Liquid ejection device, liquid ejection head, and control method for liquid ejection device

Abstract

To set a detection signal to an appropriate amplitude.SOLUTION: A liquid ejection device comprises: an ejection unit including: a piezoelectric element configured to be driven by a driving signal; a pressure chamber which is filled with a liquid and a volume of which is changed according to driving of the piezoelectric element; and a nozzle configured to eject the liquid in the pressure chamber according to a change in the volume of the pressure chamber; a detection unit configured to detect, after the driving of the piezoelectric element, a vibration signal indicating a potential of the piezoelectric element that varies according to vibration remaining in the ejection unit, and generate a detection signal, based on the detected vibration signal; and a setting unit configured to set a signal amplification factor, based on liquid characteristic information related to a characteristic of the liquid ejected by the ejection unit and element characteristic information related to a characteristic of the piezoelectric element; wherein the detection unit generates the detection signal by amplifying the vibration signal according to the signal amplification factor set by the setting unit.SELECTED DRAWING: Figure 10

Description

[Technical field]

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

[0002] A liquid ejection device such as an inkjet printer drives a piezoelectric element provided in an ejection section of a liquid ejection head to eject liquid such as ink filled in a pressure chamber provided in the ejection section from a nozzle, thereby forming an image on a medium. However, in a liquid ejection device, an ejection abnormality may occur in which the liquid cannot be ejected normally from the ejection section. Therefore, a technique for determining the ejection state in the ejection section has been proposed in the past. For example, Patent Document 1 discloses a technique for determining the ejection state in the ejection section based on a detection signal obtained by amplifying a vibration signal indicating vibration remaining in the ejection section after driving the piezoelectric element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-044771 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the amplitude of the vibration remaining in the ejection section after the piezoelectric element is driven varies depending on the characteristics of the liquid ejected by the ejection section and the characteristics of the piezoelectric element. Therefore, when the ejection state in the ejection section is determined based on a detection signal obtained by amplifying a vibration signal indicating the vibration remaining in the ejection section by a certain amplification factor, the detection signal has an inappropriate amplitude, and therefore the ejection state may not be determined accurately. [Means for solving the problem]

[0005] In order to solve the above problems, the liquid ejection device of the present invention comprises an ejection unit having a piezoelectric element driven by a drive signal, a pressure chamber filled with liquid and whose volume changes in response to the driving of the piezoelectric element, and a nozzle that ejects the liquid in the pressure chamber in response to changes in the volume of the pressure chamber; a detection unit that detects a vibration signal indicating the electric potential of the piezoelectric element which fluctuates in response to vibration remaining in the ejection unit after the piezoelectric element is driven, and generates a detection signal based on the detected vibration signal; and a setting unit that sets a signal amplification factor based on liquid characteristic information related to the characteristics of the liquid ejected by the ejection unit and element characteristic information related to the characteristics of the piezoelectric element, and is characterized in that the detection unit generates the detection signal by amplifying the vibration signal in response to the signal amplification factor set by the setting unit.

[0006] In addition, the liquid ejection head of the present invention comprises an ejection section having a piezoelectric element driven by a drive signal, a pressure chamber filled with liquid and whose volume changes in response to the driving of the piezoelectric element, and a nozzle that ejects the liquid in the pressure chamber in response to the change in volume of the pressure chamber, and a detection section that detects a vibration signal indicating the electric potential of the piezoelectric element which fluctuates in response to vibration remaining in the ejection section after the piezoelectric element is driven, and generates a detection signal based on the detected vibration signal, wherein the detection section generates the detection signal by amplifying the vibration signal in accordance with a signal amplification factor set based on liquid characteristic information related to the characteristics of the liquid ejected by the ejection section and element characteristic information related to the characteristics of the piezoelectric element.

[0007] In addition, a control method according to the present invention is a control method for a liquid ejection device having an ejection unit equipped with a piezoelectric element driven by a drive signal, a pressure chamber filled with liquid and whose volume changes in response to the driving of the piezoelectric element, and a nozzle that ejects the liquid in the pressure chamber in response to the change in volume of the pressure chamber, characterized in that after the piezoelectric element is driven, a vibration signal indicating the potential of the piezoelectric element which fluctuates in response to vibration remaining in the ejection unit is detected, a signal amplification factor is set based on liquid characteristic information related to the characteristics of the liquid ejected by the ejection unit and element characteristic information related to the characteristics of the piezoelectric element, and the vibration signal is amplified in accordance with the signal amplification factor to generate a detection signal. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of an inkjet printer 1 according to an embodiment of the invention. [Diagram 2] FIG. 1 is a perspective view showing an example of a schematic structure of an inkjet printer 1. [Diagram 3] 13 is a cross-sectional view illustrating an example of the structure of a discharge section D[m]. FIG. [Figure 4] 2 is a block diagram showing an example of the configuration of a head unit 3. FIG. [Diagram 5] 4 is a timing chart for explaining an example of a signal supplied to the head unit 3. [Figure 6] FIG. 11 is an explanatory diagram illustrating an example of an individual designation signal Sd[m]. [Figure 7] FIG. 11 is an explanatory diagram illustrating an example of an individual designation signal Sd[m]. [Figure 8] 11 is a timing chart illustrating an example of a detection signal SK[m]. [Figure 9] 10A and 10B are explanatory diagrams for explaining an example of a discharge state determination process. [Figure 10] 11 is a flowchart illustrating an example of an amplification factor setting process. [Figure 11] FIG. 11 is an explanatory diagram for explaining an example of ink-compatible amplification information QGT. [Figure 12] It is an explanatory diagram for explaining an example of piezo-corresponding amplification information QGP. [Figure 13] It is an explanatory diagram for explaining an example of amplification rate enhancement information QGC. [Figure 14] It is a block diagram showing an example of the configuration of an inkjet printer 1B according to Modification 1 of the present invention. [Figure 15] It is a flowchart for explaining an example of the amplification rate setting process according to Modification 1. [Figure 16] It is an explanatory diagram for explaining an example of ink-corresponding amplitude information QKT. [Figure 17] It is an explanatory diagram for explaining an example of piezo-corresponding amplitude information QKP.

Mode for Carrying Out the Invention

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

[0010] <<A. Embodiment>> In the present embodiment, a liquid ejection device will be described by exemplifying an inkjet printer that ejects ink to form an image on a recording paper PP.

[0011] <<1. Outline of Inkjet Printer>> Hereinafter, with reference to FIGS. 1 to 3, an example of the configuration of an inkjet printer 1 according to the present embodiment will be described.

[0012] FIG. 1 is a functional block diagram showing an example of the configuration of an inkjet printer 1.

[0013] 1, print data Img indicating an image to be formed by the inkjet printer 1 is supplied from a host computer such as a personal computer or digital camera to the inkjet printer 1. The inkjet printer 1 executes a printing process to form, on recording paper PP, an image indicated by the print data Img supplied from the host computer.

[0014] As shown in FIG. 1, the inkjet printer 1 includes a control unit 2 that controls each component of the inkjet printer 1, a head unit 3 provided with an ejection section D that ejects ink, a drive signal generation unit 4 that generates a drive signal Com for driving the ejection section D, a determination unit 5 that determines the ink ejection state in the ejection section D, a memory unit 6 that stores various types of information, and a transport unit 7 that changes the relative position of recording paper PP with respect to the head unit 3. In this embodiment, the inkjet printer 1 is an example of a "liquid ejection device," the head unit 3 is an example of a "liquid ejection head," ink is an example of a "liquid," the drive signal generation unit 4 is an example of a "drive signal generation section," and the judgment unit 5 is an example of a "judgment section."

[0015] In this embodiment, it is assumed that the inkjet printer 1 includes one or more head units 3, one or more drive signal generating units 4 in one-to-one correspondence with the one or more head units 3, and one or more determination units 5 in one-to-one correspondence with the one or more head units 3. Specifically, in this embodiment, it is assumed that the inkjet printer 1 includes four head units 3, four drive signal generating units 4 in one-to-one correspondence with the four head units 3, and four determination units 5 in one-to-one correspondence with the four head units 3. However, for convenience of explanation, the following description focuses on one head unit 3 of the four head units 3, one drive signal generating unit 4 provided in correspondence with one head unit 3 of the four drive signal generating units 4, and one determination unit 5 provided in correspondence with one head unit 3 of the four drive signal generating units 4, as shown in FIG.

[0016] The control unit 2 includes one or more central processing units (CPUs). However, the control unit 2 may include a programmable logic device such as a field-programmable gate array (FPGA) instead of or in addition to a CPU.

[0017] The storage unit 6 is configured to include one or both of a volatile memory such as a RAM (Random Access Memory) and a non-volatile memory such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a PROM (Programmable ROM). As will be described in detail later, the storage unit 6 stores the control program PRG of the inkjet printer 1, ink-compatible amplification information QGT, piezo-compatible amplification information QGP, and amplification rate enhancement information QGC.

[0018] The control unit 2 executes the control program PRG stored in the memory unit 6 and operates in accordance with the control program PRG, thereby functioning as a drive control unit 21, an ejection control unit 22, a judgment management unit 23, an amplification factor setting unit 24, and a transport control unit 25.

[0019] The drive control unit 21 generates a waveform designation signal dCom and supplies the generated waveform designation signal dCom to the drive signal generation unit 4. Here, the waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the discharge section D. The drive signal generation unit 4 generates a drive signal Com having a waveform defined by the waveform designation signal dCom, and supplies the generated drive signal Com to the head unit 3.

[0020] The discharge control unit 22 generates a designation signal SI and supplies the generated designation signal SI to the head unit 3. Here, the designation signal SI is a digital signal that designates the type of operation of the discharge unit D. Specifically, the designation signal SI is a signal that designates whether or not to supply the drive signal Com to the discharge unit D, thereby designating the type of operation of the discharge unit D.

[0021] The head unit 3 includes a supply circuit 31, a recording head 32, a detection circuit 33, and a temperature sensor .

[0022] The recording head 32 has M discharge sections D. Here, the value M is a natural number that satisfies "M≧2". In the following, the m-th discharge section D of the M discharge sections D provided in the recording head 32 may be referred to as discharge section D[m]. Here, the variable m is a natural number that satisfies "1≦m≦M". In the following, when a component or signal of the inkjet printer 1 corresponds to a discharge section D[m] of the M discharge sections D, the subscript [m] may be added to the symbol representing the component or signal.

[0023] The supply circuit 31 switches whether to supply the drive signal Com to the discharge section D[m] based on the designation signal SI. Hereinafter, of the drive signals Com, the drive signal Com supplied to the discharge section D[m] may be referred to as a supply drive signal Vin[m].

[0024] Based on the designation signal SI, the supply circuit 31 switches whether to supply a vibration signal VX[m] indicating the potential of the upper electrode Zu[m] provided on the piezoelectric element PZ[m] of the discharge section D[m] to the detection circuit 33. In the following, when the vibration signal VX[m] is supplied from the discharge section D[m] to the detection circuit 33, the discharge section D[m] may be referred to as a discharge section DH to be determined. The piezoelectric element PZ[m] and the upper electrode Zu[m] will be described later with reference to FIG.

[0025] The detection circuit 33 generates a detection signal SK[m] based on the vibration signal VX[m] supplied from the discharge section D[m] determined as the judgment target discharge section DH via the supply circuit 31. Specifically, the detection circuit 33 generates the detection signal SK[m] by amplifying the vibration signal VX[m]. In this embodiment, the detection circuit 33 is an example of a "detection section."

[0026] The temperature sensor 35 measures the temperature AT of the head unit 3, and outputs a temperature signal ST indicating the measurement result. The temperature of the ink discharged by the discharge section D[m] corresponds to the temperature AT indicated by the temperature signal ST. The viscosity of the ink discharged by the discharge section D[m] corresponds to the temperature AT indicated by the temperature signal ST. In other words, the temperature signal ST indicates a temperature AT corresponding to the temperature and viscosity of the ink discharged by the discharge section D[m]. In this embodiment, the temperature of the ink discharged by the discharge section D[m] is an example of the "property of the liquid discharged by the discharge section", and the viscosity of the ink discharged by the discharge section D[m] is another example of the "property of the liquid discharged by the discharge section". In this embodiment, the information indicated by the temperature signal ST is an example of the "liquid property information".

[0027] The amplification factor setting unit 24 generates an amplification factor designation signal SG based on the temperature signal ST and the designation signal SI. Here, the amplification factor designation signal SG is a signal that designates the amplification factor AG[m] of the vibration signal VX[m] in the detection circuit 33. In this embodiment, the amplification factor AG[m] is an example of a "signal amplification factor." In addition, hereinafter, the process in which the amplification factor setting unit 24 generates the amplification factor designation signal SG may be referred to as an amplification factor setting process.

[0028] Specifically, in the amplification factor setting process, the amplification factor setting unit 24 first generates piezo drive count information SP based on the designation signal SI. Here, the piezo drive count information SP is information indicating the piezo drive counts AP[1] to AP[M] corresponding to the discharge sections D[1] to D[M]. Among them, the piezo drive count AP[m] is the number of times that the piezo element PZ[m] provided in the discharge section D[m] has been driven during the period from the time of shipment of the inkjet printer 1 to the present. In this embodiment, the number of times that the piezo element PZ[m] has been driven is an example of a "piezo element characteristic." In this embodiment, the piezo drive count information SP is an example of an "element characteristic information." Then, in the amplification factor setting process, the amplification factor setting unit 24 sets the amplification factor AG[m] based on the temperature signal ST and the piezo drive count information SP, and generates an amplification factor designation signal SG indicating the amplification factor AG[m]. Next, the amplification factor setting unit 24 supplies the amplification factor designation signal SG to the detection circuit 33. The detection circuit 33 generates a detection signal SK[m] by amplifying the vibration signal VX[m] according to the amplification factor AG[m] indicated by the amplification factor designation signal SG. In this embodiment, the amplification factor setting unit 24 is an example of a "setting unit."

[0029] In addition, in the amplification factor setting process, the amplification factor setting unit 24 generates a drive waveform correction signal SC based on the temperature signal ST and the specification signal SI. Here, the drive waveform correction signal SC is a signal that instructs correction of the waveform of the drive signal Com, and is a signal that indicates the amplitude AC of the drive signal Com after correction. When the drive waveform correction signal SC is supplied from the amplification factor setting unit 24, the drive control unit 21 corrects the waveform specification signal dCom so that the amplitude of the drive signal Com becomes the amplitude AC indicated by the drive waveform correction signal SC.

[0030] The judgment unit 5 judges the ink discharge state in the discharge section D[m] based on the detection signal SK[m]. In other words, the judgment unit 5 judges whether or not a discharge abnormality occurs in the discharge section D[m] based on the detection signal SK[m]. Here, the discharge abnormality is a general term for a state in which ink cannot be normally discharged from the nozzle N of the discharge section D[m]. For example, the discharge abnormality includes a state in which ink cannot be discharged from the discharge section D[m], a state in which the discharge section D[m] discharges an amount of ink different from the ink discharge amount defined by the drive signal Com, and a state in which the discharge section D[m] discharges ink at a speed different from the ink discharge speed defined by the drive signal Com. In the following, the process of determining the ejection state of the ejection section D[m] based on the detection signal SK[m] will be referred to as an ejection state determination process. Moreover, hereinafter, the process of driving the discharge section D[m] as the determination target discharge section DH and detecting the vibration signal VX[m] from the discharge section D[m] is referred to as determination target drive process.

[0031] The judgment unit 5 generates result information SH based on the result of the judgment of the ink discharge state, and supplies the generated result information SH to the judgment management section 23. Then, the judgment management section 23 manages the result information SH supplied from the judgment unit 5. Here, the result information SH includes judgment result information SH1[m] indicating the result of the judgment of the ink discharge state in the discharge section D[m], and amplitude information SH2[m] indicating the amplitude AK[m] of the detection signal SK[m].

[0032] As described above, the inkjet printer 1 executes a printing process. When the printing process is executed, the ejection control unit 22 generates signals for controlling the head unit 3, such as a designation signal SI, based on the print data Img. The drive control unit 21 also generates signals for controlling the drive signal generating unit 4, such as a waveform designation signal dCom. The transport control unit 25 also generates a transport control signal MH for controlling the transport unit 7. In this way, during the printing process, the control unit 2 controls the transport unit 7 to change the relative position of the recording paper PP with respect to the head unit 3, while adjusting the presence or absence of ink ejection from the ejection unit D[m], the amount of ink ejection, and the timing of ink ejection, and controls each part of the inkjet printer 1 so that an image corresponding to the print data Img is formed on the recording paper PP. Hereinafter, the printing process and the determination target drive process may be collectively referred to as the ejection section drive process.

[0033] FIG. 2 is a perspective view showing an example of a schematic internal structure of the inkjet printer 1. As shown in FIG.

[0034] 2, this embodiment assumes that the inkjet printer 1 is a serial printer. Specifically, when executing a printing process, the inkjet printer 1 transports the recording paper PP in the X1 direction, while reciprocating the head unit 3 in the Y1 direction that intersects with the X1 direction, and in the Y2 direction that is the opposite direction to the Y1 direction, to eject ink from the ejection section D[m], thereby forming dots Dt on the recording paper PP according to the print data Img.

[0035] Hereinafter, the X1 direction and its opposite X2 direction will be collectively referred to as the "X-axis direction", the Y1 direction intersecting the X-axis direction and its opposite Y2 direction will be collectively referred to as the "Y-axis direction", and the Z1 direction intersecting the X-axis and Y-axis directions and its opposite Z2 direction will be collectively referred to as the "Z-axis direction". In this embodiment, as an example, a description will be given assuming that the X-axis direction, the Y-axis direction, and the Z-axis direction are mutually orthogonal. However, the present invention is not limited to this aspect. It is sufficient that the X-axis direction, the Y-axis direction, and the Z-axis direction intersect with each other. In this embodiment, the Z1 direction is the direction in which ink is ejected from the ejection section D[m].

[0036] As shown in FIG. 2, the inkjet printer 1 according to this embodiment includes a housing 100, and a carriage 110 that is capable of reciprocating within the housing 100 in the Y-axis direction and that has four head units 3 mounted thereon.

[0037] In this embodiment, as shown in FIG. 2, it is assumed that the carriage 110 stores four ink cartridges 120 in one-to-one correspondence with the four colors of ink: cyan, magenta, yellow, and black. Also, in this embodiment, it is assumed that the inkjet printer 1 includes four head units 3 in one-to-one correspondence with the four ink cartridges 120, as described above. Each ejection section D[m] receives a supply of ink from the ink cartridge 120 corresponding to the head unit 3 in which the ejection section D[m] is provided. This allows each ejection section D[m] to fill itself with the supplied ink and eject the filled ink from the nozzle N. Note that the ink cartridges 120 may be provided outside the carriage 110.

[0038] As described above, the inkjet printer 1 according to this embodiment also includes a transport unit 7. The transport unit 7 includes a carriage transport mechanism 71 for reciprocating the carriage 110 in the Y axis direction, a carriage guide shaft 76 that supports the carriage 110 so that it can reciprocate in the Y axis direction, a medium transport mechanism 73 for transporting the recording paper PP, and a platen 75 provided in the Z1 direction of the carriage 110. Thus, when a printing process is performed, the transport unit 7 causes the carriage transport mechanism 71 to reciprocate the head unit 3 together with the carriage 110 along the carriage guide shaft 76 in the Y axis direction, and the medium transport mechanism 73 to transport the recording paper PP on the platen 75 in the X1 direction, thereby changing the relative position of the recording paper PP with respect to the head unit 3 and enabling ink to land on the entire recording paper PP.

[0039] FIG. 3 is a schematic partial cross-sectional view of the recording head 32, in which the recording head 32 is cut so as to include the ejection portion D[m].

[0040] As shown in FIG. 3, the ejection section D[m] includes a piezoelectric element PZ[m], a cavity CV[m] filled with ink, a nozzle N[m] communicating with the cavity CV[m], and a vibration plate 321. The ejection section D[m] ejects ink in the cavity CV[m] from the nozzle N[m] by driving the piezoelectric element PZ[m] with a supply drive signal Vin[m]. The cavity CV[m] is a space defined by a cavity plate 324, a nozzle plate 323 in which the nozzle N[m] is formed, and the vibration plate 321. The cavity CV[m] communicates with a reservoir 325 via an ink supply port 326. The reservoir 325 communicates with the ink cartridge 120 corresponding to the ejection section D[m] via an ink intake port 327. The piezoelectric element PZ[m] has an upper electrode Zu[m], a lower electrode Zd[m], and a piezoelectric body Zm[m] provided between the upper electrode Zu[m] and the lower electrode Zd[m]. The lower electrode Zd[m] is electrically connected to a power supply line Lv set to a predetermined potential VBS. When a supply drive signal Vin[m] is supplied to the upper electrode Zu[m] and a voltage is applied between the upper electrode Zu[m] and the lower electrode Zd[m], the piezoelectric element PZ[m] is displaced in the Z1 direction or the Z2 direction according to the applied voltage, and as a result, the piezoelectric element PZ[m] vibrates. The lower electrode Zd[m] is joined to the vibration plate 321. Therefore, when the piezoelectric element PZ[m] is driven to vibrate by the supply drive signal Vin[m], the vibration plate 321 also vibrates. The vibration of the diaphragm 321 changes the volume of the cavity CV[m] and the pressure within the cavity CV[m], and the ink filled in the cavity CV[m] is ejected from the nozzle N[m]. In this embodiment, the piezoelectric element PZ[m] is an example of a "piezoelectric element," and the cavity CV[m] is an example of a "pressure chamber."

[0041] <<2. Head unit overview>> Hereinafter, an overview of the head unit 3 will be described with reference to FIGS.

[0042] FIG. 4 is a block diagram showing an example of the configuration of the head unit 3. As shown in FIG.

[0043] 4, the head unit 3 includes a supply circuit 31, a recording head 32, and a detection circuit 33. The head unit 3 also includes a wiring Lc to which the drive signal Com is supplied from the drive signal generating unit 4, and a wiring Ls for supplying the vibration signal VX[m] to the detection circuit 33.

[0044] The supply circuit 31 includes M switches Wc[1] to Wc[M] each having a one-to-one correspondence with the M discharge sections D[1] to D[M], M switches Ws[1] to Ws[M] each having a one-to-one correspondence with the M discharge sections D[1] to D[M], and a connection state designation circuit 34 that designates the connection state of each switch.

[0045] The connection state designation circuit 34 generates a connection state designation signal Rc[m] that designates the on / off state of the switch Wc[m] and a connection state designation signal Rs[m] that designates the on / off state of the switch Ws[m] based on the designation signal SI, the latch signal LAT, the change signal CH, and the period designation signal Tsig supplied from the control unit 2.

[0046] The switch Wc[m] switches between electrical continuity and non-conduction between the wiring Lc and the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designation signal Rc[m]. In this embodiment, the switch Wc[m] is turned on when the connection state designation signal Rc[m] is at a high level, and turned off when the connection state designation signal Rc[m] is at a low level. When the switch Wc[m] is turned on, the drive signal Com supplied to the wiring Lc is supplied to the upper electrode Zu[m] of the discharge section D[m] as the supply drive signal Vin[m]. The switch Ws[m] switches between electrical continuity and non-conduction between the wiring Ls and the upper electrode Zu[m] of the piezoelectric element PZ[m] based on the connection state designation signal Rs[m]. In this embodiment, the switch Ws[m] is turned on when the connection state designation signal Rs[m] is at a high level, and turned off when the connection state designation signal Rs[m] is at a low level. When the switch Ws[m] is turned on, a vibration signal VX[m] indicating the potential of the upper electrode Zu[m] provided on the discharge section D[m] is supplied from the upper electrode Zu[m] to the detection circuit 33 via the wiring Ls.

[0047] The detection circuit 33 generates a detection signal SK[m] having a waveform corresponding to the waveform of the vibration signal VX[m] based on the vibration signal VX[m] supplied from the wiring Ls and the amplification factor designation signal SG supplied from the amplification factor setting unit 24. Specifically, the detection circuit 33 generates the detection signal SK[m] by amplifying the vibration signal VX[m] by the amplification factor AG[m] indicated by the amplification factor designation signal SG.

[0048] In this embodiment, when the inkjet printer 1 executes a printing process or an ejection state determination process, one or more unit periods TP are set as the operating period of the inkjet printer 1. During each unit period TP, the inkjet printer 1 can drive each ejection section D[m] for the printing process or the ejection section drive process, which includes the determination target drive process.

[0049] FIG. 5 is a timing chart showing an example of various signals such as the drive signal Com supplied to the head unit 3 in the unit period TP.

[0050] 5, the control unit 2 outputs a latch signal LAT having a pulse PLL, whereby the control unit 2 defines a unit period TP as a period from the rising edge of the pulse PLL to the rising edge of the next pulse PLL. Moreover, the control unit 2 outputs a change signal CH having a pulse PLC in a unit period TP. The control unit 2 then divides the unit period TP into a drive period TQ1 from the rising edge of the pulse PLL to the rising edge of the pulse PLC, and a drive period TQ2 from the rising edge of the pulse PLC to the rising edge of the pulse PLL.

[0051] Moreover, the control unit 2 outputs a period designation signal Tsig having a pulse PLT1 and a pulse PLT2 in the unit period TP. The control unit 2 divides the unit period TP into a control period TS1 from the rising edge of the pulse PLL to the rising edge of the pulse PLT1, a control period TS2 from the rising edge of the pulse PLT1 to the rising edge of the pulse PLT2, and a control period TS3 from the rising edge of the pulse PLT2 to the rising edge of the pulse PLL.

[0052] As shown in FIG. 5, the designation signal SI includes 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[m] designates the driving mode of the discharge section D[m] in each unit period TP when the inkjet printer 1 executes a printing process or a discharge state determination process. Prior to each unit period TP, the control unit 2 supplies the designation signal SI including the M individual designation signals Sd[1] to Sd[M] to the connection state designation circuit 34 in synchronization with the clock signal CL. Then, during the unit period TP, the connection state designation circuit 34 generates a connection state designation signal Rc[m] and a connection state designation signal Rs[m] based on the individual designation signal Sd[m].

[0053] In this embodiment, it is assumed that when the inkjet printer 1 executes a printing process or a drive process for a target to be determined, the ejection section D[m] is capable of forming either a large dot Dt made of ink with an ink amount ξ1, or a small dot made of ink with an ink amount ξ2 that is less than the ink amount ξ1.

[0054] 6 and 7 are diagrams illustrating an example of the individual designation signal Sd[m].

[0055] As shown in Figures 6 and 7, in this embodiment, the individual designation signal Sd[m] indicates one of four values ​​during the unit period TP: a value "1" that designates the discharge section D[m] as a large dot-forming discharge section DP-1, a value "2" that designates the discharge section D[m] as a small dot-forming discharge section DP-2, a value "3" that designates the discharge section D[m] as a non-driven discharge section DP-3, and a value "4" that designates the discharge section D[m] as the discharge section DH to be judged.

[0056] Here, the large dot-forming discharge section DP-1 is a discharge section D that forms large dots in the unit period TP. The small dot-forming discharge section DP-2 is a discharge section D that forms small dots in the unit period TP. The non-driven discharge section DP-3 is a discharge section D that is not driven by the drive signal Com in the unit period TP. The judgment target discharge section DH is a discharge section D that is the target of the discharge state judgment process in the unit period TP.

[0057] Let us return to the explanation given in FIG. As shown in FIG. 5, in this embodiment, the driving signal Com has a waveform PA1 provided in a driving period TQ1 and a waveform PA2 provided in a driving period TQ2.

[0058] Of these, the waveform PA1 is a waveform that, during a control period TS1 of the drive period TQ1, goes from a reference potential V0 to a potential VL1 lower than the reference potential V0 and a potential VH1 higher than the reference potential V0, returns to the reference potential V0, and maintains the reference potential V0 during control periods TS2 and TS3 of the drive period TQ1. The waveform PA1 is determined so that when a supply drive signal Vin[m] having the waveform PA1 is supplied to the ejection section D[m], ink equivalent to the ink amount ξ1 is ejected from the ejection section D[m].

[0059] Moreover, the waveform PA2 is a waveform that, during the drive period TQ2, goes from the reference potential V0 through a potential VL2 lower than the reference potential V0 and a potential VH2 higher than the reference potential V0, before returning to the reference potential V0. The waveform PA2 is determined so that when a supply drive signal Vin[m] having the waveform PA2 is supplied to the ejection section D[m], ink equivalent to the ink amount ξ2 is ejected from the ejection section D[m].

[0060] In this embodiment, as an example, it is assumed that when the potential of the supply drive signal Vin[m] supplied to the discharge section D[m] is high, the volume of the cavity CV[m] of the discharge section D[m] is smaller than when the potential is low. Therefore, when the discharge section D[m] is driven by the supply drive signal Vin[m] having a waveform PA1 or the like, the potential of the supply drive signal Vin[m] changes from low to high, causing the ink in the discharge section D[m] to be discharged from the nozzle N[m].

[0061] Next, the operation of the discharge section D[m] designated by the individual designation signal Sd[m] will be described with reference to FIGS.

[0062] 6, when the individual designation signal Sd[m] indicates a value of "1" that designates the discharge section D[m] as the large dot forming discharge section DP-1 during the unit period TP, the connection state designation circuit 34 sets the connection state designation signal Rc[m] to a high level during the drive period TQ1. In this case, the switch Wc[m] is turned on during the drive period TQ1. Therefore, during the unit period TP, the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveform PA1, and discharges ink of the ink amount ξ1 corresponding to a large dot.

[0063] Furthermore, when the individual designation signal Sd[m] indicates a value of "2" that designates the discharge section D[m] as the small dot forming discharge section DP-2 during the unit period TP, the connection state designation circuit 34 sets the connection state designation signal Rc[m] to a high level during the drive period TQ2. In this case, the switch Wc[m] is turned on during the drive period TQ2. Therefore, during the unit period TP, the discharge section D[m] is driven by the supply drive signal Vin[m] having the waveform PA2, and discharges ink of the ink amount ξ2 corresponding to a small dot.

[0064] Furthermore, when the individual designation signal Sd[m] indicates a value of "3" that designates the discharge section D[m] as the non-driven discharge section DP-3 during the unit period TP, the connection state designation circuit 34 sets the connection state designation signal Rc[m] and the connection state designation signal Rs[m] to a low level during the unit period TP. In this case, the switches Wc[m] and Ws[m] are turned off during the unit period TP. Therefore, the discharge section D[m] is not driven by the drive signal Com during the unit period TP, and does not discharge ink.

[0065] As shown in FIG. 7, when the individual designation signal Sd[m] indicates a value "4" that designates the discharge section D[m] as the discharge section DH to be determined in the unit period TP, the connection state designation circuit 34 sets the connection state designation signal Rc[m] to a high level in the control period TS1, and sets the connection state designation signal Rs[m] to a high level in the control period TS2. In this case, the switch Wc[m] is turned on in the control period TS1, and the switch Ws[m] is turned on in the control period TS2. Therefore, as a result of the discharge section D[m] designated as the discharge section DH to be determined being driven by the supply drive signal Vin[m] having the waveform PA1 in the control period TS1, the vibration generated in the discharge section D[m] remains in the control period TS2. Then, in the control period TS2, the potential of the upper electrode Zu[m] provided on the discharge section D[m] changes according to the vibration remaining in the discharge section D[m]. The detection circuit 33 detects the potential of the upper electrode Zu[m], which changes in response to the vibration remaining in the discharge section D[m], as a vibration signal VX[m] via the switch Ws[m] during the control period TS2. That is, the waveform of the vibration signal VX[m] detected from the discharge section D[m] during the control period TS2 represents the waveform of the vibration remaining in the discharge section D[m] during the control period TS2. The waveform of the detection signal SK[m] generated based on the vibration signal VX[m] detected from the discharge section D[m] during the control period TS2 represents the waveform of the vibration remaining in the discharge section D[m] during the control period TS2.

[0066] <<3. Overview of the Judgment Unit>> Hereinafter, an overview of the determination unit 5 will be described with reference to FIGS.

[0067] As described above, the determination unit 5 executes the ejection state determination process to determine the ink ejection state of the ejection section D[m] designated as the determination target ejection section DH, based on the detection signal SK[m] supplied from the detection circuit 33.

[0068] 8 is a timing chart for explaining an example of the detection signal SK[m] supplied by the detection circuit 33 to the judgment unit 5. Note that the detection signal SK[m] output by the detection circuit 33 during the control period TS2 indicates a waveform based on the vibration remaining in the discharge section D[m] during the control period TS2.

[0069] 8, hereinafter, the period from when the potential of the detection signal SK[m] matches the reference potential VK0 set near the center of the amplitude of the detection signal SK[m] to when it next matches the reference potential VK0 is referred to as a cycle period NTC[m]. In addition, hereinafter, the time length of the cycle period NTC[m] is referred to as a cycle TC[m] of the detection signal SK[m]. In this embodiment, the cycle TC[m] is an example of a "characteristic amount indicated by the detection signal SK[m]." In addition, in this embodiment, the potential difference between the highest potential VKH[m] of the detection signal SK[m] and the lowest potential VKL[m] of the detection signal SK[m] during the cycle period NTC[m] is regarded as the amplitude AK[m] of the detection signal SK[m].

[0070] In this embodiment, the judgment unit 5 measures the period TC[m] and amplitude AK[m] of the detection signal SK[m]. The judgment unit 5 then executes a discharge state judgment process to judge the ink discharge state of the discharge section D[m] based on the period TC[m] and generate judgment result information SH1[m] indicating the result of the judgment. Next, the judgment unit 5 generates result information SH including the judgment result information SH1[m] and amplitude information SH2[m] indicating the amplitude AK[m], and supplies the generated result information SH to the control unit 2.

[0071] FIG. 9 is an explanatory diagram for explaining an example of generation of the determination result information SH1[m] in the ejection state determination process of the determination unit 5. In FIG.

[0072] As shown in Figure 9, in the ejection state judgment process, the judgment unit 5 judges the ink ejection state in the ejection section D[m] by comparing the period TC[m] with some or all of the thresholds Tth1, Tth2, and Tth3, and generates judgment result information SH1[m] indicating the result of the judgment.

[0073] The threshold value Tth1 is a fixed value that indicates the boundary between the period TC[m] of the residual vibration that occurs in the discharge section D[m] when the discharge state of the discharge section D[m] is normal, and the period TC[m] of the residual vibration that occurs in the discharge section D[m] when air bubbles have entered the cavity CV[m] of the discharge section D[m]. Threshold value Tth2 is a value greater than threshold value Tth1, and is a fixed value that indicates the boundary between the period TC[m] of the residual vibration that occurs in the discharge section D[m] when the discharge state of the discharge section D[m] is normal, and the period TC[m] of the residual vibration that occurs in the discharge section D[m] when foreign matter adheres near the nozzle N[m] of the discharge section D[m]. Threshold value Tth3 is a value greater than threshold value Tth2, and is a fixed value that indicates the boundary between the period TC[m] of the residual vibration that occurs in the ejection section D[m] when foreign matter adheres near the nozzle N[m] of the ejection section D[m], and the period TC[m] of the residual vibration that occurs in the ejection section D[m] when the ink in the cavity CV[m] of the ejection section D[m] becomes thicker. In addition, in this embodiment, the threshold values Tth1, Tth2, and Tth3 are examples of "fixed reference values".

[0074] In this embodiment, in the ejection state determination process, when the cycle TC[m] satisfies "Tth1 ≦ TC[m] ≦ Tth2", the determination unit 5 determines that the ink ejection state in the ejection unit D[m] is normal, and sets the value "1", which indicates that the ink ejection state in the ejection unit D[m] is normal, for the determination result information SH1[m]. Further, in the ejection state determination process, when the cycle TC[m] satisfies "TC[m] < Tth1", the determination unit 5 determines that ejection abnormality due to bubbles has occurred in the ejection unit D[m], and sets the value "2", which indicates that ejection abnormality due to bubbles has occurred in the ejection unit D[m], for the determination result information SH1[m]. Further, in the ejection state determination process, when the cycle TC[m] satisfies "Tth2 < TC[m] ≦ Tth3", the determination unit 5 determines that ejection abnormality due to foreign matter adhesion has occurred in the ejection unit D[m], and sets the value "3", which indicates that ejection abnormality due to foreign matter adhesion has occurred in the ejection unit D[m], for the determination result information SH1[m]. Further, in the ejection state determination process, when the cycle TC[m] satisfies "Tth3 < TC[m]", the determination unit 5 determines that ejection abnormality due to thickening has occurred in the ejection unit D[m], and sets the value "4", which indicates that ejection abnormality due to thickening has occurred in the ejection unit D[m], for the determination result information SH1[m].

[0075] Note that, in this embodiment, an example is given in which the determination unit 5 can compare the cycle TC[m] with three threshold values, i.e., the threshold values Tth1, Tth2, and Tth3. However, the present invention is not limited to such a mode. It is sufficient that the determination unit 5 can compare the cycle TC[m] with one or more of the three threshold values, i.e., the threshold values Tth1, Tth2, and Tth3.

[0076] As described above, the judgment unit 5 generates result information SH based on the detection signal SK[m], which includes judgment result information SH1[m] indicating the result of the judgment of the ink ejection state in the ejection section D[m], and amplitude information SH2[m] indicating the amplitude AK[m] of the detection signal SK[m].

[0077] Generally, the amplitude of the vibration signal VX[m] varies depending on the temperature and viscosity of the ink discharged by the discharge section D[m]. Therefore, the amplitude AK[m] of the detection signal SK[m] also varies depending on the temperature and viscosity of the ink discharged by the discharge section D[m]. Generally, the amplitude of the vibration signal VX[m] varies depending on the degree of deterioration of the piezoelectric element PZ[m] of the discharge section D[m]. Therefore, the amplitude AK[m] of the detection signal SK[m] also varies depending on the degree of deterioration of the piezoelectric element PZ[m] of the discharge section D[m].

[0078] For this reason, when the detection circuit 33 generates the detection signal SK[m] by amplifying the vibration signal VX[m] at a constant amplification rate as in the past, and the judgment unit 5 executes the discharge state judgment process for the discharge section D[m] based on the detection signal SK[m], the amplitude AK[m] of the detection signal SK[m] may be an amplitude inappropriate for the discharge state judgment process. Specifically, when the detection circuit 33 amplifies the vibration signal VX[m] at a constant amplification rate as in the past, the amplitude AK[m] of the detection signal SK[m] may become larger than a predetermined upper limit amplitude AK1, which may reduce the accuracy of the discharge state judgment process based on the detection signal SK[m]. Also, when the detection circuit 33 amplifies the vibration signal VX[m] at a constant amplification rate as in the past, the amplitude AK[m] of the detection signal SK[m] may become smaller than a predetermined lower limit amplitude AK2, which may make it difficult to measure the period TC[m] of the detection signal SK[m], and may make it difficult to execute the discharge state judgment process based on the detection signal SK[m].

[0079] In contrast, according to the present embodiment, as described above, the amplification factor setting unit 24 sets the amplification factor AG[m] based on the designation signal SI and the temperature signal ST. Then, according to the present embodiment, as described above, the detection circuit 33 amplifies the vibration signal VX[m] according to the amplification factor AG[m] to generate the detection signal SK[m]. Therefore, according to the present embodiment, it is possible to set the amplitude AK[m] of the detection signal SK[m] so that it is within a predetermined amplitude range including the reference amplitude AK0 suitable for the discharge state determination process, which is equal to or larger than the lower limit amplitude AK2 and equal to or smaller than the upper limit amplitude AK1. As a result, according to the present embodiment, it is possible to improve the accuracy of the amplification factor setting process based on the detection signal SK[m], compared to the conventional case in which the detection circuit 33 amplifies the vibration signal VX[m] at a constant amplification factor.

[0080] <<4. Amplification rate setting process>> Hereinafter, an overview of the amplification factor setting process will be described with reference to FIGS.

[0081] FIG. 10 is a flowchart showing an example of the operation of the control unit 2 when the amplification factor setting process is executed.

[0082] As shown in FIG. 10, when the amplification factor setting process is started, the amplification factor setting unit 24 acquires a temperature signal ST from the temperature sensor 35 (S101). Moreover, the amplification factor setting unit 24 acquires a designation signal SI from the discharge control unit 22 (S103).

[0083] Next, the amplification factor setting unit 24 generates piezo drive number information SP indicating the piezo drive number AP[m] based on the designation signal SI acquired in step S103 (S105). Specifically, the amplification factor setting unit 24 stores the piezo drive count information SP generated in step S105 in one amplification factor setting process in the storage unit 6. Then, in step S105 of another amplification factor setting process executed after the one amplification factor setting process, the amplification factor setting unit 24 acquires the piezo drive count information SP stored in the storage unit 6. Next, in step S105 of the other amplification factor setting process, the amplification factor setting unit 24 updates the piezo drive count AP[m] by adding the drive count of the ejection section D[m] indicated by the designation signal SI acquired in step S103 of the other amplification factor setting process to the piezo drive count AP[m] indicated by the piezo drive count information SP acquired from the storage unit 6, and generates piezo drive count information SP indicating the updated piezo drive count AP[m].

[0084] As shown in FIG. 10, the amplification factor setting unit 24 sets a provisional amplification factor AGT[m] based on the temperature signal ST acquired in step S101 and the ink-compatible amplification information QGT stored in the storage unit 6 (S107).

[0085] FIG. 11 is an explanatory diagram for explaining an example of the ink-compatible amplification information QGT.

[0086] As shown in FIG. 11, the ink-based amplification information QGT is information indicating a curve LGT0 representing a combination of the amplification factor AG[m] and the temperature AT for maintaining the amplitude AK[m] of the detection signal SK[m] at the reference amplitude AK0 in a graph G-GT in which the horizontal axis represents a temperature coordinate value ATx corresponding to the temperature AT and the vertical axis represents an amplification factor coordinate value AGy corresponding to the amplification factor AG[m]. Specifically, the ink-based amplification information QGT is information indicating the coordinates of each of a plurality of points on the curve LGT0 in the graph G-GT. For example, in FIG. 11, the point where the temperature coordinate value ATx is the reference temperature AT0 and the amplification factor coordinate value AGy is the reference amplification factor AGT0 is a point on the curve LGT0. Therefore, when the temperature AT is the reference temperature AT0 and the amplification factor AG[m] is the reference amplification factor AGT0, the amplitude AK[m] of the detection signal SK[m] becomes the reference amplitude AK0.

[0087] Moreover, the ink-based amplification information QGT is information indicating a curve LGT1 that represents a combination of the amplification factor AG[m] and the temperature AT for maintaining the amplitude AK[m] of the detection signal SK[m] at the upper limit amplitude AK1. Specifically, the ink-based amplification information QGT is information indicating the coordinates of each of a plurality of points on the curve LGT1 in the graph G-GT. Moreover, the ink-based amplification information QGT is information indicating a curve LGT2 that represents a combination of the amplification factor AG[m] and the temperature AT for maintaining the amplitude AK[m] of the detection signal SK[m] at the lower limit amplitude AK2. Specifically, the ink-based amplification information QGT is information indicating the coordinates of each of a plurality of points on the curve LGT2 in the graph G-GT.

[0088] In step S107 of the amplification factor setting process, the amplification factor setting unit 24 refers to the ink-compatible amplification information QGT to identify a point on the curve LGT0 having, as a temperature coordinate value ATx, the temperature AT indicated by the temperature signal ST acquired in step S101. In this embodiment, the amplification factor setting unit 24 then sets the amplification factor coordinate value AGy corresponding to the identified point on the curve LGT0 as the provisional amplification factor AGT[m]. Note that in this embodiment, the amplification factor setting unit 24 sets the provisional amplification factor AGT[m] to a larger value when the temperature AT indicated by the temperature signal ST is low compared to when it is high.

[0089] In this embodiment, the gain coordinate value AGy corresponding to a point on the curve LGT0 is set as the provisional gain AGT[m], but the present invention is not limited to this embodiment. For example, in step S107, the gain setting unit 24 may set, as the provisional gain AGT[m], a gain coordinate value AGy in a range that is equal to or greater than the gain coordinate value AGy corresponding to a point on the curve LGT2 having the temperature AT indicated by the temperature signal ST acquired in step S101 as the temperature coordinate value ATx and is equal to or less than the gain coordinate value AGy corresponding to a point on the curve LGT1 having the temperature AT indicated by the temperature signal ST acquired in step S101 as the temperature coordinate value ATx.

[0090] In this embodiment, the ink-compatible amplification information QGT is an example of the "first amplification information."

[0091] As shown in FIG. 10, the amplification factor setting unit 24 sets a provisional amplification factor AGP[m] based on the piezo driving count information SP generated in step S105 and the piezo corresponding amplification information QGP stored in the storage unit 6 (S109).

[0092] FIG. 12 is an explanatory diagram for explaining an example of the piezo-compatible amplification information QGP.

[0093] As shown in Fig. 12, the piezo-compatible amplification information QGP is information showing a curve LGP0 representing a combination of the amplification factor AG[m] and the piezo driving count AP[m] for maintaining the amplitude AK[m] of the detection signal SK[m] at the reference amplitude AK0 in a graph G-GP in which the horizontal axis represents the driving count coordinate value APx corresponding to the piezo driving count AP[m] and the vertical axis represents the amplification factor coordinate value AGy corresponding to the amplification factor AG[m]. Specifically, the piezo-compatible amplification information QGP is information showing the coordinates of each of a plurality of points on the curve LGP0 in the graph G-GP. For example, in Fig. 12, the point where the driving count coordinate value APx is the reference piezo driving count AP0 and the amplification factor coordinate value AGy is the reference amplification factor AGP0 is a point on the curve LGP0. Therefore, when the piezo drive count AP[m] becomes the reference piezo drive count AP0 and the amplification factor AG[m] becomes the reference amplification factor AGP0, the amplitude AK[m] of the detection signal SK[m] becomes the reference amplitude AK0.

[0094] Moreover, the piezo-compatible amplification information QGP is information indicating a curve LGP1 that represents a combination of the amplification factor AG[m] and the number of piezo drives AP[m] for maintaining the amplitude AK[m] of the detection signal SK[m] at the upper limit amplitude AK1. Specifically, the piezo-compatible amplification information QGP is information indicating the coordinates of each of a plurality of points on the curve LGP1 in the graph G-GP. Moreover, the piezo-compatible amplification information QGP is information indicating a curve LGP2 that represents a combination of the amplification factor AG[m] and the number of piezo drives AP[m] for maintaining the amplitude AK[m] of the detection signal SK[m] at the lower limit amplitude AK2. Specifically, the piezo-compatible amplification information QGP is information indicating the coordinates of each of a plurality of points on the curve LGP2 in the graph G-GP.

[0095] In step S109, the amplification factor setting unit 24 refers to the piezo-corresponding amplification information QGP to identify a point on the curve LGP0 having the piezo drive count AP[m] indicated by the piezo drive count information SP generated in step S105 as the drive count coordinate value APx. In this embodiment, the amplification factor setting unit 24 sets the amplification factor coordinate value AGy corresponding to the identified point on the curve LGP0 as the provisional amplification factor AGP[m]. In this embodiment, the amplification factor setting unit 24 sets the provisional amplification factor AGP[m] to a larger value when the piezo drive count AP[m] indicated by the piezo drive count information SP is a large value, compared to when it is a small value.

[0096] In this embodiment, the case where the gain coordinate value AGy corresponding to the point on the curve LGP0 is set as the provisional gain AGP[m] is illustrated, but the present invention is not limited to such an embodiment. For example, in step S109, the gain setting unit 24 may set, as the provisional gain AGP[m], a gain coordinate value AGy in a range that is equal to or greater than the gain coordinate value AGy corresponding to the point on the curve LGP2 having the piezo drive count AP[m] indicated by the piezo drive count information SP generated in step S105 as the drive count coordinate value APx, and is equal to or less than the gain coordinate value AGy corresponding to the point on the curve LGP1 having the piezo drive count AP[m] indicated by the piezo drive count information SP generated in step S105 as the drive count coordinate value APx.

[0097] In this embodiment, the piezo-compatible amplified information QGP is an example of the "second amplified information."

[0098] As shown in FIG. 10, the amplification factor setting unit 24 sets the amplification factor AG[m] based on the provisional amplification factor AGT[m] set in step S107 and the provisional amplification factor AGP[m] set in step S109 (S111).

[0099] Specifically, in step S111, the amplification factor setting unit 24 sets the amplification factor AG[m] based on the degree of difference between the provisional amplification factor AGT[m] and the reference amplification factor AGT0 and the degree of difference between the provisional amplification factor AGP[m] and the reference amplification factor AGP0. In addition, in step S111, the amplification factor setting unit 24 sets the amplification factor AG[m] to a larger value when the provisional amplification factor AGT[m] is larger than the reference amplification factor AGT0 compared to when it is small, and sets the amplification factor AG[m] to a larger value when the provisional amplification factor AGP[m] is larger than the reference amplification factor AGP0 compared to when it is small. In this embodiment, in step S111, the amplification factor setting unit 24 sets the amplification factor AG[m] based on, for example, the ratio of the provisional amplification factor AGT[m] to the reference amplification factor AGT0 and the ratio of the provisional amplification factor AGP[m] to the reference amplification factor AGP0. That is, in the present embodiment, in step S111, the amplification factor setting unit 24 sets the amplification factor AG[m] based on the following formula (1), for example. AG[m] = AG0×{AGT[m]÷AGT0}×{AGP[m]÷AGP0} …(1)

[0100] The reference amplification factor AG0 shown in formula (1) is an amplification factor AG[m] such that the amplitude AK[m] of the detection signal SK[m] becomes the reference amplitude AK0 when the temperature AT is the reference temperature AT0, the number of piezo drive times AP[m] is the reference piezo drive number AP0, and the amplification factor AG[m] is the reference amplification factor AG0. In the following, the right side of formula (1) "AG0×{AGT[m]÷AGT0}×{AGP[m]÷AGP0}" is referred to as the target amplification factor AGM[m].

[0101] In this embodiment, it is assumed that the detection circuit 33 can amplify the vibration signal VX[m] at an amplification factor AG[m] that is equal to or greater than the minimum amplification factor AG-min and equal to or less than the maximum amplification factor AG-max. For this reason, in step S111, the amplification factor setting unit 24 sets the amplification factor AG[m] to the minimum amplification factor AG-min if the following formula (2) is satisfied, sets the amplification factor AG[m] to the maximum amplification factor AG-max if the following formula (3) is satisfied, and sets the amplification factor AG[m] to the target amplification factor AGM[m] if neither the following formula (2) nor the following formula (3) is satisfied. AGM[m] < AG-min …(2) AG-max < AGM[m] …(3)

[0102] Next, the amplification factor setting unit 24 generates an amplification factor designation signal SG indicating the amplification factor AG[m], and supplies the generated amplification factor designation signal SG to the detection circuit 33 (S113).

[0103] Next, the amplification factor setting unit 24 determines whether or not the amplitude AK[m] of the detection signal SK[m] obtained when the detection circuit 33 amplifies the vibration signal VX[m] by the amplification factor AG[m] indicated by the amplification factor designation signal SG supplied in step S113 is included in a predetermined amplitude range (S115). Specifically, in step S115, the amplification factor setting unit 24 determines whether or not the amplification factor AG[m] set in step S111 is the target amplification factor AGM[m]. For example, in step S115, the amplification factor setting unit 24 may determine whether or not the following formula (4) is established. AG-min ≦ AGM[m] ≦ AG-max …(4)

[0104] If the result of the determination in step S115 is positive, the amplification factor setting unit 24 ends the amplification factor setting process. If the result of the determination in step S115 is negative, the amplification factor setting unit 24 sets the amplitude AC based on the amplification factor enhancement information QGC (S117). Note that in this embodiment, the amplitude AC is the potential difference between the potential VH1 and the potential VL1.

[0105] FIG. 13 is an explanatory diagram for explaining an example of the amplification factor enhancing information QGC.

[0106] As shown in FIG. 13, the amplification factor enhancement information QGC is information indicating a curve LGC0 representing a combination of the amplification factor AG[m] and the amplitude AC for maintaining the amplitude AK[m] of the detection signal SK[m] at the reference amplitude AK0 in a graph G-GC in which the horizontal axis represents the amplitude coordinate value ACx corresponding to the amplitude AC and the vertical axis represents the amplification factor coordinate value AGy corresponding to the amplification factor AG[m]. Specifically, the amplification factor enhancement information QGC is information indicating the coordinates of each of a plurality of points on the curve LGC0 in the graph G-GC. For example, in FIG. 13, the point where the amplitude coordinate value ACx becomes the reference amplitude AC0 and the amplification factor coordinate value AGy becomes the reference amplification factor AG0 is a point on the curve LGC0. Therefore, when the amplitude AC becomes the reference amplitude AC0 and the amplification factor AG[m] becomes the reference amplification factor AG0, the amplitude AK[m] of the detection signal SK[m] becomes the reference amplitude AK0.

[0107] Moreover, the amplification factor enhancement information QGC is information indicating a curve LGC1 that represents a combination of the amplification factor AG[m] and the amplitude AC for maintaining the amplitude AK[m] of the detection signal SK[m] at the upper limit amplitude AK1. Specifically, the amplification factor enhancement information QGC is information indicating the coordinates of each of a plurality of points on the curve LGC1 in the graph G-GC. Moreover, the amplification factor enhancement information QGC is information indicating a curve LGC2 that represents a combination of the amplification factor AG[m] and the amplitude AC for maintaining the amplitude AK[m] of the detection signal SK[m] at the lower limit amplitude AK2. Specifically, the amplification factor enhancement information QGC is information indicating the coordinates of each of a plurality of points on the curve LGC2 in the graph G-GC.

[0108] In step S117, the amplification factor setting unit 24 identifies a point on the curve LGC0 that has the amplification factor AG[m] set in step S111 as an amplification factor coordinate value AGy. Then, the amplification factor setting unit 24 sets the amplitude coordinate value ACx corresponding to the identified point on the curve LGC0 as the amplitude AC. Note that in this embodiment, the amplification factor setting unit 24 sets the amplitude AC to a larger value when the amplification factor AG[m] indicated by the amplification factor designation signal SG is a small value, compared to when it is a large value.

[0109] In this embodiment, the case where the amplitude coordinate value ACx corresponding to a point on the curve LGC0 is set as the amplitude AC is illustrated, but the present invention is not limited to such an embodiment. For example, in step S117, the amplification factor setting unit 24 may set, as the amplitude AC, an amplitude coordinate value ACx in a range that is equal to or greater than the amplitude coordinate value ACx corresponding to a point on the curve LGC2 having the amplification factor AG[m] set in step S111 as the amplification factor coordinate value AGy and is equal to or less than the amplitude coordinate value ACx corresponding to a point on the curve LGC1 having the amplification factor AG[m] set in step S111 as the amplification factor coordinate value AGy.

[0110] As shown in FIG. 10, the amplification factor setting unit 24 generates a drive waveform correction signal SC indicating the amplitude AC set in step S117, supplies the generated drive waveform correction signal SC to the drive control unit 21 (S119), and then terminates the amplification factor setting process.

[0111] <<5. Conclusion of the embodiment>> As described above, the inkjet printer 1 according to this embodiment includes a piezoelectric element PZ[m] driven by a drive signal Com, a cavity CV[m] filled with ink and whose volume changes in response to the driving of the piezoelectric element PZ[m], and a discharge unit D[m] including a nozzle N[m] that discharges liquid in the cavity CV[m] in response to the change in volume of the cavity CV[m], and a vibration signal VX[ the detection circuit 33 detecting the vibration signal VX[m] and generating a detection signal SK[m] based on the detected vibration signal VX[m]; and an amplification factor setting unit 24 setting an amplification factor AG[m] based on a temperature signal ST indicating a value related to the temperature of the ink ejected by the ejection section D[m] and piezo drive count information SP indicating a value related to the number of times the piezo element PZ[m] is driven, and the detection circuit 33 generates the detection signal SK[m] by amplifying the vibration signal VX[m] in accordance with the amplification factor AG[m] set by the amplification factor setting unit 24.

[0112] Thus, according to this embodiment, the detection circuit 33 generates the detection signal SK[m] by amplifying the vibration signal VX[m] according to the amplification factor AG[m] set by the amplification factor setting unit 24 based on the temperature signal ST and the piezo drive count information SP. Therefore, according to this embodiment, it is possible to generate a detection signal SK[m] that is more suitable for determining the ink ejection state at the ejection section D[m] than when the detection circuit 33 amplifies the vibration signal VX[m] at a constant amplification factor.

[0113] Furthermore, the inkjet printer 1 according to this embodiment is equipped with a judgment unit 5 which judges whether the ink ejection condition in the ejection section D[m] is normal or not by comparing the period TC[m] indicated by the detection signal SK[m] with some or all of threshold values ​​Tth1, Tth2, and Tth3, and is characterized in that the threshold values ​​Tth1, Tth2, and Tth3 include fixed reference values ​​whose values ​​do not change even if the ink temperature indicated by the temperature signal ST changes, and whose values ​​do not change even if the number of times the piezo element PZ[m] is driven, indicated by the piezo drive count information SP, changes.

[0114] Thus, according to this embodiment, since the thresholds Tth1, Tth2, and Tth3 are fixed reference values, it is possible to simplify the ejection state determination process compared to a configuration in which the thresholds Tth1, Tth2, and Tth3 are varied according to the temperature AT indicated by the temperature signal ST, or a configuration in which the thresholds Tth1, Tth2, and Tth3 are varied according to the piezo drive count AP[m] indicated by the piezo drive count information SP.

[0115] Furthermore, in the inkjet printer 1 according to this embodiment, the amplification factor setting unit 24 sets the amplification factor AG[m] based on the ink-compatible amplification information QGT indicating the amplification factor AG[m] of the vibration signal VX[m] required to keep the amplitude AK[m] of the detection signal SK[m] within a predetermined amplitude range when the ink temperature AT indicated by the temperature signal ST fluctuates.

[0116] Therefore, according to this embodiment, it is possible to generate a detection signal SK[m] suitable for the ejection state determination process.

[0117] Furthermore, in the inkjet printer 1 according to this embodiment, the amplification factor setting unit 24 sets the amplification factor AG[m] based on the piezo-compatible amplification information QGP indicating the amplification factor AG[m] of the vibration signal VX[m] required to keep the amplitude AK[m] of the detection signal SK[m] within a predetermined amplitude range when the piezo drive count AP[m] indicated by the piezo drive count information SP fluctuates.

[0118] Therefore, according to this embodiment, it is possible to generate a detection signal SK[m] suitable for the ejection state determination process.

[0119] Further, the inkjet printer 1 according to the present embodiment includes a drive signal generation unit 4 that generates a drive signal Com. The drive signal generation unit 4 corrects the amplitude AC of the drive signal Com so as to keep the amplitude AK[m] of the detection signal SK[m] within a predetermined amplitude range when the detection circuit 33 cannot keep the amplitude AK[m] of the detection signal SK[m] within the predetermined amplitude range even when amplifying the vibration signal VX[m].

[0120] Therefore, according to the present embodiment, a detection signal SK[m] suitable for the ejection state determination process can be generated.

[0121] Also, in the inkjet printer 1 according to the present embodiment, the temperature signal ST indicates the temperature AT of the ink ejected from the ejection unit D[m], and the amplification factor AG[m] is set to a larger value when the temperature AT indicated by the temperature signal ST is low compared to when it is high.

[0122] Therefore, according to the present embodiment, even when the temperature of the ink ejected from the ejection unit D[m] becomes low and the viscosity of the ink ejected from the ejection unit D[m] becomes high, it is possible to suppress a decrease in the amplitude AK[m] of the detection signal SK[m] and generate a detection signal SK[m] suitable for the ejection state determination process.

[0123] <<B. Modification Example>> Each of the above embodiments can be variously modified. Specific modification modes are exemplified below. Two or more modes arbitrarily selected from the following examples can be appropriately combined within a range where they do not conflict with each other. For elements in the modification examples exemplified below whose actions and functions are equivalent to those in the embodiment, the reference numerals referred to in the above description are reused, and the detailed description of each is appropriately omitted.

[0124] <<Modification Example 1>> In the above embodiment, the amplification factor setting unit 24 sets the amplification factor AG[m] without using the result information SH and the detection signal SK[m], but the present invention is not limited to such an embodiment. The amplification factor setting unit 24 may set the amplification factor AG[m] based on the amplitude information SH2[m] included in the result information SH or the detection signal SK[m].

[0125] FIG. 14 is a functional block diagram showing an example of the configuration of an inkjet printer 1B according to this modified example.

[0126] As shown in FIG. 14, the inkjet printer 1B differs from the inkjet printer 1 according to this embodiment in that it has a control unit 2B instead of the control unit 2, and in that it has a storage unit 6B instead of the storage unit 6. The storage unit 6B stores the ink-corresponding amplitude information QKT, the piezo-corresponding amplitude information QKP, and the control program PRG-B. The control unit 2B executes the control program PRG-B stored in the storage unit 6B and operates according to the control program PRG-B, thereby functioning as a drive control unit 21, a discharge control unit 22, a judgment management unit 23, an amplification factor setting unit 24B, and a transport control unit 25. That is, the control unit 2B differs from the control unit 2 according to the embodiment in that it includes the amplification factor setting unit 24B instead of the amplification factor setting unit 24.

[0127] FIG. 15 is a flowchart showing an example of the operation of the control unit 2B when the amplification factor setting process according to this modification is executed.

[0128] 15, when the amplification factor setting process is started, the amplification factor setting unit 24B acquires the result information SH from the judgment unit 5 and identifies the amplitude AK[m] indicated by the amplitude information SH2[m] included in the result information SH (S201). Note that in step S201, the amplification factor setting unit 24B may acquire the detection signal SK[m] instead of the amplitude information SH2[m] and identify the amplitude AK[m] based on the detection signal SK[m]. Hereinafter, the amplitude AK[m] identified by the amplification factor setting unit 24B in step S201 is referred to as the current amplitude AKr[m].

[0129] Next, the amplification factor setting unit 24B determines whether the current amplitude AKr[m] determined in step S201 is included in a predetermined amplitude range (S203). That is, in step S203, the amplification factor setting unit 24B determines whether the following formula (5) is satisfied. AK2 ≦ AKr[m] ≦ AK1 …(5)

[0130] If the result of the determination in step S203 is positive, the amplification factor setting unit 24B ends the amplification factor setting process. If the result of the determination in step S203 is negative, the amplification factor setting unit 24B acquires a temperature signal ST from the temperature sensor 35 (S205). Hereinafter, the temperature AT indicated by the temperature signal ST acquired by the amplification factor setting unit 24B in step S205 is referred to as a current temperature ATr.

[0131] Moreover, the amplification factor setting unit 24B acquires a designation signal SI from the discharge control unit 22 (S207). Then, the amplification factor setting unit 24B generates piezo drive count information SP indicating the piezo drive count AP[m] based on the designation signal SI acquired in step S207 (S209). Hereinafter, the piezo drive count AP[m] indicated by the piezo drive count information SP generated by the amplification factor setting unit 24B in step S207 is referred to as a current piezo drive count APr[m].

[0132] Next, the amplification factor setting unit 24B specifies a provisional amplitude AKT[m] and a provisional amplitude AKP[m] that satisfy the following formula (6) (S211). AK0 = AKr[m]×{AKT[m]÷AKr[m]}×{AKP[m]÷AKr[m]} …(6)

[0133] In addition, in step S211, when there are a plurality of combinations of the provisional amplitude AKT[m] and the provisional amplitude AKP[m], the amplification factor setting unit 24B may select any one combination from the plurality of combinations. For example, in step S211, the amplification factor setting unit 24B may select a combination that minimizes the evaluation value VL shown in the following formula (7) from among the plurality of combinations of the provisional amplitude AKT[m] and the provisional amplitude AKP[m]. VL = {AKT[m]} 2 +{AKP[m]} 2 …(7)

[0134] Next, the amplification factor setting unit 24B specifies a provisional amplification factor AGKT[m] corresponding to the provisional amplitude AKT[m] based on the ink-corresponding amplitude information QKT (S213).

[0135] FIG. 16 is an explanatory diagram for explaining an example of the ink-corresponding amplitude information QKT.

[0136] 16, the ink-corresponding amplitude information QKT is information indicating a curved surface CKT that indicates the amplitude AK[m] corresponding to the temperature AT indicated by the temperature signal ST and the amplification factor AG[m] indicated by the amplification factor designation signal SG in a three-dimensional graph G-KT, in which a first axis indicates a temperature coordinate value ATx corresponding to the temperature AT, a second axis indicates an amplification factor coordinate value AGy corresponding to the amplification factor AG[m], and a third axis indicates an amplitude coordinate value AKz corresponding to the amplitude AK[m]. Specifically, the ink-corresponding amplitude information QKT is information indicating the coordinates of each of a plurality of points on the curved surface CKT in the graph G-KT. For example, in FIG. 16, the amplification factor coordinate value AGy of a point on the curved surface CKT where the temperature coordinate value ATx is the current temperature ATr and the amplitude AK [m] is the current amplitude AKr [m] is the initial amplification factor AGr.

[0137] In step S213, the amplification factor setting unit 24B identifies the amplification factor coordinate value AGy of the point on the curved surface CKT where the temperature coordinate value ATx is the current temperature ATr and the amplitude AK[m] is the provisional amplitude AKT[m] as the provisional amplification factor AGKT[m].

[0138] Moreover, the amplification factor setting unit 24B specifies a provisional amplification factor AGKP[m] corresponding to the provisional amplitude AKP[m] based on the piezo-corresponding amplitude information QKP (S215).

[0139] FIG. 17 is an explanatory diagram for explaining an example of the piezo-corresponding amplitude information QKP.

[0140] 17, the piezo-corresponding amplitude information QKP is information indicating a curved surface CKP that indicates the piezo drive count AP[m] indicated by the piezo drive count information SP and the amplitude AK[m] corresponding to the amplification factor AG[m] indicated by the amplification factor designation signal SG in a three-dimensional graph G-KP in which a first axis indicates a drive count coordinate value APx corresponding to the piezo drive count AP[m], a second axis indicates an amplification factor coordinate value AGy corresponding to the amplification factor AG[m], and a third axis indicates an amplitude coordinate value AKz corresponding to the amplitude AK[m]. Specifically, the piezo-corresponding amplitude information QKP is information indicating the coordinates of each of a plurality of points on the curved surface CKP in the graph G-KP. For example, in FIG. 17, the amplification factor coordinate value AGy of a point on the curved surface CKP where the drive count coordinate value APx is the current piezo drive count APr[m] and the amplitude AK[m] is the current amplitude AKr[m], is the initial amplification factor AGr.

[0141] In step S215, the amplification factor setting unit 24B identifies the amplification factor coordinate value AGy of the point on the curved surface CKP whose drive count coordinate value APx is the current piezo drive count APr[m] and whose amplitude AK[m] is the provisional amplitude AKP[m] as the provisional amplification factor AGKP[m].

[0142] Next, the amplification factor setting unit 24B sets the amplification factor AG[m] based on the provisional amplification factor AGKT[m] determined in step S213 and the provisional amplification factor AGKP[m] determined in step S215 (S217).

[0143] Specifically, in step S217, the amplification factor setting unit 24B may set the amplification factor AG[m] based on the degree of difference between the provisional amplification factor AGKT[m] and the reference amplification factor AGT0 and the degree of difference between the provisional amplification factor AGKP[m] and the reference amplification factor AGP0. In addition, in step S217, the amplification factor setting unit 24B may set the amplification factor AG[m] to a larger value when the provisional amplification factor AGKT[m] is larger than the reference amplification factor AGT0 compared to a case where it is small, and may set the amplification factor AG[m] to a larger value when the provisional amplification factor AGKP[m] is larger than the reference amplification factor AGP0 compared to a case where it is small. In this modification, in step S217, the amplification factor setting unit 24B sets the amplification factor AG[m] based on the ratio of the provisional amplification factor AGKT[m] to the reference amplification factor AGT0 and the ratio of the provisional amplification factor AGKP[m] to the reference amplification factor AGP0. That is, in this modified example, the amplification factor setting unit 24B sets the amplification factor AG[m] based on the following formula (8) in step S217. AG[m] = AG0×{AGKT[m]÷AGT0}×{AGKP[m]÷AGP0} …(8)

[0144] Next, the amplification factor setting unit 24B generates an amplification factor designation signal SG indicating the amplification factor AG[m], supplies the generated amplification factor designation signal SG to the detection circuit 33 (S113), and ends the amplification factor setting process.

[0145] As described above, according to this modification, the detection circuit 33 amplifies the vibration signal VX[m] according to the amplification factor AG[m] set by the amplification factor setting unit 24B based on the temperature signal ST, the piezo drive count information SP, and the amplitude information SH2[m], thereby generating the detection signal SK[m]. Therefore, according to this modification, it is possible to generate a detection signal SK[m] that is more suitable for determining the ink ejection state at the ejection section D[m] than when the detection circuit 33 amplifies the vibration signal VX[m] at a constant amplification factor.

[0146] <<Variation 2>> In the above-described embodiment and modification 1, the head unit 3 is configured to include the supply circuit 31, the recording head 32, the detection circuit 33, and the temperature sensor 35, but the present invention is not limited to such an aspect. The head unit 3 may be configured to include components other than the supply circuit 31, the recording head 32, the detection circuit 33, and the temperature sensor 35. For example, the head unit 3 may be configured to include a determination unit 5.

[0147] <<Variation 3>> In the above-described embodiment and modified examples 1 and 2, it is assumed that the inkjet printer 1 has four head units 3, but the present invention is not limited to this embodiment. The inkjet printer 1 may have one to three head units 3, or may have five or more head units 3.

[0148] <<Variation 4>> In the above-described embodiment and modifications 1 to 3, the inkjet printer 1 is a serial printer, but the present invention is not limited to this. The inkjet printer 1 may be a so-called line printer in which the multiple nozzles N in the head unit 3 are arranged to extend wider than the width of the recording paper PP. [Explanation of symbols]

[0149] 1...inkjet printer, 2...control unit, 3...head unit, 4...drive signal generation unit, 5...judgment unit, 6...memory unit, 7...transport unit, 21...drive control unit, 22...ejection control unit, 23...judgment management unit, 24...amplification rate setting unit, 25...transport control unit, 31...supply circuit, 32...recording head, 33...detection circuit, 35...temperature sensor.

Claims

1. an ejection unit including a piezoelectric element that is driven by a drive signal, a pressure chamber that is filled with liquid and whose volume changes in response to the driving of the piezoelectric element, and a nozzle that ejects the liquid in the pressure chamber in response to the change in volume of the pressure chamber; a detection unit that detects a vibration signal indicating a potential of the piezoelectric element that varies in accordance with vibration remaining in the ejection unit after the piezoelectric element is driven, and generates a detection signal based on the detected vibration signal; a setting unit that sets a signal amplification factor based on liquid characteristic information related to the characteristics of the liquid ejected by the ejection unit and element characteristic information related to the characteristics of the piezoelectric element; Equipped with The detection unit generates the detection signal by amplifying the vibration signal in accordance with the signal amplification factor set by the setting unit. A liquid ejection device comprising:

2. a determination unit that determines whether or not a liquid ejection state in the ejection unit is normal by comparing a feature amount indicated by the detection signal with one or a plurality of reference values; the one or more reference values ​​include a fixed reference value whose value does not change even if the liquid characteristics indicated by the liquid characteristic information change, and whose value does not change even if the piezoelectric element characteristics indicated by the element characteristic information change. The liquid ejection device according to claim 1 .

3. the setting unit sets the signal amplification factor based on first amplification information indicating an amplification factor of the vibration signal required to keep the amplitude of the detection signal within a predetermined amplitude range when the liquid characteristic indicated by the liquid characteristic information varies. The liquid ejection device according to claim 1 .

4. The setting unit sets the signal amplification factor based on second amplification information indicating an amplification factor of the vibration signal required to keep the amplitude of the detection signal within a predetermined amplitude range when the characteristics of the piezoelectric element indicated by the element characteristic information fluctuate. The liquid ejection device according to claim 1 .

5. a drive signal generating unit that generates the drive signal, When the amplitude of the detection signal cannot be kept within a predetermined amplitude range even if the detection unit amplifies the vibration signal, the drive signal generation unit corrects a waveform of the drive signal so that the amplitude of the detection signal is kept within the predetermined amplitude range. The liquid ejection device according to claim 1 .

6. the liquid characteristic information indicates a temperature corresponding to a temperature of the liquid ejected by the ejection unit, the signal amplification rate is set to a larger value when the temperature indicated by the liquid property information is low compared to when the temperature is high; The liquid ejection device according to claim 1 .

7. an ejection unit including a piezoelectric element that is driven by a drive signal, a pressure chamber that is filled with liquid and whose volume changes in response to the driving of the piezoelectric element, and a nozzle that ejects the liquid in the pressure chamber in response to the change in volume of the pressure chamber; a detection unit that detects a vibration signal indicating a potential of the piezoelectric element that varies in accordance with vibration remaining in the ejection unit after the piezoelectric element is driven, and generates a detection signal based on the detected vibration signal; Equipped with the detection unit generates the detection signal by amplifying the vibration signal according to a signal amplification factor set based on liquid characteristic information relating to characteristics of the liquid ejected by the ejection unit and element characteristic information relating to characteristics of the piezoelectric element. A liquid ejection head comprising:

8. an ejection unit including a piezoelectric element driven by a drive signal, a pressure chamber filled with liquid and whose volume changes in response to the driving of the piezoelectric element, and a nozzle that ejects the liquid in the pressure chamber in response to the change in volume of the pressure chamber; A method for controlling a liquid ejection device comprising: After the piezoelectric element is driven, a vibration signal indicating a potential of the piezoelectric element that varies in accordance with a vibration remaining in the ejection portion is detected; setting a signal amplification factor based on liquid characteristic information relating to the characteristics of the liquid ejected by the ejection portion and element characteristic information relating to the characteristics of the piezoelectric element; a detection signal is generated by amplifying the vibration signal according to the signal amplification factor; A control method comprising:

9. determining whether or not a liquid ejection state in the ejection section is normal by comparing the characteristic amount indicated by the detection signal with one or a plurality of reference values; the one or more reference values ​​include a fixed reference value whose value does not change even if the liquid characteristics indicated by the liquid characteristic information change, and whose value does not change even if the piezoelectric element characteristics indicated by the element characteristic information change.

9. The control method according to claim 8.

10. setting the signal amplification factor based on first amplification information indicating an amplification factor of the vibration signal required to keep the amplitude of the detection signal within a predetermined amplitude range when the liquid characteristics indicated by the liquid characteristic information fluctuate.

9. The control method according to claim 8.

11. setting the signal amplification factor based on second amplification information indicating an amplification factor of the vibration signal required to keep the amplitude of the detection signal within a predetermined amplitude range when the characteristics of the piezoelectric element indicated by the element characteristic information fluctuate.

9. The control method according to claim 8.

12. When the amplitude of the detection signal cannot be kept within a predetermined amplitude range even if the vibration signal is amplified, correcting a waveform of the drive signal so that the amplitude of the detection signal is kept within the predetermined amplitude range; 9. The control method according to claim 8.

13. the liquid characteristic information indicates a temperature corresponding to a temperature of the liquid ejected by the ejection unit, When the temperature indicated by the liquid property information is low, the signal amplification factor is set to a larger value compared to when the temperature is high.

9. The control method according to claim 8.

Images