instructs the maintenance unit 10 to perform the maintenance processing described above, such as the pump suction processing, flushing processing, and wiping processing (step S81). After the maintenance processing in the maintenance unit 10 is completed, the liquid dispensing device 1 performs the same determination process as in step S20 (step S82), and the control unit 2 updates the dispensing unit status information it holds according to the determination result in the determination process in step S82, as in step S30 (step S83). Then, as in step S40, the control unit 2 determines whether or not it is possible to perform dispensing processing based on the dispensing unit status information updated in step S83 (step S84). If the control unit 2 determines that it is not possible to perform dispensing processing (N in step S84), the control unit 2 terminates the process, and the liquid dispensing device 1 stops operating.

[0180] Then, if the control unit 2 determines that no request for maintenance processing has arisen (N in step S80), or if it determines that the ejection process can be performed (Y in step S84), the control unit 2 determines whether the ejection process corresponding to the image data signal IMG, which involves forming the image on the medium P, has been completed (step S90). If the control unit 2 determines that the ejection process corresponding to the image data signal IMG has not been completed (N in step S90), the processes in steps S60 to S80 described above are repeatedly executed.

[0181] On the other hand, if the control unit 2 determines that the ejection process corresponding to the image data signal IMG is complete (step S90, Y), or if the control unit 2 determines that it is not possible to perform the ejection process (step S40, step S73, step S84, N), before the liquid ejection device 1 stops operating, the control unit 2 stores the ejection unit status information it holds in a memory circuit (not shown) that the control unit 2 has (step S100). Then the liquid ejection device 1 stops operating.

[0182] The head unit 3 and the recording head 32 of the head unit 3 are examples of print heads, the ejection units D[1] to D[M] are examples of multiple ejection units, and any one of the ejection units D[1] to D[M] is, for example, ejection unit D[1] is an example of a first ejection unit, in which case the piezoelectric element PZ[1] included in ejection unit D[1] is an example of a first piezoelectric element, and the switch Wc[1] corresponding to the piezoelectric element PZ[1] is an example of a first switch circuit. Yes, it is one of the discharge sections D[1] to D[M], for example, discharge section D[m] is an example of a second discharge section, in which case the piezoelectric element PZ[m] included in discharge section D[m] is an example of a second piezoelectric element, the switch Wc[m] corresponding to the piezoelectric element PZ[m] is an example of a second switch circuit, and it is one of the discharge sections D[1] to D[M], for example, discharge section D[2] located adjacent to discharge section D[1] is an example of a third discharge section. Also, the determination unit 7 is an example of a state determination circuit, the maintenance unit 10 is an example of a maintenance section, the transistor 403 is an example of a switch circuit, and the resistor 410 is a resistive element This is an example of a child, where wiring Lb is an example of the first wiring, and wiring Lg is an example of the second wiring. Furthermore, the ejection process in which ink is ejected from the head unit 3 is performed, and the unit period TP in which the ejection process is performed is an example of the ejection period.

[0183] 7. Effects As described above, the liquid dispensing device 1 of this embodiment includes a head unit 3 having dispensing sections D[1] to D[M], including a dispensing section D[1] that dispenses ink by driving a piezoelectric element PZ[1], and a dispensing section D[m] that dispensing ink by driving a piezoelectric element PZ[m], a drive circuit 50 that outputs a drive signal COM supplied to the upper electrode Zu[1] which is one end of the piezoelectric element PZ[1], and the upper electrode Zu[m] which is one end of the piezoelectric element PZ[m], and a reference voltage signal supplied to the lower electrode Zd[1] which is the other end of the piezoelectric element PZ[1], and the lower electrode Zd[m] which is the other end of the piezoelectric element PZ[m] The system includes a reference voltage circuit 530 that outputs VBS, a switch Wc[1] that switches whether or not to supply a drive signal COM to the upper electrode Zu[1] which is one end of the piezoelectric element PZ[1], a switch Wc[m] that switches whether or not to supply a drive signal COM to the upper electrode Zu[m] which is one end of the piezoelectric element PZ[m], a determination unit 7 that determines the state of each of the discharge sections D[1] to D[M], and a sink circuit 40 that switches the impedance value between the wiring Lb through which the reference voltage signal VBS propagates and the wiring Lg through which a signal with a ground potential lower than the reference voltage signal VBS propagates. Furthermore, in the liquid ejection device 1 of this embodiment, if the determination unit 7 determines that a short-circuit abnormality has occurred in the ejection section D[1], the switch Wc[1] does not supply the drive signal COM to the piezoelectric element PZ[1] during the unit period TP of the period in which the ejection process in which ink is ejected from the head unit 3 is performed. If the determination unit 7 determines that a short-circuit abnormality has occurred in the ejection section D[m], the switch Wc[m] does not supply the drive signal COM to the piezoelectric element PZ[m] during the unit period TP of the period in which the ejection process in which ink is ejected from the head unit 3 is performed.

[0184] In the liquid dispensing device 1 of this embodiment, configured as described above, if a short-circuit abnormality occurs in the piezoelectric element PZ[1] of the dispensing unit D[1], the switch Ws[1] does not supply a drive signal COM to the piezoelectric element PZ[1], thus reducing the risk of excess current flowing into the wiring Lb through which the reference voltage signal VBS propagates via the piezoelectric element PZ[1]. Therefore, the risk of the voltage value of the wiring Lb through which the reference voltage signal VBS propagates rising due to a short-circuit abnormality in the piezoelectric element PZ[1] of the dispensing unit D[1] is reduced. Similarly, if a short-circuit abnormality occurs in the piezoelectric element PZ[m] of the dispensing unit D[m], the switch Ws[m] does not supply a drive signal COM to the piezoelectric element PZ[m], thus reducing the risk of excess current flowing into the wiring Lb through which the reference voltage signal VBS propagates via the piezoelectric element PZ[m]. Therefore, the risk of the voltage value of the wiring Lb through which the reference voltage signal VBS propagates rising due to a short-circuit abnormality in the piezoelectric element PZ[m] of the discharge section D[m] is reduced. In other words, in the liquid discharge device 1 of this embodiment, if a short-circuit abnormality occurs in the discharge section D including the piezoelectric element PZ, and if it is possible to form an image on the medium P in the discharge section D where the abnormality does not occur, the liquid discharge device 1 can continue to form an image on the medium P, even if the image quality deteriorates.

[0185] Furthermore, in the liquid dispensing device 1 of this embodiment, the determination unit 7 determines the state of each of the dispensing sections D[1] to D[M]. If an abnormality occurs in the dispensing section D including the piezoelectric element PZ, and it is difficult to form an image on the medium P using the dispensing section D that is not abnormal, the liquid dispensing device 1 can stop forming an image on the medium P. Therefore, the risk of the dispensing process continuing with a degraded image quality formed on the medium P is reduced.

[0186] Furthermore, in the liquid dispensing device 1 of this embodiment, because the sinking capacity in the sink circuit 40 is constant, the voltage of the wiring Lb is affected by factors other than abnormalities in the dispensing section D including the piezoelectric element PZ. If the value increases, the rise in the voltage value can be detected by an overvoltage detection circuit (not shown), which can stop the image formation on the medium P in the liquid dispensing device 1. Therefore, the risk of the dispensing process continuing with a degraded image quality formed on the medium P is reduced.

[0187] As described above, the liquid dispensing device 1 of this embodiment can appropriately switch between continuing and stopping image formation on the medium P. Therefore, the risk of a decrease in productivity and convenience in the liquid dispensing device 1 can be reduced, and the risk of a decrease in the image quality formed on the medium P in the liquid dispensing device 1 can also be reduced.

[0188] Furthermore, in the liquid dispensing device 1 of this embodiment, the determination unit 7 determines the state of the multiple dispensing parts D in accordance with the residual vibration generated in the multiple dispensing parts D, and therefore can determine the state of each dispensing part D[1] to D[M] individually with high accuracy. Consequently, the determination accuracy of the state of the multiple dispensing parts D by the determination unit 7 is improved. Thus, in the liquid dispensing device 1 of this embodiment, the risk of decreased productivity and convenience can be further reduced, as can the risk of decreased image quality formed on the medium P.

[0189] Although embodiments and modified examples have been described above, the present invention is not limited to these embodiments and can be implemented in various forms without departing from its spirit. For example, the above embodiments can be combined as appropriate.

[0190] The present invention includes configurations that are substantially identical to those described in the embodiments (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect). Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Furthermore, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0191] The following conclusions can be drawn from the embodiments described above.

[0192] One embodiment of a liquid dispensing device is: A print head having a plurality of discharge sections, including a first discharge section that discharges liquid by driving a first piezoelectric element, and a second discharge section that discharges liquid by driving a second piezoelectric element, A drive circuit that outputs a drive signal supplied to one end of the first piezoelectric element and one end of the second piezoelectric element, A reference voltage circuit that outputs a reference voltage signal supplied to the other end of the first piezoelectric element and the other end of the second piezoelectric element, A first switch circuit that switches whether or not to supply the drive signal to one end of the first piezoelectric element, A second switch circuit for switching whether or not to supply the drive signal to one end of the second piezoelectric element, A state determination circuit for determining the state of the plurality of discharge units, A sink circuit that switches the impedance value between a first wiring through which the reference voltage signal propagates and a second wiring through which a signal with a lower potential than the reference voltage signal propagates. Equipped with, If the state determination circuit determines that an abnormality has occurred in the first ejection unit, the first switch circuit will not supply the drive signal to the first piezoelectric element during the ejection period in which liquid is ejected from the print head. If the state determination circuit determines that an abnormality has occurred in the second discharge unit, the second switch circuit will not supply the drive signal to the second piezoelectric element during the discharge period.

[0193] In this liquid ejection device, if a state determination circuit that determines the state of multiple ejection units determines that an abnormality has occurred in the first ejection unit, the first switch does not supply a drive signal to one end of the first piezoelectric element of the first ejection unit during the ejection period in which liquid is ejected from the print head. Similarly, if the state determination circuit determines that an abnormality has occurred in the second ejection unit, the first switch does not supply a drive signal to one end of the second piezoelectric element of the second ejection unit during the ejection period in which liquid is ejected from the print head. As a result, even if an abnormality such as a short circuit occurs in either the first or second piezoelectric element, the risk of excess current flowing into the first wiring through which the reference voltage signal propagates is reduced. Therefore, the risk of the voltage value of the first wiring rising due to a short circuit in the first piezoelectric element of the first ejection unit is reduced, and similarly, the risk of excess current flowing into the first wiring due to a short circuit in the second piezoelectric element of the second ejection unit is reduced. In other words, in this liquid dispensing device, if a short-circuit malfunction occurs in one of the piezoelectric elements of the multiple dispensing sections, and if the other dispensing sections that are not malfunctioning can still form an image on the medium, image formation can continue without degrading the quality of the formed image.

[0194] Furthermore, in this liquid dispensing device, a state determination circuit determines the state of each of the multiple dispensing sections. This allows the device to stop image formation on the medium if an abnormality occurs in any of the multiple dispensing sections, each containing a piezoelectric element, and if the remaining dispensing section is unable to form an image on the medium. Therefore, the risk of the dispensing process continuing with a degraded image quality is reduced.

[0195] Furthermore, in this liquid dispensing device, because the sinking capacity in the sink circuit is constant, if the voltage value of the first wiring through which the reference voltage signal propagates rises due to factors other than abnormalities in the dispensing section including the piezoelectric element, the rise in voltage value can be detected by an overvoltage detection circuit (not shown), and at this time, image formation on the medium can be stopped. Therefore, the risk of the dispensing process continuing with a degraded image quality formed on the medium is reduced.

[0196] As described above, this liquid dispensing device can appropriately switch between continuing and stopping image formation on the medium. Therefore, the risk of decreased productivity and convenience in the liquid dispensing device can be reduced, as can the risk of decreased image quality formed on the medium in the liquid dispensing device.

[0197] In one embodiment of the liquid dispensing device, The system may further include a maintenance unit for performing maintenance on the discharge unit.

[0198] In one embodiment of the liquid dispensing device, The maintenance unit may perform a wiping process as part of the maintenance process, which involves wiping the ejection surface from which liquid is ejected from the print head.

[0199] In one embodiment of the liquid dispensing device, The maintenance unit may perform a flushing process as part of the maintenance process, in which it discharges liquid from the plurality of discharge ports in order to restore the viscosity of the stored liquid.

[0200] These liquid ejection devices have a maintenance unit that performs maintenance processing to restore the state of the ejection unit. As part of the maintenance processing, a wiping process is performed to wipe the ejection surface from which ink is ejected from the print head, and a flushing process is performed to simultaneously eject liquid from multiple ejection units to restore the viscosity of the stored liquid. Even if the state of the ejection unit is restored, the first switch circuit and the second switch circuit are controlled according to the state determination result of the state of multiple ejection units in the state determination circuit, thereby continuing image formation on the medium. The stopping and stopping states can be controlled to an optimal state based on the most recent state of multiple dispensing units. Therefore, the risk of decreased productivity and convenience of the liquid dispensing device can be further reduced, as can the risk of decreased image quality formed on the medium.

[0201] In one embodiment of the liquid dispensing device, The aforementioned drive circuit may include a Class D amplifier circuit.

[0202] In one embodiment of the liquid dispensing device, The sink circuit may be configured to include discrete components.

[0203] In one embodiment of the liquid dispensing device, If the state determination circuit determines that an abnormality has occurred in the first discharge unit, the third discharge unit, which is located adjacent to the first discharge unit and which the state determination circuit has determined is not abnormal, may discharge liquid during the discharge period in a manner that complements the first discharge unit.

[0204] In one embodiment of the liquid dispensing device, The state determination circuit may determine the state of the first discharge section in accordance with the residual vibration generated in the first discharge section, and determine the state of the second discharge section in accordance with the residual vibration generated in the second discharge section.

[0205] In this liquid dispensing device, the state determination circuit determines the state of the first dispensing unit in accordance with the residual vibration generated in the first dispensing unit, and determines the state of the second dispensing unit in accordance with the residual vibration generated in the second dispensing unit, thereby enabling high-precision individual determination of the states of multiple dispensing units. Consequently, the accuracy of the state determination circuit's determination of the states of multiple dispensing units is improved, and the continuation and cessation of image formation on the medium can be controlled to the optimal state based on the most recent states of the multiple dispensing units. Therefore, the risk of decreased productivity and convenience of the liquid dispensing device can be further reduced, as can the risk of decreased image quality formed on the medium.

[0206] In one embodiment of the liquid dispensing device, The sink circuit includes a switch circuit and a resistor element. One end of the switch circuit is electrically connected to the first wiring, The other end of the switch circuit is electrically connected to one end of the resistive element. The other end of the resistive element may be electrically connected to the second wiring. [Explanation of symbols]

[0207] 1...Liquid dispensing device, 2...Control unit, 3...Head unit, 4...Sink unit, 5...Drive circuit unit, 7...Determination unit, 8...Transport unit, 9...Carriage movement unit, 10...Maintenance unit, 31...Supply switching circuit, 32...Recording head, 33...Detection circuit, 40...Sink circuit, 50...Drive circuit, 81...Media transport mechanism, 82...Platen, 91...Carriage, 92...Carriage transport mechanism, 93...Carriage guide shaft, 100...Housing, 115...Dispensing surface, 120...Ink cartridge, 310...Connection status specification circuit, 321...Diaphragm, 322...Cavity, 323...Nozzle plate, 324...Cavity plate 325...Reservoir, 326...Ink supply port, 327...Ink intake, 330...Waveform shaping circuit, 331...AD conversion circuit, 351...Cap, 352...Tube, 353...Pump, 354...Waste liquid tank, 359...Ink absorber, 360...Wiper, 361...Wiping material, 401...Resistor, 402...Constant voltage diode, 403...Transistor, 410...Resistor, 500...Integrated circuit, 510...Modulation circuit, 512,513...Adder, 514...Comparator, 515...Inverter, 516...Integrating attenuator, 517...Attenuator, 520...Gate drive circuit, 521,522...Gate driver, 530...Reference voltage circuit, 531...Co Amplifier, 532...transistor, 534, 535...resistor, 550...amplifier circuit, 560...demodulation circuit, 570, 572...feedback circuit, C1~C5...capacitor, D...discharge unit, D1...diode, L1...coil, Lb, Lc, Lg, Ls...wiring, M1, M2...transistor, N...nozzle, NL...nozzle row, OP1, OP2...operation amplifier, P...medium, PZ...piezoelectric element, R1~R6, Rf...resistor, W1, W2, Wc, Wf, Ws...switch, Zd...lower electrode, Zm...piezoelectric material, Zu...upper electrode

Claims

1. A print head having a plurality of discharge sections, including a first discharge section that discharges liquid by driving a first piezoelectric element, and a second discharge section that discharges liquid by driving a second piezoelectric element, A drive circuit that outputs a drive signal supplied to one end of the first piezoelectric element and one end of the second piezoelectric element, A reference voltage circuit that outputs a reference voltage signal supplied to the other end of the first piezoelectric element and the other end of the second piezoelectric element, A first switch circuit that switches whether or not to supply the drive signal to one end of the first piezoelectric element, A second switch circuit for switching whether or not to supply the drive signal to one end of the second piezoelectric element, A state determination circuit for determining the state of the plurality of discharge units, A sink circuit that switches the impedance value between a first wiring through which the reference voltage signal propagates and a second wiring through which a signal with a lower potential than the reference voltage signal propagates. Equipped with, If the state determination circuit determines that an abnormality has occurred in the first ejection unit, the first switch circuit will not supply the drive signal to the first piezoelectric element during the ejection period in which liquid is ejected from the print head. If the state determination circuit determines that an abnormality has occurred in the second discharge unit, the second switch circuit shall not supply the drive signal to the second piezoelectric element during the discharge period. A liquid dispensing device characterized by the following features.

2. The system further includes a maintenance unit that performs maintenance processing on the discharge unit. The liquid dispensing device according to feature 1.

3. The maintenance unit performs a wiping process as part of the maintenance process, which involves wiping the ejection surface from which liquid is ejected from the print head. The liquid dispensing device according to feature 2.

4. The maintenance unit performs a flushing process as part of the maintenance process, in which it discharges liquid from the plurality of discharge units in order to restore the viscosity of the stored liquid. The liquid dispensing device according to feature 2.

5. The aforementioned drive circuit includes a Class D amplifier circuit. The liquid dispensing device according to feature 1.

6. The sink circuit is composed of discrete components, The liquid dispensing device according to feature 1.

7. If the state determination circuit determines that an abnormality has occurred in the first discharge unit, the third discharge unit, which is located adjacent to the first discharge unit and which the state determination circuit determines is not abnormal, will discharge liquid during the discharge period in a manner that complements the first discharge unit. The liquid dispensing device according to feature 1.

8. The state determination circuit determines the state of the first discharge unit according to the residual vibration generated in the first discharge unit, and determines the state of the second discharge unit according to the residual vibration generated in the second discharge unit. The liquid dispensing device according to feature 1.

9. The sink circuit includes a switch circuit and a resistor element. One end of the switch circuit is electrically connected to the first wiring, The other end of the switch circuit is electrically connected to one end of the resistive element. The other end of the resistive element is electrically connected to the second wiring. A liquid dispensing device according to any one of claims 1 to 8.

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