Method for maintaining a head unit

Abstract

A maintenance method of a head unit that suppresses the scattering of liquid that has become an ink mist and has been ejected from a nozzle. The head unit includes a first nozzle row that includes one first nozzle, and a second nozzle row that includes one second nozzle. In the maintenance method, during a first period, liquid is discharged from the one first nozzle by supplying a first drive signal having a first waveform to one first drive element corresponding to the one first nozzle belonging to the first nozzle row, and liquid is discharged from the one second nozzle by supplying a second drive signal having a second waveform to one second drive element corresponding to the one second nozzle belonging to the second nozzle row. During a second period, liquid is discharged from the one first nozzle by supplying a third drive signal having a third waveform to the one first drive element, and liquid is discharged from the one second nozzle by supplying a fourth drive signal having a fourth waveform to the one second drive element.

Description

Technical Field

[0001] This invention relates to a method for maintaining a head unit. Background Technology

[0002] Liquid ejection devices such as inkjet printers use a drive signal to drive a piezoelectric element mounted on a head unit, causing it to displace and eject liquid, such as ink, from a pressure chamber on the head unit, through a nozzle to form an image on a recording paper or other medium. In such liquid ejection devices, for example, to suppress the degradation of image quality caused by thickening of the liquid in the pressure chamber, it is necessary to discharge the liquid from the nozzle. Therefore, for example, as described in Patent Document 1, techniques related to rinsing processes that discharge the liquid from the nozzle in the pressure chamber have been conventionally proposed.

[0003] However, in the existing technology, during the washing process, there is a situation where, because the maximum amount of liquid that can be ejected from each nozzle is ejected from all the nozzles set on the head unit, the liquid ejected from the nozzles becomes ink mist and scatters, resulting in a decrease in the image quality of the liquid ejection device and the occurrence of defects in the liquid ejection device.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2011-240564 Summary of the Invention

[0005] To address the above-mentioned issues, the maintenance method for a head unit according to the present invention is characterized in that the head unit comprises: a first nozzle array having a plurality of first nozzles arranged along a first axis and spraying liquid; a second nozzle array having a plurality of second nozzles arranged along a second axis parallel to the first axis and spraying liquid; a plurality of first pressure chambers corresponding to the plurality of first nozzles and filled with liquid; a plurality of second pressure chambers corresponding to the plurality of second nozzles and filled with liquid; a plurality of first drive elements corresponding to the plurality of first pressure chambers and causing pressure variations within the corresponding first pressure chambers; a plurality of second drive elements corresponding to the plurality of second pressure chambers and causing pressure variations within the corresponding second pressure chambers; and a supply unit supplying drive signals to the plurality of first drive elements and the plurality of second drive elements. In the maintenance method, during a first period, a first drive element with a first waveform is supplied with a first drive element. A driving signal is provided to discharge liquid from one of the plurality of first pressure chambers corresponding to the first driving element from one of the plurality of first nozzles corresponding to the first pressure chamber. A second driving signal with a second waveform different from the first waveform is supplied to one of the plurality of second driving elements, causing liquid from one of the plurality of second pressure chambers corresponding to the first driving element to be discharged from one of the plurality of second nozzles corresponding to the first pressure chamber. During a second period different from the first period, a third driving signal with a third waveform different from the first waveform is supplied to the first driving element, causing liquid from one of the first pressure chambers to be discharged from the first nozzle. Finally, a fourth driving signal with a fourth waveform different from both the second and third waveforms is supplied to the second driving element, causing liquid from one of the second pressure chambers to be discharged from the second nozzle. Attached Figure Description

[0006] Figure 1 This is a block diagram illustrating an example of the structure of an inkjet printer 1 according to an embodiment of the present invention.

[0007] Figure 2 A perspective view showing an example of the schematic internal structure of an inkjet printer 1.

[0008] Figure 3 A cross-sectional view used to illustrate an example of the structure of the ejector section D[m].

[0009] Figure 4A top view showing an example configuration of nozzle N in head unit 3.

[0010] Figure 5 A block diagram illustrating an example of the structure of head unit 3.

[0011] Figure 6 This is a timing diagram illustrating an example of the signals supplied to head unit 3.

[0012] Figure 7 An explanatory diagram illustrating an example of an independently specified signal Sd[m].

[0013] Figure 8 This is an explanatory diagram used to illustrate an example of the rinsing process involved in the implementation.

[0014] Figure 9 This is an explanatory diagram used to illustrate the rinsing process involved in Reference Example 1.

[0015] Figure 10 An explanatory diagram illustrating an example of flying droplets in the rinsing process described in Reference Example 1.

[0016] Figure 11 This is an explanatory diagram illustrating an example of a flying droplet in a rinsing process according to an embodiment.

[0017] Figure 12 This is an explanatory diagram used to illustrate the rinsing process involved in Reference Example 2.

[0018] Figure 13 This is an explanatory diagram used to illustrate the rinsing process involved in Modified Example 1.

[0019] Figure 14 This is an explanatory diagram used to illustrate the rinsing process involved in Reference Example 3.

[0020] Figure 15 This is an explanatory diagram used to illustrate the rinsing process involved in Modified Example 2.

[0021] Figure 16 An explanatory diagram illustrating an example of flying droplets in the rinsing process described in Reference Example 1.

[0022] Figure 17 An explanatory diagram illustrating an example of flying droplets in the rinsing process involved in Modified Example 2.

[0023] Figure 18 This is an explanatory diagram used to illustrate the rinsing process involved in Modified Example 3.

[0024] Figure 19 An explanatory diagram is provided to illustrate an example of the independently specified signal Sd[m] involved in Variation Example 4. Detailed Implementation

[0025] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. However, the dimensions and scales of the various parts in the drawings differ appropriately from the actual situation. Furthermore, since the embodiments described below are preferred examples of the present invention, various technically preferred limitations have been added, but unless otherwise stated in the following description, the scope of the present invention is not limited to these embodiments.

[0026] A. Implementation Method

[0027] In this embodiment, an inkjet printer that ejects ink to form an image on recording paper PP is used as an example to describe the liquid ejection device. Furthermore, in this embodiment, ink is an example of "liquid," and recording paper PP is an example of "medium."

[0028] 1. Overview of Inkjet Printers

[0029] like Figure 1 As illustrated, in inkjet printer 1, printing data Img representing the image to be formed by inkjet printer 1 is supplied from a host computer such as a personal computer. Inkjet printer 1 performs printing processing to form the image shown in printing data Img on recording paper PP.

[0030] The inkjet printer 1 includes: a control unit 2 that controls various parts of the inkjet printer 1; a head unit 3 that has an ink ejection section D; a drive signal generation unit 4 that generates a drive signal Com for driving the ejection section D; a transport unit 7 that changes the relative position of the recording paper PP with respect to the head unit 3; and a maintenance unit 8 that performs maintenance procedures described later.

[0031] Furthermore, in this embodiment, the inkjet printer 1 includes one or more head units 3 and one or more drive signal generation units 4 corresponding one-to-one with the one or more head units 3. Specifically, in this embodiment, the inkjet printer 1 includes four head units 3 and four drive signal generation units 4 corresponding one-to-one with the four head units 3. However, for ease of explanation in the following text, as... Figure 1 As illustrated, the explanation will focus on one of the four head units 3 and one of the four drive signal generation units 4, which is provided in correspondence with one of the head units 3.

[0032] The control unit 2 is configured to include one or more CPUs. However, the control unit 2 may replace the CPU or incorporate a programmable logic device such as an FPGA on top of the CPU. Here, CPU stands for Central Processing Unit, and FPGA stands for Field-Programmable Gate Array. Furthermore, the control unit 2 is configured to include one or both of the following: volatile memory such as RAM (Random Access Memory), non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable Read-Only Memory).

[0033] Although the details will be described later, the control unit 2 generates signals such as the printing signal SI and the waveform specification signal dCom to control the operation of various parts of the inkjet printer 1.

[0034] Here, the waveform specification signal dCom refers to a signal that specifies the waveform of the drive signal Com. Furthermore, the drive signal Com refers to an analog signal used to drive the ejector section D. In this embodiment, the drive signal Com includes drive signal Com-A and drive signal Com-B. The drive signal generation unit 4 includes a DA conversion circuit and generates a drive signal Com having the waveform specified by the waveform specification signal dCom. Furthermore, the printing signal SI refers to a signal that specifies the type of operation of the ejector section D. Specifically, the printing signal SI is a signal that specifies the type of operation of the ejector section D by specifying whether to supply the drive signal Com to the ejector section D.

[0035] like Figure 1 As illustrated, the head unit 3 includes a supply circuit 31 and a recording head 32.

[0036] The recording head 32 has 2M ejector sections D. Here, the value M is a natural number satisfying "M≥1". Furthermore, in the following text, the m-th ejector section D among the 2M ejector sections D provided on the recording head 32 is referred to as ejector section D[m]. Here, the variable m is a natural number satisfying "1≤m≤2M". Additionally, in the following text, when structural elements or signals of the inkjet printer 1 correspond to ejector sections D[m] among the 2M ejector sections D, the suffix [m] is sometimes added to the symbols used to represent those structural elements or signals.

[0037] The supply circuit 31 switches whether to supply the drive signal Com to the ejector section D[m] based on the printing signal SI. In addition, in the following text, the drive signal Com supplied to the ejector section D[m] is referred to as the supply drive signal Vin[m].

[0038] As described above, in this embodiment, the inkjet printer 1 performs printing processing. During printing processing, the control unit 2 generates signals such as a printing signal SI to control the head unit 3, a waveform specification signal dCom to control the drive signal generation unit 4, and a transport unit 7 based on the printing data Img. Thus, the control unit 2 controls the transport unit 7 in a manner that changes the relative position of the recording paper PP with respect to the head unit 3 during printing processing, and adjusts the presence or absence of ink ejection from the ejection section D[m], the amount of ink ejected, and the ink ejection timing, thereby controlling each part of the inkjet printer 1 to form an image corresponding to the printing data Img on the recording paper PP.

[0039] As described above, in this embodiment, the inkjet printer 1 performs maintenance processing on the ejector section D. Here, in this embodiment, the maintenance processing includes a rinsing process to discharge ink from the ejector section D, a wiping process to wipe away foreign matter such as ink adhering to the nozzle N of the ejector section D using a wiping device, and a suction process to draw ink in and out of the ejector section D using a pump or the like. The maintenance unit 8 includes: an ink discharge receiving section 80 for receiving the discharged ink when it is discharged from the ejector section D; a wiping device for wiping away foreign matter such as ink adhering to the nozzle N of the ejector section D; and a pump for suctioning ink, air bubbles, etc., from the ejector section D. The wiping device and the pump are not shown in the figures.

[0040] When performing the rinsing process, the control unit 2 generates signals such as the printing signal SI to control the head unit 3 and signals such as the waveform specification signal dCom to control the drive signal generation unit 4. Furthermore, when the inkjet printer 1 performs the rinsing process, the printing signal SI specifies the operation of the 2M ejector sections D mounted on the head unit 3, causing the 2M ejector sections D to operate in a predetermined manner.

[0041] Furthermore, during the rinsing process, the control unit 2 generates a signal to control the transport unit 7 so as to move the head unit 3 to a position opposite to the ink discharge receiving section 80. Thus, during the rinsing process, the control unit 2 controls each part of the inkjet printer 1 to discharge ink from the ejection section D provided on the head unit 3 to the ink discharge receiving section 80.

[0042] like Figure 2 As illustrated, in this embodiment, the inkjet printer 1 is a serial printer. Specifically, when performing printing, the inkjet printer 1 conveys the recording paper PP in the sub-scanning direction while reciprocating the head unit 3 in the main scanning direction that intersects the sub-scanning direction, and ejects ink from the ejection section D[m], thereby forming dots Dt on the recording paper PP corresponding to the printing data Img.

[0043] In the following text, the +X direction and its opposite -X direction are collectively referred to as the "X-axis direction," the +Y direction intersecting the X-axis direction and its opposite -Y direction are collectively referred to as the "Y-axis direction," and the +Z direction intersecting both the X-axis and Y-axis directions and its opposite -Z direction are collectively referred to as the "Z-axis direction." Furthermore, in this embodiment, as... Figure 2 As illustrated, the +X direction, which runs from the -X side (upstream) towards the +X side (downstream), is designated as the sub-scanning direction, and the +Y and -Y directions are designated as the main scanning directions. Furthermore, in this embodiment, as... Figure 2 As illustrated, the +Z direction is set as the ejection direction of ink from the ejector section D[m].

[0044] like Figure 2 As illustrated, the inkjet printer 1 according to this embodiment includes a frame 100 and a carriage 110, which is capable of reciprocating within the frame 100 in the Y-axis direction and carries four head units 3.

[0045] In this embodiment, such as Figure 2 As illustrated, the carriage 110 houses four ink cartridges 120, each corresponding to one of the four ink colors: cyan, magenta, yellow, and black. Furthermore, in this embodiment, as described above, the inkjet printer 1 includes four head units 3, each corresponding to one of the four ink cartridges 120. Thus, each ejector section D[m] can be internally filled with ink supplied from the corresponding ink cartridge 120 and ejected from the nozzle N. Alternatively, the ink cartridges 120 can also be disposed outside the carriage 110.

[0046] Furthermore, as described above, the inkjet printer 1 according to this embodiment includes a transport unit 7. For example... Figure 2 As illustrated, the transport unit 7 includes a carriage transport mechanism 71 for reciprocating the carriage 110 in the Y-axis direction, a carriage guide shaft 76 for supporting the carriage 110 in a reciprocating manner in the Y-axis direction, a media transport mechanism 73 for transporting the recording paper PP, and an impression plate 75 disposed on the +Z side of the carriage 110.

[0047] like Figure 3 As illustrated, the ejection section D[m] includes a piezoelectric element PZ[m], a chamber CV filled with ink, a nozzle N communicating with the chamber CV, and a vibrating plate 321. In the ejection section D[m], the piezoelectric element PZ[m] is driven by a drive signal Vin[m], thereby ejecting the ink in the chamber CV from the nozzle N. The chamber CV is a space divided by a chamber plate 324, a nozzle plate 323 on which the nozzle N is formed, and a vibrating plate 321. The chamber CV is connected to a reservoir 325 via an ink supply port 326. The reservoir 325 is connected to an ink cartridge 120 corresponding to the ejection section D[m] via an ink inlet 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric element Zm[m] disposed between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is electrically connected to the power supply line Ld, which is set to potential VBS. Furthermore, when a drive signal Vin[m] is supplied to the upper electrode Zu[m] and a voltage is applied between the upper electrode Zu[m] and the lower electrode Zd[m], the piezoelectric element PZ[m] is displaced in the +Z or -Z direction accordingly, resulting in the piezoelectric element PZ[m] vibrating. The lower electrode Zd[m] is attached to the vibrating plate 321. Therefore, when the piezoelectric element PZ[m] is driven and vibrates by the supplied drive signal Vin[m], the vibrating plate 321 also vibrates. Moreover, the vibration of the vibrating plate 321 causes changes in the volume of the chamber CV and the pressure within the chamber CV, thereby causing the ink filled within the chamber CV to be ejected from the nozzle N.

[0048] Figure 4 This is an explanatory diagram illustrating an example of the configuration of four head units 3 mounted on the carriage 110 and a total of 8M nozzles N set on the four head units 3, when viewed from above in the +Z direction of the inkjet printer 1.

[0049] like Figure 4 As illustrated, each head unit 3 mounted on the carriage 110 is provided with two nozzle rows NL. Here, a nozzle row NL refers to a plurality of nozzles N arranged in a row-like manner in a predetermined direction. In this embodiment, each nozzle row NL is composed of M nozzles N arranged in a manner extending in the X-axis direction.

[0050] Furthermore, in the following text, one of the two nozzle rows NL provided on the head unit 3 will be referred to as nozzle row NL-1, and the other nozzle row NL will be referred to as nozzle row NL-2. More specifically, in this embodiment, nozzle row NL-1 consists of M nozzles N arranged along axis AX-1 parallel to the X-axis direction, and nozzle row NL-2 consists of M nozzles N arranged along axis AX-2 parallel to the X-axis direction and located in the +Y direction of axis AX-1. That is, in this embodiment, the head unit 3 has a total of 2M nozzles N, including M nozzles N belonging to nozzle row NL-1 and M nozzles N belonging to nozzle row NL-2. In addition, nozzle row NL-1 is an example of a "first nozzle row", nozzle row NL-2 is an example of a "second nozzle row", axis AX-1 is an example of a "first axis", and axis AX-2 is an example of a "second axis".

[0051] Furthermore, in the following text, the nozzle N belonging to nozzle column NL-1 out of the 2M nozzles N set on the head unit 3 is referred to as nozzle N-1, and the nozzle N belonging to nozzle column NL-2 is referred to as nozzle N-2. Additionally, in the following text, the m1-th nozzle N-1 among the M nozzles N-1 belonging to nozzle column NL-1 is referred to as nozzle N-1[m1], and the m2-th nozzle N-2 among the M nozzles N-2 belonging to nozzle column NL-2 is referred to as nozzle N-2[m2]. Here, the variable m1 is a natural number satisfying "1 ≤ m1 ≤ M", and the variable m2 is a natural number satisfying "1 ≤ m2 ≤ M". Furthermore, nozzle N-1 is an example of a "first nozzle", and nozzle N-2 is an example of a "second nozzle".

[0052] Furthermore, in the following text, the ejector D that includes nozzle N-1 belonging to nozzle row NL-1 among the 2M ejector sections D provided on the head unit 3 is referred to as ejector section D-1, and the ejector D that includes nozzle N-2 belonging to nozzle row NL-2 is referred to as ejector section D-2. That is, the 2M ejector sections D[1] to D[2M] provided on the head unit 3 include M ejector sections D-1[1] to D-1[M] corresponding to nozzle row NL-1, and M ejector sections D-2[1] to D-2[M] corresponding to nozzle row NL-2. Furthermore, in the following text, the ejector section D-1 that includes nozzle N-1[m1] is referred to as ejector section D-1[m1], and the ejector section D-2 that includes nozzle N-2[m2] is referred to as ejector section D-2[m2].

[0053] Furthermore, in the following text, the piezoelectric element PZ provided on the ejection section D-1 [m1] is referred to as piezoelectric element PZ-1 [m1], and the piezoelectric element PZ provided on the ejection section D-2 [m2] is referred to as piezoelectric element PZ-2 [m2]. Furthermore, in the following text, the supply drive signal Vin supplied to the ejection section D-1 [m1] is referred to as supply drive signal Vin-1 [m1], and the supply drive signal Vin supplied to the ejection section D-2 [m2] is referred to as supply drive signal Vin-2 [m2]. Furthermore, in the following text, the chamber CV provided on the ejection section D-1 [m1] is referred to as chamber CV-1 [m1], and the chamber CV provided on the ejection section D-2 [m2] is referred to as chamber CV-2 [m2].

[0054] Additionally, piezoelectric element PZ-1 is an example of a "first driving element", and piezoelectric element PZ-2 is an example of a "second driving element". Furthermore, chamber CV-1 is an example of a "first pressure chamber", and chamber CV-2 is an example of a "second pressure chamber".

[0055] 2. Overview of the Head Unit

[0056] like Figure 5 As illustrated, the head unit 3 includes a supply circuit 31 and a recording head 32. Furthermore, the head unit 3 includes a wiring La for supplying a drive signal Com-A from the drive signal generation unit 4, and a wiring Lb for supplying a drive signal Com-B from the drive signal generation unit 4.

[0057] like Figure 5 As illustrated, the supply circuit 31 includes 2M switches Wa[1] to Wa[2M] corresponding one-to-one with 2M ejector sections D[1] to D[2M], 2M switches Wb[1] to Wb[2M] corresponding one-to-one with 2M ejector sections D[1] to D[2M], and a connection state designation circuit 310 for designating the connection state of each switch. Furthermore, the supply circuit 31 is an example of a "supply section".

[0058] The connection state specifying circuit 310 generates a connection state specifying signal Qa[m] for specifying the on or off state of switch Wa[m] and a connection state specifying signal Qb[m] for specifying the on or off state of switch Wb[m] based on at least a portion of the printed signal SI, latch signal LAT and conversion signal CH supplied from control unit 2.

[0059] The switch Wa[m] switches between on and off states between the wiring La and the upper electrode Zu[m] of the piezoelectric element PZ[m] disposed on the ejector section D[m], based on the connection state specification signal Qa[m]. In this embodiment, the switch Wa[m] is on when the connection state specification signal Qa[m] is high and off when it is low. When the switch Wa[m] is on, the drive signal Com-A supplied to the wiring La is supplied to the upper electrode Zu[m] of the ejector section D[m] as the supply drive signal Vin[m].

[0060] The switch Wb[m] switches between on and off states between the wiring Lb and the upper electrode Zu[m] of the piezoelectric element PZ[m] disposed on the ejector section D[m], based on the connection state specification signal Qb[m]. In this embodiment, the switch Wb[m] is on when the connection state specification signal Qb[m] is high and off when it is low. When the switch Wb[m] is on, the drive signal Com-B supplied to the wiring Lb is supplied to the upper electrode Zu[m] of the ejector section D[m] as the supply drive signal Vin[m].

[0061] In this embodiment, when the inkjet printer 1 performs printing or washing processes, one or more unit periods TP are set as the operating period of the inkjet printer 1. Within each unit period TP, the inkjet printer 1 according to this embodiment can drive each ejection section D[m] to perform printing or washing processes. Furthermore, in the following text, the unit period TP for performing printing processes will be referred to as the printing unit period TPP, and the unit period TP for performing washing processes will be referred to as the washing unit period TPF.

[0062] Figure 6 This is a timing diagram showing the various signals, such as the drive signal Com, supplied to head unit 3 within a unit period TP.

[0063] like Figure 6 As illustrated, control unit 2 outputs a latched signal LAT with a pulse PLL. Thus, control unit 2 defines the unit period TP as the period from the rising edge of the pulse PLL to the rising edge of the next pulse PLL.

[0064] Furthermore, the control unit 2 outputs a conversion signal CH with pulse PLC1 and pulse PLC2 within a unit period TP. Moreover, the control unit 2 divides the unit period TP into a control period TQ1 from the rising edge of pulse PLL to the rising edge of pulse PLC1, a control period TQ2 from the rising edge of pulse PLC1 to the rising edge of pulse PLC2, and a control period TQ3 from the rising edge of pulse PLC2 to the rising edge of pulse PLL.

[0065] The printing signal SI involved in this embodiment includes 2M independently specified signals Sd[1] to Sd[2M], each corresponding to one of the 2M ejector sections D[1] to D[2M]. When the inkjet printer 1 performs printing or washing processes, the independently specified signal Sd[m] specifies the driving method of the ejector section D[m] within each unit period TP.

[0066] like Figure 6 As illustrated, before each unit period TP, the control unit 2 synchronizes the printed signal SI, which includes 2M independent designation signals Sd[1] to Sd[2M], with the clock signal CL and supplies it to the connection state designation circuit 310. Moreover, the connection state designation circuit 310 generates connection state designation signal Qa[m] and connection state designation signal Qb[m] based on the independent designation signals Sd[m] during the unit period TP.

[0067] Furthermore, in this embodiment, within a printing unit period TPP, which serves as the unit period TP for performing the printing process, the ejector section D[m] can form any point Dt among those consisting of a large dot composed of ink amount ξ1, a medium dot composed of ink amount ξ2 which is less than ink amount ξ1, and a small dot composed of ink amount ξ3 which is less than ink amount ξ2. Additionally, in the following text, when the unit period TP is the printing unit period TPP, the ejector section D is sometimes referred to as the printing ejector section DP.

[0068] Furthermore, in this embodiment, within the rinsing unit period TPF, which is the unit period TP for performing the rinsing process, the ejector section D[m] can perform a large-volume ink discharge of ink amount ξ4 and a small-volume ink discharge of ink amount ξ5, which is less than the ink amount ξ4. Additionally, in the following text, when the unit period TP is the rinsing unit period TPF, the ejector section D is sometimes referred to as the rinsing target ejector section DF.

[0069] like Figure 7As illustrated, in this embodiment, during the printing unit period TPP, which is the unit period TP for performing the printing process, the independently designated signal Sd[m] can take any one of the following four values: "1" for designating the ejector D[m] as a large dot forming ejector DP-1, "2" for designating the ejector D[m] as a medium dot forming ejector DP-2, "3" for designating the ejector D[m] as a small dot forming ejector DP-3, and "4" for designating the ejector D[m] as a non-dot forming ejector DP-N.

[0070] like Figure 7 As illustrated, in this embodiment, during the rinsing unit period TPF, which is the unit period TP for performing the rinsing process, the independently designated signal Sd[m] can take any one of the following three values: value "5" for designating the ejector D[m] as the large ink ejector DF-1, value "6" for designating the ejector D[m] as the small ink ejector DF-2, and value "7" for designating the ejector D[m] as the discharge restriction ejector DF-N.

[0071] like Figure 6 As illustrated, in this embodiment, the drive signal Com-A has waveform PA1 set during control period TQ1, waveform PA2 set during control period TQ2, and waveform PA3 set during control period TQ3.

[0072] Here, waveform PA1 is a waveform that travels from reference potential V0 through a potential VLA1 that is lower than reference potential V0 and a potential VHA1 that is higher than reference potential V0, and then returns to reference potential V0. Waveform PA1 is defined such that when a supply drive signal Vin[m] with waveform PA1 is supplied to the ejection section D[m], ink equivalent to ink amount φ1 is ejected from the ejection section D[m].

[0073] Furthermore, waveform PA2 is a waveform that travels from reference potential V0 through a potential VLA2 (lower than reference potential V0) and a potential VHA2 (higher than reference potential V0) and returns to reference potential V0. Waveform PA2 is defined such that when a supply drive signal Vin[m] having waveform PA2 is supplied to the ejection section D[m], ink equivalent to ink amount φ2 is ejected from the ejection section D[m].

[0074] Furthermore, waveform PA3 is a waveform that travels from reference potential V0 through a potential VLA3 that is lower than reference potential V0 and a potential VHA3 that is higher than reference potential V0, and then returns to reference potential V0. Waveform PA3 is defined such that when a supply drive signal Vin[m] having waveform PA3 is supplied to the ejection section D[m], ink equivalent to ink amount φ3 is ejected from the ejection section D[m].

[0075] In addition, in the following text, waveforms PA1, PA2, and PA3 will be collectively referred to as waveform PAA.

[0076] In this embodiment, as an example, when the potential of the supply drive signal Vin[m] supplied to the ejection section D[m] is high, the volume of the chamber CV of the ejection section D[m] will be smaller compared to the case of a low potential. Therefore, when the ejection section D[m] is driven by the supply drive signal Vin[m] having a waveform PA1, etc., the ink in the ejection section D[m] is ejected from the nozzle N by the change in the potential of the supply drive signal Vin[m] from a low potential to a high potential.

[0077] Furthermore, in this embodiment, waveforms PA1, PA2, and PA3 have approximately the same shape. That is, in this embodiment, ink amounts φ1, φ2, and φ3 are approximately the same. Hereinafter, ink amounts φ1, φ2, and φ3 will be collectively referred to as ink amount φL.

[0078] Here, "substantially the same" is defined to include not only cases where they are completely identical, but also cases where errors can be considered the same. For example, cases where they are identical in design but different due to manufacturing errors, and cases where they are identical in specifications but different due to errors caused by interference, etc. In this specification, "substantially the same" is simply referred to as "the same". That is, in this specification, "the same" refers to a concept that includes "substantially the same".

[0079] like Figure 6 As illustrated, in this embodiment, the drive signal Com-B has waveform PB1 set during control period TQ1, waveform PB2 set during control period TQ2, and waveform PB3 set during control period TQ3.

[0080] The waveform PB1 is a waveform that travels from the reference potential V0 through a potential VLB1 (lower than the reference potential V0 and higher than the potential VLA1) and a potential VHB1 (higher than the reference potential V0 and lower than the potential VHA1), and returns to the reference potential V0. The waveform PB1 is defined such that when a supply drive signal Vin[m] with waveform PB1 is supplied to the ejection section D[m], ink equivalent to the ink amount φ4 is ejected from the ejection section D[m]. Furthermore, in this embodiment, the ink amount φ4 is less than the ink amount φ1.

[0081] Furthermore, waveform PB2 is a waveform that travels from reference potential V0 through potential VLB2 (which is lower than reference potential V0 and higher than potential VLA2) and potential VHB2 (which is higher than reference potential V0 and lower than potential VHA2), and returns to reference potential V0. Waveform PB2 is defined such that when a supply drive signal Vin[m] with waveform PB2 is supplied to the ejection section D[m], ink equivalent to ink amount φ5 is ejected from the ejection section D[m]. In this embodiment, ink amount φ5 is less than ink amount φ2.

[0082] Furthermore, waveform PB3 is a waveform that travels from reference potential V0 through potential VLB3 (which is lower than reference potential V0 and higher than potential VLA3) and potential VHB3 (which is higher than reference potential V0 and lower than potential VHA3) and returns to reference potential V0. Waveform PB3 is defined such that when a supply drive signal Vin[m] with waveform PB3 is supplied to the ejection section D[m], no ink is ejected from the ejection section D[m].

[0083] Furthermore, in the following text, waveforms PB1 and PB2 will be collectively referred to as waveform PBB. Additionally, in this embodiment, waveforms PB1 and PB2 have approximately the same shape.

[0084] In addition, in this embodiment, ink quantity ξ1 is equivalent to the total amount of ink quantity φ1, ink quantity φ2 and ink quantity φ3, ink quantity ξ2 is equivalent to the total amount of ink quantity φ1 and ink quantity φ2, ink quantity ξ3 is equivalent to the total amount of ink quantity φ4 and ink quantity φ5, ink quantity ξ4 is equivalent to the total amount of ink quantity φ1, ink quantity φ2 and ink quantity φ3, and ink quantity ξ5 is the same as ink quantity φ2.

[0085] like Figure 7As illustrated, when the independent specified signal Sd[m] is represented by the value "1", the connection state specifying circuit 310 sets the connection state specifying signal Qa[m] to a high level during control periods TQ1, TQ2, and TQ3. In this case, the switch Wa[m] is turned on throughout the printing unit period TPP, and the ejector D[m] is driven by the supply drive signal Vin[m] having waveforms PA1, PA2, and PA3, thereby ejecting ink equivalent to the ink volume ξ1 of the large dot.

[0086] Furthermore, when the independently specified signal Sd[m] is represented by the value "2", the connection state specifying circuit 310 sets the connection state specifying signal Qa[m] to a high level during control periods TQ1 and TQ2. In this case, the switch Wa[m] is turned on during control periods TQ1 and TQ2. Therefore, the ejector D[m] is driven by the supply drive signal Vin[m] with waveforms PA1 and PA2 during the printing unit TPP, thereby ejecting ink equivalent to the ink amount ξ2 at the midpoint.

[0087] Furthermore, when the independently specified signal Sd[m] is represented by the value "3", the connection state specifying circuit 310 sets the connection state specifying signal Qb[m] to a high level during control periods TQ1 and TQ2. In this case, the switch Wb[m] is turned on during control periods TQ1 and TQ2. Therefore, the ejector D[m] is driven by the supply drive signal Vin[m] with waveforms PB1 and PB2 during the printing unit TPP, thereby ejecting ink equivalent to the ink amount ξ3 of the small dot.

[0088] Furthermore, when the independently specified signal Sd[m] is represented by the value "4", the connection state specifying circuit 310 sets the connection state specifying signal Qb[m] to a high level during the control period TQ3. In this case, the switch Wb[m] is turned on during the control period TQ3. Therefore, although the ejector section D[m] is driven by the supply drive signal Vin[m] with waveform PB3 during the printing unit TPP, no ink is ejected.

[0089] Furthermore, when the independently specified signal Sd[m] is represented by the value "5", the connection state specifying circuit 310 sets the connection state specifying signal Qa[m] to a high level during control periods TQ1, TQ2, and TQ3. In this case, the switch Wa[m] is turned on throughout the TPF during the rinsing unit period. Therefore, the ejector D[m] is driven by the supply drive signal Vin[m] having waveforms PA1, PA2, and PA3 during the TPF during the rinsing unit period, thereby ejecting ink equivalent to the amount of ink ξ4 discharged in large quantities.

[0090] Furthermore, when the independently specified signal Sd[m] is represented as the value "6", the connection state specifying circuit 310 sets the connection state specifying signal Qa[m] to a high level during the control period TQ2. In this case, the switch Wa[m] is turned on during the control period TQ2. Therefore, the ejector D[m] is driven by the supply drive signal Vin[m] with waveform PA2 during the rinsing unit TPF, thereby ejecting ink equivalent to the amount of ink ξ5 discharged in a small amount of ink.

[0091] Furthermore, when the independent specified signal Sd[m] is represented as the value "7", the connection state specified circuit 310 sets the connection state specified signal Qb[m] to a high level during the control period TQ3. Therefore, although the ejector section D[m] is driven by the supply drive signal Vin[m] with waveform PB3 during the rinsing unit TPF, it does not eject ink.

[0092] Furthermore, in the following text, during the TPF (Transmission Period for a Washing Unit), the waveform of the supply drive signal Vin[m] supplied to the ejection section D[m] designated as the bulk ink ejection section DF-1 is referred to as the bulk ink discharge waveform PF1, the waveform of the supply drive signal Vin[m] supplied to the ejection section D[m] designated as the small ink ejection section DF-2 is referred to as the small ink discharge waveform PF2, and the waveform of the supply drive signal Vin[m] supplied to the ejection section D[m] designated as the discharge restriction ejection section DF-N is referred to as the ink discharge restriction waveform PFN. That is, in this embodiment, the bulk ink discharge waveform PF1 is a waveform composed of waveforms PA1, PA2, and PA3, the small ink discharge waveform PF2 is waveform PA2, and the ink discharge restriction waveform PFN is waveform PB3.

[0093] 3. Rinsing treatment

[0094] exist Figure 8In the example shown, the case where each nozzle row NL provided on the head unit 3 is composed of six ejection sections D with “M=6” is illustrated. Nozzle row NL-1 has nozzles N-1[1] to N-1[6] corresponding to ejection sections D-1[1] to D-1[6], and nozzle row NL-2 has nozzles N-2[1] to N-2[6] corresponding to ejection sections D-2[1] to D-2[6].

[0095] In addition, Figure 8 In the example shown, the rinsing process is performed in six consecutive unit periods TP, namely unit periods TP(1) to TP(6).

[0096] like Figure 8 As illustrated, in each of the unit periods TP(1) to TP(3) of the unit period TP(1) to TP(6) during the execution of the rinsing process, the control unit 2 supplies the head unit 3 with a printing signal SI that designates each of the ejector parts D-1[1] to D-1[6] corresponding to the nozzle line NL-1 as a large ink ejector part DF-1 and each of the ejector parts D-2[1] to D-2[6] corresponding to the nozzle line NL-2 as a small ink ejector part DF-2. In addition, in each of the unit periods TP(4) to TP(6), the control unit 2 supplies the head unit 3 with a printing signal SI that designates each of the ejector parts D-1[1] to D-1[6] corresponding to the nozzle line NL-1 as a small ink ejector part DF-2 and each of the ejector parts D-2[1] to D-2[6] corresponding to the nozzle line NL-2 as a large ink ejector part DF-1.

[0097] That is, in this embodiment, during each of the unit periods TP(1) to TP(3), the control unit 2 supplies a supply drive signal Vin-1[1] with a large amount of ink discharge waveform PF1 to the ejector section D-1[1], thereby causing the ejector section D-1[1] to operate as a large amount of ink ejector section DF-1, and causing the ink in the chamber CV-1[1] to be discharged from the nozzle N-1[1] belonging to the nozzle row NL-1. In addition, during each of the unit periods TP(1) to TP(3), the control unit 2 supplies a supply drive signal Vin-2[1] with a small amount of ink discharge waveform PF2 to the ejector section D-2[1], thereby causing the ejector section D-2[1] to operate as a small amount of ink ejector section DF-2, and causing the ink in the chamber CV-2[1] to be discharged from the nozzle N-2[1] belonging to the nozzle row NL-2.

[0098] Furthermore, during each of the unit periods TP(4) to TP(6), the control unit 2 supplies a supply drive signal Vin-1[1] with a small amount of ink discharge waveform PF2 to the ejector section D-1[1], thereby causing the ejector section D-1[1] to operate as a small amount of ink ejector section DF-2, and causing the ink in the chamber CV-1[1] to be discharged from the nozzle N-1[1] belonging to the nozzle row NL-1. Furthermore, during each of the unit periods TP(4) to TP(6), the control unit 2 supplies a supply drive signal Vin-2[1] with a large amount of ink ejector section DF-1 to the ejector section D-2[1], thereby causing the ejector section D-2[1] to operate as a large amount of ink ejector section DF-1, and causing the ink in the chamber CV-2[1] to be discharged from the nozzle N-2[1] belonging to the nozzle row NL-2.

[0099] In addition, in this embodiment, each of the unit periods TP(1) to TP(3) is an example of a "first period", each of the unit periods TP(4) to TP(6) is an example of a "second period", piezoelectric element PZ-1[1] is an example of a "first driving element", piezoelectric element PZ-2[1] is an example of a "second driving element", and the supply driving signal Vin-1[1] supplied in each of the unit periods TP(1) to TP(3) is an example of a "first driving signal". The supply drive signal Vin-2[1] supplied in each of them is an example of a "second drive signal", the supply drive signal Vin-1[1] supplied in the unit period TP(4) to TP(6) is an example of a "third drive signal", the supply drive signal Vin-2[1] supplied in the unit period TP(4) to TP(6) is an example of a "fourth drive signal", the large ink discharge waveform PF1 is an example of a "first waveform" and a "fourth waveform", and the small ink discharge waveform PF2 is an example of a "second waveform" and a "third waveform".

[0100] Figure 9 In each of the unit periods TP(1) to TP(6) of the illustrated Reference Example 1, the control unit 2 supplies the head unit 3 with a printing signal SI that designates each of the ejector sections D-1[1] to D-1[6] corresponding to the nozzle line NL-1 and each of the ejector sections D-2[1] to D-2[6] corresponding to the nozzle line NL-2 as the mass ink ejector section DF-1.

[0101] Figure 10This indicates the situation where, during the rinsing process described in Reference Example 1, droplets ejected from nozzles N-1[m0] and N-2[m0] mounted on head unit 3 fly as points. Here, the variable m0 is a natural number satisfying "1 ≤ m0 ≤ M". Figure 10 In the diagram, nozzle N-2[m0] is located in the +Y direction of nozzle N-1[m0], and nozzle N-2[m0] is adjacent to nozzle N-1[m0] in the Y-axis direction.

[0102] In the rinsing process described in Reference Example 1, the ejector section D-1 [m0] is driven by a supply drive signal Vin-1 [m0] having three waveforms PAA, thereby operating as a large ink ejector section DF-1, and continuously ejecting three points Dt from the nozzle N-1 [m0] provided on the ejector section D-1 [m0] within each unit period TP. Furthermore, in the rinsing process described in Reference Example 1, the ejector section D-2 [m0] is driven by a supply drive signal Vin-2 [m0] having three waveforms PAA, thereby operating as a large ink ejector section DF-1, and continuously ejecting three points Dt from the nozzle N-2 [m0] provided on the ejector section D-2 [m0] within each unit period TP. Therefore, in the rinsing process described in Reference Example 1, the density of the flying point Dt is higher than that of the space between the head unit 3 and the recording paper PP. As a result of the airflow flowing along the flying point Dt, the air pressure in the space between the nozzles N-1 [m0] and N-2 [m0] becomes lower than that in other spaces around the head unit 3.

[0103] In the following text, the space between nozzles N-1 [m0] and N-2 [m0] will be referred to as the inter-nozzle decompression space SP. When ejection sections D-1 [m0] and D-2 [m0] operate as mass ink ejection sections DF-1, the density of the flying point Dt is relatively high relative to the space between the head unit 3 and the recording paper PP, and an airflow towards the recording paper PP is generated around the flight path of point Dt ejected from nozzle N. Due to this airflow towards the recording paper PP, the air pressure in the inter-nozzle decompression space SP becomes lower than that in other spaces around the head unit 3, thus generating a stronger airflow towards the inter-nozzle decompression space SP from the recording paper PP side. In the following text, the airflow towards the recording paper PP and then towards the inter-nozzle decompression space SP generated by the ejection of point Dt from the aforementioned nozzle N will be referred to as the self-flowing flow JF-A.

[0104] As dot Dt is ejected from nozzle N, the liquid from nozzle N towards the recording paper PP is elongated and protrudes. This protrusion then tears off, and the torn portion, while in flight, forms a spherical dot Dt due to surface tension. In the formation of such dot Dt, relatively large main droplets and relatively small satellite droplets and fine ink mist are generated. Because the smaller satellite droplets and ink mist have less energy generated during ejection, their flight speed decreases significantly due to air resistance. Therefore, the satellite droplets and ink mist, whose flight speed decreases and whose linear energy becomes zero before reaching the recording paper PP, remain suspended in space and adhere to the head unit 3 by the flow of the jet stream. In Reference Example 1, this ink mist is lifted by the jet stream JF-A towards the head unit 3 and adheres to the head unit 3. As a result, the opening periphery of nozzles N-1[m0] and N-2[m0] is contaminated by ink adhering as ink mist, which may result in a state where ink cannot be ejected normally from nozzles N-1[m0] and N-2[m0].

[0105] In Reference Example 1, in addition to the inter-nozzle decompression space SP, decompression is also generated in the space on the -Y side compared to nozzle N-1[m0] and the space on the +Y side compared to nozzle N-2[m0]. In the following text, the airflow generated with the ejection of point Dt from nozzle N toward the space other than the inter-nozzle decompression space SP is referred to as airflow JF-B. As described above, the inter-nozzle decompression space SP is the space between the head unit 3 and the recording paper PP, which is the area where point Dt ejected from the ejection section D-1[1] to D-1[6] of nozzle row NL-1 flies and the area where point Dt ejected from the ejection section D-2[1] to D-2[6] of nozzle row NL-2 flies. The density of the flying point Dt is high, and the air pressure is easily lowered compared to the space other than the inter-nozzle decompression space SP due to the airflow from the nozzle N side toward the recording paper PP side. On the other hand, in the space on the -Y side compared to nozzle N-1[m0] and in the space on the +Y side compared to nozzle N-2[m0], even if an airflow towards the recording paper PP side is generated around the flight path of point Dt on one side, since there is no flying point Dt on the other side and the density of point Dt is lower, it is easy to replenish air from the other side, so the air pressure is difficult to decrease. Therefore, the self-jetting flow JF-A becomes a stronger airflow compared to the airflow JF-B.

[0106] Figure 11 This is a conceptual diagram illustrating the case where droplets ejected from nozzle N-1[m0] provided on head unit 3 fly as points when performing the rinsing process described in this embodiment. It also illustrates the case where droplets ejected from nozzle N-2[m0] provided on head unit 3 fly as points.

[0107] like Figure 11 As illustrated, in the rinsing process according to this embodiment, the ejector section D-1 [m0] operates as a large-volume ink ejector section DF-1, and continuously ejects three dots Dt from the nozzle N-1 [m0] provided on the ejector section D-1 [m0] within each unit period TP. On the other hand, in the rinsing process according to this embodiment, the ejector section D-2 [m0] operates as a small-volume ink ejector section DF-2, and ejects only one dot Dt from the nozzle N-2 [m0] provided on the ejector section D-2 [m0] within each unit period TP. Therefore, in the rinsing process according to this embodiment, compared with the case of Reference Example 1 described above, the density of the flying dots Dt relative to the space between the head unit 3 and the recording paper PP is lower, and no inter-nozzle decompression space SP is generated between the nozzles N-1 [m0] and N-2 [m0]. Furthermore, in the rinsing process described in this embodiment, although an airflow JF-B is generated, a self-flowing flow JF-A is not generated.

[0108] Therefore, in the rinsing process according to this embodiment, compared with Reference Example 1, the density of the dots Dt ejected from nozzles N-1 [m0] and N-2 [m0] relative to the space between the head unit 3 and the recording paper PP is lower, which can reduce the amount of ink mist thrown around the nozzle N and the amount of ink mist adhering to the head unit 3. That is, in the rinsing process according to this embodiment, compared with Reference Example 1, the risk of a state where ink cannot be ejected normally from nozzles N-1 [m0] and N-2 [m0] can be reduced.

[0109] Figure 12 In each of the unit periods TP(1) to TP(3) of the unit period TP(1) to TP(6) of the illustrated Reference Example 2, the control unit 2 supplies the head unit 3 with a printing signal SI that designates each of the ejector parts D-1[1] to D-1[6] corresponding to the nozzle line NL-1 as a large ink ejector part DF-1 and each of the ejector parts D-2[1] to D-2[6] corresponding to the nozzle line NL-2 as a discharge restriction ejector part DF-N. In addition, in each of the unit periods TP(4) to TP(6), the head unit 3 supplies the head unit 3 with a printing signal SI that designates each of the ejector parts D-1[1] to D-1[6] corresponding to the nozzle line NL-1 as a discharge restriction ejector part DF-N and each of the ejector parts D-2[1] to D-2[6] corresponding to the nozzle line NL-2 as a large ink ejector part DF-1.

[0110] As described above, in Reference Example 2, when the ejection section D-1[m0] corresponding to nozzle N-1[m0] operates as a large-volume ink ejection section DF-1, the ejection section D-2[m0] corresponding to nozzle N-2[m0] operates as a discharge-limiting ejection section DF-N. Furthermore, when the ejection section D-2[m0] corresponding to nozzle N-2[m0] operates as a large-volume ink ejection section DF-1, the ejection section D-1[m0] corresponding to nozzle N-1[m0] operates as a discharge-limiting ejection section DF-N. Therefore, in the rinsing process described in Reference Example 2, no inter-nozzle decompression space SP is generated between nozzle N-1[m0] and nozzle N-2[m0]. Therefore, according to Reference Example 2, compared to Reference Example 1, in the rinsing process, the situation where the point Dt ejected from nozzle N becomes ink mist and disperses can be suppressed.

[0111] However, in Reference Example 2, the control unit 2 stops the ejection of ink from the ejection section D-2[1] to D-2[6] corresponding to the nozzle line NL-2 during the unit period TP(1) to TP(6) of the rinsing process, and stops the ejection of ink from the ejection section D-1[1] to D-1[6] corresponding to the nozzle line NL-1 during the unit period TP(4) to TP(6).

[0112] Therefore, the time required to discharge ink from the head unit 3 as a rinsing process in Reference Example 2 is about twice the time required to discharge ink from the head unit 3 as a rinsing process in Reference Example 1.

[0113] In contrast, the control unit 2 of this embodiment, during the unit periods TP(1) to TP(3) of the unit period TP(1) to TP(6) of the rinsing process, instead of stopping the ejection of ink from the ejection sections D-2[1] to D-2[6] corresponding to the nozzle array NL-2, performs a small amount of ink discharge through each of the ejection sections D-2[1] to D-2[6]. During the unit periods TP(4) to TP(6), instead of stopping the ejection of ink from the ejection sections D-1[1] to D-1[6] corresponding to the nozzle array NL-1, a small amount of ink discharge is performed through each of the ejection sections D-1[1] to D-1[6]. Therefore, according to this embodiment, compared to Reference Example 2, the time required to discharge the desired amount of ink from the head unit 3 during the rinsing process can be shortened. That is, according to this embodiment, the improvement in print quality obtained by suppressing ink mist generation and the improvement in user convenience obtained by shortening the time required for the rinsing process can be achieved simultaneously.

[0114] B. Variations

[0115] The above methods can be modified in many ways. Specific modifications are illustrated below. Two or more methods selected from the following examples can be appropriately combined without contradiction. Furthermore, for elements whose function, purpose, and implementation are equivalent in the modifications illustrated below, the symbols referenced in the above description are used, and their detailed descriptions are omitted where appropriate.

[0116] Variation Example 1

[0117] Although the above embodiments illustrate the case where each ejector section D operates as a large-volume ink ejector section DF-1 across multiple consecutive unit periods TP, the present invention is not limited to this manner. For example, each ejector section D may also repeatedly alternate between operating as a large-volume ink ejector section DF-1 and operating as a small-volume ink ejector section DF-2 within each unit period TP during the rinsing process. For example, an ejector section D may operate as a large-volume ink ejector section DF-1 within one unit period TP, and then operate as a small-volume ink ejector section DF-2 in subsequent unit periods TP within that unit period TP.

[0118] like Figure 13 As illustrated, in each of the odd-numbered unit periods TP(1), TP(3), and TP(5) of the unit periods TP(1) to TP(6) in which the rinsing process is performed, the control unit 2 in this modified example supplies the head unit 3 with a printing signal SI that designates each of the ejector sections D-1[1] to D-1[6] corresponding to the nozzle line NL-1 as a large ink ejector section DF-1 and each of the ejector sections D-2[1] to D-2[6] corresponding to the nozzle line NL-2 as a small ink ejector section DF-2. Furthermore, in each of the even-numbered unit periods TP(2), TP(4), and TP(6) of the unit period TP(1) to TP(6) in this modified example, the control unit 2 supplies the head unit 3 with a printing signal SI that designates each of the ejection sections D-1[1] to D-1[6] corresponding to the nozzle column NL-1 as a small amount of ink ejection section DF-2 and each of the ejection sections D-2[1] to D-2[6] corresponding to the nozzle column NL-2 as a large amount of ink ejection section DF-1.

[0119] That is, in each of the odd-numbered periods of TP(1), TP(3), and TP(5), the control unit 2 of this modified example supplies a supply drive signal Vin-1[1] with a large amount of ink discharge waveform PF1 to the ejector D-1[1], thereby causing the ejector D-1[1] to operate as a large amount of ink ejector DF-1, and causing the ink in the chamber CV-1[1] to be discharged from the nozzle N-1[1] belonging to the nozzle row NL-1. In addition, in each of the odd-numbered periods of TP(1), TP(3), and TP(5), the control unit 2 of this modified example supplies a supply drive signal Vin-2[1] with a small amount of ink discharge waveform PF2 to the ejector D-2[1], thereby causing the ejector D-2[1] to operate as a small amount of ink ejector DF-2, and causing the ink in the chamber CV-2[1] to be discharged from the nozzle N-2[1] belonging to the nozzle row NL-2.

[0120] Furthermore, in each of the even-numbered units TP(2), TP(4) and TP(6) of the control unit 2 involved in this modification, by supplying the ejector units D-1[1] to D-1[6] with a supply drive signal Vin-1[1] to Vin-1[6] having a small amount of ink discharge waveform PF2, the ejector units D-1[1] to D-1[6] operate as a small amount of ink ejector unit DF-2, and the ink in the chambers CV-1[1] to CV-1[6] is discharged from the nozzles N-1[1] to N-1[6] belonging to the nozzle row NL-1. Furthermore, in each of the even-numbered units of TP(2), TP(4) and TP(6) in this modified example, the control unit 2 supplies a supply drive signal Vin-2[1] to Vin-2[6] with a large amount of ink discharge waveform PF1 to the ejection section D-2[1] to D-2[6], thereby causing the ejection section D-2[1] to D-2[6] to operate as a large amount of ink ejection section DF-1, and causing the ink in the chamber CV-2[1] to CV-2[6] to be discharged from the nozzles N-2[1] to N-2[6] belonging to the nozzle row NL-2.

[0121] Figure 14In each of the odd-numbered unit periods TP(1), TP(3), and TP(5) of the unit periods TP(1) to TP(6) in which the rinsing process is performed, the control unit 2 supplies the head unit 3 with a printing signal SI that designates each of the ejection sections D-1[1] to D-1[6] corresponding to the nozzle array NL-1 as a mass ink ejection section DF-1 and each of the ejection sections D-2[1] to D-2[6] corresponding to the nozzle array NL-2 as a discharge restriction ejection section DF-N. Furthermore, in each of the even-numbered unit periods TP(2), TP(4), and TP(6) of the unit period TP(1) to TP(6) in the unit period of performing the rinsing process, the control unit 2 in Reference Example 3 supplies the head unit 3 with a printing signal SI that designates each of the ejection sections D-1[1] to D-1[6] corresponding to the nozzle line NL-1 as the discharge restriction ejection section DF-N and each of the ejection sections D-2[1] to D-2[6] corresponding to the nozzle line NL-2 as the mass ink ejection section DF-1.

[0122] That is, in Reference Example 3, the control unit 2 stops the ejection of ink from the ejection section D-2[1] to D-2[6] corresponding to the nozzle column NL-2 during the odd-numbered unit periods TP(1) to TP(6) of the unit period TP(1) to TP(6) of the rinsing process, and stops the ejection of ink from the ejection section D-1[1] to D-1[6] corresponding to the nozzle column NL-1 during the even-numbered unit periods TP(2), TP(4) and TP(6).

[0123] Therefore, in Reference Example 3, compared with Reference Example 1, the time required to discharge the desired amount of ink from the head unit 3 during the rinsing process is longer.

[0124] In contrast, in this modified example, the control unit 2, during the odd-numbered unit periods TP(1), TP(3), and TP(5) of the unit periods TP(1) to TP(6) of the rinsing process, instead of stopping the ejection of ink from the ejection sections D-2[1] to D-2[6] corresponding to the nozzle array NL-2, performs a small amount of ink discharge through each of the ejection sections D-2[1] to D-2[6]. Similarly, during the even-numbered unit periods TP(2), TP(4), and TP(6), instead of stopping the ejection of ink from the ejection sections D-1[1] to D-1[6] corresponding to the nozzle array NL-1, performs a small amount of ink discharge through each of the ejection sections D-1[1] to D-1[6]. Therefore, according to this embodiment, compared to Reference Example 3, the time required to discharge the desired amount of ink from the head unit 3 during the rinsing process can be shortened. Furthermore, there is no situation where the density of the dots Dt relative to the space between the head unit 3 and the recording paper PP is increased, and the generation of a strong airflow toward the decompression space SP between the nozzles can be suppressed. That is, according to this embodiment, it is possible to simultaneously achieve the improvement in print quality obtained by suppressing the adhesion of ink mist to the periphery of the nozzle N, and the improvement in user convenience obtained by reducing the time required for rinsing.

[0125] As described above, in this modified example, the control unit 2, within a unit period TP(1), supplies a supply drive signal Vin-1[1] with a large amount of ink discharge waveform PF1 to the piezoelectric element PZ-1[1] among the piezoelectric elements PZ-1[1] to PZ-1[6], thereby causing the liquid in the chamber CV-1[1] to be discharged from the nozzle N-1[1]. Furthermore, by supplying a supply drive signal Vin-2[1] with a small amount of ink discharge waveform PF2, which is different from the large amount of ink discharge waveform PF1, to the piezoelectric element PZ-2[1] among the piezoelectric elements PZ-2[1] to PZ-2[6], the liquid in the chamber CV-1[1] to be discharged from the nozzle N-1[1]. The liquid in V-2[1] is discharged from the nozzle N-2[1], and during the unit period TP(2), the liquid in the chamber CV-1[1] is discharged from the nozzle N-1[1] by supplying the piezoelectric element PZ-1[1] with a supply drive signal Vin-1[1] having a small ink discharge waveform PF2 that is different from the large ink discharge waveform PF1, and the liquid in the chamber CV-2[1] is discharged from the nozzle N-2[1] by supplying the piezoelectric element PZ-2[1] with a supply drive signal Vin-2[1] having a large ink discharge waveform PF1 that is different from the small ink discharge waveform PF2, and the liquid in the chamber CV-2[1] is discharged from the nozzle N-2[1].

[0126] Therefore, according to this modified example, compared with the method of Reference Example 1, the density of the dots Dt ejected from nozzles N-1[1] and N-2[1] relative to the space between the ink head unit 3 and the recording paper PP can be reduced, and the amount of ink mist thrown up to the periphery of nozzle N can be reduced, thereby suppressing the reduction in printing quality caused by ink mist.

[0127] Furthermore, according to this modified example, the time required for rinsing can be shortened compared to the method in Reference Example 3.

[0128] In addition, in this modified example, the unit period TP(1) is an example of a "first period", the unit period TP(2) is an example of a "second period", the piezoelectric element PZ-1[1] is an example of a "first driving element", the piezoelectric element PZ-2[1] is an example of a "second driving element", the supply driving signal Vin-1[1] supplied within the unit period TP(1) is an example of a "first driving signal", the supply driving signal Vin-2[1] supplied within the unit period TP(1) is an example of a "second driving signal", the supply driving signal Vin-1[1] supplied within the unit period TP(2) is an example of a "third driving signal", the supply driving signal Vin-2[1] supplied within the unit period TP(2) is an example of a "fourth driving signal", the large ink discharge waveform PF1 is an example of a "first waveform" and a "fourth waveform", and the small ink discharge waveform PF2 is an example of a "second waveform" and a "third waveform".

[0129] Furthermore, in this modified example, the supply drive signal Vin-1[1] supplied within a unit period TP(1) includes three waveforms PAA, the supply drive signal Vin-2[1] supplied within a unit period TP(1) includes one waveform PAA, the supply drive signal Vin-1[1] supplied within a unit period TP(2) includes one waveform PAA, and the supply drive signal Vin-2[1] supplied within a unit period TP(2) includes three waveforms PAA.

[0130] Therefore, according to this modified example, compared with Reference Example 1, the amount of ink mist generated by the ink ejected from nozzle N-1[1] and nozzle N-2[1] can be reduced, and the rising of ink mist generated by point Dt ejected from nozzle N-1[m0] and nozzle N-2[m0] towards the periphery of nozzle N can be further suppressed, thereby suppressing the reduction in printing quality caused by ink mist. In addition, according to this modified example, compared with Reference Example 3, the time required for rinsing can be shortened.

[0131] Variation Example 2

[0132] Although the above-described embodiments and Modification 1 illustrate a method in which supply drive signals Vin-1[1] to Vin-1[M] with the same waveform are supplied to the ejection portions D-1[1] to D-1[M] corresponding to the nozzles N-1[1] to N-1[M] belonging to the nozzle group NL-1 during each unit period TP, and supply drive signals Vin-2[1] to Vin-2[M] with the same waveform are supplied to the ejection portions D-2[1] to D-2[M] corresponding to the nozzles N-2[1] to N-2[M] belonging to the nozzle group NL-2, the present invention is not limited to such a method. For example, it can also be set that, within each unit period TP, one of the supply drive signals Vin-1[1] to Vin-1[M] supplied to the ejector section D-1[1] to D-1[M] has a different waveform than the other supply drive signals Vin-1, and one of the supply drive signals Vin-2[1] to Vin-2[M] supplied to the ejector section D-2[1] to D-2[M] has a different waveform than the other supply drive signals Vin-2. Furthermore, for example, it can be configured such that the supply drive signal Vin-1 supplied to one of the ejector parts D-1[1] to D-1[M] has a different waveform than the supply drive signal Vin-1 supplied to the other ejector parts D-1 adjacent to one ejector part D-1. In addition, the supply drive signal Vin-2 supplied to one of the ejector parts D-2[1] to D-2[M] has a different waveform than the supply drive signal Vin-2 supplied to the other ejector parts D-2 adjacent to one ejector part D-2.

[0133] Figure 15In the illustrated modified example, the control unit 2 supplies the following printing signal SI to the head unit 3 in each of the unit periods TP(1) to TP(3) of the unit period TP(1) to TP(6) during the rinsing process: the printing signal SI is to designate each of the odd-numbered ejector parts D-1[1], D-1[3] and D-1[5] of the ejector parts D-1[1] to D-1[6] corresponding to the nozzle column NL-1 as the mass ink ejector part DF-1 and to designate each of the even-numbered ejector parts D-1[1], D-1[3] and D-1[5] as the mass ink ejector part DF-1 and to designate each of the even-numbered ejector parts D-1[1] to D-1[6] as the mass ink ejector part DF-1. The signal designates each of the output sections D-1[2], D-1[4] and D-1[6] as a small amount ink ejection section DF-2, and designates each of the odd-numbered ejection sections D-2[1] to D-2[6] corresponding to the nozzle column NL-2 as a small amount ink ejection section DF-2, and designates each of the even-numbered ejection sections D-2[2], D-2[4] and D-2[6] as a large amount ink ejection section DF-1. Furthermore, in each of the unit periods TP(4) to TP(6) of the unit period TP(1) to TP(6) in the unit period of performing the rinsing process, the control unit 2 in this modified example supplies the following printing signal SI to the head unit 3: the printing signal SI is to designate each of the odd-numbered ejector parts D-1[1], D-1[3] and D-1[5] of the ejector parts D-1[1] to D-1[6] corresponding to the nozzle column NL-1 as a small amount of ink ejector part DF-2 and to designate each of the even-numbered ejector parts D-1[1], D-1[3] and D-1[5] as a small amount of ink ejector part DF-2 and to designate each of the even-numbered ejector parts D-1[1] to D-1[6] as a small amount of ink ejector part DF-2. The signal designates each of the output sections D-1[2], D-1[4] and D-1[6] as a large ink ejection section DF-1, and designates each of the odd-numbered ejection sections D-2[1] to D-2[6] corresponding to the nozzle column NL-2 as a large ink ejection section DF-1, and designates each of the even-numbered ejection sections D-2[2], D-2[4] and D-2[6] as a small ink ejection section DF-2.

[0134] like Figure 16As illustrated, in the rinsing process described in Reference Example 1, the ejector sections D-1[1] to D-1[6] are driven by a supply drive signal Vin-1[m0] having three waveforms PAA, thereby operating as a large ink ejector section DF-1, and continuously ejecting three dots Dt from the nozzles N-1[1] to N-1[6] corresponding to the ejector sections D-1[1] to D-1[6] within each unit period TP. Therefore, in the rinsing process described in Reference Example 1, the density of dots Dt relative to the space between the head unit 3 and the recording paper PP is increased, and a nozzle decompression space SP is generated between nozzles N-1[1] and N-1[2], between nozzles N-1[2] and N-1[3], between nozzles N-1[3] and N-1[4], between nozzles N-1[4] and N-1[5], and between nozzles N-1[5] and N-1[6]. Therefore, in the rinsing process described in Reference Example 1, a self-flowing flow JF-A is generated between nozzles N-1[1] and N-1[2], between nozzles N-1[2] and N-1[3], between nozzles N-1[3] and N-1[4], between nozzles N-1[4] and N-1[5], and between nozzles N-1[5] and N-1[6]. Therefore, in the rinsing process described in Reference Example 1, the head unit 3 may be contaminated by ink adhering as ink mist, and may become unable to eject ink normally from the head unit 3.

[0135] exist Figure 17 In the rinsing process described in this modified example, for example, during a unit period TP(1), each of the odd-numbered ejector parts D-1[1], D-1[3] and D-1[5] of the ejector parts D-1[1] to D-1[6] is driven by supply drive signals Vin-1[1], Vin-1[3] and Vin-1[5] with three waveforms PAA, and thus operates as a large ink ejector part DF-1, but each of the even-numbered ejector parts D-1[2], D-1[4] and D-1[6] is driven by supply drive signals Vin-1[2], Vin-1[4] and Vin-1[6] with one waveform PAA, and thus operates as a small ink ejector part DF-2. Therefore, in the rinsing process involved in this modified example, compared with the case of Reference Example 1 above, the density of point Dt relative to the space between the head unit 3 and the recording paper PP is lower, and although airflow JF-B is generated, self-flowing flow JF-A is not generated.

[0136] Therefore, in the rinsing process of this modified example, compared with Reference Example 1, the density of the dots Dt ejected from nozzles N-1[1] to N-1[6] relative to the space between the head unit 3 and the recording paper PP is lower, thereby reducing the amount of ink mist rising around the nozzle N, and further reducing the amount of ink mist adhering to the head unit 3. Similarly, in the rinsing process of this modified example, compared with Reference Example 1, the density of the dots Dt ejected from nozzles N-2[1] to N-2[6] relative to the space between the head unit 3 and the recording paper PP is lower, thereby reducing the amount of ink mist rising around the nozzle N, and further reducing the amount of ink mist adhering to the head unit 3. That is, in the rinsing process of this modified example, compared with Reference Example 1, the risk of becoming unable to eject ink normally from nozzle N can be reduced.

[0137] Variation Example 3

[0138] Although the above-described variation 2 shows an example where the ejector section D operates as a large-volume ink ejector section DF-1 across multiple consecutive unit periods TP, the present invention is not limited to this manner. For example, the ejector section D may also alternately and repeatedly perform the operation as a large-volume ink ejector section DF-1 and the operation as a small-volume ink ejector section DF-2 for each unit period TP during the rinsing process.

[0139] Figure 18In the illustrated modified example, the control unit 2 supplies the head unit 3 with a printing signal SI during each of the odd-numbered unit periods TP(1), TP(3), and TP(5) of the unit periods TP(1) to TP(6) in performing the rinsing process. The printing signal SI is that each of the odd-numbered ejector sections D-1[1], D-1[3], and D-1[5] corresponding to the nozzle column NL-1 is designated as a large ink ejector section DF-1. The signal designates each of the even-numbered ejector sections D-1[2], D-1[4] and D-1[6] as a small amount ink ejector section DF-2, and designates each of the odd-numbered ejector sections D-2[1] to D-2[6] corresponding to the nozzle column NL-2 as a small amount ink ejector section DF-2, and designates each of the even-numbered ejector sections D-2[2], D-2[4] and D-2[6] as a large amount ink ejector section DF-1. Furthermore, in each of the even-numbered unit periods TP(2), TP(4), and TP(6) of the unit periods TP(1) to TP(6) in this modified example, the control unit 2 supplies the following printing signal SI to the head unit 3: the printing signal SI designates each of the odd-numbered ejector portions D-1[1], D-1[3], and D-1[5] of the ejector portions D-1[1] to D-1[6] corresponding to the nozzle column NL-1 as a small amount of ink ejector portion DF-2. The signal designates each of the even-numbered ejector sections D-1[2], D-1[4] and D-1[6] as a large ink ejector section DF-1, and each of the odd-numbered ejector sections D-2[1] to D-2[6] corresponding to the nozzle column NL-2 as a large ink ejector section DF-1, and each of the even-numbered ejector sections D-2[2], D-2[4] and D-2[6] as a small ink ejector section DF-2.

[0140] That is, in each of the odd-numbered units of TP(1), TP(3) and TP(5) of the control unit 2 involved in this modification, by supplying the ejector units D-1[1], D-1[3], and D-1[5] with a large amount of ink discharge waveform PF1, the ejector units D-1[1], D-1[3], and D-1[5] are operated as large amount of ink ejector units DF-1, and the ink in the chambers CV-1[1], CV-1[3], and CV-1[5] is discharged from the nozzles N-1[1], N-1[3], and N-1[5] belonging to the nozzle row NL-1. Furthermore, in each of the odd-numbered units TP(1), TP(3), and TP(5) of the control unit 2 involved in this modification, by supplying supply drive signals Vin-1[2], Vin-1[4], and Vin-1[6] with a small amount of ink discharge waveform PF2 to the ejection units D-1[2], D-1[4], and D-1[6], the ejection units D-1[2], D-1[4], and D-1[6] operate as small amount of ink ejection units DF-2, and the ink in the chambers CV-1[2], CV-1[4], and CV-1[6] is discharged from the nozzles N-1[2], N-1[4], and N-1[6] belonging to the nozzle row NL-1. Furthermore, in each of the odd-numbered units TP(1), TP(3), and TP(5) of the control unit 2 involved in this modification, by supplying supply drive signals Vin-2[1], Vin-2[3], and Vin-2[5] with a small amount of ink discharge waveform PF2 to the ejection units D-2[1], D-2[3], and D-2[5], the ejection units D-2[1], D-2[3], and D-2[5] operate as small amount ink ejection units DF-2, and the ink in the chambers CV-2[1], CV-2[3], and CV-2[5] is discharged from the nozzles N-2[1], N-2[3], and N-2[5] belonging to the nozzle row NL-2. Furthermore, in each of the odd-numbered units TP(1), TP(3), and TP(5) of the control unit 2 involved in this modification, by supplying supply drive signals Vin-2[2], Vin-2[4], and Vin-2[6] with a large amount of ink discharge waveform PF1 to the ejection units D-2[2], D-2[4], and D-2[6], the ejection units D-2[2], D-2[4], and D-2[6] operate as a large amount of ink ejection unit DF-1, and the ink in the chambers CV-2[2], CV-2[4], and CV-2[6] is discharged from the nozzles N-2[2], N-2[4], and N-2[6] belonging to the nozzle row NL-2.

[0141] Furthermore, in each of the even-numbered units TP(2), TP(4) and TP(6) of the control unit 2 involved in this modification, by supplying the ejector units D-1[1], D-1[3], D-1[5] with a small amount of ink discharge waveform PF2 to the ejector units D-1[1], D-1[3], D-1[5], the ejector units D-1[1], D-1[3], D-1[5] operate as a small amount of ink ejector unit DF-2, and the ink in the chambers CV-1[1], CV-1[3], CV-1[5] is discharged from the nozzles N-1[1], N-1[3], N-1[5] belonging to the nozzle row NL-1. Furthermore, in each of the even-numbered units of TP(2), TP(4) and TP(6) in this modified example, by supplying supply drive signals Vin-1[2], Vin-1[4], and Vin-1[6] with a large amount of ink discharge waveform PF1 to the ejection units D-1[2], D-1[4], and D-1[6], the ejection units D-1[2], D-1[4], and D-1[6] operate as a large amount of ink ejection unit DF-1, and the ink in the chambers CV-1[2], CV-1[4], and CV-1[6] is discharged from the nozzles N-1[2], N-1[4], and N-1[6] belonging to the nozzle row NL-1. Furthermore, in each of the even-numbered units TP(2), TP(4), and TP(6) of the control unit 2 involved in this modification, by supplying supply drive signals Vin-2[1], Vin-2[3], and Vin-2[5] with a large amount of ink discharge waveform PF1 to the ejection units D-2[1], D-2[3], and D-2[5], the ejection units D-2[1], D-2[3], and D-2[5] operate as a large amount of ink ejection unit DF-1, and the ink in the chambers CV-2[1], CV-2[3], and CV-2[5] is discharged from the nozzles N-2[1], N-2[3], and N-2[5] belonging to the nozzle row NL-2. Furthermore, in each of the even-numbered units of TP(2), TP(4), and TP(6) in this modified example, by supplying supply drive signals Vin-2[2], Vin-2[4], and Vin-2[6] with a small amount of ink discharge waveform PF2 to the ejection units D-2[2], D-2[4], and D-2[6], the ejection units D-2[2], D-2[4], and D-2[6] operate as small amount ink ejection units DF-2, and the ink in the chambers CV-2[2], CV-2[4], and CV-2[6] is discharged from the nozzles N-2[2], N-2[4], and N-2[6] belonging to the nozzle row NL-2.

[0142] As described above, in this modified example, during a unit period TP(1), the control unit 2 supplies a supply drive signal Vin-1[1] with a large amount of ink discharge waveform PF1 to the piezoelectric elements PZ-1[1] to PZ-1[6] corresponding to the nozzles N-1[1] to N-1[6] belonging to the nozzle column NL-1, thereby causing the liquid in the chamber CV-1[1] to be discharged from the nozzle N-1[1], and supplies a supply drive signal Vin-1[2] with a small amount of ink discharge waveform PF2 that is different from the large amount of ink discharge waveform PF1 to the piezoelectric element PZ-1[2]. 2], thereby causing the liquid in the chamber CV-1[2] to be discharged from the nozzle N-1[2]. During the unit period TP(2), the control unit 2 supplies the piezoelectric element PZ-1[1] with a supply drive signal Vin-1[1] having a small amount of ink discharge waveform PF2, thereby causing the liquid in the chamber CV-1[1] to be discharged from the nozzle N-1[1]. And by supplying the piezoelectric element PZ-1[2] with a large amount of ink discharge waveform PF1 having a different from the small amount of ink discharge waveform PF2, the liquid in the chamber CV-1[2] is discharged from the nozzle N-1[2].

[0143] Therefore, according to this modified example, compared with the method of Reference Example 1, the density of the ink dots Dt ejected from nozzle N-1[1] and nozzle N-1[2] is lower relative to the space between the head unit 3 and the recording paper PP, which can reduce the amount of ink mist rising to the periphery of nozzle N, thereby suppressing the reduction in printing quality caused by ink mist.

[0144] In addition, in this modified example, the piezoelectric element PZ-1[1] is an example of "a first driving element", the piezoelectric element PZ-1[2] is an example of "another first driving element", the supply driving signal Vin-1[1] supplied in unit period TP(1) is an example of "first driving signal", the supply driving signal Vin-1[2] supplied in unit period TP(1) is an example of "second driving signal", the supply driving signal Vin-1[1] supplied in unit period TP(2) is an example of "third driving signal", the supply driving signal Vin-1[2] supplied in unit period TP(2) is an example of "fourth driving signal", the large ink discharge waveform PF1 is an example of "first waveform" and "fourth waveform", and the small ink discharge waveform PF2 is an example of "second waveform" and "third waveform".

[0145] Furthermore, in this modified example, the supply drive signal Vin-1[1] supplied in unit period TP(1) includes three waveforms PAA, the supply drive signal Vin-1[2] supplied in unit period TP(1) includes one waveform PAA, the supply drive signal Vin-1[1] supplied in unit period TP(2) includes one waveform PAA, and the supply drive signal Vin-1[2] supplied in unit period TP(2) includes three waveforms PAA.

[0146] Therefore, according to this modified example, compared with Reference Example 1, the density of the ink dots Dt ejected from nozzle N-1[1] and nozzle N-1[2] is lower relative to the space between the head unit 3 and the recording paper PP, which can reduce the amount of ink mist rising to the periphery of nozzle N, thereby suppressing the reduction in printing quality caused by ink mist.

[0147] Furthermore, in this modified example, during a unit period TP(1), the control unit 2 supplies a supply drive signal Vin-1[1], Vin-1[3], or Vin-1[5] with a large amount of ink discharge waveform PF1 to the odd-numbered piezoelectric elements PZ-1[1], PZ-1[3], and PZ-1[5] of the piezoelectric elements PZ-1[1] to PZ-1[6] corresponding to the nozzles N-1[1] to N-1[6] belonging to the nozzle column NL-1, thereby causing the liquid in the chambers CV-1[1], CV-1[3], and CV-1[5] to flow from the nozzles N-1[1], N-1[3], or N-1[5]. Discharge, and within a unit period TP(1), by supplying even-numbered piezoelectric elements PZ-1[2], PZ-1[4] and PZ-1[6] of nozzles N-1[1] to N-1[6] belonging to nozzle group NL-1 with a small amount of ink discharge waveform PF2 that is different from the large amount of ink discharge waveform PF1, the liquid in chambers CV-1[2], CV-1[4] and CV-1[6] is discharged from nozzles N-1[2], N-1[4] or N-1[6], and within a unit period TP(1), by supplying a supply drive signal Vin-1[2], Vin-1[4] or Vin-1[6] with a small amount of ink discharge waveform PF2 that is different from the large amount of ink discharge waveform PF1, to the even-numbered piezoelectric elements PZ-1[1] to PZ-1[6] of nozzles N-1[1] to N-1[6] belonging to nozzle group NL-1, the liquid in chambers CV-1[2], CV-1[4] and CV-1[6] is discharged from nozzles N-1[2], N-1[4] or N-1[6]. [6] Discharge, and, within a unit period TP(2), by supplying a supply drive signal Vin-1[1], Vin-1[3] or Vin-1[5] with a small amount of ink discharge waveform PF2 to the odd-numbered piezoelectric elements PZ-1[1], PZ-1[3] and PZ-1[5] of the nozzles N-1[1] to N-1[6] belonging to the nozzle column NL-1, the liquid in the chambers CV-1[1], CV-1[3] and CV-1[5] is discharged from the nozzles N-1[1], N-1[3] or N-1[5], and within a unit period TP(2), by supplying the odd-numbered piezoelectric elements PZ-1[1], PZ-1[3] and PZ-1[5] with a small amount of ink discharge waveform PF2 to the nozzles N-1[1] to N-1[6] belonging to the nozzle column NL-1, the liquid in the chambers CV-1[1], CV-1[3] and CV-1[5], the liquid in the chambers CV-1[1], CV-1[3] and CV-1[5] is discharged from the nozzles N-1[1], N-1[3] or N-1[5], and within a unit period TP(2), ... During the position period TP(2), by supplying the even-numbered piezoelectric elements PZ-1[2], PZ-1[4] and PZ-1[6] corresponding to the nozzles N-1[1] to N-1[6] belonging to the nozzle column NL-1 with a large amount of ink discharge waveform PF1 that is different from the small amount of ink discharge waveform PF2, the liquid in the chambers CV-1[2], CV-1[4] and CV-1[6] is discharged from the nozzles N-1[2], N-1[4] or N-1[6].

[0148] Therefore, according to this modified example, compared with Reference Example 1, the reduction in print quality caused by ink mist can be suppressed. Furthermore, according to this modified example, compared with Reference Example 3, the time required for the rinsing process can be shortened.

[0149] In addition, in this modified example, one of the odd-numbered nozzles N-1[1], N-1[3] and N-1[5] is an example of "odd-numbered first nozzle", one of the even-numbered nozzles N-1[2], N-1[4] and N-1[6] is an example of "even-numbered first nozzle", the piezoelectric element PZ-1 corresponding to the odd-numbered first nozzle is an example of "odd-numbered first driving element", and the piezoelectric element PZ-1 corresponding to the even-numbered first nozzle is an example of "even-numbered first driving element". During the unit period TP( 1) is an example of a supply drive signal Vin-1 supplied to the odd-numbered first drive element as a “first drive signal”, TP(1) is an example of a supply drive signal Vin-1 supplied to the even-numbered first drive element as a “second drive signal”, TP(2) is an example of a supply drive signal Vin-1 supplied to the odd-numbered first drive element as a “third drive signal”, and TP(2) is an example of a supply drive signal Vin-1 supplied to the even-numbered first drive element as a “fourth drive signal”.

[0150] Furthermore, in this modified example, the supply drive signal Vin-1 supplied to the odd-numbered first drive element in unit period TP(1) includes three waveforms PAA, the supply drive signal Vin-1 supplied to the even-numbered first drive element in unit period TP(1) includes one waveform PAA, the supply drive signal Vin-1 supplied to the odd-numbered first drive element in unit period TP(2) includes one waveform PAA, and the supply drive signal Vin-1 supplied to the even-numbered first drive element in unit period TP(2) includes three waveforms PAA.

[0151] Therefore, according to this modified example, compared with Reference Example 1, the density of ink dots Dt ejected from nozzles N-1[1] and N-2[1] relative to the space between the head unit 3 and the recording paper PP is lower, which can reduce the amount of ink mist rising to the periphery of nozzle N, thereby suppressing the reduction in print quality caused by ink mist. In addition, according to this modified example, compared with Reference Example 3, the time required for rinsing can be shortened.

[0152] Furthermore, in this modified example, during a unit period TP(1), the control unit 2 supplies a supply drive signal Vin-1[1], Vin-1[3] or Vin-1[5] with a large amount of ink discharge waveform PF1 to the odd-numbered piezoelectric elements PZ-1[1], PZ-1[3] or PZ-1[5] of the piezoelectric elements PZ-1[1] to PZ-1[6] corresponding to the nozzles N-1[1] to N-1[6] belonging to the nozzle column NL-1, thereby causing the liquid in the chambers CV-1[1], CV-1[3] and CV-1[5] to be discharged from the nozzles N-1[1], N-1[3] or N-1[5]. Furthermore, during the unit period TP(1), by supplying even-numbered piezoelectric elements PZ-1[2], PZ-1[4], and PZ-1[6] with a small amount of ink discharge waveform PF2 that is different from the large amount of ink discharge waveform PF1 to the even-numbered piezoelectric elements PZ-1[1] to PZ-1[6] corresponding to nozzles N-1[1] to N-1[6] belonging to nozzle column NL-1, the liquid in the chambers CV-1[2], CV-1[4], and CV-1[6] is discharged from nozzles N-1[2], N-1[4], or N-1[6], respectively, with a supply drive signal Vin-1[2], Vin-1[4], or Vin-1[6], which is different from the large amount of ink discharge waveform PF1, the liquid in the chambers CV-1[2], CV-1[4], and CV-1[6] is discharged from nozzles N-1[2], N-1[4], or N-1[6]. [6] Discharge, and, during the unit period TP(1), by supplying a supply drive signal Vin-2[1], Vin-2[3] or Vin-2[5] with a small amount of ink discharge waveform PF2 to the odd-numbered piezoelectric elements PZ-2[1], PZ-2[3] and PZ-2[5] of the nozzles N-2[1] to N-2[6] belonging to the nozzle column NL-2, corresponding to the nozzles N-2[1] to N-2[6], the liquid in the chambers CV-2[1], CV-2[3] and CV-2[5] is discharged from the nozzles N-2[1], N-2[3] or N-2[5], and, in the unit period TP(1), by supplying the odd-numbered piezoelectric elements PZ-2[1], PZ-2[3] and PZ-2[5] with a small amount of ink discharge waveform PF2, the liquid in the chambers CV-2[1], CV-2[3] and CV-2[5] is discharged from the nozzles N-2[1], N-2[3] or N-2[5], and, in During the unit period TP(1), by supplying the even-numbered piezoelectric elements PZ-2[2], PZ-2[4] and PZ-2[6] with a large amount of ink discharge waveform PF1 to the even-numbered piezoelectric elements PZ-2[1] to PZ-2[6] corresponding to the nozzles N-2[1] to N-2[6] belonging to the nozzle column NL-2, the liquid in the chambers CV-2[2], CV-2[4] and CV-2[6] is discharged from the nozzles N-2[2], N-2[4] or N-2[6], and during the unit period TP(2),By supplying a supply drive signal Vin-1[1], Vin-1[3] or Vin-1[5] with a small amount of ink discharge waveform PF2 to the odd-numbered piezoelectric elements PZ-1[1], PZ-1[3] and PZ-1[5] of the nozzles N-1[1] to N-1[6] belonging to the nozzle column NL-1, the liquid in the chambers CV-1[1], CV-1[3] and CV-1[5] is discharged from the nozzles N-1[1], N-1[3] or N-1[5], and within a unit period TP(2), By supplying even-numbered piezoelectric elements PZ-1[2], PZ-1[4], and PZ-1[6], which correspond to nozzles N-1[1] to N-1[6] belonging to nozzle column NL-1, with a large ink discharge waveform PF1 that is different from the small ink discharge waveform PF2, the liquid in chambers CV-1[2], CV-1[4], and CV-1[6] is discharged from nozzles N-1[2], N-1[4], or N-1[6]. Furthermore, during the unit period TP(2), by supplying the odd-numbered piezoelectric elements PZ-2[1], PZ-2[3], and PZ-2[5] with a large amount of ink discharge waveform PF1 to the piezoelectric elements PZ-2[1] to PZ-2[6] corresponding to the nozzles N-2[1] to N-2[6] belonging to the nozzle column NL-2, the liquid in the chambers CV-2[1], CV-2[3], and CV-2[5] is discharged from the nozzles N-2[1], N-2[3], or N-2[5]. Furthermore, during the unit period TP(2), by supplying a supply drive signal Vin-2[2], Vin-2[4] or Vin-2[6] with a small amount of ink discharge waveform PF2 to the even-numbered piezoelectric elements PZ-2[1] to PZ-2[6] corresponding to the nozzles N-2[1] to N-2[6] belonging to the nozzle column NL-2, such that the liquid in the chambers CV-2[2], CV-2[4] and CV-2[6] is discharged from the nozzles N-2[2], N-2[4] or N-2[6].

[0153] Therefore, according to this modified example, compared with Reference Example 1, the reduction in print quality caused by ink mist can be suppressed. Furthermore, according to this modified example, compared with Reference Example 3, the time required for the rinsing process can be shortened.

[0154] Furthermore, in this modified example, the supply drive signal Vin-1 supplied to the odd-numbered first drive element in unit period TP(1) includes three waveforms PAA, the supply drive signal Vin-1 supplied to the even-numbered first drive element in unit period TP(1) includes one waveform PAA, the supply drive signal Vin-1 supplied to the odd-numbered first drive element in unit period TP(2) includes one waveform PAA, and the supply drive signal Vin-1 supplied to the even-numbered first drive element in unit period TP(2) includes three waveforms PAA.

[0155] Therefore, according to this modified example, compared with Reference Example 1, the density of ink dots Dt ejected from nozzles N-1[1] and N-2[1] relative to the space between the head unit 3 and the recording paper PP is lower, which can reduce the amount of ink mist rising to the periphery of nozzle N, thereby suppressing the reduction in print quality caused by ink mist. In addition, according to this modified example, compared with Reference Example 3, the time required for rinsing can be shortened.

[0156] Variation Example 4

[0157] Although examples of a large ink discharge waveform PF1 comprising three waveforms PAA and a small ink discharge waveform PF2 comprising one waveform PAA have been shown in the above embodiments and variations 1 to 3, the present invention is not limited to such a manner. For example, the waveforms included in the large ink discharge waveform PF1 and the waveforms included in the small ink discharge waveform PF2 may also be different.

[0158] exist Figure 19 In the illustrated modified example, when the independently specified signal Sd[m] is represented by the value "5", the connection state specifying circuit 310 sets the connection state specifying signal Qa[m] to a high level during control periods TQ1, TQ2, and TQ3. In this case, the switch Wa[m] is turned on throughout the TPF during the rinsing unit period. Therefore, the ejector D[m] is driven by the supply drive signal Vin[m] having waveforms PA1, PA2, and PA3 during the TPF during the rinsing unit period, and ejects ink equivalent to the amount of ink ξ4 discharged in large quantities.

[0159] Furthermore, when the independently specified signal Sd[m] is represented as the value "6", the connection state specifying circuit 310 sets the connection state specifying signal Qb[m] to a high level during control periods TQ1 and TQ2. In this case, the switch Wb[m] is turned on during control periods TQ1 and TQ2. Therefore, the ejector section D[m] is driven by the supply drive signal Vin[m] with waveforms PB1 and PB2 during the rinsing unit TPF, and ejects a small amount of ink ξ6 compared to the ink amount ξ4.

[0160] That is, in this modified example, the waveform PF1 of a large amount of ink discharge is a waveform composed of waveforms PA1, PA2 and PA3, and the waveform PF2 of a small amount of ink discharge is a waveform composed of waveforms PB1 and PB2.

[0161] As described above, in this variation, the first driving signal includes three waveforms PAA, the second driving signal includes two waveforms PBB, the third driving signal includes two waveforms PBB, and the fourth driving signal includes three waveforms PAA. That is, in this variation, the waveforms contained in the first driving signal are different from those contained in the second driving signal, the waveforms contained in the first driving signal are different from those contained in the third driving signal, the waveforms contained in the second driving signal are different from those contained in the fourth driving signal, and the waveforms contained in the third driving signal are different from those contained in the fourth driving signal.

[0162] Therefore, according to this modified example, compared with the method in Reference Example 1 where each of the first to fourth drive signals includes three waveforms PAA, the density of the ink dots Dt ejected from the nozzle N relative to the space between the head unit 3 and the recording paper PP is lower, which can reduce the amount of ink mist that rises to the periphery of the nozzle N, thereby suppressing the reduction in print quality caused by ink mist.

[0163] Furthermore, in this modified example, when the piezoelectric element PZ[m] is driven by the supply drive signal Vin[m] with waveform PAA, the speed of point Dt ejected from nozzle N[m] is faster than when the piezoelectric element PZ[m] is driven by the supply drive signal Vin[m] with waveform PBB.

[0164] Therefore, according to this modified example, compared with the method in Reference Example 1 where each of the first to fourth drive signals includes three waveforms PAA, the density of the ink dots Dt ejected from the nozzle N relative to the space between the head unit 3 and the recording paper PP is lower, which can reduce the amount of ink mist that rises to the periphery of the nozzle N, thereby suppressing the reduction in print quality caused by ink mist.

[0165] In addition, in this variant example, waveform PAA is an example of a "first drive pulse", and waveform PBB is an example of a "second drive pulse".

[0166] Furthermore, in this modified example, when the piezoelectric element PZ[m] is driven by the supply drive signal Vin[m] with waveform PAA, the amount of point Dt ejected from the nozzle N[m] is greater than the amount of point Dt ejected from the nozzle [m] when the piezoelectric element PZ[m] is driven by the supply drive signal Vin[m] with waveform PBB.

[0167] Therefore, according to this modified example, compared with the method in Reference Example 1 where each of the first to fourth drive signals includes three waveforms PAA, the density of the ink dots Dt ejected from the nozzle N relative to the space between the head unit 3 and the recording paper PP is lower, which can reduce the amount of ink mist that rises to the periphery of the nozzle N, thereby suppressing the reduction in print quality caused by ink mist.

[0168] Modified Example 5

[0169] Although in the above embodiments and variations 1 to 5, the waveforms PA1, PA2, and PA3 included in the drive signal Com-A have substantially the same shape, and the waveforms PB1 and PB2 included in the drive signal Com-B have substantially the same shape, the present invention is not limited to such a manner. For example, waveforms PA1 and PA2 may also be waveforms with different shapes, as may waveforms PA1 and PA3, and also waveforms PA2 and PA3. Furthermore, waveforms PB1 and PB2 may also be waveforms with different shapes.

[0170] Variation Example 6

[0171] Although the embodiments and variations 1 to 5 described above show examples in which the drive signal Com-A includes three ejection waveforms PA1, PA2, and PA3, and the drive signal Com-B includes two ejection waveforms PB1 and PB2, as the ejection waveforms for ejecting ink from nozzle N, the present invention is not limited to such a manner. For example, the drive signal Com-A may simply include at least one ejection waveform, and the drive signal Com-B may simply include at least one ejection waveform.

[0172] Variation Example 7

[0173] Although examples of driving signal Com including two signals, driving signal Com-A and driving signal Com-B, have been shown in the above embodiments and variations 1 to 6, the present invention is not limited to such a manner.

[0174] For example, the drive signal Com may include only drive signal Com-A and exclude drive signal Com-B. In this case, drive signal Com-A only needs to include at least two ejection waveforms.

[0175] Furthermore, for example, the drive signal Com may include only the drive signal Com-B and exclude the drive signal Com-A. In this case, the drive signal Com-B only needs to include at least two ejection waveforms.

[0176] In addition, for example, the drive signal Com may also include, in addition to drive signals Com-A and Com-B, a drive signal having a different waveform than drive signals Com-A and Com-B.

[0177] Variation Example 8

[0178] Although examples of two nozzle rows NL, NL-1 and NL-2, have been shown in the above embodiments and variations 1 to 7, the present invention is not limited to this configuration. The head unit 3 may have only one nozzle row NL-1, or it may have three or more nozzle rows NL.

[0179] Furthermore, when the head unit 3 has three or more nozzle rows NL, it is assumed that the aforementioned nozzle rows NL-1 and NL-2 are adjacent nozzle rows NL. That is, when the head unit 3 has three or more nozzle rows NL, it is assumed that there are no other nozzle rows NL between nozzle rows NL-1 and nozzle rows NL-2. When the head unit 3 has three or more nozzle rows NL, the piezoelectric element PZ corresponding to the nozzle row NL arranged on the +Y axis side relative to nozzle row NL-2 can be driven in the same way as the piezoelectric element PZ-1 corresponding to nozzle row NL-1, or it can be driven in a different way than the piezoelectric element PZ-1 corresponding to nozzle row NL-1 and the piezoelectric element PZ-2 corresponding to nozzle row NL-2. In summary, when the head unit 3 has three or more nozzle rows NL, by setting the driving of the piezoelectric element PZ corresponding to the nozzle rows NL located on both sides of the decompression space SP between each nozzle to the structure of the above embodiment and its variations, it is possible to suppress the self-jetting flow and thus suppress the adhesion of ink mist in the head unit 3.

[0180] Variation Example 9

[0181] Although the nozzle arrays NL1 and NL-2 included in the head unit 3 have been described in the above embodiments and variations 1 to 8, in the case where multiple head units 3 are arranged in the Y-axis direction, in order to suppress the adhesion of ink mist to the head unit 3 caused by the self-flowing flow, the piezoelectric element PZ corresponding to the nozzle arrays NL on both sides of the nozzle arrays NL located between the head units 3 is driven in the above embodiments and variations. This can suppress the self-flowing flow and thus suppress the adhesion of ink mist to the head unit 3.

[0182] Variation Example 10

[0183] Although the inkjet printer 1 has four head units 3 in the above-described embodiments and variations 1 to 9, the present invention is not limited to this configuration. The inkjet printer 1 may also have one or more but no more than three head units 3, and furthermore, the inkjet printer 1 may have five or more head units 3.

[0184] Variation Example 11

[0185] Although the above embodiments and variations 1 to 10 show an example of an inkjet printer 1 as a serial printer, the present invention is not limited to such a manner. The inkjet printer 1 may also be a so-called line printer in which a plurality of nozzles N are arranged in the head unit 3 in a manner that extends wider than the width of the recording paper PP.

[0186] Symbol Explanation

[0187] 1…Inkjet printer; 2…Control unit; 3…Head unit; 4…Drive signal generation unit; 7…Conveyor unit; 8…Maintenance unit; 31…Supply circuit; 32…Recording head; D…Ejector section; N…Nozzle.

Claims

1. A method for maintaining a head unit, characterized in that, The head unit includes: A first nozzle array having a plurality of first nozzles arranged along a first axis and ejecting liquid; The second nozzle array has a plurality of second nozzles arranged along a second axis parallel to the first axis and spraying liquid. A plurality of first pressure chambers are disposed corresponding to the plurality of first nozzles and are filled with liquid; Multiple second pressure chambers are arranged corresponding to the multiple second nozzles and filled with liquid; A plurality of first driving elements are disposed corresponding to the plurality of first pressure chambers, and cause the pressure in the corresponding first pressure chamber to change; Multiple second driving elements are provided corresponding to the multiple second pressure chambers, and cause the pressure in the corresponding second pressure chamber to change; The supply unit supplies drive signals to the plurality of first drive elements and the plurality of second drive elements. In the maintenance method, During the first period, By supplying a first drive signal with a first waveform to one of the plurality of first drive elements, liquid in one of the plurality of first pressure chambers corresponding to the first drive element is discharged from one of the plurality of first nozzles corresponding to the first pressure chamber. By supplying a second drive signal with a second waveform different from the first waveform to one of the plurality of second drive elements, liquid in one of the plurality of second pressure chambers corresponding to the first second drive element is discharged from one of the plurality of second nozzles corresponding to the first second pressure chamber. During a second period, which is different from the first period. By supplying a third drive signal having a third waveform different from the first waveform to the first drive element, the liquid in the first pressure chamber is discharged from the first nozzle, and By supplying a fourth drive signal having a fourth waveform different from the second and third waveforms to the second drive element, the liquid in the second pressure chamber is discharged from the second nozzle. During the first period, By supplying the second drive signal to another first drive element among the plurality of first drive elements, corresponding to other first nozzles included in the plurality of first nozzles and adjacent to the first nozzle, liquid in the other first pressure chambers of the plurality of first pressure chambers corresponding to the other first drive elements is discharged from the other first nozzles. During the second period, By supplying the fourth drive signal to the other first drive element, the liquid in the other first pressure chamber is discharged from the other first nozzle.

2. The maintenance method as described in claim 1, characterized in that, The first driving element is one of the odd-numbered first driving elements among the plurality of first driving elements that corresponds to the odd-numbered first nozzle among the plurality of first nozzles. The other first driving element is one of the even-numbered first driving elements among the plurality of first driving elements that corresponds to the even-numbered first nozzle among the plurality of first nozzles. During the first period, By supplying the first drive signal to the odd-numbered first drive element, the liquid in the odd-numbered first pressure chamber corresponding to the odd-numbered first drive element in the plurality of first pressure chambers is discharged from the odd-numbered first nozzle, and By supplying the second driving signal to the even-numbered first driving element, the liquid in the even-numbered first pressure chamber corresponding to the even-numbered first driving element is discharged from the even-numbered first nozzle. During the second period, By supplying the third drive signal to the odd-numbered first drive element, the liquid in the odd-numbered first pressure chamber is discharged from the odd-numbered first nozzle, and By supplying the fourth driving signal to the even-numbered first driving element, the liquid in the even-numbered first pressure chamber is discharged from the even-numbered first nozzle.

3. The maintenance method as described in claim 2, characterized in that, The second driving element is one of the odd-numbered second driving elements among the plurality of second driving elements that corresponds to the odd-numbered second nozzle among the plurality of second nozzles. During the first period, By supplying the second drive signal to the odd-numbered second drive element among the plurality of second drive elements, the liquid in the odd-numbered second pressure chamber corresponding to the odd-numbered second drive element in the plurality of second pressure chambers is discharged from the odd-numbered second nozzle, and By supplying the first drive signal to the even-numbered second drive element corresponding to the even-numbered second nozzle among the plurality of second drive elements, the liquid in the even-numbered second pressure chamber corresponding to the even-numbered second drive element in the plurality of second pressure chambers is discharged from the even-numbered second nozzle. During the second period, By supplying the fourth drive signal to the odd-numbered second drive element, the liquid in the odd-numbered second pressure chamber is discharged from the odd-numbered second nozzle, and By supplying the third driving signal to the even-numbered second driving element, the liquid in the even-numbered second pressure chamber is discharged from the even-numbered second nozzle.

4. The maintenance method as described in claim 1, characterized in that, The first drive signal includes a first drive pulse, which is a pulse that drives the first drive element in a manner that causes liquid to be ejected from the first nozzle. The second drive signal includes a second drive pulse of a second number different from the first number, the second drive pulse being a pulse that drives the second drive element in a manner that causes liquid to be ejected from the second nozzle. The third driving signal includes a third driving pulse of a third number different from the first number, wherein the third driving pulse is a pulse that drives the first driving element in a manner that causes liquid to be ejected from the first nozzle. The fourth driving signal includes a fourth driving pulse of a fourth number that is different from the second number and the third number. The fourth driving pulse is a pulse that drives the second driving element in a manner that causes liquid to be ejected from the second nozzle.

5. The maintenance method as described in claim 4, characterized in that, The waveforms of the first driving pulse, the second driving pulse, the third driving pulse, and the fourth driving pulse have the same shape. The first number and the fourth number are the same. The second number and the third number are the same.

6. The maintenance method as described in claim 1, characterized in that, The first driving signal includes a first driving pulse, which is a pulse that drives the first driving element in a manner that causes liquid to be ejected from the first nozzle. The second drive signal includes a second drive pulse, which is a pulse that drives the second drive element in a manner that causes liquid to be ejected from the second nozzle. The third driving signal includes a third driving pulse, which is a pulse that drives the first driving element in a manner that causes liquid to be ejected from the first nozzle. The fourth driving signal includes a fourth driving pulse, which is a pulse that drives the second driving element in a manner that causes liquid to be ejected from the second nozzle. The waveform of the first driving pulse is different from the waveform of the second driving pulse. The waveform of the first driving pulse is different from the waveform of the third driving pulse. The waveform of the second driving pulse is different from that of the fourth driving pulse. The waveform of the third driving pulse is different from that of the fourth driving pulse.

7. The maintenance method as described in claim 6, characterized in that, The waveform of the first driving pulse has the same shape as the waveform of the fourth driving pulse. The waveform of the second driving pulse has the same shape as the waveform of the third driving pulse.

8. The maintenance method as described in claim 6, characterized in that, When the first driving element is driven by the first driving pulse, the speed of the liquid ejected from the first nozzle is faster than the speed of the liquid ejected from the second nozzle when the second driving element is driven by the second driving pulse.

9. The maintenance method as described in claim 6, characterized in that, When the first driving element is driven by the first driving pulse, the amount of liquid ejected from the first nozzle is greater than the amount of liquid ejected from the second nozzle when the second driving element is driven by the second driving pulse.

10. The maintenance method as described in claim 1, characterized in that, The first waveform and the fourth waveform have the same shape. The second waveform and the third waveform have the same shape.

11. The maintenance method as described in claim 1, characterized in that, The first nozzle column and the second nozzle column are adjacent to each other.

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