Maintenance method and liquid discharge device

Abstract

To perform a flushing process for discharging an appropriate discharge amount of ink I in accordance with the viscosity of the ink I in a discharge unit D.SOLUTION: This maintenance method for a liquid discharge device 1 provided with a plurality of discharge units D for discharging liquids includes acquiring first viscosity information NtF1[m] regarding the viscosity of the liquid filling each of the discharger units D, discharging a first amount of the liquid from each of the discharge units D, acquiring second viscosity information NtF2[m] regarding the viscosity of the liquid filling each of the discharge units D, generating difference information indicating a difference between the viscosity indicated by the first viscosity information NtF1[m] and the viscosity indicated by the second viscosity information NtF2[m] in each of the discharge units D, and discharging the first amount of the liquid again from the discharge unit D in which the difference indicated by the difference information is equal to or larger than a prescribed value α among the discharge units D, but not discharging the liquid from the discharge unit D in which the difference indicated by the difference information is less than the prescribed value among the discharge units D.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a maintenance method and a liquid ejection apparatus. [Background technology]

[0002] In a liquid ejection device having an ejection unit that ejects liquid from a nozzle, the nozzle may become clogged, making it impossible to eject liquid from the nozzle. In order to prevent such clogging of the nozzle, a flushing operation is performed to discharge the liquid from the ejection unit. For example, Patent Document 1 discloses a technique in which the amount of liquid to be discharged from the ejection unit in the flushing operation is predetermined, and the predetermined amount of liquid is discharged in the flushing operation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-233518 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, a predetermined amount of liquid is discharged during the flushing operation, so the amount of ink discharged during the flushing operation can sometimes be excessive, exceeding the amount of ink discharged necessary to ensure printing quality in the liquid ejection device. [Means for solving the problem]

[0005] A maintenance method according to one aspect of the present invention is a maintenance method for a liquid ejection device having a plurality of ejection sections that eject liquid, the method comprising the steps of: acquiring first viscosity information regarding the viscosity of liquid filled in each of the plurality of ejection sections; ejecting a first amount of liquid from each of the plurality of ejection sections; acquiring second viscosity information regarding the viscosity of liquid filled in each of the plurality of ejection sections; generating difference information indicating the difference between the viscosity indicated by the first viscosity information and the viscosity indicated by the second viscosity information for each of the plurality of ejection sections; ejecting the first amount of liquid again from those of the plurality of ejection sections for which the difference indicated by the difference information is greater than or equal to a predetermined value; and not ejecting liquid from those of the plurality of ejection sections for which the difference indicated by the difference information is less than the predetermined value.

[0006] Furthermore, a liquid ejection device according to one aspect of the present invention includes a plurality of ejection units that eject liquid, an acquisition unit that acquires viscosity information regarding the viscosity of the liquid filled in each of the plurality of ejection units, an ejection control unit that causes each of the plurality of ejection units to eject liquid, and a generation unit that generates difference information indicating a difference between the viscosity indicated by the first viscosity information and the viscosity indicated by the second viscosity information when the acquisition unit acquires first viscosity information regarding the viscosity of the liquid filled in each of the plurality of ejection units and the ejection control unit has ejected a first amount of liquid from each of the plurality of ejection units and, after the acquisition unit has ejected a first amount of liquid from each of the plurality of ejection units, generates difference information indicating a difference between the viscosity indicated by the first viscosity information and the viscosity indicated by the second viscosity information, and the ejection control unit ejects the first amount of liquid again from those of the plurality of ejection units for which the difference indicated by the difference information is equal to or greater than a predetermined value, and does not eject liquid from those of the plurality of ejection units for which the difference indicated by the difference information is less than the predetermined value. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a functional block diagram illustrating an example of the configuration of an inkjet printer 1. [Diagram 2] FIG. 1 is a schematic diagram illustrating an inkjet printer 1. [Diagram 3] FIG. 2 is a schematic partial cross-sectional view of a recording head HD. [Figure 4] FIG. 2 is a block diagram showing an example of the configuration of a head unit HU. [Diagram 5] 1 is a timing chart illustrating the operation of the inkjet printer 1 in a unit period Tu. [Figure 6] FIG. 11 is an explanatory diagram for explaining generation of connection state designation signals SLa[m], SLb[m], and SLs[m]. [Figure 7] 10 is an explanatory diagram for explaining an example of a residual vibration signal NES. FIG. [Figure 8] FIG. 13 is an explanatory diagram for explaining the ink discharging process for one discharge section D[k]. [Figure 9] FIG. 13 is an explanatory diagram for explaining an ink discharging process for one discharge section D[j]. [Figure 10] 4 is a flowchart showing the operation of a control unit 6. [Figure 11] FIG. 2 is a functional block diagram illustrating an example of the configuration of an inkjet printer 1A. [Figure 12] FIG. 13 is an explanatory diagram for explaining the ink discharging process for one discharge section D[m]. [Figure 13] FIG. 13 is a schematic diagram of a discharge section D. [Figure 14] 13 is a table showing the number of shots FC in the n-th flushing process. [Figure 15] 4 is a flowchart showing the operation of a control unit 6A. [Figure 16] 13 is a table showing the number of shots FC in the n-th flushing process. [Figure 17] 4 is a flowchart showing the operation of a control unit 6A. [Figure 18] 4 is a flowchart showing the operation of a control unit 6A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0010] 1-1: Overview of Inkjet Printer 1 The configuration of an inkjet printer 1 according to this embodiment will be described with reference to Figures 1 and 2. Here, Figure 1 is a functional block diagram showing an example of the configuration of an inkjet printer 1 according to this embodiment. Also, Figure 2 is a schematic diagram illustrating the inkjet printer 1.

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

[0012] As illustrated in FIG. 1, the inkjet printer 1 includes a head unit HU provided with an ejection section D that ejects ink I, a control section 6 that controls the operation of each section of the inkjet printer 1, a drive signal generation circuit 2 that generates a drive signal Com for driving the ejection section D, a memory section 5 that stores the control program and other information of the inkjet printer 1, a measurement circuit 9 that determines the ejection state of the ejection section D and outputs determination information Stt that indicates the result of the ejection state, and phase information NtF related to the viscosity of the ink I in the ejection section D, a transport mechanism 7 that transports recording paper Pp, a moving mechanism 8 that moves the head unit HU, and a maintenance unit 4 that executes a maintenance process that maintains the ejection section D so that ink I is ejected normally from the ejection section D.

[0013] In this embodiment, the head unit HU includes a recording head HD having M ejection sections D, a switching circuit 10, and a detection circuit 20. In this embodiment, M is an integer of 2 or more.

[0014] In the following, in order to distinguish between the M discharge sections D provided in the recording head HD, they may be referred to in order as 1st stage, 2nd stage, ..., Mth stage. Furthermore, the mth stage of a discharge section D may be referred to as a discharge section D[m]. The variable m is an integer that satisfies 1 to M. Furthermore, when a component, signal, etc. of the inkjet printer 1 corresponds to the stage number m of the discharge sections D[m], the subscript [m] indicating that the component, signal, etc. corresponds to the stage number m may be added to the symbol representing the component, signal, etc.

[0015] The switching circuit 10 switches whether or not to supply the drive signal Com output from the drive signal generating circuit 2 to each discharge section D. In addition, the switching circuit 10 switches whether or not to electrically connect each discharge section D and the detection circuit 20.

[0016] The detection circuit 20 generates a residual vibration signal NES[m] that indicates the vibration remaining in the discharge section D[m] after the discharge section D[m] is driven, based on the detection signal Vout[m] detected from the discharge section D[m] driven by the drive signal Com. Hereinafter, this vibration is referred to as "residual vibration."

[0017] The inkjet printer 1 according to this embodiment executes a discharge state determination process that determines whether the discharge state of the ink I from the discharge section D is normal. In the discharge state determination process, the measurement circuit 9 generates determination information Stt[m] indicating whether the discharge state of the ink I from the discharge section D[m] is normal or not, based on the residual vibration signal NES[m]. Note that, in the discharge state determination process, the process in which the measurement circuit 9 generates the determination information Stt[m] based on the residual vibration signal NES[m] may be referred to as the discharge state determination process below. Also, in the discharge state determination process, the discharge section D that is the subject of the discharge state determination by the measurement circuit 9 may be referred to as the determination subject discharge section DH. Furthermore, in the discharge state determination process, the measurement circuit 9 generates phase information NtF[m] indicating the phase of the residual vibration in the discharge section D[m] based on the residual vibration signal NES[m]. In general, the phase of the residual vibration in the discharge section D[m] varies depending on the viscosity of the ink I filled in the discharge section D[m]. Therefore, the phase information NtF[m] indicates a value corresponding to the viscosity of the ink I filled in the discharge section D[m]. Therefore, in this embodiment, the phase information NtF[m] is adopted as "viscosity information", which is information regarding the viscosity of the ink I filled in the discharge section D[m].

[0018] In this embodiment, it is assumed that the inkjet printer 1 is a serial printer. Specifically, as shown in FIG. 2, the inkjet printer 1 executes a printing process by ejecting ink I from an ejection unit D while transporting the recording paper Pp in the sub-scanning direction and moving the head unit HU in the main scanning direction. In this embodiment, as shown in FIG. 2, the +X direction and the -X direction opposite to the +X direction are the main scanning direction, and the +Y direction is the sub-scanning direction. Hereinafter, the +X direction and the -X direction are collectively referred to as the "X-axis direction", and the +Y direction and the -Y direction opposite to the +Y direction are collectively referred to as the "Y-axis direction". Furthermore, the direction perpendicular to the X-axis direction and the Y-axis direction and the ejection direction of the ink I is referred to as the -Z direction. The -Z direction and the +Z direction opposite to the -Z direction are collectively referred to as the "Z-axis direction".

[0019] The print head HD and the ejection sections D provided in the print head HD will be described with reference to FIG.

[0020] FIG. 3 is a schematic partial cross-sectional view of the recording head HD, in which the recording head HD is cut so as to include a discharge portion D. As shown in FIG. 3, the ejection section D includes a piezoelectric element PZ, a cavity 320 filled with ink I, a nozzle N communicating with the cavity 320, and a vibration plate 310. The cavity 320 is an example of a "pressure chamber." In the ejection section D, a drive signal Com is supplied to the piezoelectric element PZ, and the piezoelectric element PZ is driven by the drive signal Com, thereby ejecting the ink I in the cavity 320 from the nozzle N. The cavity 320 is a space defined by a cavity plate 340, a nozzle plate 330 in which the nozzle N is formed, and the vibration plate 310. The cavity 320 communicates with a reservoir 350 via an ink supply port 360. The reservoir 350 communicates with the liquid container 14 corresponding to the ejection section D via an ink intake port 370.

[0021] In this embodiment, the piezoelectric element PZ is of a unimorph type as shown in Fig. 3. Note that the piezoelectric element PZ is not limited to the unimorph type, and a bimorph type, a laminated type, or the like may also be used.

[0022] The piezoelectric element PZ has an upper electrode Zu, a lower electrode Zd, and a piezoelectric body Zm provided between the upper electrode Zu and the lower electrode Zd. The piezoelectric element PZ is a passive element that deforms in response to a change in potential of a drive signal Com. When the lower electrode Zd is electrically connected to a power supply line LHd set to a constant potential VBS and a drive signal Com is supplied to the upper electrode Zu, a voltage is applied between the upper electrode Zu and the lower electrode Zd. The piezoelectric element PZ is displaced in the +Z direction or the -Z direction in response to the applied voltage, and as a result of this displacement, the piezoelectric element PZ vibrates.

[0023] A vibration plate 310 is placed at the opening on the top surface of the cavity plate 340. A lower electrode Zd is bonded to the vibration plate 310. Therefore, when the piezoelectric element PZ is driven to vibrate by the drive signal Com, the vibration plate 310 also vibrates. The volume of the cavity 320 changes due to the vibration of the vibration plate 310, and the ink I filled in the cavity 320 is ejected from the nozzle N. When the ink I in the cavity 320 decreases due to the ejection of the ink I, the ink I is supplied from the reservoir 350.

[0024] The transport mechanism 7 transports the recording paper Pp in the +Y direction. Specifically, the transport mechanism 7 includes a transport roller (not shown) whose rotation axis is parallel to the X-axis direction, and a motor (not shown) that rotates the transport roller under the control of the control unit 6.

[0025] The movement mechanism 8 reciprocates the head unit HU along the X axis under the control of the control unit 6. As illustrated in Fig. 2, the movement mechanism 8 includes a substantially box-shaped conveyor 82 that houses the head unit HU, and an endless belt 81 to which the conveyor 82 is fixed.

[0026] The maintenance unit 4 includes a cap 42 for covering each head unit HU so as to seal the nozzle N of the ejection portion D, a wiper 44 for wiping off foreign matter such as paper dust adhering to the vicinity of the nozzle N of the ejection portion D, a tube pump (not shown) for sucking the ink I and air bubbles in the ejection portion D, and a discharged ink receiving portion (not shown) for receiving the ink I discharged when discharging the ink I in the ejection portion D. The maintenance unit 4 is provided in an area that does not overlap with the recording paper Pp when viewed in the Z axis direction.

[0027] The storage unit 5 includes volatile memory such as RAM, and non-volatile memory such as ROM, EEPROM, or PROM, and stores various information such as print data Img supplied from the host computer and the control program for the inkjet printer 1. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. PROM is an abbreviation for Programmable ROM.

[0028] The control unit 6 includes a CPU. CPU is an abbreviation for Central Processing Unit. However, the control unit 6 may include a programmable logic device such as an FPGA instead of the CPU. FPGA is an abbreviation for Field Programmable Gate Array.

[0029] The CPU provided in the control unit 6 operates according to the control program stored in the storage unit 5, causing the inkjet printer 1 to execute printing processes and maintenance processes.

[0030] In addition, the control unit 6 executes a control program stored in the memory unit 5 and operates in accordance with the control program, thereby functioning as a drive control unit 61, an ejection control unit 62, an ejection amount determination unit 63, an acquisition unit 64, and a generation unit 65.

[0031] The drive control unit 61 generates a waveform designation signal dCom for controlling the drive signal generation circuit 2. The ejection control unit 62 generates a print signal SI for controlling the head unit HU. In addition, the control unit 6 generates a signal for controlling the transport mechanism 7 and a signal for controlling the movement mechanism 8. Here, the waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the discharge section D. The drive signal generation circuit 2 includes a DA conversion circuit and generates the drive signal Com having a waveform defined by the waveform designation signal dCom. In this embodiment, it is assumed that the drive signal Com includes a drive signal Com-A and a drive signal Com-B. Moreover, the print signal SI is a digital signal for specifying the type of operation of the ejection section D. Specifically, the print signal SI specifies whether or not to supply the drive signal Com to the ejection section D, thereby specifying the type of operation of the ejection section D. Here, specifying the type of operation of the ejection section D means, for example, specifying whether or not to drive the ejection section D, specifying whether or not ink I is ejected from the ejection section D when the ejection section D is driven, and specifying the amount of ink ejected from the ejection section D when the ejection section D is driven.

[0032] When the printing process is executed, the ejection control unit 62 first stores the print data Img supplied from the host computer in the storage unit 5. Next, the ejection control unit 62 generates various control signals, such as a print signal SI, a waveform designation signal dCom, a signal for controlling the transport mechanism 7, and a signal for controlling the movement mechanism 8, based on various data such as the print data Img stored in the storage unit 5. Then, based on the various control signals and the various data stored in the storage unit 5, the ejection control unit 62 controls the transport mechanism 7 and the movement mechanism 8 to change the relative position of the recording paper Pp with respect to the head unit HU, while controlling the head unit HU to drive the ejection unit D. In this way, the ejection control unit 62 adjusts the presence or absence of ejection of ink I from the ejection unit D, the ejection amount of ink I, the ejection timing of ink I, and the like, and controls the execution of the printing process to form an image corresponding to the print data Img on the recording paper Pp.

[0033] As described above, the inkjet printer 1 according to this embodiment executes a discharge state determination process that determines whether the discharge state of the ink I from the discharge section D is normal.

[0034] In the ejection state determination process, the inkjet printer 1 executes a series of processes, namely, a first process, a second process, a third process, a fourth process, a fifth process, a sixth process, and a seventh process, as shown below. In the first process, the control unit 6 selects an ejection unit DH to be determined from among M ejection units D provided in the head unit HU. In the second process, the control unit 6 drives the ejection unit DH to be determined, thereby causing residual vibrations in the ejection unit DH to be determined. In the third process, the detection circuit 20 generates a residual vibration signal NES based on the detection signal Vout detected from the ejection unit DH to be determined. In the fourth process, the measurement circuit 9 performs an ejection state determination process for the ejection unit DH to be determined based on the residual vibration signal NES, and generates determination information Stt indicating the result of the determination. In the fifth process, the control unit 6 stores the determination information Stt in the storage unit 5. In the sixth process, the measurement circuit 9 generates phase information NtF based on the residual vibration signal NES. In the seventh process, the control unit 6 stores the phase information NtF in the storage unit 5.

[0035] As described above, the inkjet printer 1 according to this embodiment executes a maintenance process to restore the ejection state of the ink I in the ejection section D that has experienced an ejection abnormality to normal. Furthermore, the inkjet printer 1 of this embodiment executes a maintenance process before and after a printing process to keep the viscosity of the ink I in all of the M ejection sections D within an appropriate range. Specifically, the maintenance process is a process for returning the ejection state of the ink I of the ejection section D to normal by executing one or more of a wiping process, a pumping process, and an ink discharging process. The wiping process is a process in which foreign matter such as paper powder adhering to the vicinity of the nozzle N of the ejection section D is wiped off by the wiper 44. The pumping process is a process in which the ink I and air bubbles in the ejection section D are sucked up by a tube pump. The ink discharging process is a process in which the ink I is discharged from the ejection section D by driving the ejection section D. The inkjet printer 1 executes a flushing process one or more times in the ink discharging process. Also, the inkjet printer 1 executes a flushing operation one or more times in the flushing process. Hereinafter, the number of times the flushing operation is executed in the flushing process may be referred to as the "shot count FC." Also, in the following description, in order to indicate a specific value of the shot count FC, one or more letters x may be used to denote the shot count FCx. In this embodiment, the amount of ink I ejected from the nozzles N by one flushing operation for the number of shots FC is assumed to be equal.

[0036] In FIG. 1, a discharge amount determination unit 63 determines the amount of ink I to be discharged from a discharge section D in the flushing process according to this embodiment.

[0037] The acquisition unit 64 acquires, from the measurement circuit 9, determination information Stt[m] indicating the result of the discharge state determination of the discharge section D[m] and phase information NtF[m] indicating the phase of the residual vibration in the discharge section D[m]. More specifically, the acquisition unit 64 acquires phase information NtF1[m] indicating the phase of the residual vibration in the discharge section D[m]. In addition, the acquisition unit 64 acquires phase information NtF2[m] indicating the phase of the residual vibration in the discharge section D[m] after the discharge control unit 62 discharges a first amount of ink I from the discharge section D[m] by executing a flushing operation once or multiple times. As described above, the phase information NtF1[m] and the phase information NtF2[m] indicate values ​​according to the viscosity of the ink I filled in the discharge section D[m]. In this embodiment, the phase information NtF1[m] is an example of the "first viscosity information", and the phase information NtF2[m] is an example of the "second viscosity information".

[0038] The generating section 65 generates difference information DF indicating the difference between the phase according to the viscosity indicated by the first phase information NtF1[m] and the phase according to the viscosity indicated by the second phase information NtF2[m].

[0039] The discharge control unit 62 again discharges the first amount of ink I from those discharge units D for which the difference indicated by the difference information DF is equal to or greater than the predetermined value. On the other hand, the discharge control unit 62 does not discharge ink I from those discharge units D for which the difference indicated by the difference information DF is less than the predetermined value.

[0040] The operations of the discharge control unit 62, the discharge amount determination unit 63, the acquisition unit 64, and the generation unit 65 will be described in detail below mainly with reference to FIGS.

[0041] 1-2: Head unit HU configuration The configuration of the head unit HU will be described below with reference to FIG.

[0042] 4 is a block diagram showing an example of the configuration of the head unit HU. As described above, the head unit HU includes the recording head HD, the switching circuit 10, and the detection circuit 20. The head unit HU also includes an internal wiring LHa to which the drive signal Com-A is supplied from the drive signal generation circuit 2, an internal wiring LHb to which the drive signal Com-B is supplied from the drive signal generation circuit 2, and an internal wiring LHs for supplying the detection signal Vout detected from the discharge portion D to the detection circuit 20.

[0043] 4, the switching circuit 10 includes M switches SWa[1] to SWa[M], M switches SWb[1] to SWb[M], M switches SWs[1] to SWs[M], and a connection state designation circuit 11 that designates the connection state of each switch. Each switch may be, for example, a transmission gate. Based on at least some of the signals of the print signal SI, latch signal LAT, change signal CH, and period designation signal Tsig supplied from the control unit 6, the connection state designation circuit 11 generates connection state designation signals SLa[1] to SLa[M] that specify the on / off state of switches SWa[1] to SWa[M], connection state designation signals SLb[1] to SLb[M] that specify the on / off state of switches SWb[1] to SWb[M], and connection state designation signals SLs[1] to SLs[M] that specify the on / off state of switches SWs[1] to SWs[M]. The switch SWa[m] switches between electrical continuity and non-conduction between the internal wiring LHa and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] in response to the connection state designation signal SLa[m]. For example, the switch SWa[m] is turned on when the connection state designation signal SLa[m] is at a high level, and turned off when the connection state designation signal SLa[m] is at a low level. The switch SWb[m] switches between electrical continuity and non-conduction between the internal wiring LHb and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] in response to the connection state designation signal SLb[m]. For example, the switch SWb[m] is turned on when the connection state designation signal SLb[m] is at a high level, and turned off when the connection state designation signal SLb[m] is at a low level. Of the drive signals Com-A and Com-B, the signal that is actually supplied to the piezoelectric element PZ[m] of the ejection section D[m] via the switch SWa[m] or SWb[m] may be referred to as the supplied drive signal Vin[m]. The switch SWs[m] switches between electrical continuity and non-conduction between the internal wiring LHs and the upper electrode Zu[m] of the piezoelectric element PZ[m] provided in the discharge section D[m] in response to the connection state designation signal SLs[m]. For example, the switch SWs[m] is turned on when the connection state designation signal SLs[m] is at a high level, and turned off when the connection state designation signal SLs[m] is at a low level.

[0044] A detection signal Vout[m] output from the piezoelectric element PZ[m] of the ejection section D[m] driven as the ejection section DH to be judged is supplied to the detection circuit 20 via an internal wiring LHs. Then, the detection circuit 20 generates a residual vibration signal NES based on the detection signal Vout[m].

[0045] 1-3: Operation of head unit HU Hereinafter, the operation of the head unit HU will be described with reference to FIGS.

[0046] In this embodiment, the operating period of the inkjet printer 1 includes one or more unit periods Tu. It is assumed that the inkjet printer 1 according to this embodiment performs one of the following in each unit period Tu: driving each ejection section D in a printing process, driving each ejection section D in a flushing process, and driving a judgment target ejection section DH and detecting residual vibration in a preparatory process for an ejection state judgment process. However, the present invention is not limited to this aspect, and it may be possible to perform both driving each ejection section D in a printing process, and driving a judgment target ejection section DH and detecting residual vibration in a preparatory process for an ejection state judgment process in each unit period Tu. Generally, an inkjet printer 1 forms an image represented by print data Img by repeatedly executing a printing process over a number of continuous or intermittent unit periods Tu to eject ink I one or more times from each ejection section D. The inkjet printer 1 according to this embodiment also executes a preparatory process for an ejection state determination process M times during M unit periods Tu that are provided continuously or intermittently, thereby executing an ejection state determination process with each of the M ejection sections D[1] to D[M] as the ejection section DH to be determined.

[0047] FIG. 5 is a timing chart illustrating the operation of the inkjet printer 1 in a unit period Tu. As shown in Fig. 5, the control unit 6 outputs a latch signal LAT having a pulse PlsL and a change signal CH having a pulse PlsC. As a result, the control unit 6 defines a unit period Tu as a period from the rising edge of the pulse PlsL to the rising edge of the next pulse PlsL. The control unit 6 also divides the unit period Tu into two control periods Tu1 and Tu2 by the pulse PlsC. The print signal SI includes individual designation signals Sd[1] to Sd[M] that designate the driving mode of the discharge sections D[1] to D[M] in each unit period Tu. When at least one of the print process and the discharge state determination process is executed in the unit period Tu, the control section 6 supplies the print signal SI including the individual designation signals Sd[1] to Sd[M] to the connection state designation circuit 11 in synchronization with the clock signal CL prior to the start of the unit period Tu, as shown in Fig. 4. In this case, the connection state designation circuit 11 generates the connection state designation signals SLa[m], SLb[m], and SLs[m] based on the individual designation signal Sd[m] in the unit period Tu.

[0048] The individual designation signal Sd[m] according to the present embodiment is a signal that designates, for each unit period Tu, one of five drive modes for the discharge section D[m]: discharge of an amount of ink I corresponding to a large dot, discharge of an amount of ink I corresponding to a medium dot, discharge of an amount of ink I corresponding to a small dot, non-discharge of ink I, and drive as a determination target in the discharge state determination process. In the following description, the amount corresponding to a large dot may be referred to as a "large amount", and the discharge of an amount of ink I corresponding to a large dot may be referred to as "formation of a large dot". Similarly, the amount corresponding to a medium dot may be referred to as a "medium amount", and the discharge of an amount of ink I corresponding to a medium dot may be referred to as "formation of a medium dot". The amount corresponding to a small dot may be referred to as a "small amount", and the discharge of an amount of ink I corresponding to a small dot may be referred to as "formation of a small dot". Drive as a determination target in the discharge state determination process may be referred to as "drive as a determination target discharge section DH". In this embodiment, as an example, it is assumed that the individual designation signal Sd[m] is a 3-bit digital signal as illustrated in FIG.

[0049] In the present invention, the "ejection of the amount of ink I equivalent to a large dot" corresponds to the flushing operation.

[0050] As shown in FIG. 5, the drive signal generating circuit 2 outputs a drive signal Com-A having a medium dot waveform PX provided in the control period Tu1 and a small dot waveform PY provided in the control period Tu2. In this embodiment, the medium dot waveform PX and the small dot waveform PY are determined so that the potential difference between the highest potential VHX and the lowest potential VLX of the medium dot waveform PX is greater than the potential difference between the highest potential VHY and the lowest potential VLY of the small dot waveform PY. Specifically, when the discharge section D[m] is driven by the drive signal Com-A having the medium dot waveform PX, the medium dot waveform PX is determined so that a medium amount of ink I is discharged from the discharge section D[m]. Also, when the discharge section D[m] is driven by the drive signal Com-A having the small dot waveform PY, the small dot waveform PY is determined so that a small amount of ink I is discharged from the discharge section D[m]. Note that the potentials of the medium dot waveform PX and the small dot waveform PY at the start and end are set to the reference potential V0.

[0051] When the individual designation signal Sd[m] designates the ejection section D[m] to form a large dot, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a high level during the control periods Tu1 and Tu2, and sets the connection state designation signals SLb[m] and SLs[m] to a low level during the unit period Tu. In this case, the ejection section D[m] is driven by the drive signal Com-A of the medium dot waveform PX during the control period Tu1 to eject a medium amount of ink I, and is driven by the drive signal Com-A of the small dot waveform PY during the control period Tu2 to eject a small amount of ink I. As a result, the ejection section D[m] ejects a large amount of ink I in total during the unit period Tu, and a large dot is formed on the recording paper Pp. Furthermore, when the individual designation signal Sd[m] designates the ejection section D[m] to form a medium dot, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a high level during the control period Tu1 and to a low level during the control period Tu2, and sets the connection state designation signals SLb[m] and SLs[m] to a low level during the unit period Tu. In this case, the ejection section D[m] ejects a medium amount of ink I during the unit period Tu, and a medium dot is formed on the recording paper Pp. Furthermore, when the individual designation signal Sd[m] designates the ejection section D[m] to form a small dot, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the control period Tu1 and to a high level in the control period Tu2, and sets the connection state designation signals SLb[m] and SLs[m] to a low level in the unit period Tu. In this case, the ejection section D[m] ejects a small amount of ink I in the unit period Tu, and a small dot is formed on the recording paper Pp. Furthermore, when the individual designation signal Sd[m] designates the ejection section D[m] not to eject ink I, the connection state designation circuit 11 sets the connection state designation signals SLa[m], SLb[m], and SLs[m] to a low level during the unit period Tu. In this case, the ejection section D[m] does not eject ink I during the unit period Tu, and does not form dots on the recording paper Pp.

[0052] As shown in FIG. 5, the drive signal generating circuit 2 outputs a drive signal Com-B having a test waveform PS provided in a unit period Tu. In this embodiment, the test waveform PS is determined so that the potential difference between the highest potential VHS and the lowest potential VLS of the test waveform PS is smaller than the potential difference between the highest potential VHY and the lowest potential VLY of the small dot waveform PY. Specifically, when the drive signal Com-B having the test waveform PS is supplied to the discharge section D[m], the test waveform PS is determined so that the discharge section D[m] is driven to such an extent that ink I is not discharged from the discharge section D[m]. Note that the potential of the test waveform PS at the start and end is set to the reference potential V0. The control unit 6 also outputs a period designation signal Tsig having a pulse PlsT1 and a pulse PlsT2, which divides the unit period Tu into a control period TSS1 from the start of the pulse PlsL to the start of the pulse PlsT1, a control period TSS2 from the start of the pulse PlsT1 to the start of the pulse PlsT2, and a control period TSS3 from the start of the pulse PlsT2 to the start of the next pulse PlsL.

[0053] Then, when the individual designation signal Sd[m] designates the emission section D[m] as the emission section DH to be judged, the connection state designation circuit 11 sets the connection state designation signal SLa[m] to a low level in the unit period Tu, sets the connection state designation signal SLb[m] to a high level in the control periods TSS1 and TSS3 and to a low level in the control period TSS2, and sets the connection state designation signal SLs[m] to a low level in the control periods TSS1 and TSS3 and to a high level in the control period TSS2. In this case, the ejection section DH to be judged is driven by the driving signal Com-B of the test waveform PS during the control period TSS1. Specifically, the piezoelectric element PZ of the ejection section DH to be judged is displaced by the driving signal Com-B of the test waveform PS during the control period TSS1. As a result, vibration occurs in the ejection section DH to be judged, and this vibration remains in the control period TSS2. Then, during the control period TSS2, the upper electrode Zu of the piezoelectric element PZ of the ejection section DH to be judged changes its potential according to the residual vibration occurring in the ejection section DH to be judged. In other words, during the control period TSS2, the upper electrode Zu of the piezoelectric element PZ of the ejection section DH to be judged shows a potential according to the electromotive force of the piezoelectric element PZ caused by the residual vibration occurring in the ejection section DH to be judged. Then, the potential of the upper electrode Zu can be detected as a detection signal Vout during the control period TSS2.

[0054] 6 is an explanatory diagram for explaining the generation of the connection state designation signals SLa[m], SLb[m], and SLs[m]. The connection state designation circuit 11 decodes the individual designation signal Sd[m] according to FIG. 6, and generates the connection state designation signals SLa[m], SLb[m], and SLs[m]. As shown in Figure 6, the individual designation signal Sd[m] in this embodiment indicates any one of the following values: a value (1,1,0) that specifies the formation of large dots, a value (1,0,0) that specifies the formation of medium dots, a value (0,1,0) that specifies the formation of small dots, a value (0,0,0) that specifies no ejection of ink I, or a value (1,1,1) that specifies driving of the ejection section DH to be judged. The connection state designation circuit 11 sets the connection state designation signal SLa[m] to a high level during control periods Tu1 and Tu2 when the individual designation signal Sd[m] indicates (1,1,0), sets the connection state designation signal SLa[m] to a high level during control period Tu1 when the individual designation signal Sd[m] indicates (1,0,0), sets the connection state designation signal SLa[m] to a high level during control period Tu2 when the individual designation signal Sd[m] indicates (0,1,0), sets the connection state designation signal SLa[m] to a high level during control period Tu2 when the individual designation signal Sd[m] indicates (1,1,1), sets the connection state designation signal SLb[m] to a high level during control periods TSS1 and TSS3, and sets the connection state designation signal SLs[m] to a high level during control period TSS2, and sets each signal to a low level when the above does not apply.

[0055] As described above, the detection circuit 20 generates the residual vibration signal NES based on the detection signal Vout. The residual vibration signal NES is a signal obtained by amplifying the amplitude of the detection signal Vout and removing noise components from the detection signal Vout, thereby shaping the detection signal Vout into a waveform suitable for processing in the measurement circuit 9. The residual vibration signal NES is an analog signal. The detection circuit 20 may be configured to include, for example, a negative feedback amplifier for amplifying the detection signal Vout, a low-pass filter for attenuating high frequency components of the detection signal Vout, and a voltage follower for converting impedance and outputting a low impedance residual vibration signal NES.

[0056] 1-4: Operation of measurement circuit 9 Next, the measurement circuit 9 will be described.

[0057] In general, the residual vibration occurring in the ejection portion D is determined by the shape of the nozzle N, the weight of the ink I filled in the cavity 320, and the viscosity of the ink I filled in the cavity 320, etc. Fig. 7 is an explanatory diagram for explaining an example of the residual vibration signal NES supplied from the detection circuit 20 to the measurement circuit 9.

[0058] 7, the detection circuit 20 outputs a residual vibration signal NES[m] during the detection period TSS. The residual vibration signal NES[m] shows a waveform based on the residual vibration of the discharge section D[m] during the detection period TSS. Specifically, the residual vibration signal NES[m] shows vibration that attenuates between the lowest potential VKL and the highest potential VKH.

[0059] In this embodiment, the measurement circuit 9 measures the amplitude VM[m] and initial time TF[m] of the residual vibration signal NES[m]. Here, the amplitude VM[m] is a value according to the amplitude of the residual vibration signal NES[m]. Specifically, in this embodiment, the residual vibration signal NES[m] is the potential difference between the highest potential VKH and the lowest potential VKL. In this embodiment, the initial time TF[m] is the time length from the start time of the detection period TSS to the time when the potential of the residual vibration signal NES[m] becomes a predetermined reference potential VK0. Here, the reference potential VK0 may be, for example, a potential that is the center of the amplitude of the residual vibration signal NES[m]. Furthermore, the measurement circuit 9 outputs phase information NtF[m] indicating the measured initial time TF[m]. In general, the initial time TF[m] has a time length according to the viscosity of the ink I in the discharge section D[m]. Therefore, in this embodiment, the phase information NtF[m] is used as viscosity information, which is information related to viscosity. Note that, as an example, in this application, a case is assumed in which the initial time TF[m] decreases as the viscosity of the ink I in the discharge section D[m] decreases.

[0060] In this embodiment, in the discharge state determination process for the discharge unit D[m], when the amplitude VM[m] satisfies the amplitude determination condition that it is equal to or greater than the threshold value VM-L and equal to or less than the threshold value VM-H, and satisfies the phase determination condition that the initial time TF[m] is equal to or greater than the threshold value TF-L and equal to or less than the threshold value TF-H, the measurement circuit 9 generates determination information Stt[m] indicating that the discharge state in the discharge unit D[m] is normal. On the other hand, when the amplitude VM[m] does not satisfy the amplitude determination condition, or when the initial time TF[m] does not satisfy the phase determination condition, the measurement circuit 9 generates determination information Stt[m] indicating that the discharge state in the discharge unit D[m] is abnormal. Note that the threshold values VM-L and VM-H are real numbers satisfying "0 < VM-L < VM-H", and the threshold values TF-L and TF-H are real numbers satisfying "0 < TF-L < TF-H".

[0061] 1-5: Ink discharge process Next, the ink discharge process according to this embodiment will be described.

[0062] Since the degree of thickening of the ink I depends on many factors such as the temperature and humidity around the discharge unit D, the type of the ink I, the variation in the nozzle diameter in the discharge unit D, and the printing pattern, it is difficult to determine the required discharge amount of the ink I according to the situation to which the discharge unit D has been exposed each time the ink discharge process is performed. For this reason, in the prior art, the amount of the ink I discharged in the ink discharge process has been determined to be a preset predetermined amount.

[0063] However, in the case of the method of discharging a preset predetermined amount of the ink I in the ink discharge process, there were the following two problems. First, the amount of water that evaporates from the ink I is affected by many factors, such as the temperature and humidity around the discharge section D and the time that has elapsed since the previous flushing process, so that in the ink discharge process in which a preset amount is discharged, the discharge amount may be excessive or insufficient depending on the conditions to which the discharge section D is exposed. For example, if the amount of ink I to be discharged in the ink discharge process is set assuming a condition in which the amount of water evaporation is the greatest so that the amount of ink I discharged in the ink discharge process is insufficient and the thickened ink I in the discharge section D cannot be discharged completely, causing a decrease in print quality in the print process after the ink discharge process, the ink I will be discharged excessively in the ink discharge process in a condition in which the amount of water evaporation is not large, resulting in a waste of the ink I. In addition, if the discharge section D is exposed to a condition in which the amount of water in the ink I in the discharge section D evaporates more than expected when the predetermined amount is set, the ink discharge amount in the ink discharge process will be insufficient, and the thickened ink I in the discharge section D will not be discharged completely, causing a decrease in print quality in the print process after the ink discharge process. Secondly, in the inkjet printer of the prior art, a flushing process is performed in which the same amount of ink I is uniformly discharged from the multiple discharge parts D included in the head unit HU. Therefore, if the amount of water evaporated from the ink I filled in each of the multiple discharge parts D differs, the amount of ink I discharged from some discharge parts D may be excessive or insufficient. For example, if the frequency of use of the multiple discharge parts D differs in the printing process before the ink discharge process, the ink I may be discharged excessively from the less frequently used discharge parts D, resulting in wasting the ink I, or the ink I may be discharged insufficiently from the more frequently used discharge parts D, resulting in a deterioration in print quality. In addition, for example, if the conditions, such as the temperature and humidity around the discharge parts D, the type of ink I, and the nozzle diameter of the discharge parts D, differ depending on the arrangement positions of the multiple discharge parts D, the ink I may be discharged excessively from the discharge parts D that have little water evaporated from the filled ink I, resulting in wasting the ink I, or the ink I may be discharged insufficiently from the discharge parts D that have much water evaporated from the filled ink I, resulting in a deterioration in print quality.

[0064] Therefore, in this embodiment, the control unit 6 increases the number of flushing operations of the ejection unit D[m] in which the amount of water evaporated from the ink I is large at the start of the ink discharge process, compared to the number of flushing operations of the ejection unit D[m] in which the amount of water evaporated from the ink I is small at the start of the ink discharge process. Specifically, the control unit 6 acquires phase information NtF[m] according to the viscosity of the ink I at each ejection unit D[m] before and after the flushing process, as described above. In addition, the control unit 6 controls, for each ejection unit D[m], whether to eject the ink I again by the flushing process or not, according to the difference between the phase indicated by the first phase information NtF1[m] acquired before the flushing process and the phase indicated by the second phase information NtF2[m] acquired after the flushing process. More specifically, the control unit 6 controls, for each ejection unit D[m], whether to further execute the flushing process consisting of multiple flushing operations or not, according to the difference between the phase information NtF[m] acquired before and after the above flushing process.

[0065] Fig. 8 is an explanatory diagram for explaining the ink discharging process for one discharge section D[k] among the multiple discharge sections D, and Fig. 9 is an explanatory diagram for explaining the ink discharging process for one discharge section D[j] other than the discharge section D[k] among the multiple discharge sections D. A case will be described below in which the amount of water evaporated from the ink I in the discharge section D[j] is less than the amount of water evaporated from the ink I in the discharge section D[k] at the start of the ink discharging process. Note that the variable k is an integer between 1 and M inclusive. The variable j is an integer between 1 and M inclusive. Specifically, Fig. 8 is a graph showing a relationship line L1 indicating the relationship between the number of flushing operations (shot number FCp) in one or more flushing processes included in the ink discharge process for the discharge section D[k] and the initial time TF[k] indicated by phase information NtF[k], which is viscosity information obtained in the discharge state determination process for the discharge section D[k] performed at the start and end of each flushing process. Fig. 9 is a graph showing a relationship line L2 indicating the relationship between the number of flushing operations (shot number FCp) in one or more flushing processes included in the ink discharge process for the discharge section D[j] and the initial time TF[j] indicated by phase information NtF[j], which is viscosity information obtained in the discharge state determination process for the discharge section D[j] performed at the start and end of each flushing process. Specifically, the horizontal axis indicates the cumulative number of flushing operations performed by the discharge section D[k] in the ink discharging process in the graph of Fig. 8, and indicates the cumulative number of flushing operations performed by the discharge section D[j] in the ink discharging process in the graph of Fig. 9. Hereinafter, this cumulative number is referred to as the cumulative shot number ΣFC. In addition, the vertical axis represents the initial time TF indicated by the phase information NtF[k] obtained in each of the multiple ejection state determination processes performed during the ink discharge process in the graph of Figure 8, and represents the initial time TF indicated by the phase information NtF[j] obtained in each of the multiple ejection state determination processes performed during the ink discharge process in the graph of Figure 9. In addition, although the relationship lines L1, L2 are shown as broken lines in FIG. 8 and FIG. 9, the relationship lines L1, L2 may be curved lines. In Fig. 8, each of the measurement points P plotted on the relation line L1 is a point on a graph plotting the cumulative shot count ΣFC corresponding to the end of each flushing process of the ink discharge process for the discharge section D[m] and the initial time TF[k] indicated by the phase information NtF[k] acquired in the discharge state determination process for the discharge section D[k] performed at the end of the flushing process. In Fig. 9, each of the measurement points P plotted on the relation line L2 is a point on a graph plotting the cumulative shot count ΣFC corresponding to the end of each flushing process of the ink discharge process for the discharge section D[j] and the initial time TF[j] indicated by the phase information NtF[j] acquired in the discharge state determination process for the discharge section D[j] performed at the end of the flushing process.

[0066] As an example, Figure 8 assumes that the ink discharge process includes five flushing processes and five ejection state determination processes, and Figure 9 assumes that the ink discharge process includes three flushing processes and three ejection state determination processes. In the following, the flushing process that is executed first in the ink discharging process is referred to as the "initial ejection operation."

[0067] First, the control unit 6 causes the multiple discharge units D to execute an initial discharge operation, which is a first flushing process. Specifically, the discharge amount determination unit 63 determines, as the discharge amount, the ink amount corresponding to the flushing process in which the cumulative shot count ΣFC is FC0. For example, the discharge amount determination unit 63 can read out, as the discharge amount, the shot count FC0 previously set for the initial discharge operation stored in the storage unit 5. The discharge control unit 62 causes the ink I to be discharged from the nozzle N by FC0 flushing operations. The initial discharge operation is an operation for discharging the ink I present at the tip of the nozzle N, which has a higher viscosity than the ink I present in other parts, in order to accurately measure the initial time TF.

[0068] Next, the acquisition unit 64 acquires the phase information NtF1[m] of each discharge unit D[m] at the current time from the measurement circuit 9. In the example of the discharge unit D[k] shown in the graph of FIG. 8, the value of the initial time TF[k] indicated by the phase information NtF1[k] at the time when the initial discharge operation is completed is TF0[k] as shown at the measurement point P0[k]. In the example of the discharge unit D[j] shown in the graph of FIG. 9, the value of the initial time TF[j] indicated by the phase information NtF1[j] at the time when the initial discharge operation is completed is TF0[j] as shown at the measurement point P0[j]. The value of the initial time TF[j] indicated by the phase information NtF1[j] of the discharge unit D[j] is shorter than the value of the initial time TF[k] indicated by the phase information NtF1[k] of the discharge unit D[k].

[0069] Next, the discharge amount determination unit 63 determines the number of shots FC corresponding to the discharge amount of the ink I discharged by one flushing process after the second flushing process. Specifically, the discharge amount determination unit 63 reads out the number of shots FCp for one flushing process after the second flushing process, which is stored in advance in the storage unit 5. The number of shots FCp for one flushing process is preset to a number of shots FC that can discharge about one-fourth of the discharge amount determined on the premise that all of the thickened ink I in the discharge section D exposed to a situation in which the moisture in the ink I evaporates more than usual can be discharged, and is stored in the storage unit 5. In addition, in the example of FIG. 8 and FIG. 9, the number of shots FC that is one-fourth of the number of shots obtained by subtracting the number of shots FC0 preset for the initial discharge operation from the number of shots corresponding to the discharge amount determined on the premise that all of the thickened ink I in the discharge section D exposed to a situation in which the moisture in the ink I evaporates more than usual can be discharged is preset to the number of shots FCp for one flushing process, and is stored in the storage unit 5.

[0070] Next, the discharge control unit 62 executes flushing operations FCp times as the second flushing process. In other words, the discharge control unit 62 causes each of the multiple discharge units D to discharge an amount of ink I corresponding to the shot number FCp. As a result, the cumulative shot number ΣFC becomes FC1.

[0071] Next, the acquisition unit 64 acquires the phase information NtF2[m] of each discharge unit D[m] at the current time from the measurement circuit 9. In the example of the discharge unit D[k] shown in the graph of Fig. 8, the value of the initial time TF[k] indicated by the phase information NtF2[k] at the time when the cumulative shot count ΣFC becomes FC1 is TF1[k] as shown at the measurement point P1[k]. In the example of the discharge unit D[j] shown in the graph of Fig. 9, the value of the initial time TF[j] indicated by the phase information NtF2[j] at the time when the cumulative shot count ΣFC becomes FC1 is TF1[j] as shown at the measurement point P1[j].

[0072] Next, the generation unit 65 generates difference information DF[m] indicating the difference |Tf0[m]-Tf1[m]| between the initial time TF0[m] indicated by the phase information NtF1[m] at the time when the first flushing process as the initial ejection operation is completed, in other words, before the start of the second flushing process, and the initial time TF1[m] indicated by the phase information NtF2[m] at the time when the second flushing process is completed, for each of the multiple ejection sections D.

[0073] The discharge control unit 62 executes flushing operations FCp times as the third flushing process for discharge sections D[m] for which the difference |Tf0[m]-Tf1[m]| indicated by the difference information DF[m] is equal to or greater than the predetermined value α. In other words, the discharge control unit 62 causes each discharge section D[m] for which the difference |Tf0[m]-Tf1[m]| is equal to or greater than the predetermined value α to discharge an amount of ink I corresponding to the shot count FCp. As a result, the cumulative shot count ΣFC for the discharge sections D[m] for which the difference |Tf0[m]-Tf1[m]| is equal to or greater than the predetermined value α becomes FC2.

[0074] On the other hand, the discharge control unit 62 does not execute the third or subsequent flushing process for a discharge section D for which the difference |Tf0[m]-Tf1[m]| indicated by the difference information DF[m] is less than the predetermined value α among the multiple discharge sections D. This is because for that discharge section D[m], even if the flushing process is executed further, there is no significant change in the viscosity of the ink I in that discharge section D[m], and it is expected that the flushing process has already been performed sufficiently. The difference |Tf0[k]-Tf1[k]| indicated by the differential information DF[k] at the ejection section D[k] shown in the graph in Figure 8 and the difference |Tf0[j]-Tf1[j]| indicated by the differential information DF[j] at the ejection section D[j] shown in the graph in Figure 9 are greater than or equal to the predetermined value α, so an amount of ink I corresponding to the shot number FCp is ejected from the ejection section D[k] and the ejection section D[j] in the third flushing process.

[0075] Next, for the discharge section D that has executed the third flushing process, the acquisition section 64 acquires the current phase information NtF[m] from the measurement circuit 9. In the example shown in the graph of Fig. 8, the value of the initial time TF[k] indicated by the phase information NtF[k] at the time when the cumulative shot count ΣFC becomes FC2 is TF2[k], as shown at the measurement point P2[k]. In the example shown in the graph of Fig. 9, the value of the initial time TF[j] indicated by the phase information NtF[j] at the time when the cumulative shot count ΣFC becomes FC2 is TF2[j], as shown at the measurement point P2[j].

[0076] Similarly, for each of the ejection sections D[m] that have performed the third flushing process, the generation section 65 generates difference information DF[m] indicating the difference |Tf1[m]-Tf2[m]| between the initial time TF1[m] indicated by the phase information NtF1[m] at the time when the second flushing process is completed, in other words, before the start of the third flushing process, and the initial time TF2[m] indicated by the phase information NtF2[m] at the time when the third flushing process is completed.

[0077] The discharge control unit 62 executes flushing operations FCp times as the fourth flushing process for discharge sections D[m] for which the difference |Tf1[m]-Tf2[m]| indicated by the difference information DF[m] is equal to or greater than the predetermined value α among the discharge sections D that have performed the third flushing process. As a result, the cumulative number of shots ΣFC for the discharge sections D for which the difference |Tf1[m]-Tf2[m]| is equal to or greater than the predetermined value α becomes FC3.

[0078] On the other hand, the discharge control unit 62 does not perform the flushing process from the fourth time onwards for any discharge section D[m] among the multiple discharge sections D where the difference |Tf1[m]-Tf2[m]| indicated by the difference information DF[m] is less than the predetermined value α. The difference |Tf1[k]-Tf2[k]| indicated by the difference information DF[k] for the ejection section D[k] shown in the graph of Fig. 8 is equal to or greater than the predetermined value α, so an amount of ink I corresponding to the number of shots FCp is ejected from the ejection section D[k] in the fourth flushing process. On the other hand, the difference |Tf0[j]-Tf1[j]| indicated by the difference information DF[j] for the ejection section D[j] shown in the graph of Fig. 9 is less than the predetermined value α, so the fourth or subsequent flushing processes are not executed in the ejection section D[j].

[0079] Next, the acquisition unit 64 acquires the initial time TF[m] indicated by the current phase information NtF[m] from the measurement circuit 9. In the example shown in the graph of Fig. 8, the value of the initial time TF[k] indicated by the phase information NtF[k] at the time when the cumulative shot count ΣFC becomes FC3 is TF3[k], as shown at the measurement point P3[k].

[0080] The generation unit 65 generates difference information DF[m] indicating the difference |Tf2[m]-Tf3[m]| between the initial time TF2[m] indicated by the phase information NtF1[m] at the time when the third flushing process is completed, in other words, at the time when the fourth flushing process is started, and the initial time TF3[m] indicated by the phase information NtF2[m] at the time when the fourth flushing process is completed, for each ejection section D[m] that has performed the fourth flushing process.

[0081] The discharge control unit 62 executes flushing operations FCp times as the fifth flushing process for the discharge section D[m] for which the difference |Tf2[m]-Tf3[m]| indicated by the difference information DF[m] is equal to or greater than the predetermined value α among the discharge sections D that have performed the fourth flushing process. As a result, the cumulative number of shots ΣFC for the discharge section D[m] for which the difference |Tf2[m]-Tf3[m]| is equal to or greater than the predetermined value α becomes FCw.

[0082] On the other hand, the discharge control unit 62 does not execute the flushing process from the fifth time onwards for a discharge section D[m] among the multiple discharge sections D, for which the difference |Tf2[m]-Tf3[m]| indicated by the difference information DF is less than the predetermined value α. Since the difference |Tf2[k]-Tf3[k]| indicated by the differential information DF[k] in the ejection section D[k] shown in the graph in Figure 8 is greater than or equal to the predetermined value α, an amount of ink I corresponding to the shot count FCp is ejected from the ejection section D[k] in the fifth flushing process.

[0083] Next, the acquisition unit 64 acquires the initial time TF[m] indicated by the current phase information NtF[m] from the measurement circuit 9. In the example shown in the graph of Fig. 8, the initial time TF[k] at the time when the cumulative shot count ΣFC becomes FCw is TFw[k], as shown at the measurement point Pw[k]. The generation unit 65 generates difference information DF[m] indicating the difference |Tf3[m]-Tfw[m]| between the initial time TF3[m] indicated by the phase information NtF1[m] at the time when the fourth flushing process is completed, in other words, at the time when the fifth flushing process is started, and the initial time TFw[m] indicated by the phase information NtF2[m] at the time when the fifth flushing process is completed, for each ejection section D[m] that has performed the fifth flushing process. The discharge control unit 62 executes flushing operations FCp times as the sixth flushing process for discharge sections D[m] for which the difference |Tf3[m]-Tfw[m]| indicated by the difference information DF is equal to or greater than the predetermined value α among the discharge sections D[m] that have undergone the fifth flushing process. As a result, the cumulative number of shots ΣFC for the discharge sections D for which the difference |Tf3[m]-Tfw[m]| is equal to or greater than the predetermined value α becomes FCp times more than the specified cumulative number of shots FCw. On the other hand, the discharge control unit 62 does not perform the flushing process from the sixth onwards for any discharge section D[m] among the multiple discharge sections D where the difference |Tf3[m]-Tfw[m]| indicated by the difference information DF[m] is less than the predetermined value α. In the ink discharge process, the cumulative number of shots ΣFC until the differential information DF[k] becomes less than the predetermined value α for the discharge section D[k] shown in the graph in Figure 8 is FCw, and in the discharge section D[j] shown in the graph in Figure 9, the cumulative number of shots ΣFC until the differential information DF[j] becomes less than the predetermined value α is FC2. In this way, in the ink discharging process according to this embodiment, if the amount of water evaporated from the ink I at the start of the ink discharging process is greater for the discharging section D[k] than for the discharging section D[j], the cumulative number of shots in the ink discharging process will be greater for the discharging section D[k] than for the discharging section D[j]. In other words, in the ink discharging process according to this embodiment, if the amount of water evaporated from the ink I at the start of the ink discharging process is less for the discharging section D[j] than for the discharging section D[k], the cumulative number of shots in the ink discharging process will be less for the discharging section D[j] than for the discharging section D[k]. In other words, the ink discharging process according to this embodiment discharges just the right amount of thickened ink from the discharging section D[m] according to the amount of water evaporated from the ink I at the discharging section D[m] at the start of the ink discharging process.

[0084] 8 and 9, the acquired value of TF decreases monotonically as the cumulative number of shots ΣFC increases, but this is merely an example. The acquired value of the initial time TF may increase monotonically as the cumulative number of shots ΣFC increases.

[0085] 8 and 9, the number of shots FCp in one flushing process is set to a quarter of the number of shots obtained by subtracting the number of shots FC0 preset for the initial discharge operation from the number of shots corresponding to the discharge amount determined on the premise that all of the thickened ink I in the discharge portion D exposed to a condition in which the moisture in the ink I evaporates more than usual can be discharged. However, the number of shots FCp in one flushing process may be set to a number of shots FC that is equal to or more than a quarter of the number of shots obtained by subtracting the number of shots FC0 preset for the initial discharge operation from the number of shots corresponding to the discharge amount determined on the premise that all of the thickened ink I in the discharge portion D exposed to a condition in which the moisture in the ink I evaporates more than usual can be discharged.

[0086] 8 and 9, the amount of ink I ejected from the ejection section D by FCp flushing operations is an example of the “first amount.” In addition, during the initial ejection operation, the amount of ink I ejected from the ejection section D by FC0 flushing operations is less than the first amount.

[0087] FIG. 10 is a flowchart showing the operation of the control unit 6.

[0088] In step S1, the control unit 6 causes the discharge unit D to execute an initial discharge operation. Specifically, the discharge amount determination unit 63 reads out the shot count FC0 times from the memory unit 5 as the discharge amount of the initial discharge operation. In addition, the discharge control unit 62 causes the discharge unit D to discharge ink I by performing FC0 flushing operations.

[0089] In step S2, the acquisition section 64 acquires the phase information NtF1[m] from the measurement circuit 9.

[0090] In step S3, the discharge amount determination unit 63 reads out the number of shots FCp from the storage unit 5 as the discharge amount for one flushing process.

[0091] In step S4, the discharge control unit 62 executes the flushing operation FCp times.

[0092] In step S5, the acquisition section 64 acquires the phase information NtF2 from the measurement circuit 9.

[0093] In step S6, the generating unit 65 generates difference information DF indicating the difference ΔTF between the initial time TF indicated by the phase information NtF1 acquired before the flushing process executed in this step S4 and the initial time TF indicated by the phase information NtF2 acquired after the flushing process. For the discharge units D whose difference ΔTF is less than the predetermined value α, i.e., for the discharge units D whose result is YES in step S6, the control unit 6 ends the series of processes. For the discharge units D whose difference ΔTF is equal to or greater than the predetermined value α, i.e., for the discharge units D whose result is NO in step S6, the control unit 6 rewrites the value of the phase information NtF1 to the current phase information NtF2 in step S7, returns to step S4, and executes the flushing process.

[0094] 1-6: Advantages of the First Embodiment The maintenance method according to the present embodiment is a maintenance method for an inkjet printer 1 as a liquid ejection device that includes a plurality of ejection sections D that eject ink I as a liquid. The maintenance method acquires first phase information NtF1 related to the viscosity of the ink I filled in each of the plurality of ejection sections D. The maintenance method also causes each of the plurality of ejection sections D to eject a first amount of ink I. The maintenance method also acquires second phase information NtF2 related to the viscosity of the ink I filled in each of the plurality of ejection sections D. The maintenance method also generates difference information DF indicating the difference between the phase corresponding to the viscosity indicated by the first phase information NtF1 and the phase corresponding to the viscosity indicated by the second phase information NtF2 in each of the plurality of ejection sections D. The maintenance method also causes the first amount of ink I to be ejected again from the ejection sections D among the plurality of ejection sections D, where the difference indicated by the difference information DF is equal to or greater than a predetermined value α. The maintenance method also does not cause the ejection sections D among the plurality of ejection sections D, where the difference indicated by the difference information DF is less than a predetermined value, to eject ink I.

[0095] Therefore, the maintenance method can suppress excess or deficiency in the amount of liquid ejected during the ink discharging process. Specifically, the maintenance method repeats the flushing process until the difference in viscosity of the ink I in the ejection section D before and after the flushing process in which a first amount of ink I is ejected becomes less than a predetermined value α, so that, for example, the cumulative number of flushing operations during the ink discharging process in the ejection section D in which the viscosity of the ink I in the ejection section D at the start of the ink discharging process is thicker than the normal viscosity of the ink I in the ejection section D at the start of the ink discharging process is greater than the cumulative number of flushing operations during the ink discharging process in the ejection section D in which the viscosity of the ink I in the ejection section D at the start of the ink discharging process is close to the normal viscosity. As a result, the maintenance method can execute the ink discharging process in which an appropriate amount of ink I is ejected depending on the viscosity of the ink I in the ejection section D. Here, there is also a method of repeating the flushing process until the viscosity of the ink I detected after the flushing process reaches a preset reference viscosity. However, for example, the viscosity of the ink I supplied to the discharge section D may change due to the environmental temperature, etc., so even if a certain reference viscosity is compared with the viscosity of the ink I in the discharge section D after the flushing process, it may not be possible to accurately determine whether the ink I in the discharge section D has been replaced with the supplied ink I. On the other hand, in the ink discharge process of this embodiment, the flushing process is repeated until the difference in viscosity of the ink I in the discharge section D before and after the flushing process in which the first amount of ink I is discharged becomes less than a predetermined value α, so that it is possible to easily and accurately determine whether the thickened ink I in the discharge section D has been replaced with the supplied ink I.

[0096] Moreover, in the maintenance method, before ejecting the first amount of ink I from each of the plurality of ejection sections D, an amount of ink I smaller than the first amount is ejected from each of the plurality of ejection sections D.

[0097] Therefore, this maintenance method can accurately measure the initial time TF by discharging the ink I that is present at the tip of the nozzle N at the start of maintenance and has a higher viscosity than the ink I present in other parts.

[0098] The inkjet printer 1 as a liquid ejection device according to this embodiment includes a plurality of ejection sections D, an acquisition section 64, an ejection control section 62, and a generation section 65. The plurality of ejection sections D eject ink I as a liquid. The acquisition section 64 acquires phase information NtF relating to the viscosity of the ink I filled in each of the plurality of ejection sections D. The ejection control section 62 causes each of the plurality of ejection sections D to eject the ink I. When the acquisition section 64 acquires first phase information NtF1 corresponding to the viscosity of the ink I filled in each of the plurality of ejection sections D, and the ejection control section 62 ejects a first amount of ink I from each of the plurality of ejection sections D, the generation section 65 generates difference information DF indicating a difference between a phase corresponding to the viscosity indicated by the first phase information NtF1 and a phase corresponding to the viscosity indicated by the second phase information NtF2. The discharge control unit 62 causes the first amount of ink I to be discharged again from those discharge sections D for which the difference indicated by the difference information DF is equal to or greater than the predetermined value α. The discharge control unit 62 does not cause the ink I to be discharged from those discharge sections D for which the difference indicated by the difference information DF is less than the predetermined value α.

[0099] As a result, the inkjet printer 1 can prevent an excess or deficiency in the amount of liquid ejected during the ink discharging process. Specifically, the inkjet printer 1 repeats the flushing process until the difference in the viscosity of the ink I in the ejection section D before and after the flushing process in which a first amount of ink I is ejected becomes less than a predetermined value α, so that, for example, the cumulative number of flushing operations during the ink discharging process in an ejection section D in which the viscosity of the ink I in the ejection section D at the start of the ink discharging process is higher than the cumulative number of flushing operations during the ink discharging process in an ejection section D in which the viscosity of the ink I in the ejection section D at the start of the ink discharging process is closer to a normal state. As a result, the inkjet printer 1 can execute an ink discharging process that ejects an appropriate amount of ink I depending on the viscosity of the ink I in the ejection section D. Furthermore, a method of repeating the flushing process until the difference in viscosity of ink I in the ejection section D before and after the flushing process that ejects a first amount of ink I becomes less than a predetermined value α makes it easier and more accurate to determine whether the thickened ink I in the ejection section D is being replaced by the supplied ink I than a method of repeating the flushing process until the viscosity of ink I detected after the flushing process reaches a preset reference viscosity.

[0100] 2: Second embodiment In this embodiment, the liquid ejection device will be described by taking as an example an inkjet printer 1A that ejects ink I to form an image on recording paper Pp. The inkjet printer 1A is an example of a "liquid ejection device." To simplify the explanation below, the differences between the inkjet printer 1A according to this embodiment and the inkjet printer 1 according to the first embodiment will be mainly described. Furthermore, among the components of the inkjet printer 1A, the same components as those of the inkjet printer 1 will be denoted by the same reference numerals, and a description of their functions may be omitted.

[0101] 2-1: Overview of the Inkjet Printer 1A The configuration of an inkjet printer 1A according to this embodiment will be described with reference to Fig. 11. Here, Fig. 11 is a functional block diagram showing an example of the configuration of an inkjet printer 1A according to this embodiment.

[0102] The inkjet printer 1A has a control unit 6A instead of the control unit 6 provided in the inkjet printer 1.

[0103] The control unit 6A executes a control program stored in the memory unit 5 and operates in accordance with the control program, thereby functioning as a drive control unit 61, an ejection control unit 62, an ejection amount determination unit 63, an acquisition unit 64, and a generation unit 65, as well as a selection unit 66.

[0104] The selection unit 66 selects, from among the discharge units D, a sample discharge unit DS which is a discharge unit D to be a sample.

[0105] 2-2: Ink discharge process Next, the ink discharging process according to this embodiment will be described.

[0106] The ink discharging process of this embodiment differs from the ink discharging process of the first embodiment in that a preparatory operation is carried out. Fig. 12 is an explanatory diagram for explaining the preparatory operation for one sample discharge section DS[m]. Fig. 12 is a graph showing a relation line L3 indicating the relationship between the number of flushing operations (number of shots) in each of one or more flushing processes included in the preparatory operation for the sample discharge section DS, similar to Fig. 8 and Fig. 9, and the initial time TF indicated by phase information NtF, which is viscosity information obtained in the discharge state determination process for the discharge section DS performed at the start and end of each flushing process. The shot count FCq, which corresponds to the amount of ink I discharged by one flushing process of the preparation operation for the sample discharge section DS, is set to a shot count FC that can discharge an amount of ink I that is about 1 / 15 of the prescribed cumulative shot count FCw, which corresponds to the amount of ink I discharged, on the assumption that all of the thickened ink I in the discharge section D exposed to a condition in which the water in the ink I evaporates more than usual, can be discharged. Also, in the example shown in Fig. 12, the acquisition section 64 does not necessarily acquire the initial time TF indicated by the phase information NtF in all flushing processes from the cumulative shot count ΣFC=FC0 to the cumulative shot count ΣFC=FCw. Note that, although the relationship line L3 is shown as a broken line in Fig. 12, the relationship line L3 may be a curved line.

[0107] In the graphs shown in Figures 8 and 9, as the cumulative shot count ΣFC increases, the value of the initial time TF indicated by the acquired phase information NtF decreases monotonically. On the other hand, in the graph shown in Figure 12, as the cumulative value of the shot count FC increases, the value of the initial time TF indicated by the acquired phase information NtF increases and decreases. This phenomenon is seen when the viscosity distribution of the ink I in the ejection section D is not uniform.

[0108] FIG. 13 is a schematic diagram of the discharge section D shown in FIG. 3. FIG. 13 shows a state in which the ink I in the discharge section D has different viscosities for each layer. As a result of settling of the components of the ink I in the discharge section D when the inkjet printer 1A is left unattended, absorption of moisture into the ink I from around the nozzle N, and evaporation of moisture from the ink I to around the nozzle N, the distribution of the viscosity of the ink I in the discharge section D becomes non-uniform. In FIG. 13, the difference in viscosity is indicated by the shade of color. When the ink discharge process is performed in such a state in which the viscosity of the ink I in the discharge section D is non-uniform, the value of the acquired phase information NtF increases and decreases as the cumulative number of shots ΣFC increases.

[0109] When a flushing process is performed when the viscosity of the ink I in such an ejection section D is not uniform, and whether or not to further execute the flushing process is controlled depending on the difference between the phase information NtF1 and the phase information NtF2 obtained before and after the flushing process, there may be a case where the ink is not fully discharged during the ink discharge process. Here, as an example, in FIG. 12, when the cumulative shot count ΣFC becomes FC1, the value of the initial time TF indicated by the phase information NtF acquired by the acquisition unit 64, TF1, is assumed to be the phase information NtF1. Next, when the cumulative shot count ΣFC becomes FC3, the value of the initial time TF indicated by the phase information NtF acquired by the acquisition unit 64, TF3, is assumed to be the phase information NtF2. At the initial time TF3, the ink I with increased viscosity still remains in the discharge section D. However, in the discharge section D where the difference |TF1-TF3| between TF1 and TF3 is less than a predetermined value α, the discharge control section 62 does not execute any further flushing process even though the ink I near the nozzle N has not been refreshed. As a result, problems with print quality such as uneven printing and misaligned landing points of ink I droplets occur.

[0110] Therefore, the inkjet printer 1A according to this embodiment executes a preparatory operation after the execution of the initial discharge operation and the acquisition of phase information NtF1 at the time of completion of the initial discharge operation, as in the first embodiment, and before the execution of the ink discharge process in which the flushing process for discharging the amount of ink I corresponding to a certain number of shot counts FCr is repeated until the difference ΔTF becomes less than a predetermined value α. In the preparatory operation, first, the selection unit 66 selects a sample discharge unit DS from among the multiple discharge units D. Next, the sample discharge unit DS discharges the ink I by the flushing process in an amount corresponding to the shot count FCq, and the discharge control unit 62 acquires phase information NtF according to the viscosity of the ink I filled in the sample discharge unit DS, multiple times. As a result, the acquisition unit 64 acquires relationship information regarding the relationship between the cumulative amount of ink I discharged from the sample discharge unit DS and the viscosity, which is indicated by the relationship line L3 passing through the measurement points P0 to Pw in FIG. 12. More specifically, the acquisition unit 64 acquires relationship information regarding the relationship between the cumulative shot count ΣFC, which corresponds to the cumulative amount of ink I ejected from the sample ejection unit DS, and the initial time TF, which corresponds to the viscosity. The ejection amount corresponding to the shot count FCq is an example of the "third amount." The third amount is smaller than the first amount. It is preferable that the third amount is 20% or less of the first amount. The smaller the third amount, the more precise the relationship information that can be acquired, but the time required to acquire the relationship information increases.

[0111] Next, the discharge amount determination unit 63 determines the discharge amount of ink I to be discharged by the remaining discharge units DR, excluding the sample discharge unit DS, among the multiple discharge units D in the preparation operation, based on the relationship information acquired by the acquisition unit 64. Specifically, the discharge amount determination unit 63 identifies the cumulative shot count ΣFC corresponding to the change points where the initial time TF becomes maximum and minimum on the relationship line L3 shown in Fig. 12. The measurement points where the initial time TF becomes maximum and minimum are hereinafter referred to as "change points."

[0112] In other words, the relationship information is information that indicates the one-to-one relationship between the cumulative shot number ΣFC, which corresponds to the cumulative amount of ink I ejected from the sample ejection section DS, and the viscosity of ink I filled into the sample ejection section DS, at each of a number of timings arranged in order of increasing cumulative shot number ΣFC of the sample ejection section DS during preparatory operation.

[0113] Moreover, the change point where the initial time TF becomes the maximum is the second timing when, among the above-mentioned multiple timings, the viscosity corresponding to the second timing is higher than the viscosity corresponding to the first timing and higher than the viscosity corresponding to the third timing among three consecutive timings. In the graph of FIG. 12, as an example, the initial time TF5 corresponding to the viscosity at the timing of the measurement point P5 is longer than the initial time TF4 corresponding to the viscosity at the timing of the measurement point P4 preceding the timing of the measurement point P5. Also, the initial time TF5 corresponding to the viscosity at the timing of the measurement point P5 is longer than the initial time TF6 corresponding to the viscosity at the timing of the measurement point P6 following the timing of the measurement point P5. Therefore, the measurement point P5 is the change point where the maximum occurs. Similarly, the measurement point P8 is also the change point where the maximum occurs.

[0114] Moreover, the change point where the initial time TF becomes the minimum is the second timing when, among the above-mentioned multiple timings, the viscosity corresponding to the second timing is lower than the viscosity corresponding to the first timing and is also lower than the viscosity corresponding to the third timing among the three consecutive timings. In the graph of FIG. 12, the initial time TF2 corresponding to the viscosity at the timing of the measurement point P2 is shorter than the initial time TF1 corresponding to the viscosity at the timing of the measurement point P1 preceding the timing of the measurement point P2. Moreover, the initial time TF2 corresponding to the viscosity at the timing of the measurement point P2 is shorter than the initial time TF3 corresponding to the viscosity at the timing of the measurement point P3 following the timing of the measurement point P2. Therefore, the measurement point P2 is a change point. Similarly, the measurement point P7 is also a change point where the viscosity becomes the minimum.

[0115] As described above, the discharge amount determination unit 63 identifies the measurement point P, which is the change point, by comparing the initial times TF corresponding to the viscosities at successive timings based on the relationship information. In the entire relationship line L3 shown in FIG. 12, the measurement points P2, P5, P7, and P8 are change points. Here, the measurement point P2 is called "change point M1". The measurement point P5 is called "change point M2". The measurement point P7 is called "change point M3". The measurement point P8, which is the last change point, is called "final change point LM". When the change points M1, M2, M3, and LM are arranged so that the cumulative shot counts ΣFC corresponding to each change point increase in order, one of the two consecutive change points is called "first change point" and the other change point is called "second change point".

[0116] Next, the ejection amount determination unit 63 determines the ejection amount for each flushing process of the remaining ejection sections DR so that the flushing process ends at the timing corresponding to the identified change point M1, change point M2, change point M3, and final change point LM. In the example shown in FIG. 12, the ejection amounts for each flushing process of the remaining ejection sections DR are set as shown in FIG. The table in FIG. 14 shows the number of shots FC in the n-th flushing process. Here, n is a natural number. More specifically, FIG. 14 shows the number of shots FCq in the second to fifth flushing processes in the preparatory operation of the remaining dischargers DR among the multiple dischargers D, and the number of shots FCr in a certain number of flushing processes similar to those in the first embodiment from the sixth flushing process onwards. Here, the position and number of change points appearing on the relation line L3 differ depending on the relation information obtained by the preparatory operation of the sample discharger DS, and accordingly, the number of flushing processes in the preparatory operation performed by the remaining dischargers DR and the number of shots FCq of each flushing process differ. 14, the initial discharge operation, which is the first flushing process, is omitted. The discharge amount determination unit 63 sets the shot number FC of 2FCq times corresponding to the accumulated amount of ink I corresponding to the section from the accumulated shot number ΣFC=FC0 at the end of the initial discharge operation to the accumulated shot number ΣFC=FC2 at the change point M1, as the shot number FCq of the second flushing process of the remaining discharge section DR. The discharge amount determination unit 63 sets the shot number FC of 3FCq times corresponding to the accumulated amount of ink I corresponding to the section from the accumulated shot number ΣFC=FC2 at the change point M1 to the accumulated shot number ΣFC=FC5 at the change point M2, as the shot number FCq of the third flushing process of the remaining discharge section DR. The discharge amount determination unit 63 sets the shot number FC of 2FCq times corresponding to the accumulated amount of ink I corresponding to the section from the accumulated shot number ΣFC=FC5 at the change point M2 to the accumulated shot number ΣFC=FC7 at the change point M3, as the shot number FCq of the fourth flushing process of the remaining discharge section DR. The discharge amount determination unit 63 sets the shot number FC of the remaining discharge section DR to FCq, which corresponds to the accumulated amount of ink I corresponding to the section from the accumulated shot number ΣFC=FC7 at the change point M3 to the accumulated shot number ΣFC=FC8 at the final change point LM, as the shot number FCq of the fifth flushing process of the remaining discharge section DR. Each of the accumulated amounts of ink I discharged from the remaining discharge section DR in each of the second to fifth flushing processes is an example of the "second amount."

[0117] Furthermore, the discharge amount determination unit 63 sets a certain number of shots FCr as the number of shots FC of the sixth and subsequent flushing processes after the completion of the preparatory operations of the remaining dischargers DR, as in the first embodiment. Specifically, in the example shown in FIG. 12, the discharge amount determination unit 63 sets the number of shots FCr of the sixth and subsequent flushing processes to a quarter of the number of shots FC of the shots FC corresponding to the cumulative amount of ink I corresponding to the section from the cumulative number of shots ΣFC=FC8 to the specified cumulative number of shots FCw. However, the discharge amount determination unit 63 may set the number of shots FCr of the sixth and subsequent flushing processes to a value obtained by dividing the number of shots FC corresponding to the cumulative amount of ink I corresponding to the section from the cumulative number of shots ΣFC=FC8 to the specified cumulative number of shots FCw into a number of three or less, a value obtained by dividing into a number of five or more, or a value arbitrarily set in advance. In the example shown in FIG. 12, the discharge amount of ink I discharged for each flushing process from the sixth and subsequent flushing processes is an example of the "first amount".

[0118] In addition, if there is no change point where the change in viscosity becomes a maximum or minimum on the relationship line showing the relationship between the cumulative amount indicated by the relationship information and the viscosity, the discharge amount determination unit 63 sets the number of shots FC in one flushing process of the remaining discharge section DR during the above-mentioned preparatory operation to the same number of shots FC as the number of shots FCr in one flushing process after the preparatory operation. However, if there is no change point in the relation line indicated by the relation information, the shot number FC in one flushing process of the remaining discharge section DR may be determined based on the specified cumulative shot number FCw, as in the first embodiment. For example, if there is no change point in the relation line indicated by the relation information, the shot number FC of one quarter of the specified cumulative shot number FCw may be set as the shot number FC in one flushing process of the remaining discharge section DR. In this case, the shot number FC of one quarter of the specified cumulative shot number FCw is an example of the "first amount". Also, for example, if there is no change point in the relation line indicated by the relation information, the shot number FC of one quarter of the shot number obtained by subtracting the shot number FC0 from the specified cumulative shot number FCw may be set as the shot number FC in one flushing process of the remaining discharge section DR. In this case, the shot number FC of one quarter of the shot number obtained by subtracting the shot number FC0 from the specified cumulative shot number FCw is an example of the "first amount".

[0119] Next, the discharge control unit 62 executes the flushing operation 2FCq times as the second flushing process for the remaining discharge sections DR. Next, the acquisition section 64 acquires, from the measurement circuit 9, the phase information NtF2[m] of the remaining discharge section DR[m] at the current time. Next, the generation unit 65 generates difference information DF[m] indicating the difference |Tf0[m]-Tf2[m]| between the initial time TF0[m] indicated by the phase information NtF1[m] at the time when the first flushing process as the initial ejection operation is completed, in other words, before the start of the second flushing process, and the initial time TF2[m] indicated by the phase information NtF2[m] at the time when the second flushing process is completed. The discharge control unit 62 performs 3FCq flushing operations as the third flushing process for the remaining discharge sections DR for which the difference |Tf0[m]-Tf2[m]| indicated by the difference information DF[m] is greater than or equal to the predetermined value α, while not performing the third or subsequent flushing processes for the remaining discharge sections DR for which the difference |Tf0[m]-Tf2[m]| indicated by the difference information DF[m] is less than the predetermined value α. Next, for the remaining discharge sections DR that have executed the third flushing process, the acquisition section 64 acquires the current phase information NtF[m] from the measurement circuit 9. Similarly, difference information DF[m] indicating the difference between the initial time TF indicated by the phase information NtF1[m] obtained before and after the nth flushing process and the initial time TF indicated by the phase information NtF2[m] is generated, and for the discharge section D[m] where the difference indicated by the difference information DF[m] is greater than or equal to a predetermined value α, the n+1th flushing process is executed, while for the discharge section D[m] where the difference is less than the predetermined value α, the n+1th or subsequent flushing processes are not executed.

[0120] In this embodiment, in the preparatory operation where "n≦5", for the remaining ejection sections DR, if the difference between the initial time TF indicated by the phase information NtF1[m] and the initial time TF indicated by the phase information NtF2[m] obtained before and after the nth flushing process is less than a predetermined value α, the flushing process from the n+1th onwards is not performed for the ejection section D[m], but the present invention is not limited to this form. For example, in the preparatory operation where "n≦5", the flushing process from the n+1th time onwards may be performed on the remaining discharge sections DR for which the difference between the initial time TF indicated by the phase information NtF1[m] and the initial time TF indicated by the phase information NtF2[m] obtained before and after the nth flushing process is less than a predetermined value α. Also, for example, in the preparatory operation where "n≦5", the phase information NtF[m] may not be obtained before and after the nth flushing process for the remaining discharge sections DR. In other words, in the ink discharge process, the sixth or subsequent flushing process may be performed on the remaining discharge sections DR on the premise that all preparatory operations for the remaining discharge sections DR are completed. Even in this case, when "n≧6", for the remaining ejection sections DR, if the difference between the initial time TF indicated by the phase information NtF1[m] and the initial time TF indicated by the phase information NtF2[m] obtained before and after the nth flushing process is less than a predetermined value α, the flushing process from the n+1th onwards will not be performed for the ejection section D[m].

[0121] FIG. 15 is a flowchart showing the operation of the control unit 6A.

[0122] In step S11, the control unit 6A causes the discharge section D to execute an initial discharge operation, which is a first flushing process, and sets the variable n to 2. Specifically, the discharge amount determination unit 63 reads out the number of shots FC0 from the storage unit 5 as the discharge amount of the initial discharge operation. Furthermore, the discharge control unit 62 causes the discharge section D to discharge ink I by FC0 flushing operations.

[0123] In step S12, the acquisition unit 64 acquires the initial time TF[m] for the discharge section D[m] from the measurement circuit 9 as phase information NtF1[m], and stores the current cumulative shot count ΣFC[m] and the acquired initial time TF[m] in the memory unit 5.

[0124] In step S13, the selection unit 66 selects a sample discharge unit DS from the multiple discharge units D.

[0125] In step S14, the discharge amount determination unit 63 reads out the shot count FCq from the memory unit 5 as the discharge amount of the sample discharge portion DS, and the discharge control unit 62 executes a flushing process consisting of flushing operations FCq times for the sample discharge portion DS. Here, the amount of ink I discharged by the shot count FC=FCq is an example of the "third amount". In step S15, after the flushing process of step S14, the acquisition unit 64 acquires phase information NtF indicating the initial time TF for the sample discharging portion DS from the measurement circuit 9, and stores the current cumulative shot count ΣFC of the sample discharging portion DS and the acquired initial time TF in the memory unit 5.

[0126] In step S16, it is determined whether the cumulative shot count ΣFC of the sample discharge section DS has reached the prescribed cumulative shot count FCw. If the cumulative shot count ΣFC of the sample discharge section DS has reached the prescribed cumulative shot count FCw, i.e., if the answer is YES in step S16, the control section 6A executes the process of step S17. If the cumulative shot count ΣFC of the sample discharge section DS is below the prescribed cumulative shot count FCw, i.e., if the answer is NO in step S16, the control section 6A executes the process of step S14.

[0127] In step S17, the control unit 6A acquires relationship information regarding the relationship between the cumulative amount of ink I ejected from the sample ejection section DS and the viscosity based on the cumulative shot count ΣFC for the sample ejection section DS and the corresponding initial time TF stored in the memory unit 5.

[0128] In step S18, the discharge amount determination unit 63 determines the shot count FCq corresponding to the discharge amount of ink I to be discharged in the flushing process during the preparatory operation by the remaining discharge units DR excluding the sample discharge unit DS among the multiple discharge units D, based on the relationship information acquired in step S17, and stores the determined shot count FCq in the storage unit 5. In this embodiment, as described with reference to Fig. 14, the discharge amount determination unit 63 determines the shot counts FCq and FCr in each of the second and subsequent flushing processes of the remaining discharge units DR.

[0129] In step S19, the control unit 6A executes the flushing process corresponding to the n-th flushing process stored in the storage unit 5 for the remaining discharge sections DR.

[0130] In step S20, the acquisition unit 64 acquires, from the measurement circuit 9, the phase information NtF2[m] of the remaining discharge sections DR[m].

[0131] In step S21, the generating unit 65 generates difference information DF indicating the difference ΔTF between the initial time TF[m] indicated by the phase information NtF1[m] acquired before the n-th flushing process and the initial time TF[m] indicated by the phase information NtF2[m] acquired after the n-th flushing process for the remaining discharge section DR[m]. Then, it is determined whether the difference ΔTF indicated by the difference information DF is less than a predetermined value α. For the remaining discharge section DR[m] whose difference ΔTF is less than the predetermined value α, that is, the remaining discharge section DR[m] whose result is YES in step S21, the control unit 6A ends the series of processes. For the remaining discharge section DR[m] whose difference ΔTF is equal to or greater than the predetermined value α, that is, the remaining discharge section DR[m] whose result is NO in step S21, the control unit 6A rewrites the value of the phase information NtF1[m] to the current phase information NtF2[m] in step S22, increases the value of the variable n from the current value by 1, and returns to step S19.

[0132] 2-3: Advantages of the Second Embodiment In the maintenance method according to the present embodiment, a preparatory operation is performed before a first amount of ink I as a liquid is ejected from each of the multiple ejection units D. The preparatory operation selects a sample ejection unit DS from the multiple ejection units D. The preparatory operation acquires relationship information regarding the relationship between the cumulative amount of ink I ejected from the sample ejection unit DS during the preparatory operation and the viscosity by repeating the acquisition of phase information NtF regarding the viscosity of the ink I filled in the sample ejection unit DS and the ejection of the ink I from the sample ejection unit DS multiple times. The preparatory operation also determines a second amount, which is the ejection amount of ink I to be ejected by the remaining ejection units DR in the preparatory operation, based on the relationship information. The preparatory operation also ejects the second amount of ink I from the remaining ejection units DR among the multiple ejection units D.

[0133] Therefore, this maintenance method can eject an appropriate amount of ink I according to the viscosity state of the ink I in the ejection portion D even if the viscosity distribution of the ink I in the ejection portion D is not uniform.

[0134] In addition, in this maintenance method, the second amount is the difference in the accumulated amount at each of the successive first and second change points where the viscosity becomes maximum or minimum on the relationship line showing the relationship between the accumulated amount and the viscosity indicated by the relationship information.

[0135] Therefore, this maintenance method can eject an appropriate amount of ink I according to the viscosity state of the ink I in the ejection portion D even if the viscosity distribution of the ink I in the ejection portion D is not uniform.

[0136] In addition, in the maintenance method, when acquiring the related information in the preparation operation, acquisition of phase information NtF from the sample ejection part DS and ejection of a third amount of ink I as the liquid are repeatedly performed. In the maintenance method, the third amount is smaller than the first amount.

[0137] Therefore, this maintenance method can generate detailed relationship information. Furthermore, this maintenance method can eject a more appropriate amount of ink I in accordance with the viscosity state of the ink I in the ejection portion D based on the relationship information.

[0138] In addition, the maintenance method sets the second amount to the first amount when there is no change point where the viscosity becomes maximum or minimum on the relationship line indicating the relationship between the cumulative amount and the viscosity indicated by the relationship information.

[0139] Therefore, in the case where the above-mentioned relation line does not have a change point where the viscosity becomes maximum or minimum, the maintenance method can simplify the preparation operation.

[0140] Moreover, in the maintenance method, before the preparation operation, ink I is ejected from each of the multiple ejection sections D in an amount smaller than the first amount.

[0141] Therefore, this maintenance method can accurately measure the initial time TF by discharging the ink I that is present at the tip of the nozzle N and has a higher viscosity than the ink I that is present in other parts.

[0142] 3: Third embodiment In this embodiment, the liquid ejection device will be described by taking as an example an inkjet printer 1B that ejects ink I to form an image on recording paper Pp. The inkjet printer 1B is an example of a "liquid ejection device." To simplify the explanation below, the differences between the inkjet printer 1B according to this embodiment and the inkjet printer 1A according to the second embodiment will be mainly described. Furthermore, among the components provided in the inkjet printer 1B, the same components as those provided in the inkjet printer 1 will be denoted by the same reference numerals, and a description of their functions may be omitted.

[0143] 3-1: Overview of the Inkjet Printer 1B The configuration of the inkjet printer 1B according to this embodiment is basically the same as the configuration of the inkjet printer 1A according to the second embodiment, so a functional block diagram similar to that of FIG. 11 and its description will be omitted.

[0144] 3-2: Ink discharge process Next, the ink discharging process according to this embodiment will be described.

[0145] In the ink discharge process of the second embodiment, the amount of ink I ejected in the flushing process performed by the remaining ejection sections DR other than the sample ejection section DS is determined based on all of the change points where the initial time TF becomes maximum or minimum on the relationship line showing the relationship between the cumulative shot count ΣFC corresponding to the cumulative amount of ink I ejected from the sample ejection section DS and the initial time TF corresponding to the viscosity, as shown by the relationship information regarding the relationship between the cumulative amount of ink I ejected from the sample ejection section DS and the viscosity.

[0146] On the other hand, in the ink discharge process according to this embodiment, the discharge amount determination unit 63 determines the discharge amount of ink I to be discharged in the flushing process performed by the remaining discharge units DR other than the sample discharge unit DR based on the final change point LM among all change points at which the initial time TF becomes maximum or minimum on the relationship line showing the relationship between the number of shots FC, which corresponds to the accumulated amount of ink I indicated by the relationship information, and the initial time TF, which corresponds to the viscosity.

[0147] The discharge amount determination unit 63 determines the amount of ink I to be discharged by the remaining discharge units DR, excluding the sample discharge unit DS, among the multiple discharge units D, in the preparatory operation, based on the relationship information acquired by the acquisition unit 64. Specifically, similar to the second embodiment, the discharge amount determination unit 63 identifies the cumulative shot count ΣFC corresponding to the change points at which the initial time TF becomes maximum and minimum on the relationship line L3 shown in Fig. 12. The discharge amount determination unit 63 identifies the cumulative shot count ΣFC=FC8 corresponding to the final change point LM, which is the largest among the cumulative shot counts ΣFC corresponding to the identified change points. FIG. 16 is a table showing the number of shots FC in the n-th flushing process for the discharge section D other than the sample discharge section DS in the example shown in FIG. 12 in the third embodiment. The discharge amount determination unit 63 determines the number of shots FC=8FCq from the cumulative number of shots ΣFC=FC0 corresponding to the measurement point P0 at the end of the initial discharge operation to the cumulative number of shots ΣFC=FC8 corresponding to the final change point LM in the graph illustrated in FIG. 12 as the number of shots FCq in the second flushing process of the remaining discharge sections DR. After that, the discharge control unit 62 sets the number of shots FCr of the flushing process after the end of the preparatory operation of the remaining discharge sections DR to a value obtained by dividing the number of shots FC from the cumulative number of shots ΣFC=FC8 to the specified cumulative number of shots FCw into an arbitrary number as in the second embodiment, or to a number of shots FC corresponding to a value arbitrarily set in advance. The discharge amount of the ink I discharged for each flushing process executed after the end of the preparatory operation is an example of the "first amount".

[0148] The amount of ink I ejected from the remaining ejection section DR by the second flushing operation performed by the remaining ejection section DR in the preparatory operation is an example of a "second amount," and the amount of ink I ejected from the remaining ejection section DR for each flushing process performed after the preparatory operation is completed is an example of a "first amount."

[0149] Thereafter, the discharge control unit 62 executes the flushing operation 8FCq times as the second flushing process in the remaining discharge sections DR. Next, the acquisition section 64 acquires, from the measurement circuit 9, the phase information NtF2[m] of the remaining discharge section DR[m] at the current time. Next, the generation unit 65 generates difference information DF[m] indicating the difference |Tf0[m]-Tf8[m]| between the initial time TF0[m] indicated by the phase information NtF1[m] at the time when the first flushing process as the initial ejection operation is completed, in other words, before the start of the second flushing process, and the initial time TF8[m] indicated by the phase information NtF2[m] at the time when the second flushing process is completed. The discharge control unit 62 performs flushing operations FCr times as the third flushing process for the remaining discharge sections DR for which the difference |Tf0[m]-Tf8[m]| indicated by the difference information DF is greater than or equal to the predetermined value α, while not performing the third or subsequent flushing processes for the remaining discharge sections DR for which the difference |Tf0[m]-Tf8[m]| indicated by the difference information DF is less than the predetermined value α. Next, for the remaining discharge sections DR that have executed the third flushing process, the acquisition section 64 acquires the current phase information NtF[m] from the measurement circuit 9. Similarly, difference information DF[m] indicating the difference between the initial time TF indicated by the phase information NtF1[m] obtained before and after the nth flushing process and the initial time TF indicated by the phase information NtF2[m] is generated, and the n+1th flushing process is executed for the discharge section D[m] where the difference ΔTF indicated by the difference information DF[m] is greater than or equal to the predetermined value α, while the n+1th or subsequent flushing processes are not executed for the discharge section D[m] where the difference ΔTF indicated by the difference information DF[m] is less than the predetermined value α.

[0150] In this embodiment, during the ink discharge process, among the remaining ejection sections DR, for which the difference between the initial time TF0[m] indicated by the phase information NtF1[m] and the initial time TF8[m] indicated by the phase information NtF2[m] obtained before and after the second flushing process is less than a predetermined value α, the third or subsequent flushing process is not performed, but the present invention is not limited to this form. For example, in the ink discharging process, among the remaining discharge sections DR, the third or subsequent flushing process may be performed on the discharge sections D[m] for which the difference between the initial time TF0[m] indicated by the phase information NtF1[m] and the initial time TF8[m] indicated by the phase information NtF2[m] obtained before and after the second flushing process is less than a predetermined value α. Also, for example, in the ink discharging process, for the remaining discharge sections DR, the phase information NtF[m] may not be obtained before and after the second flushing process. That is, in the ink discharging process in this embodiment, the third or subsequent flushing process may be performed on the remaining discharge sections DR on the premise that all preparatory operations for the remaining discharge sections DR are completed. Even in this case, when "n≧3", for the remaining ejection sections DR, if the difference between the initial time TF indicated by the phase information NtF1[m] and the initial time TF indicated by the phase information NtF2[m] obtained before and after the nth flushing process is less than a predetermined value α, the flushing process from the n+1th onwards will not be performed for the ejection section D[m].

[0151] Figures 17 and 18 are flowcharts showing the operation of the control unit 6A. Steps S31 to S38 in the flowcharts shown in Figures 17 and 18 are the same as steps S11 to S18 in the flowchart shown in Figure 15, so their explanation will be omitted. Also, steps S43 to S46 in the flowcharts shown in Figures 17 and 18 are the same as steps S19 to S22 in the flowchart shown in Figure 15, so their explanation will be omitted.

[0152] In step S39, the control unit 6A executes a second flushing process corresponding to the final change point LM stored in the storage unit 5 for the remaining discharge sections DR. In step S40, the control unit 6A acquires, from the measurement circuit 9, the phase information NtF2[m] of the remaining discharge units DR[m]. In step S41, the control unit 6A generates difference information DF indicating the difference ΔTF between the initial time TF0[m] indicated by the phase information NtF1[m] acquired before the second flushing process and the initial time TF8[m] indicated by the phase information NtF2[m] acquired after the second flushing process for the remaining discharge sections DR[m]. Then, it is determined whether the difference ΔTF indicated by the difference information DF is less than a predetermined value α. For the remaining discharge sections DR[m] whose difference ΔTF is less than the predetermined value α, that is, the remaining discharge sections DR[m] whose result in step S41 is YES, the control unit 6A ends the series of processes. For the remaining discharge sections DR[m] whose difference ΔTF is equal to or greater than the predetermined value α, that is, the remaining discharge sections DR[m] whose result in step S41 is NO, in step S42, the control unit 6A rewrites the value of the phase information NtF1[m] to the current phase information NtF2[m], increases the value of the variable n from the current value by 1, and proceeds to step S43.

[0153] 3-3: Advantages of the Third Embodiment In the maintenance method according to this embodiment, the second amount is set to the largest accumulated amount among the accumulated amounts corresponding to the change points where the viscosity becomes maximum or minimum on the relationship line showing the relationship between the accumulated amount and the viscosity indicated by the relationship information.

[0154] Therefore, the maintenance method can simplify the preparation operations.

[0155] 4: Variation Each of the above embodiments may be modified in various ways. Specific modified aspects are exemplified below. The aspects exemplified below and the aspects shown in the above embodiment may be appropriately combined within a range that does not contradict each other. Note that, for elements in the modified examples exemplified below that have the same actions and functions as the embodiment, the reference numerals referenced in the above description are used and detailed descriptions of each are appropriately omitted.

[0156] 4-1: Variation 1 In the above embodiment, the acquisition unit 64 acquires the initial time TF as the phase information NtF from the measurement circuit 9. However, the acquisition unit 64 may acquire the period of the residual vibration signal NES[m] instead of the initial time TF as the phase information NtF.

[0157] 4-2: Variation 2 In the ink discharge process according to the second and third embodiments, after discharging the ink I in the flushing process for acquiring the relationship information, the sample discharger DS does not discharge the ink I when the flushing process is executed on the remaining dischargers Dr, but this is not limited to the above. For example, the control unit 6A may discharge the ink I from the sample discharger DS as well as the remaining dischargers D in the flushing process in which the discharge amount is determined based on the relationship information. In this case, the flushing process may also be repeated in the sample discharger DS until the difference information DF between the phase information NtF1 and the phase information NtF2 acquired before and after the flushing process becomes less than the predetermined value α.

[0158] 4-3: Variation 3 In the flushing process according to the above embodiment, the initial ejection operation is executed, but if the initial time TF can be accurately measured, the initial ejection operation may be omitted.

[0159] 4-4: Variation 4 In the flushing process according to the second embodiment, the ejection amounts of the remaining ejection sections DR for each flushing process are determined so that the flushing process ends at the timings corresponding to all the change points where the initial time TF becomes maximum and minimum on the relationship line L3, but this is not limited to the above. For example, the control section 6A may determine the ejection amounts for each flushing process so that the flushing process ends at the timings corresponding to one or more change points selected from the change points where the initial time TF becomes maximum and minimum on the relationship line L3.

[0160] 4-5: Variation 5 In the flushing process according to the third embodiment, the shot number FC=8FCq from the cumulative shot number ΣFC=FC0 corresponding to the measurement point P0 at the end of the initial discharge operation to the cumulative shot number ΣFC=FC8 corresponding to the final change point LM is determined as the shot number FCq in the second flushing process of the remaining discharge sections DR, but this is not limited to this. For example, the shot number FC=FC0+8FCq of the cumulative shot number ΣFC=FC8 corresponding to the final change point LM may be determined as the shot number FCq in the second flushing process of the remaining discharge sections DR. [Explanation of symbols]

[0161] 1, 1A, 1B: inkjet printer, 2: drive signal generating circuit, 4: maintenance unit, 5: memory unit, 6, 6A: control unit, 7: transport mechanism, 8: movement mechanism, 9: measurement circuit, 10: switching circuit, 11: connection state designation circuit, 14: liquid container, 20: detection circuit, 42: cap, 44: wiper, 61: drive control unit, 62: discharge control unit, 63: discharge amount determination unit, 64: acquisition unit, 65: generation unit, D: discharge unit, TF: initial time, ΔTF: difference, α: predetermined value, NtF: phase information, NtF1: first phase information, NtF2: second viscosity information

Claims

1. A maintenance method for a liquid ejection device having a plurality of ejection units that eject liquid, comprising the steps of: acquiring first viscosity information relating to a viscosity of the liquid filled in each of the plurality of ejection portions; Discharging a first amount of liquid from each of the plurality of discharge portions; acquiring second viscosity information relating to a viscosity of the liquid filled in each of the plurality of ejection portions; generating difference information indicating a difference between a viscosity indicated by the first viscosity information and a viscosity indicated by the second viscosity information in each of the plurality of ejection portions; from the ejection sections among the plurality of ejection sections for which the difference indicated by the difference information is equal to or greater than a predetermined value, the first amount of liquid is ejected again; The maintenance method includes not discharging liquid from any of the plurality of discharge units for which the difference indicated by the difference information is less than a predetermined value.

2. performing a preparation operation before discharging the first amount of liquid from each of the plurality of discharge portions; The preparatory operation includes: Select a sample discharge part from the plurality of discharge parts; by repeating the acquisition of viscosity information on the viscosity of the liquid filled in the sample discharging portion and the discharging of the liquid from the sample discharging portion a plurality of times, obtaining relationship information on the relationship between the cumulative amount of the liquid discharged from the sample discharging portion during the preparation operation and the viscosity; determining a second amount, which is an ejection amount of liquid to be ejected by the ejection unit in the preparation operation, based on the relationship information; discharging the second amount of liquid from the plurality of discharging units excluding the sample discharging unit; The maintenance method according to claim 1 .

3. before discharging the first amount of liquid from each of the plurality of discharge parts, discharging an amount of liquid smaller than the first amount from each of the plurality of discharge parts; The maintenance method according to claim 1 .

4. the second amount is a difference between the cumulative amount at each of a first change point and a second change point that are consecutive among change points at which the viscosity becomes maximum or minimum on a relation line that represents the relationship between the cumulative amount and the viscosity indicated by the relation information; The maintenance method according to claim 2.

5. the second amount is set based on the largest accumulated amount among accumulated amounts corresponding to a change point at which the viscosity becomes maximum or minimum on a relation line showing the relationship between the accumulated amount and the viscosity indicated by the relation information; The maintenance method according to claim 2.

6. In the preparation operation, when acquiring the related information, acquisition of viscosity information from the sample discharging portion and discharging of a third amount of liquid are repeatedly performed; the third amount being less than the first amount; The maintenance method according to claim 2.

7. When there is no change point at which the viscosity becomes a maximum or a minimum on the relationship line indicating the relationship between the cumulative amount and the viscosity, the second amount is set to the first amount. The maintenance method according to claim 2.

8. before the preparation operation, ejecting the liquid from each of the plurality of ejection parts in an amount smaller than the first amount; The maintenance method according to claim 2.

9. A plurality of ejection units that eject liquid; an acquisition unit that acquires viscosity information relating to a viscosity of the liquid filled in each of the plurality of ejection units; a discharge control unit that causes each of the plurality of discharge units to discharge liquid; a generation unit that generates difference information indicating a difference between a viscosity indicated by the first viscosity information and a viscosity indicated by the second viscosity information when the acquisition unit acquires first viscosity information regarding a viscosity of the liquid filled in each of the plurality of ejection units and the ejection control unit causes each of the plurality of ejection units to eject a first amount of liquid, and the acquisition unit acquires second viscosity information regarding the viscosity of the liquid filled in each of the plurality of ejection units; Equipped with The discharge control unit is from the ejection sections among the plurality of ejection sections for which the difference indicated by the difference information is equal to or greater than a predetermined value, the first amount of liquid is ejected again; The liquid ejection device does not eject liquid from any of the ejection sections for which the difference indicated by the difference information is less than a predetermined value.

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