Liquid discharge device, liquid discharge head, and control method of liquid discharge head

Abstract

To shorten a time length of a unit period, which is a cycle for driving a discharge part.SOLUTION: A liquid discharge head includes: a discharge part for discharging liquid according to supply of a driving signal; a supply part for supplying the driving signal to the discharge part; and a detection part for detecting vibration in the discharge part. The supply part supplies an inspection driving signal having an inspection waveform of the driving signals to the discharge part in a first unit period that is started by a first latch pulse of a plurality of latch pulses included in a latch signal supplied to the supply part, and is ended by a second latch pulse provided next to the first latch pulse of the plurality of latch pulses. The detection part detects vibration remaining in the discharge part in a second unit period that is started by the second latch pulse and is ended by a third latch pulse provided next to the second latch pulse of the plurality of latch pulses.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a liquid ejection apparatus, a liquid ejection head, and a method for controlling a liquid ejection head. [Background technology]

[0002] A liquid ejection device such as an inkjet printer drives an ejection section of a liquid ejection head in each of a plurality of unit periods defined by a latch signal, thereby ejecting liquid such as ink filled in the ejection section in each of the plurality of unit periods, thereby forming an image on a medium. However, in a liquid ejection device, an ejection abnormality may occur in which the liquid cannot be ejected normally from the ejection section. Therefore, a technique for inspecting the ejection state of the ejection section has been proposed. For example, Patent Document 1 discloses a technique for inspecting the ejection state of the ejection section based on a detection signal indicating vibration remaining in the ejection section after the ejection section is driven by a drive signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-044771 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to conventional technology, when inspecting the ejection state of the ejection section, it was necessary to set the unit period, which is the cycle for driving the ejection section, to a sufficiently long length in order to both drive the ejection section using a drive signal and detect any vibration remaining in the driven ejection section. [Means for solving the problem]

[0005] In order to solve the above problems, the liquid ejection head of the present invention comprises an ejection section which ejects liquid in response to the supply of a drive signal, a supply section which supplies the drive signal to the ejection section, and a detection section which detects vibrations in the ejection section, wherein the supply section supplies a test drive signal having a test waveform from the drive signal to the ejection section during a first unit period which is started by a first latch pulse from among a plurality of latch pulses contained in a latch signal supplied to the supply section and which ends by a second latch pulse from among the plurality of latch pulses which follows the first latch pulse, and the detection section detects vibrations remaining in the ejection section during a second unit period which is started by the second latch pulse and which ends by a third latch pulse from among the plurality of latch pulses which follows the second latch pulse.

[0006] Furthermore, the liquid ejection device according to the present invention comprises an ejection section which ejects liquid in response to the supply of a drive signal, a supply section which supplies the drive signal to the ejection section, and a detection section which detects vibrations in the ejection section, wherein the supply section supplies a test drive signal having a test waveform from the drive signal to the ejection section during a first unit period which is started by a first latch pulse from among a plurality of latch pulses included in a latch signal supplied to the supply section and which ends by a second latch pulse from among the plurality of latch pulses which follows the first latch pulse, and the detection section detects vibrations remaining in the ejection section during a second unit period which is started by the second latch pulse and which ends by a third latch pulse from among the plurality of latch pulses which follows the second latch pulse.

[0007] Furthermore, a control method for a liquid ejection head according to the present invention is a control method for a liquid ejection head including an ejection section that ejects liquid in response to the supply of a drive signal, a supply section that supplies the drive signal to the ejection section, and a detection section that detects vibrations in the ejection section, and is characterized in that the control method controls the liquid ejection head so that the supply section supplies a test drive signal having a test waveform among the drive signals to the ejection section during a first unit period that is started by a first latch pulse among a plurality of latch pulses included in a latch signal supplied to the supply section and ends by a second latch pulse among the plurality of latch pulses that follows the first latch pulse, and controls the liquid ejection head so that the detection section detects vibrations remaining in the ejection section during a second unit period that is started by the second latch pulse and ends by a third latch pulse among the plurality of latch pulses that follows the second latch pulse. [Brief description of the drawings]

[0008] [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 block diagram showing an example of the configuration of a head unit 3. FIG. [Diagram 5] 4 is a timing chart for explaining an example of a signal supplied to the head unit 3. [Figure 6] 4 is a block diagram showing an example of the configuration of a connection state designation circuit 34. FIG. [Figure 7] FIG. 11 is an explanatory diagram illustrating an example of the operation of a decoder DC[m]. [Figure 8] 11 is a timing chart for explaining an example of a supply drive signal Vin[m]. [Figure 9]It is a timing chart for explaining an example of the detection signal SK[m]. [Figure 10] It is an explanatory diagram for explaining an example of the operation of the inspection unit 5. [Figure 11] It is a timing chart for explaining an example of the signal supplied to the head unit 3 according to the reference example. [Figure 12] It is an explanatory diagram for explaining an example of the operation of the decoder DC[m] according to the reference example. [Figure 13] It is a timing chart for explaining an example of the supply drive signal Vin-W[m] according to the reference example. [Figure 14] It is a block diagram showing an example of the configuration of the head unit 3Z according to Modification 1 of the present invention. [Figure 15] It is a timing chart for explaining an example of the signal supplied to the head unit 3Z according to Modification 1. [Figure 16] It is a block diagram showing an example of the configuration of the connection state specifying circuit 34Z according to Modification 1. [Figure 17] It is an explanatory diagram for explaining an example of the operation of the decoder DCz[m] according to Modification 1. [Figure 18] It is a timing chart for explaining an example of the supply drive signal Vin-Z[m] according to Modification 1.

Best Mode for Carrying Out the Invention

[0009] 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. Further, 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 otherwise specified in the following description to limit the present invention.

[0010] <<A. Embodiment>> In this embodiment, the liquid ejection device will be described by taking as an example an inkjet printer that ejects ink to form an image on recording paper PP.

[0011] <<1. Overview of Inkjet Printers>> An example of the configuration of an inkjet printer 1 according to this embodiment will be described below with reference to FIGS.

[0012] FIG. 1 is a functional block diagram showing an example of the configuration of an inkjet printer 1.

[0013] 1, print data Img indicating an image to be formed by the inkjet printer 1 is supplied from a host computer such as a personal computer or digital camera to the inkjet printer 1. The inkjet printer 1 executes a printing process to form, on recording paper PP, an image indicated by the print data Img supplied from the host computer.

[0014] 1, the inkjet printer 1 includes a control unit 2 that controls each part of the inkjet printer 1, a head unit 3 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, an inspection unit 5 that inspects the ink ejection state in the ejection section D, a storage unit 6 that stores various information, and a transport unit 7 that changes the relative position of recording paper PP with respect to the head unit 3. Note that the inkjet printer 1 is an example of a "liquid ejection device," ink is an example of a "liquid," and the head unit 3 is an example of a "liquid ejection head."

[0015] 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 that correspond one-to-one with the one or more head units 3, and one or more inspection units 5 that correspond one-to-one with the one or more head units 3. Specifically, in this embodiment, it is assumed that the inkjet printer 1 includes four head units 3, four drive signal generating units 4 that correspond one-to-one with the four head units 3, and four inspection units 5 that correspond one-to-one with the four head units 3. However, for convenience of explanation, the following description focuses on one head unit 3 of the four head units 3, one drive signal generating unit 4 provided to correspond to one head unit 3 of the four drive signal generating units 4, and one inspection unit 5 provided to correspond to one head unit 3 of the four inspection units 5, as shown in FIG.

[0016] The control unit 2 is configured to include one or more central processing units (CPUs). However, the control unit 2 may include a programmable logic device such as a field-programmable gate array (FPGA) instead of or in addition to a CPU. The control unit 2 also includes a memory. The memory is configured to include one or both of a volatile memory such as a random access memory (RAM) and a non-volatile memory such as a read only memory (ROM), an electrically erasable programmable read-only memory (EEPROM) or a programmable ROM (PROM).

[0017] 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 specification signal SI and a waveform specification signal dCom.

[0018] Here, the waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com. Moreover, the drive signal Com is an analog signal for driving the discharge section D. In this embodiment, it is assumed that the drive signal Com includes drive signals Com-A, Com-B, and Com-C. In this embodiment, the drive signal Com-B is an example of a "test drive signal," and the drive signal Com-C is an example of a "detection drive signal."

[0019] Moreover, the designation signal SI is a digital signal that designates the type of operation of the ejection section D. Specifically, the designation signal SI designates whether or not to supply the drive signal Com to the ejection section D, thereby designating the type of operation of the ejection section D, such as whether or not to eject ink from the ejection section D.

[0020] When a printing process is performed, the control unit 2 generates signals, such as a designation signal SI, for controlling the head unit 3 based on the print data Img. When a printing process is 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 performed, the control unit 2 also generates a signal 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 PP with respect to the head unit 3, while adjusting the presence or absence of ink ejection from the ejection unit D and the timing of ink ejection, and controls each part of the inkjet printer 1 so that an image corresponding to the print data Img is formed on the recording paper PP.

[0021] 1, the head unit 3 includes a supply circuit 31, a recording head 32, and a detection circuit 33. The supply circuit 31 is an example of a "supply section," and the detection circuit 33 is an example of a "detection section."

[0022] 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.

[0023] The supply circuit 31 switches whether to supply the drive signal Com to the discharge section D[m] based on the designation signal SI. Hereinafter, of the drive signals Com, the drive signal Com supplied to the discharge section D[m] may be referred to as a supply drive signal Vin[m]. Further, the supply circuit 31 switches whether to supply the detection potential signal VX[m] to the detection circuit 33 based on the designation signal SI. Here, the detection potential signal VX[m] is a signal indicating the potential of the upper electrode Zu[m] provided on the piezoelectric element PZ[m] of the discharge section D[m]. Hereinafter, when the detection potential signal VX[m] is supplied from the discharge section D[m] to the detection circuit 33, the discharge section D[m] may be referred to as the discharge section DS to be inspected. The piezoelectric element PZ[m] and the upper electrode Zu[m] will be described later with reference to FIG. 3.

[0024] The detection circuit 33 generates a detection signal SK[m] based on the detection potential signal VX[m] supplied from the discharge portion D[m] that is set as the inspection target discharge portion DS via the supply circuit 31. Specifically, the detection circuit 33 generates the detection signal SK[m] by amplifying the detection potential signal VX[m] and removing noise components, for example.

[0025] The inspection unit 5 inspects whether the ink ejection state in the ejection section DS to be inspected is normal or not based on the detection signal SK[m]. In other words, the inspection unit 5 inspects whether the ejection section DS to be inspected is in a state where no ejection abnormality occurs based on the detection signal SK[m]. The inspection unit 5 then generates inspection result information SH[m] indicating the result of the inspection. Here, the inspection result information SH[m] is information indicating whether an ejection abnormality occurs in the ejection section D[m] selected as the ejection section DS to be inspected. Furthermore, the ejection abnormality is a general term for a state in which ink cannot be ejected normally 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 amount of ink ejected 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.

[0026] Hereinafter, the process of driving the ejection section D[m] as the ejection section DS to inspect the ink ejection state of the ejection section D[m] is referred to as the ejection state inspection process. Also, below, the process of driving the ejection section D[m] as the ejection section DS to be inspected in the ejection state inspection process is referred to as the inspection target drive process. And below, the ejection section D[m] that is the inspection target ejection section DS to be the object of the ejection state inspection process and is the object of the inspection target drive process is referred to as the inspection drive ejection section DS1. In the following, the process of detecting the detected potential signal VX[m] from the discharge section D[m] driven as the discharge section DS to be inspected in the discharge state inspection process is referred to as the residual vibration detection process. In the following, the discharge section D[m] to be inspected in the discharge state inspection process and the discharge section D[m] to be subjected to the residual vibration detection process is referred to as the vibration detection discharge section DS2.

[0027] When the inspection target drive process is executed, the control unit 2 generates a signal such as a designation signal SI for controlling the head unit 3. Also, when the inspection target drive process is executed, the control unit 2 generates a signal such as a waveform designation signal dCom for controlling the drive signal generating unit 4. As a result, the control unit 2 drives the ejection section D[m] as an inspection drive ejection section DS1 in the inspection target drive process.

[0028] When the residual vibration detection process is executed, the control unit 2 generates a designation signal SI to control the head unit 3 so that the detection potential signal VX[m] corresponding to the ejection section D[m] driven as the inspection driving ejection section DS1 in the inspection target driving process is supplied to the detection circuit 33. When the residual vibration detection process is executed, the control unit 2 generates a designation signal SI to drive the ejection section D[m] driven as the inspection driving ejection section DS1 in the inspection target driving process as the vibration detection ejection section DS2. When the residual vibration detection process is executed, the detection circuit 33 generates a detection signal SK[m] based on the detection potential signal VX[m] detected from the ejection section D[m] driven as the vibration detection ejection section DS2.

[0029] FIG. 2 is a perspective view showing an example of a schematic internal structure of the inkjet printer 1. As shown in FIG.

[0030] 2, this embodiment assumes that the inkjet printer 1 is a serial printer. Specifically, when executing a printing process, the inkjet printer 1 transports the recording paper PP in the X1 direction, while reciprocating the head unit 3 in the Y1 direction that intersects with the X1 direction, and in the Y2 direction that is the opposite direction to the Y1 direction, to eject ink from the ejection section D[m], thereby forming dots Dt on the recording paper PP according to the print data Img.

[0031] Hereinafter, the X1 direction and its opposite X2 direction will be collectively referred to as the "X-axis direction", the Y1 direction intersecting the X-axis direction and its opposite 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 Z2 direction will be collectively referred to as the "Z-axis direction". In this embodiment, as an example, a description will be given assuming that the X-axis direction, the Y-axis direction, and the Z-axis direction are mutually orthogonal. However, the present invention is not limited to this aspect. It is sufficient that the X-axis direction, the Y-axis direction, and the Z-axis direction intersect with each other. In this embodiment, the Z1 direction is the direction in which ink is ejected from the ejection section D[m].

[0032] 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 four head units 3 mounted thereon.

[0033] 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 that the inkjet printer 1 includes four head units 3 in one-to-one correspondence with the four ink cartridges 120, as described above. 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. As a result, each ejection section D[m] is filled with the supplied ink, and the ink filled in the ejection section D[m] can be ejected from the nozzle N provided in the ejection section D[m]. Note that the ink cartridges 120 may be provided outside the carriage 110.

[0034] As described above, the inkjet printer 1 according to this embodiment also includes a transport unit 7. As shown in Fig. 2, 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 PP, and a platen 75 provided in the Z1 direction 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 the medium transport mechanism 73 to transport 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.

[0035] 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].

[0036] As shown in FIG. 3, the ejection section D[m] includes a piezoelectric element PZ[m], a cavity CV filled with ink, a nozzle N communicating with the cavity CV, and a vibration plate 321. The ejection section D[m] ejects ink in the cavity CV from the nozzle N by driving the piezoelectric element PZ[m] with a supply drive signal Vin[m]. The cavity CV 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 CV 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 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 direction or the Z2 direction according to the applied voltage, and as a result, the piezoelectric element PZ[m] vibrates. The lower electrode Zd[m] is 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 CV and the pressure within the cavity CV, causing the ink filled within the cavity CV to be ejected from the nozzle N.

[0037] <<2. Head unit overview>> Hereinafter, an overview of the head unit 3 will be described with reference to FIGS.

[0038] FIG. 4 is a block diagram showing an example of the configuration of the head unit 3. As shown in FIG.

[0039] 4, the head unit 3 includes a supply circuit 31, a recording head 32, and a detection circuit 33. The head unit 3 also includes a wiring La to which the drive signal Com-A is supplied from the drive signal generating unit 4, a wiring Lb to which the drive signal Com-B is supplied from the drive signal generating unit 4, a wiring Lc to which the drive signal Com-C is supplied from the drive signal generating unit 4, and a wiring Ls for supplying the detection potential signal VX[m] to the detection circuit 33.

[0040] The supply circuit 31 includes M switches Wa[1] to Wa[M] in one-to-one correspondence with the M discharge sections D[1] to D[M], M switches Wb[1] to Wb[M] in one-to-one correspondence with the M discharge sections D[1] to D[M], M switches Wc[1] to Wc[M] in one-to-one correspondence with the M discharge sections D[1] to D[M], M switches Ws[1] to Ws[M] in one-to-one correspondence with the M discharge sections D[1] to D[M], and a connection state designation circuit 34 that designates the connection state of each switch.

[0041] Based on the designation signal SI, latch signal LAT, and period designation signal Tsig supplied from the control unit 2, the connection state designation circuit 34 generates a connection state designation signal Qa[m] that designates the on / off state of switch Wa[m], a connection state designation signal Qb[m] that designates the on / off state of switch Wb[m], a connection state designation signal Qc[m] that designates the on / off state of switch Wc[m], and a connection state designation signal Qs[m] that designates the on / off state of switch Ws[m].

[0042] The switch Wa[m] switches between electrical continuity and non-conduction between the wiring La and the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designation signal Qa[m]. In this embodiment, the switch Wa[m] is turned on when the connection state designation signal Qa[m] is at a high level, and turned off when the connection state designation signal Qa[m] is at a low level. When the switch Wa[m] is turned on, the drive signal Com-A supplied to the wiring La is supplied to the upper electrode Zu[m] of the discharge section D[m] as the supply drive signal Vin[m]. The switch Wb[m] switches between electrical continuity and non-conduction between the wiring Lb and the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designation signal Qb[m]. In this embodiment, the switch Wb[m] is turned on when the connection state designation signal Qb[m] is at a high level, and turned off when the connection state designation signal Qb[m] is at a low level. When the switch Wb[m] is turned on, the drive signal Com-B supplied to the wiring Lb 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] switches between electrical continuity and non-conduction between the wiring Lc and the upper electrode Zu[m] of the piezoelectric element PZ[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-C 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 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] 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] provided on the discharge portion D[m] is supplied to the detection circuit 33 as a detection potential signal VX[m] via the wiring Ls.

[0043] 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] based on the detection potential signal VX[m] supplied from the line Ls. Specifically, the detection circuit 33 generates a signal obtained by amplifying the detection potential signal VX[m] and removing noise components from the detection potential signal VX[m], and outputs the generated signal as the detection signal SK[m].

[0044] When the inkjet printer 1 executes a printing process or a discharge state inspection process, a plurality of 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 discharge section D for the printing process or the discharge state inspection process. Note that, hereinafter, of the plurality of unit periods TP set in the operating period of the inkjet printer 1, the kth unit period TP will be referred to as unit period TP(k). Here, the variable k is a natural number that satisfies k≧1.

[0045] FIG. 5 is a timing chart showing an example of various signals such as the drive signal Com supplied to the head unit 3 during a plurality of unit periods TP.

[0046] As shown in Fig. 5, the control unit 2 outputs a latch signal LAT having a plurality of pulses PLL. As a result, the control unit 2 defines a unit period TP as a period from the rising edge of a pulse PLL to the rising edge of the next pulse PLL. In this embodiment, the pulse PLL is an example of a "latch pulse". Hereinafter, the pulse PLL that defines the start of the unit period TP(k) is referred to as pulse PLL(k). That is, the control unit 2 defines the unit period TP(k) as the period from the rising edge of the pulse PLL(k) of the latch signal LAT to the rising edge of the pulse PLL(k+1) of the latch signal LAT, and defines the unit period TP(k+1) as the period from the rising edge of the pulse PLL(k+1) of the latch signal LAT to the rising edge of the pulse PLL(k+2) of the latch signal LAT.

[0047] 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 TS1 from the rising edge of the pulse PLL to the rising edge of the pulse PLT1, a control period TS2 from the rising edge of the pulse PLT1 to the rising edge of the pulse PLT2, and a control period TS3 from the rising edge of the pulse PLT2 to the rising edge of the pulse PLL. Hereinafter, the pulse PLT1 provided in the unit period TP(k) will be referred to as a pulse PLT1(k), and the pulse PLT2 provided in the unit period TP(k) will be referred to as a pulse PLT2(k).

[0048] As shown in FIG. 5, the designation signal SI 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 driving mode of the discharge section D[m] in each unit period TP when the inkjet printer 1 executes a printing process or a discharge state inspection process. Prior to each unit period TP, the control unit 2 supplies the designation signal SI including the M individual designation signals Sd[1] to Sd[M] to the connection state designation circuit 34 in synchronization with the clock signal CL. Then, during the unit period TP, the connection state designation circuit 34 generates a connection state designation signal Qa[m], a connection state designation signal Qb[m], a connection state designation signal Qc[m], and a connection state designation signal Qs[m] based on the individual designation signal Sd[m].

[0049] In this embodiment, the individual designation signal Sd[m] can take any one of four values ​​during the unit period TP in which the printing process or the ejection state inspection process is executed: a value "1" that designates the ejection section D[m] as a printing ejection section DP; a value "2" that designates the ejection section D[m] as a non-dot forming ejection section DN; a value "3" that designates the ejection section D[m] as an inspection drive ejection section DS1; and a value "4" that designates the ejection section D[m] as a vibration detection ejection section DS2.

[0050] Here, the printing ejection unit DP is an ejection unit D that ejects ink from a nozzle N during a unit period TP to form dots Dt on the recording paper PP. The non-dot-forming ejection unit DN is an ejection unit D that does not eject ink from a nozzle N during a unit period TP and does not form dots Dt on the recording paper PP. The inspection drive ejection unit DS1 is an ejection unit D that is the target of the inspection target drive process during the unit period TP, among the inspection target ejection units DS, as described above. The vibration detection ejection unit DS2 is an ejection unit D that is the target of the residual vibration detection process during the unit period TP, among the inspection target ejection units DS, as described above.

[0051] 5, the driving signal Com-A has a waveform PA1 provided in each unit period TP. Here, the waveform PA1 is a waveform that, in each unit period TP, 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. The waveform PA1 is determined so that when a supply driving signal Vin[m] having the waveform PA1 is supplied to the ejection section D[m], ink equivalent to a dot Dt is ejected from the ejection section D[m].

[0052] 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 CV 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 PA1, 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.

[0053] Hereinafter, the time length from the end of the waveform PA1 of the driving signal Com-A to the end of the unit period TP in which the waveform PA1 is provided may be referred to as the time length GA1. Specifically, the time length GA1 is the time length from the timing when the potential change of the waveform PA1 of the driving signal Com-A from the potential VH1 to the reference potential V0 is completed to the timing when the unit period TP in which the waveform PA1 is provided ends.

[0054] 5, the driving signal Com-B has a waveform PB provided in each unit period TP. Here, the waveform PB is a waveform that, in each unit period TP, changes from a reference potential V0, passes through a potential VB that is higher than the reference potential V0, and returns to the reference potential V0. In this embodiment, the reference potential V0 is an example of a "first potential," and the potential VB is an example of a "second potential."

[0055] Hereinafter, the time length from the end of the waveform PB of the driving signal Com-B to the end of the unit period TP in which the waveform PB is provided may be referred to as the time length GB. Specifically, the time length GB is the time length from the timing when the potential change of the waveform PB of the driving signal Com-B from the potential VB to the reference potential V0 is completed to the timing when the unit period TP in which the waveform PB is provided ends. In the following, the time length required for the waveform PB of the driving signal Com-B to change from the reference potential V0 to the potential VB is referred to as the time length GBu, and the time length required for the waveform PB of the driving signal Com-B to change from the potential VB to the reference potential V0 is referred to as the time length GBu. In this embodiment, the time length GBu is adjusted so that ink is not ejected from the ejection section D[m] even if the ejection section D[m] is driven by the driving signal Com-B. Specifically, in this embodiment, the waveform PB is set so that the time length GBu is longer than the time length GBd.

[0056] As shown in FIG. 5, the driving signal Com-C is a signal that maintains the reference potential V0 in the control period TS1 and the control period TS2 of each unit period TP, and is provided with a waveform PC in the control period TS3 of each unit period TP. Here, the waveform PC is a waveform that returns from the reference potential V0 to the reference potential V0 via a potential VC that is lower than the reference potential V0. In this embodiment, the waveform PC is provided so that ink is not discharged from the discharge section D[m] even if the discharge section D[m] is driven by the driving signal Com-C. In this embodiment, the ink in the cavity CV of the discharge section D[m] is stirred by driving the discharge section D[m] by the driving signal Com-C having the waveform PC, and the thickening of the ink in the discharge section D[m] can be suppressed.

[0057] Hereinafter, the time length from the end of the waveform PC of the driving signal Com-C to the end of the unit period TP in which the waveform PC is provided may be referred to as the time length GC. Specifically, the time length GC is the time length from the timing when the potential change of the waveform PC of the driving signal Com-C from the potential VC to the reference potential V0 is completed to the timing when the unit period TP in which the waveform PC is provided ends.

[0058] In this embodiment, the waveforms PA1, PB, and PC are provided so that the time length GB is shorter than the time length GA1 and is shorter than the time length GC. That is, in this embodiment, the time length GB from the end of the waveform PB to the end of the unit period TP in which the waveform PB is provided is shorter than the time length GA1 from the end of the waveform PA1 to the end of the unit period TP in which the waveform PA1 is provided, and is shorter than the time length GC from the end of the waveform PC to the end of the unit period TP in which the waveform PC is provided. Hereinafter, the waveforms PA1, PB, and PC may be collectively referred to as “drive waveforms.” In addition, in this embodiment, the waveform PB is an example of an “inspection waveform.”

[0059] In this embodiment, the driving signal Com-C has a waveform PC, but the present invention is not limited to this. For example, the driving signal Com-C may be a signal that maintains the reference potential V0 over each unit period TP.

[0060] FIG. 6 is a block diagram showing an example of the configuration of the connection state designation circuit 34. As shown in FIG.

[0061] As shown in FIG. 6, the connection state designation circuit 34 includes M transfer circuits SR[1]-SR[M] provided in one-to-one correspondence with the M discharge units D[1]-D[M], M latch circuits LT[1]-LT[M] provided in one-to-one correspondence with the M discharge units D[1]-D[M], and M decoders DC[1]-DC[M] provided in one-to-one correspondence with the M discharge units D[1]-D[M]. The individual designation signals Sd[1]-Sd[M] are serially supplied to the transfer circuit SR[1]. The individual designation signals Sd[m] supplied to the transfer circuit SR[1] are sequentially transferred from the transfer circuit SR[1] to the transfer circuit SR[m] by the m transfer circuits SR[1]-SR[m] among the M transfer circuits SR[1]-SR[M] in synchronization with the clock signal CL. The latch circuit LT[m] latches the individual designation signal Sd[m] supplied to the transfer circuit SR[m] when the pulse PLL of the latch signal LAT rises to a high level. The decoder DC[m] generates a connection state designation signal Qa[m], a connection state designation signal Qb[m], a connection state designation signal Qc[m], and a connection state designation signal Qs[m] based on the individual designation signal Sd[m], the latch signal LAT, and the period designation signal Tsig.

[0062] FIG. 7 is an explanatory diagram showing an example of the operation of the decoder DC[m].

[0063] 7, when the individual designation signal Sd[m] indicates a value "1" that designates the discharge section D[m] as a print discharge section DP during the unit period TP, the decoder DC[m] sets the connection state designation signal Qa[m] to a high level during the unit period TP. In this case, the switch Wa[m] is turned on during the unit period TP. Therefore, during the unit period TP, the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveform PA1, and discharges an amount of ink equivalent to a dot Dt.

[0064] Furthermore, when the individual designation signal Sd[m] indicates a value "2" that designates the discharge unit D[m] as a dot non-forming discharge unit DN during the unit period TP, the decoder DC[m] sets the connection state designation signal Qa[m], the connection state designation signal Qb[m], the connection state designation signal Qc[m], and the connection state designation signal Qs[m] to a low level during the unit period TP. In this case, the switches Wa[m], Wb[m], Wc[m], and Ws[m] are turned off during the unit period TP. Therefore, the discharge unit D[m] is not driven by the supply drive signal Vin[m] during the unit period TP, and does not discharge ink.

[0065] Also, when the individual designation signal Sd[m] indicates a value "3" that designates the discharge unit D[m] as the inspection drive discharge unit DS1 in the unit period TP, the decoder DC[m] sets the connection state designation signal Qb[m] to a high level for the unit period TP. In this case, the switch Wb[m] is turned on for the unit period TP. Therefore, the discharge unit D[m] is driven by the supply drive signal Vin[m] having the waveform PB in the unit period TP, and vibration occurs in the discharge unit D[m].

[0066] Also, when the individual designation signal Sd[m] indicates a value "4" that designates the discharge section D[m] as the vibration detection discharge section DS2 in the unit period TP, the decoder DC[m] sets the connection state designation signal Qc[m] to a high level in the control period TS1 and the control period TS3, and sets the connection state designation signal Qs[m] to a high level in the control period TS2. In this case, the switch Wc[m] is turned on in the control period TS1 and the control period TS3, and the switch Ws[m] is turned on in the control period TS2. Therefore, when vibration remains in the discharge section D[m] in the control period TS2, the detection circuit 33 detects the potential of the upper electrode Zu[m], which changes according to the vibration remaining in the discharge section D[m], as a detection potential signal VX[m] via the switch Ws[m] in the control period TS2. The waveform of the detected potential signal VX[m] detected from the discharge section D[m] during the control period TS2 represents the waveform of the vibration remaining in the discharge section D[m] during the control period TS2. The waveform of the detected signal SK[m] generated based on the detected potential signal VX[m] detected from the discharge section D[m] during the control period TS2 represents the waveform of the vibration remaining in the discharge section D[m] during the control period TS2.

[0067] Figure 8 is a timing chart showing an example of multiple supply drive signals Vin[m] to Vin[m+2] supplied to multiple discharge sections D[m] to D[m+2] provided in the head unit 3 over multiple unit periods TP(k) to TP(k+3).

[0068] 8, it is assumed that the variable m is a natural number that satisfies "1≦m≦M-2". In addition, hereinafter, the supply drive signal Vin[m] supplied to the discharge section D[m] in the unit period TP(k) is referred to as the supply drive signal Vin[m](k). In addition, hereinafter, the individual designation signal Sd[m] that designates the operation of the discharge section D[m] in the unit period TP(k) is referred to as the individual designation signal Sd[m](k).

[0069] 8 assumes that the inkjet printer 1 executes the ejection state inspection process three times for three ejection units D, ejection unit D[m], ejection unit D[m+1], and ejection unit D[m+2], in four unit periods TP, unit period TP(k), unit period TP(k+1), unit period TP(k+2), and unit period TP(k+3). Also, in Fig. 8, it assumes that the inkjet printer 1 drives, as a printing ejection unit DP, the ejection unit D that is not the target of the ejection state inspection process out of the three ejection units D, ejection unit D[m], ejection unit D[m+1], and ejection unit D[m+2].

[0070] In this embodiment, when the inkjet printer 1 executes an ejection state inspection process targeting the ejection section D[m], it first executes an inspection target drive process targeting the ejection section D[m] in one unit period TP, and then executes a residual vibration detection process targeting the ejection section D[m] in another unit period TP following the one unit period TP.

[0071] Specifically, the control unit 2 generates an individual designation signal Sd[m](k) that designates the discharge section D[m] as the inspection driving discharge section DS1 in the unit period TP(k), and generates an individual designation signal Sd[m](k+1) that designates the discharge section D[m] as the vibration detection discharge section DS2 in the unit period TP(k+1). As a result, as shown in FIG. 8, the inkjet printer 1 supplies a drive signal Com-B having a waveform PB to the discharge section D[m] as a supply drive signal Vin[m](k) in the unit period TP(k), and supplies a drive signal Com-C having a waveform PC to the discharge section D[m] as a supply drive signal Vin[m](k+1) in the unit period TP(k+1). As a result, the inkjet printer 1 executes an inspection target drive process for the discharge section D[m] in the unit period TP(k), and then executes a residual vibration detection process for the discharge section D[m] in the unit period TP(k+1).

[0072] In this case, the discharge section D[m] is driven to vibrate by the drive signal Com-B having the waveform PB during a unit period TP(k) that starts with the pulse PLL(k) and ends with the pulse PLL(k+1).The detection circuit 33 detects the vibration that occurs in the discharge section D[m] during the unit period TP(k) due to driving by the drive signal Com-B and that remains in the discharge section D[m] during the unit period TP(k+1) during the control period TS2 of the unit period TP(k+1), and generates a detection signal SK[m] based on the detection potential signal VX[m] that indicates the detection result.In this way, the inkjet printer 1 executes the discharge state inspection process for the discharge section D[m].

[0073] 8, the inkjet printer 1 supplies a drive signal Com-B having a waveform PB to the ejection section D[m+1] as the supply drive signal Vin[m+1](k+1), and supplies a drive signal Com-C having a waveform PC to the ejection section D[m+1] as the supply drive signal Vin[m+1](k+2). As a result, the inkjet printer 1 executes an inspection target drive process for the ejection section D[m+1] in the unit period TP(k+1), and then executes a residual vibration detection process for the ejection section D[m+1] in the unit period TP(k+2), thereby executing an ejection state inspection process for the ejection section D[m+1]. The inkjet printer 1 also supplies a drive signal Com-B having a waveform PB to the ejection section D[m+2] as the supply drive signal Vin[m+2](k+2), and supplies a drive signal Com-C having a waveform PC to the ejection section D[m+2] as the supply drive signal Vin[m+2](k+3). As a result, the inkjet printer 1 executes an inspection target drive process for the ejection section D[m+2] in the unit period TP(k+2), and then executes a residual vibration detection process for the ejection section D[m+2] in the unit period TP(k+3), thereby executing an ejection state inspection process for the ejection section D[m+2].

[0074] In this embodiment, the unit period TP(k) is an example of a "first unit period", and the unit period TP(k+1) is an example of a "second unit period". In this embodiment, the pulse PLL(k) is an example of a "first latch pulse", the pulse PLL(k+1) is an example of a "second latch pulse", and the pulse PLL(k+2) is an example of a "third latch pulse". In this embodiment, the pulse PLT1(k+1) is an example of a "detection start pulse", the pulse PLT2(k+1) is an example of a "detection end pulse", and the control period TS2 included in the unit period TP(k+1) is an example of a "detection period".

[0075] <<3. Inspection unit>> Hereinafter, an overview of the inspection unit 5 will be described with reference to FIGS.

[0076] As described above, the inspection unit 5 inspects the ink ejection state in the ejection section D[m] designated as the inspection target ejection section DS, based on the detection signal SK[m] supplied from the detection circuit 33.

[0077] 9 is a timing chart for explaining an example of the detection signal SK[m] supplied by the detection circuit 33 to the inspection unit 5. Note that the detection signal SK[m] output by the detection circuit 33 during the control period TS2 indicates a waveform based on the vibration remaining in the discharge section D[m] during the control period TS2.

[0078] 9, the period from when the potential of the detection signal SK[m] coincides with a central potential VK0 set near the center of the amplitude of the detection signal SK[m] to when the potential next coincides with the central potential VK0 is referred to as a cycle period NTC[m]. In addition, the time length of the cycle period NTC[m] is referred to as a cycle TC[m].

[0079] In this embodiment, the inspection unit 5 measures the period TC[m] of the detection signal SK[m]. Then, the inspection unit 5 inspects the ink ejection state of the ejection section D[m] based on the period TC[m], and generates inspection result information SH[m] that indicates the result of the inspection.

[0080] FIG. 10 is an explanatory diagram for explaining an example of generation of the inspection result information SH[m] in the inspection unit 5. As shown in FIG.

[0081] As shown in FIG. 10, the inspection unit 5 inspects the ink ejection state in the ejection section D[m] by comparing the period TC[m] with some or all of the thresholds Tth1, Tth2, and Tth3, and generates inspection result information SH[m] indicating the results of the inspection.

[0082] The threshold value Tth1 is a fixed value that indicates the boundary between the period TC[m] of the residual vibration that occurs in the discharge section D[m] when the discharge state of the discharge section D[m] is normal, and the period TC[m] of the residual vibration that occurs in the discharge section D[m] when air bubbles are mixed into the cavity CV of the discharge section D[m]. Threshold value Tth2 is a value greater than threshold value Tth1, and is a fixed value that indicates the boundary between the period TC[m] of the residual vibration that occurs in the discharge section D[m] when the discharge state of the discharge section D[m] is normal, and the period TC[m] of the residual vibration that occurs in the discharge section D[m] when foreign matter adheres near the nozzle N of the discharge section D[m]. Threshold value Tth3 is a value greater than threshold value Tth2, and is a fixed value that indicates the boundary between the period TC[m] of the residual vibration that occurs in the ejection section D[m] when foreign matter adheres near the nozzle N of the ejection section D[m], and the period TC[m] of the residual vibration that occurs in the ejection section D[m] when the ink in the cavity CV of the ejection section D[m] becomes thicker.

[0083] In this embodiment, when the cycle TC[m] satisfies "Tth1 ≤ TC[m] ≤ Tth2", the inspection unit 5 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 inspection result information SH[m]. Further, when the cycle TC[m] satisfies "TC[m] < Tth1", the inspection unit 5 determines that ejection abnormality due to bubbles has occurred in the ejection unit D[m], and sets the value "2" indicating that ejection abnormality due to bubbles has occurred in the ejection unit D[m] for the inspection result information SH[m]. Further, when the cycle TC[m] satisfies "Tth2 < TC[m] ≤ Tth3", the inspection unit 5 determines that ejection abnormality due to foreign matter adhesion has occurred in the ejection unit D[m], and sets the value "3" indicating that ejection abnormality due to foreign matter adhesion has occurred in the ejection unit D[m] for the inspection result information SH[m]. Further, when the cycle TC[m] satisfies "Tth3 < TC[m]", the inspection unit 5 determines that ejection abnormality due to thickening has occurred in the ejection unit D[m], and sets the value "4" indicating that ejection abnormality due to thickening has occurred in the ejection unit D[m] for the inspection result information SH[m].

[0084] <<4. Reference Example>> Hereinafter, a reference example will be described with reference to FIGS. 11 to 13.

[0085] FIG. 11 is a timing chart showing an example of various signals supplied to the head unit 3 in the reference example.

[0086] 11, the reference example differs from the above-described embodiment in that a drive signal Com-W is supplied to the head unit 3 instead of the drive signal Com, a latch signal LAT-W is supplied instead of the latch signal LAT, a designation signal SI-W is supplied instead of the designation signal SI, and a period designation signal Tsig-W is supplied instead of the period designation signal Tsig. The reference example also differs from the above-described embodiment in that the operating period of the inkjet printer 1 is divided into a plurality of unit periods TP-W. In the reference example, the drive signal Com-W supplied to the discharge section D[m] is referred to as a supply drive signal Vin-W[m].

[0087] In the reference example, the latch signal LAT-W includes a plurality of pulses PLL-W. Thus, the control unit 2 according to the reference example defines a unit period TP-W as a period from the rising edge of a pulse PLL-W to the rising edge of the next pulse PLL-W. In the following, the k-th unit period TP-W in the operating period of the inkjet printer 1 according to the reference example is referred to as unit period TP-W(k). In the following, the pulse PLL-W that specifies the start of the unit period TP-W(k) among the multiple pulses PLL-W included in the latch signal LAT-W is referred to as pulse PLL-W(k). In the following, the supply drive signal Vin-W[m] supplied to the discharge section D[m] in the unit period TP-W(k) is referred to as supply drive signal Vin-W[m](k).

[0088] In addition, in the reference example, the period designation signal Tsig-W has a pulse PLT1-W and a pulse PLT2-W. As a result, the control unit 2 according to the reference example divides the unit period TP-W into a control period TS1-W from the rising edge of the pulse PLL-W to the rising edge of the pulse PLT1-W, a control period TS2-W from the rising edge of the pulse PLT1-W to the rising edge of the pulse PLT2-W, and a control period TS3-W from the rising edge of the pulse PLT2-W to the rising edge of the pulse PLL-W. In the following, the pulse PLT1-W provided in the unit period TP-W(k) will be referred to as pulse PLT1-W(k), and the pulse PLT2-W provided in the unit period TP-W(k) will be referred to as pulse PLT2-W(k).

[0089] In addition, in the reference example, the drive signal Com-W includes a drive signal Com-AW and a drive signal Com-BW. Among these, the driving signal Com-AW is a signal in which a waveform PA1 is provided in each unit period TP-W, and the driving signal Com-BW is a signal in which a waveform PB is provided in a control period TS1-W of each unit period TP-W, a reference potential V0 is maintained in a control period TS2-W of each unit period TP-W, and a waveform PC is provided in a control period TS3-W of each unit period TP-W.

[0090] Furthermore, the control unit 2 according to the reference example supplies a designation signal SI-W to the connection state designation circuit 34 in synchronization with the clock signal CL prior to each unit period TP-W. Here, the designation signal SI-W includes M individual designation signals Sd-W[1] to Sd-W[M] that correspond one-to-one to the M discharge sections D[1] to D[M]. Among these, the individual designation signal Sd-W[m] designates the driving mode of the discharge section D[m] in the unit period TP-W. Specifically, the individual designation signal Sd-W[m] can take any one of three values: a value "1" that designates the discharge section D[m] as a printing discharge section DP, a value "2" that designates the discharge section D[m] as a non-dot forming discharge section DN, and a value "3" that designates the discharge section D[m] as a test target discharge section DS.

[0091] FIG. 12 is an explanatory diagram showing an example of the operation of the decoder DC[m] according to the reference example.

[0092] As shown in Figure 12, when the individual designation signal Sd-W[m] indicates a value of "1" that designates the discharge section D[m] as the printing discharge section DP in the unit period TP-W, the decoder DC[m] in the reference example sets the connection state designation signal Qa[m] to a high level over the unit period TP-W, as in the embodiment described above. Furthermore, when the individual designation signal Sd-W[m] indicates the value "2" which designates the discharge section D[m] as a non-dot-forming discharge section DN in the unit period TP-W, the decoder DC[m] in the reference example sets the connection state designation signal Qa[m], the connection state designation signal Qb[m], the connection state designation signal Qc[m] and the connection state designation signal Qs[m] to a low level over the unit period TP-W, as in the embodiment described above.

[0093] In addition, when the individual designation signal Sd-W[m] indicates a value "3" that designates the discharge section D[m] as the discharge section DS to be inspected in the unit period TP-W, the decoder DC[m] according to the reference example sets the connection state designation signal Qb[m] to a high level in the control period TS1-W and the control period TS3-W of the unit period TP-W, and sets the connection state designation signal Qs[m] to a high level in the control period TS2-W of the unit period TP-W. In this case, the switch Wb[m] is turned on in the control period TS1-W and the control period TS3-W of the unit period TP-W, and the switch Ws[m] is turned on in the control period TS2-W of the unit period TP-W. Therefore, the vibration generated in the discharge section D[m] remains in the control period TS2-W as a result of the discharge section D[m] designated as the discharge section DS to be inspected being driven by the supply drive signal Vin-W[m] having the waveform PB in the control period TS1-W. During the control period TS2-W, 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. During the control period TS2-W, the detection circuit 33 detects the potential of the upper electrode Zu[m], which changes in response to the vibration remaining in the discharge section D[m], as a detected potential signal VX[m] via the switch Ws[m].

[0094] In this way, in the reference example, in the control period TS1-W of the unit period TP-W, the inspection target drive process is executed to drive the inspection target ejection section DS as the inspection drive ejection section DS1, and in the control period TS2-W of the unit period TP-W, the residual vibration detection process is executed to drive the inspection target ejection section DS as the vibration detection ejection section DS2. For this reason, in the reference example, the unit period TP-W requires at least the total time length of the time for driving the inspection drive ejection section DS1 by the waveform PB and the time for detecting the detection potential signal VX[m] from the vibration detection ejection section DS2. On the other hand, the unit period TP according to the embodiment is a period in which only one of the time for driving the inspection drive ejection section DS1 by the waveform PB and the time for detecting the detection potential signal VX[m] from the vibration detection ejection section DS2 is required. For this reason, the unit period TP-W according to the reference example is longer in time than the unit period TP according to the embodiment. Note that in the reference example, as an example, it is assumed that the unit period TP-W has a time length twice as long as the unit period TP.

[0095] Figure 13 is a timing chart showing an example of supply drive signals Vin-W[m] to Vin-W[m+2] supplied to multiple discharge sections D[m] to D[m+2] provided in a head unit 3 of a reference example over multiple unit periods TP-W(k) to TP-W(k+1).

[0096] 13, it is assumed that the variable m is a natural number that satisfies "1≦m≦M-2." In addition, hereinafter, the individual designation signal Sd-W[m] that designates the operation of the discharge section D[m] in the unit period TP-W(k) is referred to as the individual designation signal Sd-W[m](k).

[0097] 13, it is assumed that the inkjet printer 1 according to the reference example executes the ejection state inspection process twice for two ejection sections D, ejection section D[m] and ejection section D[m+1], in two unit periods TP-W, unit period TP-W(k) and unit period TP-W(k+1). Note that in FIG. 13, it is assumed that the unit period TP-W(k) is composed of unit periods TP(k) and TP(k+1), and the unit period TP-W(k+1) is composed of unit periods TP(k+2) and unit periods TP(k+3). Also, in Figure 13, it is assumed that the inkjet printer 1 of the reference example drives, as a printing ejection unit DP, one of the three ejection units D, ejection unit D[m], ejection unit D[m+1], and ejection unit D[m+2], that is not the target of the ejection state inspection process.

[0098] 13, the control unit 2 according to the reference example generates an individual designation signal Sd-W[m](k) that designates the ejection section D[m] as the ejection section DS to be inspected during the unit period TP-W(k). As a result, the inkjet printer 1 according to the reference example executes an ejection state inspection process targeting the ejection section D[m] during the unit period TP-W(k). Furthermore, the control unit 2 according to the reference example generates an individual designation signal Sd-W[m+1](k+1) that designates the ejection section D[m+1] as the ejection section DS to be inspected during the unit period TP-W(k+1). As a result, the inkjet printer 1 according to the reference example executes an ejection state inspection process targeting the ejection section D[m+1] during the unit period TP-W(k+1).

[0099] Thus, according to the reference example, when an ejection state inspection process is performed for one ejection section D in one unit period TP-W, it is not possible to perform an ejection state inspection process for another ejection section D in one unit period TP-W. Therefore, according to the reference example, two ejection state inspection processes are performed in two unit periods TP-W(k) and TP-W(k+1) corresponding to the period from unit period TP(k) to unit period TP(k+3). In contrast, in the above-described embodiment, when an inspection target drive process is performed for one ejection section D in one unit period TP, a residual vibration detection process can be performed for another ejection section D in one unit period TP. Therefore, in the above-described embodiment, three ejection state inspection processes are performed in the period from unit period TP(k) to unit period TP(k+3). That is, according to the embodiment, when multiple ejection state inspection processes are performed for multiple ejection sections D, the time required for the multiple ejection state inspection processes can be shortened compared to the reference example.

[0100] 13, the control unit 2 according to the reference example generates an individual designation signal Sd-W[m+1](k) that designates the discharge section D[m+1] as the print discharge section DP, and an individual designation signal Sd-W[m+2](k) that designates the discharge section D[m+2] as the print discharge section DP, during the unit period TP-W(k). As a result, the inkjet printer 1 according to the reference example forms two dots Dt using the discharge section D[m+1] and the discharge section D[m+2] during the unit period TP-W(k). Furthermore, the control unit 2 according to the reference example generates an individual designation signal Sd-W[m](k+1) that designates the discharge section D[m] as the print discharge section DP, and an individual designation signal Sd-W[m+2](k+1) that designates the discharge section D[m+2] as the print discharge section DP, during the unit period TP-W(k+1). As a result, the inkjet printer 1 according to the reference example forms two dots Dt using the discharge section D[m] and the discharge section D[m+2] during the unit period TP-W(k+1).

[0101] Thus, according to the reference example, four dots Dt are formed by three discharge sections D[m] to D[m+2] in unit periods TP-W(k) and TP-W(k+1) corresponding to the period from unit period TP(k) to unit period TP(k+3), as shown in Fig. 13. In contrast, in the above-described embodiment, six dots Dt are formed in the period from unit period TP(k) to unit period TP(k+3), as shown in Fig. 8. Thus, according to the embodiment, the time required to form a desired number of dots Dt can be shortened compared to the reference example, and the printing process can be speeded up.

[0102] <<5. Conclusion of the embodiment>> As described above, the inkjet printer 1 according to this embodiment includes a discharge section D[m] that discharges ink in response to the supply of a drive signal Com, a supply circuit 31 that supplies the drive signal Com to the discharge section D[m], and a detection circuit 33 that detects vibrations in the discharge section D[m]. The supply circuit 31 supplies a drive signal Com-B having a waveform PB of the drive signal Com to the discharge section D[m] during a unit period TP(k) that starts with a pulse PLL(k) out of a plurality of pulses PLL included in the latch signal LAT supplied to the supply circuit 31 and ends with a pulse PLL(k+1) that follows the pulse PLL(k) out of the plurality of pulses PLL. The detection circuit 33 detects vibrations remaining in the discharge section D[m] during a unit period TP(k+1) that starts with a pulse PLL(k+1) and ends with a pulse PLL(k+2) that follows the pulse PLL(k+1) out of the plurality of pulses PLL.

[0103] In this manner, according to the present embodiment, the ejection section D[m] is driven in one unit period TP, and vibrations are detected from the ejection section D[m] in another unit period TP following the one unit period TP, so that the length of the unit period TP can be shortened compared to an embodiment in which both the ejection section D[m] is driven and vibrations from the ejection section D[m] are detected in one unit period TP. As a result, according to the present embodiment, it is possible to speed up the printing process in which ink is ejected from the ejection section D[m] to form an image on the recording paper PP.

[0104] Furthermore, in the inkjet printer 1 according to this embodiment, a designation signal SI that designates whether or not ink is ejected from the ejection section D[m] during each of the unit periods TP is supplied to the supply circuit 31 at a timing corresponding to each of the unit periods TP defined by the multiple pulse PLLs, and the supply circuit 31 supplies a drive signal Com to the ejection section D[m] during each of the unit periods TP based on the designation signal SI.

[0105] Furthermore, in the inkjet printer 1 according to this embodiment, the detection circuit 33 detects vibrations remaining in the ejection section D[m] during a control period TS2 of the unit period TP(k+1), which begins with a pulse PLT1(k+1) included in the period specification signal Tsig supplied to the supply circuit 31, and ends with a pulse PLT2(k+1) included in the period specification signal Tsig.

[0106] Furthermore, in the inkjet printer 1 according to this embodiment, the drive signal Com includes a drive signal Com-C that is supplied to the ejection section D[m] during at least a portion of the unit period TP(k+1), the drive signal Com-B exhibits a reference potential V0 at the timing when the pulse PLL(k+1) is supplied to the supply circuit 31, and the drive signal Com-C maintains the reference potential V0 at least during the control period TS1 from the timing when the pulse PLL(k+1) is supplied to the supply circuit 31 to the timing when the control period TS2 starts during the unit period TP(k+1).

[0107] Therefore, according to this embodiment, at the timing when the unit period TP(k+1) starts, it is possible to switch the signal supplied to the discharge section D[m] from the drive signal Com-B to the drive signal Com-C. As a result, according to this embodiment, it is possible to supply the drive signal Com-B to the discharge section D[m] to drive the discharge section D[m] in the unit period TP(k), and supply the drive signal Com-C to the discharge section D[m] to detect vibrations from the discharge section D[m] in the unit period TP(k+1).

[0108] Furthermore, in the ink jet printer 1 according to this embodiment, the waveform PB is characterized in that it changes from a reference potential V0 to a potential VB, and then changes from the potential VB to the reference potential V0.

[0109] Furthermore, in the inkjet printer 1 according to this embodiment, the ejection section D[m] comprises a piezoelectric element PZ[m] driven by a drive signal Com, a cavity CV filled with ink and whose volume changes in response to the driving of the piezoelectric element PZ[m], and a nozzle N that ejects the ink in the cavity CV in response to the change in volume of the cavity CV, and is characterized in that the volume of the cavity CV when the drive signal Com-B supplied to the piezoelectric element PZ[m] indicates a reference potential V0 is greater than the volume of the cavity CV when the drive signal Com-B supplied to the piezoelectric element PZ[m] indicates a potential VB.

[0110] Therefore, according to this embodiment, when the ejection section D[m] is driven by a change in the waveform PB of the drive signal Com-B from potential VB to reference potential V0, it is possible to prevent ink from being ejected from the ejection section D[m].

[0111] Furthermore, the ink jet printer 1 according to this embodiment is characterized in that the time it takes for the waveform PB to change from the reference potential V0 to the potential VB is longer than the time it takes for the waveform PB to change from the potential VB to the reference potential V0.

[0112] Therefore, according to this embodiment, when the ejection unit D[m] is driven by the change from the potential VB to the reference potential V0 among the waveforms PB of the drive signal Com-B, large vibrations can be generated in the ejection unit D[m]. Also, according to this embodiment, when the ejection unit D[m] is driven by the change from the reference potential V0 to the potential VB among the waveforms PB of the drive signal Com-B, ejection of ink from the ejection unit D[m] can be prevented.

[0113] Further, in the inkjet printer 1 according to this embodiment, the drive signal Com has a plurality of drive waveforms including the waveform PB, and in one unit period TP defined by a plurality of pulses PLL, the time length GB from the end of the waveform PB to the end of one unit period TP is shorter than the time length from the end of all drive waveforms other than the waveform PB to the end of one unit period TP.

[0114] Therefore, according to this embodiment, compared with the aspect where the time length GB from the end of the waveform PB to the end of one unit period TP is equal to or longer than the time length from the end of other drive waveforms to the end of one unit period TP, the time length from the timing when the driving of the ejection unit D[m] by the waveform PB ends to the timing when the detection of the vibration remaining in the ejection unit D[m] starts can be shortened, and the vibration remaining in the ejection unit D[m] can be detected more reliably.

[0115] <<B. Modification Example>> Each of the above embodiments can be variously modified. Specific modification aspects are exemplified below. Two or more aspects arbitrarily selected from the following examples can be appropriately combined within a non - conflicting range. 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 reused, and the detailed description of each is appropriately omitted.

[0116] <<Modification Example 1>> In the above embodiment, the period designation signal Tsig, which is a signal that defines the control period TS2 during which the detection potential signal VX[m] is detected from the discharge section D[m] in the unit period TP, has been described as an example of a signal that divides the unit period TP, but the present invention is not limited to this embodiment. The unit period TP may be divided by a signal other than the period designation signal Tsig.

[0117] FIG. 14 is a block diagram showing an example of the configuration of a head unit 3Z according to this modified example.

[0118] 14, the head unit 3Z differs from the head unit 3 according to the embodiment in that it includes a connection state designation circuit 34Z instead of the connection state designation circuit 34. The connection state designation circuit 34Z differs from the connection state designation circuit 34 according to the embodiment in that a change signal CH is supplied and that a designation signal SI-Z is supplied instead of the designation signal SI.

[0119] FIG. 15 is a timing chart showing an example of various signals supplied to the head unit 3Z in this modified example.

[0120] As shown in FIG. 15, in this modified example, head unit 3Z differs from head unit 3 of the embodiment in that a change signal CH is supplied, a drive signal Com-Z is supplied instead of drive signal Com, and a designation signal SI-Z is supplied instead of designation signal SI.

[0121] The change signal CH has a plurality of unit periods TP and a corresponding plurality of pulses PLC. The control unit 2 according to this modification divides the unit period TP(k) into a control period TQ1 from the rising edge of the pulse PLL(k) 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(k+1). The pulse PLC is an example of a "change pulse." In the following description, the control period TQ1 and the control period TQ2 may be collectively referred to as the control period TQ.

[0122] The driving signal Com-Z includes the driving signal Com-AZ, the driving signal Com-B described above, and the driving signal Com-C described above. In this modification, the driving signal Com-Z supplied to the discharge section D[m] is referred to as the supply driving signal Vin-Z[m]. In this modification, the driving signal Com-Z supplied to the discharge section D[m] in the unit period TP(k) is referred to as the supply driving signal Vin-Z[m](k).

[0123] The drive signal Com-AZ has a waveform PA1 provided in the control period TQ1 and a waveform PA2 provided in the control period TQ2. As described above, the waveform PA1 is a waveform that goes from a reference potential V0, through a potential VL1 that is lower than the reference potential V0, and a potential VH1 that is higher than the reference potential V0, and then returns to the reference potential V0. In this modified example, the shape of the waveform PA1 is adjusted so that when a supply drive signal Vin-Z[m] having the waveform PA1 is supplied to the ejection section D[m], ink equivalent to the ink amount ξ1 is ejected from the ejection section D[m]. The waveform PA2 is a waveform that goes from a reference potential V0 to a potential VL2 lower than the reference potential V0, and a potential VH2 higher than the reference potential V0, before returning to the reference potential V0. In this modified example, the shape of the waveform PA2 is adjusted so that when a supply drive signal Vin-Z[m] having the waveform PA2 is supplied to the ejection section D[m], ink equivalent to the ink amount ξ2 is ejected from the ejection section D[m]. In the following, a waveform including the waveform PA1 and the waveform PA2 that the drive signal Com-AZ has in each unit period TP may be referred to as a waveform PA.

[0124] Here, the ink amount ξ1 is the ink amount corresponding to a medium dot Dt2. The ink amount ξ2 is less than the ink amount ξ1 and is the ink amount corresponding to a small dot Dt3 that is smaller than the medium dot Dt2. The total amount of the ink amount ξ1 and the ink amount ξ2 is the ink amount corresponding to a large dot Dt1 that is larger than the medium dot Dt2. In the inkjet printer 1 according to this modification, each discharge section D[m] can form any one of three types of dots Dt, large dots Dt1, medium dots Dt2, and small dots Dt3, in each unit period TP. Therefore, according to the inkjet printer 1 according to this modification, it is possible to form a high-resolution image compared to a mode in which each discharge section D[m] can form only one type of dot Dt in each unit period TP.

[0125] In this modified example, the waveform PA2 is arranged so that a time length GA2 from the end of the waveform PA2 to the end of the unit period TP in which the waveform PA2 is provided is longer than the time length GB.

[0126] Furthermore, the control unit 2 according to this modification supplies a designation signal SI-Z to the connection state designation circuit 34Z in synchronization with the clock signal CL prior to each unit period TP. Here, the designation signal SI-Z includes M individual designation signals Sd-Z[1] to Sd-Z[M] that correspond one-to-one to the M discharge sections D[1] to D[M]. Among these, the individual designation signal Sd-Z[m] designates the mode of driving the discharge section D[m] in the unit period TP.

[0127] Specifically, in this modified example, the individual designation signal Sd-Z[m] can take any one of six values ​​in each unit period TP: a value "1" that designates the discharge section D[m] as a large dot forming discharge section DP1, a value "2" that designates the discharge section D[m] as a medium dot forming discharge section DP2, a value "3" that designates the discharge section D[m] as a small dot forming discharge section DP3, a value "4" that designates the discharge section D[m] as a dot non-forming discharge section DN, a value "5" that designates the discharge section D[m] as a test drive discharge section DS1, and a value "6" that designates the discharge section D[m] as a vibration detection discharge section DS2. Here, the large dot forming discharge section DP1 is a discharge section D that discharges the total amount of ink of the ink amount ξ1 and the ink amount ξ2 from the nozzle N in the unit period TP to form a large dot Dt1 on the recording paper PP. The medium dot forming ejection unit DP2 is an ejection unit D that ejects the ink amount ξ1 from the nozzle N during the unit period TP to form a medium dot Dt2 on the recording paper PP. The small dot forming ejection unit DP3 is an ejection unit D that ejects the ink amount ξ2 from the nozzle N during the unit period TP to form a small dot Dt3 on the recording paper PP.

[0128] FIG. 16 is a block diagram showing an example of the configuration of the connection state designation circuit 34Z.

[0129] As shown in FIG. 16, the connection state designation circuit 34Z is different from the connection state designation circuit 34 according to the embodiment in that it includes M decoders DCz[1]-DCz[M] instead of M decoders DC[1]-DC[M]. The individual designation signals Sd-Z[1]-Sd-Z[M] are serially supplied to the transfer circuit SR[1]. The individual designation signal Sd-Z[m] supplied to the transfer circuit SR[1] is transferred in sequence from the transfer circuit SR[1] to the transfer circuit SR[m] by m transfer circuits SR[1]-SR[m] among the M transfer circuits SR[1]-SR[M] in synchronization with the clock signal CL. The latch circuit LT[m] latches the individual designation signal Sd-Z[m] supplied to the transfer circuit SR[m] at the timing when the pulse PLL of the latch signal LAT rises to a high level. In addition, the decoder DCz[m] generates a connection state designation signal Qa[m], a connection state designation signal Qb[m], a connection state designation signal Qc[m], and a connection state designation signal Qs[m] based on the individual designation signal Sd-Z[m], the change signal CH, the latch signal LAT, and the period designation signal Tsig.

[0130] FIG. 17 is an explanatory diagram showing an example of the operation of the decoder DCz[m] according to this modification.

[0131] 17, when the individual designation signal Sd-Z[m] indicates a value of "1" that designates the discharge section D[m] as the large dot-forming discharge section DP1 during the unit period TP, the decoder DCz[m] sets the connection state designation signal Qa[m] to a high level over the unit period TP. In this case, the discharge section D[m] is driven by the supply drive signal Vin[m] having waveforms PA1 and PA2 to discharge the combined amount of ink of the ink amount ξ1 and the ink amount ξ2, and form a large dot Dt1. Furthermore, when the individual designation signal Sd-Z[m] indicates a value of "2" that designates the discharge section D[m] as the medium dot forming discharge section DP2 during the unit period TP, the decoder DCz[m] sets the connection state designation signal Qa[m] to a high level during the control period TQ1. In this case, the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveform PA1 to discharge the ink amount ξ1 to form the medium dot Dt2. Furthermore, when the individual designation signal Sd-Z[m] indicates a value of "3" that designates the discharge section D[m] as the small dot forming discharge section DP3 during the unit period TP, the decoder DCz[m] sets the connection state designation signal Qa[m] to a high level during the control period TQ2. In this case, the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveform PA2 to discharge the ink amount ξ2 and form the small dot Dt3. In addition, when the individual designation signal Sd-Z[m] designates the discharge section D[m] as a non-dot forming discharge section DN during the unit period TP, when the discharge section D[m] is designated as an inspection driving discharge section DS1, and when the discharge section D[m] is designated as a vibration detection discharge section DS2, the discharge section D[m] operates in the same manner as in the above-described embodiment.

[0132] Figure 18 is a timing chart showing an example of supply drive signals Vin-Z[m] to Vin-Z[m+2] supplied to multiple discharge sections D[m] to D[m+2] provided in a head unit 3Z over multiple unit periods TP(k) to TP(k+3).

[0133] 18, it is assumed that the variable m is a natural number that satisfies "1≦m≦M-2". In addition, hereinafter, the individual designation signal Sd-Z[m] that designates the operation of the discharge section D[m] in the unit period TP(k) is referred to as the individual designation signal Sd-Z[m](k).

[0134] 18, it is assumed that the discharge state inspection process is executed three times for three discharge units D, discharge unit D[m], discharge unit D[m+1], and discharge unit D[m+2], in four unit periods TP, unit period TP(k), unit period TP(k+1), unit period TP(k+2), and unit period TP(k+3). Also, in FIG. 18, it is assumed that the discharge unit D that is not the target of the discharge state inspection process among the three discharge units D, discharge unit D[m], discharge unit D[m+1], and discharge unit D[m+2], is driven as the large dot forming discharge unit DP1.

[0135] The control unit 2 according to this modification generates an individual designation signal Sd-Z[m](k) that designates the discharge section D[m] as the inspection driving discharge section DS1 in the unit period TP(k), and generates an individual designation signal Sd-Z[m](k+1) that designates the discharge section D[m] as the vibration detection discharge section DS2 in the unit period TP(k+1). As a result, the inkjet printer 1 according to this modification supplies a drive signal Com-B having a waveform PB as a supply drive signal Vin-Z[m](k) to the discharge section D[m] in the unit period TP(k), and supplies a drive signal Com-C having a waveform PC to the discharge section D[m] as a supply drive signal Vin-Z[m](k+1) in the unit period TP(k+1), as shown in FIG. As a result, the inkjet printer 1 according to this modification executes the inspection target drive process for the ejection section D[m] in the unit period TP(k), and then executes the residual vibration detection process for the ejection section D[m] in the unit period TP(k+1). The inkjet printer 1 according to this modification executes the inspection target drive process for the ejection section D[m+1] in the unit period TP(k+1), and then executes the residual vibration detection process for the ejection section D[m+1] in the unit period TP(k+2), thereby executing the ejection state inspection process for the ejection section D[m+1]. The inkjet printer 1 according to this modification executes the inspection target drive process for the ejection section D[m+2] in the unit period TP(k+2), and then executes the residual vibration detection process for the ejection section D[m+2] in the unit period TP(k+3), thereby executing the ejection state inspection process for the ejection section D[m+2].

[0136] As described above, the inkjet printer 1 according to this modified example includes a discharge section D[m] that discharges ink in response to the supply of a drive signal Com-Z, a supply circuit 31 that supplies the drive signal Com-Z to the discharge section D[m], and a detection circuit 33 that detects vibrations in the discharge section D[m]. The supply circuit 31 supplies a drive signal Com-B having a waveform PB of the drive signal Com-Z to the discharge section D[m] during a unit period TP(k) that is started by a pulse PLL(k) out of a plurality of pulses PLL included in a latch signal LAT supplied to the supply circuit 31 and ends by a pulse PLL(k+1) that is provided next to the pulse PLL(k) out of the plurality of pulses PLL. The detection circuit 33 detects vibrations in the discharge section D[m] during a unit period TP(k+1) that is started by a pulse PLL(k+1) and ends by a pulse PLL(k+2) that is provided next to the pulse PLL(k+1) out of the plurality of pulses PLL. a designation signal SI-Z for specifying whether or not ink is ejected from the ejection section D[m] in each of a plurality of unit periods TP defined by a plurality of pulses PLL is supplied to a supply circuit 31 at a timing corresponding to each of the plurality of unit periods TP defined by a plurality of pulses PLL; a change signal CH having a plurality of pulses PLC for dividing each of the plurality of unit periods TP into a plurality of control periods TQ is supplied; the designation signal SI-Z supplied to the supply circuit 31 at a timing corresponding to one of the plurality of unit periods TP specifies the presence or absence of ink from the ejection section D[m] in each of the plurality of control periods TQ constituting the one unit period TP; and the supply circuit 31 supplies a drive signal Com-Z to the ejection section D[m] in each of the plurality of control periods TQ constituting the one unit period TP based on the designation signal SI-Z supplied to the supply circuit 31 at a timing corresponding to the one unit period TP.

[0137] In this manner, according to this modification, the ejection section D[m] is driven in one unit period TP, and vibrations are detected from the ejection section D[m] in another unit period TP following the one unit period TP, so that the length of the unit period TP can be shortened compared to a mode in which both the ejection section D[m] is driven and vibrations from the ejection section D[m] are detected in one unit period TP. As a result, according to this modification, it is possible to speed up the printing process in which ink is ejected from the ejection section D[m] to form an image on the recording paper PP.

[0138] <<Variation 2>> In the above-described embodiment and modified example 1, the case where the inspection unit 5 is provided separately from the head unit 3 has been described as an example, but the present invention is not limited to this aspect. The inspection unit 5 may be provided in the head unit 3. In this case, compared to an aspect where the inspection unit 5 is provided outside the head unit 3, it is possible to suppress the possibility of noise being mixed into the detection signal SK[m] supplied from the detection circuit 33 to the inspection unit 5, thereby improving the accuracy of inspection in the inspection unit 5.

[0139] <<Variation 3>> In the above-described embodiment and modified examples 1 and 2, it is assumed that the inkjet printer 1 has four head units 3, but the present invention is not limited to this embodiment. The inkjet printer 1 may have one to three head units 3, or may have five or more head units 3.

[0140] <<Variation 4>> In the above-described embodiment and modifications 1 to 4, 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 PP. [Explanation of symbols]

[0141] 1...inkjet printer, 2...control unit, 3...head unit, 4...drive signal generating unit, 5...inspection unit, 6...storage unit, 7...transport unit, 31...supply circuit, 32...recording head, 33...detection circuit.

Claims

1. an ejection unit that ejects liquid in response to a drive signal; A supply unit that supplies the drive signal to the ejection unit; A detection unit that detects vibrations in the ejection unit; Equipped with the supply unit supplies, to the ejection unit, a test drive signal having a test waveform among the drive signals, in a first unit period that is started by a first latch pulse among a plurality of latch pulses included in a latch signal supplied to the supply unit and that is ended by a second latch pulse among the plurality of latch pulses that is provided next to the first latch pulse; the detection unit detects vibration remaining in the ejection unit during a second unit period that is started by the second latch pulse and that is ended by a third latch pulse that is provided next to the second latch pulse among the plurality of latch pulses; A liquid ejection head comprising:

2. a designation signal that designates whether or not liquid is to be ejected from the ejection section during each of a plurality of unit periods defined by the plurality of latch pulses is supplied to the supply section at a timing corresponding to each of the plurality of unit periods; the supply unit supplies the drive signal to the discharge unit based on the designation signal during each of the plurality of unit periods.

2. The liquid ejection head according to claim 1, wherein the liquid ejection head is a liquid ejection head.

3. a change signal having a plurality of change pulses for dividing each of the plurality of unit periods into a plurality of control periods is supplied to the supply unit; the designation signal supplied to the supply unit at a timing corresponding to one of the plurality of unit periods designates whether or not liquid is to be ejected from the ejection unit in each of a plurality of control periods constituting the one unit period; the supply unit supplies the drive signal to the discharge unit based on a designation signal supplied to the supply unit at a timing corresponding to the one unit period during each of a plurality of control periods constituting the one unit period; 3. The liquid ejection head according to claim 2, wherein the liquid ejection head is a liquid ejection head.

4. the detection unit detects vibration remaining in the ejection unit during a detection period of the second unit period, the detection period being started by a detection start pulse included in a period designation signal supplied to the supply unit and ending by a detection end pulse included in the period designation signal.

2. The liquid ejection head according to claim 1, wherein the liquid ejection head is a liquid ejection head.

5. the drive signal includes a detection drive signal that is supplied to the ejection section during at least a portion of the second unit period, the test drive signal exhibits a first potential at a timing when the second latch pulse is supplied to the supply unit; the detection drive signal maintains the first potential at least during a period from a timing when the second latch pulse is supplied to the supply unit to a timing when the detection period starts, during the second unit period.

5. The liquid ejection head according to claim 4.

6. the inspection waveform is a waveform that changes from the first potential to a second potential and then changes from the second potential to the first potential; 6. The liquid ejection head according to claim 5,

7. The discharge unit is a piezoelectric element driven by the drive signal; a pressure chamber filled with liquid and whose volume changes in response to the driving of the piezoelectric element; a nozzle that ejects liquid in the pressure chamber in response to a change in volume of the pressure chamber; Equipped with The volume of the pressure chamber when the drive signal supplied to the piezoelectric element indicates the first potential is the volume of the pressure chamber when the drive signal supplied to the piezoelectric element indicates the second potential; 7. The liquid ejection head according to claim 6,

8. The time it takes for the test waveform to change from the first potential to the second potential is the time required for the test waveform to change from the second potential to the first potential is longer than the time required for the test waveform to change from the second potential to the first potential, 8. The liquid ejection head according to claim 7.

9. the drive signal has a plurality of drive waveforms including the test waveform, In one unit period defined by the plurality of latch pulses, The time length from the end of the inspection waveform to the end of one unit period is a time length that is shorter than a time length from the end of all driving waveforms other than the test waveform among the plurality of driving waveforms to the end of one unit period; 2. The liquid ejection head according to claim 1, wherein the liquid ejection head is a liquid ejection head.

10. an ejection unit that ejects liquid in response to a drive signal; A supply unit that supplies the drive signal to the ejection unit; A detection unit that detects vibrations in the ejection unit; Equipped with the supply unit supplies, to the ejection unit, a test drive signal having a test waveform among the drive signals, in a first unit period that is started by a first latch pulse among a plurality of latch pulses included in a latch signal supplied to the supply unit and that is ended by a second latch pulse among the plurality of latch pulses that is provided next to the first latch pulse; the detection unit detects vibration remaining in the ejection unit during a second unit period that is started by the second latch pulse and that is ended by a third latch pulse that is provided next to the second latch pulse among the plurality of latch pulses; A liquid ejection device comprising:

11. an ejection unit that ejects liquid in response to a drive signal; A supply unit that supplies the drive signal to the ejection unit; A detection unit that detects vibrations in the ejection unit; A method for controlling a liquid ejection head, comprising: controlling the liquid ejection head so that the supply unit supplies to the ejection unit an inspection drive signal having an inspection waveform among the drive signals in a first unit period that starts with a first latch pulse among a plurality of latch pulses included in the latch signal supplied to the supply unit and ends with a second latch pulse among the plurality of latch pulses that follows the first latch pulse; controlling the liquid ejection head so that the detection unit detects vibration remaining in the ejection unit during a second unit period that is started by the second latch pulse and that is ended by a third latch pulse that is provided next to the second latch pulse among the plurality of latch pulses; A method for controlling a liquid ejection head comprising the steps of:

12. supplying, to the supply unit, a designation signal that designates whether or not liquid is to be discharged from the discharge unit during each of the plurality of unit periods, at a timing corresponding to each of the plurality of unit periods defined by the plurality of latch pulses; controlling the liquid ejection head so that the supply unit supplies the drive signal to the ejection unit based on the designation signal during each of the plurality of unit periods; 12. The control method according to claim 11 .

13. supplying, to the supply unit, a change signal having a plurality of change pulses for dividing each of the plurality of unit periods into a plurality of control periods; the designation signal supplied to the supply unit at a timing corresponding to one of the plurality of unit periods designates whether or not liquid is to be ejected from the ejection unit in each of a plurality of control periods constituting the one unit period; controlling the liquid ejection head so that the supply unit supplies the drive signal to the ejection unit based on a designation signal supplied to the supply unit at a timing corresponding to the one unit period during each of a plurality of control periods constituting the one unit period; 13. The control method according to claim 12.

14. controlling the liquid ejection head so that the detection unit detects vibration remaining in the ejection unit during a detection period of the second unit period, the detection period being started by a detection start pulse included in a period designation signal supplied to the supply unit and ending by a detection end pulse included in the period designation signal; 12. The control method according to claim 11 .

15. the drive signal includes a detection drive signal that is supplied to the ejection section during at least a portion of the second unit period, the test drive signal exhibits a first potential at a timing when the second latch pulse is supplied to the supply unit; the detection drive signal maintains the first potential at least during a period from a timing when the second latch pulse is supplied to the supply unit to a timing when the detection period starts, during the second unit period.

15. The control method according to claim 14,

16. the inspection waveform is a waveform that changes from the first potential to a second potential and then changes from the second potential to the first potential; 16. The control method according to claim 15,

17. The discharge unit is a piezoelectric element driven by the drive signal; a pressure chamber filled with liquid and whose volume changes in response to the driving of the piezoelectric element; a nozzle that ejects liquid in the pressure chamber in response to a change in volume of the pressure chamber; Equipped with The volume of the pressure chamber when the drive signal supplied to the piezoelectric element indicates the first potential is the volume of the pressure chamber when the drive signal supplied to the piezoelectric element indicates the second potential; 17. The control method according to claim 16,

18. The time it takes for the test waveform to change from the first potential to the second potential is the time required for the test waveform to change from the second potential to the first potential is longer than the time required for the test waveform to change from the second potential to the first potential, 20. The control method according to claim 17,

19. the drive signal has a plurality of drive waveforms including the test waveform, In one unit period defined by the plurality of latch pulses, The time length from the end of the inspection waveform to the end of one unit period is a time length that is shorter than a time length from the end of all driving waveforms other than the test waveform among the plurality of driving waveforms to the end of one unit period; 12. The control method according to claim 11 .

Images