Liquid discharge apparatus, control method for liquid discharging apparatus, and control program for liquid discharging apparatus

Abstract

To appropriately adjust a pressure in the vicinity of the nozzle.SOLUTION: A liquid discharge apparatus 100 includes: a piezoelectric element PZ; a plurality of individual flow paths RK each including a nozzle N and a pressure chamber CV; a common flow path RC1 which communicates in common with the plurality of individual flow paths RK and through which ink is supplied to the plurality of individual flow paths RK; a common flow path RC2 which communicates in common with the plurality of individual flow paths RK and through which the ink is drained from the plurality of individual flow paths RK; a pump 63 for applying, to the common flow path RC1, a pressure Pin for supplying the ink to the common flow path RC1; a pump 64 for applying, to the common flow path RC2, a pressure Pout for draining the ink from the common flow path RC2; a detection circuit 19 which detects residual vibration in the pressure chamber CV after a voltage is applied to the piezoelectric element PZ; and a circulation control unit 40 which determines each of the pressure Pin and the pressure Pout on the basis of the residual vibration detected by the detection circuit 19.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In a liquid ejection device such as an inkjet printer, a liquid ejection head is filled with a liquid such as ink, and then the liquid is ejected from the liquid ejection head. To prevent air bubbles from remaining in the liquid and the liquid from thickening, a technique for circulating the liquid within 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 ejected from the liquid ejection head back to the liquid ejection head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-24082 Summary of the Invention [Problem to be solved by the invention]

[0004] In a liquid ejection device that circulates liquid within a flow path provided in a liquid ejection head, it is necessary to appropriately adjust the pressure in the vicinity of the nozzles in order to achieve desired ejection characteristics of the liquid ejection head. [Means for solving the problem]

[0005] In order to solve the above problems, the liquid ejection device of the present invention comprises a piezoelectric element, a plurality of individual flow paths each including a nozzle and a pressure chamber, a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths, a common discharge flow path that is commonly connected to the plurality of individual flow paths and discharges liquid from the plurality of individual flow paths, a first pressure application unit that applies a first pressure to the common supply flow path to supply liquid to the common supply flow path, a second pressure application unit that applies a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path, a detection unit that detects residual vibrations in the pressure chambers after applying a voltage to the piezoelectric element, and a pressure determination unit that determines the first pressure and the second pressure based on the residual vibrations detected by the detection unit.

[0006] Furthermore, a control method for a liquid ejection device according to the present invention is a control method for a liquid ejection device comprising a piezoelectric element, a plurality of individual flow paths each including a nozzle and a pressure chamber, a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths, a common discharge flow path that is commonly connected to the plurality of individual flow paths and discharges liquid from the plurality of individual flow paths, a first pressure application unit that applies a first pressure to the common supply flow path to supply liquid to the common supply flow path, a second pressure application unit that applies a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path, and a detection unit that detects residual vibrations in the pressure chambers after applying a voltage to the piezoelectric element, and the first pressure and the second pressure are each determined based on the residual vibrations detected by the detection unit.

[0007] Furthermore, a control program for a liquid ejection device according to the present invention is a control program for a liquid ejection device comprising a piezoelectric element, a plurality of individual flow paths each including a nozzle and a pressure chamber, a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths, a common discharge flow path that is commonly connected to the plurality of individual flow paths and discharges liquid from the plurality of individual flow paths, a first pressure application unit that applies a first pressure to the common supply flow path to supply liquid to the common supply flow path, a second pressure application unit that applies a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path, and a detection unit that detects residual vibrations in the pressure chambers after applying a voltage to the piezoelectric element, and causes a computer to function as a pressure determination unit that determines the first pressure and the second pressure based on the residual vibrations detected by the detection unit. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing an example of a configuration of a liquid ejection apparatus according to an embodiment of the present invention. [Figure 2] FIG. 1 is a configuration diagram schematically illustrating a liquid ejection device. [Figure 3] FIG. 2 is an exploded perspective view showing an example of the configuration of a liquid ejection head. [Figure 4] FIG. 2 is a cross-sectional view showing an example of the configuration of a liquid ejection head. [Figure 5] FIG. 4 is an explanatory diagram for explaining the flow of ink. [Figure 6] FIG. 2 is a block diagram showing an example of the configuration of a liquid ejection head. [Figure 7] 10 is a timing chart showing an example of an operation of the liquid ejection device in a unit period. [Figure 8] FIG. 10 is an explanatory diagram for explaining an outline of the operation of the circulation control unit. [Figure 9] 10 is a flowchart illustrating an example of an operation of the liquid ejection device. [Figure 10] FIG. 10 is an exploded perspective view showing an example of the configuration of a liquid ejection head according to a first modified example. [Figure 11]11 is a cross-sectional view showing an example of the configuration of the liquid ejection head shown in FIG. [Figure 12] FIG. 10 is an explanatory diagram for explaining the flow of ink in a first modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part are appropriately different from those of the actual parts. Furthermore, since the embodiments described below are preferred examples of the present invention, various technically preferable limitations are applied, but the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited.

[0010] [1. Embodiment] First, an overview of a liquid ejection device 100 according to this embodiment will be described with reference to Fig. 1. In this embodiment, a case will be taken as an example in which the liquid ejection device 100 is an inkjet printer that forms an image by ejecting ink onto a medium PP. In this embodiment, the medium PP will be assumed to be recording paper shown in Fig. 2, which will be described later.

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

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

[0013] The liquid ejection device 100 includes a liquid ejection head 1 provided with an ejection section D including nozzles N that eject ink, a drive signal generation unit 2 that generates a plurality of drive signals COM for driving the ejection section D, and a viscosity estimation unit 3 that estimates the viscosity of the ink in the ejection section D. Note that the nozzles N will be described later with reference to FIGS. 3 and 4. The liquid ejection device 100 also includes a control unit 4 that controls each section of the liquid ejection device 100, and a storage unit 5 that stores various information such as print data IMG and a control program PG for the liquid ejection device 100. The liquid ejection device 100 also includes a circulation mechanism 6 that circulates the ink, a maintenance unit 7 that performs maintenance processing for the liquid ejection head 1, a medium transport mechanism 8 that transports the medium PP, and a carriage transport mechanism 9 that reciprocates a carriage 91. Note that the carriage 91 will be described later with reference to FIG. 2.

[0014] In this 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 viscosity estimation 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 have a plurality of liquid ejection heads 1, a plurality of drive signal generation units 2, a plurality of viscosity estimation 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 one-to-one, the plurality of viscosity estimation units 3 correspond to the plurality of liquid ejection heads 1 one-to-one, and the plurality of circulation mechanisms 6 correspond to the plurality of liquid ejection heads 1 one-to-one. Alternatively, the liquid ejection device 100 may have one liquid ejection head 1, one drive signal generation unit 2 corresponding to the liquid ejection head 1, one viscosity estimation 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 ink: 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 viscosity estimation units 3, and four circulation mechanisms 6. However, for convenience of explanation, the following description may focus on one of the four liquid ejection heads 1, and one drive signal generation unit 2, one viscosity estimation unit 3, and one circulation mechanism 6 corresponding to that one liquid ejection head 1, as exemplified in FIG. 1 .

[0016] First, before describing the liquid ejection head 1, the control unit 4, the drive signal generating unit 2, and the storage unit 5 will be described.

[0017] The control unit 4 is configured to include one or more CPUs (Central Processing Units). 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 a CPU. Also, for example, the control unit 4 operates in accordance with a control program PG stored in the storage unit 5 to generate signals for controlling the operation of each part of the liquid ejection device 100, such as a print signal SI and a waveform designation signal dCOM.

[0018] Here, the waveform designation signal dCOM is a digital signal that defines the waveform of each of the multiple drive signals COM. Furthermore, each drive signal COM is an analog signal for driving a discharge section D. In this embodiment, as shown in FIG. 6 (to be described later), it is assumed that the multiple drive signals COM include drive signals COMa and COMb. Furthermore, the print signal SI is a digital signal for designating the type of operation of the discharge section D. Specifically, the print signal SI is a signal that designates whether or not to supply each drive signal COM to the discharge section D, thereby designating the type of operation of the discharge section D.

[0019] In this embodiment, the control unit 4 operates in accordance with the control program PG stored in the storage unit 5, thereby functioning as a circulation control unit 40 that controls the circulation mechanism 6. For example, the circulation control unit 40 generates a control signal Ctr for controlling the operation of the circulation mechanism 6, and outputs the generated control signal Ctr to the circulation mechanism 6. The control unit 4 is an example of a "computer," and the circulation control unit 40 is an example of a "pressure determination unit." Details of the operation of the circulation control unit 40 will be described in FIGS. 8 and 9.

[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 ejection head 1.

[0021] The storage unit 5 includes 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). The storage unit 5 may be included in the control unit 4.

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

[0023] The recording head 10 has M discharge units D. The value M is a natural number equal to or greater than 1. Hereinafter, the jth discharge unit D among the M discharge units D provided in the recording head 10 may be referred to as discharge unit D[j]. Hereinafter, the variable j is a natural number satisfying "1≦j≦M". Also, below, when a component or signal of the liquid ejection device 100 corresponds to a discharge unit D[j] among the M discharge units D, the subscript [j] may be added to the symbol representing the component or signal.

[0024] The switching circuit 18 switches whether to supply each drive signal COM to the discharge unit D[j] based on the print signal SI. Note that, hereinafter, as shown in FIG. 6 and other figures, the drive signal COM supplied to the discharge unit D[j] among the multiple drive signals COM may be referred to as an individual drive signal Vin[j]. The switching circuit 18 also switches whether to electrically connect the discharge unit D[j] to the detection circuit 19 based on the print signal SI. When the discharge unit D[j] and the detection circuit 19 are electrically connected, for example, a detection signal Vout[j] detected from the discharge unit D[j] is supplied to the detection circuit 19 via the switching circuit 18. The detection signal Vout[j] indicates, for example, the waveform of residual vibration, which is vibration remaining in the discharge unit D[j] after the discharge unit D[j] is driven by the individual drive signal Vin[j].

[0025] The detection circuit 19 generates the residual vibration signal Vd[j] based on the detection signal Vout[j]. For example, the detection circuit 19 amplifies the amplitude of the detection signal Vout[j] or removes noise components contained in the detection signal Vout[j], thereby shaping the detection signal Vout[j] into a waveform suitable for processing in the viscosity estimation unit 3. In this way, the residual vibration signal Vd[j] is generated. For example, the detection circuit 19 may be configured to include a negative feedback amplifier for amplifying the detection signal Vout[j], a low-pass filter for attenuating high frequency components of the detection signal Vout[j], and a voltage follower for converting impedance and outputting a low-impedance residual vibration signal Vd[j].

[0026] The detection circuit 19 outputs a residual vibration signal Vd[j] generated based on the detection signal Vout[j] to the viscosity estimation unit 3. The detection circuit 19 is an example of a "detection unit."

[0027] The viscosity estimation unit 3 estimates the viscosity of the ink in the ejection unit D[j] based on the residual vibration signal Vd[j]. Note that the residual vibration signal Vd[j] used to estimate the viscosity of the ink in the ejection unit D[j] is generated based on the detection signal Vout[j], and therefore indicates the waveform of the residual vibration of the ejection unit D[j] after it has been driven by the individual drive signal Vin[j].

[0028] For example, the viscosity estimation unit 3 may detect the viscosity relative to a predetermined viscosity by comparing the feature quantities such as the amplitude and period of the residual vibration signal Vd[j] with reference feature quantities of the residual vibration signal when the ink has a predetermined viscosity. Alternatively, the viscosity estimation unit 3 may calculate the damping rate of the residual vibration based on the damping rate of the amplitude of the residual vibration signal Vd[j], and estimate the viscosity of the ink based on the calculated damping rate of the residual vibration.

[0029] Furthermore, the viscosity estimation unit 3 generates viscosity information Vinf indicating the viscosity of the ink estimated based on, for example, the residual vibration, and outputs the generated viscosity information Vinf to the control unit 4. The viscosity estimation unit 3 may be included in the control unit 4. For example, the control unit 4 may function as the viscosity estimation unit 3 by operating in accordance with a control program PG stored in the storage unit 5. Furthermore, the elements including the viscosity estimation unit 3 and the circulation control unit 40 may be considered as a "pressure determination unit."

[0030] Furthermore, in this embodiment, as described above, the maintenance process is performed by the maintenance unit 7. For example, the maintenance unit 7 performs the maintenance process under the control of the control unit 4. The maintenance process includes, for example, a flushing process that discharges ink from the ejection section D, a wiping process that wipes off foreign matter such as ink adhering to the vicinity of the nozzle N of the ejection section D with a wiper, and a pumping process that sucks ink from inside the ejection section D with a tube pump or the like.

[0031] The maintenance unit 7 has a discharged ink receiving section for receiving the discharged ink when the ink in the discharge section D is discharged during the flushing process, a wiper for wiping off foreign matter such as ink adhering to the vicinity of the nozzle N of the discharge section D, and a tube pump for sucking ink, air bubbles, etc. from the discharge section D. The discharged ink receiving section, wiper, and tube pump are not shown in the drawings.

[0032] The configuration of the liquid ejection device 100 is not limited to the example shown in Fig. 1. For example, the viscosity estimation unit 3 may have a function of determining the ejection state of the nozzle N included in the ejection unit D[j] based on the residual vibration signal Vd[j]. In this case, for example, the viscosity estimation unit 3 may determine the ejection state of the nozzle N by comparing detected values such as the amplitude and period of the residual vibration signal Vd[j] with reference values when the ejection state of the nozzle N is normal.

[0033] Next, the overall configuration of the liquid ejection device 100 will be described with reference to FIG.

[0034] 2 is a schematic diagram of the liquid ejection device 100. In FIG. 2, the circulation mechanism 6, the medium transport mechanism 8, and the carriage transport mechanism 9 will be mainly described.

[0035] The circulation mechanism 6 supplies the ink stored in the circulation mechanism 6 to the liquid ejection head 1 based on a control signal Ctr supplied from the control unit 4. The circulation mechanism 6 also recovers ink from the liquid ejection head 1 based on the control signal Ctr supplied from the control unit 4, and returns the recovered ink to the liquid ejection head 1.

[0036] For example, the circulation mechanism 6 has an ink container 60 that stores ink, a pump 63 connected to a supply flow path 61 that supplies ink to the liquid ejection head 1, and a pump 64 connected to a recovery flow path 62 that recovers ink discharged from the liquid ejection head 1. The ink container 60 may be, for example, a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of a flexible film, or an ink tank that can be refilled with ink. The type of ink stored in the ink container 60 is not particularly limited and may be any type. The pump 63 is an example of a "first pressure application unit," and the pump 64 is an example of a "second pressure application unit."

[0037] The pumps 63 and 64 are controlled by the control unit 4. For example, the pump 63 supplies ink stored in the ink container 60 to the liquid ejection head 1 via the supply flow path 61 based on a control signal Ctr supplied from the control unit 4. Also, for example, the pump 64 recovers ink from the liquid ejection head 1 via the recovery flow path 62 based on the control signal Ctr supplied from the control unit 4, and supplies the recovered ink to the ink container 60.

[0038] The circulation mechanism 6 may be defined without including the ink container 60, or may be defined to include the supply flow path 61 and the recovery flow path 62.

[0039] The medium conveying 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 will be collectively referred to as the Y-axis direction. Hereinafter, the X1 direction along the X axis intersecting the Y axis and the X2 direction opposite to the X1 direction will be collectively referred to as the X-axis direction. Hereinafter, the Z1 direction along the Z axis intersecting the X and Y axes and the Z2 direction opposite to the Z1 direction will be collectively referred to as the Z-axis direction. In this embodiment, as an example, a case will be described in which the X axis, Y axis, and Z axis are orthogonal to one another. However, the present invention is not limited to this example. It is sufficient that the X axis, Y axis, and Z axis intersect with one another.

[0040] The carriage transport 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 transport 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. The circulation mechanism 6 may be housed in the carriage 91 together with the liquid ejection heads 1.

[0041] 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 the multiple nozzles N provided in the liquid ejection head 1. That is, the liquid ejection head 1 ejects ink from some or all of the multiple nozzles N in conjunction with the transport of the medium PP by the medium transport mechanism 8 and the reciprocating movement of the liquid ejection head 1 by the carriage transport mechanism 9, and forms a desired image on the surface of the medium PP by causing the ejected ink to land on the surface of the medium PP.

[0042] Next, the general structure of the liquid ejection head 1 will be described with reference to FIGS.

[0043] Fig. 3 is an exploded perspective view showing an example of the configuration of the liquid ejection head 1. Fig. 4 is a cross-sectional view showing an example of the configuration of the liquid ejection head 1. The cross-sectional view shown in Fig. 4 is a cross-sectional view taken along line II-II shown in Fig. 3. The cross-section taken along line II-II is parallel to the XZ plane and passes through connection ports H1 and H2, which will be described later. Fig. 4 also shows, by a dashed line, a reference plane SF, which will be referred to in modified examples that will be described later.

[0044] 3 and 4, the liquid ejection head 1 has a nozzle substrate 11, a communication plate 12, a pressure chamber substrate 13, a vibration plate 14, a flow path forming substrate 16, and a wiring board 17 on which electronic components EC are mounted. The electronic components EC include, for example, electrical 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 board 17.

[0045] As shown in Fig. 3, the nozzle substrate 11 is a plate-like member that is long in the Y-axis direction and extends approximately parallel to the XY plane. Here, "approximately parallel" is a concept that includes not only completely parallel, but also parallel when an error is taken into consideration. In this embodiment, "approximately parallel" is a concept that includes parallel when an error of about 10% is taken into consideration. The nozzle substrate 11 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing techniques such as etching, for example, but known materials and manufacturing methods may be used as desired to manufacture the nozzle substrate 11.

[0046] M nozzles N are formed on the nozzle substrate 11. Here, the nozzles N are through-holes provided in the nozzle substrate 11. The surface NP of the nozzle substrate 11 in the Z1 direction corresponds to the nozzle surface. In this embodiment, it is assumed that the M nozzles N are arranged on the nozzle substrate 11 so as to extend in the Y-axis direction. Hereinafter, the M nozzles N extending in the Y-axis direction may be referred to as a nozzle row Ln.

[0047] 3 and 4, a communicating plate 12 is provided at a position in the Z2 direction relative to the nozzle substrate 11. The communicating plate 12 is a plate-shaped member that is long in the Y-axis direction and extends approximately parallel to the XY plane. The communicating plate 12 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology, but the communicating plate 12 may be manufactured using any known material and method.

[0048] 3 and 4, a pressure chamber substrate 13 is provided at a position in the Z2 direction relative 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 approximately parallel to the XY plane. The pressure chamber substrate 13 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology, but the pressure chamber substrate 13 may be manufactured using any known material and manufacturing method.

[0049] Ink flow paths are formed in the communication plate 12 and the pressure chamber substrate 13. Specifically, one common flow path BA1 extending in the Y-axis direction and one common flow path BA2 extending in the Y-axis direction are formed in the communication plate 12 and the pressure chamber substrate 13. The common flow path BA2 is located in the X1 direction relative to the common flow path BA1.

[0050] Furthermore, M connection flow paths BR1 corresponding to the M nozzles N are formed in the communication plate 12 and the pressure chamber substrate 13. Furthermore, M connection flow paths BR2 corresponding to the M nozzles N are formed in the communication plate 12 and the pressure chamber substrate 13. Furthermore, M nozzle flow paths BN corresponding to the M nozzles N are formed in the communication plate 12. Furthermore, M pressure chambers CV corresponding to the M nozzles N are formed in the pressure chamber substrate 13.

[0051] The connection flow path BR1 is provided at a position in the X1 direction relative to the common flow path BA1, extending in the X-axis direction, and communicating with the common flow path BA1. The connection flow path BR2 is provided at a position in the X2 direction relative to the common flow path BA2, extending in the X-axis direction, and communicating with the common flow path BA2. The pressure chamber CV is located between the connection flow path BR1 and the connection flow path BR2, and communicates with the connection flow path BR1 and the connection flow path BR2. The pressure chamber CV also communicates with the nozzle flow path BN. The nozzle flow path BN is also provided at a position in the Z1 direction relative to the pressure chamber CV, and communicates with the nozzle N.

[0052] In the following description, the common flow paths BA1 and BA2 may be collectively referred to as a common flow path BA, and the connection flow paths BR1 and BR2 may be collectively referred to as a connection flow path BR.

[0053] Furthermore, hereinafter, the connection flow path BR1, the pressure chamber CV communicating with the connection flow path BR1, and the connection flow path BR2 communicating with the pressure chamber CV may be referred to as an individual flow path RK. Furthermore, hereinafter, the individual flow path RK corresponding to the j-th nozzle N among the M nozzles N may be referred to as an individual flow path RK[j]. Note that, in this embodiment, the individual flow path RK[j] is defined to include the j-th nozzle N among the M nozzles N. That is, in this embodiment, the individual flow path RK[j] has the j-th nozzle N and a pressure chamber CV corresponding to the j-th nozzle N. Furthermore, in this embodiment, the M individual flow paths RK[1] to RK[M] corresponding to the M nozzles N are arranged along the Y-axis direction. Furthermore, in this embodiment, each individual flow path RK extends in the X-axis direction.

[0054] 4 illustrates an example in which the wall surfaces of the individual flow paths RK include surfaces SL1d, SL1u, SL2d, and SL2u that are inclined with respect to the YZ plane, but the wall surfaces of the individual flow paths RK are not limited to the shape illustrated in FIG. 4. For example, surfaces SL1d, SL1u, SL2d, and SL2u may be approximately parallel to the YZ plane. Furthermore, in the present embodiment, it is assumed, as an example, that the wall surfaces that define the ends of the individual flow paths RK in the Z1 direction are formed by the communicating plates 12, but the ends of the individual flow paths RK in the Z1 direction may be formed by the nozzle substrate 11.

[0055] As shown in FIGS. 3 and 4, a diaphragm 14 is provided at a position in the Z2 direction relative to the pressure chamber substrate 13. The diaphragm 14 includes a diaphragm CPZ, a vibration absorbing plate CP1, and a vibration absorbing plate CP2. Each of the diaphragm CPZ, the vibration absorbing plate CP1, and the vibration absorbing plate CP2 is a plate-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and is capable of elastically vibrating. Each of the diaphragm CPZ, the vibration absorbing plate CP1, and the vibration absorbing plate CP2 includes, for example, an elastic film made of silicon oxide and an insulating film made of zirconium oxide. Note that the elastic film included in each of the diaphragm CPZ, the vibration absorbing plate CP1, and the vibration absorbing plate CP2 is not limited to an elastic film made of silicon oxide. Similarly, the insulating film included in each of the diaphragm CPZ, the vibration absorbing plate CP1, and the vibration absorbing plate CP2 is not limited to an insulating film made of zirconium oxide.

[0056] The diaphragm CPZ is disposed in the Z2 direction relative to the pressure chambers CV. M piezoelectric elements PZ corresponding to the M pressure chambers CV are disposed on the Z2-direction surface of the diaphragm CPZ. Here, the first-direction surface of the first element is a surface of the first element that is approximately perpendicular to the first direction and is the surface that is visible when the first element is viewed from the first direction toward the second direction. The second direction is the direction opposite to the first direction. Furthermore, in this specification, the expression "a second element is formed on the surface of the first element" does not intend to be limited to a configuration in which the first element and the second element are in direct contact. In other words, even if a third element is formed on the surface of the first element and the second element is formed on the surface of the third element, the concept of "a second element is formed on the surface of the first element" is encompassed as long as at least a portion of the first element and the second element overlap in a planar view.

[0057] 3 and 4, the piezoelectric element PZ includes a common electrode Zd supplied with a predetermined bias potential VBS, an individual electrode Zu supplied with an individual drive signal Vin, and a piezoelectric layer Zm provided between the individual electrode Zu and the common electrode Zd, as shown in FIG. 6. For example, the common electrode Zd, the piezoelectric layer Zm, and the individual electrode Zu are provided in this order along the Z2 direction on the Z2-direction surface of the diaphragm CPZ. In this embodiment, the common electrode Zd is a so-called lower electrode, and the individual electrode Zu is a so-called upper electrode; however, the common electrode Zd may be the upper electrode and the individual electrode Zu may be the 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 described above, the piezoelectric element PZ is provided on the Z2-direction surface of the diaphragm CPZ, so the diaphragm CPZ vibrates in conjunction with the deformation of the piezoelectric element PZ. When the diaphragm CPZ vibrates, the pressure inside the pressure chamber CV fluctuates. This fluctuation in the pressure inside the pressure chamber CV causes the ink filled inside the pressure chamber CV to be ejected from the nozzle N in the Z1 direction via the nozzle flow path BN.

[0060] The vibration absorbing plate CP1 is provided at a position in the Z2 direction relative to the common flow path BA1. When ink flowing in the common flow path BA1 vibrates in response to pressure fluctuations in the pressure chambers CV, the vibration absorbing plate CP1 absorbs the vibrations. The vibration absorbing plate CP2 is provided at a position in the Z2 direction relative to the common flow path BA2. When ink flowing in the common flow path BA2 vibrates in response to pressure fluctuations in the pressure chambers CV, the vibration absorbing plate CP2 absorbs the vibrations. Hereinafter, the vibration absorbing plates CP1 and CP2 may be collectively referred to as vibration absorbing plates CP.

[0061] 3 and 4, a flow path forming substrate 16 is provided at a position in the Z2 direction relative to the pressure chamber substrate 13. The flow path forming substrate 16 is a plate-like member that is elongated in the Y-axis direction and extends approximately parallel to the XY plane. The flow path forming substrate 16 is formed, for example, by injection molding of a resin material, but the flow path forming substrate 16 may be manufactured using any known material and method.

[0062] Ink flow paths are formed in the flow path forming substrate 16. Specifically, as shown in FIG. 4, one common flow path BB1 and one common flow path BB2 are formed in the flow path forming substrate 16. The common flow path BB1 is provided at a position in the Z2 direction relative to the common flow path BA1 so as to extend in the Y-axis direction, and is connected to the common flow path BA1. The common flow path BB2 is provided at a position in the Z2 direction relative to the common flow path BA2 and at a position in the X1 direction relative to the common flow path BB1 so as to extend in the Y-axis direction, and is connected to the common flow path BA2. Note that hereinafter, the common flow path BB1 and the common flow path BB2 may be collectively referred to as the common flow path BB.

[0063] Hereinafter, the common flow path BA1 and the common flow path BB1 communicating with the common flow path BA1 may be referred to as the common flow path RC1. Also, below, the common flow path BA2 and the common flow path BB2 communicating with the common flow path BA2 may be referred to as the common flow path RC2. Also, below, the common flow paths RC1 and RC2 may be collectively referred to as the common flow path RC. Note that the common flow path RC1 is an example of a "common supply flow path," and the common flow path RC2 is an example of a "common discharge flow path."

[0064] The flow channel forming substrate 16 is provided with a connection port H1 communicating with the common flow channel BB1 and a connection port H2 communicating with the common flow channel BB2. A supply flow channel 61 is connected to the connection port H1, and a recovery flow channel 62 is connected to the connection port H2. For example, a pump 63 supplies ink from an ink container 60 to a common flow channel RC1 including the common flow channel BB1 via the supply flow channel 61 and the connection port H1. In this case, a pressure Pin applied to the common flow channel RC1 becomes a positive pressure higher than atmospheric pressure, for example. Note that a portion of the ink supplied to the common flow channel RC1 fills the pressure chamber CV via the connection flow channel BR1. Then, when the piezoelectric element PZ is driven by a drive signal COM, a portion of the ink filling the pressure chamber CV is ejected from the nozzle N via the nozzle flow channel BN. Also, a portion of the ink filling the pressure chamber CV is discharged to the common flow channel RC2 via the connection flow channel BR2.

[0065] For example, the pump 64 recovers a portion of the ink stored in the common flow channel RC2, which includes the common flow channel BB2, via the recovery flow channel 62 and the connection port H2, and supplies the recovered ink to the ink container 60. In this case, the pressure Pout applied to the common flow channel RC2 becomes, for example, a negative pressure lower than atmospheric pressure. In this way, the pressure Pin is a pressure for supplying ink to the common flow channel RC1, and the pressure Pout is a pressure for discharging ink from the common flow channel RC2. Note that the pressure Pout may be equal to or greater than atmospheric pressure as long as it is smaller than the pressure Pin. The pressure Pin is an example of a "first pressure," and the pressure Pout is an example of a "second pressure."

[0066] In the following, an increase in pressure Pin means, for example, an increase in the pressure that forces ink stored in the common flow channel RC1 toward the pressure chamber CV, i.e., an increase in the force for supplying ink to the common flow channel RC1. Furthermore, a decrease in pressure Pout means an increase in the difference with pressure Pin, i.e., an increase in the amount of pressure reduction applied to the common flow channel RC2. Therefore, a decrease in pressure Pout means an increase in the pressure that discharges ink stored in the common flow channel RC2 from the connection port H2, i.e., an increase in the force for discharging ink from the common flow channel RC2. Note that, when pressure Pout is a negative pressure, a decrease in pressure Pout means an increase in the absolute value of pressure Pout, and an increase in pressure Pout means a decrease in the absolute value of pressure Pout. For example, pump 63 functions as a pressurizing mechanism that pressurizes pressure Pin, and pump 64 functions as a depressurizing mechanism that depressurizes pressure Pout.

[0067] Here, for example, if the pressure Pout is greater than an appropriate pressure relative to the pressure Pin, there is a risk that ink will leak from the nozzle N, and if the pressure Pout is less than an appropriate pressure relative to the pressure Pin, there is a risk that ink will not be properly ejected from the nozzle N. For this reason, the pressure Pin and the pressure Pout are adjusted so that the ink ejection state is normal.

[0068] A through hole 16h is provided in the flow path forming substrate 16. When the flow path forming substrate 16 is viewed in the Z1 direction, the through hole 16h is located between the common flow path BB1 and the common flow path BB2, 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. The wiring substrate 17 is inserted into the through hole 16h.

[0069] 3 and 4, a wiring board 17 is mounted on the surface of the pressure chamber substrate 13 facing in the Z2 direction. The wiring board 17 is a component for electrically connecting the liquid ejection head 1 to the control unit 4. A flexible wiring board such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably used as the wiring board 17. As described above, electronic components EC including the switching circuit 18 and the detection circuit 19 are mounted on the wiring board 17.

[0070] As shown in FIGS. 3 and 4, a filter FL is formed on the pressure chamber substrate 13. The filter FL is a structure for capturing air bubbles in the ink in the common flow path BA1. For example, the filter FL is composed of multiple protrusions FT arranged in the Y-axis direction. Of the multiple protrusions FT, the filter FL captures air bubbles that rise in the Z2 direction due to buoyancy in the ink flowing in the common flow path BA1, using two of the multiple protrusions FT that are adjacent to each other in the Y-axis direction. Note that this embodiment assumes, as an example, a case in which the multiple protrusions FT are formed by the pressure chamber substrate 13. Also, this embodiment assumes, as an example, a case in which the multiple protrusions FT are attached to the Z1-direction surface of the flow path forming substrate 16.

[0071] In this embodiment, as described above, the filter FL is provided in the common flow path BA1, which makes it possible to prevent foreign matter from mixing into the ink ejected from the nozzles N. In this embodiment, the pump 64 recovers ink from the common flow path RC2, which makes it possible to prevent ink from flowing back from the common flow path BA2 to the nozzles N. Therefore, in this embodiment, even if the filter FL is not provided in the common flow path BA2, it is possible to prevent foreign matter from mixing into the ink ejected from the nozzles N. Furthermore, by not providing the filter FL in the common flow path BA2, it is possible to prevent the filter FL from limiting the flow of ink in the common flow path BA2. The filter FL is not limited to being composed of a plurality of protrusions FT arranged in the Y-axis direction.

[0072] As described above, in this embodiment, the filter FL is provided in only one of the first flow path between the pump 63 and the plurality of individual flow paths RK and the second flow path between the pump 64 and the plurality of individual flow paths RK. For example, the first flow path includes the common flow path RC1 and the supply flow path 61, and the second flow path includes the common flow path RC2 and the recovery flow path 62.

[0073] 4, the discharge section D includes a piezoelectric element PZ, a pressure chamber CV, and a nozzle N. In addition, the residual vibration of the discharge section D[j] described above is, more specifically, vibration remaining in the pressure chamber CV of the discharge section D[j].

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

[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 channel RC and the individual flow channels RK when the liquid ejection head 1 is viewed in a plane in the Z1 direction. However, for convenience of illustration, FIG. 5 depicts the supply flow channel 61 and the recovery flow channel 62 as extending in the X-axis direction, but the supply flow channel 61 and the recovery flow channel 62 do not necessarily extend in the X-axis direction. Also, FIG. 5 assumes, as an example, that the value M is "8." Also, FIG. 5 assumes that the connection port H1 and the connection port H2 are each located between the individual flow channel RK[4] and the individual flow channel RK[5] in the Y-axis direction.

[0076] When circulating ink, the supply flow channel 61 supplies ink to the common flow channel RC1, and the recovery flow channel 62 recovers ink from the common flow channel RC2. For example, in the common flow channel RC1, ink flows from the connection port H1 in the Y1 direction and the Y2 direction, as shown by arrows AR11 and AR12. The ink flowing in the Y1 direction from the connection port H1 is supplied to the individual flow channels RK[5] to RK[8], and the ink flowing in the Y2 direction from the connection port H1 is supplied to the individual flow channels RK[1] to RK[4].

[0077] In addition, in the individual flow path RK[j], as shown by the arrow FA[j], ink flows from the common flow path RC1 to the common flow path RC2 in the X1 direction, thereby filling, for example, the pressure chamber CV provided in the individual flow path RK[j] with ink.

[0078] Furthermore, for example, in the common flow channel RC2, as indicated by arrows AR21 and AR22, ink flows from the individual flow channels RK[1] to RK[4] in the Y1 direction, and ink flows from the individual flow channels RK[5] to RK[8] in the Y2 direction. That is, ink discharged from the individual flow channels RK[1] to RK[4] flows in the Y1 direction and is recovered into the recovery flow channel 62 via the connection port H2. Furthermore, ink discharged from the individual flow channels RK[5] to RK[8] flows in the Y2 direction and is recovered into the recovery flow channel 62 via the connection port H2. Hereinafter, the portion of the individual flow channel RK[j] between the common flow channel RC1 and the nozzle N may be referred to as the individual flow channel RKin[j], and the portion between the nozzle N and the common flow channel RC2 may be referred to as the individual flow channel RKout[j].

[0079] In this way, the common flow path RC1 is commonly connected to the multiple individual flow paths RK and supplies ink to the multiple individual flow paths RK. Furthermore, the common flow path RC2 is commonly connected to the multiple individual flow paths RK and discharges ink from the multiple individual flow paths RK. Note that this embodiment assumes that ink is circulated as shown in FIG. 5 during the recovery process for restoring the ejection state of the nozzles N to a normal state, and during the printing process for forming an image indicated by print data IMG on a medium.

[0080] Furthermore, in this embodiment, as described above, the connection port H1 is provided between the individual flow path RK[4] and the individual flow path RK[5] in the Y-axis direction. That is, in this embodiment, the connection port H1 is provided between the individual flow path RK[1] and the individual flow path RK[M] in the Y-axis direction. Therefore, in this embodiment, the pressure Pin required to supply ink from the connection port H1 to the M individual flow paths RK can be reduced compared to an embodiment in which the connection port H1 is provided further in the Y2 direction than the individual flow path RK[1] and an embodiment in which the connection port H1 is provided further in the Y1 direction than the individual flow path RK[M]. As a result, in this embodiment, the power required to drive the circulation mechanism 6 can be reduced.

[0081] Furthermore, in this embodiment, a connection port H1 is provided between the individual flow channels RK[1] and RK[M] in the Y-axis direction, and a connection port H2 is provided between the individual flow channels RK[1] and RK[M]. Therefore, in this embodiment, it is possible to suppress ink stagnation in the common flow channel RC1 without providing multiple connection ports H1 connected to the common flow channel RC1, and it is also possible to suppress ink stagnation in the common flow channel RC2 without providing multiple connection ports H2 connected to the common flow channel RC2. As a result, in this embodiment, it is possible to suppress ink stagnation in the common flow channels RC1 and RC2 with a simpler configuration than in an embodiment in which multiple connection ports H1 connected to the common flow channel RC1 are provided and in an embodiment in which multiple connection ports H2 connected to the common flow channel RC2 are provided.

[0082] Next, an overview of the liquid ejection head 1 will be described with reference to FIG.

[0083] FIG. 6 is a block diagram showing an example of the configuration of the liquid ejection head 1. As shown in FIG.

[0084] 1, the liquid ejection head 1 has 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 Ls for supplying a detection signal Vout to the detection circuit 19. The liquid ejection head 1 also has a wiring Li[j] that supplies an individual drive signal Vin[j] to the ejection section D[j], and a wiring Ld to which a bias potential VBS is supplied.

[0085] The switching circuit 18 includes M switches SWa[1] to SWa[M] that correspond one-to-one to the M discharge sections D[1] to D[M], M switches SWb[1] to SWb[M] that correspond one-to-one to the M discharge sections D[1] to D[M], and M switches SWs[1] to SWs[M] that correspond one-to-one to the M discharge sections D[1] to D[M]. The switching circuit 18 also includes a connection state designation circuit CSC. The connection state designation circuit CSC designates the connection states of the M switches SWa, M switches SWb, and M switches SWs. For example, the connection state designation circuit CSC generates connection state designation signals Qa[j], Qb[j], and Qs[j] based on at least some of the print signal SI, latch signal LAT, change signal CH, and period designation signal Tsig supplied from the control unit 4. The connection state designation signal Qa[j] is a signal that designates whether the switch SWa[j] is on or off, the connection state designation signal Qb[j] is a signal that designates whether the switch SWb[j] is on or off, and the connection state designation signal Qs[j] is a signal that designates whether the switch SWs[j] is on or off.

[0086] The switch SWa[j] switches between conduction and non-conduction between the wiring La and the individual electrode Zu[j] of the piezoelectric element PZ[j] provided in the discharge section D[j] based on the connection state designation signal Qa[j]. That is, the switch SWa[j] switches between conduction and non-conduction between the wiring La and the wiring Li[j] connected to the individual electrode Zu[j] based on the connection state designation signal Qa[j]. In this embodiment, the switch SWa[j] is turned on when the connection state designation signal Qa[j] is high level and turned off when the connection state designation signal Qa[j] is low level. When the switch SWa[j] is on, the drive signal COMa supplied to the wiring La is supplied as the individual drive signal Vin[j] to the individual electrode Zu[j] of the discharge section D[j] via the wiring Li[j].

[0087] The switch SWb[j] switches between electrical continuity and non-conduction between the wiring Lb and the individual electrode Zu[j] of the piezoelectric element PZ[j] provided in the discharge section D[j] based on the connection state designation signal Qb[j]. That is, the switch SWb[j] switches between electrical continuity and non-conduction between the wiring Lb and the wiring Li[j] connected to the individual electrode Zu[j] based on the connection state designation signal Qb[j]. In this embodiment, the switch SWb[j] is turned on when the connection state designation signal Qb[j] is at a high level and turned off when the connection state designation signal Qb[j] is at a low level. When the switch SWb[j] is turned on, the drive signal COMb supplied to the wiring Lb is supplied as an individual drive signal Vin[j] to the individual electrode Zu[j] of the discharge section D[j] via the wiring Li[j].

[0088] The switch SWs[j] switches between electrical continuity and non-conduction between the wiring Ls and the individual electrode Zu[j] of the piezoelectric element PZ[j] provided in the discharge portion D[j] based on the connection state designation signal Qs[j]. That is, the switch SWs[j] switches between electrical continuity and non-conduction between the wiring Ls and the wiring Li[j] connected to the individual electrode Zu[j] based on the connection state designation signal Qs[j]. In this embodiment, the switch SWs[j] is turned on when the connection state designation signal Qs[j] is high level and turned off when the connection state designation signal Qs[j] is low level.

[0089] For example, the connection state designation signal Qs[j] becomes high when detecting residual vibration of the pressure chamber CV of the discharge section D[j]. Hereinafter, the pressure chamber CV whose residual vibration is to be detected may be simply referred to as the pressure chamber CV of the detection target. Also, hereinafter, the discharge section D including the pressure chamber CV of the detection target may be simply referred to as the discharge section D of the detection target.

[0090] When the connection state designation signal Qs[j] becomes high level, the switch SWs[j] turns on, and a detection signal Vout[j] indicating the potential of the individual electrode Zu[j] of the discharge section D[j] to be detected is supplied to the detection circuit 19 via the wiring Li[j] and the wiring Ls. The detection circuit 19 generates a residual vibration signal Vd[j] based on the detection signal Vout[j].

[0091] As described above, the individual drive signal Vin[j] is the signal of the drive signals COMa and COMb that is supplied to the piezoelectric element PZ[j] of the discharge section D[j] via the switch SWa[j] or SWb[j].

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

[0093] 7 is a timing chart showing an example of the operation of the liquid ejection device 100 in a unit period Tu. In this embodiment, when the liquid ejection device 100 executes a printing process, a printing process period including one or more unit periods Tu is set as the operating period of the liquid ejection device 100. The liquid ejection device 100 according to this embodiment can drive each ejection section D for the printing process in each unit period Tu. Furthermore, the liquid ejection device 100 according to this embodiment can drive the ejection section D to be detected and detect the detection signal Vout[j] from the ejection section 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. As a result, the control unit 4 defines a unit period Tu as the period from the rising edge of a pulse PlsL to the rising edge of the next pulse PlsL. The control unit 4 also divides the unit period Tu into two control periods Tu1 and Tu2 using 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 sections D[1] to D[M]. The individual designation signal Sd[j] designates the driving mode of the discharge section D[j] in each unit period Tu when the liquid discharger 100 executes a printing process.

[0096] Prior to each unit period Tu during which printing is performed, 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 the clock signal CL. Then, during that unit period Tu, the connection state designation circuit CSC generates connection state designation signals Qa[j], Qb[j], and Qs[j] based on the individual designation signal Sd[j].

[0097] In this embodiment, it is assumed that the ejection unit D[j] can form any of large dots, medium dots that are smaller than large dots, and small dots that are smaller than medium dots in the unit period Tu. Hereinafter, the amount of ink equivalent to a large dot will be referred to as a large amount of ink, the amount of ink equivalent to a medium dot will be referred to as a medium amount of ink, and the amount of ink equivalent to a small dot will be referred to as a small amount of ink.

[0098] For example, the individual designation signal Sd[j] is a signal that designates one of five drive modes for the discharge section D[j] in each unit period Tu: discharge of a large amount of ink, discharge of a medium amount of ink, discharge of a small amount of ink, no ink discharge, and drive as the discharge section D to be detected. For example, if the individual designation signal Sd[j] is a 3-bit digital signal, one of the five drive modes can be designated by the individual designation signal Sd[j]. Note that the individual designation signal Sd[j] may also be a 4-bit or more digital signal.

[0099] 7, the drive signal generating unit 2 outputs a drive signal COMa having a pulse PX and a pulse 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.

[0100] In this embodiment, the pulses PX and PY are determined so 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 the ejection section D[j] is driven by the drive signal COMa having the pulse PX, the waveform of the pulse PX is determined so that a medium amount of ink is ejected from the ejection section D[j]. Furthermore, when the ejection section D[j] is driven by the drive signal COMa having the pulse PY, the waveform of the pulse PY is determined so that a small amount of ink is ejected from the ejection section D[j]. The potentials of the pulses PX and PY at the start and end are set to the reference potential V0.

[0101] When the individual designation signal Sd[j] instructs the discharge unit D[j] to form a large dot, the connection state designation circuit CSC sets the connection state designation signal Qa[j] to a high level during the control periods Tu1 and Tu2, and sets the connection state designation signals Qb[j] and Qs[j] to a low level during the unit period Tu. In this case, the discharge unit D[j] is driven by the pulse PX of the drive signal COMa during the control period Tu1 to discharge a medium amount of ink, and is driven by the pulse PY of the drive signal COMa during the control period Tu2 to discharge a small amount of ink. As a result, the discharge unit D[j] discharges a large amount of ink in total during the unit period Tu, forming a large dot on the medium PP.

[0102] Furthermore, when the individual designation signal Sd[j] designates the ejection unit D[j] to form a medium dot, the connection state designation circuit CSC sets the connection state designation signal Qa[j] to a high level during control period Tu1 and to a low level during control period Tu2, and sets the connection state designation signals Qb[j] and Qs[j] to a low level during unit period Tu. In this case, the ejection unit D[j] ejects a medium amount of ink during unit period Tu, and a medium dot is formed on the medium PP.

[0103] Furthermore, when the individual designation signal Sd[j] designates the ejection section D[j] to form a small dot, the connection state designation circuit CSC sets the connection state designation signal Qa[j] to a low level during the control period Tu1 and to a high level during the control period Tu2, and sets the connection state designation signals Qb[j] and Qs[j] to a low level during the unit period Tu. In this case, the ejection section D[j] ejects a small amount of ink during the unit period Tu, and a small dot is formed on the medium PP.

[0104] Furthermore, when the individual designation signal Sd[j] designates the discharge unit D[j] not to discharge ink, the connection state designation circuit CSC sets the connection state designation signals Qa[j], Qb[j], and Qs[j] to a low level during the unit period Tu. In this case, the discharge unit D[j] does not discharge ink during the unit period Tu, and does not form dots on the medium PP.

[0105] The drive signal generating unit 2 also outputs a drive signal COMb having a pulse PS. The waveform of the drive signal COMb during the unit period Tu corresponds to the pulse PS. In this embodiment, the pulse PS is determined so 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 the drive signal COMb having the pulse PS is supplied to the ejection section D[j], the waveform of the pulse PS is determined so that the ejection section D[j] is driven to such an extent that ink is not ejected from the ejection section D[j]. The potential of the pulse PS at the start and end is set to the reference potential V0.

[0106] The control unit 4 also outputs a period defining signal Tsig having a pulse PlsT1 and a pulse PlsT2, thereby dividing 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.

[0107] When the individual designation signal Sd[j] designates the emission section D[j] as the emission section D to be detected, the connection state designation circuit CSC sets the connection state designation signal Qa[j] to a low level in the unit period Tu, sets the connection state designation signal Qb[j] to a high level in the control periods TSS1 and TSS3 and to a low level in the control period TSS2, and sets the connection state designation signal Qs[j] to a low level in the control periods TSS1 and TSS3 and to a high level in the control period TSS2.

[0108] In this case, the ejection section D to be detected is driven by the pulse PS of the drive signal COMb during the control period TSS1. Specifically, the piezoelectric element PZ of the ejection section D to be detected is displaced by the pulse PS of the drive signal COMb during the control period TSS1. As a result, vibration occurs in the ejection section D to be detected. The vibration that occurred during the control period TSS1 remains during the control period TSS2. Then, during the control period TSS2, the potential of the individual electrode Zu of the piezoelectric element PZ of the ejection section D to be detected changes according to the residual vibration occurring in the ejection section D to be detected. That is, during the control period TSS2, the potential of the individual electrode Zu of the piezoelectric element PZ of the ejection section D to be detected becomes a potential according to the electromotive force of the piezoelectric element PZ caused by the residual vibration occurring in the ejection section D to be detected. Then, the potential of the individual electrode Zu is detected as the detection signal Vout during the control period TSS2.

[0109] 7 illustrates an example in which the detection signal Vout indicating the residual vibration of the ejection section D to be detected is generated during the printing process period, but the detection signal Vout indicating the residual vibration of the ejection section D to be detected may be generated during a period other than the printing process period. In other words, a process of detecting the residual vibration of the ejection section D to be detected may be executed during a period other than the printing process period.

[0110] The operation of the liquid ejection device 100 is not limited to the example shown in FIG. 7. For example, while FIG. 7 illustrates a case where the dots that can be formed on the medium PP are of three sizes, large, medium, and small, the dots that can be formed on the medium PP are not limited to three sizes. Specifically, the dots that can be formed on the medium PP may be of one size or two sizes. Furthermore, the multiple drive signals COM may include drive signals COM other than drive signals COMa and COMb. For example, the multiple drive signals COM may include a drive signal COM having a micro-vibration waveform that applies micro-vibrations to the ink inside the ejection section D to prevent the ink from thickening.

[0111] Next, an outline of the operation of the circulation control unit 40 will be described with reference to FIG.

[0112] FIG. 8 is an explanatory diagram for explaining an outline of the operation of the circulation control unit 40. FIG. 8 shows a graph for explaining the relationship between the flow rate of ink and the flow path resistance, and an equivalent circuit, which is an equivalent circuit diagram of the flow paths provided in the liquid ejection head 1. The dashed arrows in the equivalent circuit of FIG. 8 indicate the flow of ink. In the graph of FIG. 8, the horizontal axis indicates the flow rate of ink, and the vertical axis indicates the flow path resistance. The flow path resistance Rin is, for example, the flow path resistance of the flow path from the connection port H1 to M nozzles N. The flow path from the connection port H1 to the nozzle N includes, for example, a common flow path RC1 and an individual flow path RKin. The flow path resistance Rout is, for example, the flow path resistance of the flow path from the nozzle N to the connection port H2. The flow path from the nozzle N to the connection port H2 includes, for example, a common flow path RC1 and an individual flow path RKout. As described in FIG. 5, the individual flow path RKin is the portion of the individual flow path RK between the common flow path RC1 and the nozzle N. The individual flow path RKin is the portion of the individual flow path RK between the nozzle N and the common flow path RC2.

[0113] The circulation control unit 40 adjusts the pressure Pn near the nozzle N to an appropriate pressure by controlling the pumps 63 and 64. However, in this embodiment, as described above, the filter FL is provided only in the common flow path RC1 of the common flow paths RC1 and RC2, and therefore, in order to adjust the pressure Pn to an appropriate pressure, it is necessary to take into consideration the flow path resistances Rin and Rout.

[0114] Generally, flow path resistance R is expressed by equation (1) using constants A and B determined by the shape of the flow path, ink viscosity μ, ink mass m, and ink flow rate F. Note that "*" in equation (1) indicates multiplication, and "^" in equation (1) indicates exponentiation. R=A*μ*F+B*m*F^2 …(1)

[0115] Of the flow path resistance R, "A*μ*F" in formula (1) corresponds to the resistance determined according to the ink viscosity μ, i.e., viscous resistance. Also, of the flow path resistance R, "B*m*F^2" in formula (1) corresponds to the resistance dependent on the shape of the flow path, i.e., inertial resistance.

[0116] Here, because the common flow path RC1 is provided with a filter FL, viscous resistance is more dominant than inertial resistance in the flow path resistance Rin of the flow paths including the common flow path RC1. Therefore, in equation (1), inertial resistance can be ignored and the flow path resistance Rin can be approximated. That is, the flow path resistance Rin can be expressed by equation (2), for example, using a constant Ain determined by the shape of the flow path from the connection port H1 to the nozzle N, the viscosity μ of the ink, and the flow rate F of the ink. Rin=Ain*μ*F …(2)

[0117] On the other hand, because the common flow path RC2 is provided with a filter FL, both viscous resistance and inertial resistance act on the flow path resistance Rout of the flow path including the common flow path RC2. For this reason, the flow path resistance Rout can be expressed by, for example, equation (3) using constants Aout and Bout determined by the shape of the flow path from the nozzle N to the connection port H2, the viscosity μ of the ink, the mass m of the ink, and the flow rate F of the ink. Rout=Aout*μ*F+Bout*m*F^2 …(3)

[0118] As can be seen from equations (2) and (3), the values of the flow path resistances Rin and Rout and the balance between the flow path resistances Rin and Rout change depending on the flow rate F. The balance between the flow path resistances Rin and Rout is, for example, the ratio or difference between the flow path resistances Rin and Rout. As shown in the graph of FIG. 8, for example, the balance between the flow path resistances Rin1 and Rout1 when the flow rate F is flow rate F1 is different from the balance between the flow path resistances Rin2 and Rout2 when the flow rate F is flow rate F2.

[0119] Thus, in this embodiment, at one of the flow path resistances R of the common flow paths RC1 and RC2, for example, flow path resistance Rin, the viscous resistance is greater than the inertial resistance, and at the other of the flow path resistances R of the common flow paths RC1 and RC2, for example, flow path resistance Rout, the inertial resistance is greater than the viscous resistance.

[0120] 8, the pressure Pn near the nozzle N is expressed using the flow path resistances Rin and Rout and the pressures Pin and Pout. For example, the ink flow velocity is expressed by equation (4) using the flow path resistances Rin and Rout and the pressures Pin, Pout, and Pn. Then, equation (5) expressing the pressure Pn is derived from equation (4). Flow rate=(Pin-Pn) / Rin=(Pn-Pout) / Rout …(4) Pn=(Pin*Rout+Pout*Rin) / (Rin+Rout) …(5)

[0121] Here, for example, if the same filter FL is provided in both the flow path from connection port H1 to nozzle N and the flow path from connection port H2 to nozzle N, or if the filter FL is not provided in both flow paths and the shapes of the flow paths are the same, ideally, the flow path resistances Rin and Rout will be equal to each other. In this case, if "Rin = Rout" is substituted into equation (5), "Rin" and "Rout" disappear from equation (5), and the pressure Pn is expressed as "(Pin + Pout) / 2". Therefore, in the above example in which the flow path resistances Rin and Rout are equal to each other, the pressures Pin and Pout that make the pressure Pn appropriate can be determined based on the equation "Pn = (Pin + Pout) / 2," i.e., an equation that does not include the flow path resistances Rin and Rout.

[0122] However, in this embodiment, because the filter FL is provided only in the common flow path RC1 of the two common flow paths RC1 and RC2, the change in flow path resistance R according to the ink viscosity μ differs between the common flow paths RC1 and RC2. Specifically, when focusing on the flow rate F, as shown in equations (2) and (3), the flow path resistance Rin is a linear equation, and the flow path resistance Rout is a quadratic equation. Therefore, "Rin" and "Rout" in equation (5) do not disappear from equation (5). Therefore, in the configuration of this embodiment, if the pressures Pin and Pout are adjusted without considering the flow path resistances Rin and Rout, it is difficult to adjust the pressure Pn near the nozzle N to an appropriate pressure. For this reason, in this embodiment, the circulation control unit 40 adjusts the pressure Pn to an appropriate pressure by adjusting the pressures Pin and Pout while taking into account the flow path resistances Rin and Rout.

[0123] For example, in equation (1) representing the flow path resistance R, constants A and B are constants determined by the shape of the flow path, and therefore are known values to the head manufacturer that produces the liquid ejection head 1. Furthermore, the ink mass m is determined by the ink used, and is therefore a coefficient whose value can be known in advance by manufacturers, etc. that use the liquid ejection head 1. Furthermore, the ink flow rate F can be adjusted to a desired value using a flow meter or the like. Therefore, when the ink flow rate F is adjusted to a desired value, the only variable in equation (1) representing the flow path resistance R is the ink viscosity μ. In other words, by determining the ink viscosity μ, the flow path resistances Rin and Rout can be calculated from equations (2) and (3). Furthermore, by using the flow path resistances Rin and Rout calculated based on the ink viscosity μ, the pressures Pin and Pout required to adjust the pressure Pn near the nozzle N to an appropriate pressure can be calculated from equation (5).

[0124] In this embodiment, the circulation control unit 40 determines the pressures Pin and Pout for making the pressure Pn near the nozzle N an appropriate pressure, for example, by using the flow path resistances Rin and Rout calculated based on the viscosity μ estimated by the viscosity estimation unit 3. Note that since the viscosity μ is estimated based on residual vibration, determining the pressures Pin and Pout using the flow path resistances Rin and Rout calculated based on the viscosity μ corresponds to determining the pressures Pin and Pout based on residual vibration.

[0125] Next, the operation of the liquid ejection device 100 will be described with reference to FIG.

[0126] Fig. 9 is a flowchart showing an example of the operation of the liquid ejection device 100. Note that Fig. 9 mainly explains the operation of the circulation control unit 40 that determines the pressures Pin and Pout.

[0127] First, in step S100, the control unit 4 functions as the circulation control unit 40 and causes the detection circuit 19 to detect residual vibration. Specifically, the circulation control unit 40 outputs an individual designation signal Sd that designates one of the M discharge units D as the discharge unit D to be detected to the connection state designation circuit CSC. As a result, the detection circuit 19 acquires a detection signal Vout that indicates the residual vibration of the discharge unit D to be detected, and outputs a residual vibration signal Vd generated based on the detection signal Vout to the viscosity estimation unit 3.

[0128] Next, in step S120, the control unit 4 functions as the circulation control unit 40 and acquires viscosity information Vinf indicating the viscosity μ of the ink from the viscosity estimation unit 3. For example, the viscosity estimation unit 3 estimates the viscosity μ of the ink based on the residual vibration signal Vd supplied from the detection circuit 19 by the processing of step S100. The viscosity estimation unit 3 then outputs the viscosity information Vinf indicating the viscosity of the ink estimated based on the residual vibration signal Vd to the control unit 4. As a result, the circulation control unit 40 acquires the viscosity information Vinf indicating the viscosity of the ink estimated based on the residual vibration signal Vd.

[0129] Next, in step S140, the control unit 4 functions as the circulation control unit 40 and determines the pressure Pin for supplying ink to the common flow path RC1 and the pressure Pout for discharging ink from the common flow path RC2 based on the viscosity information Vinf. Specifically, the circulation control unit 40 determines the pressure values of the pressures Pin and Pout to make the pressure Pn near the nozzle N an appropriate pressure based on the viscosity μ indicated by the viscosity information Vinf and the above-mentioned equations (2), (3), and (5). Note that the determination of the pressures Pin and Pout is not limited to determining the pressure values themselves. For example, the determination of the pressures Pin and Pout also includes determining how much to increase or decrease the pressures Pin and Pout from the current pressures.

[0130] Furthermore, when there are multiple candidate combinations of the pressures Pin and Pout calculated based on the viscosity μ indicated by the viscosity information Vinf and the above-described formulas (2), (3), and (5), the circulation control unit 40 selects one of the multiple candidates. For example, assume that "Pn = C*Pin + D*Pout" and "C = 1, D = 2" are derived from the viscosity μ indicated by the viscosity information Vinf and the above-described formulas (2), (3), and (5). Furthermore, assume that the pressure Pn is set to 10. In this case, multiple candidates are calculated, such as "(Pin, Pout) = (30, -10)," "(Pin, Pout) = (50, -20)," and "(Pin, Pout) = (2, 4)."

[0131] Typically, the pressure Pin is a positive pressure and the pressure Pout is a negative pressure. For this reason, for example, the circulation control unit 40 does not adopt the candidate "(Pin, Pout) = (2, 4)." Also, since "(Pin, Pout) = (30, -10)" and "(Pin, Pout) = (50, -20)" are both combinations of positive and negative pressures, the circulation control unit 40 determines the combination of the pressures Pin and Pout based on, for example, whether or not to increase the ink flow rate.

[0132] For example, when "(Pin, Pout) = (30, -10)", the difference between the pressures Pin and Pout is 40, and when "(Pin, Pout) = (50, -20)", the difference between the pressures Pin and Pout is 70. When the difference between the pressures Pin and Pout is large, the ink flow rate is greater than when the difference between the pressures Pin and Pout is small. When it is desired to suppress an increase in the circulating flow rate of ink, the circulation control unit 40 selects the combination "(Pin, Pout) = (30, -10)". Note that the combination "(Pin, Pout) = (30, -10)" has smaller absolute values of both the pressure Pin and the pressure Pout than the combination "(Pin, Pout) = (50, -20)", and therefore the load on the pumps 63 and 64 can be reduced. Furthermore, when prioritizing the elimination of ink viscosity through circulation, the circulation control unit 40 increases the ink circulation flow rate by selecting the combination "(Pin, Pout)=(50, -20)".

[0133] Furthermore, the circulation control unit 40 may present multiple candidate combinations of pressures Pin and Pout to the user and acquire selection information indicating a candidate selected by the user from among the candidates presented to the user. The circulation control unit 40 may then select, from the multiple candidates, a candidate indicated by the selection information as the combination of pressures Pin and Pout. The circulation control unit 40 may present some of the multiple candidate combinations of pressures Pin and Pout to the user. For example, if the multiple candidates include a candidate in which the pressure Pout is a positive pressure or a candidate in which the pressure Pin is a negative pressure, the circulation control unit 40 may present to the user candidates other than the candidate in which the pressure Pout is a positive pressure or a candidate in which the pressure Pin is a negative pressure. In the above example, the circulation control unit 40 may present to the user, from the three candidates, the candidates "(Pin, Pout) = (50, -20)" and "(Pin, Pout) = (30, -10)" excluding "(Pin, Pout) = (2, 4)". The circulation control unit 40 may present all three candidates to the user, but may also present them by recommending "(Pin, Pout) = (50, -20)." Note that the "presentation" mentioned here can be any method that can convey the candidates to the user, but one example is to visibly display information indicating the candidates on the display of the user's computer.

[0134] As described above, in this embodiment, the circulation control unit 40 determines the pressure Pin and the pressure Pout to make the pressure Pn appropriate, based on the ink viscosity μ estimated based on the residual vibration detected by the detection circuit 19. As a result, in this embodiment, the pressure Pn can be adjusted more appropriately than in a comparative example in which the pressure Pin and the pressure Pout are determined without using the residual vibration. A comparative example in which the pressure Pin and the pressure Pout are determined without using the residual vibration is, for example, an embodiment in which the pressures Pin and Pout are determined based on the above-mentioned formula "Pn = (Pin + Pout) / 2," i.e., a formula that does not include the flow path resistances Rin and Rout.

[0135] As described above, in this embodiment, the liquid ejection device 100 includes a piezoelectric element PZ, a plurality of individual flow channels RK each including a nozzle N and a pressure chamber CV, a common flow channel RC1 that communicates with the plurality of individual flow channels RK in common and supplies ink to the plurality of individual flow channels RK, a common flow channel RC2 that communicates with the plurality of individual flow channels RK in common and discharges ink from the plurality of individual flow channels RK, a pump 63 that applies a pressure Pin to the common flow channel RC1 for supplying ink to the common flow channel RC1, a pump 64 that applies a pressure Pout to the common flow channel RC2 for discharging ink from the common flow channel RC2, a detection circuit 19 that detects residual vibration in the pressure chamber CV after applying a voltage to the piezoelectric element PZ, and a circulation control unit 40 that determines the pressure Pin and the pressure Pout based on the residual vibration detected by the detection circuit 19. For example, a control program PG of the liquid ejection device 100 causes the control unit 4 to function as the circulation control unit 40.

[0136] As described above, in this embodiment, the circulation control unit 40 determines the pressure Pin and the pressure Pout based on the residual vibration detected by the detection circuit 19. As a result, in this embodiment, the pressure Pin and the pressure Pout for making the pressure Pn near the nozzle N an appropriate pressure can be determined with high accuracy compared to a comparative example in which the pressure Pin and the pressure Pout are determined without using the residual vibration. As a result, in this embodiment, the pressure Pn near the nozzle N can be appropriately adjusted.

[0137] Furthermore, in this embodiment, the change in flow path resistance R according to the viscosity μ of the ink differs between the common flow path RC1 and the common flow path RC2. Even in this case, in this embodiment, the pressure Pin and the pressure Pout are each determined based on the residual vibration, so the pressure Pn near the nozzle N can be appropriately adjusted. That is, in this embodiment, the pressure Pn near the nozzle N can be appropriately adjusted even for a liquid ejection head 1 in which the change in flow path resistance R according to the viscosity μ of the ink differs between the common flow path RC1 and the common flow path RC2.

[0138] Furthermore, in this embodiment, the viscous resistance is greater than the inertial resistance at the flow path resistance R of one of the common flow paths RC1 and RC2, and the inertial resistance is greater than the viscous resistance at the flow path resistance R of the other of the common flow paths RC1 and RC2. Even in this case, in this embodiment, the pressures Pin and Pout are each determined based on the residual vibration, so the pressure Pn near the nozzle N can be appropriately adjusted. That is, in this embodiment, the pressure Pn near the nozzle N can be appropriately adjusted even for a liquid ejection head 1 in which the viscous resistance is greater than the inertial resistance at the flow path resistance R of one of the common flow paths RC1 and RC2, and the inertial resistance is greater than the viscous resistance at the flow path resistance R of the other.

[0139] Furthermore, in this embodiment, a filter FL is provided in only one of the first flow path between the pump 63 and the multiple individual flow paths RK and the second flow path between the pump 64 and the multiple individual flow paths RK. The first flow path includes a common flow path RC1, and the second flow path includes a common flow path RC2. Even when a filter FL is provided in only one of the first flow path and the second flow path, in this embodiment, the pressures Pin and Pout are each determined based on residual vibration, so that the pressure Pn near the nozzle N can be appropriately adjusted. In other words, in this embodiment, the pressure Pn near the nozzle N can be appropriately adjusted even for a liquid ejection head 1 in which a filter FL is provided in only one of the first flow path and the second flow path.

[0140] In addition, in this embodiment, the only flow paths that connect the common flow path RC1 and the common flow path RC2 are the multiple individual flow paths RK. In this case, since there are no flow paths that connect the common flow path RC1 and the common flow path RC2 other than the multiple individual flow paths RK, it is possible to prevent the calculation of the flow path resistances Rin and Rout according to the viscosity μ from becoming complicated.

[0141] Furthermore, in this embodiment, the circulation control unit 40 may calculate candidate combinations of the pressure Pin and the pressure Pout based on the residual vibration detected by the detection circuit 19 and present the candidates to the user. The circulation control unit 40 may then acquire selection information indicating a candidate selected by the user from the candidates presented to the user and determine the pressure Pin and the pressure Pout based on the selection information. In this case, the user can select a combination of the pressure Pin and the pressure Pout, making it possible to appropriately determine a combination of the pressure Pin and the pressure Pout for adjusting the pressure Pn near the nozzle N to an appropriate pressure. Note that the user only needs to select one candidate from the candidates presented by the circulation control unit 40. This, for example, can simplify the user's work of adjusting the pressure Pn to an appropriate pressure.

[0142] In addition, in this embodiment, when presenting candidates to the user, the circulation control unit 40 may recommend some of the candidates. In this case, the recommended candidates are combinations of pressure Pin and pressure Pout determined based on the residual vibration and are also realistic for other reasons. Conversely, candidates that are not recommended are combinations of pressure Pin and pressure Pout determined based on the residual vibration but are unrealistic for other reasons. As a result, it is possible to prevent the user from selecting unrealistic combinations of pressure Pin and pressure Pout. Examples of candidate combinations of unrealistic pressure Pin and pressure Pout include a candidate where the pressure Pout is a positive pressure or a negative pressure, and a candidate where the pressure Pin exceeds the capacity of the pump 63 or a candidate where the pressure Pout exceeds the capacity of the pump 64. Note that the recommendation referred to here refers to a presentation method in which some of the candidates are preferentially selected over the other candidates. For example, the recommendation candidates may be highlighted by changing the display color, enlarging the display size, etc., so that they are easier for the user to see. Furthermore, for example, when a screen is presented on the user's display that displays multiple candidates so that the user can select them by moving a cursor or the like, the default (initial) position of the cursor or the like may be set to the recommendation candidate.

[0143] [2. Modifications] Each of the above embodiments can be modified in various ways. Specific modified embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within a range that does not contradict each other. In the modified examples exemplified below, elements whose actions and functions are equivalent to those of the embodiments will be designated by the same reference numerals as in the above description, and detailed descriptions of each will be omitted as appropriate.

[0144] [First Modification] In the above-described embodiment and modified example, the case where the only flow paths that connect the common flow path RC1 and the common flow path RC2 are the multiple individual flow paths RK has been illustrated, but the present invention is not limited to such an embodiment. For example, as shown in Fig. 10, the liquid ejection device 100 may further include bypass flow paths BP1 and BP2 that are separate from the multiple individual flow paths RK and that connect the common flow path RC1 and the common flow path RC2.

[0145] FIG. 10 is an exploded perspective view showing an example of the configuration of a liquid ejection head 1 according to a first modified example. FIG. 11 is a cross-sectional view showing an example of the configuration of the liquid ejection head 1 shown in FIG. 10. The cross-sectional view shown in FIG. 11 is a cross-sectional view taken along line III-III shown in FIG. 10. The cross-section taken along line III-III is parallel to the XZ plane and passes through a bypass flow path BP1, which will be described later. Elements similar to those described in FIGS. 1 to 9 are denoted by the same reference numerals, and detailed description thereof will be omitted. The liquid ejection head 1 according to this aspect is similar to the liquid ejection head 1 according to the above-described embodiment, except that it is provided with bypass flow paths BP1 and BP2. The description in FIGS. 10 and 11 will focus on the bypass flow paths BP1 and BP2.

[0146] 10 and 11, the communicating plate 12 is formed with one bypass flow path BP1 connecting the common flow paths BA1 and BA2, and one bypass flow path BP2 connecting the common flow paths BA1 and BA2 at a position in the Y1 direction relative to the bypass flow path BP1. Each of the bypass flow paths BP1 and BP2 extends in the X-axis direction. Hereinafter, the bypass flow paths BP1 and BP2 may be collectively referred to as the bypass flow path BP. Note that one or both of the bypass flow path BP1 and the bypass flow path BP2 are examples of the "bypass flow path."

[0147] In this embodiment, as shown in Fig. 11, the wall surfaces of the bypass flow path BP in the Z2 direction and the Z1 direction are formed in a flat shape. However, the wall surfaces of the bypass flow path BP may include a surface inclined with respect to the YZ plane, similar to the wall surfaces of the individual flow paths RK. Alternatively, the wall surfaces of the bypass flow path BP may include a surface substantially parallel to the XZ plane. Furthermore, in this embodiment, it is assumed as an example that the wall surfaces defining the Z1 direction end of the bypass flow path BP are formed by the communicating plate 12, but the Z1 direction end of the bypass flow path BP may be formed by the nozzle substrate 11. Furthermore, in this embodiment, the bypass flow path BP is not provided with a nozzle N.

[0148] Next, the flow of ink in the first modified example will be described with reference to FIG.

[0149] Fig. 12 is an explanatory diagram for explaining the flow of ink in the first modified example. Fig. 12 shows the flow of ink in the common flow channel RC and the individual flow channels RK when the liquid ejection head 1 is viewed in a plane in the Z1 direction. In Fig. 12, as in Fig. 5, it is assumed that the value M is "8" and that each of the connection ports H1 and H2 is located between the individual flow channels RK[4] and RK[5] in the Y-axis direction.

[0150] In this embodiment, when circulating ink, the supply flow path 61 supplies ink to the common flow path RC1, and the recovery flow path 62 recovers ink from the common flow path RC2. For example, in the common flow path RC1, ink flows from the connection port H1 in the Y1 direction and the Y2 direction, as indicated by arrows AR11 and AR12. The ink flowing in the Y1 direction from the connection port H1 is supplied to the individual flow paths RK[5] to RK[8] and the bypass flow path BP2, and the ink flowing in the Y2 direction from the connection port H1 is supplied to the individual flow paths RK[1] to RK[4] and the bypass flow path BP1.

[0151] Also, in the individual flow path RK[j], as indicated by the arrow FA[j], ink flows from the common flow path RC1 to the common flow path RC2 in the X1 direction. As a result, for example, the pressure chamber CV provided in the individual flow path RK[j] is filled with ink. Also, in the bypass flow path BP, as indicated by the arrows FB1 and FB2, ink flows from the common flow path RC1 to the common flow path RC2 in the X1 direction.

[0152] Also, for example, in the common flow path RC2, as indicated by the arrows AR21 and AR22, ink flows from the individual flow paths RK[1] to RK[4] and the bypass flow path BP1 in the Y1 direction, and ink flows from the individual flow paths RK[5] to RK[8] and the bypass flow path BP2 in the Y2 direction. That is, the ink discharged from the individual flow paths RK[1] to RK[4] and the bypass flow path BP1 flows in the Y1 direction and is recovered into the recovery flow path 62 through the connection port H2. Also, the ink discharged from the individual flow paths RK[5] to RK[8] and the bypass flow path BP2 flows in the Y2 direction and is recovered into the recovery flow path 62 through the connection port H2.

[0153] Hereinafter, as shown in FIG. 12, the distance between the bypass flow path BP and the individual flow path RK adjacent to the bypass flow path BP in the Y-axis direction is referred to as the distance dYB, and the distance between one of the M individual flow paths RK and another individual flow path RK adjacent to the one individual flow path RK in the Y-axis direction is referred to as the distance dYK. More specifically, the distance between the bypass flow path BP1 and the individual flow path RK[1], and the distance between the bypass flow path BP2 and the individual flow path RK[M] are referred to as the distance dYB, and the distance between the individual flow path RK[j1] and the individual flow path RK[j2] is referred to as the distance dYK. Here, the variables j1 and j2 are natural numbers that satisfy "1 ≦ j1 < j2 ≦ M" and "1 + j1 = j2".

[0154] In this embodiment, as shown in FIG. 12 , the bypass flow path BP and the individual flow paths RK are provided so that the distance dYB and the distance dYK satisfy the relationship "dYB > dYK." Therefore, in this embodiment, the influence of noise, such as vibrations, generated by ink flowing through the bypass flow path BP on the ink flowing through the individual flow paths RK can be reduced compared to an embodiment in which the distance dYB is smaller than the distance dYK. As a result, in this embodiment, the variation in the ink ejection characteristics from the M nozzles N included in the liquid ejection head 1 can be reduced compared to an embodiment in which the distance dYB is smaller than the distance dYK. However, the present invention is not limited to an embodiment in which the bypass flow path BP is provided so that the distance dYB is greater than the distance dYK. That is, the bypass flow path BP may be provided so that the distance dYB is equal to or smaller than the distance dYK. In this case, the same effects as those of the above-described embodiment can be obtained, except for the effect obtained by providing the bypass flow path BP so that the distance dYB is greater than the distance dYK.

[0155] 12, M individual flow paths RK are provided between the bypass flow path BP1 and the bypass flow path BP2. Therefore, according to this aspect, it is possible to reduce the possibility of ink stagnation at the end of the common flow path RC1 and the end of the common flow path RC2 compared to an aspect in which one or both of the bypass flow path BP1 and the bypass flow path BP2 are provided between two of the M individual flow paths RK. As a result, according to this aspect, it is possible to reduce the possibility of ink thickening and air bubbles in the ink stagnation occurring at the end of the common flow path RC1 and the end of the common flow path RC2.

[0156] Here, the flow path resistance R of the bypass flow path BP, i.e., the combined flow path resistance R of the bypass flow path BP1 and the combined flow path resistance R of the bypass flow path BP2, is preferably at least one-third the combined flow path resistance R of the multiple individual flow paths RK. In this modification, we assume that the flow path resistance R of the bypass flow path BP is at least one-third the combined flow path resistance R of the multiple individual flow paths RK. In this case, the amount of ink passing through the bypass flow path BP is less than the amount of ink passing through several individual flow paths RK. Therefore, in this modification, even if the amount of ink passing through the bypass flow path BP is ignored, the flow path resistances Rin and Rout corresponding to the ink viscosity μ can be accurately calculated. In other words, if the amount of ink passing through the bypass flow path BP is large, the amount of ink passing through the bypass flow path BP cannot be ignored when calculating the flow path resistances Rin and Rout corresponding to the ink viscosity μ, making the calculation of the flow path resistances Rin and Rout complicated. That is, in this modified example, it is possible to prevent the calculation of the flow path resistances Rin and Rout from becoming complicated, while reducing the possibility of the ink thickening, the accumulation of air bubbles in the ink, etc. As a result, in this modified example, it is possible to appropriately adjust the pressure Pn in the vicinity of the nozzle N, while reducing the possibility of the ink thickening, the accumulation of air bubbles in the ink, etc.

[0157] 10 to 12 illustrate the case where the bypass flow path BP is formed in the communicating plate 12, but the present invention is not limited to this embodiment. For example, the bypass flow path BP may be formed in the communicating plate 12 and the pressure chamber substrate 13. Alternatively, the bypass flow path BP may be formed in a location separate from the communicating plate 12 and the pressure chamber substrate 13, for example, in a location located in the Z2 direction relative to the pressure chamber substrate 13. Furthermore, even when the above example or a known bypass flow path BP is used, it is preferable that the bypass flow path BP is formed so that the amount of ink passing through the bypass flow path BP does not exceed an amount that cannot be ignored when calculating the flow path resistance R corresponding to the viscosity μ of the ink.

[0158] As described above, in this modified example, the liquid ejection device 100 further includes a bypass flow path BP, which is a flow path separate from the multiple individual flow paths RK and connects the common flow path RC1 and the common flow path RC2. The flow path resistance R of the bypass flow path is at least one-third the combined flow path resistance obtained by combining the flow path resistances R of the multiple individual flow paths RK. In this modified example, the same effects as those of the above-described embodiment can be obtained. Furthermore, in this modified example, the provision of the bypass flow path BP can reduce the possibility of ink thickening and the accumulation of air bubbles in the ink.

[0159] [Second Modification] In the above-described embodiment and modified examples, a flow path including the common flow path RC1 and the individual flow paths RKin and a flow path including the common flow path RC2 and the individual flow paths RKout may be arranged approximately symmetrically with respect to the reference plane SF shown in FIG. 4. That is, the cross-sectional area of the common flow path RC1 in the ink flow direction and the cross-sectional area of the common flow path RC2 in the ink flow direction may be the same at positions symmetrical with respect to the reference plane SF. The reference plane SF is, for example, a plane parallel to the YZ plane that passes through the nozzles N. That is, the reference plane SF is a plane that passes through the nozzles N and has the ink flow direction in the multiple individual flow paths RK as its normal direction.

[0160] As described above, in this modified example, the cross-sectional area of the common flow channel RC1 in the ink flow direction and the cross-sectional area of the common flow channel RC2 in the ink flow direction are the same at positions symmetrical with respect to a plane passing through the nozzle N, the plane having the ink flow direction as the normal direction in the multiple individual flow channels RK. In this modified example as well, the change in flow channel resistance R according to the ink viscosity μ differs between the common flow channel RC1 and the common flow channel RC2, for example, depending on whether or not the filter FL is present. Therefore, in this modified example as well, the pressure Pn near the nozzle N can be appropriately adjusted, compared to the comparative example in which the pressure Pin and the pressure Pout are determined without using residual vibration.

[0161] [Third Modification] In the above-described embodiment and modified example, a filter FL is provided only in the common flow path RC1 of the common flow paths RC1 and RC2, but the present invention is not limited to this. For example, a filter FL may be provided only in the common flow path RC2 of the common flow paths RC1 and RC2. In this case, the flow path resistance R of one of the common flow paths RC1 and RC2, for example, the flow path resistance Rout, is greater than the inertial resistance, and the flow path resistance R of the other of the common flow paths RC1 and RC2, for example, the flow path resistance Rin, is greater than the inertial resistance.

[0162] Furthermore, filters FL may be provided in both the common flow paths RC1 and RC2, or filters FL may not be provided in both the common flow paths RC1 and RC2. The reason for the difference in the change in flow path resistance R in response to the ink viscosity μ between the common flow paths RC1 and RC2 is not limited to the presence or absence of filters FL. For example, the change in flow path resistance R in response to the ink viscosity μ between the common flow paths RC1 and RC2 may differ due to manufacturing errors or the like. Therefore, even in a configuration in which filters FL are provided in both the common flow paths RC1 and RC2, the pressure Pn near the nozzle N can be more appropriately adjusted than in a comparative example in which the pressures Pin and Pout are determined without using residual vibration. Similarly, even in a configuration in which filters FL are not provided in both the common flow paths RC1 and RC2, the pressure Pn near the nozzle N can be more appropriately adjusted than in a comparative example in which the pressures Pin and Pout are determined without using residual vibration.

[0163] Furthermore, a filter FL may be provided in one or both of the supply flow path 61 and the recovery flow path 62. When a filter FL is provided in one or both of the supply flow path 61 and the recovery flow path 62, a filter FL may be provided in at least one of the common flow paths RC1 and RC2, or a filter FL may not be provided in both of the common flow paths RC1 and RC2.

[0164] As described above, in this modification, the same effects as those of the above-described embodiment and modification can be obtained.

[0165] [Fourth Modification] In the above-described embodiment and modified example, the vibration absorbing plates CP1 and CP2 are provided spaced apart from each other, but the present invention is not limited to this. For example, the vibration absorbing plates CP1 and CP2 may be formed integrally. As described above, this modified example also provides the same effects as the above-described embodiment and modified example.

[0166] [Fifth Modification] In the above-described embodiment and modified examples, a compliance sheet that absorbs pressure fluctuations of ink in the common flow path BA may be provided. For example, the nozzle substrate 11 may be formed, like the diaphragm CPZ, so as to be shorter in the X-axis direction than the nozzle substrate 11 shown in FIG. 3, and may be disposed between two compliance sheets. Specifically, one of the two compliance sheets may be provided in a position in the Z1 direction relative to the communicating plate 12 and in the X2 direction relative to the nozzle substrate 11 so as to block the common flow path BA1. The other of the two compliance sheets may be provided in a position in the Z1 direction relative to the communicating plate 12 and in the X1 direction relative to the nozzle substrate 11 so as to block the common flow path BA2. As described above, this modified example can also achieve the same effects as the above-described embodiment and modified examples.

[0167] [Sixth Modification] In the above-described embodiment and modified example, a serial-type liquid ejection device 100 in which a carriage 91 carrying a liquid ejection head 1 is reciprocated in the X-axis direction is illustrated, but the present invention is not limited to such an embodiment. For example, the liquid ejection device 100 may be a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium PP. As described above, this modified example can also achieve the same effects as the above-described embodiment and modified example.

[0168] [Seventh Modification] In the above-described embodiment and modified example, a case has been illustrated in which one piezoelectric element PZ, one pressure chamber CV, and one nozzle N are provided for one discharge portion D, but the present invention is not limited to this form. For example, one discharge portion D may have two piezoelectric elements PZ, two pressure chambers CV, and one nozzle N. As described above, in this modified example, the same effects as those of the above-described embodiment and modified example can be obtained.

[0169] [Eighth Modification] The liquid ejection device 100 exemplified in the above-described embodiment and modified example can be employed in various devices such as facsimile machines and copiers, as well as devices dedicated to printing. 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 color material is used as a manufacturing device for forming color filters for liquid crystal display devices. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes for wiring boards. As described above, this modified example can also achieve the same effects as the above-described embodiment and modified example.

[0170] [3. Notes] From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0171] A liquid ejection device according to a preferred embodiment, aspect 1, comprises a piezoelectric element, a plurality of individual flow paths each including a nozzle and a pressure chamber, a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths, a common discharge flow path that is commonly connected to the plurality of individual flow paths and discharges liquid from the plurality of individual flow paths, a first pressure application unit that applies a first pressure to the common supply flow path to supply liquid to the common supply flow path, a second pressure application unit that applies a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path, a detection unit that detects residual vibrations in the pressure chambers after applying a voltage to the piezoelectric element, and a pressure determination unit that determines the first pressure and the second pressure based on the residual vibrations detected by the detection unit. According to the first aspect, the first pressure and the second pressure for adjusting the pressure near the nozzle to an appropriate pressure can be determined with high accuracy. As a result, according to the first aspect, the pressure near the nozzle can be adjusted appropriately.

[0172] In the liquid ejection device according to Aspect 2, which is a specific example of Aspect 1, the change in flow channel resistance according to the viscosity of the liquid differs between the common supply flow channel and the common discharge flow channel. According to aspect 2, even for a liquid ejection device in which the change in flow path resistance depending on the viscosity of the liquid differs between the common supply flow path and the common discharge flow path, the first pressure and the second pressure can be accurately determined to make the pressure near the nozzle appropriate.

[0173] In a liquid ejection device according to aspect 3, which is a specific example of aspect 1 or 2, the flow path resistance of one of the common supply flow path and the common discharge flow path is such that the viscous resistance is greater than the inertial resistance, and the flow path resistance of the other of the common supply flow path and the common discharge flow path is such that the inertial resistance is greater than the viscous resistance. According to aspect 3, even for a liquid ejection device in which the flow path resistance of one of the common supply flow path and the common discharge flow path is such that the viscous resistance is greater than the inertial resistance, and the flow path resistance of the other of the common supply flow path and the common discharge flow path is such that the inertial resistance is greater than the viscous resistance, the first pressure and the second pressure can be accurately determined to make the pressure near the nozzle appropriate.

[0174] In a liquid ejection device according to aspect 4, which is a specific example of any one of aspects 1 to 3, a filter is provided in only one of a first flow path between the first pressure application unit and the plurality of individual flow paths and a second flow path between the second pressure application unit and the plurality of individual flow paths, and the first flow path includes the common supply flow path, and the second flow path includes the common discharge flow path. According to the fourth aspect, even for a liquid ejection device in which a filter is provided in only one of the first flow path and the second flow path, the first pressure and the second pressure can be accurately determined to make the pressure near the nozzle appropriate.

[0175] In a liquid ejection device according to aspect 5, which is a specific example of any one of aspects 1 to 4, the cross-sectional area of the common supply flow path in the direction of liquid flow and the cross-sectional area of the common discharge flow path in the direction of liquid flow are the same at positions symmetrical with respect to a plane passing through the nozzle, the plane having the flow direction of liquid in the multiple individual flow paths as the normal direction. In the fifth aspect as well, the first pressure and the second pressure for making the pressure in the vicinity of the nozzle an appropriate pressure can be determined with high precision.

[0176] In a liquid ejection device according to aspect 6, which is a specific example of any one of aspects 1 to 5, the only flow paths that connect the common supply flow path and the common discharge flow path are the multiple individual flow paths. According to the sixth aspect, it is possible to prevent the process of determining the first pressure and the second pressure based on the residual vibration from becoming complicated.

[0177] A liquid ejection device according to aspect 7, which is a specific example of any one of aspects 1 to 5, further includes a bypass flow path that is separate from the plurality of individual flow paths and connects the common supply flow path and the common discharge flow path, and the flow path resistance of the bypass flow path is at least one-third of the combined flow path resistance obtained by combining the flow path resistances of the plurality of individual flow paths. According to aspect 7, it is possible to reduce the possibility of ink thickening and air bubbles remaining in the ink, and to accurately determine the first pressure and second pressure to ensure that the pressure near the nozzle is appropriate.

[0178] In a liquid ejection device according to aspect 8, which is a specific example of any one of aspects 1 to 7, the pressure determination unit calculates candidate combinations of the first pressure and the second pressure based on the residual vibration detected by the detection unit, presents the candidates to a user, obtains selection information indicating the candidate selected by the user from the candidates presented to the user, and determines the first pressure and the second pressure based on the selection information. According to the eighth aspect, it is possible to appropriately determine the combination of the first pressure and the second pressure to make the pressure in the vicinity of the nozzle an appropriate pressure.

[0179] In the liquid ejection device according to Aspect 9, which is a specific example of Aspect 8, the pressure determination unit recommends some of the candidates when presenting the candidates to the user. According to aspect 9, it is possible to prevent unrealistic combinations of the first pressure and the second pressure from being presented to the user, thereby preventing the user from selecting an unrealistic combination of the first pressure and the second pressure.

[0180] Furthermore, a control method for a liquid ejection device according to a preferred aspect 10 is a control method for a liquid ejection device comprising a piezoelectric element, a plurality of individual flow paths each including a nozzle and a pressure chamber, a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths, a common discharge flow path that is commonly connected to the plurality of individual flow paths and discharges liquid from the plurality of individual flow paths, a first pressure application unit that applies a first pressure to the common supply flow path to supply liquid to the common supply flow path, a second pressure application unit that applies a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path, and a detection unit that detects residual vibrations in the pressure chambers after applying a voltage to the piezoelectric element, and the first pressure and the second pressure are each determined based on the residual vibrations detected by the detection unit. In the tenth aspect as well, the first pressure and the second pressure for making the pressure in the vicinity of the nozzle an appropriate pressure can be determined with high precision.

[0181] Furthermore, a control program for a liquid ejection device according to a preferred aspect 11 is a control program for a liquid ejection device comprising a piezoelectric element, a plurality of individual flow paths each including a nozzle and a pressure chamber, a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths, a common discharge flow path that is commonly connected to the plurality of individual flow paths and discharges liquid from the plurality of individual flow paths, a first pressure application unit that applies a first pressure to the common supply flow path to supply liquid to the common supply flow path, a second pressure application unit that applies a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path, and a detection unit that detects residual vibrations in the pressure chambers after applying a voltage to the piezoelectric element, and causes a computer to function as a pressure determination unit that determines the first pressure and the second pressure based on the residual vibrations detected by the detection unit. In the eleventh aspect as well, the first pressure and the second pressure for making the pressure in the vicinity of the nozzle an appropriate pressure can be determined with high accuracy. [Explanation of symbols]

[0182] 1...liquid ejection head, 2...drive signal generation unit, 3...viscosity estimation unit, 4...control unit, 5...memory unit, 6...circulation mechanism, 7...maintenance unit, 8...medium conveying mechanism, 9...carriage conveying mechanism, 10...recording head, 18...switching circuit, 19...detection circuit, 40...circulation control unit, 100...liquid ejection device, CV...pressure chamber, D...ejection unit, N...nozzle, PG...control program, PP...medium, PZ...piezoelectric element.

Claims

1. a piezoelectric element; a plurality of individual flow paths each including a nozzle and a pressure chamber; a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths; a common discharge flow path that is in common communication with the plurality of individual flow paths and that discharges liquid from the plurality of individual flow paths; a first pressure applying unit for applying a first pressure to the common supply flow path for supplying liquid to the common supply flow path; a second pressure applying unit for applying a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path; a detection unit that detects residual vibration in the pressure chamber after a voltage is applied to the piezoelectric element; a pressure determination unit that determines the first pressure and the second pressure based on the residual vibration detected by the detection unit; A liquid ejection device comprising:

2. a change in flow path resistance according to the viscosity of the liquid differs between the common supply flow path and the common discharge flow path; The liquid ejection device according to claim 1 .

3. In the flow path resistance of one of the common supply flow path and the common discharge flow path, viscous resistance becomes larger than inertial resistance, In the flow path resistance of the other of the common supply flow path and the common discharge flow path, inertial resistance is greater than viscous resistance.

3. The liquid ejection device according to claim 2.

4. a filter is provided in only one of a first flow path between the first pressure-applying unit and the plurality of individual flow paths and a second flow path between the second pressure-applying unit and the plurality of individual flow paths; the first flow path includes the common supply flow path, The second flow path includes the common discharge flow path.

4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

5. a cross-sectional area of the common supply flow path in the direction of liquid flow and a cross-sectional area of the common discharge flow path in the direction of liquid flow are the same at positions symmetrical with respect to a plane passing through the nozzle, the plane having the flow direction of liquid in the plurality of individual flow paths as a normal direction; 5. The liquid ejection device according to claim 4.

6. The common supply flow path and the common discharge flow path are connected only by the individual flow paths.

4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

7. a bypass flow path that is a flow path separate from the plurality of individual flow paths and that connects the common supply flow path and the common discharge flow path; The flow path resistance of the bypass flow path is equal to or greater than one-third of the combined flow path resistance of the plurality of individual flow paths.

4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

8. The pressure determination unit calculating candidates for combinations of the first pressure and the second pressure based on the residual vibration detected by the detection unit; presenting the candidates to a user; obtaining selection information indicating a candidate selected by the user from among the candidates presented to the user; determining the first pressure and the second pressure based on the selection information; 4. The liquid ejection device according to claim 1, wherein the ejection head is a nozzle.

9. The pressure determination unit recommending a part of the candidates when presenting the candidates to the user; 9. The liquid ejection device according to claim 8.

10. a piezoelectric element; a plurality of individual flow paths each including a nozzle and a pressure chamber; a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths; a common discharge flow path that is in common communication with the plurality of individual flow paths and that discharges liquid from the plurality of individual flow paths; a first pressure applying unit for applying a first pressure to the common supply flow path for supplying liquid to the common supply flow path; a second pressure applying unit for applying a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path; a detection unit that detects residual vibration in the pressure chamber after a voltage is applied to the piezoelectric element; A method for controlling a liquid ejection device comprising: determining the first pressure and the second pressure based on the residual vibration detected by the detection unit; A method for controlling a liquid ejection device.

11. a piezoelectric element; a plurality of individual flow paths each including a nozzle and a pressure chamber; a common supply flow path that is commonly connected to the plurality of individual flow paths and supplies liquid to the plurality of individual flow paths; a common discharge flow path that is in common communication with the plurality of individual flow paths and that discharges liquid from the plurality of individual flow paths; a first pressure applying unit for applying a first pressure to the common supply flow path for supplying liquid to the common supply flow path; a second pressure applying unit for applying a second pressure to the common discharge flow path to discharge liquid from the common discharge flow path; a detection unit that detects residual vibration in the pressure chamber after a voltage is applied to the piezoelectric element; A control program for a liquid ejection device comprising: Computer, a pressure determining unit that determines the first pressure and the second pressure based on the residual vibration detected by the detecting unit; A control program for a liquid ejection device.

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