DRIVE DEVICE AND METHOD FOR CONTROLLING DRIVE DEVICE

Abstract

To accurately detect vibration generated in a piezoelectric element.SOLUTION: A driving device includes a piezoelectric element which has a drive electrode and is driven by a drive signal supplied to the drive electrode through first wiring, a first switch which switches between electrical connection and disconnection of the first wiring and drive electrode, a detection circuit which detects vibration generated in the piezoelectric element driven by the drive signal as a potential change of the drive electrode through second wiring, a second switch which switches between electrical connection and disconnection of the second wiring and drive electrode, and a determination circuit which determines a state of the piezoelectric element. The second switch maintains an off-state in a first period, maintains an on-state in a second period subsequent to the first period, maintains an off-state in a third period subsequent to the second period, and maintains an on-state in a fourth period subsequent to the third period. The determination circuit determines a state of the piezoelectric element on the basis of a detection result by the detection circuit in at least a partial period in the fourth period.SELECTED DRAWING: Figure 15

Description

[Technical field]

[0001] The present invention relates to a drive device and a control method for the drive device. [Background technology]

[0002] Driving devices equipped with a driving electrode and a piezoelectric element driven by a driving signal supplied to the driving electrode, such as inkjet printers, are in widespread use. In such driving devices, a technique has been proposed for detecting vibrations generated in the piezoelectric element driven by the driving signal and judging the state of the piezoelectric element based on the detection result (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-114049 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, a switch that electrically connects or disconnects a drive electrode of a piezoelectric element and a detection circuit that detects vibrations generated in the piezoelectric element may generate noise due to opening and closing of the switch, which may cause the detection circuit to be unable to accurately detect vibrations generated in the piezoelectric element. [Means for solving the problem]

[0005] In order to solve the above problems, the driving device of the present invention comprises a piezoelectric element having a driving electrode and driven by a driving signal supplied to the driving electrode via a first wiring, a first switch for switching whether or not to electrically connect the first wiring and the driving electrode, a detection circuit for detecting vibrations generated in the piezoelectric element driven by the drive signal as a potential change of the driving electrode via a second wiring, a second switch for switching whether or not to electrically connect the second wiring and the driving electrode, and a judgment circuit for determining a state of the piezoelectric element, wherein the second switch maintains an off state during a first period, maintains an on state during a second period following the first period, maintains an off state during a third period following the second period, and maintains an on state during a fourth period following the third period, and the judgment circuit determines the state of the piezoelectric element based on the detection result by the detection circuit during at least a portion of the fourth period.

[0006] In addition, a control method for a drive device according to the present invention is a control method for a drive device including a piezoelectric element having a drive electrode and driven by a drive signal supplied to the drive electrode via a first wiring, a first switch for switching whether to electrically connect the first wiring and the drive electrode, a detection circuit for detecting vibrations generated in the piezoelectric element driven by the drive signal as a potential change of the drive electrode via a second wiring, and a second switch for switching whether to electrically connect the second wiring and the drive electrode, wherein the control method controls the second switch to maintain an off state during a first period, maintain an on state during a second period following the first period, maintain an off state during a third period following the second period, and maintain an on state during a fourth period following the third period, and determines a state of the piezoelectric element based on a detection result by the detection circuit during at least a portion of the fourth period. [Brief description of the drawings]

[0007] [Figure 1]FIG. 1 is a block diagram showing an example of the configuration of an inkjet printer 1 according to an embodiment of the invention. [Diagram 2] FIG. 1 is a perspective view showing an example of a schematic internal structure of an inkjet printer 1. [Diagram 3] 13 is a cross-sectional view illustrating an example of the structure of a discharge section D[m]. FIG. [Figure 4] 2 is a plan view showing an example of an arrangement of nozzles N in a head unit 3. FIG. [Diagram 5] 2 is a block diagram showing an example of the configuration of a head unit 3. FIG. [Figure 6] 4 is a block diagram showing an example of the configuration of a detection circuit 33. FIG. [Figure 7] 4 is a timing chart showing an example of the operation of the head unit 3. [Figure 8] FIG. 11 is an explanatory diagram illustrating an example of an individual designation signal Sd[m]. [Figure 9] 4 is a timing chart showing an example of the operation of the head unit 3. [Figure 10] FIG. 11 is an explanatory diagram illustrating an example of an individual designation signal Sd[m]. [Figure 11] FIG. 11 is an explanatory diagram illustrating an example of an individual designation signal Sd[m]. [Figure 12] 2 is an explanatory diagram for explaining an example of a connection state designation signal Qf, a connection state designation signal Q1, and a connection state designation signal Q2. FIG. [Figure 13] 4 is a timing chart showing an example of the operation of the head unit 3. [Figure 14] 4 is an explanatory diagram showing an example of the operation of the head unit 3. FIG. [Figure 15] 4 is an explanatory diagram showing an example of the operation of the head unit 3. FIG. [Figure 16] 4 is an explanatory diagram showing an example of the operation of the head unit 3. FIG. [Figure 17] 4 is an explanatory diagram showing an example of the operation of the head unit 3. FIG. [Figure 18] 4 is an explanatory diagram showing an example of the operation of the head unit 3. FIG. [Figure 19] It is an explanatory diagram showing an example of the operation of the head unit 3. [Figure 20] It is an explanatory diagram showing an example of the operation of the head unit 3. [Figure 21] It is an explanatory diagram for explaining an example of the operation of the determination unit 8. [Figure 22] It is a timing chart showing an example of the operation of the head unit 3 according to the reference example.

Embodiments 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. In addition, the embodiments described below are preferred specific examples of the present invention, so various technically preferable limitations are imposed, but the scope of the present invention is not limited to these embodiments unless there is a description to particularly limit the present invention in the following description.

[0009] <<A. Embodiment>> In this embodiment, a drive device will be described by exemplifying an inkjet printer that ejects ink to form an image on a recording paper P. In this embodiment, the ink is an example of a "liquid", and the recording paper P is an example of a "medium".

[0010] <<1. Outline of Inkjet Printer>> Hereinafter, with reference to FIGS. 1 to 4, an example of the configuration of the inkjet printer 1 according to this embodiment will be described.

[0011] FIG. 1 is a functional block diagram showing an example of the configuration of the inkjet printer 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 an image indicated by the print data Img supplied from the host computer on the recording paper P.

[0012] As illustrated in FIG. 1, the inkjet printer 1 includes a control unit 2 that controls each component of the inkjet printer 1, a head unit 3 that is provided with an ejection section D that ejects ink, a drive signal generation unit 4 that generates a drive signal Com for driving the ejection section D, a transport unit 7 that changes the relative position of the recording paper P with respect to the head unit 3, and a judgment unit 8 that judges the ink ejection state at the ejection section D.

[0013] In this embodiment, it is assumed that the inkjet printer 1 includes one or more head units 3, one or more drive signal generating units 4 in one-to-one correspondence with the one or more head units 3, and one or more determination units 8 in one-to-one correspondence with the one or more head units 3. However, for ease of explanation, the following description focuses on one head unit 3 out of the one or more head units 3, one drive signal generating unit 4 provided corresponding to the one head unit 3, and one determination unit 8 provided corresponding to the one head unit 3, as illustrated in FIG.

[0014] The control unit 2 is configured to include one or more CPUs. However, the 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.

[0015] Although details will be described later, the control unit 2 generates signals for controlling the operation of each part of the inkjet printer 1, such as a print signal SI and a waveform designation signal dCom. Here, the waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the discharge section D. The drive signal generation unit 4 includes a DA conversion circuit and generates the drive signal Com having a waveform defined by the waveform designation signal dCom. The print signal SI is a digital signal for designating the type of operation of the discharge section D. Specifically, the print signal SI is a signal that designates whether or not to supply the drive signal Com to the discharge section D, thereby designating the type of operation of the discharge section D.

[0016] As illustrated in FIG. 1, the head unit 3 includes a supply circuit 31, a recording head 32, and a detection circuit 33.

[0017] The recording head 32 has M discharge sections D. Here, the value M is a natural number that satisfies "M≧1". In the following, the m-th discharge section D of the M discharge sections D provided in the recording head 32 may be referred to as discharge section D[m]. Here, the variable m is a natural number that satisfies "1≦m≦M". In the following, when a component or signal of the inkjet printer 1 corresponds to a discharge section D[m] of the M discharge sections D, the subscript [m] may be added to the symbol representing the component or signal.

[0018] The supply circuit 31 switches whether to supply the drive signal Com to the discharge section D[m] based on the print signal SI. In the following, the drive signal Com supplied to the discharge section D[m] may be referred to as a supply drive signal Vin[m]. In addition, the supply circuit 31 switches whether to supply the detection potential signal VX[m] indicating the potential of the upper electrode Zu[m] of the piezoelectric element PZ[m] included in the discharge section D[m] to the detection circuit 33 based on the print signal SI. The piezoelectric element PZ[m] and the upper electrode Zu[m] will be described later with reference to FIG. 3.

[0019] The detection circuit 33 generates a detection signal SK[m] based on the detection potential signal VX[m] supplied from the discharge section D[m] via the supply circuit 31. 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.

[0020] The judgment unit 8 includes a circuit that judges whether the ink ejection state in the ejection section D[m] is normal or not, that is, whether the ejection section D[m] is in a normal ejection state without any ejection abnormality, based on the detection signal SK[m], and generates ejection state judgment information JH[m] indicating the judgment result. Here, the ejection abnormality is a general term for an abnormality in the ink ejection state in the ejection section D[m], that is, a state in which ink cannot be ejected accurately from the nozzle N equipped in the ejection section D[m]. For example, the ejection abnormality includes a state in which ink cannot be ejected from the ejection section D[m], a state in which the ejection section D[m] ejects an amount of ink different from the ink ejection amount defined by the drive signal Com, and a state in which the ejection section D[m] ejects ink at a speed different from the ink ejection speed defined by the drive signal Com. The circuit included in the judgment unit 8 is an example of a "judgment circuit".

[0021] Hereinafter, the process relating to the determination of the ink ejection state by the determination unit 8 will be referred to as an ejection state determination process. Furthermore, in this embodiment, prior to executing the ejection state determination process, the inkjet printer 1 executes an ejection state determination preparation process, which is a process for improving the accuracy of the determination in the ejection state determination process. The details will be described later, but the ejection state determination preparation process is a process in which the ejection section D[m] is driven by the drive signal Com, and a detection potential signal VX[m] indicating the potential of the upper electrode Zu[m] of the ejection section D[m] is supplied to the detection circuit 33. In the following, the discharge section D[m] that is the subject of the discharge state determination process may be referred to as the determination target discharge section DH. In the following, the discharge section D[m] that is the subject of the discharge state determination preparation process may be referred to as the determination preparation discharge section DJ. In the following, the determination target discharge section DH and the determination preparation discharge section DJ may be referred to as the detection target discharge section DK. In the following, the discharge section D[m] that does not fall under the detection target discharge section DK may be referred to as the non-detection target discharge section DP.

[0022] When a printing process is being performed, the control unit 2 generates signals, such as a print signal SI, for controlling the head unit 3 based on the print data Img. When a printing process is being performed, the control unit 2 also generates signals, such as a waveform designation signal dCom, for controlling the drive signal generating unit 4. When a printing process is being performed, the control unit 2 also generates signals for controlling the transport unit 7. In this way, during the printing process, the control unit 2 controls the transport unit 7 so as to change the relative position of the recording paper P with respect to the head unit 3, while adjusting the presence or absence of ink ejection from the ejection unit D[m], the amount of ink ejection, the timing of ink ejection, and the like, 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 P.

[0023] Furthermore, when the discharge state determination process is executed, the control unit 2 generates a print signal SI that specifies that the discharge section D[m] is driven as the discharge section DH to be determined, and supplies the print signal SI to the supply circuit 31. In this case, the print signal SI specifies that the detected potential signal VX[m] is supplied from the discharge section D[m] to the detection circuit 33. Thereafter, in the discharge state determination process, the detection circuit 33 generates a detection signal SK[m] based on the detected potential signal VX[m] supplied via the supply circuit 31 from the discharge section D[m] driven as the discharge section DH to be determined. Then, in the discharge state determination process, the determination unit 8 generates discharge state determination information JH[m] based on the detection signal SK[m] supplied from the detection circuit 33.

[0024] Furthermore, when the discharge state determination preparation process is executed, the control unit 2 generates a print signal SI that specifies that the discharge section D[m] is driven as a determination preparation discharge section DJ, and supplies the print signal SI to the supply circuit 31. In this case, the print signal SI specifies that the detection potential signal VX[m] is supplied from the discharge section D[m] to the detection circuit 33. Note that the determination unit 8 does not generate the discharge state determination information JH[m] in the discharge state determination preparation process.

[0025] FIG. 2 is a perspective view showing an example of a schematic internal structure of the inkjet printer 1. As shown in FIG. In this embodiment, it is assumed that the inkjet printer 1 is a serial printer, as shown in the example of Fig. 2. Specifically, when executing a printing process, the inkjet printer 1 transports the recording paper P in the sub-scanning direction, while reciprocating the head unit 3 in the main scanning direction that intersects the sub-scanning direction, and ejects ink from the ejection section D[m] to form dots on the recording paper P according to the print data Img. Hereinafter, the +X direction and its opposite direction, the -X direction, will be collectively referred to as the "X-axis direction", the +Y direction intersecting the X-axis direction and its opposite direction, the -Y direction, will be collectively referred to as the "Y-axis direction", and the +Z direction intersecting the X-axis and Y-axis directions and its opposite direction, the -Z direction, will be collectively referred to as the "Z-axis direction". In this embodiment, as illustrated in Fig. 2, the direction from the -X side, which is the upstream side, to the +X side, which is the downstream side, is the sub-scanning direction, and the +Y direction and the -Y direction are the main scanning direction.

[0026] As shown in FIG. 2, the inkjet printer 1 according to this embodiment includes a housing 100, and a carriage 110 that is capable of reciprocating within the housing 100 in the Y-axis direction and that has one or more head units 3 mounted thereon. In this embodiment, as shown in FIG. 2, it is assumed that the carriage 110 stores four ink cartridges 120 in one-to-one correspondence with the four colors of ink: cyan, magenta, yellow, and black. In addition, in this embodiment, it is assumed, as an example, that the inkjet printer 1 includes four head units 3 in one-to-one correspondence with the four ink cartridges 120. Each ejection section D[m] receives a supply of ink from the ink cartridge 120 corresponding to the head unit 3 in which the ejection section D[m] is provided. This allows each ejection section D[m] to fill itself with the supplied ink and eject the filled ink from the nozzle N. The ink cartridge 120 may be provided outside the carriage 110. The nozzle N will be described later with reference to FIG. 3.

[0027] As described above, the inkjet printer 1 according to this embodiment also includes a transport unit 7. As illustrated in Fig. 1, the transport unit 7 includes a carriage transport mechanism 71 for reciprocating the carriage 110 in the Y-axis direction, a carriage guide shaft 76 that supports the carriage 110 so that it can reciprocate in the Y-axis direction, a medium transport mechanism 73 for transporting the recording paper P, and a platen 75 provided on the -Z side of the carriage 110. Thus, when a printing process is performed, the transport unit 7 causes 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 transports the recording paper P on the platen 75 in the +X direction by transporting the recording paper P on the platen 75 in the +X direction, thereby changing the relative position of the recording paper P with respect to the head unit 3 and enabling ink to land on the entire recording paper P.

[0028] FIG. 3 is a schematic partial cross-sectional view of the recording head 32, in which the recording head 32 is cut so as to include the ejection portion D[m].

[0029] As illustrated in FIG. 3, the ejection section D[m] includes a piezoelectric element PZ[m], a cavity 322 filled with ink, a nozzle N communicating with the cavity 322, and a vibration plate 321. The ejection section D[m] ejects ink in the cavity 322 from the nozzle N when the piezoelectric element PZ[m] is driven by a supply drive signal Vin[m]. The cavity 322 is a space defined by a cavity plate 324, a nozzle plate 323 in which the nozzle N is formed, and the vibration plate 321. The cavity 322 communicates with a reservoir 325 via an ink supply port 326. The reservoir 325 communicates with the ink cartridge 120 corresponding to the ejection section 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 upper electrode Zu[m] is an example of a "drive electrode". The lower electrode Zd[m] is electrically connected to a power supply line Lb set to a 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 +Z direction or the -Z 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 vibration plate 321. Therefore, when the piezoelectric element PZ[m] is driven to vibrate by the supply drive signal Vin[m], the vibration plate 321 also vibrates. The vibration of the diaphragm 321 changes the volume of the cavity 322 and the pressure within the cavity 322, causing the ink filled within the cavity 322 to be ejected from the nozzle N.

[0030] Figure 4 is an explanatory diagram showing an example of the arrangement of four head units 3 mounted on a carriage 110 and a total of 4M nozzles N provided in the four head units 3 when the inkjet printer 1 is viewed in a planar view from the -Z direction.

[0031] 4, a nozzle row NL is provided in each head unit 3 provided in the carriage 110. Here, the nozzle row NL is a plurality of nozzles N arranged to extend in a row in a predetermined direction. In this embodiment, it is assumed as an example that each nozzle row NL is composed of M nozzles N arranged to extend in the X-axis direction.

[0032] <<2. Head unit configuration>> The configuration of the head unit 3 will be described below with reference to FIGS.

[0033] Fig. 5 is a block diagram showing an example of the configuration of the head unit 3. As described above, the head unit 3 includes a supply circuit 31, a recording head 32, and a detection circuit 33. Note that Fig. 5 shows, as an example, a case where four ejection sections D are provided in the recording head 32, that is, a case where "M=4".

[0034] 5, the head unit 3 includes a wiring Lc to which the drive signal Com is supplied from the drive signal generating unit 4, and a wiring Ls for supplying the detected potential signal VX[m] to the detection circuit 33. The wiring Lc is an example of a "first wiring," and the wiring Ls is an example of a "second wiring."

[0035] As illustrated in FIG. 5, the supply circuit 31 includes M switches Wc[1] to Wc[M] each having a one-to-one correspondence with the M discharge sections D[1] to D[M], M switches Ws[1] to Ws[M] each having a one-to-one correspondence with the M discharge sections D[1] to D[M], a switch Wf, a resistor Rf, and a connection state designation circuit 310 that designates the connection state of each switch. The connection state designation circuit 310 generates a connection state designation signal Qc[m] that specifies the on / off state of the switch Wc[m], a connection state designation signal Qs[m] that specifies the on / off state of the switch Ws[m], a connection state designation signal Qf that specifies the on / off state of the switch Wf, a connection state designation signal Q1 described later, and a connection state designation signal Q2 described later, based on at least some of the signals of the print signal SI, the latch signal LAT, the period designation signal Tsig, and the change signal CH supplied from the control unit 2.

[0036] The switch Wc[m] switches between electrical continuity and non-conduction between the wiring Lc and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] based on the connection state designation signal Qc[m]. In this embodiment, the switch Wc[m] is turned on when the connection state designation signal Qc[m] is at a high level, and turned off when the connection state designation signal Qc[m] is at a low level. When the switch Wc[m] is turned on, the drive signal Com supplied to the wiring Lc is supplied to the upper electrode Zu[m] of the discharge section D[m] as the supply drive signal Vin[m]. The switch Wc[m] is an example of a "first switch." The switch Ws[m] switches between electrical continuity and non-conduction between the wiring Ls and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[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 the connection state designation signal Qs[m] is at a low level. When the switch Ws[m] is turned on, the potential of the upper electrode Zu[m] of the discharge section D[m] is supplied to the detection circuit 33 via the wiring Ls as a detection potential signal VX[m]. The switch Ws[m] is an example of a "second switch." The switch Wf switches between conduction and non-conduction between the wiring Lc and the wiring Ls based on a connection state designation signal Qf. In this embodiment, the switch Wf is on when the connection state designation signal Qf is at a high level and is off when the connection state designation signal Qf is at a low level. When the switch Wf is on, the drive signal Com supplied to the wiring Lc is supplied to a node Nd0, which is a part of the wiring Ls, via a resistor Rf electrically connected between the switch Wf and the wiring Ls. The switch Wf is an example of a "third switch," and the resistor Rf is an example of a "first resistor."

[0037] FIG. 6 is a block diagram showing an example of the configuration of the detection circuit 33. As shown in FIG.

[0038] As illustrated in FIG. 6, the detection circuit 33 includes capacitors CP1 to CP3, operational amplifiers OP1 to OP2, switches W1 to W2, and resistors RS1 to RS5.

[0039] The capacitor CP1 has one electrode electrically connected to the node Nd0 and the other electrode electrically connected to the node Nd1. The resistor RS1 has one end electrically connected to the node Nd1 and the other end electrically connected to an analog ground AGND set to a fixed potential. Specifically, the potential of the analog ground AGND may be, for example, a center potential between a high-potential power supply potential and a low-potential power supply potential supplied to the head unit 3. The switch W1 switches between electrical continuity and non-conduction between one end of the resistor RS1 and the analog ground AGND. In this embodiment, the switch SW1 is turned on when the connection state designation signal Q1 is at a high level, and turned off when the connection state designation signal Q1 is at a low level. In this embodiment, the capacitor CP1, the resistor RS1, and the switch SW1 function as a high-pass filter.

[0040] The operational amplifier OP1 includes a non-inverting input terminal electrically connected to a node Nd1, an output terminal electrically connected to a node Nd2, and an inverting input terminal electrically connected to the node Nd2 via a resistor RS2 and to an analog ground AGND via a resistor RS3. In this embodiment, the operational amplifier OP1, the resistor RS2, and the resistor RS3 function as an amplifier circuit that amplifies the amplitude of a signal input to the node Nd1 and outputs the signal to the node Nd2.

[0041] The operational amplifier OP2 includes a non-inverting input terminal electrically connected to the node Nd2, an inverting input terminal electrically connected to the node Nd3, and an output terminal electrically connected to the node Nd3. In this embodiment, the operational amplifier OP2 functions as a buffer that converts impedance and outputs a low impedance signal to the node Nd3.

[0042] The switch W2 switches between conduction and non-conduction between the node Nd3 and the node Nd4. In this embodiment, the switch SW2 is turned on when the connection state designation signal Q2 is at a high level, and is turned off when the connection state designation signal Q2 is at a low level.

[0043] The capacitor CP2 has one electrode electrically connected to the node Nd4 and the other electrode electrically connected to the analog ground AGND. The resistor RS4 has one end electrically connected to the node Nd4 and the other end electrically connected to the power supply line LH set to a fixed potential. Specifically, the potential of the power supply line LH may be, for example, a high-potential power supply potential supplied to the head unit 3. The resistor RS5 has one end electrically connected to the node Nd4 and the other end electrically connected to the analog ground AGND. The capacitor CP3 has one electrode electrically connected to a node Nd4 and the other electrode electrically connected to a node Nd5. The node Nd5 is electrically connected to the judgment unit 8. In this embodiment, the signal output to the node Nd5 corresponds to the detection signal SK[m].

[0044] As described above, the detection circuit 33 generates the detection signal SK[m] based on the detection potential signal VX[m] input to the node Nd0, and outputs the generated detection signal SK[m] from the node Nd5.

[0045] <<3. Head unit operation>> Hereinafter, the operation of the head unit 3 will be described with reference to FIGS.

[0046] In this embodiment, when the inkjet printer 1 executes a printing process, a discharge state determination process, or a discharge state determination preparation 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 according to this embodiment can drive each discharge section D[m] for the printing process, the discharge state determination process, or the discharge state determination preparation process. Note that, below, the kth unit period TP out of K consecutive unit periods TP may be expressed as unit period TP(k). Here, the value K is a natural number that satisfies "K≧1", and the variable k is a natural number that satisfies "1≦k≦K".

[0047] 7 is a timing chart for explaining an example of various signals supplied to the head unit 3 in a unit period TP when a print process is executed in the unit period TP. Note that, hereinafter, the unit period TP in which the print process is executed may be referred to as a print unit period TPP.

[0048] 7, the control unit 2 outputs a latch signal LAT having a pulse PLL, whereby the control unit 2 defines a unit period TP as a period from the rising edge of the pulse PLL to the rising edge of the next pulse PLL. In addition, the control unit 2 outputs a change signal CH having a pulse PLC in a unit period TP. The control unit 2 divides the unit period TP into a control period TQ1 from the rising edge of the pulse PLL to the rising edge of the pulse PLC, and a control period TQ2 from the rising edge of the pulse PLC to the rising edge of the pulse PLL. Furthermore, the control unit 2 outputs a period designation signal Tsig during the unit period TP. The period designation signal Tsig will be described later.

[0049] The print signal SI according to this embodiment includes M individual designation signals Sd[1] to Sd[M] that correspond one-to-one to the M discharge sections D[1] to D[M]. The individual designation signal Sd[m] designates the mode of driving the discharge section D[m] in each unit period TP. 7, prior to each unit period TP, the control unit 2 supplies a print signal SI including individual designation signals Sd[1]-Sd[M] to the connection state designation circuit 310 in synchronization with the clock signal CL. Then, during the unit period TP, the connection state designation circuit 310 generates a connection state designation signal Qc[m], a connection state designation signal Qs[m], and a connection state designation signal Qf based on the individual designation signal Sd[m].

[0050] In this embodiment, it is assumed that the discharge section D[m] is capable of forming any of a large dot, a medium dot smaller than a large dot, or a small dot smaller than a medium dot, during the printing unit period TPP. In this embodiment, it is assumed that the individual designation signal Sd[m] can take any one of four values ​​during the printing unit period TPP: a value "1" that designates the discharge section D[m] as a large-dot-forming discharge section DP-1, which is a non-detection discharge section DP that discharges an amount of ink equivalent to a large dot; a value "2" that designates it as a medium-dot-forming discharge section DP-2, which is a non-detection discharge section DP that discharges an amount of ink equivalent to a medium dot; a value "3" that designates it as a small-dot-forming discharge section DP-3, which is a non-detection discharge section DP that discharges an amount of ink equivalent to a small dot; and a value "4" that designates it as a non-dot-forming discharge section DP-4, which is a non-detection discharge section DP that does not discharge ink.

[0051] As shown in FIG. 7, in this embodiment, in the print unit period TPP, the driving signal Com has a waveform PP1 provided in the control period TQ1 and a waveform PP2 provided in the control period TQ2. Among these, the waveform PP1 is a waveform that goes from a reference potential V0, through a potential VL1 lower than the reference potential V0, and a potential VH1 higher than the reference potential V0, and then returns to the reference potential V0. When the supply driving signal Vin[m] having the waveform PP1 is supplied to the discharge section D[m], the waveform PP1 is determined so that ink equivalent to the ink amount ξ1 is discharged from the discharge section D[m]. In addition, the waveform PP2 is a waveform that goes from the reference potential V0, through a potential VL2 lower than the reference potential V0, and a potential VH2 higher than the reference potential V0, and then returns to the reference potential V0. The waveform PP2 is determined so that when the supply drive signal Vin[m] having the waveform PP2 is supplied to the discharge section D[m], ink equivalent to the ink amount ξ2 is discharged from the discharge section D[m]. In this embodiment, the ink amount ξ1 corresponds to a medium dot. The ink amount ξ2 is smaller than the ink amount ξ1 and corresponds to a small dot. The sum of the ink amount ξ1 and the ink amount ξ2 corresponds to a large dot. In this embodiment, as an example, it is assumed that when the potential of the supply drive signal Vin[m] supplied to the discharge section D[m] is high, the volume of the cavity 322 of the discharge section D[m] is smaller than when the potential is low. Therefore, when the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveform PP1 or PP2, the potential of the supply drive signal Vin[m] changes from low to high, causing the ink in the discharge section D[m] to be discharged from the nozzle N.

[0052] FIG. 8 is an explanatory diagram for explaining the relationship between the individual designation signal Sd[m] and the connection state designation signal Qc[m], the connection state designation signal Qs[m], and the connection state designation signal Qf in the print unit period TPP.

[0053] 8, when the individual designation signal Sd[m] indicates a value of "1" that designates the discharge section D[m] as the large dot forming discharge section DP-1 in the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qc[m] to a high level over the control periods TQ1 and TQ2. In this case, the switch Wc[m] maintains an on state over the unit period TP. Therefore, the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveforms PP1 and PP2 in the unit period TP, and discharges an amount of ink equivalent to a large dot. Furthermore, when the individual designation signal Sd[m] indicates a value of "2" that designates the discharge section D[m] as the medium dot forming discharge section DP-2 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qc[m] to a high level during the control period TQ1. In this case, the switch Wc[m] maintains the on state during the control period TQ1. Therefore, the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveform PP1 during the unit period TP, and discharges an amount of ink equivalent to a medium dot. Furthermore, when the individual designation signal Sd[m] indicates a value of "3" that designates the discharge section D[m] as the small dot forming discharge section DP-3 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qc[m] to a high level during the control period TQ2. In this case, the switch Wc[m] maintains an on state during the control period TQ2. Therefore, during the unit period TP, the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveform PP2, and discharges an amount of ink equivalent to a small dot. Furthermore, when the individual designation signal Sd[m] indicates a value of "4" that designates the discharge section D[m] as a non-dot-forming discharge section DP-4 during the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qc[m] to a low level during the unit period TP. In this case, the switch Wc[m] maintains an off state during the unit period TP. Therefore, the supply drive signal Vin[m] is not supplied to the discharge section D[m] during the unit period TP, and ink is not discharged from the discharge section D[m]. In addition, in a printing unit period TPP in which the individual designation signal Sd[m] designates the discharge section D[m] as the non-detection discharge section DP in the printing unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qs[m] and the connection state designation signal Qf to a low level throughout the printing unit period TPP. In other words, the switch Ws[m] and the switch Wf maintain the off state throughout the printing unit period TPP.

[0054] 9 is a timing chart for explaining an example of various signals supplied to the head unit 3 in a unit period TP when the ejection state determination process or the ejection state determination preparation process is executed in the unit period TP. Note that, hereinafter, the unit period TP in which the ejection state determination process or the ejection state determination preparation process is executed may be referred to as an ejection determination unit period TPS.

[0055] 9, the control unit 2 outputs a period designation signal Tsig having a pulse PLT1 and a pulse PLT2 in a unit period TP. The control unit 2 divides the unit period TP into a control period TT1 which is a period from the rising edge of the pulse PLL to the rising edge of the pulse PLT1, a control period TT2 which is a period from the rising edge of the pulse PLT1 to the falling edge of the pulse PLT1, a control period TT3 which is a period from the falling edge of the pulse PLT1 to the rising edge of the pulse PLT2, a control period TT4 which is a period from the rising edge of the pulse PLT2 to the falling edge of the pulse PLT2, and a control period TT5 which is a period from the rising edge of the pulse PLT2 to the rising edge of the pulse PLL.

[0056] 9, in this embodiment, the driving signal Com has a waveform PS in the discharge determination unit period TPS. Here, the waveform PS is a waveform that changes from a reference potential V0 to a potential VS1 lower than the reference potential V0, and then to a potential VS2 higher than the reference potential V0 in a control period TT1, maintains the potential VS2 in control periods TT2, TT3, and TT4, and changes from the potential VS2 to the reference potential V0 in a control period TT5. Note that, in this embodiment, as an example, it is assumed that the waveform PS is determined so that ink is not discharged from the discharge section D[m] when a supply driving signal Vin[m] having the waveform PS is supplied to the discharge section D[m].

[0057] FIG. 10 is an explanatory diagram for explaining the relationship between the individual designation signal Sd[m] and the connection state designation signal Qc[m] in the discharge determination unit period TPS.

[0058] In this embodiment, as illustrated in Figure 10, it is assumed that the individual designation signal Sd[m] can take one of two values ​​during the discharge judgment unit period TPS: a value of "5" that designates the discharge section D[m] as a judgment preparation discharge section DJ, and a value of "6" that designates it as a discharge section DH to be judged.

[0059] 10, when the individual designation signal Sd[m] indicates a value "5" that designates the discharge unit D[m] as the judgment preparation discharge unit DJ in the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qc[m] so that the connection state designation signal Qc[m] is maintained at a high level in the control periods TT1 and TT2, and at a low level in the control periods TT3, TT4, and TT5. In this case, the switch Wc[m] is maintained in an on state in the control periods TT1 and TT2. Furthermore, when the individual designation signal Sd[m] indicates a value "6" that designates the discharge section D[m] as the discharge section DH to be determined in the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qc[m] so that the connection state designation signal Qc[m] is maintained at a high level in the control periods TT1, TT2, and TT5, and at a low level in the control periods TT3 and TT4. In this case, the switch Wc[m] is maintained in an on state in the control periods TT1, TT2, and TT5.

[0060] FIG. 11 is an explanatory diagram for explaining the relationship between the individual designation signal Sd[m] and the connection state designation signal Qs[m] in the discharge determination unit period TPS.

[0061] 11, when the individual designation signal Sd[m] indicates a value "5" that designates the discharge section D[m] as the judgment preparation discharge section DJ in the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qs[m] so that the connection state designation signal Qs[m] is maintained at a high level in the control periods TT2, TT3, and TT4, and at a low level in the control periods TT1 and TT5. In this case, the switch Ws[m] is maintained in an on state in the control periods TT2, TT3, and TT4. Furthermore, when the individual designation signal Sd[m] indicates a value "6" that designates the discharge section D[m] as the discharge section DH to be judged in the unit period TP, the connection state designation circuit 310 sets the connection state designation signal Qs[m] so that the connection state designation signal Qs[m] is maintained at a high level in the control periods TT2, TT3, and TT4, and at a low level in the control periods TT1 and TT5. In this case, the switch Ws[m] is maintained in an on state in the control periods TT2, TT3, and TT4.

[0062] FIG. 12 is an explanatory diagram for explaining the connection state designation signal Qf, the connection state designation signal Q1, and the connection state designation signal Q2 in the discharge determination unit period TPS.

[0063] As illustrated in FIG. 12, the connection state designation circuit 310 sets the connection state designation signal Qf during the discharge determination unit period TPS so that the connection state designation signal Qf maintains a high level during control periods TT2, TT3, and TT4, and maintains a low level during control periods TT1 and TT5. In addition, the connection state designation circuit 310 sets the connection state designation signal Q1 so that, during the discharge determination unit period TPS, the connection state designation signal Q1 maintains a high level during control periods TT1, TT2, TT4, and TT5, and maintains a low level during control period TT3. In addition, the connection state designation circuit 310 sets the connection state designation signal Q2 so that, during the discharge determination unit period TPS, the connection state designation signal Q2 maintains a high level during control period TT3, and maintains a low level during control periods TT1, TT2, TT4, and TT5.

[0064] Fig. 13 is a timing chart illustrating various signals supplied to the head unit 3 and an example of the operation of the head unit 3 when the ejection state determination preparation process and the ejection state determination process are executed in the inkjet printer 1. Figs. 14 to 20 are circuit diagrams illustrating an example of the operation of the head unit 3 when the ejection state determination preparation process and the ejection state determination process similar to Fig. 13 are executed in the inkjet printer 1. Below, the example of the operation of the inkjet printer 1 shown in Figs. 13 to 20 may be simply referred to as a "determination operation example".

[0065] In this embodiment, when the inkjet printer 1 executes one ejection state determination process in one unit period TP(k+1), and when the inkjet printer 1 executes multiple ejection state determination processes in multiple consecutive unit periods TP(k+1) to TP(K), the inkjet printer 1 executes an ejection state determination preparation process in the unit period TP(k) immediately preceding the unit period TP(k+1) in which the one or multiple ejection state determination processes are executed for the first time. In the example of the determination operation shown in Figures 13 to 20, it is assumed that the inkjet printer 1 executes an ejection state determination preparation process in the unit period TP(k) with the ejection section D[m] as the determination preparation ejection section DJ, and executes an ejection state determination process in the unit period TP(k+1) with the ejection section D[m] as the determination target ejection section DH. 13 to 20, it is assumed that the discharge section D[m] selected by the control unit 2 as the determination preparation discharge section DJ in the unit period TP(k) and the discharge section D[m] selected as the determination target discharge section DH in the unit period TP(k+1) are the same discharge section D, but this is an example, and the present embodiment is not limited to such an aspect. For example, the control unit 2 may select a discharge section D different from the discharge section D selected as the determination preparation discharge section DJ in the unit period TP(k) as the determination target discharge section DH in the unit period TP(k+1). An example of the determination operation will now be described.

[0066] FIG. 14 is a diagram showing an example of the operation of the head unit 3 in a control period TT1 of a unit period TP(k) in which the ejection state determination preparation process is executed.

[0067] As illustrated in FIG. 13, in the control period TT1 of the unit period TP(k), the connection state designation signal Qc[m] maintains a high level, the connection state designation signal Qs[m] maintains a low level, the connection state designation signal Qf maintains a low level, the connection state designation signal Q1 maintains a high level, and the connection state designation signal Q2 maintains a low level. Therefore, as illustrated in FIG. 13 and FIG. 14, in the control period TT1 of the unit period TP(k), the switch Wc[m] maintains an on state, the switch Ws[m] maintains an off state, the switch Wf maintains an off state, the switch W1 maintains an on state, and the switch W2 maintains an off state. Therefore, in the control period TT1 of the unit period TP(k), the drive signal Com is supplied from the wiring Lc through the switch Wc[m] to the upper electrode Zu[m] of the piezoelectric element PZ[m]. As a result, the piezoelectric element PZ[m] is driven. In addition, during the control period TT1 of the unit period TP(k), the potential of the node Nd2 becomes the potential of the analog ground AGND, and the potential of the node Nd4 becomes the potential of the analog ground AGND.

[0068] FIG. 15 is a diagram showing an example of the operation of the head unit 3 in a control period TT2 of a unit period TP(k) in which the ejection state determination preparation process is executed.

[0069] As illustrated in Fig. 13, in the control period TT2 of the unit period TP(k), the connection state designation signal Qc[m] maintains a high level, the connection state designation signal Qs[m] maintains a high level, the connection state designation signal Qf maintains a high level, the connection state designation signal Q1 maintains a high level, and the connection state designation signal Q2 maintains a low level. Therefore, as illustrated in Fig. 13 and Fig. 15, in the control period TT2 of the unit period TP(k), the switch Wc[m] maintains an on state, the switch Ws[m] maintains an on state, the switch Wf maintains an on state, the switch W1 maintains an on state, and the switch W2 maintains an off state. Therefore, in the control period TT2 of the unit period TP(k), the driving signal Com of the potential VS2 is supplied from the wiring Lc through the switch Wc[m] to the upper electrode Zu[m] of the piezoelectric element PZ[m]. In addition, during the control period TT2 of the unit period TP(k), the line Lc supplies the drive signal Com at potential VS2 to the node Nd0 via the switch Wc[m] and the switch Ws[m], and the line Lc supplies the drive signal Com at potential VS2 to the node Nd0 via the switch Wf and the resistor Rf. As a result, during the control period TT2 of the unit period TP(k), the potential of the node Nd0 is set to potential VS2. 14 to 20, the switch Ws[m] may have a parasitic capacitance CPs. Specifically, for example, the capacitance CPs may be parasitic between the gate of the transistor provided in the switch Ws[m] and the wiring Ls. In this embodiment, during the control period TT2 of the unit period TP(k), the capacitance CPs can be charged by a current flowing from the wiring Lc to the capacitance CPs via the switch Wc[m] and the switch Ws[m], and a current flowing from the wiring Lc to the capacitance CPs via the switch Wf and the resistor Rf. During the control period TT2 of the unit period TP(k), the potential of the node Nd2 becomes the potential of the analog ground AGND, and the potential of the node Nd4 becomes the potential of the analog ground AGND.

[0070] FIG. 16 is a diagram showing an example of the operation of the head unit 3 in a control period TT3 of a unit period TP(k) in which the ejection state determination preparation process is executed.

[0071] As illustrated in FIG. 13, in the control period TT3 of the unit period TP(k), the connection state designation signal Qc[m] maintains a low level, the connection state designation signal Qs[m] maintains a high level, the connection state designation signal Qf maintains a high level, the connection state designation signal Q1 maintains a low level, and the connection state designation signal Q2 maintains a high level. Therefore, as illustrated in FIG. 13 and FIG. 16, in the control period TT3 of the unit period TP(k), the switch Wc[m] maintains an off state, the switch Ws[m] maintains an on state, the switch Wf maintains an on state, the switch W1 maintains an off state, and the switch W2 maintains an on state. Therefore, in the control period TT3 of the unit period TP(k), the potential of the node Nd0 is set to a potential based on the potential VS2 of the drive signal Com supplied from the wiring Lc via the switch Wf and the resistor Rf, and the potential of the detection potential signal VX[m] supplied from the upper electrode Zu[m] via the switch Ws[m]. During the control period TT3 of the unit period TP(k), the potential of the node Nd2 becomes a potential based on the potential of the detected potential signal VX[m], and the potential of the node Nd4 becomes a potential based on the potential of the detected potential signal VX[m]. In this case, during the control period TT3 of the unit period TP(k), a signal having a waveform according to the potential change of the detected potential signal VX[m] is output from the node Nd5. Note that, even during the control period TT3 of the unit period TP(k), the capacitance CPs can be charged by the current flowing from the wiring Lc to the capacitance CPs via the switches Wc[m] and Ws[m].

[0072] FIG. 17 is a diagram showing an example of the operation of the head unit 3 in a control period TT4 of a unit period TP(k) in which the ejection state determination preparation process is executed.

[0073] As illustrated in FIG. 13, in the control period TT4 of the unit period TP(k), the connection state designation signal Qc[m] maintains a low level, the connection state designation signal Qs[m] maintains a high level, the connection state designation signal Qf maintains a high level, the connection state designation signal Q1 maintains a high level, and the connection state designation signal Q2 maintains a low level. Therefore, as illustrated in FIG. 13 and FIG. 17, in the control period TT4 of the unit period TP(k), the switch Wc[m] maintains an off state, the switch Ws[m] maintains an on state, the switch Wf maintains an on state, the switch W1 maintains an on state, and the switch W2 maintains an off state. Therefore, in the control period TT4 of the unit period TP(k), the potential of the node Nd0 is set to a potential based on the potential VS2 of the drive signal Com supplied from the wiring Lc via the switch Wf and the resistor Rf, and the potential of the detection potential signal VX[m] supplied from the upper electrode Zu[m] via the switch Ws[m]. During the control period TT4 of the unit period TP(k), the potential of the node Nd2 becomes a potential based on the potential of the detected potential signal VX[m], and the potential of the node Nd4 becomes the potential of the analog ground AGND.

[0074] FIG. 18 is a diagram showing an example of the operation of the head unit 3 in a control period TT5 of the unit period TP(k) in which the ejection state determination preparation process is executed.

[0075] As illustrated in Fig. 13, in the control period TT5 of the unit period TP(k), the connection state designation signal Qc[m] maintains a low level, the connection state designation signal Qs[m] maintains a low level, the connection state designation signal Qf maintains a low level, the connection state designation signal Q1 maintains a high level, and the connection state designation signal Q2 maintains a low level. Therefore, as illustrated in Fig. 13 and Fig. 18, in the control period TT5 of the unit period TP(k), the switch Wc[m] maintains an off state, the switch Ws[m] maintains an off state, the switch Wf maintains an off state, the switch W1 maintains an on state, and the switch W2 maintains an off state. Therefore, in the control period TT5 of the unit period TP(k), the potential of the node Nd0 maintains the potential VS2. In addition, during the control period TT5 of the unit period TP(k), the potential of the node Nd2 becomes the potential of the analog ground AGND, and the potential of the node Nd4 becomes the potential of the analog ground AGND.

[0076] 13, the head unit 3 operates in the same manner as in the control period TT1 of the unit period TP(k+1) in which the discharge state determination process is executed, during the control period TT1 of the unit period TP(k+1) in which the discharge state determination preparation process is executed. Therefore, in the control period TT1 of the unit period TP(k+1), a drive signal Com is supplied from the wiring Lc to the upper electrode Zu[m] of the piezoelectric element PZ[m] via the switch Wc[m]. As a result, the piezoelectric element PZ[m] is driven, and vibration occurs in the discharge section D[m].

[0077] 13, in the control period TT2 of the unit period TP(k+1) in which the ejection state determination process is executed, the head unit 3 operates in the same manner as in the control period TT2 of the unit period TP(k). Therefore, in the control period TT2 of the unit period TP(k+1), the driving signal Com of the potential VS2 is supplied from the wiring Lc to the node Nd0 via the switches Wc[m] and Ws[m], and the driving signal Com of the potential VS2 is supplied from the wiring Lc to the node Nd0 via the switch Wf and the resistor Rf. The vibration generated in the discharge section D[m] during the control period TT1 of the unit period TP(k+1) remains in the control period TT2 of the unit period TP(k+1). The vibration remaining in the discharge section D[m] during the control period TT2 of the unit period TP(k+1) changes the potential of the upper electrode Zu[m] of the discharge section D[m]. During the control period TT2 of the unit period TP(k+1), the potential of the upper electrode Zu[m] of the discharge section D[m] is supplied to the node Nd0 as a detection potential signal VX[m] via the switch Ws[m].

[0078] As illustrated in FIG. 13, the head unit 3 operates in the same manner as in the control period TT3 of the unit period TP(k+1) in which the discharge state determination process is executed, during the control period TT3 of the unit period TP(k+1). Therefore, during the control period TT3 of the unit period TP(k+1), the potential of the node Nd0 is set to a potential based on the potential VS2 of the drive signal Com supplied from the wiring Lc via the switch Wf and the resistor Rf, and the potential of the detection potential signal VX[m] supplied from the upper electrode Zu[m] via the switch Ws[m]. In this case, the potential of the node Nd2 is a potential based on the potential of the detection potential signal VX[m], and the potential of the node Nd4 is a potential based on the potential of the detection potential signal VX[m]. Therefore, during the control period TT3 of the unit period TP(k+1), a signal having a waveform according to the potential change of the detection potential signal VX[m] is output as the detection signal SK[m] from the node Nd5. In other words, the waveform of the detection signal SK[m] generated based on the detection potential signal VX[m] detected from the ejection section D[m] during the control period TT3 of the unit period TP(k+1) represents the waveform of the vibration remaining in the ejection section D[m] during the control period TT3 of the unit period TP(k+1).

[0079] FIG. 19 is a diagram showing an example of the operation of the head unit 3 in a control period TT4 of the unit period TP(k+1) in which the ejection state determination process is executed.

[0080] As illustrated in FIG. 13, in the control period TT4 of the unit period TP(k+1), the connection state designation signal Qc[m] maintains a high level, the connection state designation signal Qs[m] maintains a high level, the connection state designation signal Qf maintains a high level, the connection state designation signal Q1 maintains a high level, and the connection state designation signal Q2 maintains a low level. Therefore, as illustrated in FIG. 13 and FIG. 19, in the control period TT4 of the unit period TP(k+1), the switch Wc[m] maintains an on state, the switch Ws[m] maintains an on state, the switch Wf maintains an on state, the switch W1 maintains an on state, and the switch W2 maintains an off state. Therefore, in the control period TT4 of the unit period TP(k+1), the potential of the node Nd0 is set to the potential VS2 of the drive signal Com supplied from the wiring Lc via the switch Wf and the resistor Rf. During the control period TT4 of the unit period TP(k+1), the potential of the node Nd2 becomes the potential of the analog ground AGND, and the potential of the node Nd4 becomes the potential of the analog ground AGND.

[0081] FIG. 20 is a diagram showing an example of the operation of the head unit 3 in a control period TT5 of the unit period TP(k+1) in which the ejection state determination process is executed.

[0082] 13, in the control period TT5 of the unit period TP(k+1), the connection state designation signal Qc[m] maintains a high level, the connection state designation signal Qs[m] maintains a low level, the connection state designation signal Qf maintains a low level, the connection state designation signal Q1 maintains a high level, and the connection state designation signal Q2 maintains a low level. Therefore, as illustrated in FIGS. 13 and 20, in the control period TT5 of the unit period TP(k+1), the switch Wc[m] maintains an on state, the switch Ws[m] maintains an off state, the switch Wf maintains an off state, the switch W1 maintains an on state, and the switch W2 maintains an off state.

[0083] As described above, in this embodiment, the control unit 2 controls the head unit 3 so that the switch Wc[m] maintains the ON state and the switch Ws[m] maintains the ON state during the control period TT2 of the unit period TP(k) in which the ejection state determination preparation process is executed. Therefore, according to this embodiment, it is possible to reliably charge the capacitance CPs during the control period TT2 of the unit period TP(k) in which the ejection state determination preparation process is executed, compared to a mode in which the switch Wc[m] or the switch Ws[m] maintains the OFF state during the control period TT2 of the unit period TP(k) in which the ejection state determination preparation process is executed.

[0084] In the judgment operation example illustrated in FIG. 13 and FIG. 20, the control period TT1 of the unit period TP(k) in which the discharge state judgment preparation process is executed may be referred to as period TA1. In addition, the control period TT2, the control period TT3, and the control period TT4 of the unit period TP(k) in which the discharge state judgment preparation process is executed may be referred to as period TA2. In addition, the control period TT5 of the unit period TP(k) in which the discharge state judgment preparation process is executed, and the control period TT1 of the unit period TP(k+1) in which the discharge state judgment process is executed may be referred to as period TA3. In addition, the control period TT2, the control period TT3, and the control period TT4 of the unit period TP(k+1) in which the discharge state judgment process is executed may be referred to as period TA4. 13, in the example of the determination operation, the switch Ws[m] maintains an OFF state in a period TA1, maintains an ON state in a period TA2, maintains an OFF state in a period TA3, and maintains an ON state in a period TA4. The determination unit 8 then determines the state of the piezoelectric element PZ[m] based on the detection signal SK[m] indicating the potential of the node Nd5 in a control period TT3 of the period TA4. In this embodiment, period TA1 is an example of a "first period", period TA2 is an example of a "second period", period TA3 is an example of a "third period", and period TA4 is an example of a "fourth period".

[0085] <<4. Operation of the Judgment Unit>> Hereinafter, the operation of the decision unit 8 will be described with reference to FIG.

[0086] Generally, the vibration remaining in the discharge section D[m] has a natural vibration period determined by the shape of the nozzle N of the discharge section D[m], the weight of the ink filled in the cavity 322 of the discharge section D[m], the viscosity of the ink filled in the cavity 322 of the discharge section D[m], and the like. In general, when an abnormal discharge occurs due to air bubbles being mixed in the cavity 322 of the discharge section D[m], the period of the vibration remaining in the discharge section D[m] becomes shorter than when the discharge state is normal. In general, when an abnormal discharge occurs due to foreign matter such as paper powder adhering near the nozzle N of the discharge section D[m], the period of the vibration remaining in the discharge section D[m] becomes longer than when the discharge state is normal. In general, when an abnormal discharge occurs due to the viscosity of the ink in the cavity 322 of the discharge section D[m], the period of the vibration remaining in the discharge section D[m] becomes longer than when the discharge state is normal. In this way, the period of the vibration remaining in the ejection section D[m] varies depending on the ink ejection state of the ejection section D[m]. Therefore, the ink ejection state of the ejection section D[m] can be determined based on the period of the vibration remaining in the ejection section D[m]. Generally, when abnormal ejection occurs due to a breakdown of the piezoelectric element PZ[m] of the ejection section D[m], the amplitude of the vibration remaining in the ejection section D[m] is smaller than when the ejection state is normal. Therefore, the ejection state of the ink in the ejection section D[m] can be determined based on the amplitude of the vibration remaining in the ejection section D[m].

[0087] As described above, the waveform of the detection signal SK[m] indicates the waveform of the vibration remaining in the discharge section D[m] driven as the discharge section DH to be determined. That is, the period NTC[m] of the waveform of the detection signal SK[m] is the period of the vibration remaining in the discharge section D[m] driven as the discharge section DH to be determined. Therefore, based on the period NTC[m] of the waveform of the detection signal SK[m], the ink discharge state of the discharge section D[m] driven as the discharge section DH to be determined can be determined. In addition, the amplitude VM[m] of the waveform of the detection signal SK[m] is an amplitude corresponding to the amplitude of the vibration remaining in the discharge section D[m] driven as the discharge section DH to be determined. Therefore, based on the amplitude VM[m] of the waveform of the detection signal SK[m], the ink discharge state of the discharge section D[m] driven as the discharge section DH to be determined can be determined.

[0088] In this embodiment, the determination unit 8 identifies the period NTC[m] and amplitude VM[m] of the waveform of the detection signal SK[m] based on the detection signal SK[m]. Then, in this embodiment, the determination unit 8 compares the period NTC[m] with one or both of the thresholds Tth-L and Tth-H, and compares the amplitude VM[m] with the threshold Vth, as illustrated in Fig. 21, to determine the ink ejection state of the ejection section D[m] driven as the ejection section DH to be determined, and generates ejection state determination information JH[m] indicating the result of the determination. Here, the threshold value Tth-L is an estimated value of the boundary between the period NTC[m] of vibration generated in the discharge section D[m] when the discharge state of the discharge section D[m] is normal and the period NTC[m] of vibration generated in the discharge section D[m] when an air bubble is mixed in the cavity 322 of the discharge section D[m]. The threshold value Tth-H is a value larger than the threshold value Tth-L, and is an estimated value of the boundary between the period NTC[m] of vibration generated in the discharge section D[m] when the discharge state of the discharge section D[m] is normal and the period NTC[m] of vibration generated in the discharge section D[m] when a foreign object adheres near the nozzle N of the discharge section D[m] or when the ink in the cavity 322 of the discharge section D[m] becomes viscous. In addition, the threshold value Vth is an estimated boundary between the amplitude VM[m] of the vibration generated in the discharge section D[m] when the discharge state of the discharge section D[m] is normal, and the amplitude VM[m] of the vibration generated in the discharge section D[m] when the piezoelectric element PZ[m] of the discharge section D[m] fails.

[0089] As illustrated in FIG. 21, when the amplitude VM[m] satisfies "Vth ≤ VM[m]" and the period NTC[m] satisfies "Tth-L ≤ NTC[m] ≤ Tth-H", the determination unit 8 determines that the ink ejection state in the ejection unit D[m] is normal, and sets the value "1" indicating that the ink ejection state in the ejection unit D[m] is normal for the ejection state determination information JH[m]. Further, when the amplitude VM[m] satisfies "Vth ≤ VM[m]" and the period NTC[m] satisfies "NTC[m] < Tth-L", the determination unit 8 determines that ejection abnormality has occurred because air bubbles have entered the cavity 322 of the ejection unit D[m], and sets the value "2" indicating that ejection abnormality due to air bubbles has occurred in the ejection unit D[m] for the ejection state determination information JH[m]. Further, when the amplitude VM[m] satisfies "Vth ≤ VM[m]" and the period NTC[m] satisfies "Tth-H < NTC[m]", the determination unit 8 determines that ejection abnormality has occurred because foreign matter such as paper dust has adhered near the nozzle N of the ejection unit D[m], or because the ink in the cavity 322 of the ejection unit D[m] has thickened, and sets the value "3" indicating that ejection abnormality due to foreign matter or thickening has occurred in the ejection unit D[m] for the ejection state determination information JH[m]. Further, when the amplitude VM[m] satisfies "VM[m] < Vth", the determination unit 8 determines that ejection abnormality has occurred because the piezoelectric element PZ[m] of the ejection unit D[m] has failed, and sets the value "4" indicating that ejection abnormality due to failure has occurred in the ejection unit D[m] for the ejection state determination information JH[m]. As described above, the determination unit 8 generates the ejection state determination information JH[m] based on the period NTC[m] and the amplitude VM[m] of the waveform of the detection signal SK[m].

[0090] <<5. Reference Example>> Hereinafter, with reference to FIG. 22, the operation of the head unit 3 according to the reference example will be described.

[0091] FIG. 22 is a timing chart for explaining the operation of the head unit 3 according to the reference example.

[0092] As shown in Figure 22, the reference example differs from the judgment operation example illustrated in Figure 13 in that during the unit period TP(k) in which the ejection state judgment preparation process is executed, the connection state designation signal Qc[m] and the connection state designation signal Qs[m] maintain a low level.

[0093] In the reference example, during the unit period TP(k) in which the ejection state determination preparation process is executed, in control periods TT2, TT3, and TT4, the capacitance CPs is charged by a current flowing from the wiring Lc through the switch Wf and the resistor Rf to the capacitance CPs. However, in the reference example, since there is a resistor Rf on the path from the switch Wf to the capacitance CPs, there are cases where the charging of the capacitance CPs is not completed in the unit period TP(k) in which the discharge state determination preparation process is executed. In the reference example, if the charging of the capacitance CPs is not completed in the unit period TP(k) in which the discharge state determination preparation process is executed, an inrush current for charging the capacitance CPs occurs in the control period TT2 of the unit period TP(k+1) in which the discharge state determination process is executed, and noise caused by the inrush current may be superimposed on the detection potential signal VX[m] and the detection signal SK[m]. On the other hand, in the reference example, in order to complete the charging of the capacitance CPs, it is necessary to repeat the discharge state determination preparation process multiple times in multiple unit periods TP, and there is a possibility that a problem will occur in which the start of the discharge state determination process is delayed. Furthermore, in the reference example, if charging of the capacity CPs is not completed during the unit period TP(k) in which the ejection state determination preparation process is executed, at the start of the control period TT3 of the unit period TP(k+1) in which the ejection state determination process is executed, the potential of the node Nd0 is different from the potential VS2, so that an inrush current occurs due to the switching of the switch W2, and noise caused by the inrush current may be superimposed on the detection potential signal VX[m] and the detection signal SK[m].

[0094] In contrast, according to the present embodiment, the capacitance CPs is charged by a current flowing from the wiring Lc through the switch Wc[m] and the switch Ws[m] to the capacitance CPs, and a current flowing from the wiring Lc through the switch Wf and the resistor Rf to the capacitance CPs. Therefore, according to the present embodiment, it is possible to charge the capacitance CPs more quickly than in the reference example. That is, according to the present embodiment, it is possible to reduce noise caused by the inrush current for charging the capacitance CPs and to reduce noise caused by the inrush current accompanying the switching of the switch W2, compared to the reference example. Therefore, according to the present embodiment, it is possible to reduce noise superimposed on the detection potential signal VX[m] and the detection signal SK[m], compared to the reference example. As a result, according to the present embodiment, it is possible to more accurately determine the ink ejection state in the ejection section D[m], compared to the reference example.

[0095] <<6. Summary of the embodiment>> As described above, the ink jet printer 1 according to this embodiment includes an upper electrode Zu[m], a piezoelectric element PZ[m] that is driven by a drive signal Com supplied to the upper electrode Zu[m] via a wiring Lc, a switch Wc[m] that switches whether or not to electrically connect the wiring Lc and the upper electrode Zu[m], a detection circuit 33 that detects, via the wiring Ls, vibrations generated in the piezoelectric element PZ[m] driven by the drive signal Com as a change in potential of the upper electrode Zu[m], and a switch Wc[m] that switches whether or not to electrically connect the wiring Ls and the upper electrode Zu[m]. The control circuit includes a switch Ws[m] and a judgment unit 8 that judges the state of the piezoelectric element PZ[m], wherein the switch Ws[m] maintains an off state during a period TA1, maintains an on state during a period TA2 following the period TA1, maintains an off state during a period TA3 following the period TA2, and maintains an on state during a period TA4 following the period TA3, and the judgment unit 8 judges the state of the piezoelectric element PZ[m] based on a detection signal SK[m] that indicates the detection result by the detection circuit 33 during a control period TT3 of the period TA4. That is, according to this embodiment, in the period TA2, the switch Ws[m] is turned on, and therefore the capacitance CPs parasitic on the switch Ws[m] can be charged via the switch Ws[m] before the period TA4 in which detection is performed by the detection circuit 33. Therefore, according to this embodiment, in the period TA4 in which detection is performed by the detection circuit 33, it is possible to suppress the occurrence of an inrush current for charging the capacitance CPs, and it is possible to improve the detection accuracy of the detection circuit 33 in detecting the potential change of the upper electrode Zu[m].

[0096] Furthermore, in the inkjet printer 1 according to this embodiment, the switch Wc[m] is characterized in that it maintains the on state during the control period TT2 of the period TA2. Therefore, according to the present embodiment, in the period TA2, it becomes possible to charge the capacitance CPs by the driving signal Com via the line Lc, the switch Wc[m], and the switch Ws[m].

[0097] Furthermore, in the ink jet printer 1 according to this embodiment, the switch Wc[m] is characterized in that it maintains the on state during the control period TT1 within the period TA3. Therefore, according to this embodiment, the piezoelectric element PZ[m] can be driven by the drive signal Com before the period TA4.

[0098] Furthermore, the inkjet printer 1 according to this embodiment is characterized in that it includes a switch Wf that switches whether or not the wiring Lc and the wiring Ls are electrically connected, and a resistor Rf that is electrically connected between the switch Wf and the wiring Ls, and that the switch Wf maintains its on state during period TA2, and maintains its on state during period TA4. Therefore, according to the present embodiment, the capacitance CPs parasitic on the switch Ws[m] can be charged via the switch Wf before the period TA4 during which the detection by the detection circuit 33 is performed.

[0099] Further, in the inkjet printer 1 according to the present embodiment, the switch Wf maintains an off state in the period TA1 and maintains an off state in the period TA3, which is characterized in that. Therefore, according to the present embodiment, it is possible to prevent the detection circuit 33 from being affected by the potential change of the drive signal Com.

[0100] Further, in the inkjet printer 1 according to the present embodiment, in the periods TA2 and TA4, the drive signal Com maintains the potential VS2, which is characterized in that. Therefore, according to the present embodiment, in the period TA2, the potential of the wiring Ls can be set to the potential VS2. Further, according to the present embodiment, in the period TA4, the detection circuit 33 can accurately detect the potential change of the upper electrode Zu[m].

[0101] <<B. Modification 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 that does not conflict with each other. In the modification 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 used, and the detailed description of each is appropriately omitted.

[0102] <<Modification Example 1>> In the above-described embodiment, it is assumed that the unit period TP in which the printing process is executed and the unit period TP in which the ejection state determination process or the ejection state determination preparation process is executed are different periods, but the present invention is not limited to such a mode. For example, in the unit period TP in which the printing process is executed, the ejection state determination process or the ejection state determination preparation process may be executed. In this case, as a signal line for transmitting a drive signal Com having a waveform PS, a signal line for transmitting a drive signal Com having a waveform PS may be provided separately from the signal line for transmitting the drive signal Com having the waveforms PP1 and PP2 to the head unit 3 from the drive signal generation unit 4.

[0103] <<Modification Example 2>> In the above-described embodiment and variant example 1, the inkjet printer 1 is a serial printer, but the present invention is not limited to this. The inkjet printer 1 may be a so-called line printer in which the multiple nozzles N in the head unit 3 are arranged to extend wider than the width of the recording paper P.

[0104] <<Variation 3>> In the above-described embodiment and modified examples 1 and 2, an inkjet printer 1 having a piezoelectric element PZ[m], which is an example of a "capacitive load", has been exemplified as a "drive device", but the present invention is not limited to this embodiment. The present invention can be applied to any "drive device" that has a "capacitive load". For example, an audio device such as a speaker, or an automobile injector, can be used as a "drive device" according to the present invention. [Explanation of symbols]

[0105] 1...inkjet printer, 2...control unit, 3...head unit, 4...drive signal generating unit, 7...transport unit, 8...judgment unit, 31...supply circuit, 32...recording head, 33...detection circuit, 310...connection state designation circuit, D...ejection portion, Lc...wiring, Ls...wiring, PZ[m]...piezoelectric element, Rf...resistance, Wc[m]...switch, Ws[m]...switch, Wf...switch, Zu[m]...upper electrode.

Claims

1. a piezoelectric element including a drive electrode and driven by a drive signal supplied to the drive electrode via a first wiring; a first switch that switches whether or not the first wiring and the drive electrode are electrically connected; a detection circuit that detects a vibration generated in the piezoelectric element driven by the drive signal as a potential change of the drive electrode via a second wiring; a second switch that switches whether or not the second wiring and the drive electrode are electrically connected; A determination circuit for determining a state of the piezoelectric element; Equipped with The second switch is In the first period, the off state is maintained, In a second period following the first period, the ON state is maintained; In a third period following the second period, the off state is maintained; In a fourth period following the third period, the on state is maintained, The determination circuit includes: During at least a part of the fourth period, Based on the detection result by the detection circuit, Determining a state of the piezoelectric element; The first switch is maintaining an on state during at least a portion of the second period; A drive device comprising:

2. The first switch is maintain an on state during at least a portion of the third period; 2. The drive device according to claim 1, characterized in that:

3. a piezoelectric element including a drive electrode and driven by a drive signal supplied to the drive electrode via a first wiring; a first switch that switches whether or not the first wiring and the drive electrode are electrically connected; a detection circuit that detects a vibration generated in the piezoelectric element driven by the drive signal as a potential change of the drive electrode via a second wiring; a second switch that switches whether or not the second wiring and the drive electrode are electrically connected; A determination circuit for determining a state of the piezoelectric element; a third switch that switches between electrically connecting or not connecting the first wiring and the second wiring; a first resistor electrically connected between the third switch and the second wiring; Equipped with The second switch is In the first period, the off state is maintained, In a second period following the first period, the ON state is maintained; In a third period following the second period, the off state is maintained; In a fourth period following the third period, the on state is maintained, The determination circuit includes: During at least a part of the fourth period, Based on the detection result by the detection circuit, Determining a state of the piezoelectric element; The third switch is In the second period, the ON state is maintained, In the fourth period, the ON state is maintained. A drive device comprising:

4. The third switch is In the first period, the off state is maintained, In the third period, the off state is maintained.

4. The drive device according to claim 3, characterized in that

5. In the second period and the fourth period, The drive signal maintains a constant potential.

5. A drive device according to claim 1, wherein the drive device is a drive unit.

6. a piezoelectric element including a drive electrode and driven by a drive signal supplied to the drive electrode via a first wiring; a first switch that switches whether or not the first wiring and the drive electrode are electrically connected; a detection circuit that detects a vibration generated in the piezoelectric element driven by the drive signal as a potential change of the drive electrode via a second wiring; a second switch that switches whether or not the second wiring and the drive electrode are electrically connected; A method for controlling a drive device comprising: In the first period, the off state is maintained, In a second period following the first period, the ON state is maintained; In a third period following the second period, the off state is maintained; In a fourth period following the third period, the ON state is maintained. Controlling the second switch; To maintain an on-state during at least a portion of the second period, Controlling the first switch; During at least a part of the fourth period, Based on the detection result by the detection circuit, determining a state of the piezoelectric element; A method for controlling a drive device, comprising:

7. a piezoelectric element including a drive electrode and driven by a drive signal supplied to the drive electrode via a first wiring; a first switch that switches whether or not the first wiring and the drive electrode are electrically connected; a detection circuit that detects a vibration generated in the piezoelectric element driven by the drive signal as a potential change of the drive electrode via a second wiring; a second switch that switches whether or not the second wiring and the drive electrode are electrically connected; a third switch that switches between electrically connecting or not connecting the first wiring and the second wiring; a first resistor electrically connected between the third switch and the second wiring; A method for controlling a drive device comprising: In the first period, the off state is maintained, In a second period following the first period, the ON state is maintained; In a third period following the second period, the off state is maintained; In a fourth period following the third period, the ON state is maintained. Controlling the second switch; In the second period, the ON state is maintained, In the fourth period, to maintain the ON state, Controlling the third switch; During at least a part of the fourth period, Based on the detection result by the detection circuit, determining a state of the piezoelectric element; A method for controlling a drive device, comprising:

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