Liquid ejecting apparatus

Abstract

Provided is a liquid ejecting apparatus capable of immediately determining whether or not there is an abnormality in an ejection state, the liquid ejecting apparatus including: a first piezoelectric element driven by a drive signal; a first pressure chamber, the volume of which changes according to the displacement of the first piezoelectric element; a second piezoelectric element driven by the drive signal; a second pressure chamber, the volume of which changes according to the displacement of the second piezoelectric element; a nozzle flow path that communicates with the first pressure chamber and the second pressure chamber and is provided with a nozzle that ejects a liquid; and a determination unit. On the basis of a first detection signal showing a change in electromotive force of a first piezoelectric element in accordance with residual vibration of liquid generated in a first pressure chamber after driving at least one of the first piezoelectric element and a second piezoelectric element, and showing a change in electromotive force in accordance with residual vibration generated in liquid after driving at least the other of the first piezoelectric element and the second piezoelectric element, and on the basis of a second detection signal showing a change in electromotive force generated in accordance with residual vibration generated in liquid after driving at least the other of the first piezoelectric element and the second piezoelectric element The liquid ejection state from the nozzle is determined based on the difference between a second detection signal of a change in the electromotive force of the second piezoelectric element for residual vibration of the liquid in the second pressure chamber.

Description

Technical Field

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

[0002] A liquid ejection device typified by an inkjet printer has, for example, a nozzle that ejects a liquid, a pressure chamber that applies pressure to the liquid, and a piezoelectric element that applies pressure to the pressure chamber, as disclosed in Patent Document 1. In Patent Document 1, by driving the piezoelectric element, the pressure in the pressure chamber changes, and with this pressure change, ink is ejected from the nozzle.

[0003] In addition, the device described in Patent Document 1 detects the residual vibration waveform of the ink based on the vibration after supplying a drive signal to each pressure element as the electromotive force of each piezoelectric element, and determines whether there is an abnormality in the ink ejection state based on the detection result.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-189655

[0005] For example, a configuration in which a plurality of pressure chambers are provided for one nozzle and a plurality of piezoelectric elements are provided corresponding to the plurality of pressure chambers can be considered. In this case, by simultaneously driving the plurality of piezoelectric elements, the pressure in each of the plurality of pressure chambers changes, and with each of these pressure changes, ink is ejected from one nozzle. Thus, in a configuration in which a plurality of pressure chambers are provided for one nozzle, there is a problem that the signal shown by the detection result of the detected electromotive force is complex and it is difficult to determine whether there is an abnormality in the ejection state. Therefore, in the conventional device, it is difficult to immediately determine whether there is an abnormality in the ejection state, and the determination requires a certain amount of time. Summary of the Invention

[0006] In order to solve the above problems, a liquid ejection device according to a preferred aspect of the present invention includes: a first piezoelectric element driven by a drive signal; a first pressure chamber whose volume changes according to the displacement of the first piezoelectric element; a second piezoelectric element driven by the drive signal; a second pressure chamber whose volume changes according to the displacement of the second piezoelectric element; a nozzle flow path communicating with the first pressure chamber and the second pressure chamber and provided with a nozzle for ejecting a liquid; and a determination unit that determines the liquid ejection state from the nozzle based on the difference between a first detection signal and a second detection signal, the first detection signal showing a change in the electromotive force of the first piezoelectric element according to the residual vibration of the liquid generated in the first pressure chamber after at least one of the first piezoelectric element and the second piezoelectric element is driven, and the second detection signal showing a change in the electromotive force of the second piezoelectric element according to the residual vibration of the liquid generated in the second pressure chamber after at least the other of the first piezoelectric element and the second piezoelectric element is driven. Brief Description of the Drawings

[0007] Figure 1 It is a schematic diagram showing a configuration example of a liquid ejection device according to the first embodiment.

[0008] Figure 2 It is a block diagram showing the electrical configuration of the liquid ejection device according to the first embodiment.

[0009] Figure 3 It is a schematic diagram of a flow path in the liquid ejection head according to the first embodiment.

[0010] Figure 4 It corresponds to Figure 3 a diagram of the cross-section along line A-A in

[0011] Figure 5 It is a diagram showing a configuration example of the drive control unit of the first embodiment.

[0012] Figure 6 It is a diagram for explaining the waveform of the drive signal of the first embodiment.

[0013] Figure 7 It is a diagram for explaining the ejection operation and detection operation of the first embodiment.

[0014] Figure 8 It shows Figure 2 a diagram of the detection circuit and determination unit shown in

[0015] Figure 9 It is a diagram showing the first detection signal and the second detection signal in a normal state.

[0016] Figure 10 It shows Figure 9 a diagram of a determination signal, which is a signal related to the difference between the first detection signal and the second detection signal shown in

[0017] Figure 11 It is a diagram showing the first detection signal and the second detection signal in an abnormal state.

[0018] Figure 12 It shows Figure 11 a diagram of a determination signal, which is a signal related to the difference between the first detection signal and the second detection signal shown in

[0019] Figure 13 It is a diagram showing a configuration example of a drive circuit of a comparative example.

[0020] Figure 14 It is a diagram showing the determination signal in a normal state of the comparative example.

[0021] Figure 15 It is a diagram showing the determination signal in an abnormal state of the comparative example.

[0022] Figure 16 This is a diagram showing the determination unit of the second embodiment.

[0023] Figure 17 This is a diagram showing the determination unit of the third embodiment.

[0024] Figure 18 This is a diagram showing a configuration example of the drive control unit and the head chip of the fourth embodiment.

[0025] Description of Reference Numerals

[0026] 20... Liquid ejection head, 21... Control unit, 24... Head chip, 41... Piezoelectric element, 41a... First piezoelectric element, 41b... Second piezoelectric element, 45... Drive control unit, 47a... First detection piezoelectric element, 47b... Second detection piezoelectric element, 50... Determination unit, 51... Control unit, 54... Drive signal generation circuit, 55... Difference detection unit, 56... Difference determination unit, 100... Liquid ejection device, 551... Subtraction amplifier circuit, 552... Buffer circuit, 553... Amplifier circuit, 554... Phase delay circuit, A1... Operational amplifier, A2... Operational amplifier, A3... Operational amplifier, C... Pressure chamber, Ca... First pressure chamber, Cb... Second pressure chamber, Com... Drive signal, ComA... First drive signal, ComB... Second drive signal, L... Nozzle row, LHa... Wiring, LHb... Wiring, LHs... Wiring, LHt... Wiring, LHz... Wiring, N... Nozzle, Nf... Nozzle flow path, Nfa... Flow path, Nfb... Flow path, SL... Connection state designation signal, SW... Switch, Tu... Period, V1... First output signal, V2... Second output signal, Vin... Supply drive signal, Vo... Determination signal, Vout... Detection signal, Vout1... First detection signal, Vout2... Second detection signal, Zd1... First electrode, Zd2... First electrode, Zu1... Second electrode, Zu2... Second electrode, t1... Threshold value. Detailed Embodiments

[0027] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, in the drawings, the dimensions or scales of each part are appropriately different from the actual ones, and there are also parts schematically shown for easy understanding. In addition, the scope of the present invention is not limited to these embodiments as long as there is no description specifically limiting the meaning of the present invention in the following description.

[0028] In addition, the following description is appropriately made using mutually intersecting X-axis, Y-axis, and Z-axis. Further, one direction along the X-axis is referred to as the X1 direction, and the direction opposite to the X1 direction is referred to as the X2 direction. Similarly, the mutually opposite directions along the Y-axis are referred to as the Y1 direction and the Y2 direction. In addition, the mutually opposite directions along the Z-axis are referred to as the Z1 direction and the Z2 direction. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z-axis may not be a vertical axis. Further, the X-axis, Y-axis, and Z-axis typically intersect orthogonally, but are not limited thereto, and for example, they may intersect at an angle within the range of 80° or more and 100° or less.

[0029] A: First Embodiment

[0030] A1: Overall Configuration of Liquid Ejection Device

[0031] Figure 1 It is a schematic diagram showing a configuration example of a liquid ejection device 100 according to an embodiment. The liquid ejection device 100 is an inkjet printing device that ejects a liquid such as ink as droplets onto a medium 11. The medium 11 is, for example, printing paper. In addition, the medium 11 is not limited to printing paper, and for example, it may be a printing object of any material such as a resin film or cloth.

[0032] As Figure 1 shown, the liquid ejection device 100 includes a liquid container 12, a control unit 21, a conveyance mechanism 22, a moving mechanism 23, a liquid ejection head 20, and a circulation mechanism 26.

[0033] The liquid container 12 stores ink. As a specific form of the liquid container 12, for example, an ink cartridge that can be attached to and detached from the liquid ejection device 100, a bag-shaped ink bag made of a flexible film, and an ink tank that can replenish ink can be cited. In addition, the type of ink stored in the liquid container 12 is arbitrary.

[0034] The control unit 21 controls the operations of the respective elements of the liquid ejection device 100. The control unit 21 includes one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory.

[0035] The conveying mechanism 22 conveys the medium 11 in the Y1 direction under the control of the control unit 21. The moving mechanism 23 reciprocates the liquid ejection head 20 along the X-axis under the control of the control unit 21. The moving mechanism 23 includes a substantially box-shaped carriage 231 that houses the liquid ejection head 20 and an annular conveyor belt 232 fixed to the carriage 231. In addition, the number of liquid ejection heads 20 mounted on the carriage 231 is not limited to one and may be multiple. Further, in addition to the liquid ejection head 20, the above-described liquid container 12 may be mounted on the carriage 231.

[0036] Under the control of the control unit 21 based on the print data Img, the liquid ejection head 20 ejects the ink supplied from the liquid container 12 from each of the plurality of nozzles onto the medium 11. This ejection is performed in parallel with the conveyance of the medium 11 by the conveying mechanism 22 and the reciprocating movement of the liquid ejection head 20 by the moving mechanism 23, thereby forming an image corresponding to the print data Img based on the ink on the surface of the medium 11.

[0037] The liquid container 12 is connected to the liquid ejection head 20 via a circulation mechanism 26. The circulation mechanism 26 is a mechanism that supplies ink to the liquid ejection head 20 under the control of the control unit 21 and recovers the ink discharged from the liquid ejection head 20 for re-supplying it to the liquid ejection head 20. By the operation of the circulation mechanism 26, it is possible to suppress an increase in the viscosity of the ink or reduce the retention of air bubbles in the ink.

[0038] A2: Electrical Configuration of Liquid Ejection Device

[0039] Figure 2 It is a block diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment.

[0040] As Figure 2 shown, the liquid ejection head 20 includes a head chip 24, a drive control unit 45, and a detection circuit 46.

[0041] The head chip 24 has a plurality of piezoelectric elements 41. Specifically, the head chip 24 includes M first piezoelectric elements 41a driven by a drive signal Com and K second piezoelectric elements 41b driven by the drive signal Com. One nozzle N is provided for a group of one first piezoelectric element 41a and one second piezoelectric element 41b. Each piezoelectric element 41 has a function of applying pressure to the ink and a function of receiving pressure from the ink and outputting a detection signal Vout.

[0042] In addition, hereinafter, without particularly distinguishing between the first piezoelectric element 41a and the second piezoelectric element 41b, they are also referred to as "piezoelectric element 41". Further, hereinafter, in order to distinguish each of the M first piezoelectric elements 41a, the first piezoelectric element 41a is sometimes labeled as the first piezoelectric element 41a[m] using the subscript [m]. M is a natural number of 1 or more, and m is a natural number of 1 or more and M or less. Further, for the components or signals corresponding to the first piezoelectric element 41a[m], the correspondence with the first piezoelectric element 41a[m] is sometimes shown using the subscript [m]. Similarly, in order to distinguish each of the K second piezoelectric elements 41b, the second piezoelectric element 41b is sometimes labeled as the second piezoelectric element 41b[k] using the subscript [k]. K is a natural number of 1 or more, and k is a natural number of 1 or more and K or less. Further, for the components or signals corresponding to the second piezoelectric element 41b[k], the correspondence with the second piezoelectric element 41b[k] is sometimes shown using the subscript [k].

[0043] The drive control unit 45 drives the piezoelectric element 41 under the control of the control unit 21. In addition, the drive control unit 45 also serves as a switching circuit. Specifically, the drive control unit 45 controls the supply of the drive signal Com to each of the M first piezoelectric elements 41a and the K second piezoelectric elements 41b. The drive control unit 45 switches whether to supply the drive signal Com as the supply drive signal Vin to the piezoelectric element 41. In addition, the drive control unit 45 switches whether to supply the electromotive force of each of the M first piezoelectric elements 41a and the K second piezoelectric elements 41b as the detection signal Vout to the detection circuit 46.

[0044] The detection circuit 46 applies a bias voltage to the detection signal Vout indicating the change in the electromotive force of the piezoelectric element 41 that shows the residual vibration generated by the drive of each piezoelectric element 41. The residual vibration is the pressure vibration of the ink remaining in the pressure chamber C after the volume of the pressure chamber C changes due to the drive of the piezoelectric element 41.

[0045] As Figure 2 shown, the control unit 21 includes a control section 51, a storage section 52, a power supply circuit 53, a drive signal generation circuit 54, and a determination section 50.

[0046] The control unit 51 has the function of controlling the operations of the respective parts of the liquid ejecting device 100 and the function of processing various data. The control unit 51 controls the operations of the above-described drive control unit 45 and detection circuit 46. The control unit 51 includes, for example, one or more processors such as a CPU (Central Processing Unit). In addition, the control unit 51 may include a programmable logic device such as an FPGA (field-programmable gate array) instead of or in addition to the CPU. Further, in the case where the control unit 51 is composed of a plurality of processors, for example, the operation control of the drive control unit 45 and the operation control of the detection circuit 46 may be performed by different processors. Further, in the case where the control unit 51 is composed of a plurality of processors, the plurality of processors may be mounted on mutually different substrates or the like.

[0047] The storage unit 52 stores various programs executed by the control unit 51 and various data such as the print data Img processed by the control unit 51. The storage unit 52 includes, for example, a semiconductor memory including one or both of a volatile memory such as a RAM (Random Access Memory) and a non-volatile memory such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a PROM (Programmable ROM). The print data Img is supplied from an external device 200 such as a personal computer or a digital camera. Further, the storage unit 52 stores the detection signal Vout. In addition, the storage unit 52 may be configured as a part of the control unit 51.

[0048] The power supply circuit 53 receives power supply from a commercial power supply (not shown) and generates various prescribed potentials. The generated various potentials are appropriately supplied to the respective parts of the liquid ejecting device 100. For example, the power supply circuit 53 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the liquid ejection head 20. Further, the power supply potential VHV is supplied to the drive signal generation circuit 54.

[0049] The drive signal generation circuit 54 is a circuit that generates a drive signal Com for driving each piezoelectric element 41. Specifically, the drive signal generation circuit 54 has, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 54, the DA conversion circuit converts the waveform specification signal dCom from the control unit 51 from a digital signal to an analog signal, and the amplification circuit amplifies this analog signal using the power supply potential VHV from the power supply circuit 53 to generate the drive signal Com. The signal of the waveform actually supplied to the piezoelectric element 41 among the waveforms included in the drive signal Com is the above-described supply drive signal Vin. The waveform specification signal dCom is a digital signal for specifying the waveform of the drive signal Com.

[0050] The determination unit 50 determines the liquid ejection state as the state of ejecting ink from the nozzle N. Specifically, the determination unit 50 determines the liquid ejection state based on the detection signal Vout and generates determination information Stt indicating the determination result. The determination information Stt is used, for example, for control of ejecting ink from the nozzle during printing. Specifically, the determination information Stt is used, for example, for correction of the drive signal Com. In addition, the determination unit 50 may be configured as a part of the control unit 51. Also, part or all of the determination unit 50 may be provided in the liquid ejection head 20.

[0051] In the above control unit 21, the control unit 51 controls the operations of the respective parts of the liquid ejection device 100 by executing the program stored in the storage unit 52. By executing this program, the control unit 51 generates a control signal Sk1 and Sk2, a control signal SI, and a waveform specification signal dCom as signals for controlling the operations of the respective parts of the liquid ejection device 100.

[0052] The control signal Sk2 is a signal for controlling the drive of the conveyance mechanism 22. The control signal Sk1 is a signal for controlling the drive of the moving mechanism 23. The control signal SI is a digital signal for specifying the operation state of the piezoelectric element 41. In addition, the control signal SI includes a timing signal, that is, a latch signal LAT, and a change signal CH for specifying the drive timing of the piezoelectric element 41. This timing signal is generated, for example, based on the output of an encoder that detects the position of the carriage 231 described above.

[0053] A3: Flow path of the liquid ejection head

[0054] Figure 3 is a schematic diagram of the flow path in the head chip 24 according to the first embodiment. As Figure 3 shown, a plurality of nozzles N, a plurality of independent flow paths P, a first common liquid chamber R01, and a second common liquid chamber R02 are provided in the head chip 24.

[0055] A plurality of nozzles N are arranged along the Y-axis. Each nozzle N among the plurality of nozzles N ejects ink in the Z2 direction. The set of the plurality of nozzles N constitutes a nozzle row L. In addition, the plurality of nozzles N are arranged at equal intervals with a pitch θ. The pitch θ is the distance between the centers of the plurality of nozzles N in the direction along the Y-axis. Each nozzle N among the plurality of nozzles N is connected to an independent flow path P. Each independent flow path P among the plurality of independent flow paths P extends along the X-axis and is connected to a different nozzle N. In addition, the plurality of independent flow paths P are arranged along the Y-axis.

[0056] Each independent flow path P has a first pressure chamber Ca, a second pressure chamber Cb, and a nozzle flow path Nf. Each of the first pressure chamber Ca and the second pressure chamber Cb in each independent flow path P extends along the X-axis and is a space for storing the ink ejected from the nozzle N. The first pressure chamber Ca is provided for each first piezoelectric element 41a. The plurality of first pressure chambers Ca are arranged along the Y-axis. Each first pressure chamber Ca changes its volume according to the displacement of the first piezoelectric element 41a. Similarly, the second pressure chamber Cb is provided for each second piezoelectric element 41b. The plurality of second pressure chambers Cb are arranged along the Y-axis. Each second pressure chamber Cb changes its volume according to the displacement of the second piezoelectric element 41b.

[0057] In addition, in each independent flow path P, the positions of the first pressure chamber Ca and the second pressure chamber Cb in the direction along the Y-axis are Figure 3 the same as each other in the example shown. This sameness means that in addition to the completely identical case, it also includes the case where it can be regarded as the same if measurement errors are considered. In addition, hereinafter, without particularly distinguishing between the first pressure chamber Ca and the second pressure chamber Cb, it is also simply referred to as "pressure chamber C". In addition, a group of one first pressure chamber Ca and one second pressure chamber Cb is connected to one nozzle N via a nozzle flow path Nf.

[0058] A nozzle flow path Nf is arranged between the first pressure chamber Ca and the second pressure chamber Cb in each independent flow path P. In each independent flow path P, the nozzle flow path Nf mainly extends along the X-axis and is connected to the first pressure chamber Ca and the second pressure chamber Cb. A nozzle N for ejecting ink is provided in each nozzle flow path Nf. In addition, the plurality of nozzle flow paths Nf are arranged at intervals along the Y-axis. In each nozzle flow path Nf, ink is ejected from the nozzle N due to the pressure changes in the above-mentioned first pressure chamber Ca and second pressure chamber Cb.

[0059] The first common liquid chamber R01 and the second common liquid chamber R02 communicate with a plurality of independent flow paths P. Each of the first common liquid chamber R01 and the second common liquid chamber R02 is a space extending along the Y-axis over the entire range where a plurality of nozzles N are distributed. When viewed in the direction along the Z-axis, the above-mentioned plurality of independent flow paths P and the plurality of nozzles N are located between the first common liquid chamber R01 and the second common liquid chamber R02. In addition, hereinafter, viewing in the direction along the Z-axis is also referred to as "top view".

[0060] The first common liquid chamber R01 is connected to the end E1 in the X2 direction of each independent flow path P. Ink for supplying to each independent flow path P is stored in the first common liquid chamber R01. On the other hand, the second common liquid chamber R02 is connected to the end E2 in the X1 direction of each independent flow path P. Ink that is not used for ejection but is discharged from each independent flow path P is stored in the second common liquid chamber R02.

[0061] The first common liquid chamber R01 and the second common liquid chamber R02 are connected to a circulation mechanism 26. The circulation mechanism 26 is a mechanism that supplies ink to the first common liquid chamber R01 and recovers the ink discharged from the second common liquid chamber R02 for re-supplying to the first common liquid chamber R01. The circulation mechanism 26 includes a first supply pump 261, a second supply pump 262, a storage container 263, a recovery flow path 264, and a supply flow path 265.

[0062] The first supply pump 261 is a pump that supplies the ink stored in the liquid container 12 to the storage container 263. The storage container 263 is a sub-tank that temporarily stores the ink supplied from the liquid container 12. The recovery flow path 264 connects the second common liquid chamber R02 and the storage container 263 and is a flow path for recovering the ink from the second common liquid chamber R02 to the storage container 263. In addition to the ink stored in the liquid container 12 being supplied from the first supply pump 261 to the storage container 263, the ink discharged from each independent flow path P to the second common liquid chamber R02 is also supplied to the storage container 263 via the recovery flow path 264. The second supply pump 262 is a pump that sends out the ink stored in the storage container 263. The supply flow path 265 connects the first common liquid chamber R01 and the storage container 263 and is a flow path for supplying the ink from the storage container 263 to the first common liquid chamber R01.

[0063] A4: Specific structure of the liquid ejection head

[0064] Figure 4 is equivalent to Figure 3 the cross-sectional view taken along line A-A in Figure 4 which shows a cross-section of the head chip 24 cut by a plane parallel to the X-axis and the Z-axis along the independent flow path P. As shown in Figure 4As shown, the head chip 24 includes a flow path structure 30, a plurality of piezoelectric elements 41, a housing portion 42, a protective substrate 43, and a wiring substrate 44.

[0065] In the flow path structure 30, the above-described first common liquid chamber R01, second common liquid chamber R02, a plurality of independent flow paths P, and a plurality of nozzles N are provided. Specifically, the flow path structure 30 is a structure in which a nozzle substrate 31, a communication plate 33, a pressure chamber substrate 34, and a vibration plate 35 are laminated in the Z1 direction in sequence. Each member of the nozzle substrate 31, the communication plate 33, the pressure chamber substrate 34, and the vibration plate 35 extends along the Y axis and is manufactured, for example, by processing a single crystal substrate of silicon using semiconductor processing technology. In addition, these members are joined to each other by an adhesive or the like. Further, other layers or substrates such as an adhesive layer may be appropriately interposed between two adjacent members among the plurality of members constituting the flow path structure 30.

[0066] A plurality of nozzles N are provided in the nozzle substrate 31. Each nozzle N among the plurality of nozzles N penetrates the nozzle substrate 31 and is a through hole through which ink passes.

[0067] In the communication plate 33, a part of each of the first common liquid chamber R01 and the second common liquid chamber R02 and a part of the plurality of independent flow paths P other than the first pressure chamber Ca and the second pressure chamber Cb are provided. Each independent flow path P further includes a supply flow path Ra1 and a discharge flow path Ra2 in addition to the first pressure chamber Ca, the second pressure chamber Cb, and the nozzle flow path Nf. Among the elements constituting such an independent flow path P, the nozzle flow path Nf, the supply flow path Ra1, and the discharge flow path Ra2 are provided in the communication plate 33.

[0068] A part of each of the first common liquid chamber R01 and the second common liquid chamber R02 is a space that penetrates the communication plate 33. On the surface of the communication plate 33 facing the Z2 direction, vibration absorbers 361 and 362 that block the openings formed by this space are provided.

[0069] Each of the vibration absorbers 361 and 362 is a layered member made of an elastic material. The vibration absorber 361 forms a part of the wall surface of the first common liquid chamber R01 and absorbs pressure fluctuations in the first common liquid chamber R01. Similarly, the vibration absorber 362 forms a part of the wall surface of the second common liquid chamber R02 and absorbs pressure fluctuations in the second common liquid chamber R02.

[0070] As described above, the nozzle flow path Nf is a space that connects the first pressure chamber Ca and the second pressure chamber Cb. In Figure 4 the example shown, the nozzle flow path Nf has a flow path Nfa from the first pressure chamber Ca to the nozzle N and a flow path Nfb from the second pressure chamber Cb to the nozzle N. Each of the flow paths Nfa and Nfb is a space that extends along the Z axis and then along the X axis.

[0071] Each of the supply flow path Ra1 and the discharge flow path Ra2 extends along the Z-axis and is a space penetrating the communication plate 33. The supply flow path Ra1 connects the first common liquid chamber R01 to the first pressure chamber Ca and supplies the ink from the first common liquid chamber R01 to the first pressure chamber Ca. One end of the supply flow path Ra1 opens on the surface of the communication plate 33 facing the Z1 direction. In contrast, the other end of the supply flow path Ra1 is the upstream end E1 of the independent flow path P. On the other hand, the discharge flow path Ra2 connects the second common liquid chamber R02 to the second pressure chamber Cb and discharges the ink from the second pressure chamber Cb to the second common liquid chamber R02. One end of the discharge flow path Ra2 opens on the surface of the communication plate 33 facing the Z1 direction. In contrast, the other end of the discharge flow path Ra2 is the downstream end E2 of the independent flow path P.

[0072] The first pressure chamber Ca and the second pressure chamber Cb of a plurality of independent flow paths P are provided in the pressure chamber substrate 34. Each of the first pressure chamber Ca and the second pressure chamber Cb penetrates the pressure chamber substrate 34 and is the gap between the communication plate 33 and the vibration plate 35.

[0073] The vibration plate 35 is a plate-like member that can vibrate elastically. The vibration plate 35 is, for example, a laminate including a first layer made of silicon oxide (SiO 2 ), and a second layer made of zirconium oxide (ZrO 2 ). Other layers such as metal oxides may be interposed between the first layer and the second layer. In addition, part or all of the vibration plate 35 may be integrally formed of the same material as the pressure chamber substrate 34. For example, by selectively removing a part of the thickness direction in the region corresponding to the pressure chamber C in a plate-like member with a specified thickness, the vibration plate 35 and the pressure chamber substrate 34 can be integrally formed. Additionally, the vibration plate 35 may be formed of a single material layer.

[0074] On the surface of the vibration plate 35 facing the Z1 direction, a plurality of piezoelectric elements 41 corresponding to different pressure chambers C are provided. Specifically, a first piezoelectric element 41a corresponding to each first pressure chamber Ca and a second piezoelectric element 41b corresponding to each second pressure chamber Cb are provided. The first piezoelectric element 41a overlaps the first pressure chamber Ca when viewed from above. The second piezoelectric element 41b overlaps the second pressure chamber Cb when viewed from above.

[0075] Each piezoelectric element 41 is formed by laminating, for example, two electrodes facing each other and a piezoelectric body layer disposed between the two electrodes. Each piezoelectric element 41 causes the ink in the pressure chamber C to be ejected from the nozzle N by changing the pressure of the ink in the pressure chamber C. The piezoelectric element 41 vibrates the diaphragm 35 by deforming itself when a drive signal Com is supplied. Along with this vibration, the pressure chamber C expands and contracts, so that the pressure of the ink in the pressure chamber C changes.

[0076] The housing portion 42 is a housing for storing ink. In the housing portion 42, a space is provided for each of the first common liquid chamber R01 and the second common liquid chamber R02, which constitutes the remaining portion other than a part of the communication plate 33. In addition, a supply port 421 and a discharge port 422 are provided in the housing portion 42. The supply port 421 is a pipe communicating with the first common liquid chamber R01 and is connected to the supply flow path 265 of the circulation mechanism 26. Therefore, the ink sent from the second supply pump 262 to the supply flow path 265 is supplied to the first common liquid chamber R01 via the supply port 421. On the other hand, the discharge port 422 is a pipe communicating with the second common liquid chamber R02 and is connected to the recovery flow path 264 of the circulation mechanism 26. Therefore, the ink in the second common liquid chamber R02 is discharged to the recovery flow path 264 via the discharge port 422.

[0077] The protective substrate 43 is a plate-like member provided on the surface of the diaphragm 35 facing the Z1 direction, protecting a plurality of piezoelectric elements 41 while strengthening the mechanical strength of the diaphragm 35. A space for accommodating a plurality of piezoelectric elements 41 is formed between the protective substrate 43 and the diaphragm 35.

[0078] The wiring substrate 44 is mounted on the surface of the diaphragm 35 facing the Z1 direction and is a mounting component for electrically connecting the control unit 21 and the head chip 24. For example, a flexible wiring substrate 44 such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) can be suitably used. The above-mentioned drive control unit 45 is mounted on the wiring substrate 44. In addition, in the wiring substrate 44, in addition to the drive control unit 45, the above-mentioned detection circuit 46 can also be mounted.

[0079] When viewed in the Z2 direction, which is the direction in which the ink is ejected from the nozzle N, the drive control unit 45 is located between the first piezoelectric element 41a and the second piezoelectric element 41b. Therefore, compared with a configuration in which the drive control unit 45 is located at other positions, the supply path of the drive signal Com from the drive control unit 45 to both the first piezoelectric element 41a and the second piezoelectric element 41b can be shortened.

[0080] In the head chip 24 configured as described above, by supplying the drive signal Com, the first piezoelectric element 41a and the second piezoelectric element 41b are driven simultaneously, so that the pressures in the first pressure chamber Ca and the second pressure chamber Cb change, and ink is ejected from the nozzle N along with this pressure change. In Figure 4 the flow path and direction of the ink when the first piezoelectric element 41a and the second piezoelectric element 41b are driven simultaneously are shown by the dotted arrows.

[0081] In addition, in the head chip 24, through the operation of the above-described circulation mechanism 26, the ink circulates successively in the first common liquid chamber R01, the supply flow path Ra1, the first pressure chamber Ca, the nozzle flow path Nf, the second pressure chamber Cb, the discharge flow path Ra2, and the second common liquid chamber R02. In addition, the operation period or operation timing of the circulation mechanism 26 is arbitrary, and whether it repeats during the period or timing of ejecting ink from the nozzle N is also arbitrary.

[0082] By providing the circulation mechanism 26, it is possible to reduce the retention of the ink in the flow path between the supply flow path Ra1 and the discharge flow path Ra2. Therefore, it is possible to reduce the thickening of the ink near the nozzle N or the precipitation of components. As a result, it is possible to prevent deterioration of ejection characteristics such as the ejection amount or ejection speed of the ink in the head chip 24.

[0083] In addition, the connection method of the circulation mechanism 26 to the head chip 24 may be set to be opposite to the above-described connection method on the supply side and the discharge side. In this case, the supply flow path Ra1 functions as a discharge flow path for discharging ink from the first pressure chamber Ca, and the discharge flow path Ra2 functions as a supply flow path for supplying ink to the second pressure chamber Cb.

[0084] A5: Details of the drive control unit 45

[0085] Figure 5 is a diagram showing a configuration example of the drive control unit 45 of the first embodiment. The drive control unit 45 supplies the drive signal Com as the supply drive signal Vin to the piezoelectric element 41. In Figure 5 one of the two electrodes of the first piezoelectric element 41a[m] is shown as the first electrode Zu1[m], and the other electrode is shown as the second electrode Zd1[m]. One of the two electrodes of the second piezoelectric element 41b[k] is shown as the first electrode Zu2[k], and the other electrode is shown as the second electrode Zd2[k].

[0086] In addition, in Figure 5In the example shown, as the drive signal Com, the first drive signal ComA related to ink ejection and the second drive signal ComB related to micro-vibration of the ink in the nozzle N can be cited. Further, as the detection signal Vout, the first detection signal Vout1 and the second detection signal Vout2 can be cited.

[0087] As Figure 5 shown, the drive control unit 45 is connected to wirings LHz, LHa, LHb, LHs, and LHt. Further, the wirings LHs and LHt are connected to the determination unit 50 via the detection circuit 46. The wiring LHz is a power supply line for supplying the offset potential VBS. The wiring LHa is a signal line for transmitting the first drive signal ComA. The wiring LHb is a signal line for transmitting the second drive signal ComB. The wiring LHs is a signal line for transmitting the first detection signal Vout1. The wiring LHt is a signal line for transmitting the second detection signal Vout2.

[0088] The drive control unit 45 includes a plurality of switches SW and a connection state specifying circuit 451 for specifying the connection states of the plurality of switches. The plurality of switches SW includes M switches SWa (SWa[1] to SWa[M]), M switches SWb (SWb[1] to SWb[M]), K switches SWc (SWc[1] to SWd[K]), K switches SWd (SWd[1] to SWd[K]), M switches SWs (SWs[1] to SWs[M]), and K switches SWt (SWt[1] to SWt[K]). Each switch SW is, for example, a transmission gate.

[0089] The switch SWa[m] is a switch for switching the conduction (ON: connected) and non-conduction (OFF: disconnected) between the wiring LHa for transmitting the first drive signal ComA and the first piezoelectric element 41a[m]. The switch SWb[m] is a switch for switching the conduction (connected) and non-conduction (disconnected) between the wiring LHb for transmitting the second drive signal ComB and the first piezoelectric element 41a[m]. The switch SWc[k] is a switch for switching the conduction (connected) and non-conduction (disconnected) between the wiring LHa for transmitting the first drive signal ComA and the second piezoelectric element 41b[k]. The switch SWd[k] is a switch for switching the conduction (connected) and non-conduction (disconnected) between the wiring LHb for transmitting the second drive signal ComB and the second piezoelectric element 41b[k]. The switch SWs[m] is a switch for switching the conduction (connected) and non-conduction (disconnected) between the wiring LHs for transmitting the first detection signal Vout1 and the first piezoelectric element 41a[m]. The switch SWt[k] is a switch for switching the conduction (connected) and non-conduction (disconnected) between the wiring LHt for transmitting the second detection signal Vout2 and the second piezoelectric element 41b[k].

[0090] The first piezoelectric element 41a and the second piezoelectric element 41b are electrically connected to the wiring LHa via mutually different wirings. Similarly, the first piezoelectric element 41a and the second piezoelectric element 41b are electrically connected to the wiring LHb via mutually different wirings. In addition, the first piezoelectric element 41a and the second piezoelectric element 41b are electrically connected to the wiring LH for transmitting mutually different detection signals Vout.

[0091] The connection state specifying circuit 451 generates a connection state specifying signal SL for specifying the on / off states of the respective switches SW based on the control signal SI. As the connection state specifying signal SL, connection state specifying signals SLa[m], SLb[m], SLc[k], SLd[k], SLs[m], and SLt[k] can be cited.

[0092] The connection state specifying signal SLa[m] is a signal for specifying the on / off state of the switch SWa[m]. The switch SWa[m] becomes an on state when the connection state specifying signal SLa[m] is at a high level and becomes an off state when the connection state specifying signal SLa[m] is at a low level. The drive control unit 45 switches whether to supply a part or all of the waveform included in the first drive signal ComA as the supply drive signal Vin to the first piezoelectric element 41a[m] by switching the on / off state of the switch SWa[m].

[0093] The connection state specifying signal SLb[m] is a signal for specifying the on / off state of the switch SWb[m]. The switch SWb[m] becomes an on state when the connection state specifying signal SLb[m] is at a high level and becomes an off state when the connection state specifying signal SLb[m] is at a low level. The drive control unit 45 switches whether to supply a part or all of the waveform included in the second drive signal ComB as the supply drive signal Vin to the first piezoelectric element 41a[m] by switching the on / off state of the switch SWb[m].

[0094] The connection state specifying signal SLc[k] is a signal for specifying the on / off state of the switch SWc[k]. The switch SWc[k] becomes an on state when the connection state specifying signal SLc[k] is at a high level and becomes an off state when the connection state specifying signal SLc[k] is at a low level. The drive control unit 45 switches whether to supply a part or all of the waveform included in the first drive signal ComA as the supply drive signal Vin to the second piezoelectric element 41b[k] by switching the on / off state of the switch SWc[m].

[0095] The connection state specifying signal SLd[k] is a signal for specifying the on / off state of the switch SWd[k]. The switch SWd[k] becomes the on state when the connection state specifying signal SLd[k] is at a high level, and becomes the off state when the connection state specifying signal SLd[k] is at a low level. The drive control unit 45 switches whether to supply a part or all of the waveform included in the second drive signal ComB to the second piezoelectric element 41b[k] as the supply drive signal Vin by switching the on / off state of the switch SWd[k].

[0096] The connection state specifying signal SLs[m] is a signal for specifying the on / off state of the switch SWs[m]. The switch SWs[m] becomes the on state when the connection state specifying signal SLs[m] is at a high level, and becomes the off state when the connection state specifying signal SLs[m] is at a low level. The drive control unit 45 switches whether to enable the state in which the first detection signal Vout1 can be detected from the first piezoelectric element 41a[m] by switching the on / off state of the switch SWs[m].

[0097] The connection state specifying signal SLt[k] is a signal for specifying the on / off state of the switch SWt[k]. The switch SWt[k] becomes the on state when the connection state specifying signal SLt[k] is at a high level, and becomes the off state when the connection state specifying signal SLt[k] is at a low level. The drive control unit 45 switches whether to enable the state in which the second detection signal Vout2 can be detected from the second piezoelectric element 41b[k] by switching the on / off state of the switch SWt[k].

[0098] In the present embodiment, the periods during which the switch SWa[m] is on, the periods during which the switch SWb[m] is on, and the periods during which the switch SWs[m] is on do not overlap with each other. Similarly, the periods during which the switch SWc[k] is on, the periods during which the switch SWd[k] is on, and the periods during which the switch SWt[k] is on do not overlap with each other. In addition, in the present embodiment, the period during which the switch SWa[m] is on overlaps with the period during which the switch SWc[k] is on. The period during which the switch SWb[m] is on overlaps with the period during which the switch SWd[k] is on. The period during which the switch SWs[m] is on overlaps with the period during which the switch SWt[k] is on.

[0099] When the switch SWa[m] and the switch SWc[k] are turned on simultaneously to supply the same first drive signal ComA to the first piezoelectric element 41a and the second piezoelectric element 41b, the first piezoelectric element 41a and the second piezoelectric element 41b are driven simultaneously. As a result, the pressures in the first pressure chamber Ca and the second pressure chamber Cb change, and ink is ejected from the nozzle N. Further, when the switch SWb[m] and the switch SWd[k] are turned on simultaneously to supply the same second drive signal ComB to the first piezoelectric element 41a and the second piezoelectric element 41b, the first piezoelectric element 41a and the second piezoelectric element 41b are driven to perform micro-vibrations simultaneously. As a result, the pressures in the first pressure chamber Ca and the second pressure chamber Cb change, and the ink in the nozzle N performs micro-vibrations to such an extent that ink is not ejected from the nozzle N.

[0100] On the other hand, when the switches SWs[m] and SWt[k] are exclusively turned on, the ejection operation by the first piezoelectric element 41a and the second piezoelectric element 41b is not performed, and the first detection signal Vout1 and the second detection signal Vout2 are supplied to the determination unit 50 via the detection circuit 46. Then, in the determination unit 50, the liquid ejection state of the nozzle N is determined using the first detection signal Vout1 and the second detection signal Vout2.

[0101] In addition, switches SWe and SWf are provided between the drive control unit 45 and the detection circuit 46. The switch SWe is a switch that switches the conduction (turn-on) and non-conduction (turn-off) between the wiring LHa for transmitting the first drive signal ComA and the determination unit 50. The switch SWf is a switch that switches the conduction (turn-on) and non-conduction (turn-off) between the wiring LHb for transmitting the second drive signal ComB and the detection circuit 46. In addition, the switches SWe and SWf are electrically connected at the node N1. When the switches SWe and SWf are in a state where the detection signal Vout can be detected from the piezoelectric element 41, they are exclusively turned on.

[0102] When in a state where the detection signal Vout based on the remaining vibration after the supply of the first drive signal ComA can be detected, the drive control unit 45 sets the switch SWe to the on state and the switch SWf to the off state. In addition, when in a state where the detection signal Vout based on the remaining vibration after the supply of the second drive signal ComB can be detected, the drive control unit 45 sets the switch SWf to the on state and the switch SWe to the off state.

[0103] A6: Waveform of the drive signal Com

[0104] Figure 6 is a diagram for explaining the waveform of the drive signal Com of the first embodiment. As Figure 6As shown, the latch signal LAT includes a pulse PlsL for defining a repetition period Tu. The period Tu corresponds to a printing period for forming dots of ink from the nozzle N on the medium 11. The period Tu is defined, for example, as the period from the rise of the pulse PlsL to the rise of the next pulse PlsL. Further, the change signal CH includes a pulse PlsC for dividing the period Tu into a preceding control period Tua and a subsequent control period Tub. The control period Tua is, for example, the period from the rise of the pulse PlsL to the rise of the pulse PlsC. The control period Tub is, for example, the period from the rise of the pulse PlsC to the rise of the pulse PlsL.

[0105] The first drive signal ComA includes an ejection pulse P1. The ejection pulse P1 is set in the control period Tua. The ejection pulse P1 is a potential pulse that drives the piezoelectric element 41 in such a way as to generate a pressure change of an intensity that causes ink to be ejected from the nozzle N in the pressure chamber C. By supplying the ejection pulse P1 to the piezoelectric element 41, ink is ejected from the nozzle N as ink droplets. Specifically, for example, by supplying the first drive signal ComA to both the first piezoelectric element 41a and the second piezoelectric element 41b simultaneously, ink is ejected from the nozzle N as ink droplets.

[0106] In Figure 6 the example, the ejection pulse P1 is a waveform that drops from the reference potential E0 to the lowest potential EL1 lower than the reference potential E0, then rises to the highest potential EH1 higher than the reference potential E0, and then returns to the reference potential E0. Further, the reference potential E0 is, for example, a potential higher than the offset potential VBS. In addition, the potential in the control period Tub in the first drive signal ComA is the reference potential E0.

[0107] The second drive signal ComB has a non-ejection pulse P2. The non-ejection pulse P2 is set in the control period Tua. The non-ejection pulse P2 is a pulse that drives the piezoelectric element 41 in such a way as not to generate a pressure change of an intensity that causes ink to be ejected from the nozzle N in the pressure chamber C. By the non-ejection pulse P2 being supplied to the piezoelectric element 41, ink is not ejected from the nozzle N, and the meniscus of the ink in the nozzle N vibrates slightly. Specifically, for example, by the non-ejection pulse P2 being supplied to both the first piezoelectric element 41a and the second piezoelectric element 41b simultaneously, ink is not ejected from the nozzle N, and the meniscus vibrates slightly.

[0108] In Figure 6 the example, the non-ejection pulse P2 is a waveform that drops from the reference potential E0 to the lowest potential EL2 lower than the reference potential E0 and then returns to the reference potential E0. In addition, the potential in the control period Tub in the second drive signal ComB is the reference potential E0.

[0109] During the period when ink is not ejected from nozzle N, ink stagnation in nozzle N is likely to occur. When this period becomes long, there is a possibility of an increase in the viscosity of the ink in nozzle N. Therefore, during the period when ink is not ejected from nozzle N, the piezoelectric element 41 is driven so that the meniscus vibrates slightly to the extent that ink is not ejected from nozzle N. This micro-vibration is smaller than the vibration of the meniscus when ink is ejected. By this micro-vibration, the ink in nozzle N is agitated. Therefore, in combination with the action of the circulation mechanism 26 on the circulating flow of the ink, ink replacement is smoothly performed between nozzle N and the nozzle flow path Nf. Therefore, it is possible to prevent an increase in the viscosity of the ink in nozzle N and the like.

[0110] The control unit 51 controls the supply of the drive signal Com to each of the plurality of piezoelectric elements 41 based on the print data Img and for each cycle Tu in such a way as to be any one of an ejection period, a non-ejection period, and a detection signal output period. The ejection period is the period when ink is ejected from nozzle N by supplying the ejection pulse P1 of the first drive signal ComA. The non-ejection period is the period when, although ink is not ejected from nozzle N, the meniscus of nozzle N vibrates by supplying the non-ejection pulse P2 of the second drive signal ComB. The detection signal output period is a period corresponding to the control period Tub in the first drive signal ComA or the control period Tub in the second drive signal ComB, and is a period when the drive signal Com is not applied to the piezoelectric element 41 to make it operate, and a detection signal Vout showing a change in the electromotive force generated when the piezoelectric element 41 is displaced due to the pressure vibration of the liquid remaining in the pressure chamber C is transmitted through the wiring. The detection signal output period is also a period when the ejection state is determined by the determination unit 50.

[0111] In addition, based on the first drive signal ComA and the second drive signal ComB, or instead of the first drive signal ComA and the second drive signal ComB, a drive signal Com other than the first drive signal ComA and the second drive signal ComB may be provided. For example, a drive signal Com including pulses related to ink ejection other than the ejection pulse P1 may be provided. Also, a drive signal Com including pulses related to the micro-vibration of the meniscus other than the non-ejection pulse P2 may be provided. Moreover, for example, a drive signal Com including pulses for detecting a residual vibration signal may be provided.

[0112] A7: Ejection operation and detection operation

[0113] Figure 7 It is a diagram for explaining the ejection operation and detection operation of the first embodiment. In Figure 7In the example, during control period Tua, an ejection operation of ejecting ink from nozzle N is performed, and during control period Tub, a detection operation of the detection unit 50 detecting the detection signal Vout is performed. In Figure 7 In the example, control period Tua is the ejection period, and control period Tub is the detection signal output period.

[0114] For example, during control period Tua, each of the switches SWa[m] and SWc[k] is turned on, and each of the switches SWb[m], SWd[k], SWs[m], and SWt[k] is turned off. Additionally, during control period Ta, each of the switches SWe and SWf is turned off.

[0115] By such switching of the switches SW, ejection pulses P1 are simultaneously applied to both the first piezoelectric element 41a[m] and the second piezoelectric element 41b[k] during control period Ta. As a result, the first piezoelectric element 41a and the second piezoelectric element 41b are driven simultaneously, and ink is ejected from nozzle N.

[0116] Additionally, for example, during control period Tub, each of the switches SWs[m] and SWt[k] is turned on, and each of the switches SWa[m], SWb[m], SWc[k], SWd[k], and SWf is turned off. Additionally, during control period Tub, the switch SWe is turned on.

[0117] By such switching of the switches SW, a first detection signal Vout1 is output from the first piezoelectric element 41a[m], and a second detection signal Vout2 is output from the second piezoelectric element 41b[m]. Then, the determination unit 50 detects the change in the electromotive force of the piezoelectric element 41 according to the residual vibration of the ink in the pressure chamber C. That is, the determination unit 50 detects the first detection signal Vout1 and the second detection signal Vout2 passing through the detection circuit 46. Using these detection signals Vout, the determination unit 50 determines the liquid ejection state of the ink flowing in the independent flow path P provided in the head chip 24.

[0118] Furthermore, during control period Tua, non-ejection pulses P2 of the second drive signal ComB can also be simultaneously applied to both the first piezoelectric element 41a[m] and the second piezoelectric element 41b[k], and during control period Tub, the first detection signal Vout1 and the second detection signal Vout2 can also be detected. In this case, for the above Figure 7 In the example, during control period Tua, the switches SWb[m] and SWd[k] are set to be turned on, and the other switches SW are set to be turned off. During control period Tub, similar to the above Figure 7The same applies to the example. In this example, during the control period Tua, it is a non-ejection period in which micro-vibration operations are performed, and during the control period Tub, it is a detection signal output period.

[0119] A8: Detection circuit 46 and determination unit 50

[0120] Figure 8 is a diagram showing Figure 2 the detection circuit 46 and determination unit 50 shown. As Figure 8 shown, the detection circuit 46 includes detection resistors R5 and R6. One end of the detection resistor R5 is connected to a wiring LHs for transmitting a first detection signal Vout1, and the other end is electrically connected to a node N1. One end of the detection resistor R6 is connected to a wiring LHt for transmitting a second detection signal Vout2, and the other end is electrically connected to the node N1.

[0121] The detection resistors R5 and R6 function as bias resistors for supplying a driving signal Com of voltage to the voltage of the detection signal Vout. Therefore, by providing the detection circuit 46, a bias voltage is applied to the first detection signal Vout1 and the second detection signal Vout2.

[0122] The determination unit 50 determines the liquid ejection state from the nozzle N based on the difference between the first detection signal Vout1 and the second detection signal Vout2. The first detection signal Vout1 shows the change in the electromotive force of the first piezoelectric element 41a according to the residual vibration of the ink generated in the first pressure chamber Ca after at least one of the first piezoelectric element 41a and the second piezoelectric element 41b is driven. The second detection signal Vout2 shows the change in the electromotive force of the second piezoelectric element 41b according to the residual vibration of the ink generated in the second pressure chamber Cb after at least one of the first piezoelectric element 41a and the second piezoelectric element 41b is driven. In addition, in the present embodiment, the first piezoelectric element 41a and the second piezoelectric element 41b are driven simultaneously.

[0123] The determination unit 50 includes a difference detection unit 55 and a difference determination unit 56. The first detection signal Vout1 and the second detection signal Vout2 are input to the difference detection unit 55. Then, the difference detection unit 55 outputs a signal related to the difference between the first detection signal Vout1 and the second detection signal Vout2, that is, a determination signal Vo.

[0124] The difference detection unit 55 includes a subtraction amplifier circuit 551 and a buffer circuit 552. The subtraction amplifier circuit 551 is a circuit that amplifies the difference between the first detection signal Vout1 and the second detection signal Vout2. The subtraction amplifier circuit 551 includes resistors R1, R2, R3, R4 and an operational amplifier A1. The relationship between resistor R1 and R3 is R1 = R3, and the relationship between resistor R2 and R4 is R2 = R4. In this case, the determination signal Vo output from the difference detection unit 55 is shown by the following formula.

[0125] Vo = R2 / R1 (V in+ − V in- )

[0126] Therefore, the difference detection unit 55 amplifies the difference between the first detection signal Vout1 and the second detection signal Vout2.

[0127] The buffer circuit 552 is, for example, a voltage follower using an operational amplifier A2.

[0128] Based on the determination signal Vo, the difference determination unit 56 determines the liquid ejection state from the nozzle N and generates determination information Stt indicating the determination result. For example, when the amplitude of the determination signal Vo exceeds the threshold value, the difference determination unit 56 determines that the liquid ejection state has become defective. On the other hand, when the amplitude of the determination signal Vo is below the threshold value, the difference determination unit 56 determines that the liquid ejection state is normal.

[0129] A9: Example of determination of liquid ejection state

[0130] Figure 9 is a diagram showing the first detection signal Vout1 and the second detection signal Vout2 in a normal state. In Figure 9 , the waveform W1 of the first detection signal Vout1 in a normal state is shown by a solid line. The waveform W2 of the second detection signal Vout2 in a normal state is shown by a dashed line. As Figure 9 shown, in a normal state, the waveform W1 of the first detection signal Vout1 and the waveform W2 of the second detection signal Vout2 are substantially equal and overlap.

[0131] Figure 10 is a diagram showing the determination signal Vo, which is a signal related to the difference between the first detection signal Vout1 and the second detection signal Vout2 shown in Figure 9 . In Figure 10 , the waveform W01 of the determination signal Vo is shown by a solid line. Since Figure 9 the waveform W1 of the first detection signal Vout1 and the waveform W2 of the second detection signal Vout2 shown in

[0132] In addition, a threshold value t1 is shown in Figure 10 . As described above, during normal times, the amplitude of the difference between the first detection signal Vout1 and the second detection signal Vout2 is substantially zero. Thus, this difference is below the threshold value. In addition, being below the threshold value means below the absolute value of the threshold value t1. When the amplitude of the determination signal Vo is below the threshold value, the difference determination unit 56 determines that the liquid ejection state is normal.

[0133] Figure 11 is a diagram showing the first detection signal Vout1 and the second detection signal Vout2 during an abnormality. In Figure 11 , the waveform W3 of the first detection signal Vout1 during an abnormality is shown by a solid line. The waveform W4 of the second detection signal Vout2 during an abnormality is shown by a dotted line.

[0134] As Figure 11 shown, during an abnormality, the waveform W3 of the first detection signal Vout1 and the waveform W4 of the second detection signal Vout2 are different from each other. When there is an abnormality in the liquid ejection state, the first piezoelectric element 41a and the second piezoelectric element 41b show different waveforms. For example, as Figure 11 shown, the waveform W3 of the first detection signal Vout1 and the waveform W4 of the second detection signal Vout2 are different from each other.

[0135] Figure 12 is a diagram showing the determination signal Vo, which is a signal related to the difference between the first detection signal Vout1 and the second detection signal Vout2 shown in Figure 11 . In Figure 12 , the waveform W02 of the determination signal Vo is shown by a solid line. Since Figure 11 the waveform W3 of the first detection signal Vout1 and the waveform W4 of the second detection signal Vout2 shown are different from each other, the amplitude of the difference between the first detection signal Vout1 and the second detection signal Vout2 shows the Figure 12 shown waveform W02. In Figure 12 , the amplitude of the waveform W02 has a portion exceeding the threshold value t1. When the amplitude of the determination signal Vo exceeds the threshold value t1, the difference determination unit 56 determines that the liquid ejection state is abnormal.

[0136] From Figure 10 and Figure 12 it is also understood that by determining whether the determination signal Vo based on the difference between the first detection signal Vout1 and the second detection signal Vout2 is within the threshold value t1, it is possible to simply and quickly determine the liquid ejection state from the nozzle N. Therefore, it is possible to immediately discriminate an abnormality.

[0137] In this way, the determination unit 50 of the present embodiment determines the liquid ejection state from the nozzle N based on the difference between the first detection signal Vout1 and the second detection signal Vout2. By providing this determination unit 50, in the configuration of a plurality of pressure chambers C in which the first pressure chamber Ca and the second pressure chamber Cb are provided with respect to one nozzle N, it is possible to immediately and simply determine whether the liquid ejection state is abnormal.

[0138] In addition, by driving the first piezoelectric element 41a and the second piezoelectric element 41b with the same drive signal Com, it is not necessary to determine whether each of the first detection signal Vout1 and the second detection signal Vout2 is residual vibration after being supplied with any one of the first drive signal ComA and the second drive signal ComB. Since the determination is made based on the difference between the first detection signal Vout1 and the second detection signal Vout2, it is possible to immediately and simply make a determination even when any drive signal is supplied to the first piezoelectric element 41a and the second piezoelectric element 41b.

[0139] In addition, in the present embodiment, the natural vibration period of the flow path Nfa from the first pressure chamber Ca to the nozzle N is equal to the natural vibration period of the flow path Nfb from the second pressure chamber Cb to the nozzle N. When the head chip 24 is configured such that the natural vibration frequencies in the flow path Nfa and the flow path Nfb become equal, as described above, normally, the amplitude of the signal of the difference between the first detection signal Vout1 and the second detection signal Vout2 is 0 (zero) or close to 0 (zero). Therefore, it is possible to easily and accurately determine whether the liquid ejection state is abnormal. In addition, the fact that the natural vibration frequencies in the flow path Nfa and the flow path Nfb are equal to each other means that, in addition to the case of being exactly equal, it also includes the case where they can be regarded as equal when measurement errors are considered.

[0140] In addition, as described above, the determination unit 50 includes: a difference determination unit 56 that outputs a determination signal Vo, which is a signal related to the difference between the first detection signal Vout1 and the second detection signal Vout2; and a difference determination unit 56 that determines the liquid ejection state according to whether the level of the determination signal Vo is within the threshold t1. Therefore, by using a simple configuration in which the difference determination unit 56 determines whether the difference between the first detection signal Vout1 and the second detection signal Vout2 is within the threshold t1, it is possible to simply determine whether there is an abnormality in the ejection state.

[0141] Figure 13 FIG. is a configuration example diagram of the drive control unit 45x showing a comparative example. In the present embodiment, the first piezoelectric element 41a and the second piezoelectric element 41b are electrically connected to different wirings LHs and LHt for transmitting the detection signal Vout. In contrast, in Figure 13In the comparative example shown, the first piezoelectric element 41a and the second piezoelectric element 41b are electrically connected to the same wiring LHs for transmitting the detection signal Vout. Therefore, in the comparative example, the signal obtained by superimposing the first detection signal Vout1 and the second detection signal Vout2 is input to the determination unit 50.

[0142] Figure 14 FIG. is a diagram showing the determination signal Vo in the comparative example in the normal state. In Figure 14 it shows Figure 9 the waveform W04 of the determination signal Vo of the comparative example, which is the signal obtained by superimposing the first detection signal Vout1 and the second detection signal Vout2 shown. When the first detection signal Vout1 and the second detection signal Vout2 are superimposed, Figure 14 the amplitude of the waveform W04 is larger than Figure 9 the respective amplitudes of the waveforms W1 and W2.

[0143] Figure 15 FIG. is a diagram showing the determination signal Vo in the comparative example in the abnormal state. In Figure 15 it shows Figure 11 the waveform W05 of the determination signal Vo of the comparative example, which is the signal obtained by superimposing the first detection signal Vout1 and the second detection signal Vout2 shown.

[0144] In the comparative example, whether in the normal state or the abnormal state, it exceeds the threshold value t1. Therefore, in the comparative example, it is necessary to determine the parameter that is characteristic in the discrimination between normal and abnormal. For example, as the parameter that is characteristic in the discrimination, the amplitude or period of the determination signal Vo can be used. In order to obtain this parameter, a detection time of more than one vibration period of the determination signal Vo is required. In addition, when the waveform of the drive signal Com changes, the amplitude value of the determination signal Vo also changes. Therefore, it is necessary to determine whether the waveforms W04 and W05 are residual vibrations when any drive signal Com is supplied. In addition, in the comparative example, since the waveform of the determination signal Vo is the signal obtained by superimposing the first detection signal Vout1 and the second detection signal Vout2, the change of the signal is complicated, and it is difficult to immediately determine the liquid ejection state.

[0145] On the other hand, in the present embodiment, the first piezoelectric element 41a and the second piezoelectric element 41b are connected to wirings for transmitting detection signals Vout that are different from each other. Specifically, the first piezoelectric element 41a is electrically connected to the wiring LHs, and the second piezoelectric element 41b is electrically connected to the wiring LHt. Thus, by connecting the first piezoelectric element 41a and the second piezoelectric element 41b to wirings for transmitting detection signals Vout that are different from each other, the first detection signal Vout1 and the second detection signal Vout2 can be detected with different signals respectively. Therefore, even during a period that does not satisfy one vibration cycle of the detection signal, it is possible to immediately determine the liquid ejection state as described above based on the difference between the first detection signal Vout1 and the second detection signal Vout2 detected simultaneously or in parallel.

[0146] In addition, in the present embodiment, as described above, the drive control unit 45 supplies the drive signal Com to the first piezoelectric element 41a and the second piezoelectric element 41b simultaneously. Then, the first detection signal Vout1 and the second detection signal Vout2 are input to the determination unit 50 simultaneously. Therefore, it is possible to immediately and highly accurately determine the liquid ejection state based on the first detection signal Vout1 and the second detection signal Vout2 detected simultaneously.

[0147] In addition, in the above description, the liquid ejection state is determined based on the residual vibration after the ejection pulse P1 in which the first drive signal ComA is supplied to the first piezoelectric element 41a and the second piezoelectric element 41b. However, it is also possible to determine the liquid ejection state based on the residual vibration after the non-ejection pulse P2 in which the second drive signal ComB is supplied to both the first piezoelectric element 41a and the second piezoelectric element 41b. In addition, it is also possible to determine the liquid ejection state based on the residual vibration after a pulse of a drive signal Com other than the first drive signal ComA and the second drive signal ComB. Even in these cases, the liquid ejection state from the nozzle N is determined based on the difference between the first detection signal Vout1 and the second detection signal Vout2 detected after the first piezoelectric element 41a and the second piezoelectric element 41b are driven by the same pulse. Therefore, it is possible to simply and immediately determine the liquid ejection state.

[0148] 2. Second Embodiment

[0149] For elements that function or operate in the same manner as those in the above-described first embodiment in the following exemplified manner, the reference numerals used in the description of the above-described first embodiment are adopted, and their respective detailed descriptions are appropriately omitted.

[0150] Figure 16 is a diagram showing the determination unit 50A of the second embodiment. As Figure 16As shown, the difference detection unit 55A of the determination unit 50A of the present embodiment further includes an amplifier circuit 553. The amplifier circuit 553 is provided between the detection circuit 46 and the subtraction amplifier circuit 551. The amplifier circuit 553 amplifies the amplitudes of the first detection signal Vout1 and the second detection signal Vout2. The amplifier circuit 553 includes resistors R7, R8, operational amplifiers A3 and A4. In the amplifier circuit 553, when the input signals are the first detection signal Vout1 and the second detection signal Vout2, and the output signals are the first output signal V1 and the second output signal V2, the respective output signals are represented by the following equations.

[0151] V1 = (R7 / R8) Vout1

[0152] V2 = (R7 / R8) Vout2

[0153] In the present embodiment, as described above, the determination unit 50A includes an amplifier circuit 553 that amplifies the amplitudes of both the first detection signal Vout1 and the second detection signal Vout2. By providing this amplifier circuit 553, even when there is a difference in amplitude between the first detection signal Vout1 and the second detection signal Vout2 during normal operation due to the flow path structure or the like, these signals can be adjusted so that the difference in amplitude between the first output signal V1 and the second output signal V2 used for determination during normal operation becomes smaller. Therefore, even in the case of a flow path structure in which the first detection signal Vout1 and the second detection signal Vout2 are normal and there is a difference in amplitude, it is possible to immediately and highly accurately determine the liquid ejection state using the difference between the first output signal V1 and the second output signal V2 whose amplitudes have been adjusted.

[0154] In addition, in the present embodiment, the amplifier circuit 553 amplifies the amplitudes of both the first detection signal Vout1 and the second detection signal Vout2, but it is also possible to amplify either one to match the other.

[0155] 3. Third Embodiment

[0156] For elements that act or function in the same manner as those in the above-described first embodiment in the following exemplified manner, the reference numerals used in the description of the above-described first embodiment are used, and their respective detailed descriptions are appropriately omitted.

[0157] Figure 17 is a diagram showing the determination unit 50B of the third embodiment. As Figure 17As shown, the difference detection unit 55B of the determination unit 50B of the present embodiment further includes a phase delay circuit 554. The phase delay circuit 554 is provided between the detection circuit 46 and the subtraction amplifier circuit 551. The phase delay circuit 554 is a circuit that delays the phase of at least one of the first detection signal Vout1 and the second detection signal Vout2 so that the phase of the first detection signal Vout1 matches the phase of the second detection signal Vout2.

[0158] In the first embodiment, the first detection signal Vout1 and the second detection signal Vout2 are simultaneously input to the determination unit 50, and the phase of the first detection signal Vout1 matches the phase of the second detection signal Vout2. In contrast, for example, there are cases where the input of the first detection signal Vout1 and the second detection signal Vout2 to the determination unit 50 is not simultaneous, or due to the influence of the structure and circuit, the phase of the first detection signal Vout1 and the phase of the second detection signal Vout2 shift. In this case, the phase of the first detection signal Vout1 is different from the phase of the second detection signal Vout2, and even if the liquid ejection state is normal, a difference is generated between the first detection signal Vout1 and the second detection signal Vout2. Even in this case, by providing the phase delay circuit 554 that matches the phase of the first detection signal Vout1 with the phase of the second detection signal Vout2, the difference between the first detection signal Vout1 and the second detection signal Vout2 can be set below the threshold value during normal times. Therefore, it is possible to immediately and highly accurately determine the liquid ejection state using the difference between the first detection signal Vout1 and the second detection signal Vout2.

[0159] 4. Fourth Embodiment

[0160] For elements that act or function in the same manner as those in the first embodiment in the following exemplified manner, the reference numerals used in the description of the first embodiment are used, and their respective detailed descriptions are appropriately omitted.

[0161] Figure 18 is a diagram showing a configuration example of the drive control unit 45C and the head chip 24C of the fourth embodiment. As Figure 18 shown, the head chip 24C of the present embodiment independently has a first detection piezoelectric element 47a and a second detection piezoelectric element 47b with respect to the first piezoelectric element 41a and the second piezoelectric element 41b. The first detection piezoelectric element 47a detects the vibration of the ink in the first pressure chamber Ca. The second detection piezoelectric element 47b detects the vibration of the ink in the second pressure chamber Cb.

[0162] The first piezoelectric element 41a corresponds to the "first piezoelectric element for driving". The second piezoelectric element 41b corresponds to the "second piezoelectric element for driving". During the ejection period or the non-ejection period, the first piezoelectric element 41a and the second piezoelectric element 41b are driven by a driving signal Com to cause a pressure change in the pressure chamber C that is strong enough to eject ink from the nozzle N, or to cause a pressure change in the pressure chamber C that is not strong enough to eject ink from the nozzle N. During the detection signal output period, a detection signal Vout indicating a change in the electromotive force generated when the first detection piezoelectric element 47a and the second detection piezoelectric element 47b are displaced is transmitted to the wiring.

[0163] As Figure 18 shown, the first detection piezoelectric element 47a and the second detection piezoelectric element 47b are electrically connected to wirings for transmitting detection signals Vout that are different from each other. Therefore, similar to the first embodiment, the determination unit 50 determines the liquid ejection state from the nozzle N based on the difference between the first detection signal Vout1 and the second detection signal Vout2. By providing this determination unit 50, in a configuration in which a plurality of pressure chambers C including a first pressure chamber Ca and a second pressure chamber Cb are provided for one nozzle N, it is possible to immediately and simply determine whether the liquid ejection state is abnormal.

[0164] In addition, although not shown in detail, the first detection piezoelectric element 47a overlaps with the first pressure chamber Ca in a plan view and is provided on the surface of the diaphragm 35 facing the Z1 direction. The first detection piezoelectric element 47a is provided adjacent to the first piezoelectric element 41a. Similarly, the second detection piezoelectric element 47b overlaps with the second pressure chamber Cb in a plan view and is provided on the surface of the diaphragm 35 facing the Z1 direction. The second detection piezoelectric element 47b is provided adjacent to the second piezoelectric element 41b. Each of the first detection piezoelectric element 47a and the second detection piezoelectric element 47b is composed of a laminate of two electrodes facing each other and a piezoelectric layer disposed between the two electrodes.

[0165] The rigidity of the first piezoelectric element 47a for detection is preferably higher than that of the first piezoelectric element 41a. Similarly, the rigidity of the second piezoelectric element 47b for detection is preferably higher than that of the second piezoelectric element 41b. By setting the relationship of the rigidities in this way, by providing the first piezoelectric element 47a for detection, the natural vibration period of the flow path Nfa becomes longer, and the possibility of a decrease in the driving frequency of the first piezoelectric element 41a can be suppressed. Similarly, by providing the second piezoelectric element 47b for detection, the natural vibration period of the flow path Nfb becomes longer, and the possibility of a decrease in the driving frequency of the second piezoelectric element 41b can be suppressed. In addition, by increasing the rigidities of the first piezoelectric element 47a for detection and the second piezoelectric element 47b for detection, the displacement caused by residual vibration becomes smaller, and the amplitude of the detection signal Vout also becomes smaller. Therefore, the detection signal Vout can also be appropriately amplified, and the accuracy of determination can be improved in the liquid ejection state based on the difference.

[0166] 5. Modification Example

[0167] The various modes exemplified above can be modified in various ways. Specific modification modes applicable to the above-mentioned various modes are exemplified as follows. The modes that can be arbitrarily selected from the following examples can be appropriately combined within a non-conflicting range.

[0168] 5A. First Modification Example

[0169] For example, the first detection signal Vout1 and the second detection signal Vout2 may also be stored in the storage unit 52, and the liquid ejection state may be determined based on the first detection signal Vout1 and the second detection signal Vout2 stored in the storage unit 52.

[0170] Specifically, the drive control unit 45 supplies a drive signal Com only to one of the first piezoelectric element 41a and the second piezoelectric element 41b. After supplying the drive signal Com only to this one piezoelectric element, the storage unit 52 stores the first detection signal Vout1. Similarly, the drive control unit 45 supplies a drive signal Com only to the other one of the first piezoelectric element 41a and the second piezoelectric element 41b. After supplying the drive signal Com only to this other piezoelectric element, the storage unit 52 stores the second detection signal Vout2. The determination unit 50 determines the liquid ejection state from the nozzle N based on the difference between the first detection signal Vout1 stored in the storage unit 52 and the second detection signal Vout2 stored in the storage unit 52.

[0171] By pre-storing the detection signal Vout in the storage unit 52, for example, when it is necessary to determine the liquid ejection state, the liquid ejection state from the nozzle N can be immediately determined.

[0172] 5B. Other Modification Examples

[0173] In each of the above-described modes, a configuration in which ink used in a liquid ejection head is circulated by a circulation mechanism is exemplified, but the configuration is not limited thereto, and a configuration without a mechanism for such circulation may also be used.

[0174] In each of the above-described modes, a serial liquid ejection device 100 in which a carriage 231 carrying a head chip 24 reciprocates is exemplified, but the present invention is also applicable to a line-type liquid ejection device in which a plurality of nozzles N are distributed over the entire width of a medium 11.

[0175] The liquid ejection device 100 exemplified in the above-described mode can be adopted in various devices such as a facsimile machine or a copying machine in addition to a device dedicated to printing, and the use of the present invention is not particularly limited. However, the use of the liquid ejection device is not limited to printing. For example, a liquid ejection device that ejects a solution of a coloring material is used as a manufacturing device for a color filter of a display device such as a liquid crystal display panel. In addition, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wirings or electrodes of a wiring substrate. In addition, a liquid ejection device that ejects a solution of an organic substance related to a living body is used, for example, as a manufacturing device for manufacturing a biochip.

Claims

1. A liquid ejection device, characterized in that: have: A first piezoelectric element driven by a driving signal; a first pressure chamber whose volume changes according to the displacement of the first piezoelectric element; A second piezoelectric element driven by the driving signal; a second pressure chamber whose volume changes according to the displacement of the second piezoelectric element; a nozzle flow path, communicating with the first pressure chamber and the second pressure chamber, and provided with a nozzle for spraying liquid; as well as The determination unit determines the liquid ejection state from the nozzle based on the difference between a first detection signal and a second detection signal, wherein the first detection signal indicates a change in the electromotive force of the first piezoelectric element according to the residual vibration of the liquid generated in the first pressure chamber after at least one of the first piezoelectric element and the second piezoelectric element is driven, and the second detection signal indicates a change in the electromotive force of the second piezoelectric element according to the residual vibration of the liquid generated in the second pressure chamber after at least the other of the first piezoelectric element and the second piezoelectric element is driven.

2. The liquid ejection device according to claim 1, wherein: A natural vibration period of a flow path from the first pressure chamber to the nozzle is equal to a natural vibration period of a flow path from the second pressure chamber to the nozzle.

3. The liquid ejection device according to claim 1, wherein: The determination unit comprises: a difference detection unit, which receives the first detection signal and the second detection signal as input and outputs a signal related to the difference between the first detection signal and the second detection signal; as well as The difference determination unit determines the liquid discharge state from the nozzle based on whether the level of the signal related to the difference is within a threshold value.

4. The liquid ejection device according to claim 3, wherein: The liquid ejection device further includes a drive control unit that controls supply of the drive signal to the first piezoelectric element and the second piezoelectric element. The drive control unit supplies the drive signal to the first piezoelectric element and the second piezoelectric element simultaneously. The first detection signal and the second detection signal are simultaneously input to the difference detection section.

5. The liquid ejection device according to claim 3, wherein: The difference detection unit includes an amplifier circuit that amplifies the amplitude of at least one of the first detection signal and the second detection signal.

6. The liquid ejection device according to claim 3, wherein: The difference detection unit includes a phase delay circuit that delays the phase of at least one of the first detection signal and the second detection signal to match the phase of the first detection signal with the phase of the second detection signal.

7. The liquid ejection device according to claim 1, wherein: The liquid ejection device further comprises: a drive control unit that controls supply of the drive signal to the first piezoelectric element and the second piezoelectric element; and a storage unit storing the first detection signal and the second detection signal, The drive control unit supplies the drive signal to only one of the first piezoelectric element and the second piezoelectric element. The storage unit stores the first detection signal according to residual vibration of the liquid in the first pressure chamber generated after the drive signal is supplied to only one of the first piezoelectric element and the second piezoelectric element, The drive control unit supplies the drive signal to only the other of the first piezoelectric element and the second piezoelectric element. The storage unit stores the second detection signal according to the residual vibration of the liquid in the second pressure chamber generated after the drive signal is supplied to only the other of the first piezoelectric element and the second piezoelectric element, The determination unit determines a liquid ejection state from the nozzle based on a difference between the first detection signal stored in the storage unit and the second detection signal stored in the storage unit.

8. A liquid ejection device, characterized in that: have: A first driving piezoelectric element driven by a driving signal; a first pressure chamber whose volume changes according to the displacement of the first driving piezoelectric element; a first detection piezoelectric element for detecting vibration of liquid in the first pressure chamber; A second driving piezoelectric element driven by the driving signal; a second pressure chamber whose volume changes according to the displacement of the second piezoelectric element; a second detection piezoelectric element for detecting vibration of the liquid in the second pressure chamber; a nozzle flow path, communicating with the first pressure chamber and the second pressure chamber, and provided with a nozzle for spraying liquid; as well as The determination unit determines the liquid ejection state from the nozzle based on the difference between a first detection signal and a second detection signal, wherein the first detection signal indicates a change in the electromotive force of the first detection piezoelectric element according to the residual vibration of the liquid generated in the first pressure chamber after at least one of the first driving piezoelectric element and the second driving piezoelectric element is driven, and the second detection signal indicates a change in the electromotive force of the second detection piezoelectric element according to the residual vibration of the liquid generated in the second pressure chamber after at least the other of the first driving piezoelectric element and the second driving piezoelectric element is driven.

9. The liquid ejection device according to claim 8, wherein: The rigidity of the first detection piezoelectric element is higher than the rigidity of the first driving piezoelectric element. The second detection piezoelectric element has higher rigidity than the second driving piezoelectric element.

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