Liquid dispensing device and head unit

Abstract

To determine presence / absence of foreign matters adhered to an inner wall of a nozzle opening.SOLUTION: There is provided a liquid discharge device comprising: a supply part for supplying, to a piezoelectric element, a first drive signal for driving a piezoelectric element for discharging liquid from a nozzle opening and for forming an image on a medium, and a second drive signal for driving the piezoelectric element for determining absence / presence of foreign matters adhered to the inner wall of the nozzle opening, selectively; and a determination part for determining presence / absence of the foreign matters adhered to the inner wall. The second drive signal includes: a first partial signal which is changed from a first potential to a second potential; and a second partial signal which is changed from the second potential to the first potential. The determination part determines absence / presence of the foreign matters adhered to the inner wall, on the basis of vibration generated on the piezoelectric element when the second partial signal is supplied, after the first piezoelectric signal is supplied to the piezoelectric element.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] In a liquid ejection device such as an inkjet printer, by driving a piezoelectric element provided in a discharge portion included in the liquid ejection device with a drive signal, a liquid such as ink filled in the discharge portion is discharged from a nozzle opening provided in the discharge portion to form an image on a medium such as a recording paper. In such a liquid ejection device, there may be a discharge abnormality in which the nozzle opening is clogged due to thickening or the like of the liquid filled in the discharge portion, and the liquid cannot be normally discharged from the nozzle opening. When a discharge abnormality occurs, dots that are supposed to be formed on the medium by the liquid discharged from the discharge portion cannot be normally formed, and the image quality of the image formed on the medium deteriorates. In Patent Document 1, in order to prevent deterioration of image quality associated with discharge abnormality in advance, a technique for determining the presence or absence of discharge abnormality in a discharge portion based on the characteristics of vibrations generated in a piezoelectric element driven by a drive signal has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional technology, when a discharge abnormality occurs due to foreign matter adhering to the inner wall of the nozzle opening, the influence on the characteristics of vibrations generated in the piezoelectric element driven by the drive signal is slight, and there is a problem that the presence or absence of discharge abnormality in the discharge portion cannot be determined.

Means for Solving the Problems

[0005] To solve the above problems, the liquid dispensing device according to the present invention comprises a supply unit capable of selectively supplying to a piezoelectric element a first drive signal for driving a piezoelectric element to dispensing liquid from a nozzle opening to form an image on a medium, and a second drive signal for driving the piezoelectric element to determine whether or not there is foreign matter attached to the inner wall of the nozzle opening, and a determination unit for determining whether or not there is foreign matter attached to the inner wall, wherein the second drive signal includes a first partial signal that changes from a first potential to a second potential and a second partial signal that changes from the second potential to the first potential, and the determination unit determines whether or not there is foreign matter attached to the inner wall based on vibrations generated in the piezoelectric element when the second partial signal is supplied after the first partial signal has been supplied to the piezoelectric element.

[0006] Furthermore, the head unit according to the present invention comprises a supply unit capable of selectively supplying to the piezoelectric element a first drive signal for driving the piezoelectric element to discharge liquid from a nozzle opening and form an image on a medium, and a second drive signal for driving the piezoelectric element to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening, and a determination unit for determining whether or not there is foreign matter adhering to the inner wall, wherein the second drive signal includes a first partial signal that changes from a first potential to a second potential, and a second partial signal that changes from the second potential to the first potential, and the determination unit determines whether or not there is foreign matter adhering to the inner wall based on vibrations generated in the piezoelectric element when the second partial signal is supplied after the first partial signal has been supplied to the piezoelectric element. [Brief explanation of the drawing]

[0007] [Figure 1] This block diagram shows an example of the configuration of an inkjet printer 1 according to an embodiment of the present invention. [Figure 2] This is a perspective view showing an example of the general internal structure of inkjet printer 1. [Figure 3] This is a cross-sectional view illustrating an example of the structure of the discharge section D[m]. [Figure 4] This is a block diagram showing an example of the configuration of the drive signal generation circuit 4R. [Figure 5] This block diagram shows an example of the configuration of head unit 3. [Figure 6] This is a timing chart illustrating an example of a signal supplied to head unit 3. [Figure 7] This is a timing chart illustrating an example of the drive signal Com-B. [Figure 8] This is an explanatory diagram illustrating an example of an individualized signal Sd[m]. [Figure 9] This is a timing chart illustrating an example of the drive signal Com-Bw. [Figure 10] This is a timing chart illustrating an example of the drive signal Com-Bz. [Figure 11] This is a cross-sectional view illustrating an example of a discharge abnormality in the first embodiment. [Figure 12] This is a cross-sectional view illustrating an example of a discharge abnormality in the second embodiment. [Figure 13] This is a cross-sectional view illustrating the periodic TC detected in Verification Example 1. [Figure 14] This is a cross-sectional view illustrating the periodic TC detected in Verification Example 1. [Figure 15] This is a cross-sectional view illustrating the periodic TC detected in Verification Example 2. [Figure 16] This is a cross-sectional view illustrating the periodic TC detected in Verification Example 2. [Figure 17] This is a timing chart illustrating an example of the drive signal Com-B related to Modification Example 1. [Figure 18] This is a timing chart illustrating an example of the drive signal Com-B related to Modification Example 2. [Figure 19] This block diagram shows an example of the configuration of inkjet printer 1A according to modified example 3. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, in each figure, the dimensions and scales of each part are appropriately different from the actual ones. Also, the embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are imposed. However, the scope of the present invention is not limited to these embodiments unless there is a description to specifically limit the present invention in the following description.

[0009] <<A. Embodiment>> In this embodiment, a liquid ejection device will be described by exemplifying an inkjet printer that ejects ink to form an image on a recording paper PP.

[0010] <<1. Outline of Inkjet Printer>> Hereinafter, an example of the configuration of an inkjet printer 1 according to this embodiment will be described while referring to FIGS. 1 to 3.

[0011] FIG. 1 is a functional block diagram showing an example of the configuration of an inkjet printer 1.

[0012] As shown in FIG. 1, print data Img indicating an image to be formed by the inkjet printer 1 is supplied to the inkjet printer 1 from a host computer such as a personal computer or a digital camera. The inkjet printer 1 executes a printing process for forming the image indicated by the print data Img supplied from the host computer on the recording paper PP.

[0013] As shown in Figure 1, the inkjet printer 1 comprises a control unit 2 that controls various parts of the inkjet printer 1, a head unit 3 equipped with an ink ejection unit D, a drive signal generation unit 4 that generates a drive signal Com for driving the ejection unit D, a transport unit 7 for changing the relative position of the recording paper PP with respect to the head unit 3, and a determination unit 8 that determines the ink ejection state at the ejection unit D. Note that the inkjet printer 1 is an example of a "liquid ejection device", ink is an example of a "liquid", recording paper PP is an example of a "medium", the drive signal generation unit 4 is an example of a "generation unit", and the determination unit 8 is an example of a "determination unit".

[0014] In this embodiment, we assume that the inkjet printer 1 comprises one or more head units 3, one or more drive signal generation units 4 corresponding one-to-one with one or more head units 3, and one or more determination units 8 corresponding one-to-one with one or more head units 3. Specifically, in this embodiment, we assume that the inkjet printer 1 comprises four head units 3, four drive signal generation units 4 corresponding one-to-one with the four head units 3, and four determination units 8 corresponding one-to-one with the four head units 3. However, for the sake of explanation, in the following description, we will focus on one of the four head units 3, one drive signal generation unit 4 provided in correspondence with one of the four drive signal generation units 4, and one determination unit 8 provided in correspondence with one of the four drive signal generation units 4, as shown in Figure 1.

[0015] Control unit 2 is comprised of one or more CPUs. However, control unit 2 may include a programmable logic device such as an FPGA instead of, or in addition to, a CPU. Here, CPU is an abbreviation for Central Processing Unit, and FPGA is an abbreviation for field-programmable gate array. Control unit 2 also includes memory. The memory is comprised of one or both of volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM).

[0016] As will be explained in more detail later, the control unit 2 generates signals to control the operation of various parts of the inkjet printer 1, such as the print signal SI and the waveform specification signal dCom.

[0017] Here, the waveform specification signal dCom is a digital signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal used to drive the discharge unit D. In this embodiment, it is assumed that the drive signal Com includes drive signal Com-A and drive signal Com-B. In this embodiment, drive signal Com-A is an example of a "first drive signal," and drive signal Com-B is an example of a "second drive signal." Furthermore, in this embodiment, we assume that the waveform specification signal dCom includes a waveform specification signal dCom-A that defines the waveform of the drive signal Com-A, and a waveform specification signal dCom-B that defines the waveform of the drive signal Com-B. The drive signal generation unit 4 includes a DA conversion circuit and generates a drive signal Com having a waveform defined by a waveform specification signal dCom. Specifically, the drive signal generation unit 4 comprises a drive signal generation circuit 4A that generates a drive signal Com-A based on a waveform specification signal dCom-A, and a drive signal generation circuit 4B that generates a drive signal Com-B based on a waveform specification signal dCom-B.

[0018] In the following, drive signals Com-A and Com-B may be collectively referred to as drive signal Com-R. Also, in the following, drive signal generation circuits 4A and 4B may be collectively referred to as drive signal generation circuit 4R. That is, in this embodiment, the drive signal generation unit 4 comprises two drive signal generation circuits 4R: drive signal generation circuit 4A and drive signal generation circuit 4B. Also, in the following, waveform specification signals dCom-A and dCom-B may be collectively referred to as waveform specification signal dCom-R. Waveform specification signal dCom-R defines the waveform of drive signal Com-R. That is, the drive signal generation circuit 4R generates drive signal Com-R based on waveform specification signal dCom-R.

[0019] Furthermore, the print signal SI is a digital signal that specifies the type of operation of the ejector unit D. Specifically, the print signal SI specifies the type of operation of the ejector unit D by indicating whether or not to supply a drive signal Com to the ejector unit D.

[0020] As shown in Figure 1, the head unit 3 comprises a supply circuit 31, a recording head 32, and a detection circuit 33.

[0021] The recording head 32 is equipped with M ejection units D. Here, the value M is a natural number satisfying "M≧1". In the following, the m-th ejection unit D among the M ejection units D provided on the recording head 32 may be referred to as ejection unit D[m]. Here, the variable m is a natural number satisfying "1≦m≦M". Furthermore, in the following, if a component or signal of the inkjet printer 1 corresponds to ejection unit D[m] among the M ejection units D, the subscript [m] may be added to the code used to represent that component or signal.

[0022] The supply circuit 31 switches whether or not to supply the drive signal Com to the ejection unit D[m] based on the print signal SI. Note that the supply circuit 31 is an example of a "supply unit". Hereafter, the drive signal Com supplied to the ejection unit D[m] may be referred to as the supplied drive signal Vin[m]. Furthermore, the supply circuit 31 switches whether or not to supply the detection circuit 33 with a detection potential signal VX[m] indicating the potential of the upper electrode Zu[m] provided on the piezoelectric element PZ[m] of the ejection unit D[m], based on the printing signal SI.Hereafter, when the detection potential signal VX[m] is supplied from the ejection unit D[m] to the detection circuit 33, the ejection unit D[m] may be referred to as the ejection unit DH to be judged.The piezoelectric element PZ[m] and the upper electrode Zu[m] will be described later in Figure 3.

[0023] The detection circuit 33 generates a detection signal SK[m] based on the detection potential signal VX[m] supplied via the supply circuit 31 from the discharge unit D[m] designated as the discharge unit DH to be judged. Specifically, the detection circuit 33 generates the detection signal SK[m] by, for example, amplifying the detection potential signal VX[m] and removing noise components.

[0024] The determination unit 8 determines whether the ink ejection state at the ejection unit D is normal or not based on the detection signal SK[m]. In other words, the determination unit 8 determines whether or not there is an ejection abnormality at the ejection unit D based on the detection signal SK[m]. The determination unit 8 then generates determination information JH[m] indicating the result of the determination. Here, ejection abnormality is a general term for a state in which ink cannot be ejected normally from the nozzle opening N of the ejection unit D. For example, ejection abnormality includes a state in which ink cannot be ejected from the ejection unit D[m], a state in which the ejection unit D[m] ejects an amount of ink different from the amount of ink ejected defined by the drive signal Com, and a state in which the ejection unit D[m] ejects ink at a speed different from the ink ejection speed defined by the drive signal Com. Hereinafter, the process of determining the ejection state of the ejection unit D[m] based on the detection signal SK[m] will be referred to as the ejection state determination process.

[0025] Furthermore, in the following, the process of driving the discharge unit D[m] as the discharge unit DH to be judged, detecting the detected potential signal VX[m] from the discharge unit D[m], and generating the detected signal SK[m] based on the detected detected potential signal VX[m] will be referred to as the judgment target driving process.

[0026] When the determination target drive process is executed, the control unit 2 generates signals to control the head unit 3, such as the print signal SI. Also, when the determination target drive process is executed, the control unit 2 generates signals to control the drive signal generation unit 4, such as the waveform specification signal dCom. As a result, the control unit 2 drives the ejection unit D[m] as the determination target ejection unit DH during the determination target drive process. The detection circuit 33 then generates a detection signal SK[m] based on the detection potential signal VX[m] detected from the ejection unit D[m] driven as the determination target ejection unit DH during the determination target drive process.

[0027] As described above, the inkjet printer 1 performs the printing process. When the printing process is performed, the control unit 2 generates signals to control the head unit 3, such as the print signal SI, based on the print data Img. The control unit 2 also generates signals to control the drive signal generation unit 4, such as the waveform specification signal dCom, when the printing process is performed. The control unit 2 also generates signals to control the transport unit 7 when the printing process is performed. In this way, during the printing process, the control unit 2 controls the transport unit 7 to change the relative position of the recording paper PP with respect to the head unit 3, while adjusting the presence or absence of ink ejection from the ejection section D[m], the amount of ink ejection, and the timing of ink ejection, etc., and controls each part of the inkjet printer 1 so that an image corresponding to the print data Img is formed on the recording paper PP.

[0028] Figure 2 is a perspective view showing an example of the schematic internal structure of inkjet printer 1.

[0029] As shown in Figure 2, in this embodiment, it is assumed that the inkjet printer 1 is a serial printer. Specifically, when the inkjet printer 1 performs a printing process, it transports the recording paper PP in the X1 direction, and while reciprocating the head unit 3 in the Y1 direction which intersects the X1 direction and the Y2 direction which is the opposite direction of the Y1 direction, it ejects ink from the ejection unit D[m] to form dots Dt on the recording paper PP according to the print data Img.

[0030] In the following, the X1 direction and its opposite direction, the X2 direction, will be collectively referred to as the "X-axis direction," the Y1 direction intersecting the X-axis direction and its opposite direction, the Y2 direction, will be collectively referred to as the "Y-axis direction," and the Z1 direction intersecting the X-axis and Y-axis directions and its opposite direction, the Z2 direction, will be collectively referred to as the "Z-axis direction." In this embodiment, as an example, the case in which the X-axis direction, Y-axis direction, and Z-axis direction are mutually orthogonal will be described. However, the present invention is not limited to this embodiment. The X-axis direction, Y-axis direction, and Z-axis direction only need to intersect each other. In this embodiment, the Z1 direction is the direction in which ink is ejected from the ejection section D [m].

[0031] As shown in Figure 2, the inkjet printer 1 according to this embodiment comprises a housing 100 and a carriage 110 that is capable of reciprocating within the housing 100 in the Y-axis direction and is equipped with four head units 3.

[0032] In this embodiment, as shown in Figure 2, it is assumed that the carriage 110 houses four ink cartridges 120, each corresponding one-to-one with four inks: cyan, magenta, yellow, and black. Furthermore, as described above, this embodiment assumes that the inkjet printer 1 has four head units 3, each corresponding one-to-one with the four ink cartridges 120. Each ejection unit D[m] receives ink from the ink cartridge 120 corresponding to the head unit 3 on which the ejection unit D[m] is located. As a result, each ejection unit D[m] can fill itself with the supplied ink and eject the filled ink from the nozzle opening N. Note that the ink cartridges 120 may be located outside the carriage 110.

[0033] Furthermore, as described above, the inkjet printer 1 according to this embodiment includes a transport unit 7. As shown in Figure 2, the transport unit 7 comprises a carriage transport mechanism 71 for reciprocating the carriage 110 in the Y-axis direction, a carriage guide shaft 76 for supporting the carriage 110 so that it can reciprocate in the Y-axis direction, a media transport mechanism 73 for transporting the recording paper PP, and a platen 75 provided in the Z1 direction of the carriage 110. Therefore, when a printing process is performed, the transport unit 7 uses the carriage transport mechanism 71 to reciprocate the head unit 3 together with the carriage 110 along the carriage guide shaft 76 in the Y-axis direction, and the media transport mechanism 73 transports the recording paper PP on the platen 75 in the X1 direction, thereby changing the relative position of the recording paper PP with respect to the head unit 3 and enabling ink to land on the entire recording paper PP.

[0034] Figure 3 is a schematic partial cross-sectional view of the recording head 32, cut to include the ejection section D[m].

[0035] As shown in Figure 3, the ejection unit D[m] comprises a piezoelectric element PZ[m], a cavity CV filled with ink, a nozzle opening N communicating with the cavity CV, and a diaphragm 321. The ejection unit D[m] ejects ink from the cavity CV through the nozzle opening N when the piezoelectric element PZ[m] is driven by a supply drive signal Vin[m]. The cavity CV is a space partitioned by a cavity plate 324, a nozzle plate 323 with the nozzle opening N formed thereon, and a diaphragm 321. The cavity CV communicates with a reservoir 325 via an ink supply port 326. The reservoir 325 communicates with an ink cartridge 120 corresponding to the ejection unit D[m] via an ink intake port 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric body Zm[m] provided between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is electrically connected to a power supply line LD set to a predetermined potential VBS. When a supply drive signal Vin[m] is supplied to the upper electrode Zu[m] and a voltage is applied between the upper electrode Zu[m] and the lower electrode Zd[m], the piezoelectric element PZ[m] is displaced in the Z1 or Z2 direction according to the applied voltage, and as a result the piezoelectric element PZ[m] vibrates. The lower electrode Zd[m] is joined to the diaphragm 321. Therefore, when the piezoelectric element PZ[m] is driven by the supply drive signal Vin[m] and vibrates, the diaphragm 321 also vibrates. Then, the vibration of the diaphragm 321 changes the volume of the cavity CV and the pressure inside the cavity CV, causing the ink filled in the cavity CV to be ejected from the nozzle opening N.

[0036] <<2. Drive Signal Generation Unit>> As described above, the drive signal generation unit 4 comprises two drive signal generation circuits 4R: drive signal generation circuit 4A and drive signal generation circuit 4B. The outline of the drive signal generation circuit 4R within the drive signal generation unit 4 will be described below with reference to Figure 4.

[0037] Figure 4 shows an example of the circuit configuration of the drive signal generation circuit 4R.

[0038] As shown in Figure 4, the drive signal generation circuit 4R comprises an integrated circuit 40, an amplification circuit 41, a smoothing circuit 42, a pull-up circuit 43, and a filter circuit 44, and generates a drive signal Com-R based on a waveform specification signal dCom-R.

[0039] The integrated circuit 40 is, for example, an LSI, i.e., a Large Scale Integration, and generates gate signals SGH and SGL based on a waveform specification signal dCom-R. The integrated circuit 40 includes an analog conversion circuit 402, a subtractor 404, an adder 406, an attenuator 408, an integral attenuator 412, a comparator 420, and a gate driver 430.

[0040] The analog conversion circuit 402 is a DAC, or digital-to-analog converter, which converts the digital waveform specification signal dCom-R into an analog signal Aa. The voltage amplitude of signal Aa is, for example, about 0 to 2 volts, and the drive signal Com-R is obtained by amplifying this voltage by about 20 times. In other words, signal Aa is the signal before amplification of the drive signal Com-R. The integral attenuator 412 outputs a signal Ax obtained by attenuating the signal SN1 input to terminal Tn1 (described later) and then integrating it. The subtractor 404 outputs a signal Ab, which represents the potential obtained by subtracting the potential of signal Aa from the potential of signal Ax. The attenuator 408 outputs a signal Ay, which is the signal SN2 input to terminal Tn2 (described later) with its high-frequency components attenuated. The adder 406 outputs a signal As, which represents the potential obtained by adding the potentials of signal Ab and signal Ay.

[0041] Comparator 420 outputs a modulated signal Ms obtained by pulse-modulating signal As. Specifically, if signal As is rising, comparator 420 outputs a modulated signal Ms that becomes high level when it exceeds the threshold voltage Vth1, and if signal As is falling, it outputs a modulated signal Ms that becomes low level when it falls below the threshold voltage Vth2. The threshold voltages Vth1 and Vth2 are set to have the relationship 'Vth1 > Vth2'. The power supply voltage for the circuit from the analog conversion circuit 402 to the comparator 420 is a low voltage, such as 3.3 volts. In contrast, the drive signal Com-R has a large amplitude, sometimes exceeding 40 volts. Therefore, the integrating attenuator 412 attenuates the signal SN1, which has an amplitude corresponding to the drive signal Com-R, to match the amplitude range of the signal Ax to the amplitude range of the signal in the circuit from the analog conversion circuit 402 to the comparator 420. Furthermore, although a digital signal is used as an example in this embodiment for the waveform specification signal dCom-R, the waveform specification signal dCom-R can be any signal that defines the target value for generating the drive signal Com-R. For example, an analog signal Aa may be used as the waveform specification signal dCom-R. If signal Aa is the waveform specification signal dCom-R, the integrated circuit 40 may be configured without including the analog conversion circuit 402.

[0042] The gate driver 430 outputs a gate signal SGH, which is obtained by converting the modulated signal Ms to a specific amplitude, to terminal TnH. The gate driver 430 also outputs a gate signal SGL, which is obtained by converting the logic level of the modulated signal Ms inverted to a specific amplitude, to terminal TnL.

[0043] The amplification circuit 41 includes, for example, transistors TrH and TrL, and generates an amplified signal Az, which is a signal obtained by amplifying the modulated signal Ms, based on the gate signals SGH and SGL output from the integrated circuit 40. In this embodiment, as an example, it is assumed that transistors TrH and TrL are N-channel field-effect transistors, that is, Field Effect Transistors, or FETs.

[0044] The gate signal SGH output from the gate driver 430 is input to the gate electrode of transistor TrH via terminal TnH and resistor RGH. The gate signal SGL, output from the gate driver 430, is input to the gate electrode of transistor TrL via terminal TnL and resistor RGL. The logic levels of gate signals SGH and SGL are mutually exclusive.

[0045] Here, "mutually exclusive relationship" means that the signal level of the gate signal SGH supplied to the gate electrode of transistor TrH and the signal level of the gate signal SGL supplied to the gate electrode of transistor TrL can never be high at the same time; in other words, transistors TrH and TrL can never be turned on at the same time. Transistor TrH turns on when its gate electrode is high and turns off when its gate electrode is low. Similarly, transistor TrL turns on when its gate electrode is high and turns off when its gate electrode is low.

[0046] The drain electrode of transistor TrH is electrically connected to the feed line set to the high-potential power supply potential VHH, and the source electrode is electrically connected to node Nd. The source electrode of transistor TrL is electrically connected to the feed line set to the low-potential power supply potential VLL, and the drain electrode is electrically connected to node Nd. Note that potential VLL is lower than potential VHH. Potential VLL may be, for example, the ground potential, or it may be the same potential as potential VBS.

[0047] As described above, transistor TrH turns on when the gate signal SGH supplied to its gate electrode is high level and turns off when it is low level. Similarly, transistor TrL turns on when the gate signal SGL supplied to its gate electrode is high level and turns off when it is low level. Therefore, the node Nd, which electrically connects the source electrode of transistor TrH and the drain electrode of transistor TrL, outputs an amplified signal Az, which is the amplified modulated signal Ms.

[0048] The smoothing circuit 42 is an LPF, or Low Pass Filter, which smooths the amplified signal Az to generate the drive signal Com-R. The smoothing circuit 42 comprises an inductor L0 and a capacitor C0. One end of the inductor L0 is electrically connected to node Nd, and the other end is electrically connected to the output terminal Tn-out. One end of the capacitor C0 is electrically connected to the output terminal Tn-out, and the other end is electrically connected to a feed line set to potential VLL. The drive signal Com-R, which is the amplified signal Az smoothed, is output from the output terminal Tn-out.

[0049] The pull-up circuit 43 feeds back the signal SN1, which is the drive signal Com-R output to the output terminal Tn-out, to terminal Tn1. The pull-up circuit 43 includes a resistor R1, one end of which is electrically connected to the output terminal Tn-out and the other end of which is electrically connected to terminal Tn1, and a resistor R2, one end of which is electrically connected to terminal Tn1 and the other end of which is electrically connected to a power supply line set to a potential VHH.

[0050] The filter circuit 44 is a BPF, or Band Pass Filter, and feeds back a signal SN2, which is obtained by cutting the DC component from the frequency components of a predetermined band of the drive signal Com-R, to terminal Tn2. The filter circuit 44 comprises a resistor R3, a capacitor C1 with one end electrically connected to the output terminal Tn-out and the other end electrically connected to one end of resistor R3, a resistor R4 with one end electrically connected to one end of resistor R3 and the other end electrically connected to a power supply line set to potential VLL, a control unit 2 with one end electrically connected to the other end of resistor R3 and the other end electrically connected to a power supply line set to potential VLL, and a capacitor C3 with one end electrically connected to the other end of resistor R3 and the other end electrically connected to terminal Tn2.

[0051] Of these, capacitor C1 and resistor R4 function as an HPF, or High Pass Filter, which allows high-frequency components of the drive signal Com-R above the cutoff frequency to pass through. Resistor R3 and capacitor C2 function as an LPF, or Low Pass Filter, which allows low-frequency components of the drive signal Com-R below the cutoff frequency to pass through. In this embodiment, the cutoff frequency of the HPF in the filter circuit 44 is set lower than the cutoff frequency of the LPF. Therefore, the filter circuit 44 allows frequency components of the drive signal Com-R within a predetermined band that are above the cutoff frequency of the HPF and below the cutoff frequency of the LPF to pass through. Furthermore, because the filter circuit 44 is equipped with capacitor C3, the signal from which the DC component has been cut off from the predetermined band of frequency components of the drive signal Com-R that has passed through the HPF and LPF is fed back to terminal Tn2.

[0052] Thus, the drive signal generation circuit 4R generates the drive signal Com-R by smoothing the amplified signal Az at node Nd using the smoothing circuit 42. The drive signal Com-R is integrated and subtracted by the integrating attenuator 412 and then fed back to the subtractor 404. Therefore, it self-oscillates at a frequency determined by the delay in the smoothing circuit 42, the delay in the integrating attenuator 412, and the feedback transfer function. However, because the delay amount of the feedback path via terminal Tn1 is large, the self-oscillation frequency cannot be increased to a level that sufficiently ensures the accuracy of the waveform of the drive signal Com-R using only feedback via terminal Tn1. In contrast, in this embodiment, a separate path is provided via terminal Tn2 to feed back the high-frequency components of the drive signal Com-R, in addition to the path via terminal Tn1, so that the overall feedback delay of the drive signal generation circuit 4R can be reduced. In other words, in this embodiment, the frequency of signal As, obtained by adding signal Ay, which is the high-frequency component of the drive signal Com-R, to signal Ab, can be made higher compared to the case where there is no path via terminal Tn2, thus ensuring sufficient accuracy of the drive signal Com-R.

[0053] <<3. Overview of the Head Unit>> The following describes the overview of the head unit 3 with reference to Figures 5 through 8.

[0054] Figure 5 is a block diagram showing an example of the configuration of the head unit 3.

[0055] As shown in Figure 5, the head unit 3 comprises a supply circuit 31, a recording head 32, and a detection circuit 33. The head unit 3 also includes wiring LA, which receives the drive signal Com-A from the drive signal generation circuit 4A provided in the drive signal generation unit 4; wiring LB, which receives the drive signal Com-B from the drive signal generation circuit 4B provided in the drive signal generation unit 4; and wiring LS, which supplies the detection potential signal VX[m] to the detection circuit 33.

[0056] As shown in Figure 5, the supply circuit 31 comprises M switches Wa[1] to Wa[M] that correspond one-to-one with M discharge units D[1] to D[M], M switches Wb[1] to Wb[M] that correspond one-to-one with M discharge units D[1] to D[M], M switches Ws[1] to Ws[M] that correspond one-to-one with M discharge units D[1] to D[M], and a connection state specification circuit 310 that specifies the connection state of each switch.

[0057] The connection status specification circuit 310 generates a connection status specification signal Qa[m] that specifies whether switch Wa[m] is on or off, a connection status specification signal Qb[m] that specifies whether switch Wb[m] is on or off, and a connection status specification signal Qs[m] that specifies whether switch Ws[m] is on or off, based on the print signal SI, latch signal LAT, change signal CH, and period specification signal Tsig supplied from the control unit 2.

[0058] Switch Wa[m] switches between conductivity and non-conductivity between wiring LA and the upper electrode Zu[m] of piezoelectric element PZ[m] based on connection status specification signal Qa[m]. In this embodiment, switch Wa[m] is turned on when connection status specification signal Qa[m] is high level and turned off when it is low level. When switch Wa[m] is turned on, the drive signal Com-A supplied to wiring LA is supplied as a supply drive signal Vin[m] to the upper electrode Zu[m] of discharge section D[m].

[0059] The switch Wb[m] switches between conductivity and non-conductivity between the wiring LB and the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection status specification signal Qb[m]. In this embodiment, the switch Wb[m] is turned on when the connection status specification signal Qb[m] is high level and turned off when it is low level. When the switch Wb[m] is turned on, the drive signal Com-B supplied to the wiring LB is supplied as the supply drive signal Vin[m] to the upper electrode Zu[m] of the discharge section D[m].

[0060] The switch Ws[m] switches between conduction and non-conductivity between the wiring LS and the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designation signal Qs[m]. In this embodiment, the switch Ws[m] is turned on when the connection state designation signal Qs[m] is at a high level and turned off when it is at a low level. When the switch Ws[m] is turned on, the potential of the upper electrode Zu[m] provided in the discharge section D[m] is supplied to the detection circuit 33 via the wiring LS as the detection potential signal VX[m].

[0061] In this embodiment, the detection circuit 33 generates a detection signal SK[m] having a waveform corresponding to the waveform of the detection potential signal VX[m] supplied from the wiring LS. Specifically, the detection circuit 33 generates a signal that is an amplified version of the detection potential signal VX[m], from which noise components have been removed, and outputs the generated signal as the detection signal SK[m].

[0062] When the inkjet printer 1 performs a printing process or a judgment target driving process, one or more unit periods TP are set as the operating period of the inkjet printer 1. In each unit period TP, the inkjet printer 1 can drive each ejection unit D[m] for the printing process or the judgment target driving process.

[0063] Figure 6 is a timing chart showing various signals, such as the drive signal Com, supplied to the head unit 3 during a unit period TP. Figure 7 is a timing chart showing the drive signal Com-B during a unit period TP.

[0064] As shown in Figure 6, the control unit 2 outputs a latch signal LAT which has a pulse PLL. This allows the control unit 2 to define a unit period TP as the period from the rising edge of one pulse PLL to the rising edge of the next pulse PLL. Furthermore, the control unit 2 outputs a change signal CH having a pulse PLC during a unit period TP. The control unit 2 then divides the unit period TP into a drive period TQ1 from the rising edge of the pulse PLL to the rising edge of the pulse PLC, and a drive period TQ2 from the rising edge of the pulse PLC to the rising edge of the pulse PLL.

[0065] Furthermore, the control unit 2 outputs a period specification signal Tsig having pulses PLT1 and PLT2 during a unit period TP. The control unit 2 then divides the unit period TP into three control periods: TSS1, from the rising edge of the pulse PLL to the rising edge of pulse PLT1; TSS2, from the rising edge of pulse PLT1 to the rising edge of pulse PLT2; and TSS3, from the rising edge of pulse PLT2 to the rising edge of the pulse PLL.

[0066] As shown in Figure 6, the print signal SI includes M individual designation signals Sd[1] to Sd[M] that correspond one-to-one with M ejection units D[1] to D[M]. The individual designation signals Sd[m] specify the mode of operation of the ejection units D[m] in each unit period TP when the inkjet printer 1 performs a print process or a determination target drive process. Prior to each unit period TP, the control unit 2 supplies the print signal SI, which includes the M individual designation signals Sd[1] to Sd[M], to the connection state designation circuit 310 in synchronization with the clock signal CL. The connection state designation circuit 310 then generates connection state designation signals Qa[m], Qb[m], and Qs[m] in the unit period TP based on the individual designation signals Sd[m].

[0067] In this embodiment, when the inkjet printer 1 performs a printing process, it is assumed that the ejection unit D[m] is capable of forming any of the following dots Dt: a large dot made of ink with an ink amount ξ1, a medium dot made of ink with an ink amount ξ2 less than ξ1, and a small dot made of ink with an ink amount ξ3 less than ξ2. Also, in this embodiment, when the inkjet printer 1 performs a determination target drive process, it is assumed that the ejection unit D[m] designated as the determination target ejection unit DH ejects ink with an ink amount ξ0 which is greater than the ink amount ξ1.

[0068] Figure 8 is an explanatory diagram illustrating the individual designation signal Sd[m].

[0069] As shown in Figure 8, in this embodiment, the individual designation signal Sd[m] can take any one of five values ​​during a unit period TP in which printing or determination target driving processing is performed: "1" which designates the ejection unit D[m] as the large dot forming ejection unit DP-1, "2" which designates the ejection unit D[m] as the medium dot forming ejection unit DP-2, "3" which designates the ejection unit D[m] as the small dot forming ejection unit DP-3, "4" which designates the ejection unit D[m] as the non-dot forming ejection unit DP-4, and "5" which designates the ejection unit D[m] as the determination target ejection unit DH. Here, the large dot forming ejection unit DP-1 is the ejection unit D that forms large dots during the unit period TP. The medium dot forming ejection unit DP-2 is the ejection unit D that forms medium dots during the unit period TP. The small dot forming ejection unit DP-3 is the ejection unit D that forms small dots during the unit period TP. Furthermore, the dot-free dispensing section DP-4 is a dispensing section D that does not form dots during a unit period TP.

[0070] Return to the explanation in Figures 6 and 7. As shown in Figure 6, in this embodiment, the drive signal Com-A has a waveform PA1 provided during the drive period TQ1 and a waveform PA2 provided during the drive period TQ2. Of these, waveform PA1 is a waveform that returns to the reference potential V0, passing through a potential VLA1 which is lower than the reference potential V0, and a potential VHA1 which is higher than the reference potential V0. When a supply drive signal Vin[m] having waveform PA1 is supplied to the ejection unit D[m], the waveform PA1 is determined so that ink equivalent to the ink amount φ1 is ejected from the ejection unit D[m]. Furthermore, waveform PA2 is a waveform that returns to reference potential V0, passing through a potential VLA2 which is lower than reference potential V0, and a potential VHA2 which is higher than reference potential V0. When a supply drive signal Vin[m] having waveform PA2 is supplied to the ejection unit D[m], the waveform PA2 is determined so that ink equivalent to the ink amount φ2 is ejected from the ejection unit D[m].

[0071] In this embodiment, it is assumed that ink quantity ξ1 corresponds to the sum of ink quantity φ1 and ink quantity φ2, ink quantity ξ2 corresponds to ink quantity φ1, and ink quantity ξ3 corresponds to ink quantity φ2.

[0072] Furthermore, in this embodiment, as an example, we assume a case where potential VHA1 is higher than potential VHA2, and potential VLA1 is lower than potential VLA2.

[0073] Furthermore, in this embodiment, as an example, we assume that when the potential of the supply drive signal Vin[m] supplied to the ejection unit D[m] is high, the volume of the cavity CV provided by the ejection unit D[m] becomes smaller compared to when the potential is low. Therefore, when the ejection unit D[m] is driven by a supply drive signal Vin[m] having a waveform PA1 or the like, the ink in the ejection unit D[m] is ejected from the nozzle opening N as the potential of the supply drive signal Vin[m] changes from low to high.

[0074] As shown in Figures 6 and 7, in this embodiment, the drive signal Com-B has a waveform PS provided for a unit period TP. Here, the waveform PS is a waveform in which, during the control period TSS1, the potential changes from the reference potential V0 to a potential V1 that is higher than the reference potential V0, then to a potential V2 that is lower than the reference potential V0, and finally to a potential V3 that is higher than the reference potential V0. During the control period TSS2, the potential V3 is maintained, and during the control period TSS3, the potential changes from V3 to the reference potential V0.

[0075] In this embodiment, we assume that potential V1 is approximately the same as potential VCH, potential V2 is approximately the same as potential VCL, and potential V3 is approximately the same as potential VCH. That is, in this embodiment, as an example, we assume that potential V1 and potential V3 are approximately the same. Here, "approximately the same" is a concept that includes not only cases where they are completely identical, but also cases where they can be considered identical when errors are taken into account. For example, "approximately the same" may mean that they are identical in terms of design. In this specification, for example, if there is an error of 5 percent or less between two elements, those two elements will be considered identical and will be considered approximately the same. Furthermore, potential VCH is the highest potential that the drive signal generation circuit 4R can supply to the upper electrode Zu[m] as a drive signal Com-R, and potential VCL is the lowest potential that the drive signal generation circuit 4R can supply to the upper electrode Zu[m] as a drive signal Com-R. For example, potential VCH may be approximately the same potential as potential VHH, and potential VCL may be approximately the same potential as potential VLL. Also, for example, potential VCH may be the potential obtained by subtracting from potential VHH the voltage drop caused by transistor TrH and the voltage drop caused by transistors constituting switch Wa[m] or switch Wb[m], etc. Specifically, potential VCH may be the potential obtained by subtracting from potential VHH the voltage caused by the on-resistance of transistor TrH and the voltage applied between the gate and source of a transistor constituting switch Wa[m] or switch Wb[m], etc., in order to maintain the on-state of the transistor. Furthermore, for example, potential VCL may be the potential obtained by adding the voltage drop due to transistor TrL and the voltage drop due to the transistor constituting switch Wa[m] or switch Wb[m], etc., to potential VLL. Also, for example, potential VCL may be the potential obtained by adding the voltage due to the on-resistance of transistor TrL and the voltage applied between the gate and source of the transistor constituting switch Wa[m] or switch Wb[m], etc., in order to maintain the on-state of the said transistor, to potential VLL. Here, potential VCH is an example of a "first potential", and potential VCL is an example of a "second potential".

[0076] Furthermore, in the following, the portion of waveform PS that changes from potential V1 to potential V2 will be referred to as partial waveform PS1, and the portion of waveform PS that changes from potential V2 to potential V3 will be referred to as partial waveform PS2. Furthermore, in the following, the potential difference between potentials V1 and V2 will be referred to as potential difference VD1, and the potential difference between potentials V3 and V2 will be referred to as potential difference VD2. Furthermore, in the following, the potential difference between potentials VCH and VCL will be referred to as potential difference VDH. In the waveform PS according to this embodiment, potential differences VD1 and VD2 are set to approximately the same potential difference as potential difference VDH.

[0077] Furthermore, in the following, the portion of the drive signal Com-B corresponding to the partial waveform PS1 will be referred to as partial signal Com-PS1, and the portion of the drive signal Com-B corresponding to the partial waveform PS2 will be referred to as partial signal Com-PS2. That is, in this embodiment, the drive signal Com-B includes partial signal Com-PS1 having partial waveform PS1 and partial signal Com-PS2 having partial waveform PS2. Here, partial signal Com-PS1 is an example of a "first partial signal," and partial signal Com-PS2 is an example of a "second partial signal."

[0078] Furthermore, in the following, within the control period TSS1, the period during which the potential of the drive signal Com-B is maintained at potential V1 will be referred to as period Tv1, within the control period TSS1, the period during which a partial waveform PS1 is provided and the potential of the drive signal Com-B changes from potential V1 to potential V2 will be referred to as period Td1, within the control period TSS1, the period during which the potential of the drive signal Com-B is maintained at potential V2 will be referred to as period Tv2, and within the control period TSS1, the period during which a partial waveform PS2 is provided and the potential of the drive signal Com-B changes from potential V2 to potential V3 will be referred to as period Td2. Furthermore, in the following, within the unit period TP, the period during which the potential of the drive signal Com-B is maintained at potential V3 will be referred to as period Tv3.

[0079] In this embodiment, as described above, we assume that in the drive signal Com-A, the potential VHA1 is higher than the potential VHA2, and the potential VLA1 is lower than the potential VLA2. In other words, in this embodiment, as an example, we assume that the drive signal Com-A changes its potential within the range from potential VLA1 to potential VHA1. Here, potential VLA1 is an example of a "third potential," and potential VHA1 is an example of a "fourth potential." Furthermore, in this embodiment, it is assumed that potential VCH is higher than potentials VHA1 and VHA2 of drive signal Com-A, and potential VLL is lower than potentials VLA1 and VLA2 of drive signal Com-A. In other words, in this embodiment, potential VCH is not included in the range from potential VLA1 to potential VHA1 of drive signal Com-A, and potential VLL is also not included in the range from potential VLA1 to potential VHA1 of drive signal Com-A. To put it another way, in this embodiment, the highest potential of drive signal Com-A is lower than potential VCH, which is the highest potential of drive signal Com-B, and the lowest potential of drive signal Com-A is higher than potential VCL, which is the lowest potential of drive signal Com-B. That is, in this embodiment, the range of change in the potential of drive signal Com-A is included in the range of change in the potential of drive signal Com-B.

[0080] Next, referring to Figure 8, the operation of the discharge unit D[m] specified by the individual designation signal Sd[m] will be explained.

[0081] As shown in Figure 8, when the individual designation signal Sd[m] indicates a value of "1" which designates the ejection unit D[m] as the large dot forming ejection unit DP-1 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a high level during the drive period TQ1 and the drive period TQ2. In this case, the switch Wa[m] is turned on during the drive period TQ1 and the drive period TQ2. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] which has waveforms PA1 and PA2, and ejects ink with an ink amount ξ1 corresponding to a large dot.

[0082] Furthermore, if the individual designation signal Sd[m] indicates a value of "2" which designates the ejection unit D[m] as the medium dot forming ejection unit DP-2 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a high level during the drive period TQ1. In this case, the switch Wa[m] is turned on during the drive period TQ1. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] having waveform PA1 and ejects ink with an ink amount ξ2 corresponding to the medium dot.

[0083] Furthermore, if the individual designation signal Sd[m] indicates a value of "3" which designates the ejection unit D[m] as the small dot forming ejection unit DP-3 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qa[m] to a high level during the drive period TQ2. In this case, the switch Wa[m] is turned on during the drive period TQ2. Therefore, during the unit period TP, the ejection unit D[m] is driven by the supply drive signal Vin[m] having waveform PA2 and ejects ink with an ink amount ξ3 corresponding to a small dot.

[0084] Furthermore, if the individual designation signal Sd[m] indicates a value of "4" which designates the ejection unit D[m] as the dot-non-forming ejection unit DP-4 during the unit period TP, the connection status designation circuit 310 sets the connection status designation signals Qa[m], Qb[m], and Qs[m] to a low level for the unit period TP. In this case, switches Wa[m], Wb[m], and Ws[m] are turned off for the unit period TP. Therefore, the ejection unit D[m] is not driven by the supply drive signal Vin[m] during the unit period TP and does not eject ink.

[0085] Furthermore, if the individual designation signal Sd[m] indicates a value of "5" which designates the discharge unit D[m] as the discharge unit DH to be determined during the unit period TP, the connection status designation circuit 310 sets the connection status designation signal Qb[m] to a high level during control periods TSS1 and TSS3, and sets the connection status designation signal Qs[m] to a high level during control period TSS2. In this case, the switch Wb[m] is turned on during control periods TSS1 and TSS3, and the switch Ws[m] is turned on during control period TSS2. As a result, the vibrations generated in the discharge unit D[m], which was designated as the discharge unit DH to be determined, during control period TSS1 as a result of being driven by the supply drive signal Vin[m] having partial waveforms PS1 and PS2, persist during control period TSS2. During the control period TSS2, if vibration remains in the discharge section D[m], the potential of the upper electrode Zu[m] provided in the discharge section D[m] changes. The detection circuit 33 then detects the change in the potential of the upper electrode Zu[m] corresponding to the vibration remaining in the discharge section D[m] as a detected potential signal VX[m] via the switch Ws[m] during the control period TSS2. In other words, the waveform of the detection potential signal VX[m] detected from the discharge section D[m] during the control period TSS2 represents the waveform of the vibrations remaining in the discharge section D[m] during the control period TSS2. Furthermore, the waveform of the detection signal SK[m] generated based on the detection potential signal VX[m] detected from the discharge section D[m] during the control period TSS2 represents the waveform of the vibrations remaining in the discharge section D[m] during the control period TSS2.

[0086] <<4. Verification Example>> Next, the drive signals Com-Bw and Com-Bz according to the verification example will be described while referring to FIGS. 9 and 16.

[0087] FIG. 9 is a timing chart for explaining the drive signal Com-Bw according to Verification Example 1.

[0088] As shown in FIG. 9, the drive signal Com-Bw has a waveform PS-W provided in a unit period TP. Here, the waveform PS-W changes from the reference potential V0 to a potential V1w higher than the reference potential V0, a potential V2 lower than the reference potential V0, and then to a potential V3w higher than the reference potential V0 during the control period TSS1, maintains the potential V3w during the control period TSS2, and changes from the potential V3w to the reference potential V0 during the control period TSS3.

[0089] In Verification Example 1, it is assumed that the potential V1w satisfies "V0 ≤ V1w < VCH". Specifically, in Verification Example 1, when the potential V1w is closer to the reference potential V0 than the potential VCH, in other words, when the potential V1w satisfies "(V1w - V0) < (VCH - V1w)". Also, in Verification Example 1, it is assumed that the potential V3w satisfies "V1w ≤ V3w ≤ VCH".

[0090] In Verification Example 1, the portion of the waveform PS-W that changes from the potential V1w to the potential V2 is referred to as a partial waveform PS1w, and the portion of the waveform PS-W that changes from the potential V2 to the potential V3w is referred to as a partial waveform PS2w. Also, hereinafter, the potential difference between the potential V1w and the potential V2 is referred to as a potential difference VD1w, and the potential difference between the potential V3w and the potential V2 is referred to as a potential difference VD2w. Also, hereinafter, the potential difference between the reference potential V0 and the potential VCL is referred to as a potential difference VDL.

[0091] Furthermore, in Verification Example 1, the portion of the drive signal Com-Bw corresponding to the partial waveform PS1w is referred to as partial signal Com-PS1w, and the portion of the drive signal Com-Bw corresponding to the partial waveform PS2w is referred to as partial signal Com-PS2w. In other words, in Verification Example 1, the drive signal Com-Bw includes partial signal Com-PS1w having partial waveform PS1w and partial signal Com-PS2w having partial waveform PS2w.

[0092] In Verification Example 1, during the control period TSS1, the potential of the drive signal Com-Bw is maintained at potential V1w during period Tv1, a partial waveform PS1w is provided during the control period TSS1, where the potential of the drive signal Com-Bw changes from potential V1w to potential V2 during period Td1, the potential of the drive signal Com-Bw is maintained at potential V2 during period Tv2, a partial waveform PS2w is provided during the control period TSS1, where the potential of the drive signal Com-Bw changes from potential V2 to potential V3w during period Td2, and the potential of the drive signal Com-Bw is maintained at potential V3w during period Tv3 of the unit period TP.

[0093] Figure 10 is a timing chart illustrating the drive signal Com-Bz related to Verification Example 2.

[0094] As shown in Figure 10, the drive signal Com-Bz has a waveform PS-Z provided for a unit period TP. Here, the waveform PS-Z is a waveform that, during the control period TSS1, changes from the reference potential V0, through a potential V1z higher than the reference potential V0, and then a potential V2 lower than the reference potential V0, to a potential V3 higher than the reference potential V0. During the control period TSS2, the potential V3 is maintained, and during the control period TSS3, the potential changes from V3 to the reference potential V0. In Verification Example 2, it is assumed that the potential V1z satisfies the condition "V0 ≤ V1z ≤ VCH".

[0095] Furthermore, in Verification Example 2, the portion of the waveform PS-Z that changes from potential V1z to potential V2 is referred to as partial waveform PS1z, and the portion of the waveform PS-Z that changes from potential V2 to potential V3 is referred to as partial waveform PS2, as in the embodiment. In addition, below, the potential difference between potentials V1w and V2 is referred to as potential difference VD1z.

[0096] Furthermore, in Verification Example 2, the portion of the drive signal Com-Bz corresponding to the partial waveform PS1z is referred to as the partial signal Com-PS1z. That is, in Verification Example 2, the drive signal Com-Bz includes the partial signal Com-PS1z having the partial waveform PS1z, and the partial signal Com-PS2 having the partial waveform PS2.

[0097] In Verification Example 2, during the control period TSS1, the potential of the drive signal Com-Bz is maintained at potential V1z during period Tv1, a partial waveform PS1z is provided during the control period TSS1, where the potential of the drive signal Com-Bz changes from potential V1z to potential V2 during period Td1, the potential of the drive signal Com-Bz is maintained at potential V2 during period Tv2, a partial waveform PS2 is provided during the control period TSS1, where the potential of the drive signal Com-Bz changes from potential V2 to potential V3 during period Td2, and the potential of the drive signal Com-Bz is maintained at potential V3 during period Tv3 of the unit period TP.

[0098] Next, we will explain the discharge abnormalities assumed in the verification example.

[0099] Figure 11 is a diagram illustrating the first type of discharge abnormality assumed in the verification example. Figure 12 is a diagram illustrating the second type of discharge abnormality assumed in the verification example.

[0100] Here, the discharge abnormality in the first embodiment is a discharge abnormality caused by the adhesion and accumulation of foreign matter GP, such as paper dust or thickened ink, on the inner wall NH of the nozzle opening N of the discharge section D[m], as shown in Figure 11. If a first type of ejection abnormality occurs in the ejection unit D[m], the foreign matter GP adhering to the inner wall NH of the nozzle opening N causes the ink droplets ejected from the nozzle opening N of the ejection unit D[m] to fly on a different trajectory than when the ejection state is normal. Therefore, if a first type of ejection abnormality occurs in the ejection unit D[m], the ink droplets ejected from the ejection unit D[m] during the printing process will land on the recording paper PP at a position different from the desired position. Furthermore, if a discharge abnormality of the first type occurs in the discharge section D[m], the flow resistance of the inner wall NH of the nozzle opening N increases compared to when the ink discharge state in the discharge section D[m] is normal. As a result, the position of the liquid level at which the ink droplets discharged from the nozzle opening N separate from the ink in the cavity CV of the discharge section D[m] changes in the Z2 direction, and the period of vibration occurring in the discharge section D[m] becomes shorter.

[0101] Furthermore, the second type of discharge abnormality, as shown in Figure 12, is a discharge abnormality caused by the adhesion and accumulation of foreign matter GT, such as paper dust or thickened ink, on the inner wall NH of the nozzle opening N of the discharge section D[m]. Here, foreign matter GT is foreign matter that has accumulated on the inner wall NH, similar to foreign matter GP, but is smaller than foreign matter GP. When a second type of ejection abnormality occurs in the ejection unit D[m], the foreign matter GT adhering to the inner wall NH of the nozzle opening N causes the ink droplets ejected from the nozzle opening N of the ejection unit D[m] to fly on a different trajectory than when the ejection state is normal. Therefore, when a second type of ejection abnormality occurs in the ejection unit D[m], the ink droplets ejected from the ejection unit D[m] during the printing process land on the recording paper PP at a location different from the desired location. Note that the magnitude of the displacement of the landing position when a second type of ejection abnormality occurs is smaller than the displacement of the landing position when a first type of ejection abnormality occurs. Furthermore, when the second type of ejection abnormality occurs in the ejection section D[m], the flow resistance of the inner wall NH of the nozzle opening N increases compared to when the ink ejection state in the ejection section D[m] is normal. As a result, the position of the liquid level at which the ink droplet ejected from the nozzle opening N separates from the ink in the cavity CV of the ejection section D[m] changes in the Z2 direction, and the period of vibration occurring in the ejection section D[m] becomes shorter. As mentioned above, foreign matter GP is larger than foreign matter GT. Therefore, the period of vibration occurring in the ejection section D[m] when the first type of ejection abnormality occurs is shorter than the period of vibration occurring in the ejection section D[m] when the second type of ejection abnormality occurs.

[0102] Next, we will explain the detection of discharge abnormalities in the verification example.

[0103] Figure 13 shows the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] when the drive signal Com-Bw related to Verification Example 1 is supplied to the discharge unit D[m] which is driven as the discharge unit DH to be judged. In Figure 13, the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] driven by the drive signal Com-Bw is plotted while the potential difference VD2w is changed from the potential difference VDL to the potential difference VDH by varying the potential V3w of the drive signal Com-Bw in the range from the reference potential V0 to the potential VCH. Specifically, in the graph shown in Figure 13, the horizontal axis shows the potential difference VD2w of the drive signal Com-Bw, and the vertical axis shows the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] driven by the drive signal Com-Bw.

[0104] Furthermore, in Figure 13, the relationship line LW0 is a line that shows the relationship between the potential difference VD2w of the drive signal Com-Bw supplied to the ejection unit D[m] and the period TC of the detected potential signal VX[m] when the ink ejection state at the ejection unit D[m] is normal. The relationship line LW1 is a line that shows the relationship between the potential difference VD2w of the drive signal Com-Bw supplied to the ejection unit D[m] and the period TC of the detected potential signal VX[m] when the ejection abnormality of the first type occurs at the ejection unit D[m]. Furthermore, the difference value dTW1 is the difference between the period TC indicated by the detection potential signal VX[m] detected from the ejection unit D[m] driven by the drive signal Com-Bw when a first type of ejection abnormality occurs in the ejection unit D[m], and the period TC indicated by the detection potential signal VX[m] detected from the ejection unit D[m] driven by the drive signal Com-Bw when the ink ejection state in the ejection unit D[m] is normal.

[0105] As shown in Figure 13, in Verification Example 1, when a first type of ejection abnormality occurs at the ejection unit D[m], the change in the period TC indicated by the detected potential signal VX[m] when the potential difference VD2w is changed is greater than the change in the period TC indicated by the detected potential signal VX[m] when the ink ejection state at the ejection unit D[m] is normal and the potential difference VD2w is changed. Also, in Verification Example 1, when the potential difference VD2w approaches the potential difference VDH, the difference value dTW1 becomes larger compared to when the potential difference VD2 is close to the potential difference VDL. Therefore, in order to accurately detect the first type of ejection abnormality using the drive signal Com-Bw related to Verification Example 1, the potential difference VD2w should be set to a value close to the potential difference VDH.

[0106] Figure 14 shows the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] when the drive signal Com-Bw related to Verification Example 1 is supplied to the discharge unit D[m] which is driven as the discharge unit DH to be judged. In Figure 14, as with Figure 13, the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] driven by the drive signal Com-Bw related to Verification Example 1 is plotted while the potential difference VD2w is varied within the range of potential difference VDL to potential difference VDH.

[0107] Furthermore, in Figure 14, the relationship line LW2 is a line that shows the relationship between the potential difference VD2w of the drive signal Com-Bw supplied to the ejection unit D[m] and the period TC of the detected potential signal VX[m] when a second type of ejection abnormality occurs in the ejection unit D[m]. The difference value dTW2 is the difference between the period TC indicated by the detected potential signal VX[m] detected from the ejection unit D[m] driven by the drive signal Com-Bw when a second type of ejection abnormality occurs in the ejection unit D[m], and the period TC indicated by the detected potential signal VX[m] detected from the ejection unit D[m] driven by the drive signal Com-Bw when the ink ejection state in the ejection unit D[m] is normal.

[0108] As shown in Figure 14, in Verification Example 1, when the second type of ejection abnormality occurs at the ejection unit D[m] and the potential difference VD2w is changed, the change in the period TC indicated by the detected potential signal VX[m] when the potential difference VD2w is changed is approximately the same as when the ink ejection state at the ejection unit D[m] is normal and the potential difference VD2w is changed. Specifically, in Verification Example 1, the difference value dTW2 when the potential difference VD2w approaches the potential difference VDH is approximately the same as the difference value dTW2 when the potential difference VD2 is close to the potential difference VDL. Therefore, even if the potential difference VD2w is set to a value close to the potential difference VDH, it is difficult to accurately detect the second type of ejection abnormality using the drive signal Com-Bw related to Verification Example 1.

[0109] Figure 15 shows the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] when the drive signal Com-Bz related to Verification Example 2 is supplied to the discharge unit D[m] which is driven as the discharge unit DH to be judged. In Figure 15, the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] driven by the drive signal Com-Bz is plotted while the potential V1z of the drive signal Com-Bz related to Verification Example 2 is varied from the reference potential V0 to the potential VCH, thereby varying the potential difference VD1z from the potential difference VDL to the potential difference VDH. Specifically, in the graph shown in Figure 15, the horizontal axis represents the potential difference VD1z of the drive signal Com-Bz, and the vertical axis represents the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] driven by the drive signal Com-Bz.

[0110] Furthermore, in Figure 15, the relationship line LZ0 is a line that shows the relationship between the potential difference VD1z of the drive signal Com-Bz supplied to the ejection unit D[m] and the period TC of the detected potential signal VX[m] when the ink ejection state at the ejection unit D[m] is normal. The relationship line LZ1 is a line that shows the relationship between the potential difference VD1z of the drive signal Com-Bz supplied to the ejection unit D[m] and the period TC of the detected potential signal VX[m] when the ejection abnormality of the first type occurs at the ejection unit D[m]. Furthermore, the difference value dTZ1 is the difference between the period TC indicated by the detection potential signal VX[m] detected from the ejection unit D[m] driven by the drive signal Com-Bz when a first type of ejection abnormality occurs in the ejection unit D[m], and the period TC indicated by the detection potential signal VX[m] detected from the ejection unit D[m] driven by the drive signal Com-Bz when the ink ejection state in the ejection unit D[m] is normal.

[0111] As shown in Figure 15, in Verification Example 2, when a first type of ejection abnormality occurs at the ejection unit D[m], the change in the period TC indicated by the detected potential signal VX[m] when the potential difference VD1z is changed is approximately the same as the change in the period TC indicated by the detected potential signal VX[m] when the ink ejection state at the ejection unit D[m] is normal and the potential difference VD1z is changed. However, in Verification Example 2, when the potential difference VD1z approaches the potential difference VDH, the difference value dTZ1 becomes larger compared to when the potential difference VD2 is close to the potential difference VDL. Therefore, in order to accurately detect the first type of ejection abnormality using the drive signal Com-Bz related to Verification Example 2, it is preferable to set the potential difference VD1z to a value close to the potential difference VDH. Note that in Verification Example 2, the difference value dTZ1 is a large value regardless of the potential difference VD1z. Therefore, by using the drive signal Com-Bz according to Verification Example 2, it is possible to detect the discharge abnormality of the first type regardless of the potential difference VD1z.

[0112] Figure 16 shows the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] when the drive signal Com-Bz related to Verification Example 2 is supplied to the discharge unit D[m] which is driven as the discharge unit DH to be judged. In Figure 16, as with Figure 15, the period TC of the detected potential signal VX[m] detected from the discharge unit D[m] driven by the drive signal Com-Bz related to Verification Example 2 is plotted while the potential difference VD1z is varied within the range of potential difference VDL to potential difference VDH.

[0113] Furthermore, in Figure 16, the relationship line LZ2 is a line that shows the relationship between the potential difference VD1z of the drive signal Com-Bz supplied to the ejection unit D[m] and the period TC of the detected potential signal VX[m] when a second type of ejection abnormality occurs in the ejection unit D[m]. The difference value dTZ2 is the difference between the period TC indicated by the detected potential signal VX[m] detected from the ejection unit D[m] driven by the drive signal Com-Bz when a second type of ejection abnormality occurs in the ejection unit D[m], and the period TC indicated by the detected potential signal VX[m] detected from the ejection unit D[m] driven by the drive signal Com-Bz when the ink ejection state in the ejection unit D[m] is normal.

[0114] As shown in Figure 16, in Verification Example 2, when the second type of ejection abnormality occurs at the ejection unit D[m], the change in the period TC indicated by the detected potential signal VX[m] when the potential difference VD1z is changed is greater than the change in the period TC indicated by the detected potential signal VX[m] when the ink ejection state at the ejection unit D[m] is normal and the potential difference VD1z is changed. Specifically, in Verification Example 2, the difference value dTZ1 when the potential difference VD1z approaches the potential difference VDH is greater than the difference value dTZ1 when the potential difference VD1z is close to the potential difference VDL. Therefore, in order to accurately detect the second type of ejection abnormality using the drive signal Com-Bz related to Verification Example 2, the potential difference VD1z should be set to a value close to the potential difference VDH.

[0115] In this embodiment, the drive signal Com-B is a signal in which the potential V1z is set to potential VCH and the potential difference VD1z is set to potential difference VDH, as in the drive signal Com-Bz in Verification Example 2. In other words, the drive signal Com-B in this embodiment has a partial waveform PS1 that changes by a potential difference VDH from potential VCH to potential V2. On the other hand, the drive signal Com-Bw in Verification Example 1 has a partial waveform PS1w that changes by a potential difference VD1w from potential V1w, which is closer to the reference potential V0 than potential VCH, to potential V2. That is, the potential difference VDH of the partial waveform PS1 in this embodiment is larger than the potential difference VD1w of the partial waveform PS1w in Verification Example 1. Therefore, the partial waveform PS1 in this embodiment can pull the meniscus MN more strongly in the Z2 direction compared to the partial waveform PS1w in Verification Example 1. As a result, the drive signal Com-B in this embodiment can generate larger vibrations in the discharge unit D[m] driven as the discharge unit DH to be judged, compared to the drive signal Com-Bw in Verification Example 1. Therefore, by using the drive signal Com-B according to this embodiment, it becomes possible to accurately detect both the discharge abnormality of the first embodiment and the discharge abnormality of the second embodiment.

[0116] In this embodiment, during the determination target drive process, the control unit 2 drives the discharge unit D[m] as the determination target discharge unit DH using the drive signal Com-B, and causes the discharge unit D[m] to output a detection potential signal VX[m] to the detection circuit 33. Then, during the determination target drive process, the detection circuit 33 generates a detection signal SK[m] based on the detection potential signal VX[m] detected from the discharge unit D[m]. Subsequently, in the ejection state determination process, the determination unit 8 determines, based on the detection signal SK[m] output from the detection circuit 33, whether the period TC indicated by the detection potential signal VX[m] is greater than or equal to a threshold TC-th1, which is a non-negative real number. If the period TC of the detection potential signal VX[m] is greater than or equal to the threshold TC-th1, the determination unit 8 generates determination information JH[m] indicating that the ink ejection state at the ejection unit D[m] is normal, and supplies this determination information JH[m] to the control unit 2. If the period TC of the detection potential signal VX[m] is less than the threshold TC-th1, the determination unit 8 determines whether the period TC indicated by the detection potential signal VX[m] is greater than or equal to a threshold TC-th2, which is a real number smaller than the threshold TC-th1. The determination unit 8 generates determination information JH[m] indicating that a second type of discharge abnormality has occurred in the discharge unit D[m] if the period TC of the detected potential signal VX[m] is greater than or equal to the threshold TC-th2, and supplies the determination information JH[m] to the control unit 2. On the other hand, the determination unit 8 generates determination information JH[m] indicating that a first type of discharge abnormality has occurred in the discharge unit D[m] if the period TC of the detected potential signal VX[m] is less than the threshold TC-th2, and supplies the determination information JH[m] to the control unit 2.

[0117] Thus, in this embodiment, by driving the ejection unit D[m] with the drive signal Com-B, it is possible to determine whether the ink ejection state in the ejection unit D[m] is normal or not, and if an ejection abnormality occurs in the ejection unit D[m], it is possible to determine whether the ejection abnormality is of the first type or the second type.

[0118] <<5. Conclusion of the Embodiment>> As described above, the inkjet printer 1 according to this embodiment includes a supply circuit 31 capable of selectively supplying to the piezoelectric element PZ[m] a drive signal Com-A for driving the piezoelectric element PZ[m] to eject ink from the nozzle opening N and form an image on the recording paper PP, and a drive signal Com-B for driving the piezoelectric element PZ[m] to determine the presence or absence of foreign matter GT adhering to the inner wall NH of the nozzle opening N, and a determination unit 8 for determining the presence or absence of foreign matter GT adhering to the inner wall NH, wherein the drive signal Com-B includes a partial signal Com-PS1 that changes from potential VCH to potential VCL and a partial signal Com-PS2 that changes from potential VCL to potential VCH, and the determination unit 8 determines the presence or absence of foreign matter GT adhering to the inner wall NH based on vibrations generated in the piezoelectric element PZ[m] after the partial signal Com-PS1 is supplied to the piezoelectric element PZ[m] and then the partial signal Com-PS2 is supplied.

[0119] Therefore, according to this embodiment, it is possible to significantly change the potential of both the partial signal Com-PS1 and the partial signal Com-PS2. Thus, according to this embodiment, the piezoelectric element PZ[m] can be driven significantly by the drive signal Com-B. As a result, according to this embodiment, it is possible to accurately detect discharge abnormalities caused by foreign matter GT adhering to the inner wall NH of the nozzle opening N.

[0120] Furthermore, in this embodiment, the drive signal Com-A is a signal that drives the piezoelectric element PZ[m] to eject ink from the nozzle opening N by changing the potential within the range from potential VLA1 to potential VHA1, and potentials VCH and VCL are not included in the range from potential VLA1 to potential VHA1.

[0121] Therefore, according to this embodiment, it is possible to significantly change the potential of the partial signal Com-PS1 and the partial signal Com-PS2, making it possible to accurately detect discharge abnormalities caused by foreign matter GT adhering to the inner wall NH of the nozzle opening N.

[0122] Also, in the present embodiment, the potential VCH is the highest potential that can be supplied to the piezoelectric element PZ[m] via the supply circuit 31 among the potentials that the drive signal generation unit 4 that generates the drive signal Com-A and the drive signal Com-B can generate, and the potential VCL is the lowest potential that can be supplied to the piezoelectric element PZ[m] via the supply circuit 31 among the potentials that the drive signal generation unit 4 can generate. This may be a feature.

[0123] Therefore, according to the present embodiment, it is possible to greatly change the potential of the partial signal Com-PS1 and also greatly change the potential of the partial signal Com-PS2, and it is possible to accurately detect the ejection abnormality caused by the foreign matter GT adhering to the inner wall NH of the nozzle opening N.

[0124] Also, in the present embodiment, the displacement amount of the meniscus MN at the nozzle opening N when the drive signal Com-B is supplied to the ejection unit D[m] and the piezoelectric element PZ[m] is driven is larger than the displacement amount of the meniscus MN at the nozzle opening N when the drive signal Com-A is supplied to the ejection unit D[m] and the piezoelectric element PZ[m] is driven. This may be a feature.

[0125] <<B. Modified Example>> Each of the above embodiments can be variously modified. Specific modification modes are exemplified below. Two or more modes arbitrarily selected from the following examples can be appropriately combined within a range where they do not conflict with each other. In the modified examples exemplified below, for elements whose actions and functions are equivalent to those of the embodiment, the reference numerals referred to in the above description are reused, and the detailed description of each is appropriately omitted.

[0126] <<Modified Example 1>> In the embodiments described above, the drive signal Com-B is shown as having its potential maintained at potential V3 during the period from the end of the period Td2 in which the partial waveform PS2 is provided to the start of the control period TSS2. However, the present invention is not limited to such embodiments. For example, the potential of the drive signal Com-B may fluctuate during the period from the end of the period Td2 in which the partial waveform PS2 is provided to the start of the control period TSS2.

[0127] Figure 17 is a timing chart showing the drive signal Com-B related to Modification Example 1.

[0128] As shown in Figure 17, the drive signal Com-B in the modified example 1 has a waveform PS-H1 provided for a unit period TP. Here, waveform PS-H1 is a waveform in which, during the control period TSS1, the potential changes from the reference potential V0, through a potential V1 higher than the reference potential V0, a ​​potential V2 lower than the reference potential V0, and a potential V3 higher than the reference potential V0, to a potential V4 higher than the reference potential V0, and in the control period TSS2, the potential V4 is maintained, and in the control period TSS3, the potential changes from V4 to the reference potential V0.

[0129] In this modified example, it is assumed that potential V1 is approximately the same as potential VCH, potential V2 is approximately the same as potential VCL, and potential V3 is approximately the same as potential VCH. Furthermore, in this modified example, it is assumed that potential V4 is the potential between reference potential V0 and potential VCH. However, the present invention is not limited to these embodiments. Potential V4 may be, for example, the potential between potential VLA1 and potential VHA1. In this modified example, potential V4 is an example of a "specific potential".

[0130] Furthermore, in this modified example, the portion of waveform PS-H1 that changes from potential V3 to potential V4 is referred to as partial waveform PS3. Also, in this modified example, the portion of drive signal Com-B that corresponds to partial waveform PS3 is referred to as partial signal Com-PS3. That is, in this modified example, drive signal Com-B includes partial signal Com-PS1 having partial waveform PS1, partial signal Com-PS2 having partial waveform PS2, and partial signal Com-PS3 having partial waveform PS3. Here, partial signal Com-PS3 is an example of a "third partial signal".

[0131] In Modification 1, during the control period TSS1, in period Tv1, the potential of the drive signal Com-B is maintained at potential V1, and during the control period TSS1, in period Td1, a partial waveform PS1 is provided in which the potential of the drive signal Com-B changes from potential V1 to potential V2, during the control period TSS1, in period Tv2, the potential of the drive signal Com-B is maintained at potential V2, and during the control period TSS1, in period Td2, a partial waveform PS2 is provided in which the potential of the drive signal Com-B changes from potential V2 to potential V3, during the control period TSS1, in period Tv3, the potential of the drive signal Com-B is maintained at potential V3, and during the control period TSS1, in period Td3, a partial waveform PS3 is provided in which the potential of the drive signal Com-B changes from potential V3 to potential V4, and during the unit period TP, in period Tv4, the potential of the drive signal Com-B is maintained at potential V4.

[0132] In this modified example, the sum of the durations of period Td2 and Tv3 is adjusted to be approximately the same as α times the duration of the vibration period TC occurring in the discharge section D[m]. In other words, in this modified example, the duration from the start of partial waveform PS2 to the start of partial waveform PS3 is adjusted to be α times the duration of the period TC. Here, the value α is a natural number satisfying "α≧2". In this modified example, the value α is set to "2". The duration from the start of partial waveform PS2 to the start of partial waveform PS3 is an example of a "time limit".

[0133] In this modified example, partial waveform PS3 is started after a time limit twice the period TC has elapsed following the start of partial waveform PS2. Therefore, according to this modified example, compared to the configuration in which a time limit shorter than twice the period TC is set, the phase difference between the vibration that occurs in the ejection unit D[m] when the ink ejection state at the ejection unit D[m] is normal and the vibration that occurs in the ejection unit D[m] when an ejection abnormality occurs is larger. Furthermore, according to this modified example, compared to the configuration in which partial waveform PS3 is not provided, the phase difference between the vibration that occurs in the ejection unit D[m] when the ink ejection state at the ejection unit D[m] is normal and the vibration that occurs in the ejection unit D[m] when an ejection abnormality occurs is larger. Thus, according to this modified example, it is possible to determine the ejection state of the ejection unit D[m] not only based on the period TC of the vibration that occurs in the ejection unit D[m] driven as the ejection unit DH to be determined, but also based on the phase of the vibration that occurs in the ejection unit D[m] driven as the ejection unit DH to be determined.

[0134] In this modified example, in the drive signal Com-B having waveform PS-H1, partial waveform PS3 is started after the start of partial waveform PS2 and after the expiration of a time limit that is α times the period TC. However, the present invention is not limited to this embodiment. For example, in the drive signal Com-B having waveform PS, the control period TSS2 may be started after the start of partial waveform PS2 and after the expiration of a time limit that is α times the period TC.

[0135] As described above, in the inkjet printer 1 according to this modified example, the drive signal Com-B includes a partial signal Com-PS3 that changes from a potential VCH to a potential V4, and the determination unit 8 determines the presence or absence of foreign matter GT adhering to the inner wall NH of the nozzle opening N based on the vibration generated in the piezoelectric element PZ[m] when the partial signal Com-PS3 is supplied to the piezoelectric element PZ[m] after the partial signal Com-PS1 and partial signal Com-PS2 have been supplied to the piezoelectric element PZ[m].

[0136] Furthermore, in the inkjet printer 1 according to this modified example, the drive signal Com-A is a signal that drives the piezoelectric element PZ[m] to eject ink from the nozzle opening N by changing the potential within the range from potential VLA1 to potential VHA1, the drive signal Com-B includes a partial signal Com-PS3 that changes from potential VCH to potential V4, and the determination unit 8 determines the presence or absence of foreign matter GT adhering to the inner wall NH of the nozzle opening N based on the vibrations generated in the piezoelectric element PZ[m] when partial signal Com-PS3 is supplied to the piezoelectric element PZ[m] after partial signal Com-PS1 and partial signal Com-PS2 have been supplied to the piezoelectric element PZ[m], and potentials VCH and VCL are not included in the range from potential VLA1 to potential VHA1, and potential V4 is included in the range from potential VLA1 to potential VHA1.

[0137] Furthermore, in the inkjet printer 1 according to this modified example, the supply circuit 31 may be characterized in that it starts supplying the partial signal Com-PS3 to the piezoelectric element PZ[m] after a time limit of twice the period TC of the vibration occurring in the piezoelectric element PZ[m] has elapsed from the start of supplying the partial signal Com-PS2 to the piezoelectric element PZ[m].

[0138] Therefore, according to this modified example, it is possible to accurately detect discharge abnormalities caused by foreign matter GT adhering to the inner wall NH of the nozzle opening N, based on the phase of vibrations occurring in the piezoelectric element PZ[m].

[0139] <<Modification 2>> In the above-described embodiment and Modification 1, the case in which the drive signal Com-B has a potential V1 that is approximately the same as the potential VCH, a potential V2 that is approximately the same as the potential VCL, and a potential V3 that is approximately the same as the potential VCH was illustrated as an example, but the present invention is not limited to such embodiments. For example, in the drive signal Com-B, the potential V1 that is approximately the same as the potential VCL, a potential V2 that is approximately the same as the potential VCH, and a potential V3 that is approximately the same as the potential VCL may also be present.

[0140] Figure 18 is a timing chart showing the drive signal Com-B related to Modification Example 2.

[0141] As shown in Figure 18, the drive signal Com-B in the modified example 2 has a waveform PS-H2 provided for a unit period TP. Here, waveform PS-H2 is a waveform in which, during control period TSS1, the potential changes from the reference potential V0 to a potential V1 lower than the reference potential V0, then to a potential V2 higher than the reference potential V0, and finally to a potential V3 lower than the reference potential V0. During control period TSS2, the potential V3 is maintained, and during control period TSS3, the potential changes from V3 to the reference potential V0. In this modified example, it is assumed that potential V1 is potential VCL, potential V2 is potential VCH, and potential V3 is potential VCL.

[0142] Specifically, in Modification 2, during the control period TSS1, in period Tv1, the potential of the drive signal Com-B is maintained at potential VCL, and during the control period TSS1, in period Td1, a partial waveform PS1H is provided in which the potential of the drive signal Com-B changes from potential VCL to potential VCH, during the control period TSS1, in period Tv2, the potential of the drive signal Com-B is maintained at potential VCH, and during the control period TSS1, in period Td2, a partial waveform PS2H is provided in which the potential of the drive signal Com-B changes from potential VCH to potential VCL, during the unit period TP, in period Tv3, the potential of the drive signal Com-B is maintained at potential VCL, and after the end of period Tv3, the potential of the drive signal Com-B changes from potential VCL to reference potential V0.

[0143] According to this modification, it is possible to significantly change the potential in the partial waveform PS1H of the drive signal Com-B, and also significantly change the potential in the partial waveform PS2H of the drive signal Com-B. Therefore, according to this modification, the piezoelectric element PZ[m] can be driven significantly by the drive signal Com-B. As a result, according to this modification, it is possible to accurately detect discharge abnormalities caused by foreign matter GT adhering to the inner wall NH of the nozzle opening N.

[0144] <<Modification 3>> In the embodiments and modifications 1 and 2 described above, the determination unit 8 is provided separately from the head unit 3 as an example, but the present invention is not limited to such embodiments.

[0145] Figure 19 is a block diagram showing an example of the configuration of the inkjet printer 1A according to this modified example.

[0146] As shown in Figure 19, inkjet printer 1A differs from the inkjet printer 1 according to the embodiment in that it includes a head unit 3A instead of a head unit 3. Furthermore, head unit 3A differs from head unit 3 according to the embodiment in that it includes a determination unit 8.

[0147] According to this modified configuration, since the determination unit 8 is provided on the head unit 3A, the possibility of noise being introduced into the detection signal SK[m] supplied by the detection circuit 33 to the determination unit 8 can be suppressed compared to the configuration in which the determination unit 8 is provided on the outside of the head unit 3A, thereby improving the accuracy of the determination in the determination unit 8.

[0148] <<Modification 4>> In the embodiments and modifications 1 to 3 described above, it was assumed that the inkjet printer 1 is equipped with four head units 3, but the present invention is not limited to such embodiments. The inkjet printer 1 may be equipped with one to three head units 3, or it may be equipped with five or more head units 3.

[0149] <<Modification 5>> In the embodiments and modifications 1 to 4 described above, the case in which the inkjet printer 1 is a serial printer is illustrated, but the present invention is not limited to such embodiments. The inkjet printer 1 may be a so-called line printer in which a plurality of nozzle openings N in the head unit 3 are provided so as to extend wider than the width of the recording paper PP. [Explanation of symbols]

[0150] 1... Inkjet printer, 2... Control unit, 3... Head unit, 4... Drive signal generation unit, 7... Transport unit, 8... Judgment unit, 31... Supply circuit, 32... Recording head, 33... Detection circuit, D... Discharge section, N... Nozzle opening, NH... Inner wall.

Claims

1. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. The first drive signal is, This signal drives the piezoelectric element to discharge liquid from the nozzle opening by changing the potential within the range of the third potential to the fourth potential. The first potential and the second potential are, Not included in the range from the third potential to the fourth potential, A liquid dispensing device characterized by the following features.

2. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. The first potential is, Of the potentials that the generation unit that generates the first drive signal and the second drive signal can generate, This is one of the highest and lowest potentials that can be supplied to the piezoelectric element via the supply unit. The second potential is, Of the potentials that the generation unit can generate, The other of the highest and lowest potentials that can be supplied to the piezoelectric element via the supply unit, A liquid dispensing device characterized by the following features.

3. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. The second drive signal is, Includes a third partial signal that changes from the first potential to a specific potential, The determination unit, After the first partial signal and the second partial signal have been supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the third partial signal is supplied to the piezoelectric element, To determine whether or not foreign matter is adhering to the inner wall, A liquid dispensing device characterized by the following features.

4. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. The first drive signal is, This signal drives the piezoelectric element to discharge liquid from the nozzle opening by changing the potential within the range of the third potential to the fourth potential. The second drive signal is, Includes a third partial signal that changes from the first potential to a specific potential, The determination unit, After the first partial signal and the second partial signal have been supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the third partial signal is supplied to the piezoelectric element, Determine whether or not there is any foreign matter adhering to the inner wall. The first potential and the second potential are, Not included in the range from the third potential to the fourth potential, The aforementioned specific potential is The range from the third potential to the fourth potential includes, A liquid dispensing device characterized by the following features.

5. The aforementioned supply unit is From the start of supplying the second partial signal to the piezoelectric element, After a time limit equal to twice the period of vibration occurring in the piezoelectric element has elapsed, The supply of the third partial signal to the piezoelectric element is started. A liquid dispensing device according to claim 3 or 4, characterized in that it is a liquid dispensing device according to claim 3 or 4.

6. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. When the second drive signal is supplied and the piezoelectric element is driven, the amount of displacement of the liquid level at the nozzle opening is: When the first drive signal is supplied and the piezoelectric element is driven, the displacement of the liquid level at the nozzle opening is greater than the displacement of the liquid level at the nozzle opening. A liquid dispensing device characterized by the following features.

7. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. The first drive signal is, This signal drives the piezoelectric element to discharge liquid from the nozzle opening by changing the potential within the range of the third potential to the fourth potential. The first potential and the second potential are, Not included in the range from the third potential to the fourth potential, A head unit characterized by the following features.

8. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. The first potential is, Of the potentials that the generation unit that generates the first drive signal and the second drive signal can generate, This is one of the highest and lowest potentials that can be supplied to the piezoelectric element via the supply unit. The second potential is, Of the potentials that the generation unit can generate, The other of the highest and lowest potentials that can be supplied to the piezoelectric element via the supply unit, A head unit characterized by the following features.

9. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. The second drive signal is, Includes a third partial signal that changes from the first potential to a specific potential, The determination unit, After the first partial signal and the second partial signal have been supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the third partial signal is supplied to the piezoelectric element, To determine whether or not foreign matter is adhering to the inner wall, A head unit characterized by the following features.

10. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. The first drive signal is, This signal drives the piezoelectric element to discharge liquid from the nozzle opening by changing the potential within the range of the third potential to the fourth potential. The second drive signal is, Includes a third partial signal that changes from the first potential to a specific potential, The determination unit, After the first partial signal and the second partial signal have been supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the third partial signal is supplied to the piezoelectric element, Determine whether or not there is any foreign matter adhering to the inner wall. The first potential and the second potential are, Not included in the range from the third potential to the fourth potential, The aforementioned specific potential is The range from the third potential to the fourth potential includes, A head unit characterized by the following features.

11. The aforementioned supply unit is From the start of supplying the second partial signal to the piezoelectric element, After a time limit equal to twice the period of vibration occurring in the piezoelectric element has elapsed, The supply of the third partial signal to the piezoelectric element is started. The head unit according to claim 9 or 10, characterized in that...

12. A first drive signal drives a piezoelectric element to form an image on a medium by discharging liquid from a nozzle opening, and A second drive signal is used to drive the piezoelectric element in order to determine whether or not there is foreign matter adhering to the inner wall of the nozzle opening. A supply unit capable of selectively supplying to the piezoelectric element, A determination unit for determining whether or not foreign matter is attached to the inner wall, Equipped with, The second drive signal is, The first partial signal changes from the first potential to the second potential, A second partial signal that changes from the second potential to the first potential, Includes, The determination unit, After the first partial signal is supplied to the piezoelectric element, Based on the vibrations generated in the piezoelectric element when the second partial signal is supplied, Determine whether or not there is any foreign matter adhering to the inner wall. When the second drive signal is supplied and the piezoelectric element is driven, the amount of displacement of the liquid level at the nozzle opening is: When the first drive signal is supplied and the piezoelectric element is driven, the displacement of the liquid level at the nozzle opening is greater than the displacement of the liquid level at the nozzle opening. A head unit characterized by the following features.

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