Liquid dispensing device

Abstract

To suppress the degradation of image quality formed on the medium, even when applying a recovery waveform to restore the nozzle state. [Solution] A liquid dispensing device comprising: a plurality of piezoelectric elements; a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements; a plurality of nozzles from which liquid can be discharged by the pressure applied by each of the plurality of pressure chambers; a drive circuit that drives each of the plurality of piezoelectric elements; and a first wiring and a second wiring that can be switched on or off whether or not to electrically connect to each of the plurality of piezoelectric elements, wherein the drive circuit applies a discharge waveform to one piezoelectric element via the first wiring to drive one piezoelectric element to the extent that liquid is discharged; a micro-vibration waveform to one piezoelectric element via the second wiring to drive one piezoelectric element to the extent that liquid is not discharged; and a recovery waveform to one piezoelectric element via the first wiring to drive one piezoelectric element to the extent that the nozzle state is restored.

Description

Technical Field

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

Background Art

[0002] In a liquid ejection device that ejects a liquid such as ink onto a medium such as printing paper, thickening of the liquid due to evaporation of a solvent such as moisture contained in the liquid is a problem. For example, Patent Document 1 discloses a liquid ejection device having a piezoelectric element, a pressure chamber that applies pressure to the internal liquid by driving the piezoelectric element, and a nozzle through which the liquid can be ejected by this pressure, and applying a micro-vibration waveform that drives the piezoelectric element to such an extent that the liquid is not ejected in order to eliminate local thickening near the nozzle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When bubbles occur in the nozzle, ejection failure may occur. Therefore, in order to restore the state of the nozzle, it is conceivable to apply a micro-vibration waveform to the piezoelectric element. However, with the micro-vibration waveform, the bubbles in the nozzle cannot be sufficiently removed, and there is a risk that the state of the nozzle cannot be restored. On the other hand, if the intensity of the micro-vibration waveform is increased or the degree of agitation of the liquid in the nozzle is increased, there is a risk of causing adverse effects on other nozzles and degrading the quality of the image formed on the medium.

Means for Solving the Problems

[0005] A liquid dispensing device according to one aspect of the present disclosure is a liquid dispensing device using a liquid dispensing head having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements, a plurality of nozzles from which liquid can be dispensed by the pressure applied by each of the plurality of pressure chambers, a drive circuit that drives each of the plurality of piezoelectric elements, a first wiring that can be switched on or off by control of the drive circuit to electrically connect to each of the plurality of piezoelectric elements, and a second wiring that can be switched on or off by control of the drive circuit separately from the first wiring to electrically connect to each of the plurality of piezoelectric elements, wherein the drive circuit applies a discharge waveform to one of the plurality of piezoelectric elements via the first wiring to drive the piezoelectric element to the extent that liquid is dispensed, a micro-vibration waveform that drives the piezoelectric element to the extent that liquid is not dispensed via the second wiring to the piezoelectric element, and a recovery waveform that drives the piezoelectric element to the extent that the state of the nozzle corresponding to the piezoelectric element is restored via the first wiring to the piezoelectric element.

[0006] Furthermore, a liquid dispensing device according to one aspect of the present disclosure is a liquid dispensing device using a liquid dispensing head having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving the plurality of piezoelectric elements, a plurality of nozzles from which liquid can be dispensed by the pressure applied by each of the plurality of pressure chambers, a drive circuit that drives each of the plurality of piezoelectric elements, a first wiring that can be switched on or off by control of the drive circuit to electrically connect to each of the plurality of piezoelectric elements, and a second wiring that can be switched on or off by control of the drive circuit separately from the first wiring to electrically connect to each of the plurality of piezoelectric elements, wherein the drive circuit applies a discharge waveform to one of the plurality of piezoelectric elements via the first wiring to drive the piezoelectric element to the extent that liquid is dispensed, a micro-vibration waveform that drives the piezoelectric element to the extent that liquid is not dispensed via the second wiring to the piezoelectric element, and a recovery waveform that has an intensity higher than the intensity of the micro-vibration waveform and lower than the intensity of the discharge waveform to the piezoelectric element via the first wiring.

[0007] Furthermore, a liquid dispensing device according to one aspect of the present disclosure is a liquid dispensing device using a liquid dispensing head having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements, a plurality of nozzles from which liquid can be discharged by the pressure applied by each of the plurality of pressure chambers, a plurality of individual flow paths, a common supply flow path that is in common communication with the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths, a common discharge flow path that is in common communication with the plurality of individual flow paths and discharges liquid from the plurality of individual flow paths, and a drive circuit that drives each of the plurality of piezoelectric elements, wherein each of the plurality of individual flow paths is a liquid dispensing device using a liquid dispensing head The drive circuit has one or more pressure chambers and communicates with one of the plurality of nozzles, and applies to the piezoelectric element a discharge waveform that drives the piezoelectric element to the extent that liquid is discharged, a micro-vibration waveform that drives the piezoelectric element to the extent that liquid is not discharged, and a recovery waveform that drives the piezoelectric element to the extent that restores the state of the nozzle corresponding to the piezoelectric element, wherein the recovery waveform drives the piezoelectric element to the extent that it restores the state of the nozzle corresponding to the piezoelectric element by causing bubbles generated in the nozzle corresponding to the piezoelectric element to flow to the individual flow path having a pressure chamber corresponding to the piezoelectric element. [Brief explanation of the drawing]

[0008] [Figure 1] A functional block diagram showing an example of the configuration of the inkjet printer 1 according to the first embodiment. [Figure 2] A schematic diagram illustrating inkjet printer 1. [Figure 3] Disassembled perspective view of the HC head tip. [Figure 4] Cross-sectional view of line IV-IV in Figure 3. [Figure 5] Plan view of the head tip HC as seen in the Z2 direction. [Figure 6] A magnified cross-sectional view of the vicinity of the piezoelectric element PZq. [Figure 7] A block diagram showing an example of the configuration of the head chip HC_A1. [Figure 8]A diagram showing a timing chart to explain the operation during the recording period Tu[i]. [Figure 9] An explanatory diagram illustrating the generation of connection status specification signals SLa[m], SLb[m], and SLc[m]. [Figure 10] This diagram shows the state near nozzle Nz before the recovery operation is performed. [Figure 11] This diagram shows the state near nozzle Nz after the recovery operation has been performed. [Figure 12] A flowchart illustrating the operation of the control unit 6. [Figure 13] This figure illustrates an example of the flowchart shown in Figure 12. [Figure 14] A flowchart showing the operation of the control unit 6 in the second embodiment. [Figure 15] A diagram showing a timing chart to explain the operation during the recording period Tu[i] when a recording operation should be performed. [Figure 16] A diagram showing a timing chart to explain the operation during the recording period Tu[i] when the recording operation should not be performed. [Figure 17] A flowchart illustrating the operation of the control unit 6 in the third embodiment. [Modes for carrying out the invention]

[0009] The embodiments for implementing this disclosure will be described below with reference to the drawings. However, the dimensions and scale of each part in each drawing have been appropriately altered from those of the actual parts. Furthermore, the embodiments described below are preferred examples of this disclosure and are subject to various technically preferred limitations. However, the scope of this disclosure is not limited to these embodiments unless otherwise stated in the following description.

[0010] 1. First Embodiment 1-1. Overview of Inkjet Printer 1 Referring to FIGS. 1 and 2, the configuration of the inkjet printer 1 will be described. FIG. 1 is a functional block diagram showing an example of the configuration of the inkjet printer 1 according to the first embodiment. FIG. 2 is a schematic diagram illustrating the inkjet printer 1. The inkjet printer 1 is an inkjet printing apparatus that ejects ink, which is an example of a "liquid", onto a medium PP. The medium PP is typically printing paper, but any printing target such as a resin film or fabric can be used as the medium PP. The inkjet printer 1 is an example of a "liquid ejection device".

[0011] As illustrated in FIG. 2, the inkjet printer 1 includes a liquid container 14 that stores ink. As the liquid container 14, for example, a cartridge that is detachable from the inkjet printer 1, a bag-shaped ink pack formed of a flexible film, or an ink tank that can be refilled with ink can be adopted. A plurality of types of inks having different colors are stored in the liquid container 14.

[0012] As illustrated in FIG. 1, the inkjet printer 1 includes six ejection drive signal generation circuits 21, two fine vibration drive signal generation circuits 22, a liquid ejection head HU, a control unit 6, a storage unit 5, a conveyance mechanism 7, a movement mechanism 8, and a circulation mechanism 15. The liquid ejection head HU includes six head chips HC. Hereinafter, each of the six ejection drive signal generation circuits 21 and each of the two fine vibration drive signal generation circuits 22 may be referred to as a drive signal generation circuit 2 without distinction. Also, the signal generated by the drive signal generation circuit 2 may be referred to as a drive signal. Specific examples of the drive signal will be described later.

[0013] The inkjet printer 1 includes, as six ejection drive signal generation circuits 21, an ejection drive signal generation circuit 21_A1, an ejection drive signal generation circuit 21_A2, an ejection drive signal generation circuit 21_B1, an ejection drive signal generation circuit 21_B2, an ejection drive signal generation circuit 21_C1, and an ejection drive signal generation circuit 21_C2. The inkjet printer 1 includes, as two fine vibration drive signal generation circuits 22, a fine vibration drive signal generation circuit 22_1 and a fine vibration drive signal generation circuit 22_2.

[0014] The control unit 6 is a processing circuit such as a CPU or an FPGA. Here, CPU is an abbreviation for Central Processing Unit, and FPGA is an abbreviation for Field Programmable Gate Array. The control unit 6 controls each element of the inkjet printer 1.

[0015] The storage unit 5 is configured to include a volatile memory such as a RAM and a non-volatile memory such as a ROM, an EEPROM, or a PROM, and stores various information such as the number of sheets information indicating the number of printed sheets of the image to be formed by the inkjet printer 1, the media information indicating the size of the medium PP, and the control program of the inkjet printer 1. The print data Img, the number of sheets information, and the media information are transmitted from the host computer to the inkjet printer 1. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. PROM is an abbreviation for Programmable ROM.

[0016] The transport mechanism 7, under the control of the control unit 6, transports the medium PP in the Y1 direction along the Y axis. Hereinafter, the Y1 direction and the Y2 direction opposite to the Y1 direction will be collectively referred to as the direction along the Y axis. Also below, the X1 direction along the X axis intersecting the Y axis and the X2 direction opposite to the X1 direction will be collectively referred to as the direction along the X axis. Also below, the Z1 direction along the Z axis intersecting the X and Y axes and the Z2 direction opposite to the Z1 direction will be collectively referred to as the direction along the Z axis. In this embodiment, as an example, the case in which the X axis, Y axis, and Z axis are orthogonal to each other will be described. However, this disclosure is not limited to this embodiment. The X axis, Y axis, and Z axis only need to intersect each other. Also below, viewing in the direction along the Z axis may be described as a "plan view".

[0017] The transport mechanism 7 comprises a transport roller (not shown) whose rotation axis is parallel to the X axis, a transport motor (not shown) that rotates the transport roller under the control of the control unit 6, and an encoder (not shown) that outputs a signal to the control unit 6 corresponding to the amount of rotation of the transport roller, and the transport position of the medium PP that is transported in accordance with the rotation drive of the transport roller.

[0018] The moving mechanism 8 reciprocates the liquid discharge head HU in the X1 and X2 directions under the control of the control unit 6. As shown in Figure 2, the moving mechanism 8 comprises a storage case 8a for housing the liquid discharge head HU, an endless belt 8b to which the storage case 8a is fixed, a motor (not shown) that rotates the endless belt 8b under the control of the control unit 6, and an encoder (not shown) that outputs a signal to the control unit 6 corresponding to the amount of rotation of the motor and the position of the liquid discharge head HU which is moved in accordance with the rotation drive of the motor. The liquid container 14 and the circulation mechanism 15 may also be housed in the storage case 8a together with the liquid discharge head HU.

[0019] The inkjet printer 1 transports the medium PP in the sub-scanning direction Y1 and moves the liquid ejection head HU in the main scanning directions X1 and X2, while ejecting ink from the nozzle Nz to form an image on the medium PP. Hereinafter, the operation of ejecting ink onto the medium PP may be referred to as the "recording operation".

[0020] The circulation mechanism 15, under the control of the control unit 6, supplies the ink stored in the liquid container 14 to the supply channel RB1 provided in the liquid discharge head HU. Furthermore, under the control of the control unit 6, the circulation mechanism 15 recovers the ink stored in the discharge channel RB2 provided in the liquid discharge head HU and recirculates the recovered ink back into the supply channel RB1. The supply channel RB1 and the discharge channel RB2 will be described later in Figure 4.

[0021] The liquid discharge head HU has six head tips HC, namely head tip HC_A1, head tip HC_A2, head tip HC_B1, head tip HC_B2, head tip HC_C1, and head tip HC_C2. Hereinafter, head tips HC_A1, HC_A2, HC_B1, HC_B2, HC_C1, and HC_C2 may be referred to simply as head tip HC.

[0022] Each of the six head tips HC has one nozzle row Ln. Nozzle row Ln has M nozzles Nz, where M is an integer greater than or equal to 2. For the sake of simplicity, each of the six head tips HC has one nozzle row Ln. Specifically, as shown in Figure 2, head tip HC_A1 has nozzle row LA1, head tip HC_A2 has nozzle row LA2, head tip HC_B1 has nozzle row LB1, head tip HC_B2 has nozzle row LB2, head tip HC_C1 has nozzle row LC1, and head tip HC_C2 has nozzle row LC2. Hereafter, nozzle rows LA1, LA2, LB1, LB2, LC1, and LC2 may be referred to simply as nozzle row Ln without distinction.

[0023] The aforementioned recording operation is the operation in which one or more nozzles Nz of the liquid discharge head HU discharge onto the medium PP.

[0024] 1-2. Overview of Head Tip HC As shown in Figure 2, each of the six head tips HC extends along the Y-axis and is arranged in a line along the X-axis. The direction of extension of the nozzle row Ln of each of the six head tips HC coincides with the direction of extension of the head tip HC. Therefore, the nozzle row Ln of each of the six head tips HC also extends along the Y-axis and is arranged in a line along the X-axis. However, the arrangement of the head tips HC is not limited to that shown in Figure 2. In this embodiment, the liquid discharge head HU has six nozzle rows Ln, but it may have one or more nozzle rows Ln.

[0025] The following describes the overview of the head tip HC with reference to Figures 3 to 6. Figure 3 is an exploded perspective view of the head tip HC, Figure 4 is a cross-sectional view of line IV-IV in Figure 3, and Figure 5 is a plan view of the head tip HC in the Z2 direction.

[0026] As illustrated in Figures 3 and 4, the head chip HC comprises a nozzle substrate 60, compliance sheets 61 and 62, a communication plate 20, a pressure chamber substrate 30, a diaphragm 40, a storage chamber forming substrate 50, and a wiring substrate 80.

[0027] As illustrated in Figure 3, the nozzle substrate 60 is a plate-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and has M nozzles Nz formed on it. Here, "substantially parallel" is a concept that includes not only cases where they are perfectly parallel, but also cases where they can be considered parallel considering the error. The nozzle substrate 60 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology such as etching. However, known materials and manufacturing methods can be arbitrarily used for the manufacture of the nozzle substrate 60. The nozzles Nz are through holes provided in the nozzle substrate 60. In this embodiment, as an example, we assume that in the nozzle substrate 60, M nozzles Nz are provided to form a nozzle row Ln extending in the Y-axis direction.

[0028] As illustrated in Figures 3 and 4, a communication plate 20 is provided in the Z1 direction of the nozzle substrate 60. The communication plate 20 is a plate-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and forms an ink flow path.

[0029] Specifically, the communication plate 20 has one supply channel RA1 and one discharge channel RA2. Of these, the supply channel RA1 communicates with the supply channel RB1 (described later) and is provided to extend in the Y-axis direction. The discharge channel RA2 communicates with the discharge channel RB2 (described later) and is provided to extend in the Y-axis direction in the X2 direction when viewed from the supply channel RA1.

[0030] Furthermore, the communication plate 20 is provided with M nozzle channels RN corresponding one-to-one with M nozzles Nz, M communication channels RR1 corresponding one-to-one with M nozzles Nz, M communication channels RR2 corresponding one-to-one with M nozzles Nz, M communication channels RK1 corresponding one-to-one with M nozzles Nz, M communication channels RK2 corresponding one-to-one with M nozzles Nz, one communication channel RX1 common to M nozzles Nz, and one communication channel RX2 common to M nozzles Nz. The communication plate 20 may also be provided with M communication channels RX1 corresponding one-to-one with M nozzles Nz, and M communication channels RX2 corresponding one-to-one with M nozzles Nz.

[0031] Of these, the communication channel RX1 communicates with the supply channel RA1 and is provided to extend in the X-axis direction in the X2 direction when viewed from the supply channel RA1. The communication channel RK1 communicates with the communication channel RX1 at its end in the X2 direction and is provided to extend in the Z-axis direction. The communication channel RR1 is provided to extend in the Z-axis direction in the X2 direction when viewed from the communication channel RK1.

[0032] Furthermore, the communication channel RX2 communicates with the discharge channel RA2 and is provided to extend in the X-axis direction in the X1 direction when viewed from the discharge channel RA2. Furthermore, the communication channel RK2 communicates with the communication channel RX2 at its end in the Z2 direction and is provided to extend in the Z-axis direction. Furthermore, the communication channel RR2 is provided to extend in the Z-axis direction in the X1 direction when viewed from the communication channel RK2 and in the X2 direction when viewed from the communication channel RR1.

[0033] Furthermore, the nozzle channel RN connects the communication channels RR1 and RR2, and is provided to extend in the X-axis direction, in the X2 direction when viewed from the communication channel RR1 and in the X1 direction when viewed from the communication channel RR2. The nozzle channel RN communicates with the nozzle Nz corresponding to the nozzle channel RN.

[0034] The connecting plate 20 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology. However, known materials and manufacturing methods can be arbitrarily used in the manufacture of the connecting plate 20.

[0035] As illustrated in Figures 3 and 4, a pressure chamber substrate 30 is provided in the Z1 direction of the communication plate 20. The pressure chamber substrate 30 is a plate-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and forms an ink flow path.

[0036] Specifically, the pressure chamber substrate 30 has M pressure chambers CB1 corresponding one-to-one with M nozzles Nz, and M pressure chambers CB2 corresponding one-to-one with M nozzles Nz. Of these, pressure chamber CB1 connects the communication channel RK1 and the communication channel RR1, and when viewed from the Z-axis direction, it connects the X1-direction end of the communication channel RK1 and the X2-direction end of the communication channel RR1, extending in the X-axis direction. Pressure chamber CB2 connects the communication channel RK2 and the communication channel RR2, and when viewed from the Z-axis direction, it connects the X2-direction end of the communication channel RK2 and the X1-direction end of the communication channel RR2, extending in the X-axis direction.

[0037] The pressure chamber substrate 30 is manufactured, for example, by processing a silicon single-crystal substrate using semiconductor manufacturing technology. However, known materials and manufacturing methods can be arbitrarily used in the manufacture of the pressure chamber substrate 30.

[0038] In the following, the ink flow path connecting the supply flow path RA1 and the discharge flow path RA2 may be referred to as the individual flow path RJ. As illustrated in Figure 5, the connecting flow path RX1 and the connecting flow path RX2 are connected by M individual flow paths RJ that correspond one-to-one with M nozzles Nz. Each individual flow path RJ includes, as described above, a connecting flow path RK1 that connects to the connecting flow path RX1, a pressure chamber CB1 that connects to the connecting flow path RK1, a connecting flow path RR1 that connects to the pressure chamber CB1, a nozzle flow path RN that connects to the connecting flow path RR1, a connecting flow path RR2 that connects to the nozzle flow path RN, a pressure chamber CB2 that connects to the connecting flow path RR2, and a connecting flow path RK2 that connects to the pressure chamber CB2. In this embodiment, as an example, it is assumed that each individual flow path RJ extends in the X-axis direction.

[0039] As can be seen from Figure 4, the individual channel RJ is provided by the pressure chamber substrate 30 and the connecting plate 20.

[0040] As illustrated in Figures 3 and 4, a diaphragm 40 is provided in the Z1 direction of the pressure chamber substrate 30. The diaphragm 40 is a plate-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and is an elastically vibrating member.

[0041] As illustrated in Figures 3 and 4, the diaphragm 40 is provided with M piezoelectric elements PZ1 corresponding one-to-one to M pressure chambers CB1 in the Z1 direction, and M piezoelectric elements PZ2 corresponding one-to-one to M pressure chambers CB2. Hereinafter, piezoelectric elements PZ1 and PZ2 may be collectively referred to as piezoelectric elements PZq without distinction. Piezoelectric elements PZq are passive elements that deform in response to potential changes in the drive signal generated by the drive signal generation circuit 2. Hereinafter, the subscript "q" may be added to the symbols indicating components or signals in the head chip HC that correspond to piezoelectric elements PZq.

[0042] Figure 6 is an enlarged cross-sectional view of the vicinity of the piezoelectric element PZq. As illustrated in Figure 6, the piezoelectric element PZq is a laminate in which a piezoelectric material ZMq is interposed between a lower electrode ZDq to which a predetermined reference potential VBS is supplied, and an upper electrode ZUq to which a drive signal generated by the drive signal generation circuit 2 is supplied. The piezoelectric element PZq is, for example, the portion where the lower electrode ZDq, the upper electrode ZUq, and the piezoelectric material ZMq overlap when viewed in the Z2 direction. A pressure chamber CBq is also provided in the Z2 direction of the piezoelectric element PZq.

[0043] As described above, the piezoelectric element PZq is driven and deformed in response to the potential change of the drive signal generated by the drive signal generation circuit 2. The diaphragm 40 vibrates in conjunction with the deformation of the piezoelectric element PZq. When the diaphragm 40 vibrates, the pressure inside the pressure chamber CBq fluctuates. As the pressure inside the pressure chamber CBq fluctuates, the ink filled inside the pressure chamber CBq is ejected from the nozzle Nz via the communication channel RRq and the nozzle channel RN.

[0044] As illustrated in Figures 3 and 4, a wiring board 80 is mounted on the surface of the diaphragm 40 facing the Z1 direction. The wiring board 80 is a component for electrically connecting the control unit 6 and the head chip HC. A flexible wiring board such as an FPC or FFC is preferably used as the wiring board 80. Here, FPC is an abbreviation for Flexible Printed Circuit, and FFC is an abbreviation for Flexible Flat Cable. A drive circuit 81 is mounted on the wiring board 80. The drive circuit 81 is an electrical circuit that, under the control of a printed signal SI, switches whether or not to supply a drive signal generated by the drive signal generation circuit 2 to the piezoelectric element PZq. As illustrated in Figure 6, the drive circuit 81 supplies a drive signal generated by the drive signal generation circuit 2 to the upper electrode ZUq of the piezoelectric element PZq via wiring 810.

[0045] In this embodiment, when ejecting ink from nozzle Nz, it is assumed that the waveform of the drive signal supplied by the drive circuit 81 to piezoelectric element PZ1 corresponding to nozzle Nz and the waveform of the drive signal supplied by the drive circuit 81 to piezoelectric element PZ2 corresponding to nozzle Nz are substantially the same. Here, "substantially the same" is a concept that includes not only cases where they are completely identical, but also cases where they can be considered identical when errors are taken into account.

[0046] In the following, to distinguish each of the M nozzles Nz contained in a single head chip HC, they may be referred to sequentially as stage 1, stage 2, ..., stage M. Also, a nozzle Nz of stage m may be referred to as nozzle Nz[m]. In the following description, the variable m is an integer between 1 and M. Furthermore, if the components or signals of the inkjet printer 1 correspond to the stage number m of nozzle Nz[m], the subscript [m] indicating that it corresponds to the stage number m may be added to the code representing the component or signal. For example, the pressure chamber CBq corresponding to the piezoelectric element PZq[m] is the pressure chamber CBq[m] to which pressure is applied by the piezoelectric element PZq[m]. Furthermore, the nozzle Nz corresponding to the piezoelectric element PZq[m] is the nozzle Nz[m] that communicates with the pressure chamber CBq[m] to which pressure is applied by the piezoelectric element PZq[m]. Furthermore, if piezoelectric element PZq[m] corresponds to "one piezoelectric element", then pressure chamber CBq[m] corresponds to "the pressure chamber corresponding to one piezoelectric element", and nozzle Nz[m] corresponds to "the nozzle corresponding to one piezoelectric element". Individual channel RJ, in which pressure chamber CBq[m] is provided, corresponds to "an individual channel in which a pressure chamber corresponding to one piezoelectric element is provided".

[0047] As illustrated in Figures 3 and 4, a storage chamber forming substrate 50 is provided in the Z1 direction of the communication plate 20. The storage chamber forming substrate 50 is an elongated member in the Y-axis direction, and an ink flow path is formed therein. Specifically, the storage chamber forming substrate 50 has one supply channel RB1 and one discharge channel RB2. Of these, the supply channel RB1 communicates with the supply channel RA1 and is provided to extend in the Y-axis direction in the Z1 direction when viewed from the supply channel RA1. The discharge channel RB2 communicates with the discharge channel RA2 and is provided to extend in the Y-axis direction in the Z1 direction when viewed from the discharge channel RA2 and in the X2 direction when viewed from the supply channel RB1. Furthermore, the storage chamber forming substrate 50 is provided with an inlet 51 that communicates with the supply channel RB1 and an outlet 52 that communicates with the discharge channel RB2. Ink is supplied to the supply channel RB1 from the liquid container 14 via the inlet 51. The ink stored in the discharge channel RB2 is recovered via the outlet 52. The storage chamber forming substrate 50 is also provided with an opening 50K. Inside the opening 50K are a pressure chamber substrate 30, a diaphragm 40, and a wiring substrate 80. The storage chamber forming substrate 50 is formed, for example, by injection molding of a resin material. However, known materials and manufacturing methods can be arbitrarily used for the manufacture of the storage chamber forming substrate 50.

[0048] In this embodiment, the ink supplied from the liquid container 93 to the inlet 51 flows into the supply channel RA1 via the supply channel RB1. A portion of the ink that flows into the supply channel RA1 flows into the pressure chamber CB1 via the communication channels RX1 and RK1. A portion of the ink that flows into the pressure chamber CB1 flows into the pressure chamber CB2 via the communication channel RR1, the nozzle channel RN, and the communication channel RR2. A portion of the ink that flows into the pressure chamber CB2 is discharged from the outlet 52 via the communication channels RK2, RX2, the discharge channel RA2, and the discharge channel RB2. When the piezoelectric element PZ1 is driven by the drive signal generated by the drive signal generation circuit 2, a portion of the ink filling the inside of the pressure chamber CB1 is discharged from the nozzle Nz via the communication channel RR1 and the nozzle channel RN. Furthermore, when the piezoelectric element PZ2 is driven by the drive signal generated by the drive signal generation circuit 2, a portion of the ink filling the pressure chamber CB2 is ejected from the nozzle Nz via the communication channel RR2 and the nozzle channel RN.

[0049] As illustrated in Figures 3 and 4, a compliance sheet 61 is provided on the surface of the communication plate 20 facing the Z2 direction, so as to block the supply channel RA1, the communication channel RX1, and the communication channel RK1. The compliance sheet 61 is made of an elastic material and absorbs pressure fluctuations of the ink in the supply channel RA1, the communication channel RX1, and the communication channel RK1. In addition, a compliance sheet 62 is provided on the Z2 side surface of the communication plate 20 so as to block the discharge channel RA2, the communication channel RX2, and the communication channel RK2. The compliance sheet 62 is made of an elastic material and absorbs pressure fluctuations of the ink in the discharge channel RA2, the communication channel RX2, and the communication channel RK2.

[0050] As described above, the head chip HC according to this embodiment circulates ink from the communication channel RX1 through the individual channel RJ to the communication channel RX2. Therefore, in this embodiment, even if there is a period during which the ink inside the pressure chamber CBq is not discharged from the nozzle Nz, it is possible to prevent the ink from remaining stagnant inside the pressure chamber CBq and in the nozzle channel RN, etc. Thus, in this embodiment, even if there is a period during which the ink inside the pressure chamber CBq is not discharged from the nozzle Nz, it is possible to suppress the viscosity increase of the ink inside the pressure chamber CBq, and it is possible to prevent the occurrence of discharge abnormalities in which ink cannot be discharged from the nozzle Nz due to ink viscosity increase.

[0051] As shown in Figure 4, a common supply channel Rsup is formed by supply channel RA1, supply channel RB1, and communication channel RX1. The common supply channel Rsup communicates in common with M individual channels RJ and supplies ink to each of the M individual channels RJ. Also, as shown in Figure 4, a common discharge channel Rdch is formed by discharge channel RA2, discharge channel RB2, and communication channel RX2. The common discharge channel Rdch communicates in common with M individual channels RJ and discharges ink from each of the M individual channels RJ.

[0052] Furthermore, the head tip HC according to this embodiment can discharge both the ink filled inside pressure chamber CB1 and the ink filled inside pressure chamber CB2 from the nozzle Nz. Therefore, the head tip HC according to this embodiment makes it possible to increase the amount of ink discharged from the nozzle Nz compared to, for example, an embodiment in which only the ink filled inside one pressure chamber CBq is discharged from the nozzle Nz.

[0053] As described above, each of the M individual flow paths RJ has two pressure chambers CBq out of 2 × M and communicates with one nozzle Nz out of M nozzles Nz. The two pressure chambers CBq provided in one individual flow path RJ correspond to "one or more pressure chambers provided in each of the multiple individual flow paths." However, one individual flow path RJ may not have two pressure chambers CBq, but only one pressure chamber CBq.

[0054] Let's return to the explanation in Figures 1 and 2. The control unit 6 generates a printing signal SI for controlling the head chip HC, a waveform specification signal dCom for controlling the drive signal generation circuit 2, a signal for controlling the transport mechanism 7, and a signal for controlling the moving mechanism 8.

[0055] Here, the waveform specification signal dCom is a digital signal that defines the waveform of the ejection drive signal Com or the micro-vibration drive signal BSD. The ejection drive signal Com and the micro-vibration drive signal BSD are analog signals for driving the piezoelectric element PZq. The drive signal generation circuit 2 includes a DA conversion circuit and generates the ejection drive signal Com or the micro-vibration drive signal BSD having the waveform defined by the waveform specification signal dCom.

[0056] Specifically, the control unit 6 outputs a waveform specification signal dCom_A1 that defines the discharge drive signal Com_A1 to the discharge drive signal generation circuit 21_A1. The control unit 6 outputs a waveform specification signal dCom_A2 that defines the discharge drive signal Com_A2 to the discharge drive signal generation circuit 21_A2. The control unit 6 outputs a waveform specification signal dCom_B1 that defines the discharge drive signal Com_B1 to the discharge drive signal generation circuit 21_B1. The control unit 6 outputs a waveform specification signal dCom_B2 that defines the discharge drive signal Com_B2 to the discharge drive signal generation circuit 21_B2. The control unit 6 outputs a waveform specification signal dCom_C1 that defines the discharge drive signal Com_C1 to the discharge drive signal generation circuit 21_C1. The control unit 6 outputs a waveform specification signal dCom_C2 that defines the discharge drive signal Com_C2 to the discharge drive signal generation circuit 21_C2. The control unit 6 outputs a waveform specification signal dCom_D1 that defines the micro-vibration drive signal BSD_1 to the micro-vibration drive signal generation circuit 22_1. The control unit 6 outputs a waveform specification signal dCom_D2 that defines the micro-vibration drive signal BSD_2 to the micro-vibration drive signal generation circuit 22_2.

[0057] Furthermore, the print signal SI is a digital signal used to specify the type of operation of the piezoelectric element PZq. Specifically, the print signal SI specifies whether or not to supply an ejection drive signal Com to the piezoelectric element PZq, or a micro-vibration drive signal BSD to the piezoelectric element PZq, thereby specifying whether or not ink will be ejected from the nozzle Nz when the piezoelectric element PZq is driven.

[0058] As can be seen from Figure 1, the head chip HC_A1 is supplied with the ejection drive signal Com_A1 generated by the ejection drive signal generation circuit 21_A1, the ejection drive signal Com_A2 generated by the ejection drive signal generation circuit 21_A2, and the micro-vibration drive signal BSD_1 generated by the micro-vibration drive signal generation circuit 22_1. The head chip HC_A2 is supplied with the ejection drive signal Com_A1, the ejection drive signal Com_A2, and the micro-vibration drive signal BSD_2 generated by the micro-vibration drive signal generation circuit 22_2.

[0059] The head chip HC_B1 is supplied with the ejection drive signal Com_B1 generated by the ejection drive signal generation circuit 21_B1, the ejection drive signal Com_B2 generated by the ejection drive signal generation circuit 21_B2, and the micro-vibration drive signal BSD_1. The head chip HC_B2 is supplied with the ejection drive signal Com_B1, the ejection drive signal Com_B2, and the micro-vibration drive signal BSD_2.

[0060] The head chip HC_C1 is supplied with the ejection drive signal Com_C1 generated by the ejection drive signal generation circuit 21_C1, the ejection drive signal Com_C2 generated by the ejection drive signal generation circuit 21_C2, and the micro-vibration drive signal BSD_1. The head chip HC_C2 is supplied with the ejection drive signal Com_C1, the ejection drive signal Com_C2, and the micro-vibration drive signal BSD_2.

[0061] In the following description, the ejection drive signals Com_A1, Com_A2, Com_B1, Com_B2, Com_C1, and Com_C2 may be referred to simply as "ejection drive signal Com" without distinction. Similarly, the micro-vibration drive signals BSD_1 and BSD_2 may be referred to simply as "micro-vibration drive signal BSD" without distinction. Furthermore, the waveform of the ejection drive signal Com that drives the piezoelectric element PZq to the extent that ink is ejected may be referred to as the "ejection waveform." The operation of applying the ejection waveform to the piezoelectric element PZq may be referred to as the "ejection operation." The aforementioned recording operation can also be described as the operation in which one or more piezoelectric elements PZq of all the piezoelectric elements PZq of the liquid ejection head HU perform the ejection operation, or in other words, the operation of applying the ejection waveform to one or more piezoelectric elements PZq. Furthermore, the waveform of the micro-vibration drive signal BSD that drives the piezoelectric element PZq to the extent that ink is not ejected may be referred to as the "micro-vibration waveform WB". The operation of applying the micro-vibration waveform WB to the piezoelectric element PZq may be referred to as the "micro-vibration operation".

[0062] 1-3. Head Tip HC Configuration The configuration of the head chip HC_A1 will be described below, with reference to Figure 7.

[0063] Figure 7 is a block diagram showing an example of the configuration of the head chip HC_A1. The head chip HC_A1 also includes internal wiring LHa to which the ejection drive signal Com_A1 is supplied from the ejection drive signal generation circuit 21_A1, internal wiring LHb to which the ejection drive signal Com_A2 is supplied from the ejection drive signal generation circuit 21_A2, internal wiring LHc to which the micro-vibration drive signal BSD_1 is supplied from the micro-vibration drive signal generation circuit 22_1, and internal wiring LHd to which the reference potential Vbs is supplied.

[0064] As shown in Figure 7, the drive circuit 81 comprises M switches SWa[1] to SWa[M], M switches SWb[1] to SWb[M], M switches SWc[q][1] to SWc[M], and a connection state specification circuit 82 that specifies the connection state of each switch. For example, transmission gates can be used as each switch.

[0065] Based on at least some of the print signal SI, latch signal LAT, and change signal CH supplied from the control unit 6, the connection status specification circuit 82 generates a connection status specification signal SLa[m] that specifies whether switch SWa[m] is on or off, a connection status specification signal SLb[m] that specifies whether switch SWb[m] is on or off, and a connection status specification signal SLc[m] that specifies whether switch SWc[m] is on or off, for each of the values ​​from 1 to M that variable m can take.

[0066] For each variable m from 1 to M, the switch SWa[m] switches whether or not to electrically connect the internal wiring LHa and the upper electrode Zu[m] of the piezoelectric element PZq[m], depending on the connection status signal SLa[m]. For example, the switch SWa[m] turns on when the connection status signal SLa[m] is high level and turns off when it is low level.

[0067] For each variable m from 1 to M, the switch SWb[m] switches whether or not to electrically connect the internal wiring LHb and the upper electrode Zu[m] of the piezoelectric element PZq[m], depending on the connection status signal SLb[m]. For example, the switch SWb[m] turns on when the connection status signal SLb[m] is high level and turns off when it is low level.

[0068] For each variable m from 1 to M, the switch SWc[m] switches whether or not to electrically connect the internal wiring LHc and the upper electrode Zu[m] of the piezoelectric element PZq[m], depending on the connection status signal SLc[m]. For example, the switch SWc[m] turns on when the connection status signal SLc[m] is high level and turns off when it is low level.

[0069] In addition, among the discharge drive signal Com_A1, discharge drive signal Com_A2, and micro-vibration drive signal BSD_1, the signal actually supplied to the piezoelectric element PZq[m] via switch SWa[m], switch SWb[m], or switch SWc[m] may be referred to as the supply drive signal Vin[m].

[0070] As described above, the internal wiring LHa, internal wiring LHb, and internal wiring LHc can be switched on or off to connect to each of the 2 × M piezoelectric elements PZq by the control of the drive circuit 81. In the first embodiment, internal wiring LHb corresponds to the "first wiring," and internal wiring LHc corresponds to the "second wiring."

[0071] The configurations of head chips HC_A1 and HC_A2 are the same as those of head chip HC_A1, and therefore are not shown in the diagram. Compared to the configuration of head chip HC_A1, head chip HC_A2 has internal wiring in which the micro-vibration drive signal BSD_2 is supplied from the micro-vibration drive signal generation circuit 22_2 instead of the internal wiring LHc. Compared to the configuration of head chip HC_A1, head chip HC_B1 has internal wiring in which the ejection drive signal Com_B1 is supplied from the ejection drive signal generation circuit 21_B1 instead of the internal wiring LHa, and internal wiring in which the ejection drive signal Com_B2 is supplied from the ejection drive signal generation circuit 21_B2 instead of the internal wiring LHb. Compared to the configuration of head chip HC_B1, head chip HC_B2 has internal wiring in which the micro-vibration drive signal BSD_2 is supplied from the micro-vibration drive signal generation circuit 22_2 instead of the internal wiring LHc. The configuration of head chip HC_C1 is as follows, compared to the configuration of head chip HC_A1: it has internal wiring in which the ejection drive signal Com_C1 is supplied from the ejection drive signal generation circuit 21_C1 instead of internal wiring LHa, and internal wiring in which the ejection drive signal Com_C2 is supplied from the ejection drive signal generation circuit 21_C2 instead of internal wiring LHb. The configuration of head chip HC_C2 is as follows, compared to the configuration of head chip HC_C1: it has internal wiring in which the micro-vibration drive signal BSD_2 is supplied from the micro-vibration drive signal generation circuit 22_2 instead of internal wiring LHc.

[0072] 1-4.Micro-vibration waveform WB In inkjet printer 1, a problem arises when the ink becomes thicker due to the evaporation of solvents such as water contained in the ink. When the ink thickens, ejection failure occurs. Ejection failure is a condition in which, even when the piezoelectric element PZq is driven by the ejection drive signal Com to eject ink from the nozzle Nz, the ink cannot be ejected in the manner specified by the ejection drive signal Com, and the ejection characteristics of the nozzle Nz are reduced. Ejection characteristics include, for example, the ejection amount and / or ejection speed. In this embodiment, in order to eliminate localized thickening near the nozzle Nz, a micro-vibration drive signal BSD is applied to the piezoelectric element PZq. The micro-vibration drive signal BSD has a micro-vibration waveform WB that drives the piezoelectric element PZq to the extent that ink is not ejected.

[0073] As will be explained in more detail later, the intensity of the micro-vibration waveform WB is lower than the intensity of the output waveform possessed by the output drive signal Com. Here, the intensity of the waveform is indicated, for example, by the potential difference between the lowest potential and the highest potential within the waveform. Hereafter, this potential difference may be referred to as the potential difference ΔVh. A higher waveform intensity means that the potential difference ΔVh of the waveform is large. However, the intensity of the waveform is not limited to the potential difference ΔVh; for example, it may also be the slope of the potential change within the waveform. The rate of potential change is the absolute value of the magnitude obtained by dividing the potential difference resulting from the change in potential within the waveform by the length of the period during which the potential changed.

[0074] Since the intensity of the micro-vibration waveform WB is lower than the intensity of the discharge waveform, the manufacturer of the liquid discharge head HU can set the withstand voltage of the internal wiring LHc that supplies the micro-vibration waveform WB lower than the withstand voltage of the internal wiring LHa and internal wiring LHb that supply the discharge waveform. Here, the withstand voltage of the wiring refers to the magnitude of the voltage that can be applied to the wiring. The greater the magnitude of the voltage that can be applied to the wiring, the higher the withstand voltage of the wiring. To increase the magnitude of the voltage that can be applied to the wiring, one can shorten the length of the wiring or make the wiring thicker. Shortening the length of the wiring is not always feasible. Also, making the wiring thicker increases the cost of the wiring and the size of the substrate on which the wiring is placed. For the above reasons, if the voltage applied to the wiring is small, it is preferable for the withstand voltage of the wiring to be low. Therefore, it is preferable that the withstand voltage of the internal wiring LHc be lower than the withstand voltage of the internal wiring LHa and internal wiring LHb. Figure 7 shows the current-tolerance performance of internal wiring LHa, internal wiring LHb, and internal wiring LHc, indicated by their wire thickness. Of the three internal wirings, internal wiring LHa, being the thickest wire, has the highest current-tolerance performance, while internal wiring LHc, being the thinnest wire, has the lowest.

[0075] Ink ejection failure can occur not only due to ink viscosity but also when air bubbles form within the nozzle Nz. When air bubbles form within the nozzle Nz, it is conceivable to attempt to restore the nozzle Nz's condition by applying a micro-vibration waveform WB to the piezoelectric element PZq to remove the bubbles. However, there was a risk that the micro-vibration waveform WB could not sufficiently remove the air bubbles within the nozzle Nz, thus failing to restore its condition. On the other hand, increasing the intensity of the micro-vibration waveform WB to enhance ink agitation within the nozzle Nz could, in certain situations such as during recording, transmit pressure fluctuations to other nozzles Nz, potentially causing problems such as fluctuations in the amount and speed of ink ejected from other nozzles Nz. Fluctuations in the amount and speed of ink ejected from other nozzles Nz can degrade the image quality formed on the PP medium.

[0076] Therefore, it is conceivable to supply a recovery waveform WK to the piezoelectric element PZq to drive it to the extent that it restores the state of the nozzle Nz. If this recovery waveform WK is supplied to the piezoelectric element PZq via the internal wiring LHc, it may exceed the current resistance performance of the internal wiring LHc, potentially causing problems such as short circuits with other wiring. Therefore, in the first embodiment, the recovery waveform WK is supplied to the piezoelectric element PZq via the internal wiring LHb. Hereinafter, the operation of supplying the recovery waveform WK to the piezoelectric element PZq may be referred to as the "recovery operation".

[0077] 1-5. Operation of the head tip HC In this embodiment, the operating period of the inkjet printer 1 includes one or more recording periods Tu. Hereinafter, the operating period of the inkjet printer 1 will be described as having I recording periods Tu, where I is an integer of 1 or more. Furthermore, the i-th recording period Tu may be referred to as recording period Tu[i], where i is an integer from 1 to I. In this embodiment, the inkjet printer 1 is assumed to perform driving of the piezoelectric element PZq in one of the following operations: ejection operation, micro-vibration operation, or recovery operation, during each recording period Tu[i]. Generally, the inkjet printer 1 forms the image shown in the print data Img by repeatedly performing recording operations over I continuous or intermittent recording periods Tu, ejecting ink from each nozzle one or more times.

[0078] Figure 8 is a timing chart illustrating the operation of inkjet printer 1 during the recording period Tu[i]. Figure 8 illustrates the drive signals supplied to the head chip HC_A1, namely the ejection drive signal Com_A1, the ejection drive signal Com_A2, and the micro-vibration drive signal BSD_1.

[0079] As shown in Figure 8, the control unit 6 outputs a latch signal LAT having a pulse PlsL and a change signal CH having a pulse PlsC. This allows the control unit 6 to define the recording period Tu[i] as the period from the rising edge of pulse PlsL to the rising edge of the next pulse PlsL. The specific length or period of the recording period Tu[i] is not particularly limited. Furthermore, the control unit 6 divides the recording period Tu[i] into two control periods, Tu1 and Tu2, using pulse PlsC.

[0080] The printed signal SI includes individual designation signals Sd[1] to Sd[M] that specify the driving mode of the piezoelectric elements PZq[1] to PZq[M] during each recording period Tu[i]. The control unit 6 then supplies the printed signal SI, including the individual designation signals Sd[1] to Sd[M], to the connection state designation circuit 82 in synchronization with the clock signal CL prior to the start of each recording period Tu[i]. For each integer m from 1 to M, the connection state designation circuit 82 generates connection state designation signals SLa[m], Sd[m], and Sd[m] during the recording period Tu[i] based on the individual designation signal Sd[m].

[0081] The individual designation signal Sd[m] is a signal that, for each recording period Tu[i], specifies one of the following operations for the piezoelectric element PZq[m]: an ejection operation that ejects an amount of ink equivalent to a large dot, an ejection operation that ejects an amount of ink equivalent to a medium dot, an ejection operation that ejects an amount of ink equivalent to a small dot, a micro-vibration operation, and a recovery operation.

[0082] As shown in Figure 6, the ejection drive signal generation circuit 21_A1 outputs an ejection drive signal Com_A1 having two high-volume ejection waveforms WL during one recording period Tu. One of the two high-volume ejection waveforms WL is provided within the control period Tu1, and the other high-volume ejection waveform WL is provided within the control period Tu2.

[0083] As shown in Figure 6, the ejection drive signal generation circuit 21_A2 outputs an ejection drive signal Com_A2 having a recovery waveform WK and a small-volume ejection waveform WS during one recording period Tu. The recovery waveform WK is provided within the control period Tu1, and the small-volume ejection waveform WS is provided within the control period Tu2. Hereafter, the large-volume ejection waveform WL and the small-volume ejection waveform WS may be referred to simply as the ejection waveform without distinction.

[0084] As shown in Figure 6, the micro-vibration drive signal generation circuit 22_1 outputs a micro-vibration drive signal BSD_1 having two micro-vibration waveforms WB in one recording period Tu. One of the two micro-vibration waveforms WB is present within the control period Tu1, and the other micro-vibration waveform WB is present within the control period Tu2.

[0085] For the sake of simplicity, the shapes of the two high-volume ejection waveforms WL are approximately identical, but may differ from each other. Similarly, the shapes of the two micro-vibration waveforms WB are approximately identical, but may differ from each other. The start and end potentials of the high-volume ejection waveform WL, the low-volume ejection waveform WS, the recovery waveform WK, and the micro-vibration waveform WB are the reference potential V0. When the high-volume ejection waveform WL and the low-volume ejection waveform WS are applied to the piezoelectric element PZq, ink is ejected from the nozzle Nz corresponding to the applied piezoelectric element PZq. On the other hand, when the recovery waveform WK and the micro-vibration waveform WB are applied to the piezoelectric element PZq, ink is not ejected from the nozzle Nz corresponding to the applied piezoelectric element PZq. The high-volume ejection waveform WL and the low-volume ejection waveform WS are so-called pull-push-pull waveforms. The recovery waveform WK and the micro-vibration waveform WB are so-called pull-push waveforms.

[0086] In this embodiment, the manufacturer of the inkjet printer 1 determines the high-volume ejection waveform WL and the low-volume ejection waveform WS such that the potential difference ΔVhL between the highest potential VHL and the lowest potential VLL of the high-volume ejection waveform WL is greater than the potential difference ΔVhS between the highest potential VHS and the lowest potential VLS of the low-volume ejection waveform WS. Hereinafter, the manufacturer of the inkjet printer 1 may be referred to as the printer manufacturer. The printer manufacturer determines the recovery waveform WK and the micro-vibration waveform WB such that the potential difference ΔVhK between the reference potential V0, which is the highest potential of the recovery waveform WK, and the lowest potential VLK is greater than the potential difference ΔVhB between the reference potential V0, which is the highest potential of the micro-vibration waveform WB, and the lowest potential VLB. The potential difference ΔVhS is greater than the potential difference ΔVhK.

[0087] In this embodiment, the inkjet printer 1 forms large dots on the medium PP by applying two high-volume ejection waveforms WL to the piezoelectric element PZq during one recording period Tu. The inkjet printer 1 also forms medium dots on the medium PP by applying one high-volume ejection waveform WL and one low-volume ejection waveform WS to the piezoelectric element PZq during one recording period Tu. The inkjet printer 1 also forms small dots on the medium PP by applying one high-volume ejection waveform WL to the piezoelectric element PZq during one recording period Tu.

[0088] However, the method for forming small dots is not limited to applying a single high-volume discharge waveform WL to the piezoelectric element PZq, but may also be applied to the piezoelectric element PZq by applying a single low-volume discharge waveform WS. Furthermore, if small dots are formed by applying a single low-volume discharge waveform WS to the piezoelectric element PZq, medium dots may be formed by applying a single high-volume discharge waveform WL to the piezoelectric element PZq.

[0089] For any m from 1 to M, if the individual designation signal Sd[m] specifies an ejection operation to the piezoelectric element PZq[m] to eject an amount of ink equivalent to a large dot, the connection state designation circuit 82 sets the connection state designation signal SLa[m] to a high level during control periods Tu1 and Tu2, and sets the connection state designation signals SLb[m] and SLc[m] to a low level during the recording period Tu. In this case, a large-volume ejection waveform WL is applied to the piezoelectric element PZq[m] during control periods Tu1 and Tu2.

[0090] For any m from 1 to M, if the individual designation signal Sd[m] specifies an ejection operation to eject an amount of ink equivalent to a medium dot to the piezoelectric element PZq[m], then during the control period Tu1, the connection state designation circuit 82 sets the connection state designation signal SLa[m] to a high level and the connection state designation signals SLb[m] and SLc[m] to low levels. Next, during the control period Tu2, the connection state designation circuit 82 sets the connection state designation signal SLb[m] to a high level and the connection state designation signals SLa[m] and SLc[m] to low levels. In this case, the piezoelectric element PZq is subjected to a high-volume ejection waveform WL during the control period Tu1 and a low-volume ejection waveform WS during the control period Tu2.

[0091] For any m from 1 to M, if the individual designation signal Sd[m] specifies an ejection operation to the piezoelectric element PZq[m] to eject an amount of ink equivalent to a small dot, then during the control period Tu1, the connection state designation circuit 82 sets the connection state designation signal SLc[m] to a high level and the connection state designation signals SLa[m] and SLb[m] to low levels. Next, during the control period Tu2, the connection state designation circuit 82 sets the connection state designation signal SLb[m] to a high level and the connection state designation signals SLa[m] and SLc[m] to low levels. In this case, the piezoelectric element PZq is subjected to a micro-vibration waveform WB during the control period Tu1 and a small-volume ejection waveform WS during the control period Tu2.

[0092] For any m from 1 to M, if the individual designation signal Sd[m] specifies micro-vibration operation for the piezoelectric element PZq[m], then during control periods Tu1 and Tu2, the connection state designation circuit 82 sets the connection state designation signal SLc[m] to a high level and the connection state designation signals SLa[m] and SLb[m] to low levels. In this case, the micro-vibration waveform WB is applied to the piezoelectric element PZq[m] during control periods Tu1 and Tu2.

[0093] For any m from 1 to M, if the individual designation signal Sd[m] specifies a recovery operation for the piezoelectric element PZq[m], during the control period Tu1, the connection state designation circuit 82 sets the connection state designation signal SLb[m] to a high level and the connection state designation signals SLa[m] and SLc[m] to low levels. Next, during the control period Tu2, the connection state designation circuit 82 sets the connection state designation signal SLc[m] to a high level and the connection state designation signals SLa[m] and SLc[m] to low levels. In this case, the piezoelectric element PZq is subjected to a recovery waveform WK during the control period Tu1 and a micro-vibration waveform WB during the control period Tu2.

[0094] In the first embodiment, the small discharge waveform WS supplied to the piezoelectric element PZq via the internal wiring LHb, which corresponds to the "first wiring," corresponds to the "discharge waveform."

[0095] In Figure 8, the lowest potential VLK of the recovery waveform WK is higher than, but may be lower than, the lowest potential VLS of the small-volume discharge waveform WS. Furthermore, the recovery waveform WK may be a pull-push-pull waveform. Also, although one recovery waveform WK was provided during the control period Tu1, multiple recovery waveforms WK may be provided.

[0096] Figure 9 is an explanatory diagram illustrating the generation of connection status designation signals SLa[m], SLb[m], and SLc[m] for any m from 1 to M. The connection status designation circuit 82 decodes the individual designation signal Sd[m] according to Figure 9 and generates the connection status designation signals SLa[m], SLb[m], and SLc[m].

[0097] As shown in Figure 9, the individual designation signal Sd[m] according to this embodiment indicates one of the following values: a value that specifies an ejection operation to eject an amount of ink corresponding to a large dot (1,1,0), a value that specifies an ejection operation to eject an amount of ink corresponding to a medium dot (1,0,0), a value that specifies an ejection operation to eject an amount of ink corresponding to a small dot (0,1,0), a value that specifies a micro-vibration operation (0,0,0), or a value that specifies a recovery operation (1,1,1).

[0098] The connection status designation circuit 82 sets the connection status designation signal SLa[m] to a high level during control periods Tu1 and Tu2 if the individual designation signal Sd[m] indicates (1,1,0), and sets each signal to a low level if none of the above conditions are met.

[0099] Furthermore, the connection status designation circuit 82 sets the connection status designation signal SLa[m] to a high level during control period Tu1 and the connection status designation signal SLb[m] to a high level during control period Tu2 if the individual designation signal Sd[m] indicates (1,0,0), and sets each signal to a low level if none of the above conditions are met.

[0100] Furthermore, the connection status designation circuit 82 sets the connection status designation signal SLc[m] to a high level during control period Tu1 if the individual designation signal Sd[m] indicates (0,1,0), and sets the connection status designation signal SLa[m] to a high level during control period Tu2. If none of the above conditions are met, each signal is set to a low level.

[0101] Furthermore, the connection status specification circuit 82 sets the connection status specification signal SLc[m] to a high level during control periods Tu1 and Tu2 if the individual specification signal Sd[m] indicates (0,0,0), and sets each signal to a low level if none of the above conditions are met.

[0102] Furthermore, the connection state designation circuit 82 sets the connection state designation signal SLb[m] to a high level during control period Tu1 and during control period Tu2 if the individual designation signal Sd[m] indicates (1,1,1), and sets the connection state designation signal SLc[m] to a high level if none of the above conditions are met. If none of the above conditions are met, the signals are set to a low level. Figures 10 and 11 illustrate the change in the state near nozzle Nz by performing the recovery operation.

[0103] Figure 10 shows the state near nozzle Nz before the recovery operation is performed. Figure 11 shows the state near nozzle Nz after the recovery operation is performed. In the nozzle Nz shown in Figure 10, a bubble BL is formed. From the state shown in Figure 10, the drive circuit 81 performs a recovery operation, causing the bubble BL to flow into the nozzle channel RN, which is part of the individual channel RJ, as shown in Figure 11. Therefore, the bubble BL is no longer present in nozzle Nz, and the state of nozzle Nz is restored. Thus, it can be said that the recovery waveform WK drives the piezoelectric element PZq to the extent that it restores the state of nozzle Nz by causing the bubble BL formed in nozzle Nz to flow to the individual channel RJ.

[0104] 1-6. Operation of the control unit 6 Figure 12 is a flowchart showing the operation of the control unit 6. In step S2, the control unit 6 receives print data Img from the host computer. Next, in step S4, the control unit 6 assigns 1 to the variable i. Then, in step S6, the control unit 6 determines whether or not the image formation on the PP medium is complete. If the determination result in step S6 is positive, the control unit 6 terminates the series of processes shown in Figure 12.

[0105] If the determination result in step S6 is negative, the control unit 6 determines in step S8 whether the liquid discharge head HU is in a position facing the medium PP during the recording period Tu[i]. The liquid discharge head HU being in a position facing the medium PP means that, in a plan view, the medium PP and the liquid discharge head HU overlap. In this embodiment, the liquid discharge head HU is described as being in a position facing the medium PP if, in a plan view, a part of the medium PP and the liquid discharge head HU overlap.

[0106] As a specific process in step S8, the control unit 6 determines the position of the liquid discharge head HU relative to the medium PP in a plan view, based on a signal corresponding to the transport position of the medium PP obtained from the encoder of the transport mechanism 7 and a signal corresponding to the position of the liquid discharge head HU obtained from the encoder of the moving mechanism 8. Next, the control unit 6 determines whether the medium PP and the liquid discharge head HU overlap in a plan view, based on the position of the liquid discharge head HU relative to the medium PP in a plan view and the medium information obtained from the host computer. If it is determined that the medium PP and the liquid discharge head HU overlap in a plan view, the control unit 6 determines that the liquid discharge head HU is in a position facing the medium PP. On the other hand, if it is determined that the medium PP and the liquid discharge head HU do not overlap in a plan view, the control unit 6 determines that the liquid discharge head HU is in a position not facing the medium PP.

[0107] If the determination result in step S8 is positive, in step S10, the control unit 6 generates individual designation signals Sd for all piezoelectric elements PZq of the liquid ejection head HU based on the print data Img. Specifically, the control unit 6 generates individual designation signals Sd for all piezoelectric elements PZq of the liquid ejection head HU, specifying one of the following operations: ejection operation to eject an amount of ink equivalent to a large dot, ejection operation to eject an amount of ink equivalent to a medium dot, ejection operation to eject an amount of ink equivalent to a small dot, and micro-vibration operation.

[0108] If the result of the determination in step S8 is negative, in step S12, the control unit 6 generates an individual designation signal Sd for all piezoelectric elements PZq of the liquid discharge head HU that indicate a recovery operation.

[0109] After the processing in step S10 or step S12 is completed, in step S14, the control unit 6 transmits the individual designation signal Sd generated by the processing in step S10 or step S12 to the liquid discharge head HU before the recording period Tu[i] begins. Then, in step S16, the control unit 6 increments the value of variable i by 1. After the processing in step S16 is completed, the control unit 6 returns to the processing in step S6.

[0110] An example of executing the flowchart shown in Figure 12 will be explained using Figure 13.

[0111] Figure 13 is a diagram illustrating an example of the flowchart shown in Figure 12. As shown in Figure 2, the inkjet printer 1 transports the media PP in the Y1 direction, but in Figure 13, for ease of understanding, it is shown as if the liquid ejection head HU moves in the Y2 direction relative to the media PP.

[0112] The path RT1 shown in Figure 13 represents the path along which the liquid discharge head HU moves. The position of the liquid discharge head HU from time t1 to time t8 is shown along path RT1. In Figure 13, for ease of understanding, the position of the liquid discharge head HU at time tx is shown as liquid discharge head HU_tx for integers x from 1 to 8. The medium PP shown in Figure 13 represents the area Pic of the image formed on the medium PP.

[0113] As can be seen from Figure 13, the liquid discharge head HU is not in a position facing the medium PP at times t1, t4, t5, and t8. Therefore, at times t1, t4, t5, and t8, the control unit 6 determines that the determination result of step S8 is negative and generates an individual designation signal Sd in step S12 to indicate a recovery operation.

[0114] On the other hand, at times t2, t3, t6, and t7, the liquid discharge head HU is in a position facing the medium PP. Therefore, at times t2, t3, t6, and t7, the control unit 6 determines that the result of step S8 is positive, and in step S10 generates an individual designation signal Sd based on the print data Img. Specifically, at times t2, t3, and t7, the control unit 6 generates an individual designation signal Sd that specifies either a discharge operation or a micro-vibration operation, and at time t6, the control unit 6 generates an individual designation signal Sd that specifies a micro-vibration operation.

[0115] 1-7. Summary of the First Embodiment For the sake of simplicity, the following summary of the first embodiment will focus on one of the six head chips HC in the liquid discharge head HU, and further, refer to one of the 2 × M piezoelectric elements PZq[m] in that single head chip HC as "one piezoelectric element".

[0116] The inkjet printer 1 in the first embodiment has a liquid ejection head HU having a head chip HC which includes 2 × M piezoelectric elements PZq, 2 × M pressure chambers CBq that apply pressure to the ink inside by driving each of the 2 × M piezoelectric elements PZq, M nozzles Nz that can eject ink by the pressure applied by each of the 2 × M pressure chambers CBq, a drive circuit 81 that drives each of the 2 × M piezoelectric elements PZq, internal wiring LHb which can be switched on or off by the control of the drive circuit 81 to be electrically connected to each of the 2 × M piezoelectric elements PZq, and internal wiring LHc which can be electrically connected to each of the 2 × M piezoelectric elements PZq separately from the internal wiring LHb by the control of the drive circuit 81. The drive circuit 81 applies a small-volume ejection waveform WS to the piezoelectric element PZq[m] via internal wiring LHb to drive the piezoelectric element PZq[m] among the 2 × M piezoelectric elements PZq to the extent that ink is ejected; a micro-vibration waveform WB to the piezoelectric element PZq[m] via internal wiring LHc to drive the piezoelectric element PZq[m] to the extent that ink is not ejected; and a recovery waveform WK to the piezoelectric element PZq[m] via internal wiring LHb to drive the piezoelectric element PZq[m] to the extent that the state of the nozzle Nz[m] corresponding to the piezoelectric element PZq[m] is restored. According to the first embodiment, by applying the recovery waveform WK to the piezoelectric element PZq[m] via the internal wiring LHb, the state of the nozzle Nz[m] can be restored by the recovery waveform WK while avoiding the occurrence of short circuits and other problems that would occur if the recovery waveform WK were applied via the internal wiring LHc. Since the discharge failure is resolved by restoring the state of the nozzle Nz[m], the deterioration of the image quality formed on the medium PP can be suppressed.

[0117] Furthermore, the recovery waveform WK drives the piezoelectric element PZq[m] to the extent that ink is not ejected. The recovery waveform WK may be a waveform that drives the piezoelectric element PZq[m] to the extent that ink is ejected, but this would result in unnecessary ink consumption. Therefore, according to the first embodiment, ink consumption can be reduced compared to the mode in which ink is ejected by driving the piezoelectric element PZq[m] with the recovery waveform WK.

[0118] Furthermore, the intensity of the recovery waveform WK is higher than that of the micro-vibration waveform WB. According to the first embodiment, even if bubbles in the nozzle Nz cannot be removed by the micro-vibration waveform WB, the bubbles in the nozzle Nz can be removed by the recovery waveform WK, which has a higher intensity than the micro-vibration waveform WB.

[0119] Furthermore, the intensity of the recovery waveform WK is lower than that of the small-volume discharge waveform WS. The intensity of the recovery waveform WK may be higher than the intensity of the small-volume ejection waveform WS. However, since the small-volume ejection waveform WS ejects ink from the nozzle Nz when applied to the piezoelectric element PZq, there is a high probability that ink will also be ejected from the nozzle Nz even if the recovery waveform WK has a higher intensity than the small-volume ejection waveform WS. Therefore, according to the first embodiment, ink consumption can be reduced compared to the embodiment in which the intensity of the recovery waveform WK is higher than the intensity of the small-volume ejection waveform WS.

[0120] One head tip HC of the liquid ejection head HU further includes M individual channels RJ, a common supply channel Rsup that communicates in common with the M individual channels RJ and supplies ink to each of the multiple individual channels RJ, and a common discharge channel Rdch that communicates in common with the M individual channels RJ and discharges ink from each of the M individual channels RJ. Each of the M individual channels RJ has one or more pressure chambers CBq out of 2 × M pressure chambers CBq and communicates with one nozzle Nz out of M nozzles Nz. According to the first embodiment, the method of applying the recovery waveform WK to the piezoelectric element PZq can also be applied to a method of circulating ink from the communication channel RX1 through the individual channel RJ to the communication channel RX2.

[0121] Furthermore, the recovery waveform WK drives the piezoelectric element PZq[m] to the extent that it restores the state of the nozzle Nz[m] by causing the bubbles generated in the nozzle Nz[m] corresponding to the piezoelectric element PZq[m] to flow to the individual channel RJ[m] which has a pressure chamber CBq[m] corresponding to the piezoelectric element PZq[m]. In a configuration in which ink is circulated from the connecting channel RX1 through the individual channel RJ to the connecting channel RX2, bubbles are allowed to flow from inside the nozzle Nz into the individual channel RJ, and the bubbles flowing into the individual channel RJ can be discharged to the outside of the liquid ejection head HU by the flow of ink generated in the individual channel RJ.

[0122] Furthermore, the liquid ejection head HU ejects ink onto the medium PP. When the liquid ejection head HU is facing the medium PP, the drive circuit 81 performs an operation selected by the control unit 6 from between an ejection operation that applies a small ejection waveform WS via the internal wiring LHb and a micro-vibration operation that applies a micro-vibration waveform WB via the internal wiring LHc. When the liquid ejection head HU is not facing the medium PP, the drive circuit 81 performs a recovery operation that applies a recovery waveform WK via the internal wiring LHc. When the liquid ejection head HU is in a position that does not face the medium PP, ink will not be ejected from any of the nozzles Nz of the liquid ejection head HU. Therefore, according to the first embodiment, the recovery waveform WK is applied to the piezoelectric element PZq at a timing that does not affect the image quality, so the state of the nozzles Nz can be restored while maintaining the image quality formed on the medium PP.

[0123] Furthermore, it is preferable that the electrical withstand capability of the internal wiring LHc is lower than that of the internal wiring LHb. According to the first embodiment, compared to an embodiment in which the electrical withstand performance of the internal wiring LHc is higher than that of the internal wiring LHb, the cost of the internal wiring LHc and the size of the substrate on which the internal wiring LHc is placed can be reduced.

[0124] Furthermore, the following embodiments can also be defined from the first embodiment. The inkjet printer 1 has a liquid ejection head HU having a head chip HC which includes 2 × M piezoelectric elements PZq, 2 × M pressure chambers CBq that apply pressure to the ink inside by driving the 2 × M piezoelectric elements PZq, M nozzles Nz that can eject ink by the pressure applied by each of the 2 × M pressure chambers CBq, a drive circuit 81 that drives each of the 2 × M piezoelectric elements PZq, internal wiring LHb which can be switched on or off whether or not to be electrically connected to each of the 2 × M piezoelectric elements PZq by the control of the drive circuit 81, and internal wiring LHc which can be switched on or off whether or not to be electrically connected to each of the 2 × M piezoelectric elements PZq separately from the internal wiring LHb by the control of the drive circuit 81. The drive circuit 81 applies a small-volume ejection waveform WS to the piezoelectric element PZq[m] via internal wiring LHb to drive the piezoelectric element PZq[m] to the extent that ink is ejected from 2 × M piezoelectric elements PZq, a micro-vibration waveform WB to the piezoelectric element PZq[m] via internal wiring LHc to drive the piezoelectric element PZq[m] to the extent that ink is not ejected, and a recovery waveform WK having an intensity higher than the micro-vibration waveform WB and lower than the intensity of the small-volume ejection waveform WS to the piezoelectric element PZq[m] via internal wiring LHb. According to this embodiment, a recovery waveform WK having an intensity higher than that of the micro-vibration waveform WB and lower than that of the small-volume discharge waveform WS is applied to the piezoelectric element PZq[m] via the internal wiring LHb. This allows the state of the nozzle Nz[m] to be restored by the recovery waveform WK while avoiding the occurrence of a short circuit that would occur if the recovery waveform WK were applied via the internal wiring LHc.

[0125] Furthermore, the following embodiments can also be defined from the first embodiment. The inkjet printer 1 has a liquid ejection head HU having a head chip HC which includes 2 × M piezoelectric elements PZq, 2 × M pressure chambers CBq that apply pressure to the ink inside by driving each of the 2 × M piezoelectric elements PZq, M nozzles Nz that can eject ink by the pressure applied by each of the 2 × M pressure chambers CBq, M individual flow paths RJ, a common supply flow path Rsup that communicates in common with the M individual flow paths RJ and supplies ink to the multiple individual flow paths RJ, a common discharge flow path Rdch that communicates in common with the M individual flow paths RJ and discharges ink from the M individual flow paths RJ, and a drive circuit 81 that drives each of the 2 × M piezoelectric elements PZq. Each of the M individual flow paths RJ is provided with one or more pressure chambers CBq of the 2 × M pressure chambers CBq and communicates with one of the M nozzles Nz. The drive circuit 81 applies the following waveforms to the piezoelectric element PZq[m]: a small-volume ejection waveform WS that drives the piezoelectric element PZq[m] among 2 × M piezoelectric elements PZq to the extent that ink is ejected; a micro-vibration waveform WB that drives the piezoelectric element PZq[m] to the extent that no ink is ejected; and a recovery waveform WK that drives the piezoelectric element PZq[m] to the extent that the state of the nozzle Nz[m] corresponding to the piezoelectric element PZq[m] is restored, wherein the recovery waveform WK drives the piezoelectric element PZq[m] to the extent that the state of the nozzle Nz[m] is restored by causing the bubbles generated in the nozzle Nz[m] to flow to the individual flow path RJ[m] provided with a pressure chamber CBq[m]. According to this embodiment, by applying the recovery waveform WK to the piezoelectric element PZq[m] via the internal wiring LHb, the occurrence of a short circuit that would occur if the recovery waveform WK were applied via the internal wiring LHc is avoided, and the state of the nozzle Nz[m] can be restored by causing the bubbles in the nozzle Nz[m] to flow into the individual channel RJ[m] using the recovery waveform WK.

[0126] 2. Second Embodiment In the first embodiment, depending on whether the liquid discharge head HU is facing the medium PP, a recovery waveform WK is applied to the piezoelectric element PZq, or either the discharge waveform or the micro-vibration waveform WB is applied to the piezoelectric element PZq. On the other hand, in the second embodiment, depending on whether a recording operation is performed during the recording period Tu[i], a recovery waveform WK is applied to the piezoelectric element PZq, or either the discharge waveform or the micro-vibration waveform WB is applied to the piezoelectric element PZq. The second embodiment will be described below.

[0127] 2-1. Operation of the second embodiment Figure 14 is a flowchart showing the operation of the control unit 6 in the second embodiment. The flowchart shown in Figure 14 differs from the flowchart shown in Figure 12 in that step S8A is executed instead of step S8. Below, only the differences from the flowchart shown in Figure 12 will be explained.

[0128] If the result of the determination in step S6 is affirmative, in step S8A, the control unit 6 determines whether or not to perform a recording operation during the recording period Tu[i]. Specifically, based on the print data Img, the control unit 6 determines whether or not there is one or more piezoelectric elements PZq among all the piezoelectric elements PZq of the liquid ejection head HU that will perform an ejection operation during the recording period Tu[i]. If the result of the determination in step S8A is affirmative, the control unit 6 executes the process in step S10, and if the result of the determination in step S8A is negative, it executes the process in step S12.

[0129] Using Figure 13, an example of the execution of the flowchart shown in Figure 12 will be explained. At times t1, t4, t5, t6, and t8, the liquid discharge head HU does not overlap with the range Pic in a plan view, i.e., it does not perform a recording operation. Therefore, at times t1, t4, t5, t6, and t8, the control unit 6 in the second embodiment determines that the determination result of step S8A is negative, and in step S12 generates an individual designation signal Sd indicating a recovery operation. On the other hand, in a plan view, at times t2, t3, and t7, the liquid discharge head HU overlaps with the range Pic, i.e., it performs a recording operation. Therefore, at times t2, t3, and t7, the control unit 6 in the second embodiment determines that the determination result of step S8A is positive, and in step S10 generates an individual designation signal Sd based on the print data Img.

[0130] 2-2. Summary of the Second Embodiment In the second embodiment, the liquid ejection head HU performs a recording operation in which ink is ejected onto the medium PP from one or more nozzles Nz out of the M nozzles Nz. When the recording operation is being performed, the drive circuit 81 performs an operation selected by the control unit 6 from among an ejection operation that applies an ejection waveform via internal wiring LHb and an operation that applies a micro-vibration waveform WB via internal wiring LHc. When the recording operation is not being performed, the drive circuit 81 performs an operation that applies a recovery waveform WK via internal wiring LHb. If the recording operation is not performed, ink will not be ejected from any of the nozzles Nz of the liquid ejection head HU. Therefore, according to the second embodiment, as with the first embodiment, the recovery waveform WK is applied to the piezoelectric element PZq at a timing that does not affect the image quality, so that the state of the nozzles Nz can be restored while maintaining the image quality formed on the medium PP. As can be understood from the explanation of Figure 13, it is preferable for the liquid ejection head HU to perform a recovery operation at time t6. Therefore, the second embodiment has more opportunities to perform a recovery operation compared to the first embodiment, and thus increases the opportunities to restore the state of the nozzles Nz. On the other hand, in the second embodiment, in step S8A, it is necessary to determine whether there is one or more piezoelectric elements PZq that perform an ejection operation for all of the piezoelectric elements PZq of the liquid ejection head HU, so the more piezoelectric elements PZq the liquid ejection head HU has, the longer the execution period of step S8A becomes. On the other hand, the processing in step S8 in the first embodiment is fixed regardless of the number of piezoelectric elements PZq in the liquid discharge head HU, and the execution period of step S8 tends to be shorter than the execution period of step S8A. Therefore, the first embodiment can shorten the period required for the operation of the control unit 6 compared to the second embodiment.

[0131] It is also possible to apply the second embodiment to the first embodiment. For example, if the determination result of step S8 is affirmative, the control unit 6 may execute the process of step S8A.

[0132] 3. Third Embodiment In the third embodiment, the control unit 6 switches the waveform supplied to the ejection drive signal Com_A2 depending on whether or not a recording operation should be performed. The third embodiment will be described below.

[0133] Figure 15 is a timing chart illustrating the operation of the inkjet printer 1 during the recording period Tu[i] when a recording operation should be performed. A recording operation should be performed when the determination result of step S8 in the first embodiment is positive, or when the determination result of step S8A in the second embodiment is positive. Figure 15 illustrates the ejection drive signal ComB_A1, the ejection drive signal ComB_A2, and the micro-vibration drive signal BSDB_1 when a recording operation should be performed.

[0134] As shown in Figure 15, the discharge drive signal ComB_A1 has one large discharge waveform WL for one recording period Tu. The discharge drive signal ComB_A2 has one small discharge waveform WS for one recording period Tu. The micro-vibration drive signal BSDB_1 has one micro-vibration waveform WB for one recording period Tu.

[0135] Figure 16 is a timing chart illustrating the operation of the inkjet printer 1 during the recording period Tu[i] when the recording operation should not be performed. The case in which the recording operation should not be performed is when the determination result of step S8 in the first embodiment is negative, or when the determination result of step S8A in the second embodiment is negative. Figure 15 illustrates the ejection drive signal ComC_A2 when the recording operation should not be performed.

[0136] As shown in Figure 16, the ejection drive signal ComC_A2 has one recovery waveform WK for one recording period Tu. The ejection drive signal Com_A1, when recording should not be performed, may be the same as or different from the ejection drive signal ComB_A1. Similarly, the micro-vibration drive signal BSD_1, when recording should not be performed, may be the same as or different from the micro-vibration drive signal BSDB_1.

[0137] Figure 17 is a flowchart showing the operation of the control unit 6 in the third embodiment. The flowchart in Figure 17 differs from the flowchart in Figure 12 in that it executes the process in step S22 if the determination result in step S8 is positive, and executes the process in step S24 if the determination result in step S8 is negative. Below, only the differences from the flowchart in Figure 12 will be explained.

[0138] If the determination result in step S8 is affirmative, the control unit 6 in the third embodiment transmits a waveform specification signal dCom to the drive signal generation circuit 2 in step S22, indicating that a recording operation should be performed. Specifically, the control unit 6 in the third embodiment outputs a waveform specification signal dCom_A1 defining the discharge drive signal ComB_A1 to the discharge drive signal generation circuit 21_A1, a waveform specification signal dCom_A2 defining the discharge drive signal ComB_A2 to the discharge drive signal generation circuit 21_A2, and a waveform specification signal dCom_D1 defining the micro-vibration drive signal BSDB_1 to the micro-vibration drive signal generation circuit 22_1. After the processing in step S22 is completed, the control unit 6 in the third embodiment executes the processing in step S10.

[0139] If the determination result in step S8 is affirmative, in step S24, the control unit 6 in the third embodiment transmits a waveform specification signal dCom, which indicates that the recording operation should not be performed, to the drive signal generation circuit 2. Specifically, the control unit 6 in the third embodiment outputs a waveform specification signal dCom_A2, which defines the discharge drive signal ComC_A2, to the discharge drive signal generation circuit 21_A2. After the processing in step S24 is completed, the control unit 6 in the third embodiment executes the processing in step S12.

[0140] 4. Variations Each of the embodiments exemplified above can be modified in various ways. Specific examples of modifications that can be applied to each of the embodiments described above are given below. Two or more embodiments arbitrarily selected from the following examples can be merged as appropriate, provided they do not contradict each other.

[0141] 4-1. First variation In each of the embodiments described above, the recovery waveform WK drives the piezoelectric element PZq[m] to the extent that ink is not ejected, but is not limited to this. For example, the recovery waveform WK may be a waveform that drives the piezoelectric element PZq[m] to the extent that ink is ejected.

[0142] 4-2. Second variation In each of the embodiments described above, the intensity of the recovery waveform WK is lower than the intensity of the small-volume discharge waveform WS, but this is not limited to this. For example, the intensity of the recovery waveform WK may be higher than the intensity of the small-volume discharge waveform WS.

[0143] 4-3. Third Variation In each of the embodiments described above, the drive circuit 81 applies the recovery waveform WK to the piezoelectric element PZq via the internal wiring LHb, but is not limited to this. For example, the drive circuit 81 may apply the recovery waveform WK to the piezoelectric element PZq via the internal wiring LHa.

[0144] 4-4. Fourth variation In the embodiments described above, a serial-type inkjet printer 1 is exemplified in which the liquid ejection head HU is reciprocated in a direction along the X axis, but the present disclosure is not limited to such embodiments. The inkjet printer 1 may also be a line-type liquid ejection device in which a plurality of nozzles Nz are distributed over the entire width of the medium PP.

[0145] 4-5. Other variations The inkjet printer 1 described above can be used in various devices such as facsimile machines and photocopiers, in addition to devices dedicated to printing. However, the use of the recording device of this disclosure is not limited to printing. For example, a recording device that ejects a colorant solution can be used as a manufacturing device for forming color filters for liquid crystal displays. Also, a recording device that ejects a conductive material solution can be used as a manufacturing device for forming wiring and electrodes for wiring boards. [Explanation of Symbols]

[0146] 1...Inkjet printer, 2...Drive signal generation circuit, 5...Storage unit, 6...Control unit, 7...Transport mechanism, 8...Movement mechanism, 8a...Storage case, 8b...Endless belt, 14...Liquid container, 15...Circulation mechanism, 20...Communication plate, 21_A1,21_A2,21_B1,21_B2,21_C1,21_C2...Discharge drive signal generation circuit, 22_1,22_2...Micro-vibration drive signal generation circuit, 30...Pressure chamber substrate, 40...Diaphragm, 50...Storage chamber forming substrate, 50K...Opening, 51...Inlet, 52...Outlet, 60...Nozzle substrate, 61,62...Compliance sheet, 80...Wiring board, 81... Drive circuit, 82...Connection status specification circuit, 93...Liquid container, 810...Wiring, BL...Air bubble, BSDB_1, BSD_1, BSD_2...Micro-vibration drive signal, CB1, CB2...Pressure chamber, CH...Change signal, CL...Clock signal, ComB_A1, ComB_A2, ComC_A2, Com_A1, Com_A2, Com_B1, Com_B2, Com_C1, Com_C2...Discharge drive signal, HC_A1, HC_A2, HC_B1, HC_B2, HC_C1, HC_C2...Head chip, HU...Liquid discharge head, Img...Print data, LA1, LA2...Nozzle row, LA T...Latch signal, LB1,LB2,LC1,LC2...Nozzle row, LHa,LHb,LHc,LHd...Internal wiring, Ln...Nozzle row, Nz...Nozzle, PP...Medium, PZ1,PZ2,PZq...Piezoelectric element, Pic...Range, PlsC,PlsL...Pulse, RA1...Supply channel, RA2...Discharge channel, RB1...Supply channel, RB2...Discharge channel, RJ...Individual channel, RK1,RK2...Communicating channel, RN...Nozzle channel, RR1,RR2,RRq...Communicating channel, RT1...Path, RX1,RX2...Communicating channel, Rdch...Common discharge channel, Rsup...Common supply channel, SI...Print signal, SI...Specify Signal, SLa, SLb, SLc…Connection status specification signal, SWa, SWb, SWc…Switch, Sd…Individual specification signal, Tu…Unit period, Tu…Recording period, Tu1, Tu2…Control period, V0, VBS…Reference potential, VHL, VHS…Highest potential, VLB, VLK, VLL, VLS…Lowest potential, Vbs…Reference potential, Vin…Supply drive signal, WB…Micro-vibration waveform, WK…Recovery waveform, WL…High-volume discharge waveform, WS…Low-volume discharge waveform, ZDq…Lower electrode, ZMq…Piezoelectric, ZUq, Zu…Upper electrode, dCom, dCom_A1, dCom_A2, dCom_B1, dCom_B2,dCom_C1, dCom_C2, dCom_D1, dCom_D2… waveforms specifying signals, ΔVh, ΔVhB, ΔVhK, ΔVhL, ΔVhS… potential differences.

Claims

1. Multiple piezoelectric elements, Multiple pressure chambers that apply pressure to the liquid inside by driving each of the multiple piezoelectric elements, Multiple nozzles capable of discharging liquid by the pressure applied by each of the multiple pressure chambers, A drive circuit for driving each of the plurality of piezoelectric elements, A first wiring, which is controlled by the drive circuit to switch whether or not it is electrically connected to each of the plurality of piezoelectric elements, A second wiring, which is controlled by the drive circuit, is configured to be electrically connected to each of the plurality of piezoelectric elements, or not, separately from the first wiring. A liquid dispensing device using a liquid dispensing head having, The liquid dispensing device is characterized in that the drive circuit applies a discharge waveform to one of the plurality of piezoelectric elements via the first wiring to drive the piezoelectric element to the extent that liquid is discharged, a micro-vibration waveform to the piezoelectric element via the second wiring to drive the piezoelectric element to the extent that no liquid is discharged, and a recovery waveform to the piezoelectric element via the first wiring to drive the piezoelectric element to the extent that the state of the nozzle corresponding to the piezoelectric element is restored.

2. The liquid dispensing device according to claim 1, characterized in that the recovery waveform drives the first piezoelectric element to such an extent that no liquid is dispensed.

3. The liquid dispensing device according to claim 1, characterized in that the intensity of the recovery waveform is higher than the intensity of the micro-vibration waveform.

4. The liquid dispensing device according to claim 1, characterized in that the intensity of the recovery waveform is lower than the intensity of the discharge waveform.

5. The aforementioned liquid dispensing head is Multiple individual channels, A common supply channel that communicates with the plurality of individual channels and supplies liquid to each of the plurality of individual channels, The system further includes a common discharge channel that is in common with the aforementioned plurality of individual channels and discharges liquid from each of the plurality of individual channels, Each of the plurality of individual flow paths has one or more pressure chambers from the plurality of pressure chambers and communicates with one of the plurality of nozzles. The liquid dispensing device according to feature 1.

6. The liquid dispensing device according to claim 5, characterized in that the recovery waveform drives the first piezoelectric element to such an extent that it restores the state of the nozzle corresponding to the first piezoelectric element by causing bubbles generated in the nozzle corresponding to the first piezoelectric element to flow to an individual channel having a pressure chamber corresponding to the first piezoelectric element.

7. The liquid dispensing head dispenses liquid into the medium. The aforementioned drive circuit is When the liquid discharge head is in a position facing the medium, the selected operation is performed from the operation of applying the discharge waveform via the first wiring and the operation of applying the micro-vibration waveform via the second wiring. The liquid dispensing device according to claim 1, characterized in that when the liquid dispensing head is in a position not facing the medium, the operation of applying the recovery waveform via the first wiring is performed.

8. The liquid discharge head performs a recording operation in which liquid is discharged into the medium from one or more of the plurality of nozzles. The aforementioned drive circuit is When the recording operation is being performed, the selected operation is performed from the operation of applying the discharge waveform via the first wiring and the operation of applying the micro-vibration waveform via the second wiring. The liquid dispensing device according to claim 1, characterized in that, if the recording operation is not performed, an operation to apply the recovery waveform via the first wiring is performed.

9. The liquid dispensing device according to claim 1, characterized in that the electrical withstand performance of the second wiring is lower than that of the first wiring.

10. Multiple piezoelectric elements, Multiple pressure chambers that apply pressure to the liquid inside by driving the multiple piezoelectric elements, Multiple nozzles capable of discharging liquid by the pressure applied by each of the multiple pressure chambers, A drive circuit for driving each of the plurality of piezoelectric elements, A first wiring, which is controlled by the drive circuit to switch whether or not it is electrically connected to each of the plurality of piezoelectric elements, A second wiring, which is controlled by the drive circuit, is configured to be electrically connected to each of the plurality of piezoelectric elements, or not, separately from the first wiring. A liquid dispensing device using a liquid dispensing head having, The liquid dispensing device is characterized in that the drive circuit applies a discharge waveform to one of the plurality of piezoelectric elements via the first wiring to drive the piezoelectric element to the extent that liquid is discharged, applies a micro-vibration waveform to the piezoelectric element via the second wiring to drive the piezoelectric element to the extent that liquid is not discharged, and applies a recovery waveform to the piezoelectric element via the first wiring that has an intensity higher than the intensity of the micro-vibration waveform and lower than the intensity of the discharge waveform.

11. Multiple piezoelectric elements, Multiple pressure chambers that apply pressure to the liquid inside by driving each of the multiple piezoelectric elements, Multiple nozzles capable of discharging liquid by the pressure applied by each of the multiple pressure chambers, Multiple individual channels, A common supply channel that is in common with the plurality of individual channels and supplies liquid to the plurality of individual channels, A common discharge channel that is in common with the plurality of individual channels and discharges liquid from the plurality of individual channels, A drive circuit for driving each of the plurality of piezoelectric elements, A liquid dispensing device using a liquid dispensing head having, Each of the aforementioned plurality of individual flow paths has one or more pressure chambers of the plurality of pressure chambers and communicates with one of the plurality of nozzles. The liquid dispensing device is characterized in that the drive circuit applies to the one piezoelectric element a discharge waveform that drives one of the plurality of piezoelectric elements to the extent that liquid is discharged, a micro-vibration waveform that drives the one piezoelectric element to the extent that liquid is not discharged, and a recovery waveform that drives the one piezoelectric element to the extent that restores the state of the nozzle corresponding to the one piezoelectric element, wherein the recovery waveform drives the one piezoelectric element to the extent that it restores the state of the nozzle corresponding to the one piezoelectric element by causing bubbles generated in the nozzle corresponding to the one piezoelectric element to flow to an individual flow path having a pressure chamber corresponding to the one piezoelectric element.

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