Liquid ejection device and control method for liquid ejection device

Abstract

To recover an ejecting state to a normal state by appropriately adjusting the circulation of ink according to the type of an anomaly in the ejecting state.SOLUTION: A liquid ejection device 100 includes: a piezoelectric element PZ; a plurality of individual flow passages RK each of which includes a pressure chamber CV and a nozzle N; a common flow passage R1 that supplies ink to the plurality of individual flow passages RK; a common flow passage R2 that ejects ink from the plurality of individual flow passages RK; a determination unit 3 that determines an ejecting state of the nozzle N, based on residual vibration generated in the pressure chamber CV after a voltage is applied to the piezoelectric element PZ; a circulating mechanism 6 that circulates ink from the common flow passage R1 to the common flow passage R2 via the plurality of individual flow passages RK; and a recovery control unit 40 that executes a recovery process for recovering the ejecting state of the nozzle N to a normal state by controlling the circulating mechanism 6 in a case where there is an anomaly in the ejecting state of the nozzle. As the recovery process, the recovery control unit 40 executes a different process according to a type of the anomaly determined by the determination unit 3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a method for controlling the liquid ejection device.

Background Art

[0002] A liquid ejection device such as an inkjet printer fills a liquid such as ink into a liquid ejection head and then ejects the liquid from the liquid ejection head. In such a liquid ejection head, in order to prevent the retention of air bubbles in the liquid and the thickening of the liquid, a technique of circulating the liquid in a flow path provided in the liquid ejection head has been proposed. For example, Patent Document 1 discloses a liquid ejection device having a circulation mechanism that circulates ink discharged from a liquid ejection head back to the liquid ejection head.

[0003] Further, in a liquid ejection head that ejects a liquid from a nozzle using a piezoelectric element, a technique has been proposed for determining the ejection state of the nozzle based on residual vibration generated in a pressure chamber communicating with the nozzle after applying a voltage to the piezoelectric element. For example, Patent Document 2 discloses a droplet ejection device having a head unit including a plurality of droplet ejection heads each having a diaphragm, an actuator, and a cavity, and head abnormality detection means for detecting residual vibration of the diaphragm and detecting a head abnormality of the droplet ejection head based on the vibration pattern of the residual vibration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in a liquid ejection apparatus that circulates liquid in a flow path provided in a liquid ejection head, it has been considered that even when the ejection state of the nozzles becomes abnormal, the ejection state will return to a normal state due to the circulation of the liquid. However, according to the study by the inventor of the present application, it has been found that it is necessary to adjust the circulation of the liquid depending on the type of abnormality in the ejection state of the nozzles.

Means for Solving the Problems

[0006] In order to solve the above problems, a liquid ejection apparatus according to the present invention includes a piezoelectric element, a plurality of individual flow paths each including a pressure chamber and a nozzle for ejecting liquid, a common supply flow path that communicates with the plurality of individual flow paths in common and supplies liquid to the plurality of individual flow paths, a common discharge flow path that communicates with the plurality of individual flow paths in common and discharges liquid from the plurality of individual flow paths, a state determination unit that determines the ejection state of the nozzles based on residual vibration generated in the pressure chamber after applying a voltage to the piezoelectric element, a circulation unit that circulates liquid from the common supply flow path to the common discharge flow path via the plurality of individual flow paths, and a recovery control unit that executes a recovery process for returning the ejection state of the nozzles to a normal state by controlling the circulation unit when there is an abnormality in the ejection state of the nozzles. The recovery control unit executes different processes according to the type of the abnormality determined by the state determination unit as the recovery process.

[0007] In addition, a control method for a liquid ejection device according to the present invention includes a piezoelectric element, a plurality of individual flow paths each including a pressure chamber and a nozzle for ejecting liquid, a common supply flow path that communicates with the plurality of individual flow paths in common and supplies liquid to the plurality of individual flow paths, a common discharge flow path that communicates with the plurality of individual flow paths in common and discharges liquid from the plurality of individual flow paths, a state determination unit that determines the ejection state of the nozzle based on residual vibration generated in the pressure chamber after applying a voltage to the piezoelectric element, and a circulation unit that circulates liquid from the common supply flow path through the plurality of individual flow paths to the common discharge flow path. The control method for the liquid ejection device is characterized in that when there is an abnormality in the ejection state of the nozzle, a recovery process is executed to recover the ejection state of the nozzle to a normal state by controlling the circulation unit, and the recovery process is different depending on the type of the abnormality determined by the state determination unit.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, in each figure, the dimensions and scales of each part are appropriately different from the actual ones. Also, the embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are imposed. However, the scope of the present invention is not limited to these embodiments unless otherwise specifically stated in the following description to limit the present invention.

[0010] [1. Embodiment] First, with reference to FIG. 1, an overview of the liquid ejection device 100 according to the present embodiment will be described. In the present embodiment, it is assumed as an example that the liquid ejection device 100 is an inkjet printer that ejects ink onto a medium PP to form an image. In the present embodiment, as the medium PP, the recording paper shown in FIG. 2 described later is assumed.

[0011] FIG. 1 is a block diagram showing an example of the configuration of the liquid ejection device 100 according to the embodiment of the present invention.

[0012] The liquid ejection device 100 is supplied with print data IMG indicating an image to be formed by the liquid ejection device 100 from a host computer such as a personal computer or a digital camera. The liquid ejection device 100 executes a printing process for forming the image indicated by the print data IMG supplied from the host computer on the medium PP.

[0013] The liquid ejection device 100 includes a liquid ejection head 1 provided with a discharge part D that ejects ink, a drive signal generation unit 2 that generates a plurality of drive signals COM for driving the discharge part D, and a determination unit 3 that determines the discharge state of the nozzle N. Note that the nozzle N will be described later with reference to FIGS. 3 and 4. Further, the liquid ejection device 100 includes a control unit 4 that controls each part of the liquid ejection device 100, and a storage unit 5 that stores print data IMG and various information such as a control program of the liquid ejection device 100. Furthermore, the liquid ejection device 100 includes a circulation mechanism 6 that circulates ink, a maintenance unit 7 that executes maintenance processing of the liquid ejection head 1, a medium conveyance mechanism 8 that conveys a medium PP, and a carriage conveyance mechanism 9 that reciprocates a carriage 91. Note that the carriage 91 will be described later with reference to FIG. 2. The determination unit 3 is an example of a "state determination part", and the circulation mechanism 6 is an example of a "circulation mechanism part".

[0014] In the present embodiment, it is assumed that the liquid ejection head 1 and the drive signal generation unit 2 correspond to each other, the liquid ejection head 1 and the determination unit 3 correspond to each other, and the liquid ejection head 1 and the circulation mechanism 6 correspond to each other. For example, the liquid ejection device 100 may include a plurality of liquid ejection heads 1, a plurality of drive signal generation units 2, a plurality of determination units 3, and a plurality of circulation mechanisms 6. In this case, for example, the plurality of drive signal generation units 2 correspond to the plurality of liquid ejection heads 1 on a one-to-one basis, the plurality of determination units 3 correspond to the plurality of liquid ejection heads 1 on a one-to-one basis, and the plurality of circulation mechanisms 6 correspond to the plurality of liquid ejection heads 1 on a one-to-one basis. Alternatively, the liquid ejection device 100 may include one liquid ejection head 1, one drive signal generation unit 2 corresponding to the liquid ejection head 1, one determination unit 3 corresponding to the liquid ejection head 1, and one circulation mechanism 6 corresponding to the liquid ejection head 1.

[0015] In this embodiment, it is assumed that the liquid ejection device 100 has four liquid ejection heads 1 corresponding to four types of inks: cyan, magenta, yellow, and black. That is, in this embodiment, it is assumed that the liquid ejection device 100 has four liquid ejection heads 1, four drive signal generation units 2, four determination units 3, and four circulation mechanisms 6. However, hereinafter, for convenience of explanation, as illustrated in FIG. 1, attention may be paid to one of the four liquid ejection heads 1, and one drive signal generation unit 2, one determination unit 3, and one circulation mechanism 6 corresponding to the one liquid ejection head 1, and an explanation may be given.

[0016] First, before explaining the liquid ejection head 1, the control unit 4, the drive signal generation unit 2, and the storage unit 5 will be explained.

[0017] The control unit 4 is configured to include one or more CPUs (Central Processing Unit). Note that the control unit 4 may be configured to include a programmable logic device such as an FPGA (field-programmable gate array) instead of or in addition to the CPU. Further, for example, the control unit 4 operates according to a control program stored in the storage unit 5 to generate signals for controlling the operations of each part of the liquid ejection device 100, such as a print signal SI and a waveform specification signal dCOM.

[0018] Here, the waveform specification signal dCOM is a digital signal that defines the waveform of each of the plurality of drive signals COM. Each drive signal COM is an analog signal for driving the ejection unit D. In this embodiment, as shown in FIG. 6 and the like described later, it is assumed that the plurality of drive signals COM include a drive signal COMa, a drive signal COMb, and a drive signal COMc. The print signal SI is a digital signal for specifying the type of operation of the ejection unit D. Specifically, the print signal SI is a signal for specifying the type of operation of the ejection unit D by specifying whether to supply each drive signal COM to the ejection unit D.

[0019] Also, in the present embodiment, the control unit 4 functions as a recovery control unit 40 by operating according to a control program stored in the storage unit 5. When there is an abnormality in the discharge state of the nozzle N shown in, for example, FIG. 3 described later, the recovery control unit 40 executes a recovery process of controlling the circulation mechanism 6 to recover the discharge state of the nozzle N to a normal state. In the present embodiment, the recovery control unit 40 executes different processes according to the type of abnormality in the discharge state determined by the determination unit 3 as the recovery process. The details of the recovery process will be described in FIGS. 9, 10, and 11.

[0020] The drive signal generation unit 2 includes, for example, a DAC (Digital Analog Converter), and generates a plurality of drive signals COM based on a waveform designation signal dCOM supplied from the control unit 4. For example, each of the plurality of drive signals COM generated by the drive signal generation unit 2 includes a waveform defined by the waveform designation signal dCOM. The drive signal generation unit 2 outputs the plurality of drive signals COM generated based on the waveform designation signal dCOM to a switching circuit 18 included in the liquid discharge head 1.

[0021] The storage unit 5 is configured to include one or both of a volatile memory such as a RAM (Random Access Memory) and a non-volatile memory such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a PROM (Programmable ROM). Note that the storage unit 5 may be included in the control unit 4.

[0022] The liquid discharge head 1 includes a switching circuit 18, a recording head 10, and a detection circuit 19.

[0023] The recording head 10 has M ejection units D. Note that the value M is a natural number of 1 or more. Hereinafter, among the M ejection units D provided in the recording head 10, the m-th ejection unit D may be referred to as ejection unit D[m]. Here, the variable m is a natural number satisfying "1 ≦ m ≦ M". Further, hereinafter, when a component or signal etc. of the liquid ejection apparatus 100 corresponds to the ejection unit D[m] among the M ejection units D, a subscript [m] may be attached to the symbol for representing the component or signal etc.

[0024] The switching circuit 18 switches whether to supply each drive signal COM to the ejection unit D[m] based on the print signal SI. Hereinafter, as shown in FIG. 6 etc. to be described later, among the plurality of drive signals COM, the drive signal COM supplied to the ejection unit D[m] may be referred to as the individual drive signal Vin[m]. Further, the switching circuit 18 switches whether to electrically connect the ejection unit D[m] and the detection circuit 19 based on the print signal SI. When the ejection unit D[m] and the detection circuit 19 are electrically connected, for example, the detection signal Vout[m] detected from the ejection unit D[m] is supplied to the detection circuit 19 via the switching circuit 18.

[0025] The detection circuit 19 generates the residual vibration signal Vd[m] based on the detection signal Vout[m]. For example, the detection circuit 19 shapes the detection signal Vout[m] into a waveform suitable for processing in the determination unit 3 by amplifying the amplitude of the detection signal Vout[m] or removing noise components included in the detection signal Vout[m]. Thereby, the residual vibration signal Vd[m] is generated. For example, the detection circuit 19 may include a negative feedback type amplifier for amplifying the detection signal Vout[m], a low-pass filter for attenuating the high-frequency components of the detection signal Vout[m], and a voltage follower for converting the impedance and outputting the low-impedance residual vibration signal Vd[m].

[0026] The detection circuit 19 outputs the residual vibration signal Vd[m] generated based on the detection signal Vout[m] to the determination unit 3.

[0027] The determination unit 3 determines, for example, the ejection state of the nozzle N included in the ejection unit D[m] based on the residual vibration signal Vd[m]. For example, the residual vibration signal Vd[m] used for determining the ejection state of the nozzle N included in the ejection unit D[m] represents the waveform of the residual vibration that remains in the ejection unit D[m] after the ejection unit D[m] is driven by the individual drive signal Vin[m].

[0028] For example, the determination unit 3 determines the ejection state of the nozzle N by comparing the detected values such as the amplitude and period of the residual vibration signal Vd[m] with the reference values when the ejection state of the nozzle N is normal. Then, the determination unit 3 generates, for example, determination result information Rinf including information indicating the ejection state of the nozzle N, and outputs the generated determination result information Rinf to the control unit 4. Examples of the ejection state of the nozzle N include states such as normal, a first abnormality caused by air bubbles entering the nozzle N, a second abnormality caused by thickening of the ink in the nozzle N, and a third abnormality caused by ink leakage from the nozzle N. The above-described recovery control unit 40 executes, for example, a recovery process for recovering the ejection state of the nozzle N to a normal state based on the type of abnormality indicated by the determination result information Rinf when the determination result information Rinf indicates any of the first abnormality, the second abnormality, and the third abnormality. Note that the determination unit 3 may be included in the control unit 4. For example, the control unit 4 may function as the determination unit 3 by operating according to a control program stored in the storage unit 5.

[0029] Also, in the present embodiment, as described above, the maintenance unit 7 executes the maintenance process. For example, the maintenance unit 7 executes the maintenance process under the control of the control unit 4. The maintenance process includes, for example, a flushing process for discharging ink from the ejection unit D, a wiping process for wiping foreign matter such as ink adhering to the vicinity of the nozzle N of the ejection unit D with a wiper, and a pumping process for sucking the ink in the ejection unit D by a tube pump or the like.

[0030] The maintenance unit 7 includes a discharged ink receiving portion for receiving the discharged ink when the ink in the discharge portion D is discharged in the flushing process, a wiper for wiping foreign matters such as ink attached near the nozzle N of the discharge portion D, and a tube pump for sucking the ink, air bubbles, etc. in the discharge portion D. Note that the discharged ink receiving portion, the wiper, and the tube pump are not shown in the figure.

[0031] Next, while referring to FIG. 2, a schematic overall configuration of the liquid discharge device 100 will be described.

[0032] FIG. 2 is a configuration diagram schematically showing the liquid discharge device 100. In FIG. 2, the description will be centered on the circulation mechanism 6, the medium conveyance mechanism 8, and the carriage conveyance mechanism 9.

[0033] Based on the control signal Ctr supplied from the control unit 4, the circulation mechanism 6 supplies the ink stored in the circulation mechanism 6 to the liquid discharge head 1. Further, based on the control signal Ctr supplied from the control unit 4, the circulation mechanism 6 recovers the ink from the liquid discharge head 1 and returns the recovered ink to the liquid discharge head 1.

[0034] For example, the circulation mechanism 6 includes an ink container 60 for storing ink, a pump 63 connected to a supply flow path 61 for supplying ink to the liquid discharge head 1, and a pump 64 connected to a recovery flow path 62 for recovering the ink discharged from the liquid discharge head 1. As the ink container 60, for example, a cartridge detachable from the liquid discharge device 100, a bag-shaped ink pack formed of a flexible film, or an ink tank capable of replenishing ink can be adopted. Note that the type of ink stored in the ink container 60 is not particularly limited and is arbitrary.

[0035] Pumps 63 and 64 are controlled by the control unit 4. For example, pump 63 supplies the ink stored in the ink container 60 to the liquid ejection head 1 via the supply channel 61 based on the control signal Ctr supplied from the control unit 4. Also, for example, pump 64 collects the ink from the liquid ejection head 1 via the recovery channel 62 based on the control signal Ctr supplied from the control unit 4, and supplies the collected ink to the ink container 60.

[0036] Note that the circulation mechanism 6 may be defined without including the ink container 60, or may be defined including the supply channel 61 and the recovery channel 62.

[0037] The medium conveyance mechanism 8 conveys the medium PP in the Y1 direction along the Y axis under the control of the control unit 4. Hereinafter, the Y1 direction and the Y2 direction opposite to the Y1 direction are collectively referred to as the Y-axis direction. Also, hereinafter, the X1 direction along the X axis intersecting the Y axis and the X2 direction opposite to the X1 direction are collectively referred to as the X-axis direction. Also, hereinafter, the Z1 direction along the Z axis intersecting the X axis and the Y axis and the Z2 direction opposite to the Z1 direction are collectively referred to as the Z-axis direction. In the present embodiment, as an example, the case where the X axis, the Y axis, and the Z axis are orthogonal to each other will be assumed and described. However, the present invention is not limited to such a mode. The X axis, the Y axis, and the Z axis only need to intersect each other.

[0038] The carriage conveyance mechanism 9 reciprocates the plurality of liquid ejection heads 1 in the X1 direction and the X2 direction under the control of the control unit 4. As shown in FIG. 2, the carriage conveyance mechanism 9 has a substantially box-shaped carriage 91 that houses the plurality of liquid ejection heads 1 and an endless belt 92 to which the carriage 91 is fixed. Note that the circulation mechanism 6 may be housed in the carriage 91 together with the liquid ejection heads 1.

[0039] The liquid ejection head 1 is driven by a drive signal COM under the control of a print signal SI, and ejects ink in the Z1 direction from some or all of a plurality of nozzles N provided in the liquid ejection head 1. That is, the liquid ejection head 1 ejects ink from some or all of the plurality of nozzles N in conjunction with the conveyance of the medium PP by the medium conveyance mechanism 8 and the reciprocating movement of the liquid ejection head 1 by the carriage conveyance mechanism 9, and lands the ejected ink on the surface of the medium PP, thereby forming a desired image on the surface of the medium PP.

[0040] Next, with reference to FIGS. 3 and 4, a schematic structure of the liquid ejection head 1 will be described.

[0041] FIG. 3 is an exploded perspective view of the liquid ejection head 1. FIG. 4 is a cross-sectional view taken along line II-II shown in FIG. 3. The cross-section along line II-II is parallel to the XZ plane and passes through connection ports H1 and H2, which will be described later.

[0042] As shown in FIGS. 3 and 4, the liquid ejection head 1 includes a nozzle substrate 11, compliance sheets CS1 and CS2, a communication plate 12, a pressure chamber substrate 13, a diaphragm 14, a sealing substrate 15, a flow path forming substrate 16, and a wiring substrate 17 on which electronic components EC are mounted. The electronic components EC include, for example, electric circuits such as a switching circuit 18 and a detection circuit 19. For example, the recording head 10 is electrically connected to the switching circuit 18, the detection circuit 19, etc. via the wiring substrate 17.

[0043] As shown in FIG. 3, the recording head 10 includes, for example, a nozzle substrate 11, compliance sheets CS1 and CS2, a communication plate 12, a pressure chamber substrate 13, a diaphragm 14, a sealing substrate 15, and a flow path forming substrate 16.

[0044] The nozzle substrate 11 is a plate-shaped member that is long in the Y-axis direction and extends substantially parallel to the XY plane. Here, "substantially parallel" is a concept that includes cases where, in addition to being completely parallel, it can be regarded as parallel considering errors. In this embodiment, "substantially parallel" is a concept that includes cases where it can be regarded as parallel considering an error of about 10%. "Substantially perpendicular" described later is also a concept that includes cases where, in addition to being completely perpendicular, it can be regarded as perpendicular considering errors, similar to "substantially parallel".

[0045] M nozzles N are formed on the nozzle substrate 11. Here, the nozzle N is a through-hole provided in the nozzle substrate 11. In this embodiment, it is assumed that M nozzles N are arranged to extend in the Y-axis direction on the nozzle substrate 11. Hereinafter, the M nozzles N extending in the Y-axis direction may be referred to as a nozzle row Ln.

[0046] Note that the nozzle substrate 11 is manufactured, for example, by processing a single-crystal silicon substrate using semiconductor manufacturing techniques such as etching, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the nozzle substrate 11.

[0047] As shown in FIGS. 3 and 4, a communication plate 12 is provided at a position in the Z2 direction with respect to the nozzle substrate 11. The communication plate 12 is a plate-shaped member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The communication plate 12 is manufactured, for example, by processing a single-crystal silicon substrate using semiconductor manufacturing techniques, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the communication plate 12.

[0048] An ink flow path is formed in the communication plate 12. Specifically, one common flow path BB1 provided to extend in the Y-axis direction and one common flow path BB2 provided to extend in the Y-axis direction are formed in the communication plate 12. Note that the common flow path BB2 is located in the X2 direction with respect to the common flow path BB1. Also, one common flow path BA1 provided to extend in the Y-axis direction and one common flow path BA2 provided to extend in the Y-axis direction are formed in the communication plate 12. Note that although the common flow path BA1 and the common flow path BA2 are not shown in FIG. 3, as shown in FIG. 4, they are located between the common flow path BB1 and the common flow path BB2. The common flow path BA2 is located between the common flow path BA1 and the common flow path BB2.

[0049] Also, in the communication plate 12, M connection channels BK1 corresponding to the M nozzles N, M connection channels BK2 corresponding to the M nozzles N, M connection channels BR1 corresponding to the M nozzles N, and M connection channels BR2 corresponding to the M nozzles N are formed. Further, as shown in FIG. 4, M nozzle channels BN corresponding to the M nozzles N are formed in the communication plate 12.

[0050] As shown in FIG. 4, the connection channel BK1 is provided to extend in the Z-axis direction at a position in the X2 direction with respect to the common flow path BB1 and at a position in the Z2 direction with respect to the common flow path BA1, and communicates with the common flow path BA1. The connection channel BR1 is provided to extend in the Z-axis direction at a position in the X2 direction with respect to the connection channel BK1. Also, the connection channel BK2 is provided to extend in the Z-axis direction at a position in the X1 direction with respect to the common flow path BB2 and at a position in the Z2 direction with respect to the common flow path BA2, and communicates with the common flow path BA2. The connection channel BR2 is provided to extend in the Z-axis direction at a position in the X1 direction with respect to the connection channel BK2. Note that the connection channel BR2 is located in the X2 direction with respect to the connection channel BR1. The nozzle channel BN is located between the connection channel BR1 and the connection channel BR2 and communicates with the connection channel BR1 and the connection channel BR2. Also, the nozzle channel BN communicates with the nozzle N corresponding to the nozzle channel BN.

[0051] Hereinafter, the common flow paths BA1 and BA2 may be collectively referred to as the common flow path BA, and the common flow paths BB1 and BB2 may be collectively referred to as the common flow path BB. Also, hereinafter, the connection flow paths BK1 and BK2 may be collectively referred to as the connection flow path BK, and the connection flow paths BR1 and BR2 may be collectively referred to as the connection flow path BR.

[0052] As shown in FIGS. 3 and 4, a pressure chamber substrate 13 is provided at a position in the Z2 direction with respect to the communication plate 12. The pressure chamber substrate 13 is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The pressure chamber substrate 13 is manufactured, for example, by processing a single-crystalline silicon substrate using semiconductor manufacturing technology. However, known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the pressure chamber substrate 13.

[0053] Ink flow paths are formed in the pressure chamber substrate 13. Specifically, M pressure chambers CV1 corresponding to the M nozzles N and M pressure chambers CV2 corresponding to the M nozzles N are formed in the pressure chamber substrate 13. The pressure chamber CV1 is located in the Z2 direction with respect to the connection flow paths BK1 and BR1, and extends in the X-axis direction so as to communicate with the connection flow paths BK1 and BR1. The pressure chamber CV2 is located in the Z2 direction with respect to the connection flow paths BK2 and BR2, and extends in the X-axis direction so as to communicate with the connection flow paths BK2 and BR2. Hereinafter, the pressure chambers CV1 and CV2 may be collectively referred to as the pressure chamber CV.

[0054] Hereinafter, the connection flow path BK1, the pressure chamber CV1 communicating with the connection flow path BK1, the connection flow path BR1 communicating with the pressure chamber CV1, the nozzle flow path BN communicating with the connection flow path BR1, the connection flow path BR2 communicating with the nozzle flow path BN, the pressure chamber CV2 communicating with the connection flow path BR2, and the connection flow path BK2 communicating with the pressure chamber CV2 may be referred to as individual flow paths RK. Further, hereinafter, the individual flow path RK corresponding to the m-th nozzle N among the M nozzles N may be referred to as individual flow path RK[m]. In the present embodiment, the individual flow path RK[m] is defined to include the m-th nozzle N among the M nozzles N. That is, in the present embodiment, the individual flow path RK[m] has the m-th nozzle N and the pressure chamber CV corresponding to the m-th nozzle N. Further, in the present embodiment, the M individual flow paths RK[1] to RK[M] are arranged along the Y-axis direction.

[0055] As shown in FIGS. 3 and 4, a diaphragm 14 is provided at a position in the Z2 direction with respect to the pressure chamber substrate 13. The diaphragm 14 is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane, and is a member that can vibrate elastically. The diaphragm 14 has, for example, an elastic film made of silicon oxide and an insulator film made of zirconium oxide. Note that the elastic film included in the diaphragm 14 is not limited to an elastic film made of silicon oxide. Similarly, the insulator film included in the diaphragm 14 is not limited to an insulator film made of zirconium oxide.

[0056] As shown in FIGS. 3 and 4, on the surface of the diaphragm 14 in the Z2 direction, M piezoelectric elements PZ1 corresponding to M pressure chambers CV1 and M piezoelectric elements PZ2 corresponding to M pressure chambers CV2 are provided. Here, the surface of element A in the first direction is a surface that is substantially perpendicular to the first direction among the surfaces of element A and is the surface that can be seen when element A is viewed from the first direction to the second direction. Note that the second direction is the direction opposite to the first direction. Also, in this specification, the expression "element B is formed on the surface of element A" is not intended to be limited to a configuration in which element A and element B are in direct contact. That is, even in a configuration where element C is formed on the surface of element A and element B is formed on the surface of element C, as long as at least a part of element A and element B overlaps in a plan view, it is included in the concept of "element B is formed on the surface of element A".

[0057] Although not shown in FIGS. 3 and 4, as shown in FIG. 6, the piezoelectric element PZ1 has a common electrode Zd1 to which a predetermined bias potential VBS is supplied, an individual electrode Zu1 to which an individual drive signal Vin1 is supplied, and a piezoelectric layer Zm1 provided between the individual electrode Zu1 and the common electrode Zd1. For example, the common electrode Zd1, the piezoelectric layer Zm1, and the individual electrode Zu1 are provided along the Z2 direction on the surface of the diaphragm 14 in the Z2 direction in this order. Similarly, the piezoelectric element PZ2 has a common electrode Zd2, an individual electrode Zu2, and a piezoelectric layer Zm2. Hereinafter, the piezoelectric elements PZ1 and PZ2 may be collectively referred to as the piezoelectric element PZ. Similarly, the common electrodes Zd1 and Zd2 may be collectively referred to as the common electrode Zd, the individual electrodes Zu1 and Zu2 may be collectively referred to as the individual electrode Zu, and the piezoelectric layers Zm1 and Zm2 may be collectively referred to as the piezoelectric layer Zm. Note that in this embodiment, the common electrode Zd is a so-called lower electrode and the individual electrode Zu is a so-called upper electrode, but the common electrode Zd may be an upper electrode and the individual electrode Zu may be a lower electrode.

[0058] The piezoelectric element PZ is a passive element that deforms in response to a change in the potential of the drive signal COM supplied to the individual electrode Zu as the individual drive signal Vin. Specifically, the piezoelectric element PZ is driven and deformed in response to a change in the potential of the drive signal COM.

[0059] As shown in FIGS. 3 and 4, since the piezoelectric element PZ is provided on the surface of the diaphragm 14 in the Z2 direction, the diaphragm 14 vibrates in conjunction with the deformation of the piezoelectric element PZ. When the diaphragm 14 vibrates, the pressure in the pressure chamber CV fluctuates. Then, due to the fluctuation of the pressure in the pressure chamber CV, the ink filled inside the pressure chamber CV is discharged from the nozzle N via the connection flow path BR and the nozzle flow path BN.

[0060] As shown in FIGS. 3 and 4, at a position in the Z2 direction with respect to the pressure chamber substrate 13, a sealing substrate 15 for protecting M piezoelectric elements PZ1 and M piezoelectric elements PZ2 is provided. The sealing substrate 15 is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The sealing substrate 15 is manufactured, for example, by processing a single-crystal silicon substrate using semiconductor manufacturing technology, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the sealing substrate 15.

[0061] On the surface of the sealing substrate 15 in the Z1 direction, a recess for covering M piezoelectric elements PZ1 and a recess for covering M piezoelectric elements PZ2 are provided. Hereinafter, the sealing space formed between the diaphragm 14 and the sealing substrate 15 that covers M piezoelectric elements PZ1 is referred to as a sealing space SP1, and the sealing space formed between the diaphragm 14 and the sealing substrate 15 that covers M piezoelectric elements PZ2 is referred to as a sealing space SP2. Also, hereinafter, the sealing spaces SP1 and SP2 may be collectively referred to as a sealing space SP. The sealing space SP is a space for sealing the piezoelectric element PZ to prevent the piezoelectric element PZ from deteriorating due to the influence of moisture or the like.

[0062] The sealing substrate 15 is provided with a through hole 15h. The through hole 15h is a hole that is located between the sealing space SP1 and the sealing space SP2 when the sealing substrate 15 is viewed in the Z1 direction and penetrates from the surface of the sealing substrate 15 in the Z1 direction to the surface of the sealing substrate 15 in the Z2 direction. A wiring substrate 17 is inserted into the through hole 15h.

[0063] As shown in FIGS. 3 and 4, a flow path forming substrate 16 is provided at a position in the Z2 direction with respect to the communication plate 12. The flow path forming substrate 16 is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The flow path forming substrate 16 is formed, for example, by injection molding of a resin material, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the flow path forming substrate 16.

[0064] In the flow path forming substrate 16, an ink flow path is formed. Specifically, in the flow path forming substrate 16, one common flow path BC1 provided so as to extend in the Y-axis direction and one common flow path BC2 provided so as to extend in the Y-axis direction are formed. For example, as shown in FIG. 4, the common flow path BC1 is provided at a position in the Z2 direction with respect to the common flow path BB1 and communicates with the common flow path BB1. The common flow path BC2 is provided at a position in the Z2 direction with respect to the common flow path BB2 and at a position in the X2 direction with respect to the common flow path BC1 and communicates with the common flow path BB2. Hereinafter, the common flow paths BC1 and BC2 may be collectively referred to as the common flow path BC.

[0065] Hereinafter, the common flow path BA1, the common flow path BB1 communicating with the common flow path BA1, and the common flow path BC1 communicating with the common flow path BB1 may be collectively referred to as the common flow path R1. Also, hereinafter, the common flow path BA2, the common flow path BB2 communicating with the common flow path BA2, and the common flow path BC2 communicating with the common flow path BB2 may be collectively referred to as the common flow path R2. Also, hereinafter, the common flow paths R1 and R2 may be collectively referred to as the common flow path R. Note that the common flow path R1 is an example of a "common supply flow path", and the common flow path R2 is an example of a "common discharge flow path".

[0066] The flow path forming substrate 16 is provided with a connection port H1 communicating with the common flow path BC1 and a connection port H2 communicating with the common flow path BC2. A supply flow path 61 is connected to the connection port H1, and a recovery flow path 62 is connected to the connection port H2. For example, the pump 63 supplies ink from the ink container 60 to the common flow path R1 including the common flow path BC1 through the supply flow path 61 and the connection port H1. In this case, the pressure applied to the common flow path R1 becomes a positive pressure Pin higher than the atmospheric pressure. Also, for example, the pump 64 recovers a part of the ink stored in the common flow path R2 including the common flow path BC2 through the recovery flow path 62 and the connection port H2, and supplies the recovered ink to the ink container 60. In this case, the pressure applied to the common flow path R2 becomes a negative pressure Pout lower than the atmospheric pressure. Thus, for example, the pump 63 functions as a pressurizing mechanism for pressurizing the pressure applied to the common flow path R1, and the pump 64 functions as a decompressing mechanism for decompressing the pressure applied to the common flow path R2.

[0067] Hereinafter, an increase in the positive pressure Pin means, for example, an increase in the pressure for directing the ink stored in the common flow path R1 toward the nozzle N. Also, an increase in the negative pressure Pout means an increase in the pressure for discharging the ink stored in the common flow path R2 from the connection port H2, that is, an increase in the amount of pressure reduction applied to the common flow path R2. Hereinafter, unless otherwise specified, an increase in the negative pressure Pout means an increase in the absolute value of the negative pressure Pout, and a decrease in the negative pressure Pout means a decrease in the absolute value of the negative pressure Pout.

[0068] Here, for example, when the negative pressure Pout is smaller than an appropriate pressure with respect to the positive pressure Pin, there is a risk that ink may leak from the nozzle N, and when the negative pressure Pout is larger than an appropriate pressure with respect to the positive pressure Pin, there is a risk that ink may not be properly discharged from the nozzle N. Therefore, the positive pressure Pin and the negative pressure Pout are adjusted so that the ink discharge state becomes a normal state.

[0069] Also, a part of the ink supplied to the common flow path R1 is filled into the pressure chamber CV1 via the connection flow path BK1. When the piezoelectric element PZ1 is driven by the drive signal COM, a part of the ink filled in the pressure chamber CV1 is discharged from the nozzle N via the connection flow path BR1. Also, a part of the ink supplied to the pressure chamber CV1 is filled into the pressure chamber CV2 via the connection flow path BR1, the nozzle flow path BN, and the connection flow path BR2. When the piezoelectric element PZ2 is driven by the drive signal COM, a part of the ink filled in the pressure chamber CV2 is discharged from the nozzle N via the connection flow path BR2. As shown in FIG. 4, in the present embodiment, one discharge unit D includes two piezoelectric elements PZ, two pressure chambers CV, and one nozzle N.

[0070] As shown in FIGS. 3 and 4, the flow path forming substrate 16 is provided with a through hole 16h. The through hole 16h is located between the common flow path BC1 and the common flow path BC2 when the flow path forming substrate 16 is viewed in the Z1 direction, and is a hole that penetrates from the surface of the flow path forming substrate 16 in the Z1 direction to the surface of the flow path forming substrate 16 in the Z2 direction. A wiring substrate 17 is inserted into the through hole 16h.

[0071] As shown in FIGS. 3 and 4, the wiring substrate 17 is mounted on the surface of the diaphragm 14 in the Z2 direction. The wiring substrate 17 is a component for electrically connecting the liquid discharge head 1 to the control unit 4. As the wiring substrate 17, for example, a flexible wiring substrate such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably adopted. As described above, electronic components EC including the switching circuit 18 and the detection circuit 19 are mounted on the wiring substrate 17.

[0072] As shown in FIGS. 3 and 4, at a position in the X1 direction with respect to the nozzle substrate 11 at a position in the Z1 direction with respect to the communication plate 12, a compliance sheet CS1 is provided so as to block the common flow path BA1 and the common flow path BB1. Further, at a position in the X2 direction with respect to the nozzle substrate 11 at a position in the Z1 direction with respect to the communication plate 12, a compliance sheet CS2 is provided so as to block the common flow path BA2 and the common flow path BB2. Hereinafter, the compliance sheets CS1 and CS2 may be collectively referred to as the compliance sheet CS. The compliance sheet CS is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The compliance sheet CS is formed of an elastic material and absorbs pressure fluctuations of the ink in the common flow path BA and the connection flow path BK.

[0073] Although not shown, the liquid ejection head 1 has a cap for sealing the nozzle surface NP which is the surface in the Z1 direction of the nozzle substrate 11. The cap seals the nozzle surface NP of the nozzle substrate 11 on which the nozzles N are formed during a period when ink is not ejected from the nozzles N.

[0074] Next, with reference to FIG. 5, the flow of ink will be described.

[0075] FIG. 5 is an explanatory diagram for explaining the flow of ink. Note that FIG. 5 shows the flow of ink in the common flow path R and the individual flow paths RK when the liquid ejection head 1 is viewed in a plan view in the Z1 direction. However, in FIG. 5, for convenience of illustration, the connection flow path BK is described as extending in the X-axis direction, but in the liquid ejection head 1, the connection flow path BK extends in the Z-axis direction. Further, in FIG. 5, for convenience of illustration, the supply flow path 61 and the recovery flow path 62 are described as extending in the X-axis direction, but the supply flow path 61 and the recovery flow path 62 do not necessarily extend in the X-axis direction. Further, in FIG. 5, as an example, a case where the value M is "8" is assumed. Further, in FIG. 5, it is assumed that each of the connection port H1 and the connection port H2 is located between the individual flow path RK[4] and the individual flow path RK[5] in the Y-axis direction.

[0076] When circulating the ink, the supply channel 61 supplies the ink to the common channel R1, and the recovery channel 62 recovers the ink from the common channel R2. For example, in the common channel R1, as shown by the arrows AR11 and AR12, the ink flows from the connection port H1 in the Y1 direction and the Y2 direction. The ink flowing from the connection port H1 in the Y1 direction is supplied to the individual channels RK[5] to RK[8], and the ink flowing from the connection port H1 in the Y2 direction is supplied to the individual channels RK[1] to RK[4].

[0077] Also, in the individual channel RK[m], as shown by the arrow FA[m], the ink flows from the common channel R1 to the common channel R2 in the X2 direction. As a result, for example, the pressure chambers CV1 and CV2 provided in the individual channel RK[m] are filled with ink.

[0078] Also, for example, in the common channel R2, as shown by the arrows AR21 and AR22, the ink flows from the individual channels RK[5] to RK[8] in the Y2 direction, and the ink flows from the individual channels RK[1] to RK[4] in the Y1 direction. That is, the ink discharged from the individual channels RK[1] to RK[4] flows in the Y2 direction and is recovered by the recovery channel 62 via the connection port H2. Also, the ink discharged from the individual channels RK[5] to RK[8] flows in the Y1 direction and is recovered by the recovery channel 62 via the connection port H2.

[0079] In this way, the common channel R1 communicates with a plurality of individual channels RK in common and supplies ink to the plurality of individual channels RK. Also, the common channel R2 communicates with a plurality of individual channels RK in common and discharges ink from the plurality of individual channels RK. In this embodiment, it is assumed that ink circulation as shown in FIG. 5 occurs in the recovery process of restoring the discharge state of the nozzle N to a normal state and the printing process of forming an image indicated by the print data IMG on the medium.

[0080] Next, the outline of the liquid ejection head 1 will be described with reference to FIG. 6.

[0081] FIG. 6 is a block diagram showing an example of the configuration of the liquid ejection head 1. In FIG. 6, for ease of viewing, one ejection unit D[m] out of the M ejection units D is shown.

[0082] As described with reference to FIG. 1, the liquid ejection head 1 includes a recording head 10, a switching circuit 18, and a detection circuit 19. The liquid ejection head 1 also has a wiring La to which a drive signal COMa is supplied from the drive signal generation unit 2, a wiring Lb to which a drive signal COMb is supplied from the drive signal generation unit 2, and a wiring Lc to which a drive signal COMc is supplied from the drive signal generation unit 2. Further, the liquid ejection head 1 has a wiring Ls for supplying a detection signal Vout to the detection circuit 19, wirings Li1[m] and Li2[m] for supplying individual drive signals Vin1[m] and Vin2[m] to the ejection unit D[m], respectively, and a wiring Ld to which a bias potential VBS is supplied. Note that the detection signal Vout is a general term for detection signals Vout1 and Vout2. Also, hereinafter, the individual drive signals Vin1 and Vin2 may be collectively referred to as the individual drive signal Vin, and the wirings Li1 and Li2 may be collectively referred to as the wiring Li.

[0083] The switching circuit 18 includes M switches SWa1 corresponding one-to-one to the M ejection units D, M switches SWb1 corresponding one-to-one to the M ejection units D, M switches SWc1 corresponding one-to-one to the M ejection units D, and M switches SWs1 corresponding one-to-one to the M ejection units D. Further, the switching circuit 18 includes M switches SWa2 corresponding one-to-one to the M ejection units D, M switches SWb2 corresponding one-to-one to the M ejection units D, M switches SWc2 corresponding one-to-one to the M ejection units D, and M switches SWs2 corresponding one-to-one to the M ejection units D. Hereinafter, the switches SWa1 and SWa2 may be collectively referred to as the switch SWa, the switches SWb1 and SWb2 may be collectively referred to as the switch SWb, the switches SWc1 and SWc2 may be collectively referred to as the switch SWc, and the switches SWs1 and SWs2 may be collectively referred to as the switch SWa.

[0084] Further, the switching circuit 18 has a connection state specifying circuit CSC. The connection state specifying circuit CSC specifies the connection state of each of M switches SWa1, M switches SWb1, M switches SWc1, M switches SWs1, M switches SWa2, M switches SWb2, M switches SWc2, and M switches SWs2. For example, the connection state specifying circuit CSC generates connection state specifying signals Qa1[m], Qb1[m], Qc1[m], Qs1[m], Qa2[m], Qb2[m], Qc2[m], and Qs2[m] based on at least some of the signals of the print signal SI, latch signal LAT, change signal CH, and period defining signal Tsig supplied from the control unit 4.

[0085] For example, the connection state specifying signal Qa1[m] is a signal for specifying the on / off state of the switch SWa1[m], and the connection state specifying signal Qb1[m] is a signal for specifying the on / off state of the switch SWb1[m]. The connection state specifying signal Qc1[m] is a signal for specifying the on / off state of the switch SWc1[m], and the connection state specifying signal Qs1[m] is a signal for specifying the on / off state of the switch SWs1[m]. The connection state specifying signal Qa2[m] is a signal for specifying the on / off state of the switch SWa2[m], and the connection state specifying signal Qb2[m] is a signal for specifying the on / off state of the switch SWb2[m]. Further, the connection state specifying signal Qc2[m] is a signal for specifying the on / off state of the switch SWc2[m], and the connection state specifying signal Qs2[m] is a signal for specifying the on / off state of the switch SWs2[m].

[0086] The switch SWa1[m] switches between conduction and non - conduction of the wiring La and the individual electrode Zu1[m] of the piezoelectric element PZ1[m] provided in the ejection part D[m] based on the connection state designation signal Qa1[m]. That is, the switch SWa1[m] switches between conduction and non - conduction of the wiring La and the wiring Li1[m] connected to the individual electrode Zu1[m] based on the connection state designation signal Qa1[m]. In the present embodiment, the switch SWa1[m] turns on when the connection state designation signal Qa1[m] is at a high level and turns off when it is at a low level. When the switch SWa1[m] is on, the drive signal COMa supplied to the wiring La is supplied as the individual drive signal Vin1[m] to the individual electrode Zu1[m] of the ejection part D[m] via the wiring Li1[m].

[0087] The switch SWb1[m] switches between conduction and non - conduction of the wiring Lb and the individual electrode Zu1[m] of the piezoelectric element PZ1[m] provided in the ejection part D[m] based on the connection state designation signal Qb1[m]. That is, the switch SWb1[m] switches between conduction and non - conduction of the wiring Lb and the wiring Li1[m] connected to the individual electrode Zu1[m] based on the connection state designation signal Qb1[m]. In the present embodiment, the switch SWb1[m] turns on when the connection state designation signal Qb1[m] is at a high level and turns off when it is at a low level. When the switch SWb1[m] is on, the drive signal COMb supplied to the wiring Lb is supplied as the individual drive signal Vin1[m] to the individual electrode Zu1[m] of the ejection part D[m] via the wiring Li1[m].

[0088] Switch SWc1[m] switches between conduction and non - conduction of wiring Lc and the individual electrode Zu1[m] of the piezoelectric element PZ1[m] provided in the ejection part D[m] based on the connection state designation signal Qc1[m]. That is, switch SWc1[m] switches between conduction and non - conduction of wiring Lc and the wiring Li1[m] connected to the individual electrode Zu1[m] based on the connection state designation signal Qc1[m]. In the present embodiment, switch SWc1[m] turns on when the connection state designation signal Qc1[m] is at a high level and turns off when it is at a low level. When switch SWc1[m] is on, the drive signal COMc supplied to the wiring Lc is supplied as the individual drive signal Vin1[m] to the individual electrode Zu1[m] of the ejection part D[m] via the wiring Li1[m].

[0089] Switch SWs1[m] switches between conduction and non - conduction of wiring Ls and the individual electrode Zu1[m] of the piezoelectric element PZ1[m] provided in the ejection part D[m] based on the connection state designation signal Qs1[m]. That is, switch SWs1[m] switches between conduction and non - conduction of wiring Ls and the wiring Li1[m] connected to the individual electrode Zu1[m] based on the connection state designation signal Qs1[m]. In the present embodiment, switch SWs1[m] turns on when the connection state designation signal Qs1[m] is at a high level and turns off when it is at a low level.

[0090] For example, the connection state designation signal Qs1[m] becomes at a high level when detecting the residual vibration of the pressure chamber CV1[m] of the ejection part D[m]. Hereinafter, the pressure chamber CV in which the residual vibration is detected may be referred to as the pressure chamber CV to be detected. When switch SWs1[m] is on, the detection signal Vout1[m] indicating the potential of the individual electrode Zu1[m] of the piezoelectric element PZ1[m] corresponding to the pressure chamber CV1[m] to be detected is supplied to the detection circuit 19 via the wiring Li1[m] and the wiring Ls. The detection circuit 19 generates a residual vibration signal Vd[m] based on the detection signal Vout[m]. Hereinafter, the ejection part D including the pressure chamber CV to be detected may be referred to as the ejection part D to be detected.

[0091] As described above, the individual drive signal Vin[m] is a signal that is supplied to the piezoelectric element PZ[m] of the discharge unit D[m] via the switch SWa[m], SWb[m], or SWc among the drive signals COMa, COMb, and COMc. Further, the piezoelectric element PZ2[m] is also driven in the same manner as the piezoelectric element PZ1[m].

[0092] Next, with reference to FIG. 7, the operation of the liquid discharge device 100 in the unit period Tu will be described.

[0093] FIG. 7 is a timing chart showing an example of the operation of the liquid discharge device 100 in the unit period Tu. In the present embodiment, when the liquid discharge device 100 executes printing processing, a printing processing period including one or a plurality of unit periods Tu is set as the operation period of the liquid discharge device 100. The liquid discharge device 100 according to the present embodiment can drive each discharge unit D for printing processing in each unit period Tu. Further, the liquid discharge device 100 according to the present embodiment can drive the discharge unit D to be detected and detect the detection signal Vout[m] from the discharge unit D to be detected in each unit period Tu.

[0094] The control unit 4 outputs a latch signal LAT having a pulse PlsL and a change signal CH having a pulse PlsC. Thereby, the control unit 4 defines the unit period Tu as the period from the rising edge of the pulse PlsL to the rising edge of the next pulse PlsL. Further, the control unit 4 divides the unit period Tu into two control periods Tu1 and Tu2 by the pulse PlsC.

[0095] The print signal SI includes, for example, M individual designation signals Sd[1] to Sd[M] that correspond one-to-one to the M discharge units D[1] to D[M]. The individual designation signal Sd[m] designates the driving mode of the discharge unit D[m] in each unit period Tu when the liquid discharge device 100 executes printing processing.

[0096] Prior to each unit period Tu during which printing processing is executed, the control unit 4 supplies a print signal SI including individual designation signals Sd[1] to Sd[M] to the connection state designation circuit CSC in synchronization with a clock signal CL. Then, in the unit period Tu, the connection state designation circuit CSC generates connection state designation signals Qa1[m], Qb1[m], Qs1[m], Qa2[m], Qb2[m], and Qs2[m] based on the individual designation signal Sd[m].

[0097] Note that in this embodiment, it is assumed that the ejection unit D[m] can form any one of a large dot, a medium dot smaller than the large dot, and a small dot smaller than the medium dot in the unit period Tu. Hereinafter, the amount of ink corresponding to a large dot may be referred to as a large amount of ink, the amount of ink corresponding to a medium dot may be referred to as a medium amount of ink, and the amount of ink corresponding to a small dot may be referred to as a small amount of ink.

[0098] For example, the individual designation signal Sd[m] is a signal that designates any one of five driving modes, namely, ejection of a large amount of ink, ejection of a medium amount of ink, ejection of a small amount of ink, non-ejection of ink, and driving as the ejection unit D to be detected, for the ejection unit D[m] in each unit period Tu.

[0099] First, the operation of the connection state designation circuit CSC and the like when a driving mode other than the ejection unit D to be detected is designated by the individual designation signal Sd[m] will be described. Note that in this embodiment, it is assumed that the piezoelectric elements PZ1[m] and PZ2[m] included in the ejection unit D[m] are driven in the same manner as each other in the ejection of a large amount of ink, the ejection of a medium amount of ink, the ejection of a small amount of ink, and the non-ejection of ink.

[0100] The drive signal generation unit 2 outputs a drive signal COMa having pulses PX and PY. Note that the waveform of the drive signal COMa in the control period Tu1 corresponds to the pulse PX, and the waveform of the drive signal COMa in the control period Tu2 corresponds to the pulse PY.

[0101] In this embodiment, the pulse PX and the pulse PY are defined such that the potential difference between the highest potential VHx and the lowest potential VLx of the pulse PX is greater than the potential difference between the highest potential VHy and the lowest potential VLy of the pulse PY. Specifically, when driving the ejection unit D[m] with the drive signal COMa having the pulse PX, the waveform of the pulse PX is defined such that a medium amount of ink is ejected from the ejection unit D[m]. Further, when driving the ejection unit D[m] with the drive signal COMa having the pulse PY, the waveform of the pulse PY is defined such that a small amount of ink is ejected from the ejection unit D[m]. Note that the potentials at the start and end of the pulse PX and the pulse PY are set to the reference potential V0.

[0102] Further, the drive signal generation unit 2 outputs a drive signal COMb having a pulse PB. The pulse PB has a fine vibration waveform such that no ink is ejected from the ejection unit D[m] when the individual drive signal Vin[m] having the pulse PB is supplied to the ejection unit D[m]. That is, the pulse PB is a fine vibration waveform for applying fine vibration to the ink inside the ejection unit D to prevent thickening of the ink. For example, in this embodiment, the pulse PB is defined such that the potential difference between the lowest potential Vb of the pulse PB and the reference potential V0 which is the highest potential is smaller than the potential difference between the highest potential VHy and the lowest potential VLy of the pulse PY of the drive signal COMa. Note that the potentials at the start and end of the pulse PB are set to the reference potential V0.

[0103] When the individual designation signal Sd[m] designates the formation of a large dot for the ejection unit D[m], the connection state designation circuit CSC sets the connection state designation signal Qa[m] to a high level during the control periods Tu1 and Tu2. Further, the connection state designation circuit CSC sets the connection state designation signals Qb[m], Qc[m], and Qs[m] to a low level during the unit period Tu. In this case, the ejection unit D[m] is driven by the pulse PX of the drive signal COMa during the control period Tu1 to eject a medium amount of ink, and is driven by the pulse PY of the drive signal COMa during the control period Tu2 to eject a small amount of ink. As a result, the ejection unit D[m] ejects a total of a large amount of ink during the unit period Tu, and a large dot is formed on the medium PP.

[0104] Also, when the individual designation signal Sd[m] designates the formation of a medium dot for the ejection unit D[m], the connection state designation circuit CSC sets the connection state designation signal Qa[m] to a high level during the control period Tu1 and to a low level during the control period Tu2, respectively. Further, the connection state designation circuit CSC sets the connection state designation signal Qb[m] to a low level during the control period Tu1 and to a high level during the control period Tu2, respectively, and sets the connection state designation signals Qc[m] and Qs[m] to a low level during the unit period Tu. The connection state designation signals Qb[m], Qc[m], and Qs[m] are set to a low level during the unit period Tu. In this case, the ejection unit D[m] is driven by the pulse PX of the drive signal COMa during the control period Tu1 to eject a medium amount of ink, and is driven so as not to eject ink by the pulse PB of the drive signal COMb during the control period Tu2. As a result, the ejection unit D[m] ejects a medium amount of ink during the unit period Tu, and a medium dot is formed on the medium PP.

[0105] Also, when the individual designation signal Sd[m] designates the formation of small dots for the ejection unit D[m], the connection state designation circuit CSC sets the connection state designation signal Qa[m] to a low level during the control period Tu1 and to a high level during the control period Tu2, respectively. Also, the connection state designation circuit CSC sets the connection state designation signal Qb[m] to a high level during the control period Tu1 and to a low level during the control period Tu2, respectively, and sets the connection state designation signals Qc[m] and Qs[m] to a low level during the unit period Tu. In this case, during the control period Tu1, the reference potential V0 is supplied to the piezoelectric element PZ[m] of the ejection unit D[m] by the drive signal COMb. Thus, during the control period Tu1, the reference potential V0 is supplied to the ejection unit D[m] by the drive signal COMb so that the shape of the piezoelectric element PZ[m] of the ejection unit D[m] does not deform. Also, during the control period Tu2, the ejection unit D[m] is driven by the pulse PY of the drive signal COMa to eject a small amount of ink. As a result, the ejection unit D[m] ejects a small amount of ink during the unit period Tu, and small dots are formed on the medium PP.

[0106] Also, when the individual designation signal Sd[m] designates non-ejection of ink for the ejection unit D[m], the connection state designation circuit CSC sets the connection state designation signal Qb[m] to a high level during the unit period Tu, and sets the connection state designation signals Qa[m], Qc[m], and Qs[m] to a low level during the unit period Tu. In this case, the ejection unit D[m] is driven so as not to eject ink by the pulse PB of the drive signal COMb during the unit period Tu. As a result, the ejection unit D[m] does not eject ink during the unit period Tu and does not form dots on the medium PP. Also, since the ejection unit D[m] is driven so as not to eject ink, thickening of the ink in the ejection unit D[m] is prevented.

[0107] Next, the operations of the connection state designation circuit CSC and the like when the driving mode of the ejection unit D as the detection target is designated by the individual designation signal Sd[m] will be described.

[0108] For example, the drive signal generation unit 2 outputs a drive signal COMc having a pulse PS. Note that the waveform of the drive signal COMc in the unit period Tu corresponds to the pulse PS. In the present embodiment, the pulse PS is defined such that the potential difference between the highest potential VHs and the lowest potential VLs of the pulse PS is smaller than the potential difference between the highest potential VHy and the lowest potential VLy of the pulse PY. Specifically, when supplying the drive signal COMc having the pulse PS to the ejection unit D[m], the waveform of the pulse PS is defined such that the ejection unit D[m] is driven to such an extent that ink is not ejected from the ejection unit D[m]. Note that the potential at the start and end of the pulse PS is set to the reference potential V0.

[0109] Further, the control unit 4 outputs a period definition signal Tsig having pulses PlsT1 and PlsT2. Thereby, the control unit 4 divides the unit period Tu into a control period TSS1 from the start of the pulse PlsL to the start of the pulse PlsT1, a control period TSS2 from the start of the pulse PlsT1 to the start of the pulse PlsT2, and a control period TSS3 from the start of the pulse PlsT2 to the start of the next pulse PlsL.

[0110] And, for example, when the individual designation signal Sd[m] designates the pressure chamber CV1[m] as the pressure chamber CV to be detected, the connection state designation circuit CSC sets the connection state designation signals Qa1[m], Qb1, Qa2[m], Qb2[m], Qc2[m], and Qs2[m] to the low level in the unit period Tu. Further, the connection state designation circuit CSC sets the connection state designation signal Qc1[m] to the high level in the control periods TSS1 and TSS3 and to the low level in the control period TSS2, respectively. Further, the connection state designation circuit CSC sets the connection state designation signal Qs1[m] to the low level in the control periods TSS1 and TSS3 and to the high level in the control period TSS2, respectively.

[0111] In this case, the piezoelectric element PZ1[m] corresponding to the pressure chamber CV1[m] to be detected is driven by the pulse PS of the drive signal COMc during the control period TSS1. Specifically, the piezoelectric element PZ1[m] is displaced by the pulse PS of the drive signal COMc during the control period TSS1. As a result, vibration occurs in the pressure chamber CV1[m] to be detected. The vibration generated during the control period TSS1 also remains during the control period TSS2. Then, during the control period TSS2, the potential of the individual electrode Zu1[m] of the piezoelectric element PZ1[m] corresponding to the pressure chamber CV1[m] to be detected changes according to the residual vibration occurring in the pressure chamber CV1[m]. That is, during the control period TSS2, the potential of the individual electrode Zu of the piezoelectric element PZ corresponding to the pressure chamber CV to be detected becomes a potential corresponding to the electromotive force of the piezoelectric element PZ caused by the residual vibration occurring in the pressure chamber CV to be detected. And the potential of the individual electrode Zu is detected as the detection signal Vout during the control period TSS2.

[0112] In addition, in the above example, it is assumed that only the piezoelectric element PZ1[m] out of the piezoelectric elements PZ1[m] and PZ2[m] of the pressure chamber CV1[m] to be detected is driven, but both the piezoelectric elements PZ1[m] and PZ2[m] may be driven. That is, both the piezoelectric elements PZ1[m] and PZ2[m] of the pressure chamber CV1[m] to be detected may be driven by the pulse PS of the drive signal COMc during the control period TSS1.

[0113] Note that the operation of the liquid ejection device 100 is not limited to the example shown in FIG. 7. For example, in FIG. 7, the case where the sizes of the dots that can be formed on the medium PP are three types, large, medium, and small, is exemplified, but the size of the dots that can be formed on the medium PP is not limited to three types. Specifically, the size of the dots that can be formed on the medium PP may be one type or two types. Also, the drive signal COMc may have a micro-vibration waveform, for example, the pulse PB, as the pulse PS to give a micro-vibration to the ink inside the ejection unit D during the control period TSS1 to prevent thickening of the ink. In this case, the drive signal generation unit 2 may not generate the drive signal COMb.

[0114] Also, in FIG. 7, the case where the detection signal Vout for detecting the presence or absence of an abnormality in the ejection state of the nozzle N included in the ejection unit D to be detected is generated during the printing process is illustrated. However, the detection signal Vout may be generated during a period different from the printing process. That is, a process for detecting the presence or absence of an abnormality in the ejection state of the nozzle N included in the ejection unit D to be detected may be executed during a period different from the printing process. Further, the pulse PB may be used when circulating the ink without ejecting it from the nozzle N. For example, when performing printing every one pass while moving the liquid ejection head 1 along the X-axis, the pressure chamber CV may be vibrated by the pulse PB between passes to circulate the ink. Also, the pressure chamber CV may be vibrated by the pulse PB to circulate the ink between a printing job based on one print data IMG and a printing job based on other print data IMG. Alternatively, the pressure chamber CV may be vibrated by the pulse PB to circulate the ink during maintenance.

[0115] Next, the operation of the determination unit 3 will be described with reference to FIG. 8.

[0116] FIG. 8 is an explanatory diagram for explaining the operation of the determination unit 3.

[0117] Generally, the residual vibration generated in the pressure chamber CV has a natural vibration frequency determined by the shape of the nozzle N, the weight of the ink filled in the pressure chamber CV, the viscosity of the ink filled in the pressure chamber CV, and the like.

[0118] Also, generally, when bubbles are mixed in the nozzle N and an abnormality occurs in the ejection state of the nozzle N, the frequency of the residual vibration becomes higher compared to the case where no bubbles are mixed in the nozzle N. Also, generally, when foreign matter such as paper dust adheres near the nozzle N of the ejection unit D and an abnormality occurs in the ejection state of the nozzle N, the frequency of the residual vibration becomes lower compared to the case where no foreign matter adheres. For example, when ink leaks from the nozzle N and an abnormality occurs in the ejection state of the nozzle N, the frequency of the residual vibration becomes lower compared to the case where no ink leaks from the nozzle N. Also, generally, when the ink in the nozzle N thickens and an abnormality occurs in the ejection state of the nozzle N, the frequency of the residual vibration becomes lower compared to the case where the ink in the nozzle N has not thickened. Also, generally, when the ink in the nozzle N thickens and an abnormality occurs in the ejection state of the nozzle N, the frequency of the residual vibration becomes lower compared to the case where foreign matter such as paper dust adheres near the nozzle N. Also, generally, when the pressure chamber CV of the ejection unit D is not filled with ink and an abnormality occurs in the ejection state of the nozzle N, or when the piezoelectric element PZ fails and cannot be displaced, resulting in an abnormality in the ejection state of the nozzle N, the amplitude of the residual vibration becomes smaller.

[0119] As described above, the residual vibration signal Vd shows a waveform corresponding to the residual vibration occurring in the pressure chamber CV to be detected. Specifically, the residual vibration signal Vd shows a frequency corresponding to the frequency of the residual vibration occurring in the pressure chamber CV to be detected, and shows an amplitude corresponding to the amplitude of the residual vibration occurring in the pressure chamber CV to be detected. Therefore, the determination unit 3 can determine the ink ejection state of the nozzle N of the ejection unit D to be detected based on the residual vibration signal Vd.

[0120] In the determination of the ejection state, the determination unit 3 measures the time length of one cycle of the residual vibration signal Vd as the period NTc of the residual vibration signal Vd. Also, in the determination of the ejection state, the determination unit 3 determines whether the residual vibration signal Vd has a predetermined amplitude. Specifically, during the period when the determination unit 3 measures the period NTc of the residual vibration signal Vd, the determination unit 3 determines whether the potential of the residual vibration signal Vd is equal to or higher than a first threshold potential that is higher than the potential at the amplitude center level of the residual vibration signal Vd and equal to or lower than a second threshold potential that is lower than the potential at the amplitude center level. When the result of this determination is affirmative, it is specified that the residual vibration signal Vd has a predetermined amplitude, and when the result of this determination is negative, it is specified that the residual vibration signal Vd does not have a predetermined amplitude. Then, the determination unit 3 generates determination result information Rinf indicating the determination result of the ejection state of the nozzle N of the ejection unit D to be detected based on the period NTc and the amplitude of the residual vibration signal Vd.

[0121] For example, when the amplitude of the residual vibration signal Vd is equal to or greater than a predetermined amplitude, the determination unit 3 determines the ejection state of the nozzle N of the ejection unit D to be detected by comparing the period NTc of the residual vibration signal Vd with some or all of the threshold values Tth1, Tth2, and Tth3.

[0122] Here, the threshold value Tth1 is a value for indicating the boundary between the time length of one cycle of the residual vibration when the ejection state of the nozzle N is normal and the time length of one cycle of the residual vibration when air bubbles are mixed into the pressure chamber CV. Also, the threshold value Tth2 is a value for indicating the boundary between the time length of one cycle of the residual vibration when the ejection state of the nozzle N is normal and the time length of one cycle of the residual vibration when foreign matter adheres near the nozzle N. Also, the threshold value Tth3 is a value for indicating the boundary between the time length of one cycle of the residual vibration when foreign matter adheres near the nozzle N and the time length of one cycle of the residual vibration when the ink in the pressure chamber CV thickens. Note that the threshold values Tth1, Tth2, and Tth3 satisfy "Tth1 < Tth2 < Tth3".

[0123] As shown in FIG. 8, in the present embodiment, when the amplitude of the residual vibration signal Vd is equal to or greater than a predetermined amplitude and the period NTc of the residual vibration signal Vd satisfies “Tth1 ≦ NTc ≦ Tth2”, the determination unit 3 determines that the ejection state of the nozzle N of the ejection unit D to be detected is normal.

[0124] When the amplitude of the residual vibration signal Vd is equal to or greater than a predetermined amplitude and the period NTc of the residual vibration signal Vd satisfies “NTc < Tth1”, the determination unit 3 determines that the ejection state of the nozzle N is a first abnormality caused by the entry of bubbles into the nozzle N. Further, when the amplitude of the residual vibration signal Vd is equal to or greater than a predetermined amplitude and the period NTc of the residual vibration signal Vd satisfies “Tth2 < NTc ≦ Tth3”, the determination unit 3 determines that the ejection state of the nozzle N is a third abnormality caused by ink leakage from the nozzle N. Further, when the amplitude of the residual vibration signal Vd is equal to or greater than a predetermined amplitude and the period NTc of the residual vibration signal Vd satisfies “Tth3 < NTc”, the determination unit 3 determines that the ejection state of the nozzle N is a second abnormality caused by thickening of the ink in the nozzle N.

[0125] When the amplitude of the residual vibration signal Vd is less than the predetermined amplitude, the determination unit 3 determines that the ejection state of the nozzle N is abnormal. In the present embodiment, when the amplitude of the residual vibration signal Vd is less than the predetermined amplitude, the ejection state of the nozzle N is treated as an abnormality other than the above-described first abnormality, second abnormality, and third abnormality.

[0126] Next, with reference to FIG. 9, a first recovery process that is executed when the ejection state of the nozzle N is a first abnormality caused by the entry of bubbles into the nozzle N among the recovery processes for restoring the ejection state of the nozzle N to a normal state will be described.

[0127] FIG. 9 is a flowchart showing an example of the first recovery process. The first recovery process is executed when the discharge state of the nozzle N is a first abnormality caused by the mixing of bubbles into the nozzle N. That is, the process in step S100 is executed when the determination unit 3 determines that the discharge state of the nozzle N is the first abnormality. Note that the first recovery process shown in FIG. 9, that is, the series of processes from step S100 to step S128, is executed by the control unit 4 that functions as the recovery control unit 40. In addition, detailed descriptions of the processes described in FIGS. 1 to 8 are omitted. As described in FIG. 5, in the present embodiment, it is assumed that ink circulation is performed in the recovery process such as the first recovery process and the printing process.

[0128] First, in step S100, the recovery control unit 40 continues the ink circulation. For example, the recovery control unit 40 continues the ink circulation by controlling the pumps 63 and 64.

[0129] Then, in step S102, after waiting for a predetermined time, the recovery control unit 40 moves the process to step S104.

[0130] In step S104, the recovery control unit 40 acquires determination result information Rinf indicating the determination result of the discharge state of the nozzle N from the determination unit 3. For example, the recovery control unit 40 controls the liquid discharge head 1 or the like to cause the determination unit 3 to re-determine the discharge state of the nozzle N. Then, the recovery control unit 40 acquires the determination result information Rinf indicating the result of the re-determination from the determination unit 3.

[0131] Next, in step S106, the recovery control unit 40 determines based on the determination result information Rinf whether or not the discharge state of the nozzle N has recovered from the first abnormality to a normal state. If the result of the determination in step S106 is affirmative, the recovery control unit 40 ends the first recovery process shown in FIG. 9. On the other hand, if the result of the determination in step S106 is negative, the recovery control unit 40 moves the process to step S108.

[0132] In step S108, the recovery control unit 40 determines whether or not a series of processes from step S100 to step S106 have been executed a predetermined number of times. If the result of the determination in step S108 is affirmative, the recovery control unit 40 transfers the process to step S110. On the other hand, if the result of the determination in step S108 is negative, the recovery control unit 40 returns the process to step S100.

[0133] That is, the process in step S110 is executed when the ejection state of the nozzle N does not recover from the first abnormality even if the circulation of the ink is continued for a time corresponding to the product of a predetermined time and a predetermined number of times. In other words, when the result of the determination of the ejection state of the nozzle N by the determination unit 3 after the circulation of the ink by the circulation mechanism 6 is continued for a time corresponding to the product of the predetermined time and the predetermined number of times indicates that the first abnormality continues, the process in step S110 is executed. Note that the time corresponding to the product of the predetermined time and the predetermined number of times is an example of the "first time".

[0134] In step S110, the recovery control unit 40 increases the circulation flow rate of the ink. For example, the recovery control unit 40 controls the pumps 63 and 64 to increase the positive pressure Pin applied to the common flow path R1 and the negative pressure Pout applied to the common flow path R2. Specifically, the recovery control unit 40 controls the pumps 63 and 64 such that, for example, the positive pressure Pin becomes +10 [Pa] from the current positive pressure Pin and the negative pressure Pout becomes -10 [Pa] from the current negative pressure Pout. Note that the increase amounts of the positive pressure Pin and the negative pressure Pout are not limited to the above example.

[0135] Then, in step S112, after waiting for a predetermined time, the recovery control unit 40 transfers the process to step S114. Note that the predetermined time in step S112 may be the same as the predetermined time in step S102 or may be different from the predetermined time in step S102.

[0136] In step S114, the recovery control unit 40 acquires, from the determination unit 3, determination result information Rinf indicating the determination result of the ejection state of the nozzle N, as in step S104.

[0137] Next, in step S116, the recovery control unit 40 determines based on the determination result information Rinf whether or not the discharge state of the nozzle N has recovered from the first abnormality to a normal state. If the result of the determination in step S116 is affirmative, the recovery control unit 40 ends the first recovery process shown in FIG. 9. On the other hand, if the result of the determination in step S116 is negative, the recovery control unit 40 transfers the process to step S118.

[0138] In step S118, the recovery control unit 40 determines whether or not a series of processes from step S110 to step S116 have been executed a predetermined number of times. If the result of the determination in step S118 is affirmative, the recovery control unit 40 transfers the process to step S120. On the other hand, if the result of the determination in step S118 is negative, the recovery control unit 40 returns the process to step S110. That is, if the discharge state of the nozzle N does not recover from the first abnormality to a normal state even when the circulation flow rate of the ink is increased and the circulation of the ink is continued for a predetermined time, the process of step S110 is executed again.

[0139] Note that the predetermined number of times used for the determination in step S118 may be the same as the predetermined number of times used for the determination in step S108, or may be a different number of times from the predetermined number of times used for the determination in step S108. The predetermined number of times used for the determination in step S118 is an example of the "first number of times".

[0140] In step S120, the recovery control unit 40 increases the positive pressure Pin applied to the common flow path R1 by controlling the pump 63. For example, the recovery control unit 40 controls the pump 63 so that the positive pressure Pin becomes +10 [Pa] from the current positive pressure Pin, and controls the pump 64 so that the negative pressure Pout is maintained at the current negative pressure Pout. Note that the increase amount of the positive pressure Pin is not limited to the above example.

[0141] Then, in step S122, after waiting for a predetermined time, the recovery control unit 40 transfers the process to step S124. Note that the predetermined time in step S122 may be the same as the predetermined time in step S102, or may be different from the predetermined time in step S102.

[0142] In step S124, the recovery control unit 40 obtains determination result information Rinf indicating the determination result of the discharge state of the nozzle N from the determination unit 3 in the same manner as in step S104.

[0143] Next, in step S126, the recovery control unit 40 determines based on the determination result information Rinf whether the discharge state of the nozzle N has recovered from the first abnormality to a normal state. If the result of the determination in step S126 is affirmative, the recovery control unit 40 ends the first recovery process shown in FIG. 9. On the other hand, if the result of the determination in step S126 is negative, the recovery control unit 40 transfers the process to step S128.

[0144] In step S128, the recovery control unit 40 determines whether a series of processes from step S120 to step S126 has been executed a predetermined number of times. If the result of the determination in step S128 is affirmative, the recovery control unit 40 ends the first recovery process shown in FIG. 9 on the assumption that the discharge state of the nozzle N cannot recover to a normal state. On the other hand, if the result of the determination in step S128 is negative, the recovery control unit 40 returns the process to step S120. That is, if the discharge state of the nozzle N does not recover from the first abnormality to a normal state even when the positive pressure Pin is increased and the ink circulation is continued for a predetermined time, the process of step S120 is executed again.

[0145] Note that the predetermined number of times used for the determination in step S128 may be the same as the predetermined number of times used for the determination in step S108, or may be different from the predetermined number of times used for the determination in step S108.

[0146] Note that the first recovery process is not limited to the example shown in FIG. 9. For example, in step S120, the recovery control unit 40 may maintain the positive pressure Pin at the current positive pressure Pin and decrease the negative pressure Pout. Specifically, in step S120, the recovery control unit 40 may control the pump 63 so that the positive pressure Pin is maintained at the current positive pressure Pin, and control the pump 64 so that the negative pressure Pout becomes +10 [Pa] from the current negative pressure Pout. That is, in step S120, the recovery control unit 40 increases the ratio of the positive pressure Pin to the absolute value of the negative pressure Pout. Also, the process of step S100 may be regarded as the "first recovery process".

[0147] Next, with reference to FIG. 10, the second recovery process executed when the discharge state of the nozzle N is a second abnormality caused by thickening of the ink in the nozzle N will be described.

[0148] FIG. 10 is a flowchart showing an example of the second recovery process. Note that the second recovery process is executed when the discharge state of the nozzle N is a second abnormality caused by thickening of the ink in the nozzle N. That is, the process of step S200 is executed when the determination unit 3 determines that the discharge state of the nozzle N is a second abnormality. Note that the second recovery process shown in FIG. 10, that is, the series of processes from step S200 to step S218, is executed by the control unit 4 that functions as the recovery control unit 40. Also, detailed description of processes similar to those described in FIG. 9 will be omitted.

[0149] First, in step S200, the recovery control unit 40 increases the circulation flow rate of the ink. For example, the recovery control unit 40 increases the positive pressure Pin applied to the common flow path R1 and the negative pressure Pout applied to the common flow path R2 by controlling the pumps 63 and 64. Specifically, the recovery control unit 40 controls the pumps 63 and 64 so that, for example, the positive pressure Pin becomes +20 [Pa] from the current positive pressure Pin and the negative pressure Pout becomes -20 [Pa] from the current negative pressure Pout. Note that the increase amounts of the positive pressure Pin and the negative pressure Pout are not limited to the above example.

[0150] Then, in step S202, after waiting for a predetermined time, the recovery control unit 40 moves the process to step S204. Note that the predetermined time in step S202 may be the same as the predetermined time in step S102 shown in FIG. 9, or may be different from the predetermined time in step S102.

[0151] In step S204, the recovery control unit 40 acquires determination result information Rinf indicating the determination result of the discharge state of the nozzle N from the determination unit 3, in the same manner as in step S104 shown in FIG. 9.

[0152] Next, in step S206, the recovery control unit 40 determines based on the determination result information Rinf whether the discharge state of the nozzle N has recovered from the second abnormality to a normal state. If the result of the determination in step S206 is affirmative, the recovery control unit 40 ends the second recovery process shown in FIG. 10. On the other hand, if the result of the determination in step S206 is negative, the recovery control unit 40 moves the process to step S208.

[0153] In step S208, the recovery control unit 40 determines whether a series of processes from step S200 to step S206 has been executed a predetermined number of times. Note that the predetermined number of times used for the determination in step S208 may be the same as the predetermined number of times used for the determination in step S108 shown in FIG. 9, or may be different from the predetermined number of times used for the determination in step S108.

[0154] If the result of the determination in step S208 is negative, the recovery control unit 40 returns the process to step S200. That is, when increasing the circulation flow rate of the ink and continuing the circulation of the ink for a predetermined time, if the discharge state of the nozzle N does not recover from the second abnormality to the normal state, the process of step S200 is executed again. In other words, when the result of the determination of the discharge state of the nozzle N by the determination unit 3 after increasing the circulation flow rate of the ink and continuing the circulation of the ink for a predetermined time indicates that the second abnormality continues, the recovery control unit 40 further increases the circulation flow rate of the ink in step S200. Note that the predetermined time in step S202 is an example of the "second time".

[0155] On the other hand, if the result of the determination in step S208 is positive, the recovery control unit 40 moves the process to step S210. That is, the process of step S210 is executed when the discharge state of the nozzle N does not recover from the second abnormality to the normal state even if the control of increasing the circulation flow rate of the ink and continuing the circulation of the ink for a predetermined time is executed a predetermined number of times. In other words, when the result of the determination of the discharge state of the nozzle N by the determination unit 3 after executing the control of increasing the circulation flow rate of the ink and continuing the circulation of the ink for a predetermined time a predetermined number of times indicates that the second abnormality continues, the process of step S210 is executed. Note that the predetermined number of times used for the determination in step S208 is an example of the "second number of times".

[0156] In step S210, the recovery control unit 40 makes the intensity of the fine vibration waveform applied to the piezoelectric element PZ stronger than the current intensity. The intensity of the fine vibration waveform becomes stronger, for example, by increasing the amplitude of the fine vibration waveform. In the present embodiment, the pulse PB of the drive signal COMb is applied to the piezoelectric element PZ as the fine vibration waveform. Therefore, the recovery control unit 40 controls the drive signal generation unit 2, for example, to make the amplitude of the pulse PB of the drive signal COMb larger than the current amplitude.

[0157] Then, in step S212, after waiting for a predetermined time, the recovery control unit 40 transfers the process to step S214. Note that the predetermined time in step S212 may be the same as the predetermined time in step S102 shown in FIG. 9, or may be different from the predetermined time in step S102.

[0158] In step S214, the recovery control unit 40 obtains determination result information Rinf indicating the determination result of the discharge state of the nozzle N from the determination unit 3, in the same manner as in step S104 shown in FIG. 9.

[0159] Next, in step S216, the recovery control unit 40 determines based on the determination result information Rinf whether the discharge state of the nozzle N has recovered from the second abnormality to a normal state. If the result of the determination in step S216 is affirmative, the recovery control unit 40 ends the second recovery process shown in FIG. 10. On the other hand, if the result of the determination in step S216 is negative, the recovery control unit 40 transfers the process to step S218.

[0160] In step S218, the recovery control unit 40 determines whether a series of processes from step S210 to step S216 have been executed a predetermined number of times. If the result of the determination in step S218 is affirmative, the recovery control unit 40 ends the second recovery process shown in FIG. 10, assuming that the discharge state of the nozzle N cannot recover to a normal state. On the other hand, if the result of the determination in step S218 is negative, the recovery control unit 40 returns the process to step S210. That is, when the discharge state of the nozzle N does not recover from the second abnormality to a normal state even if the intensity of the fine vibration waveform is increased and the ink circulation is continued for a predetermined time, the process of step S210 is executed again.

[0161] Note that the predetermined number of times used for the determination in step S218 may be the same as the predetermined number of times used for the determination in step S108 shown in FIG. 9, or may be different from the predetermined number of times used for the determination in step S108.

[0162] Note that the second recovery process is not limited to the example shown in FIG. 10. For example, the method of increasing the intensity of the fine vibration waveform in step S210 is not limited to increasing the amplitude of the pulse PB. Specifically, instead of increasing the amplitude of the pulse PB, or in addition to increasing the amplitude of the pulse PB, the recovery control unit 40 may control the drive signal generation unit 2 or the like so that the number of pulses PB applied to the piezoelectric element PZ in the unit period Tu increases. Also, the process of step S200 may be regarded as the "second recovery process".

[0163] Next, with reference to FIG. 11, the third recovery process executed when the discharge state of the nozzle N is a third abnormality caused by ink leakage from the nozzle N will be described.

[0164] FIG. 11 is a flowchart showing an example of the third recovery process. Note that the third recovery process is executed when the discharge state of the nozzle N is a third abnormality caused by ink leakage from the nozzle N. That is, the process of step S300 is executed when it is determined by the determination unit 3 that the discharge state of the nozzle N is a third abnormality. Note that the third recovery process shown in FIG. 11, that is, the series of processes from step S300 to step S318, is executed by the control unit 4 functioning as the recovery control unit 40. Also, detailed descriptions of processes similar to those described in FIGS. 9 and 10 are omitted.

[0165] First, in step S300, the recovery control unit 40 increases the negative pressure Pout applied to the common flow path R2 by controlling the pump 64. For example, the recovery control unit 40 controls the pump 63 so that the positive pressure Pin is maintained at the current positive pressure Pin, and controls the pump 64 so that the negative pressure Pout becomes -30 [Pa] from the current negative pressure Pout. Note that the increase amount of the negative pressure Pout is not limited to the above example.

[0166] Then, in step S302, after waiting for a predetermined time, the recovery control unit 40 transfers the process to step S304. Note that the predetermined time in step S302 may be the same as the predetermined time in step S102 shown in FIG. 9, or may be different from the predetermined time in step S102.

[0167] In step S304, the recovery control unit 40 obtains determination result information Rinf indicating the determination result of the discharge state of the nozzle N from the determination unit 3 in the same manner as in step S104 shown in FIG. 9.

[0168] Next, in step S306, the recovery control unit 40 determines based on the determination result information Rinf whether or not the discharge state of the nozzle N has recovered from the third abnormality to a normal state. If the result of the determination in step S306 is affirmative, the recovery control unit 40 ends the third recovery process shown in FIG. 11. On the other hand, if the result of the determination in step S306 is negative, the recovery control unit 40 transfers the process to step S308.

[0169] In step S308, the recovery control unit 40 determines whether or not a series of processes from step S300 to step S306 have been executed a predetermined number of times. Note that the predetermined number of times used for the determination in step S308 may be the same as the predetermined number of times used for the determination in step S108 shown in FIG. 9, or may be different from the predetermined number of times used for the determination in step S108.

[0170] If the result of the determination in step S308 is negative, the recovery control unit 40 returns the process to step S300. That is, when the discharge state of the nozzle N does not recover from the third abnormality to a normal state even if the negative pressure Pout is increased and the ink circulation is continued for a predetermined time, the process of step S300 is executed again.

[0171] On the other hand, if the result of the determination in step S308 is affirmative, the recovery control unit 40 transfers the process to step S310. That is, the process of step S310 is executed when, even if the control of increasing the negative pressure Pout and continuing the ink circulation for a predetermined time is executed a predetermined number of times, the discharge state of the nozzle N does not recover from the third abnormality to the normal state.

[0172] In step S310, the recovery control unit 40 controls the maintenance unit 7 to execute a wiping process of wiping off foreign matters such as ink adhering to the vicinity of the nozzle N with a wiper.

[0173] Then, in step S314, the recovery control unit 40 acquires determination result information Rinf indicating the determination result of the discharge state of the nozzle N from the determination unit 3 in the same manner as step S104 shown in FIG. 9.

[0174] Next, in step S316, the recovery control unit 40 determines whether or not the discharge state of the nozzle N has recovered from the third abnormality to the normal state based on the determination result information Rinf. If the result of the determination in step S316 is affirmative, the recovery control unit 40 ends the third recovery process shown in FIG. 10. On the other hand, if the result of the determination in step S316 is negative, the recovery control unit 40 transfers the process to step S318.

[0175] In step S318, the recovery control unit 40 determines whether or not a series of processes from step S310 to step S316 have been executed a predetermined number of times. If the result of the determination in step S318 is affirmative, the recovery control unit 40 ends the third recovery process shown in FIG. 11 on the assumption that the discharge state of the nozzle N cannot recover to the normal state. On the other hand, if the result of the determination in step S318 is negative, the recovery control unit 40 returns the process to step S310 and executes the wiping process again. Note that the predetermined number of times used for the determination in step S318 may be the same as the predetermined number of times used for the determination in step S108 shown in FIG. 9, or may be a different number from the predetermined number of times used for the determination in step S108.

[0176] Note that the third recovery process is not limited to the example shown in FIG. 11. For example, in step S300, the recovery control unit 40 may maintain the negative pressure Pout at the current negative pressure Pout and decrease the positive pressure Pin. Specifically, the recovery control unit 40 may control the pump 63 so that the positive pressure Pin becomes -30 [Pa] from the current positive pressure Pin, and control the pump 64 so that the negative pressure Pout is maintained at the current negative pressure Pout. That is, in step S300, the recovery control unit 40 increases the ratio of the absolute value of the negative pressure Pout to the positive pressure Pin. Also, the process of step S300 may be regarded as the "third recovery process".

[0177] As described above, in the present embodiment, the recovery control unit 40 executes different processes according to the type of abnormality in the discharge state of the nozzle N as a recovery process for recovering the discharge state of the nozzle N to a normal state by controlling the circulation mechanism 6. That is, in the present embodiment, by appropriately adjusting the ink circulation according to the type of abnormality in the discharge state of the nozzle N, the discharge state of the nozzle N can be recovered to a normal state.

[0178] For example, when the first abnormality caused by the mixing of air bubbles from the interface of the nozzle N into the nozzle N has occurred, as shown in FIG. 9, even if the circulation flow rate at that time is continued by the process of step S100, the air bubbles should go toward the common flow path R2. On the other hand, when the second abnormality caused by the thickening of the ink in the nozzle N due to the evaporation of the ink at the interface of the nozzle N has occurred, the thickening in the nozzle N cannot be sufficiently refreshed even with the circulation flow rate at that time, and there is a possibility that the thickening will progress with the circulation flow rate at that time. Therefore, when the second abnormality has occurred, as shown in FIG. 10, it is preferable to increase the ink circulation flow rate by the process of step S200. Also, when the third abnormality caused by the leakage of the ink to the outside of the nozzle N along the attached paper powder or foreign matter has occurred, as shown in FIG. 11, by the process of step S300, it is preferable to increase the negative pressure or decrease the positive pressure to strengthen the force for discharging the ink to the common flow path R2.

[0179] As described above, in this embodiment, the liquid ejection device 100 includes a piezoelectric element PZ, a plurality of individual flow paths RK each including a pressure chamber CV and a nozzle N that ejects ink, a common flow path R1 that communicates with the plurality of individual flow paths RK in common and supplies ink to the plurality of individual flow paths RK, a common flow path R2 that communicates with the plurality of individual flow paths RK in common and discharges ink from the plurality of individual flow paths RK, a determination unit 3 that determines the ejection state of the nozzle N based on residual vibration generated in the pressure chamber CV after a voltage is applied to the piezoelectric element PZ, a circulation mechanism 6 that circulates ink from the common flow path R1 through the plurality of individual flow paths RK to the common flow path R2, and a recovery control unit 40 that executes a recovery process for recovering the ejection state of the nozzle N to a normal state by controlling the circulation mechanism 6 when an abnormality occurs in the ejection state of the nozzle N. The recovery control unit 40 executes different processes according to the type of abnormality determined by the determination unit 3 as the recovery process.

[0180] As described above, in this embodiment, the recovery control unit 40 executes different processes according to the type of abnormality in the ejection state of the nozzle N as a recovery process for recovering the ejection state of the nozzle N to a normal state by controlling the circulation mechanism 6. Thereby, in this embodiment, by appropriately adjusting the ink circulation according to the type of abnormality in the ejection state of the nozzle N, the ejection state of the nozzle N can be recovered to a normal state.

[0181] Further, in the present embodiment, when the abnormality determined by the determination unit 3 is a first abnormality caused by the mixing of bubbles into the nozzle N, the recovery control unit 40 performs a first recovery process of continuing the circulation of the ink by the circulation mechanism 6; when the abnormality determined by the determination unit 3 is a second abnormality caused by the thickening of the ink in the nozzle N, the recovery control unit 40 performs a second recovery process of increasing the circulation flow rate of the ink by the circulation mechanism 6; and when the abnormality determined by the determination unit 3 is a third abnormality caused by the leakage of the ink from the nozzle N, the recovery control unit 40 performs a third recovery process of increasing the ratio of the absolute value of the negative pressure Pout applied to the common flow path R2 to the positive pressure Pin applied to the common flow path R1. At least two of these may be executed as recovery processes. In this aspect, by appropriately adjusting the circulation of the ink according to the type of abnormality in the ejection state of the nozzle N, for example, at least two of the first abnormality, the second abnormality, and the third abnormality, the ejection state of the nozzle N can be restored to a normal state.

[0182] Further, in the present embodiment, the recovery control unit 40 may be capable of executing at least the first recovery process among the first recovery process, the second recovery process, and the third recovery process as a recovery process. In this aspect, when the type of abnormality in the ejection state of the nozzle N is the first abnormality, the circulation of the ink can be appropriately adjusted to restore the ejection state of the nozzle N to a normal state.

[0183] Further, in the present embodiment, in the first recovery process, when the result of the determination of the ejection state of the nozzle N by the determination unit 3 after continuing the circulation of the ink by the circulation mechanism 6 for a first period of time indicates that the first abnormality continues, the circulation flow rate may be increased. Also in this aspect, when the type of abnormality in the ejection state of the nozzle N is the first abnormality, the circulation of the ink can be appropriately adjusted to restore the ejection state of the nozzle N to a normal state. Further, in this aspect, when the type of abnormality in the ejection state of the nozzle N is the first abnormality, it is possible to suppress the failure to restore the ejection state of the nozzle N to a normal state.

[0184] Further, in the present embodiment, when the determination result of the discharge state of the nozzle N by the determination unit 3 after the recovery control unit 40 executes the control to increase the circulation flow rate a first number of times in the first recovery process indicates that the first abnormality continues, the ratio of the positive pressure Pin applied to the common flow path R1 to the absolute value of the negative pressure Pout applied to the common flow path R2 may be increased. Also in this aspect, when the type of abnormality in the discharge state of the nozzle N is the first abnormality, the ink circulation can be appropriately adjusted to recover the discharge state of the nozzle N to a normal state. Further, in this aspect, when the type of abnormality in the discharge state of the nozzle N is the first abnormality, it is possible to suppress the non-recovery of the discharge state of the nozzle N to a normal state as compared with the above-described aspect.

[0185] Further, in the present embodiment, the recovery control unit 40 may be capable of executing at least the second recovery process among the first recovery process, the second recovery process, and the third recovery process as a recovery process. In this aspect, when the type of abnormality in the discharge state of the nozzle N is the second abnormality, the ink circulation can be appropriately adjusted to recover the discharge state of the nozzle N to a normal state.

[0186] Further, in the present embodiment, when the determination result of the discharge state of the nozzle N by the determination unit 3 after the recovery control unit 40 increases the circulation flow rate and continues the circulation for a second time in the second recovery process indicates that the second abnormality continues, the circulation flow rate may be further increased. Also in this aspect, when the type of abnormality in the discharge state of the nozzle N is the second abnormality, the ink circulation can be appropriately adjusted to recover the discharge state of the nozzle N to a normal state. Further, in this aspect, when the type of abnormality in the discharge state of the nozzle N is the second abnormality, it is possible to suppress the non-recovery of the discharge state of the nozzle N to a normal state.

[0187] Further, in the present embodiment, in the second recovery process, a pulse PB having a fine vibration waveform such that ink is not ejected from the nozzle N may be applied to the piezoelectric element PZ. When the determination result of the ejection state of the nozzle N by the determination unit 3 after the recovery control unit 40 executes the control of increasing the circulation flow rate and continuing the circulation for a second time a second number of times in the second recovery process indicates that the second abnormality continues, the intensity of the pulse PB applied to the piezoelectric element PZ may be increased. Also in this aspect, when the type of abnormality in the ejection state of the nozzle N is the second abnormality, the ejection state of the nozzle N can be restored to a normal state by appropriately adjusting the circulation of the ink. Further, in this aspect, when the type of abnormality in the ejection state of the nozzle N is the second abnormality, it is possible to suppress the failure of the ejection state of the nozzle N to be restored to a normal state as compared with the above-described aspect.

[0188] Further, in the present embodiment, the recovery control unit 40 may be capable of executing at least the third recovery process among the first recovery process, the second recovery process, and the third recovery process as a recovery process. In this aspect, when the type of abnormality in the ejection state of the nozzle N is the third abnormality, the ejection state of the nozzle N can be restored to a normal state by appropriately adjusting the circulation of the ink.

[0189] [2. Modification Example] Each of the above embodiments can be variously modified. Specific modification modes are exemplified below. Two or more modes arbitrarily selected from the following examples can be appropriately combined within a range not conflicting with each other. In the modification examples exemplified below, for elements whose actions and functions are equivalent to those of the embodiment, the reference numerals referred to in the above description are used, and the detailed description of each is appropriately omitted.

[0190] [First Modification Example] In the above-described embodiments, the positive pressure Pin and the negative pressure Pout during the printing process executed after the discharge state of the nozzle N has been restored to a normal state by any one of the first recovery process, the second recovery process, and the third recovery process may be the final values of the recovery process. Alternatively, the positive pressure Pin and the negative pressure Pout during the printing process may be reset to a predetermined pressure. As described above, also in this modified example, the same effects as those of the above-described embodiments can be obtained.

[0191] [Second Modified Example] In the above-described embodiments and modified examples, when the process of step S120 shown in FIG. 9 is repeated, the recovery control unit 40 may alternately execute a process of increasing the positive pressure Pin applied to the common flow path R1 and a process of decreasing the negative pressure Pout applied to the common flow path R2. Similarly, when the process of step S300 shown in FIG. 11 is repeated, the recovery control unit 40 may alternately execute a process of increasing the negative pressure Pout applied to the common flow path R2 and a process of decreasing the positive pressure Pin applied to the common flow path R1. As described above, also in this modified example, the same effects as those of the above-described embodiments can be obtained. Further, in this modified example, it is possible to suppress only one of the positive pressure Pin and the negative pressure Pout from changing. Thereby, in this modified example, it is possible to suppress the positive pressure Pin or the negative pressure Pout from reaching a limit value due to the performance of the circulation mechanism 6 or the like.

[0192] [Third Modified Example] In the above-described embodiments and modified examples, the case where one discharge unit D includes two piezoelectric elements PZ, two pressure chambers CV, and one nozzle N has been exemplified, but the present invention is not limited to such a mode. For example, one piezoelectric element PZ, one pressure chamber CV, and one nozzle N may be provided for one discharge unit D. That is, when paying attention to the pressure chamber CV and the individual flow path RK, one individual flow path RK may include only one pressure chamber CV. As described above, also in this modified example, the same effects as those of the above-described embodiments and modified examples can be obtained.

[0193] [Fourth Modified Example] In the above-described embodiments and modified examples, the serial liquid ejection device 100 that reciprocates the carriage 91 equipped with the liquid ejection head 1 in the X-axis direction has been exemplified. However, the present invention is not limited to such an aspect. For example, the liquid ejection device 100 may be a line-type liquid ejection device in which a plurality of nozzles N are distributed over the entire width of the medium PP. As described above, also in this modified example, the same effects as those of the above-described embodiments and modified examples can be obtained.

[0194] [Fifth Modified Example] The liquid ejection device 100 exemplified in the above-described embodiments and modified examples can be adopted not only in devices dedicated to printing but also in various devices such as facsimile machines and copying machines. However, the use of the liquid ejection device of the present invention is not limited to printing. For example, a liquid ejection device that ejects a solution of a coloring material is used as a manufacturing device for forming a color filter of a liquid crystal display device. Also, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wirings and electrodes of a wiring board. As described above, also in this modified example, the same effects as those of the above-described embodiments and modified examples can be obtained.

[0195] [3. Supplementary Note] From the forms exemplified above, for example, the following configurations can be grasped.

[0196] The liquid ejection device according to Embodiment 1, which is a preferred embodiment, includes a piezoelectric element, a plurality of individual flow paths each including a pressure chamber and a nozzle for ejecting liquid, a common supply flow path that communicates with the plurality of individual flow paths in common and supplies liquid to the plurality of individual flow paths, a common discharge flow path that communicates with the plurality of individual flow paths in common and discharges liquid from the plurality of individual flow paths, a state determination unit that determines the ejection state of the nozzle based on residual vibration generated in the pressure chamber after applying a voltage to the piezoelectric element, a circulation unit that circulates liquid from the common supply flow path through the plurality of individual flow paths to the common discharge flow path, and a recovery control unit that executes a recovery process for restoring the ejection state of the nozzle to a normal state by controlling the circulation unit when there is an abnormality in the ejection state of the nozzle. The recovery control unit executes different processes according to the type of the abnormality determined by the state determination unit as the recovery process. According to Embodiment 1, by appropriately adjusting the circulation of the ink according to the type of abnormality in the ejection state of the nozzle N, the ejection state of the nozzle N can be restored to a normal state.

[0197] In the liquid ejection device according to Embodiment 2, which is a specific example of Embodiment 1, when the abnormality determined by the state determination unit is a first abnormality caused by the mixing of air bubbles into the nozzle, the recovery control unit can execute at least two of a first recovery process of continuing the circulation of the liquid by the circulation unit, a second recovery process of increasing the circulation flow rate of the liquid by the circulation unit when the abnormality determined by the state determination unit is a second abnormality caused by the thickening of the liquid in the nozzle, and a third recovery process of increasing the ratio of the absolute value of the negative pressure applied to the common discharge flow path to the positive pressure applied to the common supply flow path when the abnormality determined by the state determination unit is a third abnormality caused by the leakage of the liquid from the nozzle, as the recovery process. According to Embodiment 2, for at least two of the first abnormality, the second abnormality, and the third abnormality, the ejection state of the nozzle N can be restored to a normal state by appropriately adjusting the circulation of the ink.

[0198] In the liquid ejection device according to Aspect 3, which is a specific example of Aspect 2, the recovery control unit can execute at least the first recovery process among the first recovery process, the second recovery process, and the third recovery process as the recovery process. According to Aspect 3, when the type of abnormality in the ejection state of the nozzle N is the first abnormality, it is possible to appropriately adjust the circulation of the ink and recover the ejection state of the nozzle N to a normal state.

[0199] In the liquid ejection device according to Aspect 4, which is a specific example of Aspect 3, in the first recovery process, when the result of the determination of the ejection state of the nozzle by the state determination unit after continuing the circulation of the liquid by the circulation unit for a first period of time indicates that the first abnormality continues, the circulation flow rate is increased. Also in Aspect 4, when the type of abnormality in the ejection state of the nozzle N is the first abnormality, it is possible to appropriately adjust the circulation of the ink and recover the ejection state of the nozzle N to a normal state. Further, in Aspect 4, when the type of abnormality in the ejection state of the nozzle N is the first abnormality, it is possible to suppress the non-recovery of the ejection state of the nozzle N to a normal state compared to Aspect 3.

[0200] In the liquid ejection device according to Aspect 5, which is a specific example of Aspect 4, in the first recovery process, when the result of the determination of the ejection state of the nozzle by the state determination unit after executing the control to increase the circulation flow rate a first number of times indicates that the first abnormality continues, the ratio of the positive pressure applied to the common supply channel to the absolute value of the negative pressure applied to the common discharge channel is increased. Also in Aspect 5, when the type of abnormality in the ejection state of the nozzle N is the first abnormality, it is possible to appropriately adjust the circulation of the ink and recover the ejection state of the nozzle N to a normal state. Further, in Aspect 5, when the type of abnormality in the ejection state of the nozzle N is the first abnormality, it is possible to suppress the non-recovery of the ejection state of the nozzle N to a normal state compared to Aspect 4.

[0201] In the liquid ejection device according to Aspect 6, which is a specific example of any one of Aspects 2 to 5, the recovery control unit can execute at least the second recovery process among the first recovery process, the second recovery process, and the third recovery process as the recovery process. According to Aspect 6, when the type of abnormality in the ejection state of the nozzle N is the second abnormality, it is possible to appropriately adjust the circulation of the ink and recover the ejection state of the nozzle N to a normal state.

[0202] In the liquid ejection device according to Aspect 7, which is a specific example of Aspect 6, in the second recovery process, when the result of the determination of the ejection state of the nozzle by the state determination unit after increasing the circulation flow rate and continuing the circulation for a second time indicates that the second abnormality continues, the recovery control unit further increases the circulation flow rate. Also in Aspect 7, when the type of abnormality in the ejection state of the nozzle N is the second abnormality, it is possible to appropriately adjust the circulation of the ink and recover the ejection state of the nozzle N to a normal state. Further, in Aspect 7, when the type of abnormality in the ejection state of the nozzle N is the second abnormality, it is possible to suppress the non-recovery of the ejection state of the nozzle N to a normal state as compared with Aspect 6.

[0203] In the liquid ejection device according to Aspect 8, which is a specific example of Aspect 7, in the second recovery process, a fine vibration waveform with which liquid is not ejected from the nozzle is applied to the piezoelectric element, and in the second recovery process, when the result of the determination of the ejection state of the nozzle by the state determination unit after executing the control of increasing the circulation flow rate and continuing the circulation for the second time a second number of times indicates that the second abnormality continues, the intensity of the fine vibration waveform applied to the piezoelectric element is increased. Also in Aspect 8, when the type of abnormality in the ejection state of the nozzle N is the second abnormality, it is possible to appropriately adjust the circulation of the ink and recover the ejection state of the nozzle N to a normal state. Further, in Aspect 8, when the type of abnormality in the ejection state of the nozzle N is the second abnormality, it is possible to suppress the non-recovery of the ejection state of the nozzle N to a normal state as compared with Aspect 7.

[0204] In the liquid ejection device according to Aspect 9, which is a specific example of any one of Aspects 2 to 8, the recovery control unit can execute at least the third recovery process among the first recovery process, the second recovery process, and the third recovery process as the recovery process. According to Aspect 9, when the type of abnormality in the ejection state of the nozzle N is the third abnormality, it is possible to appropriately adjust the ink circulation and restore the ejection state of the nozzle N to a normal state.

[0205] In the liquid ejection device according to Aspect 10, which is a specific example of Aspect 2, in the first recovery process, when the result of the determination of the ejection state of the nozzle by the state determination unit after continuing the circulation of the liquid by the circulation unit for a first time indicates that the first abnormality continues, the absolute values of the positive pressure and the negative pressure are increased to increase the circulation flow rate. In the second process, the absolute values of the positive pressure and the negative pressure are increased to increase the circulation flow rate. In the third process, the positive pressure is maintained and the absolute value of the negative pressure is increased to increase the ratio. When the ratio is increased once in the third process, the increase amount of the absolute value of the negative pressure is larger than the increase amount of the absolute value of the negative pressure when the circulation flow rate is increased once in the second process. The increase amount of the absolute value of the negative pressure when the circulation flow rate is increased once in the second process is larger than the increase amount of the absolute value of the negative pressure when the circulation flow rate is increased once in the first process. According to Aspect 10, for the first abnormality, the second abnormality, and the third abnormality, it is possible to appropriately adjust the ink circulation and restore the ejection state of the nozzle N to a normal state.

[0206] Further, a control method for a liquid ejection device according to Embodiment 11, which is a preferred embodiment, includes a piezoelectric element, a plurality of individual flow paths each including a pressure chamber and a nozzle for ejecting liquid, a common supply flow path that communicates with the plurality of individual flow paths in common and supplies liquid to the plurality of individual flow paths, a common discharge flow path that communicates with the plurality of individual flow paths in common and discharges liquid from the plurality of individual flow paths, a state determination unit that determines the ejection state of the nozzle based on residual vibration generated in the pressure chamber after a voltage is applied to the piezoelectric element, and a circulation unit that circulates liquid from the common supply flow path through the plurality of individual flow paths to the common discharge flow path. The control method for the liquid ejection device is such that when there is an abnormality in the ejection state of the nozzle, a recovery process is executed to recover the ejection state of the nozzle to a normal state by controlling the circulation unit, and the recovery process is different depending on the type of abnormality determined by the state determination unit. According to Embodiment 11, by appropriately adjusting the circulation of the ink according to the type of abnormality in the ejection state of the nozzle N, the ejection state of the nozzle N can be restored to a normal state.

Description of Reference Numerals

[0207] 1... Liquid ejection head, 2... Drive signal generation unit, 3... Determination unit, 4... Control unit, 5... Storage unit, 6... Circulation mechanism, 7... Maintenance unit, 8... Medium conveyance mechanism, 9... Carriage conveyance mechanism, 10... Recording head, 18... Switching circuit, 19... Detection circuit, 40... Recovery control unit, 100... Liquid ejection device, CV... Pressure chamber, D... Ejection part, N... Nozzle, PP... Medium, PZ... Piezoelectric element.

Claims

1. A piezoelectric element, a plurality of individual flow paths each including a pressure chamber and a nozzle for discharging a liquid, a common supply flow path that communicates with the plurality of individual flow paths in common and supplies the liquid to the plurality of individual flow paths, a common discharge flow path that communicates with the plurality of individual flow paths in common and discharges the liquid from the plurality of individual flow paths, a state determination unit that determines a discharge state of the nozzle based on residual vibration generated in the pressure chamber after applying a voltage to the piezoelectric element, a circulation unit that circulates the liquid from the common supply flow path through the plurality of individual flow paths to the common discharge flow path, a recovery control unit that executes a recovery process for recovering the discharge state of the nozzle to a normal state by controlling the circulation unit when there is an abnormality in the discharge state of the nozzle, comprising, the recovery control unit, as the recovery process, executes different processes according to the type of the abnormality determined by the state determination unit, A liquid discharge device characterized by the above.

2. the recovery control unit, when the abnormality determined by the state determination unit is a first abnormality caused by air bubbles entering the nozzle, a first recovery process of continuing the circulation of the liquid by the circulation unit; when the abnormality determined by the state determination unit is a second abnormality caused by thickening of the liquid in the nozzle, a second recovery process of increasing the circulation flow rate of the liquid by the circulation unit; when the abnormality determined by the state determination unit is a third abnormality caused by leakage of the liquid from the nozzle, a third recovery process of increasing the ratio of the absolute value of the negative pressure applied to the common discharge flow path to the positive pressure applied to the common supply flow path; at least two of the above can be executed as the recovery process, The liquid discharge device according to claim 1, characterized by the above.

3. the recovery control unit can execute at least the first recovery process among the first recovery process, the second recovery process, and the third recovery process as the recovery process, The liquid discharge device according to claim 2, characterized by the above.

4. the recovery control unit, in the first recovery process, when the result of the determination of the discharge state of the nozzle by the state determination unit after continuing the circulation of the liquid by the circulation unit for a first time indicates that the first abnormality continues, the circulation flow rate is increased, The liquid discharge device according to claim 3, characterized by the above.

5. the recovery control unit, In the first recovery process, when the result of the determination of the discharge state of the nozzle by the state determination unit after executing the control for increasing the circulation flow rate a first number of times indicates that the first abnormality continues, increasing the ratio of the positive pressure applied to the common supply flow path to the absolute value of the negative pressure applied to the common discharge flow path The liquid discharge device according to claim 4, characterized in that

6. The recovery control unit is capable of executing at least the second recovery process among the first recovery process, the second recovery process, and the third recovery process as the recovery process The liquid discharge device according to claim 2, characterized in that

7. The recovery control unit In the second recovery process, when the result of the determination of the discharge state of the nozzle by the state determination unit after increasing the circulation flow rate and continuing the circulation for a second time indicates that the second abnormality continues, further increasing the circulation flow rate The liquid discharge device according to claim 6, characterized in that

8. In the second recovery process, a fine vibration waveform at which liquid is not discharged from the nozzle is applied to the piezoelectric element The recovery control unit In the second recovery process, when the result of the determination of the discharge state of the nozzle by the state determination unit after executing the control for increasing the circulation flow rate and continuing the circulation for the second time a second number of times indicates that the second abnormality continues, increasing the intensity of the fine vibration waveform applied to the piezoelectric element The liquid discharge device according to claim 7, characterized in that

9. The recovery control unit is capable of executing at least the third recovery process among the first recovery process, the second recovery process, and the third recovery process as the recovery process The liquid discharge device according to claim 2, characterized in that

10. A piezoelectric element A plurality of individual flow paths each including a pressure chamber and a nozzle for discharging liquid A common supply flow path that communicates with the plurality of individual flow paths in common and supplies liquid to the plurality of individual flow paths A common discharge flow path that communicates with the plurality of individual flow paths in common and discharges liquid from the plurality of individual flow paths A state determination unit that determines the discharge state of the nozzle based on residual vibration generated in the pressure chamber after applying a voltage to the piezoelectric element A circulation unit that circulates liquid from the common supply flow path through the plurality of individual flow paths to the common discharge flow path A control method for a liquid discharge device comprising When there is an abnormality in the discharge state of the nozzle, a recovery process is executed to recover the discharge state of the nozzle to a normal state by controlling the circulation unit. The recovery process is a different process according to the type of the abnormality determined by the state determination unit. A control method for a liquid discharge device, characterized by the above.

Images