Liquid discharge apparatus and method for acquiring deterioration state of liquid discharge apparatus

Abstract

To more accurately estimate the degree of deterioration of a liquid ejection head.SOLUTION: A liquid discharge apparatus includes a liquid discharge head including a nozzle that discharges a liquid, a pressure chamber, and a piezoelectric body that applies a pressure to the liquid in the pressure chamber to discharge the liquid from the nozzle, a voltage application circuit that applies a voltage to the piezoelectric body, and an acquisition unit 241 that acquires a degree of deterioration of the piezoelectric body based on information on an integral value of a current generated when the voltage applied to the piezoelectric body is gradually changed from a first voltage to a second voltage.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection device having a liquid ejection head that ejects liquid from a nozzle, and a method for acquiring the deterioration state of a liquid ejection device. [Background technology]

[0002] 2. Description of the Related Art A liquid ejection apparatus, typified by an ink jet recording apparatus such as an ink jet printer, is equipped with a liquid ejection head capable of ejecting liquid such as ink stored in a cartridge or tank as droplets.

[0003] A liquid ejection head ejects liquid from a pressure chamber as droplets from a nozzle by flexing and deforming a part of the pressure chamber, such as a diaphragm, using a piezoelectric element. The amount of displacement of the diaphragm caused by the piezoelectric element deteriorates as droplets are repeatedly ejected. Therefore, the voltage applied to the piezoelectric element is corrected according to the degree of decrease in the amount of displacement, so that the amount of displacement is equal to the amount of displacement before deterioration. Since the degree of deterioration is influenced by the number of times the piezoelectric element ejects droplets, the number of ejections is counted and the degree of deterioration is estimated based on the number of ejections (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-66948 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in addition to the number of ejections, the temperature of the environment in which the droplets are ejected and the voltage applied to the piezoelectric element also contribute to the degree of deterioration, so there is a risk that the degree of deterioration cannot be accurately determined by simply estimating the degree of deterioration based on the number of ejections, as in Patent Document 1. [Means for solving the problem]

[0006] An aspect of the present invention that solves the above problem is a liquid ejection device characterized by having a liquid ejection head including a nozzle that ejects liquid, a pressure chamber, and a piezoelectric element that applies pressure to the liquid in the pressure chamber to eject the liquid from the nozzle, a voltage application circuit that applies a voltage to the piezoelectric element, and an acquisition unit that acquires the degree of deterioration of the piezoelectric element based on information regarding the integral value of the current generated when the voltage applied to the piezoelectric element is gradually changed from a first voltage to a second voltage.

[0007] Another aspect of the present invention is a liquid ejection device comprising a liquid ejection head having a nozzle for ejecting liquid, a pressure chamber, and a piezoelectric element that applies pressure to the liquid in the pressure chamber to eject the liquid from the nozzle, a voltage application circuit that applies voltage to the piezoelectric element, and an acquisition unit that acquires the degree of deterioration of the piezoelectric element based on information regarding the maximum strain or residual strain of the piezoelectric element.

[0008] Another aspect of the present invention is a method for obtaining the deterioration state of a liquid ejection device that includes a nozzle for ejecting liquid, a pressure chamber, and a piezoelectric element that applies pressure to the liquid in the pressure chamber to eject the liquid from the nozzle, the method comprising: applying a voltage that is gradually changed from a first voltage to a second voltage to the piezoelectric element; integrating the current generated by the application of the voltage to obtain information relating to the integrated value; and obtaining the degree of deterioration of the piezoelectric element based on the information. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the appearance of a liquid ejection device according to a first embodiment. [Figure 2] 1 is a diagram showing a schematic configuration of a liquid ejection device according to a first embodiment. [Figure 3] 1 is a cross-sectional view of a liquid ejection head according to a first embodiment. [Figure 4] 1 is a block diagram showing the electrical configuration of a liquid ejection device according to a first embodiment. [Figure 5] 2 is a block diagram showing a function realization section of a control unit according to the first embodiment. FIG. [Figure 6] FIG. 3 is a waveform diagram showing an example of a drive signal according to the first embodiment. [Figure 7] FIG. 10 is a diagram showing the relationship between parameters and deterioration rate (dr). [Figure 8] FIG. 10 is a diagram showing a butterfly curve in a piezoelectric actuator. [Figure 9] 1 is a hysteresis loop showing the relationship between the voltage and current of a piezoelectric actuator. [Figure 10] FIG. 10 is a diagram showing linearity before and after endurance testing. [Figure 11] FIG. 10 is a diagram showing the correspondence relationship between the driving time of the piezoelectric actuator and the deterioration rate. [Figure 12] 10 is a flowchart illustrating a method for acquiring a deterioration rate of a liquid ejection device. [Figure 13] FIG. 2 is a diagram showing a screen of the display device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below based on embodiments. However, the following description illustrates one aspect of the present invention and can be modified as desired within the scope of the present invention. In each drawing, the same reference numerals indicate the same components, and their description will be omitted as appropriate. In each drawing, X, Y, and Z represent three spatial axes that are orthogonal to each other. In this specification, the directions along these axes are referred to as the X direction, Y direction, and Z direction. In each drawing, the direction indicated by the arrow is the positive (+) direction, and the direction opposite the arrow is the negative (-) direction. The Z direction indicates the vertical direction, the +Z direction indicates a vertically downward direction, and the -Z direction indicates a vertically upward direction. Furthermore, the directions of the three spatial axes, which are not limited to positive and negative directions, will be described as the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0011] (Embodiment 1) 1 is an external view of a liquid ejection device 1 according to a first embodiment of the present invention, and FIG. As shown in the figure, the liquid ejection device 1 is a so-called serial printer that includes a liquid ejection head H and prints by conveying a medium S in the X-axis direction while moving the liquid ejection head H back and forth in the Y-axis direction, ejecting liquid from the liquid ejection head H toward the medium S in the +Z direction. Note that the medium S can be made of any material, such as cloth, recording paper, or resin film.

[0012] The liquid ejection device 1 comprises a liquid ejection head H, a liquid storage section 3, a control unit 4 which is a control section, a transport mechanism 5 which feeds out the medium S, a moving mechanism 6, and a housing 2 which houses these components.

[0013] The liquid ejection head H ejects liquid supplied from a liquid storage section 3 that stores the liquid as droplets in the +Z direction.

[0014] The liquid storage unit 3 individually stores multiple types of liquid with different colors and components to be ejected from the liquid ejection head H. Examples of the liquid storage unit 3 include a cartridge that is detachable from the liquid ejection device 1, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. FIG. 2 shows one liquid storage unit 3 as an example. The liquid storage unit 3 may be a liquid storage unit 3 having separate chambers that individually store multiple types of liquid, or may be multiple liquid storage units 3 provided individually for the multiple types of liquid. The liquid storage unit 3 may also be divided into a main tank and a sub-tank. The sub-tank may be connected to the liquid ejection head H, and the liquid consumed by ejecting droplets from the liquid ejection head H may be replenished from the main tank to the sub-tank.

[0015] The control unit 4 comprehensively controls each element of the liquid ejection device 1, that is, the liquid ejection head H, the transport mechanism 5, the moving mechanism 6, and the like.

[0016] The transport mechanism 5 transports the medium S in the X-axis direction and has a transport roller 5a. The transport mechanism 5 transports the medium S in the X-axis direction by rotating the transport roller 5a. The transport roller 5a is rotated by driving a transport motor (not shown). The control unit 4 controls the driving of the medium transport motor, thereby controlling the transport of the medium S. Note that the transport mechanism 5 that transports the medium S is not limited to one that includes the transport roller 5a, and may transport the medium S by, for example, a belt or a drum.

[0017] The movement mechanism 6 is a mechanism for reciprocating the liquid ejection head H in the Y-axis direction, and includes a holder 7 and a conveyor belt 8. The holder 7 is a so-called carriage that holds the liquid ejection head H, and is fixed to the conveyor belt 8. The conveyor belt 8 is an endless belt that is installed along the Y-axis direction. The conveyor belt 8 is rotated by the drive of a drive motor (not shown). The control unit 4 controls the drive of the conveyor motor to rotate the conveyor belt 8, and moves the liquid ejection head H back and forth in the Y-axis direction together with the holder 7. The holder 7 may be configured to mount a liquid storage unit 3 together with the liquid ejection head H.

[0018] The housing 2 has an operation panel 9 fixed to its outer periphery. The operation panel 9 includes a display device 9a, which is an example of a display unit, and an operation device 9b, which is an example of a reception unit that receives user input. The display device 9a is configured, for example, with a liquid crystal display, an organic EL display, an LED lamp, or the like, and displays various information. The operation device 9b is configured with various switches that can receive input from the user. Examples of the switches of the operation device 9b include a direction switch that controls the cursor position, a confirmation switch that makes a decision, a cancel switch, and a power switch. The display device may be a touch panel that can receive user input. In the case of a touch panel, the touch panel serves as both the display unit and the reception unit.

[0019] The liquid ejection head H performs an ejection operation in which the liquid supplied from the liquid storage section 3 is ejected as droplets in the +Z direction from each of the multiple nozzles 21 (see FIG. 3) under the control of the control unit 4. This ejection operation by the liquid ejection head H is performed in parallel with the transport of the medium S by the transport mechanism 5 and the reciprocating movement of the liquid ejection head H by the movement mechanism 6, thereby applying the liquid to the medium S, or so-called printing.

[0020] 3 is a cross-sectional view of the liquid ejection head H. Note that the directions of the liquid ejection head H will be described based on the directions when it is mounted on the liquid ejection device 1, that is, the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0021] As shown in the figure, the liquid ejection head H includes a flow path forming substrate 10, a communication plate 15, a nozzle plate 20 having a plurality of nozzles 21 formed therein, a protective substrate 30, a case member 40, and a piezoelectric actuator 300.

[0022] The flow path forming substrate 10 is made of, for example, a silicon substrate, a glass substrate, an SOI substrate, or various ceramic substrates. In the flow path forming substrate 10, a plurality of pressure chambers 12 are arranged side by side along the X-axis direction. The plurality of pressure chambers 12 are arranged on a straight line along the X-axis direction so as to be at the same position in the Y-axis direction. In this embodiment, two pressure chamber rows are provided in the Y-axis direction, each row having the pressure chambers 12 arranged side by side along the X-axis direction. The pressure chambers 12 constituting these two pressure chamber rows are arranged at the same position in the X-axis direction. Note that the two pressure chamber rows may be arranged with a shift of half the pitch of the pressure chambers 12, i.e., a so-called half pitch, from each other in the X-axis direction. In other words, all of the pressure chambers 12 in the two pressure chamber rows may be arranged in a staggered pattern along the X-axis direction.

[0023] A communication plate 15 and a nozzle plate 20 are sequentially stacked on the surface of the flow path forming substrate 10 facing the +Z direction. A vibration plate 50 and a piezoelectric actuator 300 are sequentially stacked on the surface of the flow path forming substrate 10 facing the -Z direction.

[0024] The communication plate 15 is made of a plate-like member bonded to the surface of the flow channel forming substrate 10 facing the +Z direction. The communication plate 15 is provided with nozzle communication passages 16 that connect the pressure chambers 12 and the nozzles 21. The communication plate 15 is also provided with a first manifold portion 17 and a second manifold portion 18 that constitute part of a manifold 100 that serves as a common liquid chamber through which multiple pressure chambers 12 communicate. The first manifold portion 17 is provided to penetrate the communication plate 15 in the Z-axis direction. The second manifold portion 18 is provided to open on the surface facing the +Z direction without penetrating the communication plate 15 in the Z-axis direction. The communication plate 15 is also provided with supply communication passages 19 that communicate with the pressure chambers 12, independently for each pressure chamber 12. The supply communication passages 19 connect the second manifold portion 18 and the pressure chambers 12, and supply ink from the manifold 100 to the pressure chambers 12. Such a communication plate 15 may be a silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, or a metal substrate such as a stainless steel substrate.

[0025] The nozzle plate 20 is bonded to the side of the communication plate 15 opposite to the flow path forming substrate 10, i.e., the surface facing the +Z direction. A plurality of nozzles 21 are formed in the nozzle plate 20, which communicate with each pressure chamber 12 via nozzle communication passages 16. In this embodiment, a plurality of nozzles 21 are arranged in a line along the X-axis direction for each pressure chamber row. That is, in this embodiment, two nozzle rows, each having the nozzles 21 arranged side by side along the X-axis direction, are provided, spaced apart in the Y-axis direction. The nozzles 21 constituting these two nozzle rows are arranged so as to be at the same position in the X-axis direction. Of course, when the two pressure chamber rows are arranged at positions shifted from each other by half a pitch of the pressure chambers 12 in the X-axis direction, the two nozzle rows may also be similarly shifted from each other by half a pitch of the nozzles 21 in the X-axis direction. That is, all of the nozzles 21 in the two nozzle rows may be arranged in a staggered pattern along the X-axis direction.

[0026] A silicon substrate, a glass substrate, an SOI substrate, various ceramic substrates, a metal substrate such as a stainless steel substrate, an organic substrate such as a polyimide resin, etc. are used for such a nozzle plate 20. The surface of the nozzle plate 20 facing the +Z direction forms part of the ejection surface of the liquid ejection head H.

[0027] In this embodiment, the vibration plate 50 has an elastic film 51 made of silicon oxide provided on the flow path forming substrate 10 side, and an insulating film 52 made of zirconium oxide provided on the surface facing the -Z direction of the elastic film 51. The vibration plate 50 may be composed of only the elastic film 51, or may be composed of only the insulating film 52, or may have a configuration including other films in addition to the elastic film 51 and the insulating film 52.

[0028] The piezoelectric actuator 300 includes a first electrode 60, a piezoelectric layer 70, and a second electrode 80, which are sequentially stacked on the vibration plate 50 in the -Z direction. The piezoelectric actuator 300 corresponds to a "piezoelectric body" that applies pressure to ink in the pressure chamber 12 to eject liquid from the nozzle 21. The piezoelectric actuator 300 includes the first electrode 60, the piezoelectric layer 70, and the second electrode 80. The active section 310 refers to the portion of the piezoelectric layer 70 where piezoelectric strain occurs when a voltage is applied between the first electrode 60 and the second electrode 80. In other words, the active section 310 refers to the portion of the piezoelectric layer 70 sandwiched between the first electrode 60 and the second electrode 80. In this embodiment, an active section 310 is formed for each pressure chamber 12. Generally, one of the electrodes of the active section 310 is an individual electrode independent of the other active section 310, and the other electrode is a common electrode shared by multiple active sections 310. In this embodiment, the first electrode 60 is separated for each active portion 310 to form an individual electrode for the active portion 310, and the second electrode 80 is provided continuously across the multiple active portions 310 to form a common electrode for the multiple active portions 310. Of course, the first electrode 60 may form a common electrode, and the second electrode 80 may form an individual electrode.

[0029] The piezoelectric layer 70 is made of a piezoelectric material made of a complex oxide with a perovskite structure represented by the general formula ABO3, for example.

[0030] Furthermore, individual lead electrodes 91, which are lead wiring, are drawn out from the first electrode 60. Furthermore, a common lead electrode (not shown), which is lead wiring, is drawn out from the second electrode 80. A flexible wiring substrate 110 is connected to the ends of these individual lead electrodes 91 and the common lead electrode opposite to the ends connected to the piezoelectric actuator 300. The wiring substrate 110 is mounted with a drive signal selection circuit 111 having a plurality of switching elements that select whether or not to supply a drive signal (COM) for driving each of the active portions 310 to each active portion 310. In other words, the wiring substrate 110 in this embodiment is a COF (Chip On Film). Note that the wiring substrate 110 does not necessarily have to be provided with the drive signal selection circuit 111. In other words, the wiring substrate 110 may be an FFC (Flexible Flat Cable), an FPC (Flexible Printed Circuits), or the like.

[0031] A protective substrate 30 having approximately the same size as the flow path forming substrate 10 is bonded to the surface of the flow path forming substrate 10 facing the -Z direction. The protective substrate 30 has a housing portion 31, which is a space for protecting the piezoelectric actuators 300. The housing portion 31 is provided independently for each row of the piezoelectric actuators 300 arranged side by side in the X axis direction, and two housing portions 31 are formed side by side in the Y axis direction. The protective substrate 30 also has a through hole 32 penetrating in the Z axis direction between the two housing portions 31 arranged side by side in the Y axis direction. Ends of individual lead electrodes 91 and a common lead electrode (not shown) drawn from the electrodes of the piezoelectric actuators 300 extend so as to be exposed in the through hole 32, and the individual lead electrodes 91 and the common lead electrode are electrically connected to the wiring substrate 110 within the through hole 32. As with the flow path forming substrate 10, for example, a silicon substrate, a glass substrate, an SOI substrate, or various ceramic substrates can be used as the protective substrate 30.

[0032] Additionally, a case member 40 is fixed to the protective substrate 30. The case member 40 defines a portion of a manifold 100 that communicates with the multiple pressure chambers 12. The case member 40 has substantially the same shape as the above-described communicating plate 15 in a plan view, and is bonded to the protective substrate 30 as well as the above-described communicating plate 15. The case member 40 has a recess 41 on the protective substrate 30 side that is deep enough to accommodate the flow path forming substrate 10 and the protective substrate 30. The case member 40 is also provided with a third manifold portion 42 that communicates with the first manifold portion 17 of the communicating plate 15. The first manifold portion 17 and second manifold portion 18 provided on the communicating plate 15 and the third manifold portion 42 provided on the case member 40 constitute the manifold 100 of this embodiment. A manifold 100 is provided for each nozzle row. That is, different types of ink can be ejected from each nozzle row. The case member 40 is also provided with inlet ports 44 that communicate with the manifolds 100 and supply ink to each manifold 100. The case member 40 is also provided with connection ports 43 that communicate with the through holes 32 of the protective substrate 30 and through which the wiring board 110 is inserted, and the wiring board 110 is led out to the surface of the liquid ejection head H that faces the -Z direction via the connection ports 43. The case member 40 can be made of, for example, a metal material, a resin material, or the like.

[0033] Furthermore, a compliance substrate 45 is provided on the surface of the communicating plate 15 on the +Z direction side where the first manifold portion 17 and the second manifold portion 18 open. This compliance substrate 45 seals the openings on the +Z direction side of the first manifold portion 17 and the second manifold portion 18. In this embodiment, such compliance substrate 45 includes a sealing film 46 made of a flexible thin film, and a fixed substrate 47 made of a hard material such as metal. An opening 48 that is completely removed in the thickness direction is provided in the region of the fixed substrate 47 facing the manifold 100, and one side of the manifold 100 forms a compliance portion 49 that is a flexible portion sealed only by the flexible sealing film 46.

[0034] In such a liquid ejection head H, liquid is taken in through the inlet 44, and the inside of the flow path from the manifold 100 to the nozzles 21 is filled with ink. Thereafter, in accordance with a signal from the drive signal selection circuit 111, a voltage is applied to each active portion 310 corresponding to the pressure chamber 12, thereby deflecting and deforming the vibration plate 50 together with the piezoelectric actuator 300. This increases the pressure of the liquid in the pressure chamber 12, causing droplets to be ejected from the designated nozzles 21.

[0035] Fig. 4 is a block diagram showing the electrical configuration of the liquid ejection device 1 of this embodiment. Fig. 5 is a block diagram showing the function realization section of the control unit 4. The electrical configuration and functions of the liquid ejection device 1 of this embodiment will be described with reference to Figs. 4 and 5.

[0036] As shown in FIG. 4, the liquid ejection device 1 includes a control unit 4, which is a control section of this embodiment, a print engine 220, and an operation panel 9.

[0037] The control unit 4 is an element that controls the entire liquid ejection device 1. The control unit 4 has a control processing unit 211 that includes a CPU and the like, a memory unit 212, a drive signal generation unit 213, an external I / F (interface) 214, an internal I / F 215, and a current detection unit 216. The memory unit 212 also includes a ROM that records control programs and the like, and a RAM that temporarily records various data required for printing images. The control processing unit 211 comprehensively controls each element of the liquid ejection device 1 and also realizes each function by executing the control program recorded in the memory unit 212. The drive signal generation unit 213 is an example of a "voltage application circuit."

[0038] Print data indicating an image to be printed on the medium S is sent from an external device 230 such as a host computer to the external I / F 214 of the control unit 4, and a print engine 220 is connected to the internal I / F 215. The print engine 220 is an element that records an image on the medium S under the control of the control unit 4, and includes a liquid ejection head H, a transport mechanism 5, and a movement mechanism 6.

[0039] The control unit 4 has functions as an injection control unit 240 , an acquisition unit 241 , a waveform adjustment unit 242 , a time acquisition unit 243 , a number acquisition unit 244 , and an aging processing unit 245 .

[0040] The ejection control unit 240 controls the ejection of droplets from the nozzles 21. Specifically, the control processing unit 211 converts print data sent from the external device 230 to the external I / F 214 into head control signals, such as a clock signal CLK, a latch signal LAT, a change signal CH, pixel data SI, and setting data SP, that instruct each activation unit 310 to eject or not eject droplets from each nozzle 21 of the liquid ejection head H, and transmits the signals to the liquid ejection head H via the internal I / F 215. Furthermore, the drive signal generation unit 213 generates a drive signal (COM) and transmits it to the liquid ejection head H via the internal I / F 215. That is, ejection data such as head control data and drive signals are transmitted to the liquid ejection head H via the internal I / F 215, which is a transmission unit.

[0041] The liquid ejection head H receives ejection data such as a head control signal and a drive signal from the control unit 4 , generates an application pulse from the head control signal and the drive signal, and applies the application pulse to the active portion 310 .

[0042] Furthermore, the control processing unit 211 generates movement control signals for the transport mechanism 5 and the movement mechanism 6 from print data received from the external device 230 via the external I / F 214, and transmits these to the transport mechanism 5 and the movement mechanism 6 via the internal I / F 215, thereby controlling the transport mechanism 5 and the movement mechanism 6. In this way, printing on the medium S is performed.

[0043] The current detection unit 216 is a circuit that applies a current detection signal to the piezoelectric actuator 300 to drive the piezoelectric actuator 300 and outputs a signal that is an integral of the current flowing through the piezoelectric actuator 300 while the current detection signal is being applied. Hereinafter, the integral of the current output by the current detection unit 216 is referred to as the "current integral value." The current integral value is referenced by the acquisition unit 241, which will be described later. The current detection signal is a signal that indicates the current detected when the voltage is gradually changed from a first voltage to a second voltage. The first and second voltages are set by the acquisition unit 241, which will be described later, and the current detection unit 216 drives the piezoelectric actuator 300 with a current detection signal that corresponds to the first and second voltages. Note that the piezoelectric actuator 300 has multiple active units 310, and the current detection signal may be applied to all or some of the active units 310. Here, the first voltage and the second voltage refer to the differential pressure actually applied to the piezoelectric layer 60, that is, the difference between the voltage applied to the first electrode 60 and the voltage applied to the second electrode.

[0044] 6 is a waveform diagram showing a drive signal according to this embodiment, and an example of a drive signal for ejecting ink droplets will be described with reference to FIG.

[0045] The drive signal (COM) generated by the drive signal generating unit 213 has a drive pulse that causes ink droplets to be ejected from the nozzle 21 within one recording period T (frequency 1 / T).

[0046] 6, the drive waveform DP is a relative value of the potential supplied to the first electrode 60, which is an individual electrode, when the second electrode 80, which is a common electrode of the multiple active units 310, is set to a reference potential Vbs. In other words, the voltage applied to the first electrode 60 by the drive waveform is the sum of the drive waveform DP shown by the solid line in FIG. 6 and the reference potential Vbs shown by the dashed line in FIG. 6.

[0047] The drive waveform DP comprises an enlargement element P1, an enlargement maintaining element P2, a contraction element P3, a contraction maintaining element P4, and an enlargement return element P5, in this order. The voltage of the enlargement element P1 is the potential difference between the potential indicated by the enlargement element P1 and a reference potential Vbs, and corresponds to the "enlargement voltage." The voltage of the contraction element P3 is the potential difference between the potential indicated by the contraction element P3 and the reference potential Vbs, and corresponds to the "contraction voltage." The voltage of the intermediate potential Vm is the potential difference between the intermediate potential Vm and the reference potential Vbs, and corresponds to the "intermediate voltage."

[0048] The expansion element P1 applies a first potential V1 from a state in which the intermediate potential Vm is applied, thereby expanding the volume of the pressure chamber 12 from the reference volume. The meniscus of ink formed in the nozzle 21 by the expansion element P1 is drawn into the pressure chamber 12, and ink is supplied to the pressure chamber 12 from the manifold 100 side.

[0049] The expansion maintaining element P2 maintains the volume of the pressure chamber 12 expanded by the expansion element P1 for a certain period of time.

[0050] The contraction element P3 applies a potential difference Vh from the first potential V1 to the second potential V2 to contract the volume of the pressure chamber 12. The volume of the pressure chamber 12 is suddenly contracted by the contraction element P3, and the ink in the pressure chamber 12 is pressurized and ejected from the nozzle 21 as an ink droplet.

[0051] The contraction maintaining element P4 maintains the volume of the pressure chamber 12 contracted by the contraction element P3 for a certain period of time.

[0052] The expansion return element P5 expands and returns the pressure chamber 12 from the contracted state at the second potential V2 to the reference volume at the intermediate potential Vm. The expansion return element P5 is supplied at a timing when the pressure of the ink in the pressure chamber 12, which was reduced by the contraction element P3, rises again due to the natural vibration of the meniscus at the contraction maintenance element P4. By supplying the expansion return element P5 at such a timing, the pressure fluctuation of the ink in the pressure chamber 12 is absorbed.

[0053] In such a driving waveform DP, the minimum voltage applied to the piezoelectric layer 60 is the first potential V1, and more specifically, its value is approximately -3.5 [V]. The maximum voltage applied to the piezoelectric layer is the second potential V2, and more specifically, its value is approximately 35 [V]. The reason for setting these values ​​will be explained later.

[0054] The acquisition unit 241 acquires the degree of deterioration of the piezoelectric actuator 300. The degree of deterioration of the piezoelectric actuator 300 is defined, for example, as follows.

[0055] The degree of deterioration of the piezoelectric actuator 300 is calculated as the ratio (second displacement amount - first displacement amount) / first displacement amount, where the displacement amount when the piezoelectric actuator 300 starts to be driven is defined as the first displacement amount, and the displacement amount after applying voltage for a certain driving time is defined as the second displacement amount. Hereinafter, this ratio will be referred to as the deterioration rate. Since the displacement amount decreases the more the piezoelectric actuator 300 is driven, the deterioration rate becomes smaller after voltage application than the displacement amount at the start of driving. Therefore, the drive change rate becomes a negative value. Note that the displacement amount corresponds to the amplitude of the diaphragm 50 deflected by deformation of the piezoelectric actuator 300. In other words, the displacement amount corresponds to the distance in the Z-axis direction between the part of the diaphragm 50 that is most deflected in the +Z direction and the part that is most deflected in the -Z direction.

[0056] Analysis by the inventors of the present invention has revealed that the deterioration rate is correlated with the rate of change of the following parameters. [Parameter Pm] This is a value indicating the maximum strain, and tends to decrease with degradation. It is due to the fixation of the polarization axis due to the movement of oxygen defects (fatigue degradation) and changes in the crystal structure (domain structure change). The parameter Pm can be calculated from the time integral of the current amount from the minimum voltage to the maximum voltage when the piezoelectric actuator 300 is driven. Since the contraction element P3 of the drive waveform DP shown in Figure 6 is an element that changes from the minimum potential V1, which is the minimum voltage, to the maximum potential V2, which is the maximum voltage, the parameter Pm can be easily obtained by applying the drive waveform DP, detecting the current flowing during the contraction element P3, and integrating it over time. [Parameter Pr] This is a value that indicates residual strain and tends to decrease with deterioration. It is due to the influence of the shift in coercive voltage caused by the movement of oxygen defects and changes in the crystal structure (domain structure changes). The parameter Pr can be calculated from the time integral of the current from the minimum voltage to 0 [V]. [Parameters Pm-Pr] This value is approximate to the dielectric constant and tends to decrease with deterioration. It is caused by a combination of the parameters Pm and Pr. The parameter Pm-Pr can be calculated by the time integral of the current from 0 [V] to the maximum voltage.

[0057] Unlike parameter Pm, parameters Pr and Pm-Pr have no elements in the drive waveform DP that change within the voltage range required for their detection. Therefore, although it is theoretically possible to measure them without error using the drive waveform DP (for example, by detecting the current from midway through contraction element P3), this is difficult in practice. Therefore, it is preferable to prepare a waveform for detection separate from the drive waveform DP. For example, it is preferable to prepare a waveform that changes from the minimum voltage to 0 [V] to detect parameter Pr, and a waveform that changes from 0 [V] to the maximum voltage to detect parameter Pm-Pr. Once either parameter Pr or parameter Pm-Pr is obtained, the other can be obtained by taking the difference between that parameter and parameter Pm.

[0058] In this way, information relating to the time integral value of the current flowing through the piezoelectric actuator 300 refers to parameters such as the above-mentioned parameters Pm, Pm-Pr, and Pr. As will be explained below with reference to Fig. 7, these parameters tend to decrease as the displacement of the piezoelectric actuator 300 deteriorates. In this embodiment, it is sufficient to acquire at least one of the parameters Pm, Pm-Pr, and Pr.

[0059] FIG. 7 illustrates the relationship between each parameter and the deterioration rate (dr). The horizontal axis represents the rate of change of each parameter, and the vertical axis represents the deterioration rate. As shown in the figure, experiments have shown that there is a positive correlation between the deterioration rate and the rate of change of each parameter. Therefore, it has been found that if the rate of change of a parameter can be obtained, the deterioration rate can also be obtained. The rate of change of a parameter is the ratio calculated as (post-driving parameter / initial parameter), where the value of the parameter when driving of the piezoelectric actuator 300 begins is the initial parameter and the parameter obtained after that time is the post-driving parameter. Details of the timing for obtaining the post-driving parameter will be described later.

[0060] A method for obtaining the parameter Pm will be described using Figures 8 and 9. Figure 8 is a butterfly curve for the piezoelectric actuator 300 of this embodiment. Figure 9 is a hysteresis loop showing the relationship between the voltage and current of the piezoelectric actuator 300 of this embodiment. The horizontal axis of Figure 8 is voltage [V], and the vertical axis is the displacement [nm] of the diaphragm 50. The horizontal axis of Figure 9 is voltage [V], and the vertical axis is current value [A].

[0061] As shown in FIG. 8, the piezoelectric actuator 300 of this embodiment has a minimum voltage (coercive field) of approximately −3.5 V and a maximum voltage of approximately 35 V. The minimum voltage is approximately equal to the coercive field of the piezoelectric actuator 300, and the maximum voltage is approximately equal to the voltage at which the piezoelectric actuator 300 reaches saturated polarization. When a current detection signal with this minimum voltage as the first voltage and the maximum voltage as the second voltage is applied to the piezoelectric actuator 300, the displacement ranges from zero to approximately 800 nm, resulting in maximum strain. Because the piezoelectric actuator 300 of this embodiment has these electrical characteristics, in order to maximize the displacement, the drive waveform DP shown in FIG. 6 sets the first potential V1, which is the minimum voltage, to approximately −3.5 V, and the second potential V2, which is the maximum voltage, to approximately 35 V. 9, when the current detection signal is applied to the piezoelectric actuator 300, a current flows through the piezoelectric actuator 300 as indicated by the path from point Q1 to point Q2 on the hysteresis loop (the path passing through point Q3). The current detection unit 216 integrates the current value within the range from point Q1 to point Q2 on the hysteresis loop. In other words, the integrated current value, which is the area between the horizontal axis and the path from point Q1 to point Q2, becomes the parameter Pm.

[0062] When a current detection signal with the first voltage as the minimum voltage and the second voltage as the maximum voltage is applied to the piezoelectric actuator 300, the displacement of the diaphragm 50 of the piezoelectric actuator 300 changes from zero to maximum strain. Therefore, the parameter Pm, which is the integral of the current flowing through the piezoelectric actuator 300 while the current detection signal is applied, indicates the maximum strain. While the parameter Pm does not represent the maximum strain itself, changes in the parameter Pm indicate changes in the maximum strain. For example, if the piezoelectric actuator 300 deteriorates and the maximum strain decreases, the parameter Pm also decreases accordingly. That is, as shown in FIG. 7, there is a positive correlation between the rate of change in the parameter Pm and the deterioration rate of the piezoelectric actuator 300. In this embodiment, the drive waveform DP shown in FIG. 6 is used, so the first voltage, which is the minimum voltage, corresponds to the minimum potential V1 in FIG. 6, and the second voltage, which is the maximum voltage, corresponds to the maximum potential V2 in FIG. 6.

[0063] Based on this principle, the acquisition unit 241 acquires the deterioration rate based on the parameter Pm as follows. First, the relationship between the deterioration rate and the parameter change rate as shown in FIG. 7 is obtained in advance through experiments or simulations. Then, the relationship between the deterioration rate and the parameter change rate is stored in the storage unit 212. For example, a correspondence table of the relationship between the deterioration rate and the parameter change rate is stored in the storage unit 212. Alternatively, a relational expression between the deterioration rate and the parameter change rate is stored in the storage unit 212. The relationship between the deterioration rate and the parameter change rate is specific depending on the structure of the liquid ejection head H, etc. Therefore, this relationship can be commonly used for liquid ejection devices 1 that employ liquid ejection heads H having the same structure.

[0064] The acquisition unit 241 sets a minimum voltage as the first voltage and a maximum voltage as the second voltage, and causes the current detection unit 216 to generate a current detection signal based on the first and second voltages and apply it to the piezoelectric actuator 300. The current detection unit 216 outputs an integral value of the current flowing through the piezoelectric actuator 300 based on the current detection signal. The acquisition unit 241 sets the current integral value output by the current detection unit 216 as a parameter Pm. The timing for acquiring this parameter Pm is when the piezoelectric actuator 300 starts to be driven and any time thereafter. If the parameter Pm acquired at the former timing is the initial parameter Pm and the parameter Pm acquired at the latter timing is the post-driving parameter Pm, the rate of change of the parameter Pm can be obtained by calculating (post-driving parameter Pm / initial parameter Pm). The initial parameter Pm is stored in the storage unit 212 or the like during manufacturing or shipping of the liquid ejection head H. The post-driving parameter Pm can be acquired at any timing, but is preferably acquired at the timing when waveform adjustment is performed based on, for example, the deterioration rate.

[0065] Next, each time the acquisition unit 241 acquires the post-drive parameter Pm, it reads out the initial parameter Pm to find the rate of change of the parameter Pm, and acquires the deterioration rate from the correspondence table or relational expression stored in the storage unit 212. For example, when using the correspondence table, the deterioration rate corresponding to the rate of change of the parameter Pm is read from the correspondence table. When using the relational expression, the deterioration rate is obtained by substituting the rate of change of the parameter Pm into the relational expression. In this way, the acquisition unit 241 acquires the post-drive parameter Pm at any timing after shipment, for example, when waveform adjustment is performed, and acquires the deterioration rate corresponding to the post-drive parameter Pm.

[0066] A method for obtaining the parameters Pm-Pr will be described. As shown in Fig. 8, the first voltage is set to zero [V] and the second voltage to the maximum voltage, and current detection unit 216 generates a current detection signal based on the first and second voltages and applies it to piezoelectric actuator 300. As shown in Fig. 9, when this current detection signal is applied to piezoelectric actuator 300, a current flows through piezoelectric actuator 300 as indicated by the path from point Q3 to point Q2 on the hysteresis loop. Current detection unit 216 integrates the current value within the range from point Q3 to point Q2 on the hysteresis loop. In other words, the current integral, which is the area between the horizontal axis and the path from point Q3 to point Q2, becomes parameter Pm-Pr.

[0067] The parameter Pm-Pr is a value that approximates the dielectric constant and tends to decrease with deterioration. If the piezoelectric actuator 300 deteriorates and the displacement decreases, the parameter Pm-Pr also decreases accordingly. In other words, as shown in FIG. 7, there is a positive correlation between the rate of change in the parameter Pm-Pr and the deterioration rate of the piezoelectric actuator 300.

[0068] The acquisition unit 241 sets the first voltage to zero and the second voltage to the maximum voltage, and causes the current detection unit 216 to generate a current detection signal based on the first and second voltages and apply it to the piezoelectric actuator 300. The current detection unit 216 outputs the integral value of the current flowing through the piezoelectric actuator 300 based on the current detection signal. The acquisition unit 241 sets the current integral value output by the current detection unit 216 as the parameter Pm-Pr. The timing for acquiring this parameter Pm-Pr is when the piezoelectric actuator 300 starts to be driven and any time thereafter. If the parameter Pm-Pr acquired at the former timing is the initial parameter Pm-Pr and the parameter Pm-Pr acquired at the latter timing is the post-drive parameter Pm-Pr, the rate of change of the parameter Pm-Pr can be obtained by calculating (post-drive parameter Pm-Pr / initial parameter Pm-Pr). The initial parameter Pm-Pr is stored in the storage unit 212 or the like during manufacturing or shipping of the liquid ejection head H. The timing for obtaining the post-drive parameter Pm-Pr is arbitrary, but it is preferable that the timing is the timing for adjusting the waveform based on the deterioration rate, for example.

[0069] Next, each time the acquisition unit 241 acquires the post-drive parameter Pm-Pr, it reads out the initial parameter Pm-Pr, calculates the rate of change of the parameter Pm-Pr, and acquires the deterioration rate from the correspondence table and relational equation stored in the memory unit 212.

[0070] The method for obtaining the parameter Pr will be described. As shown in FIG. 8, the first voltage is set to a minimum voltage, and the second voltage is set to zero [V]. The current detection unit 216 generates a current detection signal based on the first and second voltages and applies it to the piezoelectric actuator 300. As shown in FIG. 9, when the current detection signal is applied to the piezoelectric actuator 300, a current flows through the piezoelectric actuator 300 as indicated by the path from point Q1 to point Q3 on the hysteresis loop. The current detection unit 216 integrates the current value within the range from point Q1 to point Q3 on the hysteresis loop. That is, the current integral, which is the area between the horizontal axis and the path from point Q1 to point Q3, becomes the parameter Pr. Note that, in addition to calculating the integral of the current value, parameter Pr may also be obtained by calculating the above-mentioned parameter Pm and parameter Pm-Pr and subtracting parameter Pm-Pr from parameter Pm.

[0071] The parameter Pr is a value that indicates the residual strain and tends to decrease with deterioration. If the piezoelectric actuator 300 deteriorates and the displacement decreases, the parameter Pr also decreases accordingly. In other words, as shown in FIG. 7, there is a positive correlation between the rate of change in the parameter Pr and the deterioration rate of the piezoelectric actuator 300.

[0072] The acquisition unit 241 sets the first voltage to a minimum voltage and the second voltage to zero [V], and causes the current detection unit 216 to generate a current detection signal based on the first and second voltages and apply it to the piezoelectric actuator 300. The current detection unit 216 outputs an integral value of the current flowing through the piezoelectric actuator 300 based on the current detection signal. The acquisition unit 241 sets the current integral value output by the current detection unit 216 as a parameter Pr. The timing for acquiring this parameter Pr is when the piezoelectric actuator 300 starts to be driven and any time thereafter. If the parameter Pr acquired at the former timing is defined as an initial parameter Pr and the parameter Pr acquired at the latter timing is defined as a post-driving parameter Pr, the rate of change of the parameter Pr can be obtained by calculating (post-driving parameter Pr / initial parameter Pr). The initial parameter Pr is stored in the storage unit 212 during manufacturing or shipping of the liquid ejection head H. The post-driving parameter Pr can be acquired at any timing, but is preferably acquired at a timing when waveform adjustment is performed based on, for example, the deterioration rate.

[0073] Next, the acquisition unit 241 acquires the deterioration rate from the rate of change of the parameter Pr and the correspondence table or relational expression stored in the storage unit 212. For example, when using the correspondence table, the deterioration rate corresponding to the rate of change of the parameter Pr is read from the correspondence table. When using the relational expression, the deterioration rate is obtained by substituting the rate of change of the parameter Pr into the relational expression.

[0074] The waveform adjustment unit 242 adjusts the drive waveform in accordance with the deterioration rate of the piezoelectric actuator 300 acquired by the aforementioned acquisition unit 241. Specifically, the waveform adjustment unit 242 calculates the corrected potential difference Vh (hereinafter, corrected Vh) by applying the deterioration rate dr and the potential difference Vh (hereinafter, also referred to as reference Vh) in the drive waveform DP to Equation 1. After correction Vh=A(1 / (1+dr))-1) 2 +B((1 / (1+dr))-1)+C (Equation 1) A=As×Vh+Ai B=Bs×Vh+Bi C=Cs×Vh+Ci The coefficients As, Bs, Cs, Ai, Bi, and Ci are values ​​determined based on the linearity of the piezoelectric actuator 300, as will be described in detail below. In this way, Equation 1 and the coefficients A to C used in Equation 1 are stored in a memory (not shown) provided in the liquid ejection head H, the storage unit 212 of the control unit 4, the memory of the external device 230, the cloud, or the like. The waveform adjustment unit 242 calculates the corrected Vh by applying the coefficients A to C read from the memory, the reference Vh used in the drive waveform DP, and the deterioration rate dr acquired by the acquisition unit 241 to Equation 1. Then, the waveform adjustment unit 242 changes the reference Vh of the drive waveform DP to the corrected Vh.

[0075] The waveform adjuster 242 may obtain the corrected Vh based on the correction amount instead of the deterioration rate. The correction amount dc is obtained from Equation 2. dc=(1 / (1+dr))-1 (Equation 2) For example, if the deterioration rate is -0.05, the correction amount is approximately 0.053. In other words, if the displacement amount has deteriorated by 5%, in order to return it to the original displacement amount, the drive waveform DP must be corrected so that the displacement amount is increased by approximately 5.3%. The corrected Vh can be obtained by substituting the correction amount dc into Equation 3, which is obtained by substituting Equation 2 into Equation 1. After correction Vh=Adc 2 +Bdc+C (Formula 3)

[0076] The adjustment of the drive waveform using the above-mentioned formula 1 will now be described. As shown in formula 4, it is empirically known that the displacement of the piezoelectric actuator 300 can be linearly approximated with respect to the logarithm of the voltage. This characteristic of the displacement of the piezoelectric actuator 300 depending on the voltage is called linearity. The voltage in linearity is the potential difference Vh in the drive waveform DP shown in FIG. 6.

[0077] y=a×Ln(x)+b (Formula 4) y is the displacement and x is the reference Vh.

[0078] Figure 10 shows the linearity before and after durability testing. In the figure, graph G1 has voltage [V] on the horizontal axis and displacement [nm] on the vertical axis. Graph G2 has voltage [V] on the horizontal axis and rate of change [%] on the vertical axis. Voltage is the potential difference Vh of the drive waveform DP. "1" in graphs G1 and G2 indicates the linearity for a piezoelectric actuator 300 to which a drive waveform of 100 million shots was applied. Similarly, "130" indicates the linearity for a piezoelectric actuator 300 to which a drive waveform of 13 billion shots was applied, and "2500" indicates the linearity for a piezoelectric actuator 300 to which a drive waveform of 250 billion shots was applied.

[0079] As shown in the "Displacement Amount" column of graph G1 and table T1, the displacement amount varies depending on the voltage. The degree of change varies depending on the durability, i.e., the number of shots of the drive waveform DP. In this example, the displacement amount after 13 billion shots is smaller than after 100 million shots, and the displacement amount after 250 billion shots is smaller than after 13 billion shots.

[0080] Graph G2 shows the displacement of graph G1 converted into a rate of change. Here, the displacement when the voltage is 25V is used as the reference, and the ratio of the displacement at each voltage to that reference displacement is used as the rate of change. The reference Vh mentioned above is the potential difference Vh set as the reference in this way. As shown in graph G2 and the "25V reference rate of change" in table T1, the rate of change varies depending on the voltage, but it can be seen that the rate of change is approximately the same even if the durability differs. For example, the rate of change corresponding to a voltage of 19V is 84% ​​for all shot counts.

[0081] Thus, when a specific voltage is used as the reference, the rate of change in linearity is roughly the same regardless of the degree of durability, so Vh in Table T1 can be considered the corrected Vh, and the rate of change in each voltage can be considered the correction amount dc. For example, suppose that piezoelectric actuator 300 using a drive waveform with a potential difference Vh of 25 V deteriorates and the correction amount is 10%. In this case, the original displacement can be restored by setting the corrected Vh to 30 V, which corresponds to 110%.

[0082] The relationship between the correction amount dc and the corrected Vh can be well approximated by a quadratic function shown in Equation 3. The coefficients A, B, and C in Equation 3 can be approximated by a linear equation with the reference Vh as a variable and As, Ai, Bs, Bi, Cs, and Ci as coefficients, as shown in Equation 1. It is known that As, Ai, Bs, Bi, Cs, and Ci are values ​​determined by the linearity of the piezoelectric actuator 300.

[0083] As, Ai, Bs, Bi, Cs, and Ci are specific values ​​determined by the configuration of the liquid ejection head H, the shape and material of the piezoelectric actuator 300, etc., so these coefficients are experimentally determined in advance and stored in the memory unit 212 when the liquid ejection head H is manufactured or shipped.

[0084] As described above, the waveform adjustment unit 242 calculates the corrected Vh using the deterioration rate acquired by the acquisition unit 241, the reference Vh applied to the drive waveform, Equation 1, and coefficients A to C obtained based on the linearity, and corrects the drive waveform to achieve the corrected Vh. By adjusting the drive waveform in accordance with the deterioration rate dr in this way, the displacement amount of the piezoelectric actuator 300 increases by the amount of correction, and can be restored to the original displacement amount.

[0085] The time acquisition unit 243 acquires information regarding the time the liquid ejection head H has been used. Hereinafter, this information will be referred to as usage time information. The time the liquid ejection head H has been used may be, for example, the accumulated time that power is supplied to the liquid ejection head H. Another example is the accumulated time that the liquid ejection head H has been ejecting liquid. The time acquisition unit 243 stores such usage time information in the storage unit 212. The usage time information acquired by the time acquisition unit 243 can be referenced by the waveform adjustment unit 242.

[0086] The count acquisition unit 244 acquires information relating to the number of times liquid has been ejected from the liquid ejection head H. Hereinafter, this information will be referred to as ejection count information. The ejection count information can be acquired, for example, by accumulating the number of drive waveforms DP applied to the piezoelectric actuator 300. Alternatively, the ejection count information may be acquired by capturing an image of the droplets ejected from the nozzle 21, detecting the droplets from the image obtained by capturing the image using a known image processing method, and accumulating the number of detected droplets.

[0087] The liquid ejection head H is provided with a plurality of nozzles 21. Therefore, ejection count information may be acquired for liquid ejected from a specific nozzle 21. Alternatively, the average value, maximum value, minimum value, or total value of the number of times liquid is ejected from the plurality of nozzles 21 may be used as the ejection count information. The number acquisition unit 244 stores such ejection count information in the storage unit 212. The ejection count information acquired by the number acquisition unit 244 can be referenced by the waveform adjustment unit 242.

[0088] It is preferable that the waveform adjustment unit 242 adjusts the drive waveform when the usage time information acquired by the time acquisition unit 243 exceeds a predetermined threshold number of times. It is also preferable that the waveform adjustment unit 242 adjusts the drive waveform when the ejection count information acquired by the count acquisition unit 244 exceeds a predetermined threshold number of times. It is also preferable that the waveform adjustment unit 242 adjusts the drive waveform when it receives input indicating that the drive waveform needs to be adjusted from the operation device 9b, which receives input from the user regarding whether or not the drive waveform needs to be adjusted. Of course, the waveform adjustment unit 242 can adjust the drive waveform at any timing.

[0089] The aging processing unit 245 reduces the displacement of the piezoelectric actuator 300 by driving the piezoelectric actuator 300 before printing according to the degree of deterioration of the piezoelectric actuator 300. In this embodiment, the aging processing unit 245 performs the aging process by driving the piezoelectric actuator 300 with the same drive signal (COM) as the drive signal used to eject ink droplets. The time required for this aging process is referred to as the voltage application time. The displacement can be reduced to the desired amount by appropriately adjusting the voltage application time. Note that the aging processing unit 245 may also drive the piezoelectric actuator 300 using a drive signal having a drive waveform dedicated to aging that is different from the drive signal (COM) used to eject ink droplets.

[0090] The aging process uses correspondence relationship information that indicates the correspondence relationship between the driving time and the deterioration rate of the piezoelectric actuator 300. An example of the correspondence relationship information is shown in Figure 11. The horizontal axis represents the voltage application time, and the vertical axis represents the deterioration rate.

[0091] The figure shows the relationship between the voltage application time and the degradation rate when the piezoelectric actuator 300 is continuously driven after the aging process, when the driving time for which the piezoelectric actuator 300 is driven is changed in increments of 0.5 hours from 0 hours (0 hrs) to 2.5 hours (2.5 hrs).

[0092] Regardless of the drive time during aging, the longer the voltage application time, the smaller the deterioration rate of the piezoelectric actuator 300. However, the change in the deterioration rate becomes gradual after the voltage application time has reached a certain level. Thus, although the degree of deterioration rate differs depending on the drive time in the initial stage of drive, the tendency for the deterioration rate to decrease with increasing voltage application time is common.

[0093] For example, for a piezoelectric actuator 300 whose initial drive time is 0.5 hours, the deterioration rate acquired by the acquisition unit 241 is -4%, and the displacement of the piezoelectric actuator 300 is to be reduced to -6% will be described. In this case, the aging processing unit 245 uses the correspondence information for a drive time of 0.5 hours, as indicated by the solid line. The aging processing unit 245 then obtains 1020 hours, which is the difference between the voltage application time of approximately 180 hours corresponding to -4% indicated at point R1 and the voltage application time of approximately 1300 hours corresponding to -6% indicated at point R2. The aging processing unit 245 applies the drive waveform to the piezoelectric actuator 300 for 1020 hours. This reduces the displacement of the piezoelectric actuator 300 from a deterioration rate of -4% to -6%.

[0094] It is preferable that the correspondence information be stored in an external memory provided outside the liquid ejection device 1, and that the aging processing unit 245 acquire the correspondence information from the external memory. Examples of external memories include a storage medium physically connected to the liquid ejection device 1, and a server connected to the liquid ejection device 1 via a network such as the Internet or a public telephone network. Of course, the correspondence information is not limited to information stored in an external memory; for example, the correspondence information may be stored in the storage unit 212 of the liquid ejection device 1, and the aging processing unit 245 may acquire the correspondence information from the storage unit 212.

[0095] A method for acquiring the deterioration state (deterioration rate) using the acquisition unit 241 described above and subsequent adjustment of the drive waveform will be described with reference to Figs. 12 and 13. Fig. 12 is a flowchart illustrating a method for acquiring the deterioration rate of the liquid ejection device 1. Fig. 13 is an example of a screen displayed on the display device 9a. Here, the parameter Pm will be described, but the same applies when using the parameter Pm-Pr or the parameter Pr.

[0096] First, the initial parameter Pm is acquired (step S1) when the liquid ejection head H is manufactured or shipped. Specifically, as described above, the acquisition unit 241 supplies a current detection signal to the piezoelectric actuator 300 and acquires the integral value of the current flowing through the piezoelectric actuator 300. The acquisition unit 241 then stores the integral value as the initial parameter Pm in the storage unit 212 or the like.

[0097] Next, it is determined whether the usage time information exceeds a threshold time (step S2). Specifically, the waveform adjustment unit 242 determines whether the usage time information acquired by the time acquisition unit 243 exceeds a threshold time by comparing the information with the threshold time previously stored in the storage unit 212.

[0098] If the usage time information is equal to or shorter than the threshold time (step S2: No), it is determined whether the ejection count information exceeds the threshold count (step S3). Specifically, the waveform adjustment unit 242 makes this determination by referring to the ejection count information acquired by the count acquisition unit 244 and comparing it with the threshold count previously stored in the storage unit 212.

[0099] If the ejection count information is equal to or less than the threshold count (step S3: No), it is determined whether the user has input that the drive waveform needs to be adjusted (step S4). For example, in response to a user operation, a screen such as that shown in FIG. 13 is displayed on the display device 9a (see FIG. 1), and the user operates the operation device 9b (see FIG. 1) to input that the drive waveform needs to be adjusted. If no such input is received (step S4: No), the process returns to step S2 after a predetermined time has elapsed. Note that in practice, step S4 is not necessarily performed in the order of steps S2 and S3, but is an event that occurs due to a user operation.

[0100] If the usage time information exceeds the threshold time (step S2: Yes), if the ejection count information exceeds the threshold count (step S3: Yes), or if the user inputs that the drive waveform needs to be adjusted (step S4: Yes), the post-drive parameter Pm is acquired (step S5). Specifically, as described above, the acquisition unit 241 acquires the post-drive parameter Pm.

[0101] Next, the amount of change in the parameter Pm is calculated from the initial parameter Pm and the post-drive parameter Pm (step S6). Then, the deterioration rate dr is obtained from the amount of change in the parameter Pm (step S7). Specifically, the acquisition unit 241 acquires the post-drive parameter Pm, and acquires the deterioration rate dr based on the relationship between the amount of change in the parameter Pm and the deterioration rate dr.

[0102] Next, the drive waveform is adjusted based on the deterioration rate dr acquired by the acquisition unit 241 (step S8). Specifically, as described above, the waveform adjustment unit 242 calculates the corrected Vh based on the deterioration rate dr, the potential difference Vh (reference Vh) of the drive waveform currently being used, and Equation 1, and corrects the drive waveform to achieve the corrected Vh.

[0103] As described above, the liquid ejection device 1 according to this embodiment comprises a liquid ejection head H having a nozzle 21 for ejecting liquid, a pressure chamber 12, and a piezoelectric actuator 300 for applying pressure to the liquid in the pressure chamber 12 in order to eject the liquid from the nozzle 21, a drive signal generation unit 213 which is a voltage application circuit that applies voltage to the piezoelectric actuator 300, and an acquisition unit 241 that acquires the deterioration rate, which is the degree of deterioration of the piezoelectric actuator 300, based on information relating to the integral value of the current generated when the voltage applied to the piezoelectric actuator 300 is gradually changed from a first voltage to a second voltage.

[0104] When a current detection signal that gradually changes from a first voltage to a second voltage is applied to the piezoelectric actuator 300, the displacement of the diaphragm 50 of the piezoelectric actuator 300 changes. Information regarding the integral of the current flowing through the piezoelectric actuator 300 while the current detection signal is applied tends to decrease as the displacement of the piezoelectric actuator 300 deteriorates. In other words, the information regarding the integral of the current can be considered equivalent to a direct measurement of the decrease in the displacement of the piezoelectric actuator 300. Therefore, the ratio of the information regarding the integral of the current obtained before and after durability directly indicates the degree of deterioration from the original displacement of the piezoelectric actuator 300, and the deterioration rate of the piezoelectric actuator 300 can be more accurately obtained using the correlation illustrated in FIG. 7. Furthermore, when the liquid ejection head H is mounted on the liquid ejection device 1, it is difficult to directly measure the deterioration rate of the liquid ejection head H because a special measuring device is required. However, with the liquid ejection device 1 of the present invention, the current detection unit 216 can obtain the integral value of the current flowing through the piezoelectric actuator 300, and the deterioration rate can be obtained based on this integral value. In other words, the deterioration rate can be obtained with the liquid ejection head H still mounted on the liquid ejection device 1, without the need for a special measuring device.

[0105] In the liquid ejection device 1 according to this embodiment, the first and second voltages are one positive and the other negative. The first voltage is approximately equal to the coercive field of the piezoelectric actuator 300, and the second voltage is approximately equal to the voltage at which the piezoelectric actuator 300 reaches saturated polarization. As described above, the current detection signal used to obtain the parameter Pm has a negative first voltage that is approximately equal to the coercive field. The second voltage is also approximately equal to the voltage at which saturated polarization occurs. Note that "the first voltage is approximately equal to the coercive field" means that the ratio of the first voltage to the coercive field (first voltage / coercive field) is 90% or more and 110% or less. "The second voltage is approximately equal to the voltage at which saturated polarization occurs" means that the ratio of the second voltage to the voltage at which saturated polarization occurs (second voltage / voltage at which saturated polarization occurs) is 90% or more and 110% or less. With this liquid ejection device 1, the parameter Pm, which is the integral of the current, is equivalent to the direct result of the maximum strain, and deterioration of the parameter Pm represents deterioration of the maximum strain, making it possible to obtain a deterioration rate based on the maximum strain of the piezoelectric actuator 300. The first voltage may be positive and the second voltage may be negative. For example, if the second electrode 80 of the piezoelectric actuator 300 is used as a common electrode and a reference potential Vbs is applied, the first voltage will be positive and the second voltage will be negative. In this case, too, a current detection signal that gradually changes from the first voltage to the second voltage can be applied to the piezoelectric actuator 300 in a similar manner, and the deterioration rate can be obtained based on the integral of the current flowing through the piezoelectric actuator 300.

[0106] In the liquid ejection device 1 according to this embodiment, the drive signal generation unit 213, which is a voltage application circuit, applies a drive waveform to the piezoelectric actuator 300 to eject liquid from the nozzle 21, with the first voltage being the minimum voltage of the drive waveform and the second voltage being the maximum voltage of the drive waveform. In this embodiment, the minimum voltage of the drive waveform is the potential difference between the first potential V1 and the reference potential Vbs, and the maximum voltage is the potential difference between the second potential V2 and the reference potential Vbs. The minimum voltage of the drive waveform is approximately equal to the coercive field, and the maximum voltage is approximately equal to the voltage at which saturated polarization occurs. Therefore, as described above, the deterioration rate based on the maximum strain of the piezoelectric actuator 300 can be obtained based on the parameter Pm.

[0107] In the liquid ejection device 1 according to this embodiment, the first voltage is a voltage substantially equal to 0, and the second voltage is a voltage substantially equal to the voltage at which the piezoelectric body reaches saturated polarization. As described above, the current detection signal used to obtain the parameter Pm-Pr has a first voltage of zero, and a second voltage substantially equal to the voltage at which saturated polarization occurs. With this liquid ejection device 1, the parameter Pm-Pr, which is the integral of the current, is equivalent to the directly obtained dielectric constant, and degradation of the parameter Pm-Pr represents degradation of the dielectric constant, so that a degradation rate based on the dielectric constant of the piezoelectric actuator 300 can be obtained.

[0108] In the liquid ejection device 1 according to this embodiment, the first voltage is a voltage substantially equal to the coercive electric field of the piezoelectric actuator 300, and the second voltage is zero. As described above, the current detection signal used to obtain the parameter Pr has a first voltage substantially equal to the coercive electric field, and a second voltage of zero. With this liquid ejection device 1, the parameter Pr, which is the integral of the current, is equivalent to a direct result of the residual strain, and deterioration of the parameter Pr represents deterioration of the residual strain, so that a deterioration rate based on the residual strain of the piezoelectric actuator 300 can be obtained.

[0109] In the liquid ejection device 1 according to this embodiment, the drive signal generation unit 213, which is a voltage application circuit, applies a drive waveform to the piezoelectric actuator 300 in order to eject liquid from the nozzle 21, and further includes a waveform adjustment unit 242 that adjusts the drive waveform in accordance with the degree of deterioration of the piezoelectric actuator 300. Because the deterioration rate of the piezoelectric actuator 300 acquired by the acquisition unit 241 is accurate, using a drive waveform adjusted based on this deterioration rate makes it possible to more accurately adjust the displacement amount of the piezoelectric actuator 300 to the displacement amount before deterioration.

[0110] In the liquid ejection device 1 according to this embodiment, the drive waveform is a waveform in which an intermediate voltage, an expansion voltage that expands the pressure chamber 12, a contraction voltage that contracts the pressure chamber 12, and an intermediate voltage are applied in this order.

[0111] In the liquid ejection device 1 according to this embodiment, the waveform adjustment unit 242 adjusts the drive waveform so that the reference Vh, which is the difference between the expansion voltage and the contraction voltage, increases as the degree of deterioration of the piezoelectric actuator 300 increases. As illustrated in the 100 million shots column of Table T1 in FIG. 10, when attempting to recover 10% from 100% (denoted as 110% in Table T1), the reference Vh of 25 [V] is corrected to the corrected Vh of 30 [V]. On the other hand, when attempting to recover 19% from 100%, the reference Vh of 25 [V] is corrected to the corrected Vh of 35 [V]. In this way, the greater the degree of deterioration of the piezoelectric actuator 300, in other words, the greater the correction amount, the larger the reference Vh, allowing for recovery closer to the original displacement.

[0112] The liquid ejection device 1 according to this embodiment further includes a time acquisition unit 243 that acquires usage time information, which is information relating to the time for which the liquid ejection head H has been used, and the waveform adjustment unit 242 adjusts the drive waveform when the usage time information acquired by the time acquisition unit 243 exceeds a predetermined threshold time. With this liquid ejection device 1, it is possible to automatically adjust the drive waveform at a timing when it is estimated that the displacement amount of the piezoelectric actuator 300 has deteriorated considerably.

[0113] The liquid ejection device 1 according to this embodiment further includes a count acquisition unit 244 that acquires ejection count information, which is information relating to the number of times liquid has been ejected from the liquid ejection head H, and the waveform adjustment unit 242 adjusts the drive waveform when the ejection count information acquired by the count acquisition unit 244 exceeds a predetermined threshold number. With this type of liquid ejection device 1, it is possible to automatically adjust the drive waveform at a timing when it is estimated that the displacement amount of the piezoelectric actuator 300 has deteriorated to a considerable extent.

[0114] The liquid ejection device 1 according to this embodiment further includes an operation device 9b that receives input from the user as to whether or not the drive waveform needs to be adjusted, and the waveform adjustment unit 242 adjusts the drive waveform when the operation device 9b receives input indicating that the drive waveform needs to be adjusted. With this liquid ejection device 1, the drive waveform can be automatically adjusted at a timing desired by the user.

[0115] The liquid ejection device 1 according to this embodiment further includes an aging processing unit 245 that performs an aging process to reduce the displacement of the piezoelectric actuator 300 by driving the piezoelectric actuator 300 before printing, depending on the degree of deterioration of the piezoelectric actuator. The aging process can be performed according to the user's needs while the liquid ejection head H is mounted on the liquid ejection device 1. This prevents the liquid ejection head H from no longer meeting the user's needs, thereby improving user satisfaction.

[0116] The liquid ejection device 1 according to this embodiment includes a liquid ejection head H including a nozzle 21 for ejecting liquid, a pressure chamber 12, and a piezoelectric actuator 300 for applying pressure to the liquid in the pressure chamber 12 to eject the liquid from the nozzle 21; a drive signal generation unit 213 which is a voltage application circuit that applies voltage to the piezoelectric actuator 300; and an acquisition unit that acquires the degree of deterioration of the piezoelectric actuator 300 based on information about the maximum strain or residual strain of the piezoelectric actuator 300. In the above-described embodiment, the parameters Pm and Pr obtained from the integral of the current flowing through the piezoelectric actuator 300 represent the maximum strain and residual strain, respectively. However, the integral of the current does not necessarily have to be used. In other words, the degree of deterioration of the piezoelectric actuator 300 may be directly acquired by measuring the maximum strain or residual strain of the piezoelectric actuator 300 and comparing the values ​​of the maximum strain or residual strain before and after endurance testing.

[0117] The method for acquiring the deterioration state of the liquid ejection device 1 according to this embodiment involves applying a current detection signal, which is a voltage that is gradually changed from a first voltage to a second voltage, to the piezoelectric actuator 300, integrating the current generated by the application of the current detection signal to acquire parameters Pm, Pm-Pr, and Pr, which are information related to the integral value, and acquiring the degree of deterioration of the piezoelectric actuator 300 based on this information. The information related to the integral value of the current acquired by this acquisition method can be considered equivalent to a direct measurement of the decrease in the displacement of the piezoelectric actuator 300. Therefore, the ratio of the information related to the integral value of the current obtained before and after durability testing directly indicates the degree of deterioration from the original displacement of the piezoelectric actuator 300, and the deterioration rate of the piezoelectric actuator 300 can be more accurately acquired using the correlation illustrated in FIG. 7.

[0118] (Other embodiments) Although the embodiments of the present invention have been described above, the basic configuration of the present invention is not limited to those described above.

[0119] For example, in the above-described first embodiment, three types of parameters Pm, Pm-Pr, and Pr are exemplified, but the acquisition unit 241 may employ any one of them, or may employ multiple parameters. When multiple parameters are used, a deterioration rate corresponding to each parameter is obtained. The acquisition unit 241 may select any one of the multiple deterioration rates, or may employ, for example, the average value, maximum value, or minimum value of the multiple deterioration rates as the deterioration rate.

[0120] In the above-described first embodiment, the change in current when the voltage is changed from a low to a high voltage is detected to obtain the parameters Pm, Pm-Pr, and Pr, but it is also possible to detect the change in current when the voltage is changed from a high to a low voltage. In that case, the lower path in the hysteresis loop of Fig. 9 is followed instead of the upper path. However, if a piezoelectric material is used whose characteristics are almost the same when the voltage is changed from a high to a low voltage and when the voltage is changed from a low to a high voltage (the hysteresis loop is almost point-symmetric), it is possible to obtain approximately the same results even if the lower path is used.

[0121] In the above-described first embodiment, a thin-film piezoelectric actuator 300 is used as the driving element for generating a pressure change in the pressure chamber 12, but this is not particularly limited to this. For example, a thick-film piezoelectric actuator formed by a method such as adhering a green sheet, or a longitudinal vibration piezoelectric actuator in which piezoelectric material and electrode forming material are alternately laminated to expand and contract in the axial direction can be used.

[0122] Furthermore, the present invention is broadly applicable to liquid ejection devices in general that include a liquid ejection head. Examples of liquid ejection heads include various inkjet recording heads used in image recording devices such as printers, and colorant ejection heads used in manufacturing color filters for liquid crystal displays and the like. Examples of liquid ejection heads include electrode material ejection heads used in forming electrodes for organic EL displays, FEDs (field emission displays), and the like, and bioorganic material ejection heads used in biochip manufacturing, and the present invention can also be applied to liquid ejection devices that include these liquid ejection heads.

[0123] (Addendum) From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0124] A liquid ejection device according to a preferred embodiment, aspect 1, comprises a liquid ejection head having a nozzle for ejecting liquid, a pressure chamber, and a piezoelectric element for applying pressure to the liquid in the pressure chamber to eject the liquid from the nozzle, a voltage application circuit for applying a voltage to the piezoelectric element, and an acquisition unit for acquiring the degree of deterioration of the piezoelectric element based on information regarding the integral value of the current generated when the voltage applied to the piezoelectric element is gradually changed from a first voltage to a second voltage.

[0125] According to this, the information on the integral of the current tends to decrease as the displacement of the piezoelectric body deteriorates, and therefore, based on the information on the integral of the current obtained, it is possible to directly determine the degree of deterioration of the piezoelectric body from its original displacement, and to more accurately determine the degree of deterioration of the piezoelectric body.

[0126] In aspect 2, which is a specific example of aspect 1, one of the first voltage and the second voltage is positive and the other is negative, the first voltage is a voltage approximately equal to the coercive electric field of the piezoelectric body, and the second voltage is a voltage approximately equal to the voltage at which the piezoelectric body reaches saturated polarization. Information regarding the integral value of the current represents the maximum strain of the piezoelectric body, so it is possible to obtain the degree of deterioration based on the maximum strain of the piezoelectric body.

[0127] In Aspect 3, which is a specific example of Aspect 1 or Aspect 2, the voltage application circuit applies a drive waveform to the piezoelectric body to eject liquid from the nozzle, the first voltage being a minimum voltage of the drive waveform, and the second voltage being a maximum voltage of the drive waveform. Information regarding the integrated value of the current represents the maximum strain of the piezoelectric body, and therefore it is possible to obtain the degree of deterioration based on the maximum strain of the piezoelectric body.

[0128] In Aspect 4, which is a specific example of Aspect 1, the first voltage is a voltage substantially equal to 0, and the second voltage is a voltage substantially equal to a voltage at which the piezoelectric body reaches saturated polarization. Information relating to the integral value of the current represents the dielectric constant of the piezoelectric body, and therefore the degree of deterioration based on the dielectric constant of the piezoelectric body can be obtained.

[0129] In aspect 5, which is a specific example of aspect 1, the first voltage is a voltage substantially equal to the coercive electric field of the piezoelectric body, and the second voltage is 0. Information relating to the integral value of the current represents residual strain in the piezoelectric body, and therefore the degree of deterioration based on the residual strain in the piezoelectric body can be obtained.

[0130] In Aspect 6, which is a specific example of Aspect 1, the voltage application circuit further includes a waveform adjustment unit that applies a drive waveform to the piezoelectric element to eject liquid from the nozzle and adjusts the drive waveform in accordance with the degree of deterioration of the piezoelectric element. Because the degree of deterioration of the piezoelectric element acquired by the acquisition unit is accurate, using a drive waveform adjusted based on this degree of deterioration makes it possible to more accurately adjust the displacement of the piezoelectric element to the displacement amount before deterioration.

[0131] In aspect 7, which is a specific example of aspect 6, the drive waveform is a waveform in which an intermediate voltage, an expansion voltage that expands the pressure chamber, a contraction voltage that contracts the pressure chamber, and the intermediate voltage are applied in this order.

[0132] In Aspect 8, which is a specific example of Aspect 7, the waveform adjustment unit adjusts the drive waveform so that the difference between the expansion voltage and the contraction voltage increases as the degree of deterioration of the piezoelectric element increases, thereby enabling the displacement of the piezoelectric element to be more accurately adjusted to the displacement before deterioration.

[0133] In Aspect 9, which is a specific example of Aspect 6, the liquid ejection head further includes a time acquisition unit that acquires information regarding the time period during which the liquid ejection head is used, and the waveform adjustment unit adjusts the drive waveform when the time indicated by the information acquired by the time acquisition unit exceeds a predetermined threshold time. The drive waveform can be adjusted at a timing when it is estimated that the displacement of the piezoelectric element has deteriorated to a considerable extent.

[0134] In Aspect 10, which is a specific example of Aspect 6, the liquid ejection head further includes a count acquisition unit that acquires information about the number of times liquid has been ejected from the liquid ejection head, and the waveform adjustment unit adjusts the drive waveform when the number of times indicated by the information acquired by the count acquisition unit exceeds a predetermined threshold number. The drive waveform can be adjusted at a timing when it is estimated that the displacement of the piezoelectric body has deteriorated to a considerable extent.

[0135] In Aspect 11, which is a specific example of Aspect 6, the device further includes a receiving unit that receives input from a user regarding whether or not the drive waveform needs to be adjusted, and the waveform adjusting unit adjusts the drive waveform when the receiving unit receives input indicating that the drive waveform needs to be adjusted. The drive waveform can be adjusted at a timing desired by the user.

[0136] In Aspect 12, which is a specific example of Aspect 1, an aging processing unit is further provided that performs an aging process to drive the piezoelectric element before printing to reduce the displacement of the piezoelectric element according to the degree of deterioration of the piezoelectric element. The aging process can be performed according to user requests with the liquid ejection head mounted on the liquid ejection device.

[0137] A liquid ejection device according to a preferred aspect 13 includes a liquid ejection head including a nozzle for ejecting liquid, a pressure chamber, and a piezoelectric element that applies pressure to the liquid in the pressure chamber to eject the liquid from the nozzle, a voltage application circuit that applies a voltage to the piezoelectric element, and an acquisition unit that acquires the degree of deterioration of the piezoelectric element based on information regarding the maximum strain or residual strain of the piezoelectric element. The degree of deterioration of the piezoelectric element can be acquired based on the maximum strain or residual strain of the piezoelectric element.

[0138] A preferred embodiment of a fourteenth aspect of the present invention relates to a method for acquiring the deterioration state of a liquid ejection device including a nozzle for ejecting liquid, a pressure chamber, and a piezoelectric element for applying pressure to the liquid in the pressure chamber to eject the liquid from the nozzle. The method includes applying a voltage that is gradually changed from a first voltage to a second voltage to the piezoelectric element, integrating a current generated by the application of the voltage to acquire information relating to the integrated value, and acquiring the degree of deterioration of the piezoelectric element based on the information. The information relating to the integrated value of the current tends to decrease as the displacement of the piezoelectric element deteriorates. Therefore, based on the information relating to the integrated value of the current, it is possible to directly determine the degree of deterioration of the piezoelectric element from its original displacement, thereby more accurately determining the degree of deterioration of the piezoelectric element. [Explanation of symbols]

[0139] H...liquid ejection head, S...medium, 1...liquid ejection device, 2...casing, 3...liquid storage section, 4...control unit, 5...transport mechanism, 5a...transport roller, 6...movement mechanism, 7...holding body, 8...transport belt, 9...operation panel, 9a...display device, 9b...operation device, 10...flow path forming substrate, 12...pressure chamber, 15...communication plate, 16...nozzle communication path, 17...first manifold section, 18...second manifold section, 19...supply communication path, 20...nozzle plate, 21...nozzle, 30...protective substrate, 31...accommodation section, 32...through hole, 40...case member, 41...recess, 42...third manifold section, 43...connection port, 44...inlet port, 45...compliance base Plate, 46...sealing film, 47...fixed substrate, 48...opening, 49...compliance section, 50...vibration plate, 51...elastic film, 52...insulating film, 60...first electrode, 70...piezoelectric layer, 80...second electrode, 91...individual lead electrode, 100...manifold, 110...wiring board, 111...drive signal selection circuit, 211...control processing section, 212...storage section, 213...drive signal generation section, 216...current detection section, 220...print engine, 230...external device, 240...ejection control section, 241...acquisition section, 242...waveform adjustment section, 243...time acquisition section, 244...count acquisition section, 245...aging processing section, 300...piezoelectric actuator, 310...active section

Claims

1. a liquid ejection head including a nozzle for ejecting liquid, a pressure chamber, and a piezoelectric body for applying pressure to the liquid in the pressure chamber in order to eject the liquid from the nozzle; a voltage application circuit that applies a voltage to the piezoelectric body; and an acquisition unit that acquires the degree of deterioration of the piezoelectric body based on information regarding the integral value of the current generated when the voltage applied to the piezoelectric body is gradually changed from a first voltage to a second voltage.

2. one of the first voltage and the second voltage is positive and the other is negative; the first voltage is a voltage substantially equal to a coercive electric field of the piezoelectric body, 2. The liquid ejection device according to claim 1, wherein the second voltage is substantially equal to a voltage at which the piezoelectric body reaches saturated polarization.

3. the voltage application circuit applies a drive waveform to the piezoelectric element to eject liquid from the nozzle; the first voltage is a minimum voltage of the drive waveform, 3. The liquid ejection apparatus according to claim 1, wherein the second voltage is a maximum voltage of the drive waveform.

4. the first voltage is a voltage substantially equal to 0; 2. The liquid ejection device according to claim 1, wherein the second voltage is substantially equal to a voltage at which the piezoelectric body reaches saturated polarization.

5. the first voltage is a voltage substantially equal to a coercive electric field of the piezoelectric body, 2. The liquid ejection device according to claim 1, wherein the second voltage is zero.

6. the voltage application circuit applies a drive waveform to the piezoelectric element to eject liquid from the nozzle; 2. The liquid ejection device according to claim 1, further comprising a waveform adjustment unit that adjusts the drive waveform in accordance with the degree of deterioration of the piezoelectric body.

7. 7. The liquid ejection device according to claim 6, wherein the drive waveform is a waveform in which an intermediate voltage, an expansion voltage for expanding the pressure chamber, a contraction voltage for contracting the pressure chamber, and the intermediate voltage are applied in this order.

8. 8. The liquid ejection device according to claim 7, wherein the waveform adjustment section adjusts the drive waveform so that the difference between the expansion voltage and the contraction voltage increases as the degree of deterioration of the piezoelectric body increases.

9. a time acquisition unit that acquires information about a time period during which the liquid ejection head is used; 7. The liquid ejection device according to claim 6, wherein the waveform adjustment section adjusts the drive waveform when the time indicated by the information acquired by the time acquisition section exceeds a predetermined threshold time.

10. a number acquisition unit that acquires information about the number of times liquid has been ejected from the liquid ejection head; The liquid ejection device according to claim 6 , wherein the waveform adjustment section adjusts the drive waveform when the number of times indicated by the information acquired by the number acquisition section exceeds a predetermined threshold number of times.

11. a receiving unit that receives an input from a user regarding whether or not the driving waveform needs to be adjusted; The liquid ejection device according to claim 6 , wherein the waveform adjustment unit adjusts the drive waveform when the reception unit receives an input indicating that adjustment of the drive waveform is necessary.

12. The liquid ejection device according to claim 1, further comprising an aging processing unit that performs an aging process to reduce the displacement of the piezoelectric element by driving the piezoelectric element before printing, depending on the degree of deterioration of the piezoelectric element.

13. a liquid ejection head including a nozzle for ejecting liquid, a pressure chamber, and a piezoelectric body for applying pressure to the liquid in the pressure chamber in order to eject the liquid from the nozzle; a voltage application circuit that applies a voltage to the piezoelectric body; an acquisition unit that acquires the degree of deterioration of the piezoelectric body based on information about the maximum strain or residual strain of the piezoelectric body.

14. A method for acquiring a deterioration state of a liquid ejection device including a nozzle that ejects liquid, a pressure chamber, and a piezoelectric element that applies pressure to the liquid in the pressure chamber in order to eject the liquid from the nozzle, the method comprising: applying a voltage that is gradually changed from a first voltage to a second voltage to the piezoelectric body; integrating the current generated by applying the voltage to obtain information about the integral value; A method for acquiring the deterioration state of a liquid ejection device, comprising acquiring the degree of deterioration of the piezoelectric body based on the information.

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